Remote C- H Functio naliz ation a nd Photo chromic Properties I nvestigatio n of 3 H -Naphthop yrans vorg elegt von Master of S cience Longy ing Qi von der Fak ultät II - Mathem atik und Naturwisse nschaften der Techn ischen Univer sität Berlin zur Erlang ung des ak adem ischen Grades Dok tor der Naturwissens chaften - Dr. rer . nat. - genehm igte Disserta tion Promotions ausschuss: Vorsitzende r: Prof. Dr. M ichael Gradz ielski Gutachterin : Prof. Dr. Karo la Rück- Braun Gutachter: P rof. Dr. Be rnd Schm idt Tag der wis senschaft lichen Ausspr ache: 04. Dezem ber 2020 Berlin 20 20 Die vorlieg ende Arbei t wurde unter der Le itung v on Frau Prof. D r. Karola Rück- Braun in der Zeit v on Sep. 2016 b is Sep. 2020 im I nstitut für Chem ie der Fak ultät II der Techn ischen Univer sität Berlin angefertig t i Abstract Naphthopy rans, as an important class of or ganic photochromic compounds, have a wide application in ophthalmic lenses and other fields, such as mol ecular elec tronic devices , photochromic thin films, etc. The substituents have a great influence on the photochromic behaviors of naphthop y rans. Hen ce, the research about relationship between subst ituents and photochromic prope rties as well a s the meth ods on introducing diffe rent substituents to naphthopyrans will lea d to a better understanding on the design of naphthop y rans in the industry. Selective C-H functionalization is a significant organic s ynthesis method, but it has not been adopted on naphthopyrans. Especially the distant selective C -H functionalization, it is still a challenge for naphthalenes. Thus, the first part of this thesis is expl oring selective C- H functionalization of naphthopyra ns involving two differe nt methods. The fi rst method is direc ted C-H functionalization. Selec tive meta -C-H (C4-H) and C5 -H functionalization of naphthalene s were achieved with route 1. Selective C 6-H functionalization of naphthopy rans was carried out with route 2. How ever, the se cond method, nondirected C-H functionalization lead to a mix ture of differe nt substituted products. The second part of this thesis is the investi gation on photochromic p roperties o f different substituted 3 H -naphthopy ra ns, which is focused o n the effects of 8 -, 6- and 3-substituents. R oom temperature UV/Vis absorption spectroscopy an d low temperature in -situ NMR measure ments were applied. Kinetic analysis was conducted successfull y i n different solvents during UV irradiation, thermal relaxation and irradiation with visi ble light. The rate con stants of diff erent processes were ca lculated and demonstrated to be impacted greatly by substituents. ii Kurzzusa mmenfassung Naphthopy rane sind eine wichtige Klasse orga nischer photochromer Verbindun ge n mit weitreiche nden Anwendungen in augenoptischen Gläsern und Linsen sowie auf and eren Gebieten, z.B. in molekularen elektronischen Instrumenten, photochromen d ünnen Filmen usw.. Substituenten haben einen großen Einfluss auf da s photochrome Verhalten von Naphthop yra n en. Somit führe n experimentelle Untersuchungen, di e eine Beziehung z wischen S ubstituenten und photochromen Ei ge nschaften he rstellen, und Methoden zur Einführung von v erschiedenen Substituenten an Na phthopyranen, z u einem besseren Verständnis für das Desi gn industriell relevanter Na phthop y rane. Die selektive C -H Funktionalisierung ist eine signifikante organisch-s y nthetische Methode, die bislang auf Naphthop y rane ka um angewe ndet wurde. I nsb esondere die we itreichende selektive C- H Funktionalisierung ist im Fall von Naphthalinen noch eine Hera usforder ung. I m ersten Teil der vorliegenden Promotio nsschrift werden d aher selektive C -H-Funktionalisierungen von Naphthopy ranen über zwei verschiedene Meth oden be schrieben. Die erste Me thode ist eine dirigierende C-H Fun ktionalisierung. Hierbei wurde di e meta -C-H (C4-H) und C5- H Funktionalisierung von Naphthalinen über Route 1 untersucht. Die selektive C6 - H Funktionalisierung von Na phthopyranen wurde über Route 2 ebenfalls untersuc ht und erfol gre ich ausgeführt. Außerdem wurde über die z weite Methode die nicht -dirigierende C- H Funktionalisierung von Naphthalinen erprobt, die allerdings eine Mischung verschiedener Verbindungen erga b. Im zweiten Teil der Promotionsarbeit werden die p hotochromen Eigenschaft en verschiedener 3 H - Naphthopy rane untersu cht und vor gestellt, w obei der Fokus auf den Einfl üssen von 8 -, 6- und 3- Substituenten liegt. UV /Vis-spektroskopische Untersuchungen bei Raumtempera tur und Tieftemperatur in -situ NMR Untersuc hungen wurden durchgeführt. Kinetische Untersuc hungen und Analy sen wurden in verschiede nen L ösun gsmitteln unter UV-Bestrahlung, thermischer Relaxation und un ter Be strahlung mit sichtbarem L icht ausgeführt. Die Geschwindigkeitskonstanten wurden ermitt elt, und es konnte gezeig t werden, dass die Substituenten eine g roße Auswirkung auf die verschiedenen Prozesse zeigen. iii Abbreviations A Absorbance AP Allenyl-naphthol Ar Ar y l APC I Atmospheric pre ssure io nisation i Bu i so -butyl t Bu tert -butyl c Concentration CF Closed form COSY Correlation spectroscopy d Doublet DCE 1,2-Dichloroethane DCM Dichloromethane DEPT Distortionless enhancement by polariz ation transfer DG Directing group DMF Dimethylfor mamide DMS Dimethyl sulfide DMSO Dimethyl sulfoxide EA Ethyl acetate eq. Equivalent ESI Electrospray ionization Et Ethyl h Hour HFIP Hexafluoroisopropanol HMBC Heteronuc lear multiple b ond corre lation HMQC Heteronuc lear multiple-q uantum correlation HRMS High resoluted mass spectrometry LDA Lithium diisopropy lamide m Multiplet m - meta - M mol/L iv Me Methyl min Minute MOMCl Chloromethyl methy l ether Mp Melting point NBS N -bromosuccinimide NFSI N -fluorobenzene sulfonimi de NMR Nuclear magnetic resonance ppm Parts per million PPTS Pyridinium p -toluenesulfonate PSS Photostationary state q Quartet R f Retention factor r.t. Room temperature s Singlet t Triplet t 1/2 half-life (azobenzenes e tc), or the time tak en from absorbance to re duce b y 1/2 of the initial absorbance (naphthop y rans) t 3/4 The time taken fr om abs orbance to reduce b y 3/4 of the initial absorbance t pss The time to arrive at the PSS TC Transoid - cis TCE Tetrac hloroethene THF Tetrahydrofura n TLC Thin layer c hromatograph y TMS Trimethylsily l group TT Transoid - trans UV Ultraviolet V is Visible λ 𝑖𝑠𝑜 The wave len gth at the isosbestic point λ 𝑚𝑎𝑥 The absorption maximum Table of Conte nts Abstract ........................................................................................................................................... i Kurzzusamme nfassu ng ................................................................................................................. ii Abbreviations ............................................................................................................................... iii 1. Introduction ............................................................................................................................... 1 1.1 Photoc hromis m .................................................................................................................... 1 1.1.1 Naphthopyrans .............................................................................................................. 3 1.1.2 Synthesis of Naphthopyrans ................................ ........................................................ 6 1.1.3 Structure and Character isation of 3 H -Naphthopyrans ............................................ 8 1.1.4 Photoc hromic Properties of 3 H -Naph thopyrans Varied with Substitue nts .......... 15 1.1.5 Applications of 3 H -Naphthopyrans ................................................................ .......... 22 1.2 Meta -C-H Functionalization of Benzene ................................................................ ......... 23 1.3 Distant Selective-C-H Functionalization of Naphthalene .............................................. 27 2. Aim and Strategy ................................................................................................ .................... 31 3. Synthesis of Rem ote S elective C -H Functionalization of Naphthopyrans ......................... 33 3.1 Method Ⅰ : Dire cted S elective C-H Function alization .................................................. 33 3.1.1 Route 1 of the Synthesis ................................ ............................................................. 34 3.1.2 Route 2 of the Synthesis ................................ ............................................................. 47 3.2 Method Ⅱ : Nondirecte d Meta -C-H Functionalization ................................ .................. 54 3.3 Discussion ........................................................................................................................... 58 3.3.1 The Selection for C-H Functionalization of Naphthopyran N6 ............................. 58 3.3.2 The Failure for Formation of Naphthopyran 21 in Route 1 of Method Ⅰ ........... 59 4. UV/Vis Spectroscopy .............................................................................................................. 61 4.1 UV/Vis Studies of Two States System: N aphthopyrans N1, N2, N3 and N4 ................ 61 4.1.1 UV Irradiation ................................................................ ............................................ 61 4.1.2 Therm al Back Re action .............................................................................................. 63 4.1.3 Visible Light Irradiation ............................................................................................ 67 4.1.4 Solvent Effect on the Photoc hromic Properties ....................................................... 68 4.2 UV/Vis Studies of Three States System: Naphthopyrans N5 and N6 ........................... 72 4.2.1 UV Irradiation ................................................................ ............................................ 72 4.2.2 Therm al Back Re action .............................................................................................. 73 4.2.3 Visible Light Irradiation ............................................................................................ 76 4.3 UV/Vis Studies of C-H Functionalization Product N7 ................................................... 78 4.3.1 UV Irradiation ................................................................ ............................................ 78 4.3.2 Therm al Back Re action .............................................................................................. 79 4.3.3 Visible Light Irradiation ............................................................................................ 80 4.4 UV/Vis Studies of Naphthopyrans N8, N9 and N10 ....................................................... 82 4.5 Discussion ........................................................................................................................... 84 4.5.1 The Effect of 8-Substituent on the Photochrom ic Properties of Naphthop yrans . 84 4.5.2 Comparison betwee n Two S tates System and Three States System ...................... 85 4.5.3 The Effect of 6-Substituent on Photochromic Properties of Naphthopyran ......... 86 5. In -situ NMR Analysis ............................................................................................................. 89 5.1 In -situ 1 H NMR Analysis of Two States System : Naphthopyran N1, N3 and N4 ....... 89 5.1.1 Structural Identification of Different Isome rs of N1 ............................................... 89 5.1.2 Structural Identification of Different Isome rs of N3 ............................................... 92 5.1.3 Structural Identification of Different Isome rs of N4 ............................................... 94 5.1.4 Kinetic Analysis of N1, N3 and N4 during Different P ro cesses .............................. 96 5.2 In -situ 19 F NM R anal ysis of Three State s System: Naphthopyran N5 and N6 .......... 100 5.3 Investigation of Visible Light Wavelength Influence on P SS Vis of N7 by In -situ 19 F NMR analysis ......................................................................................................................... 105 5.4 In -situ 1 H NMR analysis of Naphthopyrans N8, N9 and N10 ..................................... 109 5.5 Discussion ......................................................................................................................... 111 5.5.1 The Different Pe rf ormance between Two States System and Three States System during the Low Temperature in - si tu NMR Me asurements ........................................... 111 5.5.2 The Effect of 6-Substituent on Photochromic Properties of Naphthopyran during the Visible Light Irradiation in Low Temper ature in -situ NMR Measurem ents ........ 113 6. Summar y and Outlook ................................................................................................ ......... 115 6.1 The Synthesis of Naphthopyrans by Selective C-H Functionalization ....................... 115 6.2 The Photoc hromic Properties of 3 H -Naphthopyrans .................................................. 118 6.3 Outlook ............................................................................................................................. 124 7. Experimental Section ............................................................................................................ 125 7.1 Synthesis ........................................................................................................................... 125 7.1.1 General Information ................................................................................................. 125 7.1.2 Pr ocedure .................................................................................................................. 126 7.2 UV/Vis Absorption Spectroscopy .................................................................................. 150 7.2.1 General Information ................................................................................................. 150 7.2.2 Time-Resolved Experiments and Exponential Fitt ing .......................................... 154 7.3 In -situ NMR Measurem ent ............................................................................................. 161 8. Appendix ................................................................................................................................ 163 8.1 1 H and 13 C NMR Spectr a ................................................................................................ 163 8.2 2D NMR Spectra ............................................................................................................. 189 8.3 UV Absorption Spectra ................................................................................................... 195 8.4 In -situ NMR Spectra ....................................................................................................... 204 9. Reference ............................................................................................................................... 213 1 Introduc tion 1 1 . Introduction 1.1 Photochrom i sm “ Photochromism ” was us ed firstly in 1950, when Hirshberg propos ed the t erm “Photochromism” [from the Greek words: p hos (light) and chroma (color)] to depict the phenomenon that compounds changed c olor under light irra diation and returned to the initial color in the dark. [ 1] However, at present, “ Photochromism ” is defined as “a reversible transformation of a chemical species induced in one or both directions by absorption of electromag netic radiation between two forms, which have different absorption spectra ” (Figure 1.1). [2] F or most photochromic c ompounds, λ max (A ) < λ max (B) and the phenomenon is regarded as positive photochromism. Otherwise, it is negative (reverse) photochromism. Figure 1.1 Gene r al pho tochrom ic behavior according to the defini t ion of posi tive photoc hromism. Copyrig ht © 2001, I nt ernational Unio n of Pure and Ap plied Chemistry . Light is an excellent sti mulus due to its se veral advantages: it is non-tox ic, an unli mited energy source a nd can be delive red fast with high spatial and tempora l control. Since the first example of Photochromism was reported in 1867, [3] all kinds of photochr omic compounds have been published. Based on th e ba ck reaction, they can be divided into two t y pes. I f the compounds a re thermally reversible, they are T -t ype photochr omic compounds (or p hotoswitches). If the photochromic molecules are thermall y ir reversible but photochemically reversible, the y ar e P-t y p e photochromic compounds . Various prevalent pho tochromic compounds o f these two t y pes are demonstrated in Figure 1.2. 1.1 Photoc h rom ism 2 Figure 1.2 Di fferent ph otochrom ic compounds o f T-ty pe and P-ty pe. 1 Introduc tion 3 Six different chemical processes are found during photochromism, including peric y clic reaction, cis - trans ( E / Z ) isomerizations, intramolecular hydrogen transfer, intramolecular group transfers, dissociation processes and electron trans fer (ox ido-reduction), [2] wherein peric y c lic reactions and cis - trans ( E / Z ) isomerizations are involve d in the prevalent photoch romic compounds pre sented in Fig u re 1.2 upon irradiation with light. For T -type photochromic compounds, spirop y r ans and spirooxazines undergo 6π six atom electrocy clizati on ring opening reaction s; hemithioindigo and azobenzenes go through cis - trans ( E / Z ) isomerizations; naphthop y rans undergo 6π six atom electrocy clization ring opening reaction s followed by cis - trans ( E / Z ) isomerizations; donor- acceptor Stenhouse adducts (DASA) go through 4π electroc y cliz ation ring closure r eaction s, which are also a kind of negative photoswitches. For P-t ype photochromi c compounds, closed forms of dithien y l ethenes are obtained through 6π six atom electrocyclization ring closure reac tions; Fulgides and related compounds go through cis - trans ( E / Z ) isomeriz ations followed by ring c losure reaction. Photochromic compounds have wid e applications, such as opti cal data storage, fluore scence microscopy ima ging, ophthalmic lenses, smart w indows and biomaterial s b y incorporation into surfaces, peptides, pol ymers, enz ymes, prot eins and amino acids, because of the variation in photophysical and photochemica l properties between isomers of photochro mic compounds. [4 – 10] 1.1.1 Naphthopyrans Naphthopy rans, as a kind of chromene derivatives, w ere first ly reported by Becker and Michl in 1966. [11] C hromenes are a kind of T-t ype photochromic compounds. As reported in the literature , photochromism of chro menes was observed and it was also found th at the lifetime of colored isomers of chromenes was enhanced b y th e annulation of an additional benzene ring. In addition, it was r eported that the stabilit y of colored iso mers was also increased by the conju ga tion substituents at the sp 3 -C-atom adjacent to the ox yge n atom. Afterwards, the naphthop yra ns with two ary l substituents att ached to sp 3 -C-atom de veloped into currently the popular s y stem of photochromic naphthopyrans. There are thre e t y pes o f naphthop y rans, wh erein 2 H -naphtho[1,2-b]p y rans and 3 H -naphtho[2,1- b]p y rans are the main r esearch objects of phot ochromic behavior, r esult ing from few use ful photochromic response s demonstrated for 2 H -naphtho[ 2,3-b]p y ran. [12] 1.1 Photoc h rom ism 4 Figure 1.3 Di fferent types of nap hthopy rans. After UV irradiation, the colorless naphthop y r ans can change into colored open forms, resulting from the more bathochromi c absorption spectrum of these colored open fo rms (Figure 1.4). [1 3,14] Base d on the me chanism investiga tion using femo- to -picosecond transient absorption spectroscopy b y Guglielmetti and co- workers [15,16] , UV li ght excites the ground state (A) o f the closed form of 3 H -naphthopyran into one of its s ing let excited states ( n A*). Then it decay s to the first ex cited state ( 1 A*). The molecular conversion into a primar y isom er (B 1 ) through a conical intersection and the c leavage of the C-O bond is observed in 450 fs. B 1 is s hort-lived a nd conve rts into the one of the trans-isomers (B 2 ) in 2 ps. At last, another trans-isomer (B 3 ) is formed through isomerization in 21 ps (Figure 1.5). Figure 1.4 Col or change (u p) and abso rption spe ctr al chang es of 2,2- diphenyl- 3 H -naphtho[2,1- b]pyran in acetonitrile a f ter U V irradiation (dow n). Copyright © 20 13, The Roy al Society of Chem ist ry. 1 Introduc tion 5 Figure 1.5 The energ y diagram of the ring opening m echanism [16] . Copy right © 2016, Elsevier B. V. Figure 1.6 Gene r ic photoc hrom ic and therm al relaxation pro cess es of naphthopy rans . Further mechanisms ha ve also been studied. [16] Upon UV irradiation, the cl eavage of the C(sp 3 )- O bond appea rs, resulting in the short-lived CC fo rm and was followed b y the formation of the colored the rmally unstable TC ( trans oid - cis ) form through rotation of the single C 2 -C 3 bond (from cisoid to transoid ). Mea nwhile, the TC form c an revert to the long-lived TT ( transoid - trans ) form through rotation of the C 1 =C 2 double bond under UV irradiation. I f the ar yl substituents attached 1.1 Photoc h rom ism 6 to the C(sp 3 )- atom are different, there will exist TTC, TTT, TCC and TCT forms. I n addition, the alleny l-naphthol (AP) iso mer was d etected b y Delbaere and co -workers, [17,18] and the AP form can be reverted fr om the TC form under irra diation with UV or visible light. On the other ha nd, in t he dark, the AP form can b e revert ed b ack to the T C form easil y, and the T C form can be r evert ed back to the CF form ( closed from) ra pidl y . B y contrast, the the rmal trans formation from TT to TC is much slower. B ut faste r conversion is observed under visible light irradiation (Figure 1.6). 1.1.2 Synthesis of Naph thopyrans The earliest publication about the synthesis of naphthop y r ans with two ar y l subst ituents was reported b y Livingstone and co-workers in 1960, in which aryl Grignard reagents were emplo y ed and 3 H -naphthop y r ans were obtained in moderate y ield. But a by product was also detected at the same time (Figure 1.7 ). [19 – 21] Figure 1.7 The synthesis of naphthopy r ans from naphthopyranones. In 1983, Talley reported a s y nthetic method for di meth y l substituted 3 H - naphthop yrans from α,β - unsaturated ald eh y des and ketones in the presence of n -B uLi. [22] Afterwards, this method was developed b y Heller to synthesize diary l substituted 2 H -naphthopyra ns with diffe rent substituents (R 1 ) at 1-position. But the method is li mited b y th e nature of the α,β -unsatura ted aldeh yde s (Figure 1.8 ). [23] Simi lar methods were also used for the s ynthesis of naphthop y rans with a benzothiophene ring in the presence of n -BuLi. [24 – 26] Figure 1.8 The synthesis of naphthopy r ans from α,β -unsaturated aldehydes. 1 Introduc tion 7 The most successful me thod is based on Claisen rearrange ment of naphth yl propargy l ethers . The first publication about s ynthesis of naphthop y rans involving thi s method was reported b y Iwai and Ide in 1962. [ 27,28] Naphthopy r ans were prepared from naphthol and propargy l bromide in two steps (Figure 1.9 ). Figure 1.9 The two step s sy nthesis from propar gy l brom ide and naphthol. In 1991, s ynthesizing diar y l naphthop y r ans in a single step was achieved from n aphthol and propargyl alcohol catal yzed by p -toluenesulfonic acid (PTSA) (Figure 1.10). [29] I n this method, naphthyl proparg y l ethers were formed in -situ from naphthol and propargy l alcohol under acid catalysis, then naphthopyrans were generated through Claisen rearrange me nt. Figure 1.10 The one pot-m ulti step sy nthesis from propargy l alcohol and naphth ol. This method was adopted and developed b y many other groups. So lid -state synthesis of naphthopyrans w as achieved. [3 0] The acid aluminium oxide and pyridinium p-toluenesulfonate (PPTS) as the cataly st can also work wel l. [31,32] However, the y i elds were alway s low or moderate due to the formation o f by-products ( Figure 1.1 1). Wherein b y p roduct A was generated through Mey er-Schuster rea rrangement of the proparg y l a lcohol and by product B was generated through [1,7] -H-shift. [ 31,33] Suprisingl y , the addition of (MeO) 3 CH as a d eh y dr ating agent improved the reac tion to an excellent yield under the PPTS catalysis and the scope of this method is very wid e (Figure 1.12 ). [34] 1.1 Photoc h rom ism 8 Figure 1.11 Gen er ation o f by- product s throug h aci d c at alyzed sy nt hesis of naph thopy rans. Figure 1.12 The synthesis of nap hthopy rans with a ddition of (MeO ) 3 CH . 1.1.3 Structure and Characterisation of 3 H -Naphthopyrans 1.1.3.1 UV/V is Spe ctroscopy There e xist totally different UV a bsorption spectra for naphthop y r ans befor e and after UV irradiation, hence UV/Vis spectroscopy is the main method to investigate the photochromic properties of n aphthop y r ans. The UV absorption s pectra o f closed a nd open forms can be obtaine d and maxim a waveleng t hs of absorption ( λ max ) can be observed. Ther efore , w e can get the colorability, half-life (t 1/2 ) of different substituted naphthop y r ans and then proceed to the kinetic investigation. 1 Introduc tion 9 Colorability Colorability is the abilit y to produce coloration for a colorless or sli ghtly colored photochromic material. [2] A 0 ( λ ) = k Φ col ε B C A A 0 (λ) is the ini tial absorbanc e at a given irradiation wavelength , Φ col is the coloration quantum y i eld, ε B is the mol ar absorption coefficient of th e colored fo rm, C A is the concentration of the colorless form and k is the proportionality constant. [35] Half-life Half-life (t 1/2 ) is defined as the time taken from absorbance to reduce b y ½ of the initial absorbance during thermal re laxation. Kinetic investiga tion When the λ max of open forms are detected after UV irradiation, time resolved absorbance curves can be recorded at λ max . T hen the speed of rin g ope ning and ring closure reac tion can be calculated. For thermal fading rate, we are considering two processes: a. TC → CF and b. TT → TC , which ex ist in the procedure at the same ti me, thermal back rate constants k 1 and k 2 can be calculated b y fittin g the absorbance c urve to a biex ponential decay ( Equ ation 1 ). [36 – 42] A (t) = A 1 exp (- k 1 t) + A 2 exp (- k 2 t) + A th (1) Where A (t) is the absorbance at the λ max , A 1 and A 2 are contributions to the initial absorbance A 0 , k 1 and k 2 a re ra te constants of fast and slow components, respectively. A th is the residual absorbance when time approaches in finity. I n addition, Abe group thinks the ratios of TT f or ms in the photostationary state (PSS) can be calculated through A 2 / (A 1 +A 2 ). [43,44] However, if k 2 is far slower than k 1 ( k 2 << k 1 ), there will be residual c olor left after thermal relaxation until prolonging enough thermal time due to the long -lived TT form. Correspondingly, the thermal fading curve is a monoexponential decay in the beginning stage of thermal back period , and k 1 can be obtained through fitting absorban ce curves to a first order exponential decay ( Equation 2 ). [45,46] 1.1 Photoc h rom ism 10 A (t) = A 1 exp (- k t) + A th (2) Where A (t) is the absorbance at the λ max , A 1 is the contributions to the initial absorbance A 0 , k is rate constants of fast components, and A th is the residual absorba nce at the termination of testing time . Furthermore, to explore the photochromic properties of dif ferent naphthop y rans, the measurements should be carried out in the same solvent and at th e same temperature, considering temperature and solvent will influence the photochromic behaviors a lot . [12,47] The photochromic properties var y with substi tuents through UV/Vis spectroscopy and will be disscussed in Chapter 1.1.4. 1.1.3.2 In -Situ NMR Spectroscopy Because at least two new isomers are for med in the sy st em of naphthopyrans a fter UV irradiation, spectral overlapping between different isomers makes it difficult to explore the photochromic properties of ever y isomer with UV/Vis spectroscop y . Thus, in -situ NMR s pectroscopy is a more powerful method to investiga te the photochromic behavior of naphthop y r ans. [48] Meanwhile, low temperature in -situ NMR measure ments provide us a viable method for the detection of naphthopyrans whic h ha ve a very fast therm al fading rate. The chemcal shifts of d ifferent substituted 3 H -naphthopyrans are depicted in Table 1.1. It is revea led that the identifiable peaks of open forms are 1 -position, 2-position and 5 -position of protons. In general, the H-2 of TC forms appears at the lowest field around 9 ppm because of the deshielding cau sed b y C= O, and H-1 of T T form is at the lowest field in it s spectrum. The H-2 and H-1 are used as fingerprint for the presence of TC and TT form, respectively. [48] The H-5 of both open isomers moves to a higher field ar ound 6.4 ppm from a low field in the closed form. Moreover, the allen yl-naphthol (AP) isomer of 3 H -naphthop y rans was disc overed b y Delbaere and co -workers via NMR spectroscop y at low temperature. [1 7,18] I ts identifiable peak is the – O H, which ge nerall y a ppears at approx imately 10 ppm. 1 Introduc tion 11 Table 1.1 Sel ected chem ical shifts of repor ted 3 H - naphthopyrans. Naphthopyra n Chem ical shift/ ppm CF TC TT AP NP1 a H1 = 7.47 H2 = 6.56 H5 = 7.31 H6 = 7.81 H7 = 7.83 H10 = 8.08 H1 = 7.75 H2 = 8.43 H5 = 6.41 H6 = 7.59 H7 = 7.49 H10 = 7.59 - H1 = 7.84 H5 = 7.44 H6 = 7.97 H7 = 8.02 H10 = 8.52 OH = 10.06 b NP 2 a H1 = 7.48 H2 = 6.46 H5 = 7.28 H6 = 7.81 F = - 114.98 H1 = 7.68 H2 = 8.40 H5 = 6.41 H6 = 7.64 F = - 111.96, - 112.49 H1 = 7.99 H2 = 7.50 H5 = 6.32 H6 = 7.64 F = - 112.10, - 112.12 H1 = 7.68 H5 = 7.30 H6 = 7.81 OH = 9.83 F = - 115.2 c NP 3 d - H2 - CT C = 8.66 F-CTC = - 112.47 H2 - T TC = 8.24 F-TTC = - 112.66 H5 - CT T = 6.29 F-CTT = - 112.62 H5 - TT T = 6.31 F-TTT = - 112.55 H1 = 7.70 H5 = 7.30 H6 = 7.84 OH = 9.90 F = - 112.2 c NP 4 e F = - 113.7 F = - 110.1 - 110.6 F = - 109.5 - 110.4 F = - 113.6 NP 5 f - H1 = 7.74 H2 = 9.31 H5 = 6.50 H6 = 6.60 H1 = 8.16 H5 = 6.39 - NP 6 f - H1 = 7.61 H2 = 9.22 H5 = 6.41 H6 = 6.47 H1 = 8.08 H5 = 6.26 - 1.1 Photoc h rom ism 12 NP 7 g - H1 - CT C = 8.09 H2 - CT C = 9.09 H1 - T TC = 7.65 H2 - T TC = 9.52 H5 - T TC = 6.52 H1 - CT T = 8.54 H2 - CT T = 7.04 H1 - T TT = 7.97 H2 - T TT = 7.47 H5 - T TT = 6.32 - NP 8 h H2 = 5.78 F = - 113.1 - 113.2 H2 = 8.88 H5 = 6.49 F = - 110.0 - 110.6 H1 = 7.31 H5 = 6.20 F = - 109.6 - 110.2 - NP 9 i H1 = 7.78 H2 = 6.00 H5 = 7.29 H6 = 7.64 H1 = 9.39 H2 = 9.26 H1 = 8.79 H2 = 7.17 - NP 10 j H1 = 6.07 H2 = 6.72 H5 = 8.46 H1 = 7.89 H2 = 9.41 H5 = 7.68 H1 = 8.24 - [a] Data from Ref. [36] , 1×10 -2 M in CD 3 CN, 228 K. [b] Data from Ref . [17] , 1×10 -2 M in acetone- d 6 , 213 K . [c] Data from Ref. [18] , 1×10 -2 M in acetone- d 6 , 213 K . [d] Data from Ref. [49] , 1×10 -2 M in CD 3 CN, 228 K. [e] Da ta from Ref. [50 ] , 1×10 -2 M in tol uene- d 8 , 243 K. [f] Data fro m Ref. [51] , 6×10 -3 M- 1×10 -2 M in toluene- d 8 , 228 K . [g] Data from Ref. [52] , 6×10 -3 M- 1×10 -2 M in t oluen e- d 8 , 213 K. [ h] Data from Ref. [53] , 5×10 -3 M in toluene- d 8 , 228 K. [i] Data from Ref. [54] , 5×10 -3 M in toluene- d 8 , 293 K. [j] Data from Ref . [55] , 1×10 -2 M in to luene- d 8 , 193-223 K. 1 Introduc tion 13 1.1.3.3 Infrared Spectroscopy IR spectroscop y is also a useful method to investi ga te the photochromic prope rties of naphthopyrans. The I R spectra changes of naphth opyran N1 are pr esented in Fig ur e 1.13. After UV irradiation, a new peak appeared at 1633 cm -1 , assi gned to the ketone ν( C-(C=O)-C) , confirming the formation of open forms. At the sa me ti me, both of two ba nds, ν( Ar y l- O) a nd ν( O- Alkyl), decreased in inte nsity at 1247 and 1085 cm -1 , respectively . [ 56] Therefore, the photochromic behavior of naphthopy rans can be explored. 1700 1600 1500 1400 1300 1200 1100 n as (-O-Alkyl-Ether) n as (Aryl-O-Ether) n (C-N) n as (R-CO-O-CH 3 ) n as (-C-CO-O) n (C-N) n (C=C) n (C=C) n (C=O) Ketone Transmission [arb. units] Wa venumbers (cm -1 ) Initial state PSS (after 250 s irradiation with 3 65 nm) Thermal relaxation at RT a fter 650 s n (C=O) Ester d as (-CO-O-CH 3 ) Figure 1.13 The I R spectra changes o f naphthopy ran N1 (3.45 × 10 -2 M in to l uene at 293 K ). [56] 1.1.3.4 X-Ray Crystallography The X-ra y cr ystal structure of several 3 H -naphtho pyrans have be en reported. [ 57 – 59] From the data in Table 1.2, it is revealed that all the C 3 -O bonds (1.440-1.462 Å) ar e lon ger than a ty pical C - O bond in a six-membered heter oc y c le (1.41-1.43 Å). [60] The C 3 -O bond length is affected by th e substituents in the ary l r ings. Moreover, the first X-ra y crystal structure of open form was also reported ( Figure 1.1 4). The bond lengths of both C 1 -C 13D and C 2 -C 3 are 1.36 Å. And C 1 -C 2 bond length is 1.43 Å, which is consistent with a quinoidal structure of an open isomer. [54] 1.1 Photoc h rom ism 14 Table 1.2 Sel ected geom etric parameters. Figure 1.14 The structu re of CTC form of naphthopy r an NP9 . 1.1.3.5 Mass Spectroscopy During t he fr agmentation of 3,3 -diaryl 3 H -naphthop y r ans the homol y ti c dissociation of either on e of the aryl substituents was obser ved (Figure 1.15 ). [61] Figure 1.15 The fragm entati on of 3 H - napht hopyra ns. Naphthopyra n Ar 1 Ar 2 C 3 - O (Å) C 4 - O (Å) C- Ar 1 (Å) C- Ar 2 (Å) Ar 1 -C- Ar 2 (º) NP1 [57] Ph Ph 1.458 1.372 1.530 1.527 110.5 NP 11 [58] 2,6- diFC 6 H 3 Ph 1.440 1.369 1.539 1.544 108.1 NP 12 [58] 2- FC 6 H 4 4- MeOC 6 H 4 1.464 1.380 1.525 1.527 113.1 NP 13 [59] 2- MeOC 6 H 4 2- MeOC 6 H 4 1.462 1.373 - - 93.3 1 Introduc tion 15 1.1.4 Photoc hromic Properties of 3 H -Naph thopyrans Varied with Substituents Different substituents will have a di fferent influe nce on the photochromi c performance of 3 H - naphthopyrans, which depends on the geometr ic size, electron egativity, electropositivity of substituents and the substituted positions. The phe nomena can be explained by the st eric, electron inductive and elec tron resonance effects induced b y the substituents. 1.1.4.1 2-Substituents 2-substituted 3 H -naphthopyrans were fir stl y reported by the Rück-Braun group in 2009. [62] I n that article, the half-life o f a 2-substit uted benzop y ran was reduced to 12 µs. A fterwards, the Ab e group measured the photochromic behavior of 2 - Br -substituted 3 H -naphthopy r ans NP15 . [ 63] It was found that the half-life of N P15 was reduced to 2.5 µs from 34 min of NP14 (the naphthop y r an without 2-substituent) (T able 1.3). The sha rp de crease of half-life is due to the larg e steric repulsion of the 2-substituent which destabilizes the open forms. Table 1.3 Photo chrom ic properties of 2-substituted 3 H -naphthopy rans. a 1.1.4.2 3-Substituents The choice o f substituents at 3 -position pheny l rin gs can have a great influence on the photochromic performance of 3 H -n aphthop y rans and attra ct more and more attentions in the last Naphthopyra n R 1 λ m a x t 1/2 NP14 H 465 34 m in NP15 Br 415 2.5 µs [a] Data from Ref. [63] , 8.5×10 - 5 M in toluene, 298 K . 1.1 Photoc h rom ism 16 two decades. He ron and co -workers revealed that the electron-donating groups at para -position cause a b athochromic shi ft in the UV absorption spectra and promote the thermal relaxation rate. In contrast, electron-withdrawing groups at para -position bring a h y p sochromic shift and retard the thermal bleaching speed (Table 1.4). [58 ,64 ] Table 1.4 Photo chrom ic properties of 3 H - naphthopyrans af fected by substituents at 3- phenyl ri ngs. a For the effect of ortho - a nd meta -substituents, the size of the subst ituents is more important. As presented in Table 1.5, b oth elec tron withdrawing groups and electron-donating groups at ortho - position slow down the thermal back speed and t he half -life increases as the size of subst ituents increases ( NP19 - N P23 ). However, the λ max is influenced b y ortho -substituents barely. [65] B y contrast, meta -substituents have a major e ffect on the λ max . The meta -electron withdrawing g roup s cause a h ypsochromic sh ift in the absorption spectra and reduce λ max as the size of substituents increases ( NP25 - N P27 ) , because of decreasin g c onjugation between the p y rrolidine moiets and the whole structure. For the meta -electron donating g roups, it depends on the comparison between ge ometric siz e and electron donating power , i f geometric siz e contributes more, a h y pso chromi c Naphthopyra n R 1 R 2 λ m a x (nm) NP1 H H 430 NP16 H p - MeO 458 NP17 p -NMe 2 p - MeO 512 NP 18 H p - F 428 NP 2 p - F p - F 419 [a] Data from Re f. [58,64] in toluene, 293 K. 1 Introduc tion 17 shift is observed ( NP28 ); if electron donating power contributes more, it has to be a ba thochromic shift ( NP 29 ). But all the meta -substituents have a negligible effect on the thermal bac k rate. [ 66] Table 1.5 The e f fect of o rtho - and meta -substituen ts in 3-pheny l rings on photoc hromic proper ties of 3 H - naphthopy rans. a Except for pheny l rings, 3 H -naphthop y rans with other substit uents at 3-position have also been reported. Delbaere and co -workers investigated 3 -thieny l-naphthop yra ns (Figure 1.16). [5 2] The y Naphthopyra n R 1 R 2 λ m a x (nm) t 1/2 (s) NP 19 H H 538 5 NP20 F H 554 40 NP21 Cl H 554 741 NP22 Br H 554 1024 NP23 I H 553 1167 NP24 OMe H 555 351 NP25 H F 529 4 NP26 H Cl 513 4 NP27 H Br 493 4 NP 28 H Me 517 3 NP 29 H OMe 557 5 [a] Data from Ref. [65,66] , 1×10 -5 M in toluene, 293 K. 1.1 Photoc h rom ism 18 found that the ring opening rate decreases with an increasing number of thiophene rings and the concentration of open forms also reduces when the number of thiophene rings increase. Figure 1.16 The structu res of 3-thienyl- naphthopyrans. In addition, CH - π bonds were adopted to the s y stem. [54] When an eth y n yl group was added to the 3-carbon instead o f a p heny l rin g, the CH - π bond was observed between the phen yl ring of carba zole group and proton H2’’ in the C TC form, and between the ph en y l ring of the carbazole group and proton H2’ in t he CTT form, thereb y stabiliz ing the open forms (Figure 1.17). Therefore, the ring opening reaction was ac hieved easil y without UV light. Figure 1.17 The photoch rom is m of 3 H - naphthopyrans with CH- π bonds. [54] Copyright © 2012, Am erican Chem ical Society. 1.1.4.3 5-Substituents In ge neral, the 5-substituents have li ttle effect on the λ max of absorption spectra of 3 H - naphthopyrans. [67] But the therm al bleaching rate is decreased b y 5- amino-substituents ( N P32 - NP35 ). [68] Furthe rmore, when the π -conjugation group was introduced, the λ max was induced a s large bathochromic shift and the th ermal bl eaching rate was also accelerated [3 8] ( NP 38 ) (Table 1.6). 1 Introduc tion 19 Table 1.6 The e f fect of 5- subs tituent s on photochr om ic properties of 3 H - naphthopyrans. a Naphthopyra n R 1 λ m a x (nm) k (s -1 ) NP 32 NH 2 439 0.007 NP 33 455 0.017 NP 34 438 0.015 NP 35 425 0.021 NP 36 b MeO 435 - [a] Data from Ref. [68] , 5×1 0 -5 M in tol uene, 293 K. [b ] Data from Ref. [67] , in alipha tic acry lic matrix. Naphthopyra n R 2 λ m a x (nm) t 1/2 (min) NP 37 c H 580 6 NP 38 c CONHC 6 H 5 640 < 1 [c ] Data from Ref. [38] 1.1 Photoc h rom ism 20 1.1.4.4 6-Substituents The 6-substituents have a large influence on the photochromic properties, especially the thermal relaxation rate. As it is demonstrated in Table 1.7, 6 -elec tron don ating sub stituents bring about a hypsoc hromic shift and retard the thermal bleaching sp eed [64,69] ( NP 39 - NP 41 ). However, the effects of 6-e lectron withdrawin g substituents are unknown. Table 1.7 The e f fect of 6- subs tituent s on photochr om ic properties o f 3 H -naphthopy rans . a 1.1.4.5 8-Substituents As shown in Table 1.8, t he 8-substituents can cause a bathochromic shift in the absorption spectra of 3 H -naphthop y rans, in cluding a π -conjugation group, thiophene [45] ( NP42 - NP 43 ), and electron donating substit uents, methoxy l group [6 9] ( NP46 ). Moreover, the thermal bleaching rate is also accera ted b y 8 - π -conjugation substituents and it increa ses with the growth of the thi ophene ring chain [51] ( NP42 - NP 45 ). Naphthopyra n R λ m a x (nm) IOD F 10 % NP13 H 475 45 NP39 OMe 456 10 NP40 Piperidino 452 11 NP41 Morpholino 452 13 [a] Data f rom Ref. [64,69] , i n spectralite. IO DF 10 % : the percentag e loss in initial optical density 10 s after remov i ng the UV source (d es cribed in the litera ture [69] ). 1 Introduc tion 21 Table 1.8 The e f fect of 8- subs tituent s on photochr om ic properties o f 3 H -naphthopy rans . a 1.1.4.6 10-Substituents The 10-substituents play a major role in the stability of open forms. Thus, the thermal bleaching rate will be impacted b y different subst ituents. As presented in Table 1.9, half-life of N P47 is sharply reduced, compared with the reference n aphthop y ran NP1 , becaus e of the destabiliz ing effect on the TC form by the large stericall y demanding bromine substituent. However, the thermal bleaching r ate is retarded by a 10-methox yl gro up due to the C-H ┄ O hydrogen bond, which Naphthopyra n R 1 R 2 λ m a x (nm) k TC→CF (s -1 ) k TT→TC (s -1 ) NP1 H H 430 b 1.59 × 10 -4 - NP42 Th H 478 b 1.96 × 10 -4 5.19 × 10 -6 NP43 Th 2 H 500 b 2.13 × 10 -4 9.90 × 10 -6 NP 6 H - 5.30 × 10 -4 9.76 × 10 -6 NP44 H - 3.69 × 10 -4 - NP45 H - 4.73 × 10 -4 - NP13 c H OMe 475 - - NP46 c OMe OMe 502 - - [a] D ata f rom Ref. [51] , 6×10 -3 - 1× 10 -2 M in toluene- d 8 , 243 K . [b] D ata from Ref. [45] , 1×10 -5 M in toluen e, 280 K. [c] D at a from Ref. [69] , in polyurethane. Th= Th 2 = 1.1 Photoc h rom ism 22 stabilizes the TC from. Coresponding l y , the concentration of TT form is reduced, result ing from the promoted speed of the TT→TC process. [43] Table 1.9 The e f fect of 10 -substituents on photochrom ic properties of 3 H - napht hopy r ans. a 1.1.5 Applications of 3 H -Naphthopyrans Naphthopy rans are a kind of important org anic photochromic materials for ophthalmic lenses, due to their efficient colorabilit y , fa st reversibility, good fa tigue r esistance and broad color range from purple to red. [70,71] Besides, 3 H -n aphthopy rans can be a pplied as photochromic switches [ 72] , molecular electronic devices [73] , photoswitcha ble mol ecular receptor s [74] , photoresponsive polymer s [7 5] , photochromic thin films [41,76] , photoresponsive gels [7 7,78] , liquid cry stalline materials [79] and as molec ular logic gates [80] . Naphthopyra n R λ m a x (nm) t 1/2 (s) TT form/% b NP1 H 425 6.9 16 NP47 Br 419 0.36 17 NP48 OMe 450 9.5 3 [a] Data from Ref. [43] , 5.5×10 -5 M in toluene, 298 K. [b ] data calculated from A 2 / (A 1 +A 2 ) of equation 1 ( for detail, se e Chapte r 1.1.3.1). 1 Introduc tion 23 1.2 Meta -C- H F unctiona l ization of Be nzene Transition meta l-catalyzed selective C – H function alization is a versa ti le a nd powerful tool for the synthesis of complex organic compounds . [81] Wherein para - and ortho -C-H functionalization can be achieved with c lassical Friedel-Crafts reaction easily in the presence of a donor group . Chelation-assisted ortho - C- H activation has also b een developed ver y well during the past decades. Although an ele ctron withdrawing group can direct th e r eaction for ward to the m eta -C-H functionalization product as the main product, usu ally a product mix ture is observed. Consequentl y, selective meta -C-H funct ionalization remains a si gnificant challen ge. [82,83] In the past few y ears, more and more attention has been attracted to this field and a few ex cellent designs have been published. Base d on the m e ch anism, there are about six different t y pes. Figure 1.18 Fun ctionalization of arenes. Directed meta -C-H functionalization with nitrile-containing templates In 2012, Yu and co-workers described a proposa l in which a series of newl y desi gned templates containing a nit rile group was used as directing group to achieve meta -C - H functionalization of arene s. [84] In later mechanism studies, a heterodimeric complex was regarded as the useful catal y st and concerted metalation−deprotonation (CMD) was the proposed procedure [85] (Figure 1.19). La ter, man y othe r nitrile-containing templates for meta -C-H functionalization of arene s have also been designe d. [86 – 107] 1.2 Meta -C-H Fu n ctional ization of Benz ene 24 Figure 1.19 Pd - cat aly zed meta - C- H functionalization using a nitrile e nd-on tem p late. Copper-catalyzed meta -C-H arylation of arenes The second method was discovered b y Phipps an d Gaunt. [8 3] The y reported a Cu -catal y z ed m eta - C – H arylation of arenes with Ar 2 I O Tf under the cataly sis o f C u(OTf) 2 , and the amido group was used as a directin g group. The proposed mechanism is through a dearomati zing “ox y - cupra ti on” process (Figure 1.20). Figure 1.20 Cu - ca talyz ed meta - C- H functionalization. Traceless directing group In 2014, the Larrosa group reported the third method for achieving me ta -C – H ar y lation of ph enols via the ortho -directing eff ect of a tempor aril y int roduced c arboxyl group, thereb y ex ploring a CO 2 - based traceless directing group strateg y [ 108] (Figure 1.21 ). 1 Introduc tion 25 Figure 1.21 Us i ng a trace less carboxy l directing group relay strategy to ach ieve meta -C – H arylation of phenols. Metalation-directing meta -C-H functionalization The metalation-direc ting meta -C-H functionalization of are nes has also been reported. The Frost group described a Ru-catalyzed meta -sulfon y lation of 2-pheny lp y ridines. The strong ortho/para- directing e ffect of the Ru( II ) c enter b y σ -activation led to electrophilic sulfonylation para - to the Ru – C ary l bond [109] (Figure 1.22). Figure 1.22 Ru - ca talyz ed meta - sulfonylation of 2- pheny l pyridines. Ion pair directed meta -C- H borylation The ion pai r directing group was expected to achieve meta -C-H bo r y l ation b y P hipps and co - workers. [110] In the prese nse of a proper anionic s ulfonate ligand, b is(pinacolato)diboron and an 1.2 Meta -C-H Fu n ctional ization of Benz ene 26 iridium catalyst, a meta -C- H borylation product c an be obtained effective ly . But a small number of para -C-H borylation products also existed as byproducts (Figure 1.23). Figure 1.23 Ir -catalyz ed ion pair directe d meta -C- H b orylation. Ligand contolled m eta -C -H functionalization Nondirected selected meta -C-H a ctivation is an excellent method, considering no need to introduce and remove the dire cting group. In 2018, the van Gemmeren group reported nondirected meta-C- H functionalization wit h steric and electronic control of reg ioselectivit y . However, it is worth noting that para- and ortho -products were also observed in the reac tion [ 111] (F igure 1.24). Figure 1.24 Nond i rec ted meta - C-H functional ization. 1 Introduc tion 27 1.3 Distant Se l ective-C - H Functiona lizat ion of Naphthalene Naphthalene has a differ ent geometric structure from benzene. For ex ample, the bond lengths are not the same as that of benzene [112] (Figure 1.25). For the chemistry pro perties, they are also differe nt. As exhibi ted in Figure 1.26, the direct ing group gave the orth o -selective produ ct for benzene, and the meta -selective produc t for naphthalene under the same conditions. [113] Figure 1.25 Di fferent structure be tween naph thalene a nd benzene. [112] Copy right © 2020, Thiem e. Figure 1.26 The differe nce between nap hthalene an d benzene during selective C-H func t ionaliz ation. [113] Copyrig ht © 2015, Am eri can Chem ical Soci ety. For the C-H a ctivation of naphthalene, the y can be divided int o two ty pes based on the position of the directing group: direc ting group at 1 -positi on and direc ting group at 2-p osition (Figure 1.27). When the directing grou p is at 1 -position, many work has been published dealing with selective C-H functionalization, and the cha llenge is selective C5-H, C6-H and C7- H bond activation. [ 114] 1. 3 Di stant Se lective-C-H Funct ionalizati on of Naphthal ene 28 Figure 1.27 Two ty pes of naphth alene. According to m y knowledge, sele ctive C5 -H functionalization has not been reported. The functionalization of C6-H was just described from two papers b y Sakaki and Nakao group. [115,116] C6 -H bond was activated b y the coordination between an alumini um compound and an amide directing group. Thus, selective C6-H alk y l ation was achieve d with the help of a nickel cataly st (Figure 1.28). Figure 1.28 Se lectiv e C6 -H functional ization. Selective C7-H func ti onalization ha s not been achi eved until very recently. I n 2019, the Yan g and You group r eported the onl y example about selective C 7-H functionalization of naphthalene. [117] The palladium complex was ox idiz ed by F + . Th e mechanistic pathw ay incl udes C8 -H electrophilic activation, ary l migration and β -h y dride eliminatio n (Figure 1.29). As for th e second t ypes of naphth alene, di recting group at 2 -position (Figure 1.27, ri ght), 3- position functionalizatio n is usuall y the same as for benzene. [112] The stud y about C -H activation of the othe r positions is ver y few, onl y C4 -H f unctionalization was rep orted b y a few groups through meta -C-H functionalization. [118 – 122 ] Interestingly , bis C-H functionalization, both the C8 - H and C4 -H functionaliz ation were achieved b y the Yu group. [123] P yridine was used as th e template, in the presence of silver salt and palla dium catal yst, a 4,8-disubstitut ed product w as 1 Introduc tion 29 obtained in 78% y i eld ( Figure 1.30). How ever, selective mono - C8 -H functionalization is still unknown. Figure 1.29 Se lectiv e C7 -H functional ization. [117] Figure 1.30 Bi s C4 -H and C8-H functiona lization of n aphthalene. 1. 3 Di stant Se lective-C-H Funct ionalizati on of Naphthal ene 30 2 Aim and Strategy 31 2 . Aim and Strate gy From the int roduction part, we c an learn that 3 H -naphthop y rans are a kind of important photochromic compounds and the substituents ha ve a great effect on its photochromic properties. Consequently, it will promote the development of 3 H -naphthopyrans to discover novel methods on introducing different substituents into different position s of 3 H -naphthop y rans and to investigate the influence on photochromic properties by those substituted compounds . Hence , the first part of my thesis is to find useful methods to introduce subst ituents into key positions of 3 H -naphthop y r ans. On the one hand, because we want to apply 3 H -naphthop y rans on the silicon surfaces (Si (111)) in the futu re, 8-po sition, because of the lon gest distance f rom the pyran ring, is the perfect positi on for a linker. The 8-substituents will be kept. On the other hand, the positions we are interested in are 6- and 10-po sition, considering 6 -position substituents have a major influence on the thermal bleachin g rate an d only ver y few compounds with a 6-donating group were reported, 3 H -naphthop y rans with 6-electronic withdrawing substituent are still unknown. 10-position substituents a ffect the stabilities of the ope n for ms. The introduction of a 6- electronic withdrawing group or large r steri c 10-s ubstituents is ex pected. Therefore, selective C- H functionalization is a favourable choic e. S o far, no ex ample was reported about m eta -C- H functionalization of naphthop yrans. Introducing 10 -substituents will be interesting. Mo reover, selective C6 -H functionaliz ation is a c hallenge, because selective C8 -H functionalization of naphthalene is still unknown (Figure 2.1). Figure 2.1 Exp ec ted sele ctiv e C -H bond funct ionalizat i on of naph thopyrans. The second part of my thesis is devoted to explore the photochromic behavior of diff erent substituted 3 H -naphthopy rans. The investi gated s ubstituents include 2 -, 6- and 8-substituents in this work. For 2 -substituents, the effect of la rge steric substituent s wil l be explored. For 6- substituents, the influenc e of an elec tron withdrawing group and conjuga tion will be investiga ted. 2 Aim and Strategy 32 For 8-substit uents, ester , c arboxylic acid, hy drox ymethyl and ether methyl groups will be studied. In addition, the effec t of 3 -aryl substituents will also be investiga ted (Fi gure 2.2). Figure 2.2 The 3 H - napht hopy rans to be inv estigated. The research m ethod involves UV/Vis spectroscopy and in -situ NMR spectroscop y . The absorption spectra changes will be det ected du ring irradiation with UV light, visible light and in the dark. The fo rmation of different isom ers will be observed with in -situ NMR spectroscop y during UV irradiation. Furthermore, kinetic studies will be adopted in both room temperature UV/Vis experiments and low tempera ture in -situ NMR measurements. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 33 3. Synthesis of Re mote Selective C - H Functionali zation of Naphthopyrans In this chapter, the directing group at 8-position w as introduced and different s ynthe tic methods were explored to achieve re mote selective C-H bo nd functionalization of naphthopy rans. Figure 3.1 Rem ote s ele ctive C- H bond functionalization of n aphthopyrans. 3. 1 Meth o d Ⅰ : D i rect ed Selective C-H F unctionaliz ation In 2012, the Yu group reported palladium catalyzed meta -C-H activation of arene substrate s. [ 84] Encouraged b y this interesting research, we de signed our first s y nthesis method: palladiu m cataly z ed directed m -C-H activation of naphthop y rans. And the target mol ecule is described in Fig ure 3.2. Figure 3.2 Targ et molecule of s y nth e ti c method Ⅰ . 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 34 3.1.1 Route 1 of the Synthesis Figure 3.3 Pr oposed ret rosynthetic ro ute 1 about dir ected rem ot e C- H functionali zation of nap hthopy ran s. The retrosynthetic route 1 for sy nthesiz ing the target compound is shown in Figure 3.3. T he general strategy is described below: At first, the s y nthes is of targ et molecule naphthop yran 21 can be achieve d from compoun d 16 and proparg y l alcohol 20 under acid catal y s is . Then naphthalene 16 can be obtained throug h meta -C-H activation of naphthalene 13 . In addition, compound 13 c an be synthesized from c ompound 11 and naphthalene 5 through a nucleophilic subst itution reaction. As for compound 11 and propargy l alcohol 20 , both of them were literature reported. [65,84] 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 35 Synthesis of Compound 2-Bromom et hyl-6-(methoxymethoxy)naphthalene (5) Figure 3.4 Sy nt hesis of n aphthalen e 5 . Our synthetic path started with the commercial ly a vailable naphthol 1 (Fig ure 3.4). At first, an acid chloride was formed b y reaction with thi ony l chl oride, after substituti on with methanol via an addition-elimination mechanism, naphthol 2 was prepared in 97% y i eld. [ 124] At second, considering the proton of the h y drox y l group will influence the next step C -H activation, the hydroxy l group in naphthol 2 needs to be protected. Sodium hy dride w as used for the removal of the proton from the hy drox y l group in naphthol 2 . Then the chloride of (chloromethyl) methyl ether (MOMCl) c an be replaced with the intermediate naphthola te. Afterwards, the naphthalene 3 with the protecting group (MOM) was obta ined in 95% y ield. For the s y nthesis of naphthalene 4 , classical LiAlH 4 was used as the reductant, and after 24 hours in THF , compound 3 was reduc ed to compound 4 and the latter isolated in 85% y ield. [1 25] As for the bromination of compound 4 , the commonly used PBr 3 was not suitable for this reaction. The possible reason is the produced p hosphorous acid , which will induce the deprotection of the hydroxy l group. Then so ft N -bromosuccinimide (NBS) is a favorable choi ce. After 10 min to a mixture of N BS and dimethyl sul fide (DMS), compound 4 was added a nd product 5 wa s obtained with a good yield of 88% after 4 h reac tion ti me in DCM. Notabl y , because product 5 is sensitive to sil ica gel, only a short plug of silica gel was use d for the purification of the crude product. The product 5 was also found to undergo easily deco mposition under air and daylight in the fridge. Thus, stora ge under ar gon and shieldin g fr om light is nec essar y . The mechanism is depicted in Fig ure 3.5. 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 36 The process c an be divided into two parts. The fir st step is the formation of compound 31 . At first, DMS as a nucleophile attacke d the bromine of NBS, resulting in formation of the succinimide anion 29 . After nucleophilic subst itution and leaving o f bromi de, compound 3 1 was formed. The second step is the reaction between 31 and the starting material 4 . The sulfur atom of 31 was attacked b y compound 4 and then compound 31 was converted into int ermediate 32 , which owns a better leaving group co mpared to the ini tial h y d rox y l group. [126,127] Accordingl y , bromine anion attacked 32 and product 5 was formed. Figure 3.5 M echanism of the bromination re action. Synthesis of 2-(3,5-Di-tert-butyl-2-hydroxyphenyl)acetonitrile (11) Figure 3.6 Sy nt hesis of com pound 11 . 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 37 The s ynthesis of compound 11 was reported in the literature before. [84] Commerc ial ly available compound 6 was chosen as the starting materia l. Firstly, in the pre sence of NaH, MOMCl was used for protecting the hydroxy l g roup of compound 6 . Then compound 7 was reduced to compound 8 with a good y i eld of 93% by usin g NaBH 4 as the reductant. The third step is bromination of compound 8 , employing the sam e condition s as for the bromination reaction of compound 4 . After work up, the crude produc t 9 w as dire ctly used for th e nex t step, considering it is sensitive to sil ica gel. In the pre sence of NaCN and H 2 O, the nitrile grou p was introduced, and compound 10 was isol ate d in 68% y ield over 2 steps. Signific antly, NaCN is ver y toxic, so the reac tion should be handled in a well-maintained f ume hood and the operator should alwa y s have appropriate protection. The last step is deprotection of compound 10 . I n the solvent of h y drochloric acid and acetonitrile, compound 10 can b e convert ed into product 11 with a y ield of 71% (Figure 3.6). Synthesis of 2-(3,5-Di-tert-butyl-2- ((6 -(methoxym ethoxy)naphthalen-2-yl)methoxy)phenyl)-2- isobutyl-4-methylpentanenitrile (13) Figure 3.7 Sy nt hesis of com pound 13 . With the directing group 11 and b enz y l bromide 5 in hand, after deproton ation of compound 11 induced b y NaH, we can afford substrate 12 b y a sim ple nucleophilic substitution reaction in 74 % y i eld after 4 h in DMF. For the introduction of two iso butyl group, L D A was emplo ye d as the deprotonation reagent fo r the α -H of the nitrile group. Then the second is o -butyl group can be 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 38 introduced into the α -position of the nitrile grou p. Afterwards, product 13 was obt ained with a good yield of 89% ( Fig ur e 3.7). C-H functionalization of naphthalene 13 Figure 3.8 C- H functionaliz ation of naphth alene 13 (a. the ratio wa s from 1 H NMR analysis of the unpurified rea ction mixture using CH 2 Br 2 as the intern al standard ). The naphthalene 13 with dire ctin g group was prepared as the startin g material of th e C- H functionalization reaction. The other startin g m aterial is the c ommercial ly available eth yl acrylate. In the presence of Pd(OPiv) 2 and Ag (OPiv), after 4 2 h reflux in DCE, product 14 was isolated with a y i eld of 46% as ex pected. Interestingl y , product 15 was also detected and isolated in 7% y ield . The ratio of the two pro ducts was 14 : 15 = 7:1 from 1 H NMR analysis of the unpurified re action mixture (Figure 3.8). There are two reasons for the formation of 15 : 1) fr om spatial distanc e, m ’ - C is close to m -C, so that palladium can also activate the m ’ -C-H bond; 2) m ’ -position is a favorable position for classical Friedel-Crafts reaction. In addition, there were 16% of starting material 13 left, which ca n be rec yc led. To characterize the struc ture of the products 14 a nd 15 , 2D NMR spectra were obtained, includin g 13 C DEPT NMR spectrum, 1 H- 13 C HMBC NMR spectrum, 1 H- 13 C HMQC NMR spectrum and 1 H- 1 H COSY NMR spec trum (see Chapter 8.2). At first, the c hemical shifts of H-16, H-18, H-29 and H-30 were easil y identified. For produ ct 14 , the additional peaks in the aromatic area were as follows: a sin glet at 7.86 ppm, a doublet at 7.75 ppm, a singlet at 7.70 ppm, a doublet at 7.60 ppm and a doublet of doublet at 7.23 ppm. One part of the 1 H- 13 C HM BC NMR spectrum and 1 H- 1 H COSY NMR spectrum of 14 is displa y ed in F igure 3.9. Correlations were observed be tween C-13 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 39 Figure 3.9 500 MHz 1 H- 13 C HMBC NMR spec trum ( up) and 1 H- 1 H COSY NMR spectrum ( down) of 14 . 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 40 Figure 3.10 50 0 MHz 1 H- 13 C HMBC spectrum (up) an d 1 H- 1 H C OSY NMR spectrum ( down) of 15 . 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 41 and two singlet peaks at 7.86 and 7.70 ppm, and a we ak correlation was found between those two singlets. A ccordingly, th ose two sin glets were a ssigned to H -1 and H-9 and the acr y li c ester substituent should be at m -position. When the correlation was observ ed betwe en C-29 and the singlet at 7.70 ppm, the singlet at 7.70 ppm wa s assigned to H -1 and the other singlet was assi gned to H-9. Correspondingly, H-4, H-6 and H-7 were i dentified, when doublet of doublet at 7.23 ppm was observed to be correlated with doublets at 7.75 and 7.60 ppm, respectively . For product 15 , ther e were sti ll four peaks to be identified in the aromatic area: one singlet at 8.19 ppm, one doublet at 7.81 ppm, one doublet of doublet a t 7.59 ppm and one multi plet at 7.50- 7.18 ppm. The 1 H- 13 C HMBC NMR spectrum in Figure 3.10 reveals that C-13 was correlated with the singlet at 8.19 ppm a nd the doublet of doublet at 7.59 ppm, respectively. Therefore, th e sin glet was assigned to H-9, and the doublet of doublet signal at 7.59 ppm was ass igned to H -1. W hen a corre lation was found between H -1 and doublet at 7.81 ppm in the 1 H- 1 H COSY NMR spectrum (Figure 3.10), the doublet at 7.81 ppm was assigned to H-2. Moreover, C-3 was noticed to be corre lated with H-29, while no correlation was detected between C -8 and H-29. Thus, the acr y lic ester substituent should be at m ’ -position. At last , the mutiplet at 7.50-7.18 ppm was assi gned to the mixture of H-6 and H-7. The proposed mechanism for thi s reaction is presented in Figure 3.11, based on the li terature . [ 85,128] The useful catalyst is co mpound 35 , which was f ormed from Pd(OPiv) 2 a nd Ag (OPiv). At first, the nitrile group of comp ound 13 coordinated with silver. Then the reaction was divided int o two directions, which resulte d in two different prod ucts: 14 and 15 . If th e carbon at m -position coordinated with palladi um, thro ugh a concerted metalation−deprotonation process, meta -C- H activation was achieved and intermediate 39 was obtained. M eanwhile, e th y l acr y l ate c an coordinate with palladium. After alken e insertion, intermediate 42 was obtained. At last, product 14 was achi eved through β -hydride elimi nation reaction, and catalyst 35 was reformed through the oxidation by Ag (O Piv). On the other hand, if th e catal y st coordinated w ith the carbon at m ’ - position, product 15 can be obtained through similar processes. 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 42 Figure 3.11 P r oposed m echani sm of C- H functionalization of naph t halen e 13 . 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 43 Synthesis of Ethyl (E)-3- (3 -((2,4-di-tert-butyl-6- (4 -cyano-2,6- dim ethylheptan-4- yl)phenoxy)methyl)-7-hydroxynaphthalen-1-yl)acrylate (16) Figure 3.12 Sy nt hesis of com pound 16 . The m-C-H activation product 14 was emplo y e d for the final s ynthesis of a naphthop yran. Afte r 30 min in the solvent of hy d rochloric acid a nd acetonitrile, the ke y building block 16 wa s isolated with a yield of 52% (Figure 3.12). Synthesis of 1- (2 -Chlorophenyl)-1- (4 -(pyrrolidin -1-yl)phenyl)prop- 2- yn -1-ol (20) Figure 3.13 Sy nt hesis of com pound 20 . 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 44 S y nthesis of compound 20 started with the commercial ly ava ilable compound 17 (Fig ure 3.13). At first, compound 17 was activated b y trieth y lamine. Then aniline nucleophilic attacked the activated acid chloride 17 . Af ter formation of trie thy lamine hydrochloride, product 18 was obtained in 97% y i eld. [1 29] The conversion f rom co mpound 18 to 20 was achieved according to the reported li terature. [65] The synthesis of compound 18 from 19 went through a Vilsmeier-Haack reaction. The mechanism is demonstrated in Figure 3.14. The reaction was carried out in two steps. The first step was the formation of the Vilsmeier reagent: im inium salt 57 . The second step was the reaction between N - pheny lp y rrolidine and iminium salt 57 to afford compound 19 . At first, POCl 3 was attacked b y the ox yge n of 18 ’ to afford intermediate 54 . Afte r the le aving of the chlori ne anion, int ermediate 55 was generated. Then the carbon of 55 was nucleophilic attacked by th e chlorin e anion. After leaving of the phosphorus salt, iminium salt 57 was fo rmed. Afterwards intermediate 58 was obtained through an e lectrophilic aroma tic substitution reaction be tween N -pheny lp y rrolidine and iminium salt 57 . After elimination of h y drogen chloride, intermediate 59 was obtained. At last, product 19 was isolated in a y ield of 45% by h y drol y sis through aqueous workup. For the pre p aration of compound 20 , firstl y , lithium (trimeth y lsilyl)acetylide was prepared in -situ during the re action between trimethylsil y lacet y lene and n -but y ll ithium solu tion. Then the solution of starting material 19 in THF w as added. By the addition of potassium hydroxide in methanol , the trimethylsil y l group was r emoved and the product propargy l alcohol 2 0 was obtained in 86% y i eld. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 45 Figure 3.14 Mechanism of the Vilsm eier-H aa ck reaction. Synthesis of naphthopyran 21 With the building block 16 and propargyl alcohol 20 in hand, the preparation of naphthopyran 21 was investigated with the method reported b y Gabbutt et al [65] (Figure 3.15). Unfortunately, naphthopyran 21 was no t detected, after 1.5 h sti rr ing with acidic aluminium oxide in toluene. Approximately 85% of starting material 16 was left. I n addition, b y p roduct 22 was isolated in 40% y i eld, which was generated through a Me y e r – Schuster rearrangement. [31,130] The mechanism is described in F igu re 3.16. I n the beginning, compound 20 wa s protonated b y the acid catalyst. After le aving of on e molecul e water, intermediate 61 was formed. Then wate r nucleophilic attacked t he allene group of 61 , and intermediate 62 was ge nerated. After deprotonation, intermediate 63 was obtain ed. At l ast, by product 22 was formed through keto-enol tautomerism. 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 46 Figure 3.15 Sy nt hesis of naphtho pyran 21 . Figure 3.16 Mechanism of Meyer – Schust er rearrang ement. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 47 3.1.2 Route 2 of the Synthesis Considering it is difficult to sy nth esize naphthop y ran s using m -C-H functionaliz ation of the naphthalene 16 fr om rout e 1, route 2 was proposed in Fig ure 3.17. In this way , the naphthop yrans with directing group, N4 and N6 , were pre pared firstl y . Then remote C-H functionalization of the naphthopyran can b e in vestiga ted. Naphthop yrans N4 and N6 can b e o btained throu gh acid- cataly z ed etherification of naphthol 23 , followed b y Claisen rearrangement, enolization, 1, 5- hydrogen-shift and electroc y c lization with propargy l alcohols 20 and 25 , respectivel y . Naphthol 23 can be p repared through de protection of comp ound 13 and the protected precursor 13 can be ge nerated from compound 11 and 5 . Figure 3.17 P r oposed ret rosynthetic route 2 about directed rem ot e C- H funct ionaliz ation of naphthopy ran s N4 and N6 . 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 48 Synthesis of 2-(3,5-Di-tert-butyl-2- ((6 -hydroxynaph thalen-2-yl)methoxy)phenyl)-2-isobutyl-4- methylpentanenitrile (23) Figure 3.18 Sy nt hesis of n aphthol 23 . The s ynthesis rout e 2 st arted from compound 13 , w hich was s y nthesiz ed in route 1 (Chapter 3.1.1). In the solut ion of 2M h ydrochloric acid in a cetonitrile, after 30 min stirr in g at 70 ℃ and a queous workup, the protection group MOM was removed and product 23 was isolated in 55% y ield (Figure 3.18). Synthesis of 1,1-Bis(4-fluorophenyl)prop-2- yn -1 -ol (25) Figure 3.19 Sy nt hesis of pr opargy l alcohol 25 . Propargy l alcohol 25 was s y nthesized from commercial ly available compound 24 based on the known literature. [58] After 86 h stirring in THF, p roduct 25 was isolated in a good y i eld of 78% through a Grignard reaction with eth y n y lmagnesium chloride (Figure 3.19). Synthesis of naphthopyrans N4 and N6 Figure 3.20 Sy nt hesis of n aphthopyran N6 . 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 49 For the synthesis of na phthop y ran N6 , compounds 23 and 25 were e mplo y ed as starting materials and PPTS wa s used as the catal y st. [ 131] After 40 h refluxing in DCE solution in the presence of (MeO) 3 CH, N6 wa s afforded in 81% y i eld (Figure 3.20). The mechanism is presented in Figure 3.21. At first, in the presenc e of the acid catalyst, one molecule of water was removed and intermediate 66 was formed. Then 66 was nucleophilic attacked b y compound 23 and int ermediate 67 was obtained. B y a C laisen rearrangement, intermediate 67 was converted to intermediate 68 . Subsequently, intermediate 69 was obtained via keto-enol tautomerism and aromatization. After [1, 5]-H-Shift, intermediate 70 was formed. At last, product N6 was prepared through an electrocy clic ring closure reaction. Figure 3.21 Mechanism of the synthes is of naphtho pyran N6 . 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 50 From the investigation of the s ynthesis methods of naphthop y ran N1 (Table 3.1), it was revealed that method A was not s uitable compared with method B. Presumably because naphthop y ran N1 is unstable at high temperature, considering the reaction temperature is more than 110 ℃ for method A while 84 ℃ for method B. Considering naphthop y r an N4 has a sim ilar structure with N1 , method B was emplo y ed for the synthesis of naphthop y ran N4 . Compounds 23 and 20 were starting materials and acidic aluminium oxide was chosen as the catal y st. [ 65] After 1.5 h reflux in toluene, naphthopyran N4 was obtained in 55% y ield ( Figure 3.22). The mechanism is similar to the mechanism of the s y nthesis of naphthop y ran N6 . Table 3.1 Op timization of t he syntheti c methods. a Entry Method Reaction tim e Yield 1 A 27 h 23 % 2 B 26 h 46 % [a] 0.5 mm ol scale. Method A: PPTS ( 5 mol%), (MeO) 3 CH (2 equiv ), DC E, reflux; Method B: acid ic Al 2 O 3 (7.7 equiv), toluene, reflux. Data fr om PhD Thesis of Dian a Liebm ann in the Rück- Braun group. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 51 Figure 3.22 Sy nt hesis of n aphthopyran N4 . Remote C-H functionalization of naphthopyran N6 Figure 3.23 C- H functionaliz ation of naph thopyran N6 . With the prepared naphth opyran N6 with the directing group in h and, the reaction of remote C - H functionalization of N6 , catal y z ed b y Pd(OPiv) 2 , in the presence of Ag(OPiv), b y re fluxing in DCE solution with acrylic acid ethy l ester for 48 h w as i nvestigated. S urprisingly, the m -C-H activation product 26 was not detected. However, the 6-posit ion C-H activation product N7 was isol ated b y chromatogra ph y in 17% yield (Figure 3.23). 3. 1 Me thod Ⅰ: D irected Sel ective C -H Function alizatio n 52 To characterize the stru cture of N7 , 2 D 13 C DEPT NMR spectrum, 1 H- 13 C HMBC NMR spectrum, 1 H- 13 C HMQC NMR spectrum and 1 H- 1 H COSY NMR spectrum were acquired (see Chapte r 8.2). Accordingly, it is eas y to identify the chemical shi fts of H -1, H-2, H-14, H-15, H-20, H-21, H-26 and H-28. A sin glet at 8. 16 ppm, a doublet at 8.05 ppm, a doublet of doublet at 7.68 ppm and a singlet at 7.46 ppm were sti ll unident ified in the aromatic area. Base d on the 1 H- 13 C HMBC NMR spectrum (F igure 3.24), it was obser ved that C-23 wa s correlated with the si nglet at 8.16 ppm and the doublet of doublet at 7 .68 ppm, respectivel y . In the 1 H- 1 H COSY NMR spectrum (Figure 3.24), there existed correlations betwe en the doubl et of d oublet at 7.68 ppm and th e doublet at 8.05 ppm, and a weak correlation be tween the doublet of dou blet at 7.68 ppm and the s inglet at 8.16 ppm. As a result, the singlet at 8.1 6 ppm was assigned to H -8, the doublet at 8.05 ppm was assigned to H- 11, and the doublet of doublet at 7.68 ppm was assig ned to H-10. At last, H-14 was observed to corre late with C-7, while the re was no correlation betwe en C-4 and H- 14. Hence, the acry lic ester substituent should be at 6-position and the singlet at 7.46 ppm was assignned to H-5. Remote C- H functional ization of naphthop y ran N4 was also investi gated under the same conditions. Unfortunately , ther e was no desired C - H functionalization product observed from the reac tion, and onl y damaged N4 was found. To investi ga te the effect of directin g group, naphthopyran 28 was pr epared accordin g to the literature [131] . After 48 h reflux under the same conditions, almost 100% of starting materials were left obs erved from 1 H NMR spectroscop y (Figure 3.25, for 1 H NMR spectrum, see C hapter 8.1, Figure 8.2 ). T he results indicated that the reac tion is obviousl y accelerated b y the coordination of the nitrile group to the cataly st and the directing group can affect the reactivit y and se lectivi ty o f the C- H fun ctionalization reaction. Figure 3.25 C- H functionaliz ation of naph thopyran 28 w i thout direct i ng g r oup. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 53 Figure 3.24 50 0 MHz 1 H- 13 C HMBC (up) and 1 H- 1 H COSY NMR spectrum (down) of N7 . 3. 2 Me thod Ⅱ: No ndirected Meta -C -H Fun ctionalizat ion 54 3. 2 Meth o d Ⅱ: Nond i rected Me ta -C- H Functi onalization Nondirected selected C-H activation is an attractive method, because buil ding complex directing groups is not necessary in this way . C orrespondingl y , we do not need to remove them afterwards. In 2018, the van G emmeren group repo rted t heir good results about d ual l igand- enabled nondirected C-H olefination of benzene compounds, [111] which ga ve us an in spiration to investigate a method to achieve meta -C-H functionalization of naphthopy r ans. The proposed s y nthetic route is shown in Figure 3.26. C onsidering the intricate structure of naphthopyran 72 , a chieving C -H olefin ation of n aphthalene 3 firstl y is a f avorable choice. Then after d eprotection, naphthol 71 can be obtained. Un der acidic catal y sis and reaction with propargyl alcohol, the final C -H fu nctionalization and the formation of naphthop y r an 72 can b e achieved, based on the research e xperience of the Rück-Braun group. Figure 3.26 P r oposed ret rosynthetic route about n ondirected m - C - H functionalization of n aphth alene. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 55 Synthesis of Ligand 1 Figure 3.27 Sy nt hesis of ligand 1 . Our synthetic path starte d with the s ynthesis of li gand 1 . I n the presence of piperidine and acetic acid, ligand 1 was obtained from aldeh y de 73 and dimeth y l malonate 74 with a y i eld of 45%, [111] through a Knoevenagel condensation (Figure 3.27). The me chanism is des cribed in Figure 3.28. Firstly, compound 74 was deprotonated b y the pip eridine. Intermediate 75 attac ked aldeh yde 73 . After protonation, 77 w as formed. Finall y , liga nd 1 was obtained aft er the elimination of one molecule water. Figure 3.28 The m echanism of the Knoevenagel cond ensation. 3. 2 Me thod Ⅱ: No ndirected Meta -C -H Fun ctionalizat ion 56 Table 3.2 Cont r ol expe riments. a The starting material 3 was prepared according to method Ⅰ (Cha pter 3.1.1) and ligand 1 was also prepared. As for eth y l acrylate 27 , Pd(OAc) 2 , Ag OAc and N - acetyl-glycine, the y are all commercial ly available. He nce the experiments of nondirected C -H activation of naphthalene 3 were investigated under the conditions of Table 3.2. After 24 h r eflux, about five different products were identified, whi ch could not be separated from each othe r b y column chromatogra p h y. According to the in formation from the literature, [ 111] the C -H activation prefers to happ en in th e Entry Solvent Time Conversion Product ratio b 1 3 equiv HFIP 24 h 84 % 25:30:32:8:5 2 1 equiv HFIP 24 h 63 % 60:14:9:11:6 3 3 equiv HFIP 14 h 43 % 54:14:6:14:1 2 4 3 equiv DCE 14 h 40 % 48:22:10:4:1 6 [a] 0.2 mm ol scal e. Pd(OAc) 2 (10 mol% ), N -Acety l-glycine (30 mol%), ligand 2 (20 m ol%), AgOAc (0.6 mmol), solvent (2 m L), 90 o C. Yields were determined by 1 H NMR analysis u sing CH 2 Br 2 as the internal stand ard (for spectrum , see Chap ter 8.1 , Figure 8.1). [ b ] Ratios were id entified by the hydrogen signals of alkene subs tituents. 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 57 ortho - and meta -position of the electron-withdrawing substituent and the meta -position of the electron rich substituent. Thus, five possible stru ctures are p resented in Table 3.2. We tried to control the ratio b y reducing the r eaction time, decreasin g the amount of e th y l acr ylate 27 and changing the solvent. However, unfortunatel y, iso lation of pure produ cts was not achieve d. What we isolated w as always the mi xture. There fo re, we cannot continue with this method an y more. This nondirected meta -C -H activation seems to be suit able for benzene c ompounds but not for naphthalene compounds. Hence effective methods for nondirected me ta -C-H activa tion of naphthalene should be investigated in the future. 3. 3 Di scussion 58 3. 3 Di scussion 3.3.1 The Selection for C-H Functionalization of Naphthopyran N6 Remote C-H func ti onalization of naphthalene 27 resulted in m - an d m ’ -sel ected products, while 6- selected product N7 was obtained fr om remote C -H functionalization of naphthopy ran N6 (Figure 3.29). Reviewin g the mechanism of remote C-H f unctionalization of naphthalene in Fi gure 3.11, intermediates 38 and 47 are the key intermediates in the process of C-H activation. According to the computation from the literature, [85] the directing group coordinated with catalyst favored to activate meta -C-H bonds for normal benzene compound. For naphthalene 13 , the m ’ -C-H is adjace nt to m -C-H, thus m ’ -C-H fun ctionalization produc t 15 was formed. However, in the m -C- H (10-position) act ivation process of n aphthop y ran N6 , ther e exist large steric restrictions in th e structure of the intermediate 83 . C onsequently , 6-selected C-H functionalization product N7 was formed since the intermediate 84 is favorable (Figure 3.30). Figure 3.29 C- H functionaliz ation of naph thalene 13 and naph thopyran N6 . 3 Sy nthesis of Rem ote Selective C-H Func tionalizatio n of Nap hthopy ran s 59 Figure 3.30 The intermediates of the C- H activation processes of naphthalen e 27 and naphthopy r an N6 . 3.3.2 The Failure for Formation of Naphthopyran 21 in Route 1 of Method Ⅰ The last step of route 1, the conversion from compound 16 to naphthopyra n 21 , wa s not achieved. But b y produ ct 22 was isolated in 40% y ield. In order to investi ga te the reason, a related mechanism is shown in Figure 3.31, indi cating th at the former two steps were th e same for the formation of the two products. If inter mediate 61 is nucl eophilic attacked b y naphthol 16 , intermediate 85 will be form ed. Th e r eaction will follow Route A. After Claisen rearrangement, keto-enol tautome rism, [1, 5] -H-shift and electro cy clic rin g closure reaction , product 21 will be obt ained. On th e contrar y , if the allene form of intermediate 61 is nucleophilic attacked b y th e water molecule, the reaction will follow Route B. Then b y product 22 will be generated through Me y er – S chuster rearrangement. Therefore, Route A and Route B are two compet ing reactions. I nterestingl y, under the same conditions, naphthop y r an N4 was prepared success fully, while naphthop yran 21 was not. The onl y differe nce betw een the starting materials of the two reac tions is the meta -substituent group of compound 16 . Thus, naphthop y ran 21 was not genera ted from compound 16 and 20 , presumabl y resulting from the meta -substituent group, which hindered the formation of intermediate 85 . The reac tion went alon g route B a nd b y product 22 was ge nerated. 3. 3 Di scussion 60 Figure 3.31 Mechanism for the s ynt hesis of nap hthopy ran 21 and byprod uct 22 . 4 UV/Vis Spe ct rosco py 61 4 . UV/V is Spec trosco py The photochromic properties of 7 different naphthop y rans were investi ga ted, and all the d ata are from the experiments of an Avantes AvaSpec Dual-channel Fibre Optic Spectrometer (for details, see C hapter 7.2) in this chapter. All the seven c ompounds are divi ded into 2 types: two stat es system and three state s system (Figure 4.1). Those naphthopy rans without residual color left after thermal back reaction are considered as “two st ates s y stem” (initi al state - P SS (UV) ). Otherwise, they are regarded as “three states s y stem” (initial state -PSS(UV)-PSS(dark)). Figure 4.1 St ructures o f different k inds of naph t hopyra ns. 4.1 UV/V is Studie s of Two States S ystem : Naphthopyrans N 1, N2, N 3 and N4 4.1.1 UV Irradiation Figure 4.2 St ructures o f naphthopyrans N1 , N2 , N3 and N4 . 4.1 UV/Vis St udies o f Two States Sy st em : Naphthopyrans N1 , N2 , N3 and N4 62 Figure 4.3 Absorption spectra ch anges of a) N1 , b) N2 , c) N3 and d) N4 upon U V irradiat i on ( N1 , N2 an d N3 : 340 nm, 12 m W/cm 2 , N4 : 365 nm, 110 m W/cm 2 , 1.5×10 -5 M in acetoni trile, 293 K ). The structures of the naphthop yrans N1 , N2 , N3 and N4 are ex hibited in Figure 4.2. From the initial UV absorption spe ctra of 4 compounds (Figure 4.3), it was found that two strong absorptions were centered at 261 nm and 260 nm in the spectra of naphthop yran N1 and N2 , respectively , while two strong absorptions around 250 nm were detected in the sp ectra of N3 and N4 . Compared 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Absorbance Wavelength (nm) 0 s 4 s 6 s 10 s 16 s 34 s a) 300 400 500 600 700 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Absorbance Wavelength (nm) 0 s 10 s 20 s 40 s 60 s 100 s b) 300 400 500 600 700 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Wavelength (nm) Absorbance 0 s 2 s 4 s 7 s 12 s 18 s 30 s 60 s c) 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) 0 s 2 s 4 s 10 s 22 s d) 4 UV/Vis Spe ct rosco py 63 with the spectra of N3 and N4 , the spectra of N1 and N2 hav e a bathochromic shift by 10 nm, which is a consequence of the ex tended π conjugation of carbox y lic acid este r group at 8 -position. Upon UV irradiation, four new visible absorption bands which are centered around 561-592 nm for N1 , N2 , N3 and N4 emerged, which a re corresponding to the ring-open for ms: TC and TT, and the absorption peaks at 2 50-260 nm were r educed. After less than 2 min , all these 4 compounds can reach a photostationary state (PS S). I t was not ed that the absorption spectra of open forms of N1 and N2 also hav e a bathochromic shift with respect to that of N3 and N4 . The λ max of open forms of naphthopy rans bearing 8-substituent follows the order: Ester > Carboxy li c acid > E ther methyl > H y drox ymethyl. As it is depicted in Tabl e 4.1, t pss is the time need ed to arrive at the PSS. Naphthopy ran N1 is the fastest compound to arr ive at the PSS. Moreover, the speed of the ring opening reaction was affected b y the li ght intensit y . If i rradiated with 340 nm, 12 mW/cm 2 light, it took 30 seconds to arrive at the P SS for compound N1 , while 15 seconds we re n eeded under 365 nm, 110 mW/cm 2 light irra diation. Table 4.1 Ab sorption p roperties of N1 , N2 , N3 and N4 in the procedur e of UV irradi ation. a 4.1.2 Therm al Back R eaction As displaye d in Figure 4 .4, once UV light was switched off, all the open forms of naphthop y ran N1 , N2 , N3 and N4 can return to the closed fo rms thermally. The absorbance changes at λ max o f open forms were moni tored in Fig ure 4.5 and 4.6. For N1 , N2 , N3 and N4 , a diff erent position of λ max was not obse rved. Therefore, th e λ max of the TC and TT forms can not be dist inguished. Naphthopyra n λ m a x [nm ] (Closed form ) λ m a x [nm ] (Open form s) λ iso [nm ] t pss [s] N1 261, 318 592 301 30, 15 b N2 260, 315 571 301 106 N3 249, 265, 302, 317 , 347, 36 3 561 289 43 N4 b 250, 261, 300, 315 , 347, 362 567 288 24 [a] 1.5×10 -5 M in acetonitrile, 293 K, UV light: 340 nm , 12 m W/cm 2 . [b] UV light: 365 nm , 110 m W/cm 2 . 4.1 UV/Vis St udies o f Two States Sy st em : Naphthopyrans N1 , N2 , N3 and N4 64 Notably, there was no residual color left. For compound N1 , after more than 5 times UV/ dark cy cles, residual color was detected, wh ich was no t observed due to the TT form, but because of the decomposition of the naphthop y ran. Th e decrease in absorbance of N1 at PSS of dif ferent cy cles co rrelates with t he increase in remainin g absorbance ( residual color). However, the naphthopyran N3 has a diffe rent behavior and no residual color was observed. Additional c y cles were not inve sti ga ted for N2 and N4 because of the slow thermal back ra tes. Figure 4.4 Absorption spectra changes of a) N1 , b) N2 , c) N3 and d) N4 during t herm al relaxation ( c = 1.5×10 -5 M in ac etonitrile, 293 K). In general, there exist two processes: TC → CF and TT → TC , and the latter one is slower. A common way of describing the bleaching of the colored forms is b y introduction of t 1/2 and t 3/4 values, which are defined as the ti me taken from absorbance to reduce b y ½ and ¾ of the initial absorbance, respectivel y. The thermal bleaching kinetics were calculated from time-resolved 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Absorbance Wavelength (nm) 0 s 4 s 8 s 14 s 22 s 40 s 135 s a) 300 400 500 600 700 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Wavelength (nm) Absorbance 0 s 40 s 80 s 140 s 220 s 340 s 740 s 7500 s b) 300 400 500 600 700 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Absorbance Wavelength (nm) 0 s 20 s 50 s 90 s 140 s 210 s 300 s 700 s c) 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) 0 s 40 s 180 s 420 s 740 s 1340 s 5340 s d) 4 UV/Vis Spe ct rosco py 65 absorption spectra, b y fi tting the experimental data to the biexponential decay ( E quation 1 ) (Fitting infor mation see Chapter 7.2). [ 37,42,132] A(t) = A 1 e - k1 t + A 2 e - k2 t + A th (1) Where A (t) is the absorbance at the λ max , A 1 and A 2 are contributions to the initial absorbance A 0 , k 1 and k 2 a re ra te constants of fast and slow components, respectively . A th is the residual absorbance whe n time ap proache s infinit y. Spectrokinetic data are presented in Table 4.2. Figure 4.5 C olorat ion/decolorat ion cy cles f or a) n aphthopyran N1 (m onitoring waveleng th is bet ween 5 91 and 592 nm) and b) naphth opyran N3 (monito ring wav elength is between 555 and 556 nm) in MeCN (c = 1.5×10 -5 M) at 293 K. The grey regions: UV light : 3 40 nm, 12 m W/ cm 2 . Non -mark ed reg i ons p resent the periods when th e s ample w as i n the dark . The data of Table 4.2 indicate that t 1/2 and t 3/4 of naphthopy ran N1 are 12 and 25 s, respectively , which are quite smaller t han that of N3 (t 1/2 = 91 s, t 3/4 = 187 s). Compared with N3 , the k 2 of N4 ( k 2 = 1.33×10 -3 s -1 ) is only a sixth of that of N3 ( k 2 = 7.62×10 - 3 s -1 ), althoug h the k 1 of N4 ( k 1 = 9.89×10 -3 s -1 ) is larg er than that of N3 ( k 1 = 7.62×10 -3 s -1 ), naphthop y ran N4 still has the slowest thermal back reaction (t 1/2 = 518 s, t 3/4 = 1140 s). B oth k 1 and k 2 of N1 are ver y large: the k 1 of N1 ( k 1 = 9.09×10 -2 s -1 ) is approximately 12 times a s fast as that of N3 ( k 1 = 7.62×10 -3 s -1 ), and 9 times as fast as that o f N4 ( k 1 = 9.89×10 -3 s -1 ). The k 2 o f N1 ( k 2 = 4.71×10 -2 s -1 ) is about 6 ti mes as f ast as that of N3 ( k 2 = 7.62×1 0 -3 s -1 ), and 35 times as fast as that of N4 ( k 2 = 1.33×10 -3 s -1 ). According l y , the thermal ba ck speed o f naphthop y ran N1 is the f astest . Unexpectedl y , both k 1 and k 2 of N2 ( k 1 = 5.72×10 -3 s -1 , k 2 = 3.5×10 -4 s -1 ) are smaller than that of N3 . The possible reason is the presence of a dim er structure of the acid substituted naphthop y ran N3 , [133] and the photochromic properties a re 0 1000 2000 3000 4000 5000 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 Time (s) Absorbance N1 in MeCN 591-592 nm a) 0 1000 2000 3000 4000 5000 0.0 0.1 0.2 0.3 0.4 0.5 Absorbance Time (s) N3 in MeCN 555-556 nm b) 4.1 UV/Vis St udies o f Two States Sy st em : Naphthopyrans N1 , N2 , N3 and N4 66 impacted b y that. W hen N3 was inv estiga ted in different solvents, its photochromic properties changed a lot (For details, see Chapter 4.1.4). Fo r an overview of photochromic properties o f two states s y stem naphthop y rans, the k 1 and k 2 of n aphthop y rans be aring an 8 -substituent follows the order: Hydroxy meth y l < Ether meth y l < Ester. Figure 4.6 Absorbance chang es monitored at λ max for a) naphthopyran N2 (m onitoring wavelength is between 579 and 580 nm) and b) naphthopyran N4 (monito ring wavelength i s between 567 and 56 8 nm) i n MeCN (c = 1.5×10 -5 M) at 293 K . The g rey regions : UV light irradiation ( N2 : 340 nm, 1 2 mW/ cm 2 ; N4 : 365 nm, 110 mW/cm 2 , irradiation for 63 s). Non-m arked reg ions present the periods when the sample was in the dark . Table 4.2 Photo chrom ic properties in the procedu r e of therm al back react ion. A 1 , A 2 , A th , k 1 and k 2 are the fitting param et ers from Equation 1 ; t 1/2 , t 3/4 and A 0 were obta ined from experim ental data. a 0 1000 2000 3000 4000 5000 6000 7000 8000 0.00 0.05 0.10 0.15 0.20 0.25 Absorbance Time (s) N2 in MeCN 579-580 nm a) 0 1000 2000 3000 4000 5000 6000 0.0 0.1 0.2 0.3 0.4 0.5 0.6 N4 in MeCN 567-568 nm Absorbance Time/s b) 63 s t 1/2 (s) t 3/4 (s) A 0 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th N1 12 25 0.3807 90.9 47.1 0.118 0.256 0.012 N2 140 340 0.2513 5.72 0.35 0.210 0.032 0.002 N3 91 187 0.4653 7.62 (7.62076) 7.62 (7.62049) 1.329 0.525 0.012 N4 518 1140 0.5243 9.89 1.33 0.014 0.453 0.041 [a] 1.5×10 -5 M in ac etonitri le, 293 K. 4 UV/Vis Spe ct rosco py 67 4.1.3 Visible Light Irradiation Figure 4.7 Coloration/dec ol oration cycles for naphthopy ran N4 (m oni toring wavelength i s between 567 and 568 nm) in MeCN (c = 1.5×10 -5 M) at 293 K. T he grey regions: UV light i rradiation ( 365 nm, 110 m W/cm 2 ). The yel low region s: visible light irradiation ( 565 nm , 84 m W/ cm 2 ). Non- m arked regions present the per i ods when t he sam ple was in the dark. Table 4.3 Photo chrom ic properties in the procedu r e of visible light irra diation. A 1 , A 2 , A th , k 1 and k 2 are the fitting parameters from Equation 1 ; t 1/2 , t 3/4 and A 0 w ere obtained from experimental data. a To promote the de coloration process o f naphthopyran N4 , visible light irradiation was applied (Figure 4.7 ). When naphthop y ran N4 arrived at the P SS for about 80 s under UV irradiation, UV light irradiation was switched off, and 565 nm li ght irradiation w as switched on at the same time until naphthop y r an N4 arrived at the PSS under 565 nm light ir radiation, which is also th e same with the initial state. Then the sample was in the dark and no obvious chang e in absorbance w as observed. Th e visible light decoloration beh avior was investigated b y fitting it to the bi exponential decay ( Eq uation 1 ) (Fitting inform ation see Chapter 7.2). Upon irradiation with 565 nm light, the k 1 of N4 (34.9×10 -3 s -1 ) was accelerated to 3.5 times faster than that in the thermal back process and k 2 was increased 25-fold, to 34.9×10 -3 s - 1 . Correspondingly, the t 1/2 and t 3/4 of naphthopy ran 0 200 400 600 800 1000 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Absorbance Time/s N4 in MeCN 567-568 nm t 1/2 (s) t 3/4 (s) A 0 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th N4 25 43 0.5243 34.9 (34.9372) 34.9 (34.9369) 0.266 0.282 - 0.0003 [a] Visible l ight: 565 nm , 84 mW/ cm 2 , 1.5×10 -5 M in acetonitrile, 293 K . 4.1 UV/Vis St udies o f Two States Sy st em : Naphthopyrans N1 , N2 , N3 and N4 68 N4 were promoted to 25 and 43 s, respec tivel y (Table 4.3). After thre e circles of UV irradiation/ visible light irradiation, there w as no residual color or decomposition observed. 4.1.4 Solvent Effect on the Photoc hromic Properties 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 Absorbance Wavelength (nm) N3 in MeCN before UV N3 in MeCN after UV N3 in TCE before UV N3 in TCE after UV N3 in DCM before UV N3 in DCM after UV c) Figure 4.8 Abs orption spectra of a) N1 , b) N2 and c ) N3 in t he initial state and after UV irradiation i n different so lvents (UV lig ht: 340 nm, 12 m W/cm 2 , c = 1.5×10 -5 M, 293 K ). To investigate the solvent effect on the photoc hromic properties of n aphthop y rans, nonpolar solvents, tetrachloroethy lene (TCE) and dichlorom ethane (DCM), were also applied to the UV/Vis experiments. As ex hibited in Figure 4.8, all the absorption spectra of N1 , N2 and N3 in TCE have a blue shift with respect to that in ac etonitrile. B y contrast, the absorption s pectrum of N3 just has a small bathochromic shift (12 nm) in DCM com pared with that in acetonit rile. I n respect of the ring opening sp eed, N1 arrived at the PSS quicker than N3 , which is consis tent with t he behavior in MeCN. In contrast, N2 was im proved to the fastest naphthop y ran to arrive PSS in TCE from 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 0,6 Absorbance Wavelength (nm) N1 in MeCN before UV N1 in MeCN after UV N1 in TCE before UV N1 in TCE after UV a) 300 400 500 600 700 -0,05 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 Absorbance Wavelength (nm) N2 in MeCN before UV N2 in MeCN after UV N2 in TCE before UV N2 in TCE after UV b) 4 UV/Vis Spe ct rosco py 69 the slowest naphthop y ran to arrive PSS in MeCN, because of the effects on the formation of an acid dimer b y th e different solvents. [133] Besides that, the other naphthop y r ans, both N1 and N3 , arrived at the PSS slower in TCE than that in MeCN (Table 4.2 and 4.4). Table 4.4 Ab sorption p roperties of N1 , N2 and N3 in the pro cedure of UV i r radiat ion in TCE. a Table 4.5 Photo chrom ic properties of N1 , N2 and N3 in the procedu re of therm al back reaction. A 1 , A 2 , A th , k 1 and k 2 are the fitting par amete rs from Equation 1 ; t 1/2 , t 3/4 and A 0 were obt ained from experimental data. a Naphthopyra n λ m a x [nm ] (Closed form ) λ m a x [nm ] (Open form s) λ iso [nm ] t pss [s] N1 324 526 302 168 N2 323 553 306 80 N3 318, 352, 366 498 - b 214 N3 c 273, 296, 321, 351 , 364 573 296 100 [a] 1.5×10 -5 M in T CE, 293 K, UV light: 340 nm, 12 mW/cm 2 . [b] λ iso < 290 nm cannot be detected, because the U V cut- off of TCE is 290 nm . [c ] 1.5×1 0 -5 M in DCM . t 1/2 (s) t 3/4 (s) A 0 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th N1 347 700 0.4004 3.75 1.96 0.012 0.381 0.005 N2 101 219 0.2465 42.7 6.16 0.019 0.205 0.019 N3 1365 2192 0.2216 0.535 0.064 0.177 0.043 0.002 N3 b 129 269 0.4706 99 5.19 0.017 0.422 0.033 [a] 1.5×10 -5 M in TCE at 293 K. [b] 1.5×1 0 -5 M in DC M. 4.1 UV/Vis St udies o f Two States Sy st em : Naphthopyrans N1 , N2 , N3 and N4 70 Figure 4.9 Absorbance chang es monitored at λ max for a) naphthopyran N1 (m onitoring wavelength is between 5 38 and 539 nm ) in tetrach loroethy l ene, b) naphthopyran N2 (monitoring waveleng th is between 549 and 550 nm ) in tetrachloro ethylene, c) naphthopyran N3 (m onitoring waveleng th is between 494 and 495 nm ) in tetrachloroe thylene an d naphtho pyran N3 (m onit oring waveleng th is b et ween 570 and 57 1 nm) in DCM (c = 1.5×10 -5 M) at 293 K. The grey r egions : UV light irradiation (3 40 nm , 1 2 mW/ cm 2 ). Non- m arked regions presen t the periods whe n the sample w as in the da rk. The thermal r elaxation kinetics were cal cul ated fr om time-resolved absorbance changes at λ max , by fitting the ex perimental data to the biexponential deca y ( Equation 1 ) (Fi gure 4.9) (Fitting information se e Cha pter 7.2). For the thermal back relaxation pe riod, it wa s noted that the thermal back speed of both N1 ( k 1 = 3.75×10 -3 s -1 , k 2 = 1.96×10 -3 s -1 ) and N3 ( k 1 = 5.35×10 -4 s -1 , k 2 = 6.4×10 -5 s -1 ) in TCE were retarded compared to that in acetonitrile. W hile both k 1 (4.27×10 -2 s -1 ) and k 2 (6.16×10 -3 s -1 ) of N2 were lar ge r than that in acetonitrile, which can be explained b y th e differe nt ef fects on the formation of an acid dimer b y dif ferent so lvents, [133] while the photochromic prop erties of N2 varied with the dimer concentration. La st but not least, compared with the t 1/2 (1365 s) and t 3/ 4 (2192 s) of naphthop y r an with 8 -hy drox y m ethyl substituent, N3 , those 0 1000 2000 3000 4000 0.0 0.1 0.2 0.3 0.4 Absorbance Time (s) N1 in TCE 538-539 nm a) 0 500 1000 0.00 0.05 0.10 0.15 0.20 0.25 0.30 Absorbance Time (s) N2 in TCE 549-550 nm b) 0 500 1000 1500 2000 2500 0.00 0.05 0.10 0.15 0.20 0.25 Time (s) Absorbance N3 in TCE 494-495 nm c) 0 200 400 600 800 1000 1200 1400 1600 1800 0.0 0.1 0.2 0.3 0.4 0.5 Absorbance Time/s N3 in DCM 570-571 nm d) 4 UV/Vis Spe ct rosco py 71 of N1 (t 1/2 = 347 s, t 3/4 =700 s) were smaller (Table 4.5). Consequent ly, the t 1/2 and t 3/4 of naphthopyrans bea ring 8- substituent follow the order: Ester < Hydrox y meth y l, which has the same trend as in ac etonitrile. R egarding the photo chromic behavior of N3 in DCM, k 1 was promoted to 9.9×10 -2 s -1 , while k 2 (5.19×10 -3 s -1 ) was almost the same as that in acetonitrile. Notabl y , there ex ist decomposition in the coloration/decoloration c y cles of N2 in TCE and N3 in DCM (Figure 4.10). The decrease in absorbance of N2 in TCE and N3 in DCM at PSS of differe nt c yc les correlates with the increa se in remaining absorbance (residual color). Figure 4.10 Colo ration/decolo ration cycles f or a) naphthopy ran N2 (monitoring wavelength is between 549 and 550 nm) in TCE and b) naphthopyran N3 (m onitoring wav elength is betw een 570 and 571 nm) in DCM (c = 1.5×10 -5 M) at 293 K. T he grey regions: U V light : 340 nm , 1 2 m W/ cm 2 . Non-marked regions present the per i ods when the sam ple was in the d ark. In con clusion, a positive solvatochromism was o bserved for N1 , N2 and N3 , resulting from a hypsoc hromic shift with decreasing solvent polarit y (fo r the polarit y of sol vent, see C hapter 8 .3, Table 8.1). Besides that, the thermal back rates were redu ced in nonpolar s olvent (Tables 4.2 and 4.5), which is in agreement with the other reports about substituted 3 H -naphthopyrans. [47] 0 500 1000 1500 2000 2500 3000 3500 4000 0.00 0.05 0.10 0.15 0.20 0.25 N2 in TCE 549-550 nm Absorbance Time (s) a) 0 1000 2000 3000 4000 5000 6000 7000 0.0 0.1 0.2 0.3 0.4 0.5 Absorbance Time (s) N3 in DCM 570-571 nm b) 4.2 UV/Vis St udies o f Three State s Sy stem: Naphth opyrans N5 and N6 72 4. 2 UV /V is Studies of Three St a tes Sy stem : Naphthopyrans N 5 and N6 4.2.1 UV Irradiation Figure 4. 11 St ructures of N5 and N6 (be low) and absorption spectra chang es of a ) N5 and b ) N6 upon UV irradiation (U V light: 365 nm , 110 m W/ cm 2 , 1.5×10 -5 M in ace t onitrile, 2 93 K ). The structures and absorption spectra o f N5 and N6 are displa y ed in Figure 4.11. Before UV irradiation, the spectra o f N5 and N6 have a strong absorption at 261 and 250 nm, respectively. Upon UV irradiation, a new absorption centered at 427-429 nm emerged corresponding to the ring- 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Absorbance Wavelength (nm) 0 s 3 s 7 s a) 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 Wavelength (nm) 0 s 2 s 4 s 6 s 8 s Absorbance b) 4 UV/Vis Spe ct rosco py 73 open forms: TC and TT forms, and the absorption peaks around 250 and 261 nm were reduced. According to the data of Table 4.6, it is noted that the spec tra of both closed forms a nd open for ms of naphthopy ran N5 have a bathochromic shift with respect to that of N6 , which is due to the extended π conjugation of the carboxy lic acid ester group in naphthop yra n N5 as mentioned in chapter 4.1.1. Table 4.6 Ab sorption p roperties of N5 and N6 in the p r ocedure of UV irradiat i on. a 4.2.2 Therm al Back Re action As it is demonstrated in Figure 4.12, on ce UV light was switched off, the absorption around 427 nm of N5 and N6 r educed quickl y until about 0.04 of absorbance left. A fter a few minutes in the dark, no obvious change in the residual color was observed, and for that t he long lifetime of the TT forms are responsible. The time -resolved absorbance at λ max was monitored in Figure 4.13. In the procedure of thermal relaxation, t 1/2 and t 3/4 values were also mea sured for N5 and N6 . Upon UV light was switched off, t wo processes were obs erved in the s y s tem : TC→C F and TT→TC→CF . But the s peed of the p rocess TT →TC was by far sl ower than the speed of the TC→CF process. The T T form was almost not reduced du rin g the short thermal relaxation time. Thus, the absorbance curves during thermal bleaching w ere fitted to the first order d eca y ( Equation 2 ) [45,46] (Fitting inform ation see Chapter 7.2). 𝐴 t = 𝐴 1 𝑒 - k t + 𝐴 𝑡 ℎ (2) Where A (t) is the absorbance at the λ max , A 1 is the contributions to the initial absorbance A 0 , k is rate constant of fast component ( k TC→CF, thermal ), and A th is the residu al absorbance at the termination of testing time. Spectrokine tic data are exhibited in Table 4.7. Naphthopyra n λ m a x [nm ] (Closed form ) λ m a x [nm ] (Open form s) t pss [s] N5 261, 338 429 7 N6 250, 302, 316, 345 , 360 427 8 [a] 1.5×10 -5 M in acetonitrile, 293 K, UV light: 365 nm , 110 m W/cm 2 . 4.2 UV/Vis St udies o f Three State s Sy stem: Naphth opyrans N5 and N6 74 The k TC→CF, th ermal of N5 (0.634 s -1 ) was approximatel y 4.5 times as fast as that of N6 (0.141 s -1 ). That is wh y the t 1/2 (1.6 s) and t 3/4 (3.4 s) of N5 were smaller than those of N6 (t 1/2 = 4.8 s, t 3/4 = 9.7 s). Thus, the t 1 /2 and t 3/4 of naphthop y rans bearing an 8-substit uent were increa sed in the order: Ester < Ether meth yl. Correspondingl y , the thermal back speed was increased in the inverse order. Figure 4.12 Absorp tion spectra changes of a) N5 and b ) N6 during thermal relaxation started from PSS (UV) (1.5×10 -5 M in ace t onitrile, 293 K ). Table 4.7 Photo chrom ic properties of N5 and N6 in the pro cedure of th ermal back reaction . A th and k a r e the fitting parameters from Equation 2 ; t 1/2 , t 3/4 and A 0 w ere obtained from experimental data. a 300 400 500 600 700 0,0 0,2 0,4 0,6 0,8 1,0 Absorbance Wavelength (nm) 0 s (PSS UV ) 3 s 7 s 11 s initial state (CF) a) 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 Absorbance Wavelength (nm) Initial state (CF) 0 s (PSS UV ) 2 s 4 s 6 s 8 s 12 s 32 s b) t 1/2 (s) t 3/4 (s) A 0 k (s -1 ) A th N5 1.6 3.4 0.164 0.634 0.038 N6 4.8 9.7 0.231 0.141 0.041 [a] 1.5×10 -5 M in acetonitrile, 293 K. 4 UV/Vis Spe ct rosco py 75 Figure 4.13 Colora tion/de coloration cycles for a) naphthopy ran N5 ( m onitoring wavelength is between 427 and 428 nm) and b) naphthopyran N6 (monito ring wavelength is between 425 and 426 nm) in acetonitrile (c = 1.5×10 -5 M) at 293 K . T he grey regions: UV li ght irradiation (3 65 nm, 110 m W/ cm 2 ). Non - m arked r egions present t he periods when the sam pl e was in the dark. T he blue regions: visible light irradiation (420 nm, 73 m W/ cm 2 ). However, the spectra of N5 and N6 can return to the initi al state, when the thermal relaxation time was long enough. I f the sample of N5 was put in the dark for an additional hour (1 h) after the f ast total thermal relaxation of the TC form, the slow thermal relaxation of the TT form was observed (F igure 4.14). Therefore, k TT→TC, thermal of N5 was obtained by fitting the absorbance curve into monoexponential decay (Fitting information see C hapter 7.2). From the experimental data, it was revea led that the half life of the TT form is 1150 s , 720 times as long as tha t of the TC form. The thermal relaxation speed of the TC for m is about 900 times a s fast a s that of the TT form (6.8× 10 - 4 s -1 ) (Table 4.8). Accordingly, two diffe rent monoexponential decays w ere observed durin g the whole thermal relaxation period. Table 4.8 Photo chrom ic properties of N5 in the proce dure of therm al back reacti on. A th and k TT → TC , thermal are the fitting parameters from Equation 2 ; t 1/2, TT and A 0 were obtained fr om experim ental data. a 0 500 1000 1500 2000 2500 0.00 0.05 0.10 0.15 0.20 Absorbance Time (s) N5 in MeCN a) 0 50 100 150 200 250 300 0.00 0.05 0.10 0.15 0.20 0.25 N6 in MeCN 425 and 426 nm Absorbance Time/s b) t 1/2, TT (s) k TT → TC , thermal (s -1 ) A th N5 1150 6.8×10 -4 0.028 [a] 1.5×10 -5 M in acetonitri le, 293 K. 4.2 UV/Vis St udies o f Three State s Sy stem: Naphth opyrans N5 and N6 76 Figure 4.14 The tim e -resolv ed absorbance of N5 at λ m ax during long time thermal rel axation (black dots) and m onoexponential deca y fitting (red line) in MeCN ( c = 1.5×10 -5 M ) at 293 K. 4.2.3 Visible Light Irradiation After s everal minutesʹ thermal relaxation, there sti ll ex isted residual color in the absorption spectra of N5 and N6 , which disappeared rapidly unde r the irradiation with visible light. Upon irradiation with 420 nm light, the spectra of both N5 and N6 returned to the initial state (Figure 4.15), result ing from the faster spe ed of the proce dure TT→TC→ CF . There w ere onl y two isomers, TT and CF, in the s y stem of N5 and N6 after several minutes ’ thermal back reaction. Upon the visible light irradiation was switched on, the Vis-process, TT→TC→CF existed in the system. Wherein the Vis-process TT→TC was the r ate determinin g step because of the faster speed of the Vis -process TC→CF . Accordingly, the visi ble light bleaching ki netics were investigated from the time - resolved absorbance curve (Figure 4.13), b y fitting the ex perimental data to the mono exponential decay ( Eq uation 2 ) (Fitting information see C hapter 7.2). Spectrokinetic data are demonstrated in Table 4.9. 0 500 1000 1500 2000 2500 3000 0.030 0.032 0.034 0.036 0.038 Thermal relaxation of N5 Monoexponential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.02856 ± 0 .00127 A1 0.00986 ± 0 .00121 t1 1462.7059 5 ± 437.6495 1 Reduced Chi-Sqr 3.12452E-7 R-Square (C OD) 0.98254 Adj . R-Square 0.97089 4 UV/Vis Spe ct rosco py 77 Figure 4.15 The comparison of absorption spectra of a) N5 and b ) N6 : i ni tial (black ), after UV irradiat ion (red, 365 nm, 110 mW/cm 2 ), after therm al relaxation (blue) and after visible light i rradia tion (green, 420 nm , 73 mW/cm 2 ) (1.5×10 -5 M in aceton itrile, 293 K ). Table 4.9 Photo chrom ic properties of N5 and N6 in th e procedu re of visible light i rradiation. A th and k TT→TC, VIS are the fit ting par ameters from Equation 2 . a Upon irradiation with 420 nm light, the k TT→TC, VI S of N5 and N6 , the speed of Vis-process from TT to TC, were increased to 0.150 and 0.106 s -1 , respectively. Consequentl y, total dec oloration was achieved in 30 sec onds. Compared to the visi ble li ght bleaching speed o f N6 , k TT→TC, VIS of N5 is still faster. The tr end of the visi ble li ght promoted back reaction is consistent with the procedure of thermal back reaction. 400 450 500 550 0.0 0.1 0.2 Absorbance Wavelength (nm) N5 in MeCN PSS (365 nm for 7 s) After thermal back for 30 s After 420 nm irradiation for 20 s a) TT+TC TT 300 400 500 600 700 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 N6 in MeCN PSS (365 nm for 8 s) After thermal relaxation f or 32 s After 420 nm for 30 s Absorbance Wavelength (nm) b) k TT→TC, VIS (s -1 ) A th N5 0.150 0.023 N6 0.106 0.022 [a] Visible l ight: 420 nm , 73 mW/ cm 2 , 1.5×10 - 5 M in acet onitril e, 293 K. 4.3 UV/Vis St udies o f C-H Functiona lization Pr oduct N7 78 4. 3 UV /V is Studies of C-H F uncti onali zation Produc t N7 4.3.1 UV Irradiation Figure 4.16 Structu re (up) and absorp tion spectra ch anges (down) o f N7 after UV irradiation (365 nm , 110 m W/cm 2 ) in acetoni trile (c = 1.5×10 -5 M) a t 293 K. The absorption spectra of N7 is shown in Figure 4.16. Before UV irradiation, an absorption peak at 388 nm was obse rved in the spe ctra of N7 . Co mpared with N6 , th e bathochromic shift in the absorption spectra of N7 is due to the extended π c onjugation of the acr y lic ester subst ituent in the 6-position of the naphthopy ran. Upon continuous irradiation with 365 nm UV light at 293 K, a new visi ble absorption band centered at 459 nm em erged in the spectra of N7 . A fter just 2.5 seconds, N7 can reach a PS S (Table 4.10). According l y, the introduction of the acrylic ester substituent at 6-position brings about a bathochromic shift in the spe ctra o f both closed and open fo rms and an increase in th e speed of the ring ope ning reaction. 300 400 500 600 700 0,0 0,2 0,4 0,6 0,8 1,0 Absorbance Wavelength (nm) 0 s 0.5 s 1 s 2.5 s 459 nm 459 nm 4 UV/Vis Spe ct rosco py 79 Table 4.10 A bsorption p roperties of N6 and N7 in the procedur e of UV irradi ation. a 4.3.2 Therm al Back Re action Figure 4.17 Absorption spectra changes of N7 during ther m al relaxat ion in acetonitrile started fr om PSS (UV) (c = 1.5 ×10 -5 M) at 293 K. Once th e solution of naphthop yran N7 was in th e dark, th e absorption aro und 459 nm reduced quickly until 0.03 in the absorbance (Figure 4.17) , for which the long li fetime of the TT form is responsible. Therefore, totall y returning back to the initial spectrum was expected, if the thermal relaxation was long enough. The absorbance ch anges at λ max were monitored over time in Fig ure 4.18. The thermal blea ching kinetics we re fitted to the first order deca y ( Eq uation 2 ) (Fitting information see Chapter 7.2) . As it is exhibited in Table 4.11, the k TC→CF, thermal of N7 was 0.401 s − 1 , approximately 3 times as large a s that of N6 . Corresponding l y , the t 1/2 (1.8 s) and t 3/ 4 (3.5 s) of N7 were smaller. Moreover, the absorbance of N7 w as the same as that of N6 in the PSS under UV irradiation, but less residual colour was observed from the spe ctra of N7 . 300 400 500 600 700 0,0 0,2 0,4 0,6 0,8 Absorbance Wavelength (nm) Initial state (CF) 0 s (PSS UV ) 0.5 s 1 s 2 s 3 s 5 s 24 s Naphthopyra n λ m a x [nm ] (Closed form ) λ m a x [nm ] (Open form s) t pss [s] N6 250, 302, 316, 345 , 360 427 8 N7 244, 255, 331, 340 , 388 459 2.5 [a] 1.5×10 -5 M in acetonitrile, 293 K, UV light: 365 nm , 110 m W/cm 2 . 4.3 UV/Vis St udies o f C-H Functiona lization Pr oduct N7 80 Table 4.11 Phot ochrom i c prope rties of N6 and N7 i n the procedure of t hermal back reaction . A th and k TC→CF, thermal are the fitting par am eters from Equation 2 ; t 1/2 , t 3/4 and A 0 were obt ained from experimental data. a Figure 4.18 Absorbance changes monitored at λ max f or naphthopy ran N7 (monitoring wavelength is between 445 an d 446 nm) i n acetonitrile (c = 1.5×1 0 -5 M) at 293 K. The grey reg ions: U V light irradia tion (started a t 12 s and the PSS was reached after 2.5 s o f U V irradi ation. 365 nm, 110 mW/ cm 2 ). Non-m ar ked regions present the periods when the sample was in the dar k. The green regions: visible light irradiation (505 nm, 70 m W/ cm 2 ). 4.3.3 Visible Light Irradiation After s everal mi nutes in the dark, no obvious ch ange in the residual color of N7 was observed. Upon irradiation with 505 nm li ght, the spectra returned to the initial state in 25 second s (Fi gure 4.19). The visible li ght bl eaching kinetics were inv estigated from time -resolved absorption sp ectra (Figure 4.18), b y fitting the experimental d ata to t he monoexponential deca y ( Equation 2 ) (Fitting information see Chapter 7.2). Spectrokinetic data are depicted in Table 4.12. 0 50 100 150 200 0.00 0.05 0.10 0.15 0.20 0.25 N7 in MeCN 445-446 nm Absorbance Time/s t 1/2 (s) t 3/4 (s) A 0 k TC→CF, thermal (s -1 ) A th N6 4.8 9.1 0.2310 0.141 0.041 N7 1.8 3.5 0.2310 0.401 0.030 [a] 1.5×10 -5 M in acetonitrile, 293 K. 4 UV/Vis Spe ct rosco py 81 Under 505 nm light irradiation, the k TT→TC, VI S of N7 was 0.149 s -1 , which is 1.5 times as larg e as that of N6 in the Vis -proce ss. Notabl y, the residual colour of N7 did not disappea r under 420 nm light irradiation. For details, y ou can se e the in -situ NMR anal y sis for naph thopyra n N7 (Chapter 5.3). 300 400 500 600 700 0,0 0,2 0,4 0,6 0,8 1,0 initial state (CF) PSS (365 nm for 2.5 s) after thermal back fo r 100 s after 505 nm for 25 s Wavelength (nm) Absorbance Figure 4.19 T he compariso n of absorpt ion spec t ra of N7 in acetonitrile (c = 1.5×10 -5 M) at 293 K: initial (black), after UV irradiation ( red, 365 nm , 110 m W/ cm 2 ), after t herm al r elaxat ion (blue) and after visible light irradiat i on (g reen, 505 nm , 70 mW/cm 2 ) (derived from Figure 4.18). Table 4.12 Phot ochrom i c prope rties of N6 and N7 i n the procedure of v isible lig ht irradiation. A th and k TT→TC, VIS are the fit ting par ameters from Equation 2 . a k TT→TC, VIS (s -1 ) A th N6 b 0.106 0.021 N7 c 0.149 0.008 [a] 1.5×10 -5 M in acetonitrile, 293 K . [b ] V isible light: 420 nm , 73 mW/ cm 2 . [c ] Visible light : 505 nm , 70 m W/ cm 2 . 4.4 UV/Vis St udies o f Naphthopy rans N8 , N9 and N10 82 4. 4 UV /V is Studies of N a phthopyrans N8 , N9 and N10 Figure 4.20 S t ructures of naphthopy ran s N8 , N9 and N10 . Table 4.13 A bsorption pro per ties of N8 , N9 , and N10 . a The structures and abso rption spectra of N8 , N9 and N10 are described in Fig ure 4.20 and Figure 4.21, respectively. From the initi al state, it was il lustrated that the extended π conjugation with the alkyne substituent at 2-position lead to a bathochromic shift in the spectra of N9 with respect to the absorption spectra of N8 . The TMS substituent, which has an electron d onating effect, resulted in a further bathochromic shift in the spectra of N10 (Table 4.13). However, there were no n ew peaks observed in the spectra of N8 , N9 and N10 after s everal minutes of irradiation with UV light. The possible reason is the large steric substi tuent at 2 -position destabilizing the TC and TT forms (Figure 4.22). Therefore, the switch ing b etween closed and open forms is too fast to be detected under our experimental apparatus and conditions in hand. In fact, the s y nthesis of N8 and N10 we re r eported by the Rück -Braun group before [62] and later the photochromic properties of a sim ilar structural na phthopyran 2- Br - NP was reported b y th e Abe group (Figure 4.22 belo w). [63] The half life of the open fo rms of 2- Br - NP is 2.5 ms. While the machine we used for the ex periments in hand has a shortest time limitation with 100 ms to record Naphthopyra n N8 N9 N10 λ m a x [nm ] 265, 328 267, 365 272, 369 [a] 1.5×10 -5 M in acetonitrile, 293 K. 4 UV/Vis Spe ct rosco py 83 a single spectrum (for details, see Chapter 7.2). Accordin gl y , the photochr omic properties o f N8 , N9 and N10 were and are not available for the moment. Figure 4.21 Abs or ption sp ectra of a) N8 , b) N9 and c ) N10 in acetonitrile ( c = 1.5×10 -5 M) at 29 3 K. Figure 4.22 Pho t ochrom i c equi librium f or N8 , N9 and N10 (up ) and the struc t ure of naphthopy r an 2- Br - NP (down). 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) N8 in MeCN a) 300 400 500 600 700 800 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Absorbance Wavelength (nm) N9 in MeCN b) 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) N10 in MeCN c) 4.5 Discuss ion 84 4. 5 Di scussion 4.5.1 The Effect of 8-Substituent on the Photochromic Properties of Naphthopyran s From the former info rmation of the Chapters 4.1 and 4.2, it was revealed that, no matter in two states s y stem or three states s ystem, the ester group at 8 -positi on of na phthopyrans pla ys an important role in the photochromic properties: bathochromic shift for both open and closed forms, decrease in the time of arriving at the P SS and the acceleration in the rate of thermal relaxation. The bathochromic shift in the absorption spectra was obs erved, bec ause of the extended π conjugation with the ester group. For the reductio n in the time of ar riving at the P SS, in general, the π → π * transitions are c oncerned with the photochromic behavior of n aphthopyrans. Thus, th e extended π conjugation ca n promote the photochromic behavior. I n addition, the increase in the rate of ther mal re laxation can be ex plained b y the resonance elec tron-wit hdrawing effect of the ester g roup. As depicted in Figure 4.23 below, there ori ginally exist electron -poor centers at 3, 7 and 9 position. Meanwhile, the ester group at 8 position can withdraw the e lectrons f rom 3, 7 and 9 posi tion thereby destabiliz ing the open forms. Consequentl y , the speed of thermal relaxation is accelera ted. Figure 4.23 The resonance electron- withdrawing effect of the ester g roup at 8- position. 4 UV/Vis Spe ct rosco py 85 4.5.2 Comparison betwee n Two S tates System and Three States System Figure 4.24 The structu res of N1 and N5 . Naphthopy ran N1 and N5 are chosen as the examples to investigate the difference b etween two states s y st em and three st ates system (Figure 4.24) . For the absorption spect ra of the closed form, compounds have the s ame λ max at 261 nm. However, upon i rradiation with UV light, the electron donating pyrrolidine ring on the ary l rin g at 3 -position can be conjuga ted with the whole open form structure , correspon dingly inducing a ba thoc hromic shift in λ max of 163 nm. In the p eriod of thermal relaxation, the k TC→CF, thermal of N1 is about one seventh as fast as that of N5 .This phenomena is result ing from the ortho -chlorine group of the 3- ary l -substit uent, which hinders the re-formation of the CC form, but the C C form is necessar y for th e ring- closure reaction (Figure 4.25). [6 5] The influence ca n a lso be found from the cr ystal structure of naphthop y rans with similar ortho -substituents. [59] I nterestingl y , th e k TT→TC, thermal of N1 is increas ed, and is 70fold f aster than that of N5 , which is attributed to the para -pyrrolidine subst ituent. As a result, for N1 , the r atio of k 1 / k 2 is approx imately 2, while it is about 930 for N5 (Table 4.14). Accordingly, the thermal relaxation of N1 follows a biex ponential decay, whil e the thermal relaxation of N5 follows a fast monoexponenetial deca y (TC → CF) and another slow monoexponenetial deca y ( TT→TC→ CF ). Moreover, the latter step is faster under irr adiation with visi ble light. And that is why we can s ee three states in the time r esolved UV/Vis spectra of N5 . 4.5 Discuss ion 86 Table 4.14 Phot ochrom i c prope rties of N1 and N5 in t he procedure o f therm al back isom erization. a Figure 4.25 Pho t ochrom i c equi librium f or naphthopyr an N1 . 4.5.3 The Effect of 6-Substituent on Photochromic Properties of Naphthopyran From the information of Chapter 4.3, it was f ound that the introduction of an acr y li c ester substituent at 6-positi on, through a r emote C -H activation, had a great influence on the photochromic propertie s of the naphthop y r an. Except for the bathochromic shift in the absorption spectra, the the rmal relaxation speed and visible light bleaching speed w ere ac celerated. In order to investigate the reason, the resonance structures of N7 are shown in Fi gure 4.26. Because of the inductive electron-withdrawing effect of the este r group, the TC form of compound N7 is less stable than that of the naphthop y r an without the acr y li c ester substituent at 6-position. Hence the ring-closure reaction was promoted. λ m a x [nm] (Closed) λ m a x [nm] (Open) t 1/2 (s) t 3/4 (s) A 0 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) N1 261, 318 592 12 25 0.3807 90.9 b 47.1 b N5 261, 338 429 1.6 3.4 0.164 634 c 0.68 c [a] 1.5×10 -5 M in acetoni trile, 293 K. λ max , t 1/2 , t 3/4 and A 0 ar e obtained f rom experim ental data. [ b] k 1 and k 2 are t he fitting parameters from Equation 1 and data from Figure 4.5 - a and Table 4.2. [c] k 1 and k 2 are the fitting par ameters from Equation 2 . k 1 ( k TC → CF , ther mal ) from Figure 4.13 and T able 4.7, k 2 ( k TT → TC, thermal ) fr om Figure 4.14 and Table 4.8. 4 UV/Vis Spe ct rosco py 87 Figure 4.26 The resonance st ructure s of naph thopyran N7 . 4.5 Discuss ion 88 5 In -situ NMR A n aly s is 89 5 . In -situ NMR Ana lysis Low temp erature in -situ NMR experiments allow us to investigate how man y species are formed during the UV irradiation, thermal relaxation and visible light irradiation processes. We also c an evaluate the chan ge between the different fo rms directly so that the tra nsformation proc esse s among different forms will be clear. 5.1 In -s itu 1 H NM R Analysi s of Two States S y stem : Naphthopyran N1, N 3 and N4 5.1.1 Structural Identification of Different Isome rs of N1 The 1 H in -situ NMR spectra of naphthop y r an N1 is displayed in Fi gure 5.1. Upon irra diation with UV light, a new signal a t 9.02 ppm appea red, which belong ed to the H at 2 -position of the TC form acc ording to the literature. [ 49,51,55,1 3 4] The low field is due to the deshielding induced b y the C=O group. [36] At the sa me time, the sign als of H -17 and H-19 of the TC form appeared at 3.32 and 3.82 ppm, resp ectively. Th e signal of H -16 of the TC form appeared at 6.54 ppm. Thus, the conversion from CF to TC was de tected. Afte r 6 min UV irradiation, anothe r signa l was observed at 8.15 ppm, which was assigned to the 1 -position proton of the TT form. [48] Meanwhile, the H-5 of the TT fo rm appeared at 6.29 ppm. The reby th e transformation from T C to TT was det ected. After 35 min irr adiation, the s y stem arrived at the PSS. The ratio of different forms w as obtained as CF : TC : TT = 1 8 :7 1 :1 1. Moreover, based on the 1 H- 1 H COSY NMR experiment measured at PSS under UV irradiation (Figure 5.2), the sign als of other protons of th e TC form w ere also identified (Table 5.1). 5.1 In -situ 1 H NMR Analy s is of Two S tates System : N1 , N3 and N4 90 e) d) c) b) a) Figure 5.1 500 MHz 1 H NMR spectra of N1 a) before UV ir radiat ion, b) after 1 min of UV ir radiatio n, c ) after 6 m in of U V irradiatio n, d) afte r 20 m in of U V irradiati on and e ) a fter 65 m in of U V irr adiation a t the PSS i n CD 3 CN (c = 1×10 -2 M) at 238 K. (UV light: 365 nm , 0.45 mW/cm 2 , 5 00 MHz Bruker NMR spectrom eter) 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.4 3.6 3.8 4.0 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.4 3.6 3.8 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.4 3.6 3.8 ppm H7-CF H10-CF H9-CF H6-CF H11-CF H1+H14-CF H12+H13-CF H5-CF H15-CF H2-CF H16-CF H19-CF H17-CF 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.4 3.6 3.8 4.0 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.4 3.6 3.8 ppm H2-TC H1-TT H7-TC H9-TC H1-TC H10+H15-TC H16-TC H5-TC H5-TT H19-TC H17-TC 5 In -situ NMR A n aly s is 91 Figure 5.2 500 MHz 1 H- 1 H COSY NMR spectrum o f N1 at the PSS in CD 3 CN ( c = 1×10 -2 M) at 238 K . (UV light : 365 nm, 0.45 m W/cm 2 , 500 MHz Bruk er NMR spe ctrometer) Table 5.1 1 H NMR chemical shifts ( in ppm ) of differ ent isom er s of N1 obtain ed from in -situ NMR experim ents. a H1 H2 H5 H7 H9 H10 H15 H16 H17 H19 CF 7.38 6.61 7.22 8.47 7.99 8.06 7.10 6.40 3.15 3.87 TC 7.44 9.02 6.42 8.00 7.74 7.27 7.27 6.54 3.32 3.82 TT 8.15 6.29 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm , 0.45 mW/cm 2 . 5.1 In -situ 1 H NMR Analy s is of Two S tates System : N1 , N3 and N4 92 5.1.2 Structural Identification of Different Isome rs of N3 e) d) c) b) a) Figure 5.3 500 MHz 1 H NMR spectra of N3 a) before UV ir radiat ion, b) after 1 min of UV ir radiatio n, c ) after 6 min of UV irradiation, d) after 40 m i n of UV irradiation and e) after 115 m in of UV i rradiation a t the PSS in CD 3 C N ( c = 1×10 -2 M) at 238 K. ( U V light: 365 nm, 0.45 mW/cm 2 , 500 MHz Bruker NMR spectrom eter) 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.5 4.0 4.5 ppm H10-CF H11-CF H6+H7-CF H9-CF H1+H14-CF H12+H13-CF H5+H15-CF H2-CF H16-CF H19-CF H20-CF H17-CF 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.5 4.0 4.5 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.5 4.0 4.5 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.5 4.0 4.5 ppm 6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 ppm 3.5 4.0 4.5 ppm H2-TC H1-TT H6-TC H2-TT H1-TC H15-TC H16-TC H5-TC H5-TT H19-TT H19-TC H20-TT H20-TC H17-TC 5 In -situ NMR A n aly s is 93 Figure 5.4 500 MHz 1 H- 1 H COSY NMR spectrum o f N3 at t he PSS in CD 3 CN (c = 1×10 -2 M) at 238 K . (UV light : 365 nm, 0.45 m W/cm 2 , 500 MHz Bruk er NMR spe ctrometer) Table 5.2 1 H NMR chemical shifts ( in ppm ) of differ ent isom er s of N3 obt ained from in -situ NMR experim ents. a H1 H2 H5 H6 H11 H15 H1 6 H1 7 H1 9 H20 CF 7.38 6.59 7.13 7.70 7.87 7.11 6.41 3.16 4.64 3.95 TC 7.35 8.92 6.36 7.52 - 7.24 6.54 3.30 4.51 3.91 TT 8.02 7.44 6.22 - 4.61 4.04 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm , 0.45 mW/cm 2 . 5.1 In -situ 1 H NMR Analy s is of Two S tates System : N1 , N3 and N4 94 As exhibited in Figure 5 .3 (a), the signals of all the protons of N3 have been identified in the spectrum. Upon irradiation with UV light, the TC form was converte d fro m closed form (CF). A new si gnal assigned to th e H -2 of th e TC form a ppeared at 8.92 ppm. At the same time, the signals of H -5 a nd H- 16 of the TC form appea red at 6.36 and 6.54 ppm, respectively. The sig nals of H- 17 and H-19 of the TC form were detected at 3.30 and 4.51 ppm, respectively . Aft er 6 min UV irradiation, the sig nals of the TT form w ere also observed. The si gnal at 6.22 ppm was assigned to the 5-position proton of t he TT fo rm. The si gnal at 8.02 ppm was assigned t o the 1-position proton of TT form. Thus, the tra nsformation from TC to TT was detec ted. After 115 min irradiation with UV light, the s ignals o f t he CF form w ere almost disappeared, and the s y stem arrived at the PSS. The ratio of the differe nt forms is CF : T C : TT = 5 :80 :1 5. I n addition, the sig nals of other protons of TC and TT forms (T able 5.2) can be identified from the 1 H- 1 H C OSY NMR experiment measured at the PSS under U V irradiation (Figure 5.4). 5.1.3 Structural Identification of Different Isome rs of N4 The in -situ 1 H NMR spe ctra of N4 is shown in Figure 5.5. Th e signals of all the protons of N4 have been identifi ed in the spec trum of Figure 5. 5 (a). Upon UV ir radiation, three new doublet signals app eared at 8.95, 6.36 and 3.31 ppm. The former one signal b elong ed to H-2 o f the TC form. The latter two si gnals were assi gned to H -5 and H-17 o f the TC fo rm, respec tivel y . A fter 6 min UV irradi ation, the signals of th e TT form were obse rved due to conversion from th e TC form to the TT form. The sig nal which appeared at 8.11 ppm wa s assigned to the 1-position proton (H -1) of th e TT form. A nd the si gnal a t 6.24 pp m belong ed to th e 5 -position proton (H -5) of the TT form. After 35 min UV irradiation, the s y st em of N4 arrived at the PSS , and the ratio of differe nt forms is CF : TC : TT = 13:73:14. I n addition, H-21 and H-22 of the TC form were identified at 1.27 and 1.32 ppm, respectively (Table 5.3). 5 In -situ NMR A n aly s is 95 d) c) b) a) Figure 5.5 500 MHz 1 H NMR spectra of N4 a) before UV ir radiat ion, b) after 1 min of UV ir radiation, c ) after 4 min o f UV irrad iation and d) afte r 35 min of U V irradiation at t he PSS in CD 3 CN (c = 1×10 -2 M) a t 238 K. (U V light: 365 nm , 3.86 mW/cm 2 , 500 MHz Bruker NMR spect rometer) 5.1 In -situ 1 H NMR Analy s is of Two S tates System : N1 , N3 and N4 96 Table 5.3 1 H NMR chemical shifts ( in ppm ) of differ ent isom er s of N4 obt ained from in -situ NMR experim ents. a 5.1.4 Kinetic Analysis of N1, N3 and N4 during Different P ro cesses When we followed the H-7 (8.47 ppm) of CF, H -2 (9.02 ppm) of TC and H-5 (6.29 ppm) of TT under UV irr adiation and in the dark, the evolution of different isomers of N1 was obtained in Fig ure 5.6 ( a). The evolution of different isomers of N3 was achieved in Figure 5.6 (b) b y following the H-11 (7.87 ppm) of CF, H-2 (8.92 ppm) of TC and H-5 (6.22 ppm) of T T. As exhibited in the Fi gure 5.6, upon irradiation with UV li ght, the TC form was converted from the CF form, meanwhile, the TT form was converted from the TC form. When the sample was in the da rk, the TC form can be c onverted fr om the TT form slowly, and the C F form we re converted f rom the TC form quickly . The kinetics of CF → TC, TC → TT, TC → CF and TT → TC were fitted to the first order reac tion ( Equation 3 ). c t = 𝐴 1 𝑒 − 𝑘𝜏 + c 𝑡 ℎ (3) c t is the concentration of CF, TC or TT, k is the rate constant. Spectrokinetic data are d emonstrated in Table 5.4. Under UV ir radiation, t he speed of N1 in the process CF→TC ( k 3 ) a nd TC→TT ( k 4 ) were 9.98×10 − 4 s − 1 and 8.36× 10 -4 s -1 , respectively, which were simil ar with that of N3 ( k 3 = 1.04×10 − 3 s − 1 , k 4 = 1.04×10 -3 s -1 ). For the thermal back period, k 5 of N1 (5.02×10 -4 s -1 ) wa s approximately 50 ti mes as fast as that of N3 (9.6 9×10 -6 s -1 ). I n the proces s of TT → TC , k 6 of N1 (2×10 -4 s -1 ) was about 33 -fold fast er than that of N3 (6.09×10 -6 s -1 ). According l y , the trend was H1 H2 H5 H10 H1 6 H17 H21 H22 CF - 6.65 7.18 8.07 6.45 3.20 1.32 1.38 TC - 8.95 6.36 - 6.55 3.31 1.27 1.32 TT 8.11 - 6.24 - 6.50 3.28 - - [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm , 3.86 mW/cm 2 . 5 In -situ NMR A n aly s is 97 consistent with the result of room temperature UV/Vis experiments (se e Chapter 4.1): the thermal relaxation speed was acce lerated b y the ester group at 8 -position of the naphthop y r an. Furthermore, the ratio of k 5 / k 6 ( k 5 / k 6 = 2.5) of N1 was r evealed to have a similar re lationship with k 1 / k 2 ( k 1 / k 2 = 2) of N1 in the room temperature UV/Vis exper iments. Compared to the ratio of k 1 / k 2 ( k 1 / k 2 = 1) of N3 in the room temperature UV/Vis ex periments, the ratio of k 5 / k 6 ( k 5 / k 6 = 1.5) of N3 was als o similar. Figure 5.6 Ev ol ution of CF , T C and TT of a) N1 and b) N3 in CD 3 CN (c = 1×1 0 -2 M) at 238 K. The grey region sig nals the period s when the sam ple was irrad iated with U V light (365 nm, 0.45 m W/cm 2 ); non- m arked region presents th e periods whe n t he sam ple was in the da rk. 0 2000 4000 6000 8000 10000 0 20 40 60 80 100 CF TC TT C/10 -4 M Time/s a) 0 2000 4000 6000 8000 10000 12000 14000 16000 0 20 40 60 80 100 CF TC TT C/10 -4 M Time/s b) 5.1 In -situ 1 H NMR Analy s is of Two S tates System : N1 , N3 and N4 98 Table 5.4 Rate constants of N1 and N3 from in -situ NMR. a The evolution of different isomers of N4 upon UV irradiation was acquired in Figure 5.7, if the H- 10 (8.07 ppm) of CF, H- 2 (8.95 ppm) of TC and H- 1 (8.11 ppm) of TT were followed. The kinetics of different processes were fitted to the first order rea ction ( Equation 3 ). Upon UV irradiation, the TC form was converted from the CF form with a rate constant of 1.65×10 − 3 s − 1 . At the same time, the TT form was converted from the TC form with a rate constant of 1.48×10 - 3 s -1 . Compared with N1 and N3 , the ring openin g reaction of N4 was faster due to the higher pow er of the UV light (3.86 mW/cm 2 ). Considering the slow th ermal back reaction from the data of room temperature UV/Vis experiments (see Chapter 4.1), visi ble light ir radiation wa s applied for promotion of the TT→T C process . Once the s ystem arrived the PSS, UV light was switched off, and visi ble light was switched on. The k 5 and k 6 of N4 were promoted to 1.37×10 -4 s - 1 and 1.16×10 - 4 s -1 , respectivel y , approx imately 14 and 19 ti mes faster than that of N3 , while the the rmal b ack speed of N4 w as similar with that of N3 in the room temperature U V/Vis ex periments. I n addition, the ratio of k 5 / k 6 ( k 5 / k 6 = 1.2) of N4 w as similar with k 1 / k 2 ( k 1 / k 2 = 1) of N4 under irradiation with visible light in the room temperature UV/Vis experiments. k 3 (s -1 ) k 4 (s -1 ) k 5 (s -1 ) k 6 (s -1 ) Ratio ´N1 9.98×10 -4 8.36×10 -4 5.02×10 -4 2.00×10 -4 CF : TC : TT = 18:71:11 N3 1.04×10 -3 1.04×10 -3 9.69×10 -6 6.09×10 -6 CF : TC : TT = 5: 80:15 [a] 1×10 -2 M in CD 3 CN at 238 K. UV light : 365 nm , 0.45 mW/cm 2 . 5 In -situ NMR A n aly s is 99 Figure 5. 7 Ev olut ion of CF , TC and TT of N4 i n C D 3 CN (c = 1×10 -2 M) at 238 K . T he g rey region s i gnals the periods when the sam p le was irradiated with UV light (365 nm , 3.86 mW/cm 2 ); t he yellow reg ion signals the per iods when t he sam pl e was irrad i ated w ith visible lig ht (565 nm , 3.20 mW/cm 2 ). Table 5.5 Rate constants o f N4 from in -s itu NMR. a 0 2000 4000 6000 8000 10000 12000 14000 0 20 40 60 80 100 CF TC TT Time/s C/10 -4 M k 3 (s -1 ) k 4 (s -1 ) k 5 (s -1 ) k 6 (s -1 ) Ratio ´N4 1.65×10 -3 1.48×10 -3 1.37×10 -4 1.16×10 -4 CF : TC : TT = 13:73:14 [a] 1×10 -2 M in CD 3 CN at 238 K. U V light : 365 nm , 3.86 mW/cm 2 . Visibl e light : 565 nm, 3.20 m W/cm 2 . 5.2 In -situ 19 F N MR Analysis of Th ree Sta t es System : Naphthopy rans N5 a nd N6 100 5.2 In -s itu 19 F N MR analysis of Thr ee State s System: Napht ho pyran N 5 and N6 The 19 F NMR spectra have less peaks than the 1 H NMR spectra to be investigated and the 19 F nucleus is also easily observable, because of its 100% natural abundance, ½ spin and similarl y high sensitivit y with 1 H nucleus. [36] Since the relation betwee n 19 F NMR spectra and 1 H NMR spectra ha ve been invest igated b y the literatures [18,36,48,49] the in -situ 1 H NMR spectra are not necessary for the exploration of naphthop y rans N5 , N6 and N7 an y more. The in -situ 19 F NMR spectra of N5 are depicted in Fig u re 5.8. The si gnals of fluorine o f different isom ers are easil y identified. Before U V i rradiation, the signal of N5 was loc ated at −115.84 ppm. Upon UV irradiation, two new signals we re observed at −11 2.42 ppm and −113.13 ppm, re spectively, which were assigned to the TC form. After 3 min UV irr adiation, the signals of th e TT form app eared at −112.64 and −112.75 ppm, respec tivel y . Particular ly , the si gnal of an alleny l -naphthol compound (AP) was detected at −116.21 ppm, signals which were also observed from other naphthopyrans. [17,18,36, 48,135,136] After 32 min o f UV irradiation, th e s y stem of N5 arrived at the PSS with a ratio of CF : TC : TT : AP = 1 0 :6 0:8: 22. Similar performance was also observed in the evolution of naphthopyran N6 . After about 30 min irradiation with UV light, an equilibrium was established in the s ystem of N6 with a ratio of CF : TC : TT : AP = 15:72:5:8. The c hemical shifts of different isomers of N5 and N6 are presented in Table 5.6. Table 5.6 19 F NMR chem ical shifts (i n ppm ) of differe nt isom ers of N5 and N6 ob t ained from in -si tu NMR experim ent s. a N5 N6 CF TC TT AP CF TC TT AP F − 115.84 − 112.42 − 113.13 − 112.64 − 112.75 − 116.21 − 116.06 − 113.00 − 113.54 − 113.15 − 116.28 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm, 3.86 m W/cm 2 . 5 In -situ NMR A n aly s is 101 e) d) c) b) a) Figure 5.8 470 MHz 19 F NMR spectra of N5 a) before UV irradiation, b) after 1 m i n of UV irradiation, c ) after 3 m in of U V irradiatio n, d) afte r 10 m in of U V irradiati on and e ) a fter 32 m in of U V irr adiation a t the PSS in CD 3 CN (c = 1×10 -2 M) a t 238 K. (365 nm , 3.86 m W/cm 2 , 500 MHz Bruker NMR spectrom eter ) -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm CF -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm TC TC -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm AP TT -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm 5.2 In -situ 19 F N MR Analysis of Th ree Sta t es System : Naphthopy rans N5 a nd N6 102 When the fluorine signals of CF, TC, TT and AP w ere follow ed, the evolution of diffe rent isomers of N5 were obtained in Fig u re 5.9 (a). The kin etics of all the transformation processes between any two related isomers were fitted to the first or der reac tion ( Equation 3 ) (Table 5.8). Upon U V irradiation, the CF form wa s converted into the TC form with a r ate c onsta nt of k 3 = 5.38×10 -3 s -1 , meanwhile, TT and AP forms were converted from the TC form with rate constants of k 4 = 3.78×10 -3 s - 1 and k 7 = 4.92×10 − 4 s − 1 , respectively. At the same time, b y p roduct was observed at − 115.5 ppm after 32 min UV irradiation (Figure 5.8, e). When the sample was in the da rk, the CF form was increased, TC and AP forms started to be decreased, because of the two following processes: TC→CF ( k 8 = 9.59×10 -4 s -1 ) and AP→ TC ( k 10 = 8.00×10 -4 s -1 ). S urprisingly, TT form was increased when the sample was in the dark, which differed from room temperature UV/Vis experiments. Similar phenomenon was observed for chromene and the y think it is resulting from the process TC→TT , [136] although the process AP →TT is also a possible reason. The rate constant of process TC→TT in th e dark is k 9 = 1.54×10 -4 s -1 . I t is worth notin g that , if the UV li ght was switched on aga in, the TT form was converted into the TC form until arriving at the same ratio as obtained under UV irradiation in the beginning. In addition, after 396 s UV irradiation, the CF form content was decreased to (9×10 -4 M) and did not change an y more, while the content of the TC form was increase d to (6.2×10 - 3 M) for the fir st 396 s UV irradiation and re duced to (5.5×10 − 3 M) until the PSS was reached in th e follo wing 924 s of UV i rradiation. At the same time, AP content was increasing until the PSS was reached in the whole 1320 s U V irradiation process . That is an evidence that the AP form wa s converted from the TC form. The evolution of differen t isomers of N6 is presented in Fig ure 5.9 (b). Upon UV irradiation, both process es CF→TC and TC→TT were detected with rate constants of k 3 = 2.81×10 -3 s - 1 and k 4 = 1.55×10 -3 s -1 , respectively, which are slower than the process es observed for N5 . But the transformation from TC to AP ( k 7 = 2.35×10 -3 s -1 ) is faster than the process of N5 . W hen the UV light was switched off, the TC form o f N6 was con verted into the CF form with a slowe r spe ed ( k 8 = 3.25×10 -4 s -1 ) than that of N5 , which has a sa me trend as in the room temperature UV/Vis experiments for N5 and N6 . Howev er, the re is no clear change for the TT form during the whole thermal ba ck p eriod, which is diff erent from na phthopyran N5 . T he pro cess: AP→TC ( k 10 = 8.00×10 -4 s -1 ) is faster th an that of N5 . After about 2 h in the dark, no AP form was d etected, and a new e quilibrium was established in the s ystem of N6 with a ratio of C F : TC : TT = 87:6:7. Upon irradiation with 420 nm l ight, the TC content was increased firstl y , and th en was reduced due to 5 In -situ NMR A n aly s is 103 t he concurrent thre e processes: TC→CF, TT→TC and TC→AP. The AP form appeared again, and all the TT form disappeared. A new equilibrium was observed with a ra tio of CF : TC : AP = 92:3:5. When visi ble light was switched off, TC was conve rted from all the AP fo rm. A new thermal equilibrium was reached between CF and TC (CF : TC = 94:6 ). Figure 5.9 Evolution of CF, T C, TT and AP of a) N5 and b) N6 in CD 3 C N (c = 1×10 -2 M) at 238 K. T he grey regions: UV light irradiation (365 nm, 3.86 mW/cm 2 ); t he blue region: visible light irradiat ion (420 nm , 8.10 mW/cm 2 ); non-mark ed regions: the sam ple was in the dark . 0 2000 4000 6000 8000 0 20 40 60 80 100 Time/s C/ 10 -4 M CF TC TT AP a) 0 2000 4000 6000 8000 10000 12000 14000 0 20 40 60 80 100 CF TC TT AP Time/s C/10 -4 M b) 5.2 In -situ 19 F N MR Analysis of Th ree Sta t es System : Naphthopy rans N5 a nd N6 104 Table 5.7 The r atios am ong different isom er s of N5 a nd N6 in the PSS under UV i rradiat ion. a Table 5.8 Rate constants of N5 and N6 from in -situ NMR. a Naphthopyra n Ratio N5 CF : TC : TT : AP = 10 :6 0: 8:22 N6 CF : TC : TT : AP = 15 :72:5:8 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm , 3.86 mW/cm 2 k 3 (10 -3 s -1 ) k 4 (10 -3 s -1 ) k 7 (10 -3 s -1 ) k 8 (10 -3 s -1 ) k 9 (10 -3 s -1 ) k 10 (10 -3 s -1 ) k 11 (10 -3 s -1 ) k 12 (10 -3 s -1 ) k 13 (10 -3 s -1 ) N5 5.38 3.78 0.492 0.959 0.154 0.800 - c - c - c N6 b 2.81 1.55 2.35 0.325 - 1.82 1.89 6.37 4.32 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm, 3.86 m W/cm 2 [b ] Visible light: 420 nm, 8.10 m W/ cm 2 . [c ] For com pound N5, irradi ation with visible l ight was not i nvesti gated. 5 In -situ NMR A n aly s is 105 5.3 Investi gation of Visible Li ght Wavelength Influence on PSS Vis of N 7 by In - situ 19 F NM R analysis Table 5.9 19 F NMR chem ical shifts (i n ppm ) of differe nt isom ers of N7 obtain ed from in -situ NMR experim ents. a The chemic al shifts of differe nt isomers of N7 a re reported in Table 5. 9 ( for NMR spectra, see Chapter 8.4). If w e followed the F signals of CF, TC, TT a nd AP, the e volution of differe nt forms of N7 was ac hieved as presented in Fi gure 5.10. Upon UV irr adiation, the CF content w as decreased, the content of the other three forms: TC, TT and AP, we re increased. Afte r about 24 min irradiation, the system arrived at the P SS with a ratio of CF : TC : TT : A P = 32:53:13:2. W hen the sample was in the dark, two processes, TC → CF and AP →TC were d etected and the TT form did not change, which is the same as compound N6 and different from compound N5 . After 45 N7 CF TC TT AP F − 115.84 − 112.81 − 113.38 − 113.00 − 116.09 [a] 1×10 -2 M in CD 3 CN at 238 K . UV light: 365 nm , 3.86 mW/cm 2 . 5.3 Investiga tion of V isible Light W avelength Infl uence on PS S Vis of N7 by In -situ 19 F NMR a n aly si s 106 min in the dark, one equilibrium w as found with a ratio of CF : TC : TT = 80:6:14. However, when the sample was irra diated with 420 nm light, the T T form were conve rted to the CF for m until the content of (9×10 -4 M) , and the process C F→TC was observed, which is different from the compound N6 . After 2 mi n irra diation with 420 n m light, a ratio of CF : TC : TT : A P = 5 3:34:9:4 was established. Further more, the total disappearance of TT form w ere not observed under the irradiation with 455 nm, too . The process CF→T C was also detected ( Figure 5.10 blue and Table 5.10). This phenomenon is result ing from the abs orption band at 375-450 nm of the closed form of N7 . Therefore, the cleavage of the C-O bond can be in duced b y the ir radiation with both 420 nm and 455 nm light. Finall y, after 6 min 505 nm irradiation, all the TT form w as converted to the TC form, and the TC form w as converted to the CF form with an equilibrium of CF : TC : AP = 92:4:4, established under the irradiation wit h 505 nm light. Figure 5.10 Evolut ion of C F, TC, TT and AP o f N7 in CD 3 CN (c = 1×10 -2 M) at 238 K. The g r ey reg ions : UV light irradiati on (365 nm, 3.86 mW/cm 2 ); the blue region: visible li ght irradiation (420 nm, 8.10 m W/cm 2 ); the light blue r eg i on: visible light irradiat ion (455 nm, 4.30 m W/cm 2 ) ; t he green region: visible light irradiat i on (505 nm , 2.37 m W/cm 2 ); non-m ar ked reg ions: the sample was i n t he dark. 0 2000 4000 6000 8000 10000 0 20 40 60 80 100 CF TC TT AP Time/s C/10 -4 M 5 In -situ NMR A n aly s is 107 The kinetics of all the transformation processes between an y two related isomers of N7 can be fitted to the first order reaction ( Eq uation 3 ) (Table 5.10). B y comparison of the photochromic behavior b etwee n N6 and N7 (T able 5.8 and Table 5.10), it was rev ealed that k 3 of N7 (3.93×10 − 3 s − 1 ) is faster than that of N6 (2.81×10 − 3 s − 1 ), that is why naphthop y r an N7 can a rrive a t the PSS quicker. This trend is also in agreement with the photochromic performance in the UV/Vis experiments. The speeds of process TC →T T are almost the same for N6 and N7 : 1.56×10 − 3 s − 1 . But AP of N6 can b e converted from TC faster than that of N7 . In the thermal re laxation period, the speed from TC to CF of N7 ( k 8 = 1.10×10 − 3 s − 1 ) is appro x imately 3 time as fast as that of N6 ( k 8 = 3.25× 10 − 2 s − 1 ), w hich is in accorda nce with the data fr om room temperature UV/Vis experiments. I n the visi ble light irradiation peri od, under 505 nm irradi ation, the reconversion speed of k 20 (2.11× 10 − 3 s − 1 ) and k 21 (12.97×10 − 3 s − 1 ) are faster than k 11 a nd k 12 of N6 , which has the same trend as in the room temperature UV/Vis e xperiments. At last, in the procedure of different visible light irradiation of N7 , it was indicated tha t the longer the wavelength of visi ble light, the faster is tr ansformation f rom TT to TC. The rate constants are: 420 nm: 2.80×10 − 3 s − 1 , 455 nm: 7.92×10 − 3 s − 1 and 505 nm : 12.97×10 − 3 s − 1 . 5.3 Investiga tion of V isible Light W avelength Infl uence on PS S Vis of N7 by In -situ 19 F NMR a n aly si s 108 Table 5.10 Rat e constant s and the r atio in the PSS un der UV i rradiation o f N7 from in - situ NMR. a k 3 (10 -3 s -1 ) k 4 (10 -3 s -1 ) k 7 (10 -3 s -1 ) k 8 (10 -3 s -1 ) k 10 (10 -3 s -1 ) k 14 (10 -3 s -1 ) k 15 (10 -3 s -1 ) k 16 (10 -3 s -1 ) k 17 (10 -3 s -1 ) 3.93 1.56 1.92 1.10 2.02 3.29 2.80 3.50 2.31 k 18 (10 -3 s -1 ) k 19 (10 -3 s -1 ) k 20 (10 -3 s -1 ) k 21 (10 -3 s -1 ) k 22 (10 -3 s -1 ) Ratio 7.92 2.00 2.11 12.97 4.47 CF : TC : TT : AP = 32 :53:13:2 [a] 1×10 -2 M in CD 3 CN at 238 K. UV lig ht: 365 nm , 3.86 mW/cm 2 . Visibl e light : 420 nm, 8.10 m W/cm 2 ; 455 nm , 4.30 m W/cm 2 ; 505 nm , 2.37 mW/cm 2 . 5 In -situ NMR A n aly s is 109 5.4 In -s itu 1 H NM R analysis of N aphthopyr ans N8 , N9 and N10 a) b) Figure 5.11 500 MHz 1 H NMR spectra of N10 a) bef ore U V irradiation and b) after 20 min of UV irradiation in CD 3 CN (c = 1×10 -2 M) at 238 K. (UV lig ht: 365 nm, 3.86 mW/cm 2 , 500 MHz Bruker NMR spectrom eter) Because of the ex tremely fa st th ermal relaxation speed of naphthop yran N8 , N9 and N10 , normal room temperature UV/Vis experiments are not effective in the detection of the open forms (Chapter 4.4). Therefore, N8 , N9 and N10 were monitored b y low temperature in -situ NMR experiments. As shown in Figure 5.11, after 20 min UV irradiation at 238 K, no new si gnal was detected in the spectra of N10 . And the same phenomena were also observe d in the spectra of N8 and N9 . Then lower temperature experiments at 213 K were performed fo r N8 a nd N9 (Figure 5.12). Unfortunately, new signals were sti ll not observed in toluene- d 8 solution at 213 K, and 213 K is the lowest temperature for long time in -situ NMR measurements in the Institute. Hence the photochromic data of N8 , N9 and N10 are not ava ilable at prese nt. 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 ppm 4 3 2 1 ppm 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 ppm 4 3 2 1 ppm 5.4 In -situ 1 H NMR Analy s is of Na phthopy rans N8 , N9 and N10 110 a) b) c) d) Figure 5.12 500 MHz 1 H NMR spectra of a) N8 befo re UV irradiation, b) N8 after 20 min of UV irradiat ion, c ) N9 before UV irradiatio n and d ) N9 af ter 20 min of UV irradiation in toluene- d 8 ( c = 1×10 -2 M) at 2 13 K. (UV light : 365 nm, 3.86 mW/cm 2 , B ruker NMR spectrom eter) 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 ppm 3.5 ppm 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 ppm 3.4 3.6 3.8 ppm 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 ppm 3.0 3.5 ppm 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 ppm 3.0 3.5 ppm 5 In -situ NMR A n aly s is 111 5.5 Discussi on 5.5.1 The Different Pe rf ormance b etween Two States System and Three Stat es System during the Low Temperature in -sit u NMR Measurements Comparing the photochromic behaviors of two states s ystem with three stat es s y stem naphthopyrans, N1 (Table 5.4) and N5 (Table 5.7), in the low tempera ture in -situ NMR experiments, it was foun d that TT →T C process was observed in the two states s y stem N1 durin g the thermal relax ation. In contrast, TC →T T proc ess was observed in the t hree states s ystem N5 during the low temperatu re therm al relaxation. In order to explain the phenomenon, the proposed energy dia gram is illustrated in F i gure 5.14, in which the AP form is not inv olved, because the AP form was not detected in the two states sy stem. Pr esumably , the activation energ y (ΔG 5 ) between TT form and tra nsition state 3 is too large to reach in the three states sy stem at 238K. Meanwhile, the energ y barrier between TC form and transition state 3 is low enoug h to climb. As a result, onl y the TC →T T process was observed. How ever, when th e temperature rose t o 293 K, the TT form had enou gh energ y to climb to the transition state 3. Thus, all the processes TC →T T, TT →T C and TC → CF exist ed in the s y stem. Due to the decrea sing TC form, the TT →T C process was observed. Therefore, the rate const ant ( k TT→T C, th ermal ) of the TT →T C process was detected durin g thermal relaxation in the room temperature UV/Vis ex periments (Table 4.12). Nevertheless, k TC→CF , thermal of N5 is far larger than k TT → TC, thermal of N5 , beca use ΔG 5 is larger than ΔG 3 . As for the two states sy st em N1 , in the period of therma l relaxation, the low energy barrier (ΔG 6 ) between TT form and transition state 3 make it possible for process TT →T C at both 293 K and 238 K. In addition, as mentioned in Chapter 4.5.2, the ortho -chlorine group of aryl is a hindrance to the re -formation of CC form (Fi gure 5.13). [65] So the ener gy b arrier (ΔG 2 ) between TC form and transition state 2 is higher than that of three state s s y stem N5 (ΔG 1 ). That is why the rate constant of process TC → CF ( k 1 ) of N5 is larg er than that of N1 at 293 K, and k 8 of N5 is also large r than k 5 of N1 at 238 K. M eanwhile, it was revealed th at the difference between ΔG 4 and ΔG 6 is not as much as the diff erence between ΔG 5 and ΔG 3 , w hich can ex plain wh y the ratio of k 1 / k 2 of N5 is much bigger than that of N1 . Correspondin gly, under U V irradiation, the rate constant of process CF → TC ( k 3 ) of N5 is lar ger than that of N1 due to the smaller ΔG 1 compared with ΔG 2 . 5. 5 Di scussion 112 Furthermore, the rate constant of pro cess TC → T T ( k 4 ) of N5 is larger th an that of N1 , because ΔG 3 is smaller than ΔG 4 . Figure 5.13 Pho t ochrom i c equi librium f or naphthopyr an. Figure 5.14 T he proposed energy di agram of two states system (black line) and t hree states system ( red line) (the ene rgy barriers are not accu rate, further need to be modified by the calcu l ation). 5 In -situ NMR A n aly s is 113 5.5.2 The Effect of 6-Substituent on Photochromic Properties of Naphthopyran during the Visible Light Irradiation in Low Temperature in -situ NMR Me asurements During low temperature in -situ NMR me asurements, naphthop yran N7 had a different photochromic behavior during visible light irradiation, comp ared w ith the unsubst ituted naphthopyran N6 (Figures 5.9-b and 5.10). Und er irr adiation with 420 n m light, the TT form of N7 was not conve rted into the CF form totall y in the presence of th e process CF →T C, although TT →T C was obs erved. The incr easing TC form prevent th e complet e conversion of the TT form because o f the process TC → TT (Figure 5.10 and Table 5.10) . On the contrar y, the pro cess TC → CF was detected in the s y st em of N6 under 420 nm irradiation. In order to explain this phenomenon, the UV spectra o f N6 and N7 should be consider ed (Figure 5.15). There w as no absorption detected in the area ≥3 70 nm for the cl osed form of N6 . However, an absorption band between 370 and 450 nm was detected in the UV spectrum of N7 . Ac cordingl y , the 420 nm light can induce the ring-open reaction for N7 , but not for N6 . As for the bathochromic shift in the spectrum of N7 , it is resulted from t he pres ence of the 6-acr y li c ester group, which ex tends π conjugation with in the whole structure . Figure 5.15 Abs or ptio n spectra o f N6 and N7 before UV irradia tion in aceton itrile (1.5×10 -5 M) at 293 K. 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 N6 N7 Absorbance Wavelength (nm) 5. 5 Di scussion 114 6 Summ ar y and Outlook 115 6 . Summary and Outlook In this work, the s y nthesis of remote selective C -H functionalization of naphthop yra ns was achieve d. The photoch romic prope rties of di fferent substituted 3 H -naphthopyrans w ere investigated b y U V/Vis s pectroscop y and in -situ NMR measurements. Dif ferent transformations between isomers, inc luding allen y l -naphthol (AP) formation, were discussed in detail. 6.1 The Synth esis of Naphthopyrans by Selective C-H Functi onalization In this part, two methods we re applied for the m -C-H functionalization of naphthop y r ans. The first method was directed selective C-H functionalization of naphthopyrans, and a nit rile containing directing group was used . For thi s method, two different routes were invest igated: 1) selective C - H functionalization of na phthalene 13 wa s achieved firstl y and two different produ cts, m -selective product 14 and m ’ -selective product 15 , were obt ained with a ratio of 14 : 15 =7:1 (Figure 6.1). However, the de sired na phthop y ran 21 wa s not detected durin g the naphthop y r an sy nth esis due to the unstable intermediate 85 , while b y product 22 was obtained in 40% yield. Therefore, route 2 was explored as follows: 2) the naphthop y r an with the directing group, N6 , was s y nthesiz ed firstl y . Then directed C-H functionaliz ation of N6 was achieved successfull y . Interestingly, onl y the 6- selective product N7 was observed (Figure 6.2). The second method w as nondirected C -H functionalization of naphthopyrans. The route was exploring nondirected C- H functionalization o f naphthalene 3 firstly, before tr y ing to synthesize the c orresponding naphthopyran. Un fortunately, 5 different products we re detected, which c annot be distinguished and s eparated from each other. Although this method works well for benzene compounds under the co ntrol of ster ic or e lectronic effects, [1 11] t here are too many active positions in a naphthalene structur e. Thus, new methods concerning nondirected C -H functionalization of naphthalenes should be developed in the f uture. 6.1 The Sy nt hesis of Select ive C-H Functional ization of N aphth opyrans 116 Figure 6.1 The route 1 of d i rected m -C-H func tionalization of naphthopyrans. 6 Summ ar y and Outlook 117 Figure 6.2 The route 2 of d i rected m -C-H func tionalization of naphthopyrans. 6.2 The Photoc h rom ic Properties of 3 H -Nap hthopyrans 118 6.2 The Phot o chrom i c Prop erties of 3 H -Naphthopy rans In this work, the photochromic behavior o f 10 different 3 H -naphthopyrans were explored with room temperature UV/Vis spectroscopy and low temperature in -situ NMR ex periments (F igure 6.3), where in the effects of substituents at 4 diffe rent positions on photochromic properties we re discussed: 8-substituent, 6-substituent, 2-substit uent and the different ar y l-substit uents attache d to C3 -atom. Figure 6.3 The structures o f naphthopyra ns investi gated in this work. For the effects of 8 -substituent s on photochromic properties of naphthop y r ans, four different substituents, ester, carboxylic acid, h ydroxy meth y l and ether meth y l were investigated in this work. In both two states s y stem and three states s ystem, naphthop y r ans with an 8-e ster subst ituent always had a bathochromic shift in the UV/Vis absorption spectra. Dur ing thermal relaxation, the thermal back speed (both of the process es TC → CF and TT → TC) of naphthop y rans with 8-ester substituent were faster (Figure 6.4) . Howeve r, in the procedure of UV irradiation, the ring-open speed (CF → TC) of the 8-ester naphthopyran was fa ster among three states sy stem with 3-C 6 H 4 F substituent (Table 6.1) while slower among two states s y stem (Table 6.2). As for the 8-ether meth y l and 8-hydrox y meth y l su bstituent s, the y made similar impact on the photochr omic behavior of 6 Summ ar y and Outlook 119 naphthopyrans, and both of them had longer half -life open forms in comparison to the 8-ester naphthopyran. Mor eover, the photochromic behavior of the naphthop y ran with 8-carbox y li c acid substituent ( N2 ) was influenced by the formation of acid dimers, which was solvent dependent. Figure 6.4 Com pari son of tim e resolved abso rbance at λ m ax of a) naphthopy ran N1 , N2 , N3 and N4 and b) naphthopy ran N5 , N6 and N7 (UV light: 340 nm , 12 m W/cm 2 for N1 , N2 and N3 ; 365 nm , 110 mW/cm 2 for N4 , N5 , N6 and N7 . 1.5 ×10 -5 M in ace tonitrile at 2 93 K ). Table 6.1 Com parison of photochrom i c propert ies of naphtho pyrans N5 and N6 . 0 200 400 600 800 1000 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Absorbance Time/s N1 N2 N3 N4 UV Irradiation a) 0 10 20 30 40 50 60 70 80 90 100 110 120 0.00 0.05 0.10 0.15 0.20 0.25 Absorbance Time/s N5 N6 N7 UV Irradiation b) 6.2 The Photoc h rom ic Properties of 3 H -Nap hthopyrans 120 Table 6.2 Com parison of photochrom i c propert ies of naphtho pyrans N1 , N3 and N4 . k 1 a k 2 b k 3 c k 4 c k 7 c k 8 c k 10 c Trend N5 > N6 N5 > N6 N5 > N6 N5 > N6 N5 < N6 N5 > N6 N5 < N6 [a ] In the dark, 1.5×10 -5 M in acetonitrile, 293 K. [b ] Irradia ted with 420 nm l ight, 73 m W/cm 2 , 1.5×10 -5 M i n ac etonitr ile, 293 K. [c ] 1× 10 -2 M in CD 3 CN at 238 K. UV light: 365 nm , 3.86 m W/cm 2 . Trend λ m a x a N1 > N4 > N3 k 1 a N1 > N4 > N3 k 2 a N1 > N3 > N4 k 3 b N1 < N3 < N4 k 4 b N1 < N3 < N4 k 5 b N1 > N3 k 6 b N1 > N3 [a] 1.5×10 -5 M in acetonit rile, 293 K. [b ] UV light: 365 nm, 0.45 m W/ cm 2 for N1 and N3 , 3.86 m W/ cm 2 for N4 , 1× 10 -2 M in CD 3 CN, 238 K. 6 Summ ar y and Outlook 121 The 6-acr y li c ester substituent on naphthop y ran N7 was introduced by C -H functionalization. From the UV absorption spectra ( Figure 6.5), th e 6-acr y li c ester induc ed a b athochromic shift. For the rin g-open speed (CF → TC) under UV irradiati on and the rin g closure speed (TC → CF and TT → TC) in the dark, the 6-acr ylic ester brou ght an acceleration (Table 6.3). Particularl y , regarding visible light irradiation, the ring openi ng reaction wa s observed for th e naphthopyran with the 6-acr y lic ester substit uent ( N7 ) und er ir radiation with 420 nm li ght, while rin g closure reac tion was found for N6 with this wavelength, the naphthop y ran without 6-substituent. Figure 6.5 Com pari son of UV absorp t ion sp ectra of naphtho pyrans N6 and N7 (UV lig ht: 365 nm, 110 m W/cm 2 . 1.5×10 -5 M in ace t onitri le at 293 K ). Table 6.3 Com parison of photochrom i c propert ies of naphtho pyrans N6 and N7 . 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) N6 in MeCN N6 in MeCN after UV N7 in MeCN N7 in MeCN after UV k 1 a k 2 b k 3 c k 4 c k 7 c k 8 c k 10 c Trend N7 > N6 N7 > N6 N7 > N6 N7 = N6 N7 < N6 N7 > N6 N7 > N6 [a ] In the dark, 1.5×10 -5 M in acetonitrile, 293 K. [b ] Irradia ted with 420 nm l ight, 73 m W/cm 2 for N6 , 505 n m li ght, 70 m W/cm 2 for N7 , 1.5×10 -5 M in aceton itrile, 293 K. [c ] 1×10 -2 M i n CD 3 CN at 238 K. UV light: 365 nm , 3.86 mW/cm 2 . 6.2 The Photoc h rom ic Properties of 3 H -Nap hthopyrans 122 Two different kinds of su bstituents were explored for the aryl substituents attached to the C3 -atom, resulting in two different s y stems: two states sy st e m and three states s y stem (Figure 6.3, blue part). On the one h and, in the UV absorption spectra, para -p y rrolidine of two st ates s y stem ( N1 ) brou ght a bathochromic shift for the ring -open forms ( Table 6.4). During the th ermal relax ation, the combination of ortho -chlorine and para -p y rrolidi ne substit uent accelerated the speed of TT → TC ( k 2 ) while d ecreased the speed of TC → C F ( k 1 ). T hus, the difference between k 1 and k 2 of N5 was far l arger than that of N1 , leading to two sta ge mon oexponential deca y for three states s ystem ( N5 - 7 ) while one biexponential decay for two states system ( N1 -4 ). At the sa me time, the speed o f TT → TC of three states s ystem was faster under irradiation with visible light, although it ca n thermal back to initial st ate after long enou gh time in the dark. On the other hand, in the low temperature in -situ NM R measurements, TT → TC was dete cted for tw o states s ystem durin g thermal relaxation. B y contrast, TC → TT was obse rved for N5 , which w as also different from room temperature UV/Vis e xperiments. In a ddition, the ra tios betwee n rates o f thermal back reaction of two states s y stem ( N1 and N3 ) are sim ilar at dif ferent tempe rature (293 K UV/Vis experiments and 238 K in -situ NMR measurements), and the ratios between rates of visibl e light irr adiation of two states system ( N4 ) are similar at different temperature, too (Table 6.5). Table 6.4 Photo chrom ic properties of N1 and N5 in th e procedu re of therm al back reaction. a λ m a x [nm] (Closed) λ m a x [nm] (Open) t 1/2 (s) t 3/4 (s) A 0 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) N1 261, 318 592 12 25 0.3807 90.9 b 47.1 b N5 261, 338 429 1.6 3.4 0.164 634 c 0.68 c [a] 1.5×10 -5 M in acetoni trile, 293 K. λ max , t 1/2 , t 3/4 and A 0 ar e obtained f rom experim ental data. [ b] k 1 and k 2 are t he fitting parameters from Equation 1 and data from Figure 4.5 - a and Table 4.2 ( Ch apter 4). [ c] k 1 and k 2 are the fi tting parameters from Equation 2 . k 1 ( k TC → CF , thermal ) from Figure 4.13 and Table 4.7, k 2 ( k TT → TC, ther mal ) from Fig ure 4.14 and Table 4. 8 (Chapt er 4). 6 Summ ar y and Outlook 123 Table 6.5 Com parison of ratios betwee n r ate s of napht hopyrans N1 , N3 and N4 . At last, 2-position substituents on N8 , N9 and N10 destabilized the open for ms of naphthopyrans. Therefore, th e thermal relaxation is too fast to be observed. Ev en in the lo w temperature in -situ NMR measurements, the presence of sw itchin g was still not detected. In addition, the photochromic behavior of naphthopyrans was influenced b y solv ents. W hen TCE was emplo y ed as the solv ent, a blue shift w as found in the UV absorption spectra and thermal back speeds w ere reduced, result ing from the inter action of open forms and int ermediates and tetrachloroethy lene molecule. Howe ver, the thermal bac k spee d of N2 was faster in TCE, because of the formation of acid dim er s, which is solvent depe ndent. [133] Furthermore, a small bathochromic shift was observed in the UV absorption spectrum of N3 in DCM and the rate o f thermal relaxation was acc elerated, compared with that in acetonitrile. Ratio N1 N3 N4 k 1 / k 2 a 2 1 - k 5 / k 6 b 2.5 1.5 - k TC→CF, VIS, 293 K / k TT→TC, VIS, 293K c - - 1 k TC→CF, VIS, 238 K / k TT→TC, VIS, 238K d - - 1.2 [a] 1.5×10 -5 M in a cetonitrile, 293 K. [ b ] 1×10 -2 M in CD 3 CN at 238 K . [c ] 1 .5 ×10 -5 M in acet onitr ile, 293 K, 565 nm l ight, 84 mW/cm 2 . [d ] 1×10 -2 M in CD 3 CN at 238 K, 565 nm light, 3.2 m W/cm 2 . 6.3 Outloo k 124 6.3 Outlook Remote 6- selective C-H func ti onalization of naphthopyrans was achieved. L ong term thi s method and related methods can be used for introducing different 6 -position substituents in naphthop y rans . Besides, considering the y ield is not so good an d more than 60% of starting material was left, further improve ment is s till possible. On the other hand, with diffe rent 3 H -naphthop yrans and their photoch romic properties in hand, th ese naphthop yrans can be applied fo r the dev elopment of photos witchable monola y ers on a Si(111) surf ace acc ording to the research experience of the Rück -Braun group. [7,8,137] N1 , N4 , N5 , N6 and N7 are potential compounds and candidates for monolayer designs . If we need two states system, N1 and N4 are fast and slow thermal relaxation naphthopyrans, respectivel y . If three states system are preferable, N5 and N6 are fast and slow thermal relaxation naphthopy rans, respectively. If different visible lig ht control i s expected, N7 is a favourable choice (Figure 6.6). Figure 6.6 Fu t ure application of photoswitchable monolay ers on a Si (111) surface. 7 Experim en tal Sect ion 125 7. Experimental S ection 7.1 Synthe sis 7.1.1 General Information All starting materials and reagents were pur chased from Sigma-Aldrich, Alfa Aesar, Acros, TC I and abcr of the highest available purity and were used without further purification. S olvents were dried prior to use according to standard pro cedures. [1] The reactions were moni tored by analytical thin-layer chromatograph y (TLC, silica gel, Merck 60 F 2 54 plates) and visualized b y UV light, potassium permangana te or Seebach reagent (phosphomol y bdic acid/Ce(IV)(SO4) 2 ) stain. Chromatography Flash-c olumn chromatograph y w as pe rformed using silica gel (MP silica, 32 -63 µm, 60 Å , MP Biomedica ls German y GmbH). Melting points Melting points were measured with a Büchi M-56 0 melting point appara tus using open capillary tubes and remain uncorrected. NMR spectroscopy 1 H, 13 C NMR spectra were recorded on a B ruker Avance II 400 MHz spe ctrometer or a Bruker Avance III 500 MHz spe ctrometer at room t emperature, unless other wise s tated. Chemical shifts were reported in p arts per million (ppm) and were refere nced to the re sidual solvent sig nals as the internal standard (CDCl 3 : δ = 7.26 ppm fo r 1 H NM R and δ = 77.16 ppm for 13 C NMR; DMSO- d 6 : δ = 2.50 ppm for 1 H NMR and δ = 39.52 ppm for 13 C NMR; Acetonitrile- d 3 : δ = 1.94 ppm for 1 H NMR and δ = 118.26 ppm for 13 C NMR). Data we re reported a s follows: chemical shift, multiplicit y (s = sin glet, d = doublet, t = triplet, q = quartet, m = multiplet), couplin g constants (Hz), and integra tion. 7.1 Synthesi s 126 IR spectrosc opy Infrared spectra were recorded as ATR (attenuat ed total reflectance) on a Nicolet FTIR 750 spectrometer and are rep orted as wa venumbers in cm -1 . Mass spectrometry High-resolution mass spectra were measured with a Finni gan MAT 95S or Thermo Fisher Scientific L TQ Orbitrap X L apparatus. 7.1.2 Pr ocedure Methyl-6-hydroxy-2-naphtoate (2) [124] To a solution of 6 -h y d rox y-2-naphtoic-acid 1 (1.935 g, 10.0 mmol, 1.00 eq.) in MeOH (10 m L), SOC l 2 (1.85 mL , 25.0 mmol, 2.50 eq.) was added dropwise. The reaction was refluxed for 3 h at 75 °C. MeOH was removed and the reaction mixture was diluted in EA (50 m L ). I t was washe d b y saturated NaHCO 3 (3 25 mL) and dried over NaSO 4 . The solve nt was removed under reduc ed pr essure and purification b y column chromatogra ph y (pentane/EA = 5:1) to give product 2 (1.965 g, 9.7 mmol, 97%) as a white solid. R f = 0.72 (pentane/ EA , 1:1); Mp : 171.3-172.6 º C; 1 H -NMR (400 MHz, DMSO - d 6 ): δ 10.18 (s, 1H, H-11(OH)), 8.49 (s, 1H, H-6), 7.97 (d, 3 J = 8.8 Hz, 1H, H-10), 7.86 (dd, 3 J = 8.6 Hz , 4 J = 1.7 Hz, 1H, H-2), 7.77 (d, 3 J = 8.6 Hz, 1H, H-3), 7.19-7.15 (m, 2H, H-9, H-7), 3.88 (s, 3H, H-14); 13 C- NMR (126 MHz, DMSO - d 6 ): δ 166. 5 (C-12), 1 57.8 (C-8), 137.2 (C-4), 131.3 (C -10), 130.6 (C- 6), 126.7 (C-5), 126.5 (C -3), 125.2 (C -2), 123.8 (C -1), 119.8 (C -9), 108.8 (C -7), 52.1 (C -14); I R (ATR): ν (cm -1 ) = 3389, 2953, 1679, 1433, 1203, 1098, 917, 812, 756 ; HR MS (AP CI) calculated for C 12 H 11 O 3 + [M+H] + , m /z : 203.0703; found: 203.0708. 7 Experim en tal Sect ion 127 Methyl-6-(methoxymethoxy)-2-naphthoate (3) One clea n 2-ne ck round bottom flask was dried carefully under a nitro ge n atmosphere . Dr y DMF (10 mL) and NaH (60 % in mineral oil, 260 mg, 6.5 mmol, 1.30 eq.) was added. Then ester 2 (1.019 g , 5.0 mm ol, 1.00 eq. ) was added portion wise at -5 °C. After the bubblin g had subsided, MOMCl (0.8 m L, 10.0 mmol, 2.00 eq.) was added dropwi se to the reaction mix ture. After stirring for 1 h at room temperature , the reaction was completed as checked b y T L C. Th e mixture was cooled again to 0 °C and distilled water was added. The mix ture was extracted with Eth y l acetate (3 25 mL) and the or ganic l ayers were combined an d washed with distilled water (3 15 m L) and brine (15 mL), and then dried over Na 2 SO 4 . The solvent was removed under reduced pr essure and purification b y column chromatograph y (pentane/EA = 15:1) y ielded product 3 (1.256 g, 4.5 mm ol, 90%) as a white solid. R f = 0.72 (p entane/ eth y l acetate, 2:1); Mp : 78.3-79.2 ºC; 1 H-NMR (400 MHz, CDCl 3 ): δ 8.54 (s, 1H, H -6), 8.02 (d d, 3 J = 8.8 Hz, 4 J = 1.7 Hz, 1H, H-2), 7.87 (d, 3 J = 9.0 Hz, 1H, H-10), 7.76 (d, 3 J = 8.5 Hz, 1H, H-3), 7.41 (d, 4 J = 2.3 Hz, 1H, H-7), 7.27 (d d, 3 J = 8.8 Hz , 4 J = 2.4 Hz, 1H, H-9), 5.32 (s, 2H, H-12), 3. 97 (s, 3H, H-17), 3. 53 (s, 3H, H-14 ); 13 C-NMR (126 MHz, C DCl 3 ): δ16 7.5 (C -15), 157.1 (C -8 ), 13 7.1 (C -4), 131.1 (C -1 0), 131.0 (C -6), 128.5 (C - 5), 127.3 (C -3), 126.0 (C -2), 125.8 (C-1), 119.9 (C -9), 109.8 (C -7), 9 4.6 (C -12), 56.4 (C-14), 52.2 (C -17); IR (ATR): ν (cm -1 ) = 3003, 2953, 290 7, 2850, 2828, 1708, 1626 , 1600, 1478, 1428, 1416, 1383, 1339, 1286, 1248, 1198, 1148, 1125, 1097, 1076, 997, 911, 85 9, 841, 825, 812, 782, 766, 751, 723, 651, 621, 548, 527, 476 ; HRMS (APCI) calculated for C 14 H 15 O 4 + [ M+H ] + , m/z: 247.0965; found: 247.0962. (6 -(Methoxymethoxy)naphthalene -2-yl)me thanol (4) [125] One clea n 2-neck round bottom flask was dried ca refully under a nitro gen atmosphere . C ompound 3 (492 mg, 2.0 mmol, 1.00 eq.) and 10 m L dr y THF were added. The mixture was cooled do wn to 0°C. To the cooled solut ion, LiAlH 4 (140 m g, 3.5 mm ol, 1.75 eq.) was added portionwise. The reaction was stirred for 24 h until complete consumption of the starting 7.1 Synthesi s 128 material and quenched with cold wa ter slowly. Then the mixture was filtered over Celite ® and the filtrate was extracted wit h EA (3 15 mL ) and washed with brine (15 mL ). The organic la y er wa s dried over Na 2 SO 4 . The solvent was removed und er reduc ed pressure and purification b y column chromatogra ph y (p entane/EA = 8:1) gave product 4 (370 mg, 1.7 mmol, 8 5%) as a white- ye llow solid. R f = 0.31 (pent ane/ ethy l acetate, 2:1); Mp : 55.3-56.1 ºC; 1 H-NMR (400 MHz , CDCl 3 ): δ 7.76- 7.73 (m, 3H, H -10, H-3, H-6), 7.44 (dd, 3 J = 8.4 Hz, 4 J = 1.5 Hz, 1H, H-2), 7.39 (d, 4 J = 2.5 Hz , 1H, H-7), 7.22 (dd, 3 J = 8.8 Hz , 4 J = 2.5 Hz, 1H, H-9), 5.29 (s, 2H, H-12), 4. 81 (s, 2H, H- 15), 3.53 (s, 3H, H-14); 13 C-NMR (126 MHz , CDCl 3 ): δ155.28 (C -8), 136.64 (C-1), 134.10 (C-4), 129.53 (C -10), 129.49 (C-5), 127.63 (C -3), 125.96 (C-2), 125.55 (C-6), 119.38 (C-9), 110.06 (C-7), 94.69 (C -12), 65.63 (C-15), 56 .24 (C -14); IR (ATR): ν (cm -1 ) = 3290, 2993, 290 9, 2833, 1630, 1604, 1480, 1150, 1025, 991, 862 , 755 ; HRMS (ESI) calculated for C 13 H 13 O 2 + [M - OH] + , m/ z: 201.0910; found: 201.0911. 2-Bromomethyl-6-(methoxymethoxy)naphthalene (5) One clean 2-ne ck round bottom flask was dried carefull y under a nitrogen atmosphere . Dimeth y l sulfide (DMS, 215 µ L , 2.93 mmol, 1.8 0 eq.) was added to a su spension of N-bromosuccinimide ( NBS, 440 mg, 2.45 mmol, 1.5 eq.) in dry DCM (2.5 m L ) at 0 °C and stirred for 10 min. The reac tion mixture was cooled to −20 °C and alcohol 4 (355 m g, 1. 63 mmol, 1 eq.) in dry DCM ( 2.5 m L) was a dded dropw ise. The mixture was further stirred at 0 °C for additional 4 h. The reaction mixture was poured into cold water (10 mL) a nd ex tracted with DCM (3 15 mL ). The organic layer was wa shed with brine (15 mL) and dried over Na 2 SO 4 . The solvent was removed under reduced pressure. Then crude product 5 was purified b y quick filtration through a sho rt plug of sil ica gel, produ ct 5 (403 mg, 1.42 mmol, 88 %) was isolated as a yellow solid. R f = 0.89 (pentane/ ethy l acetate, 4:1); Mp : 71.3. 3-71.8 ºC; 1 H -NMR (40 0 MHz, CDCl 3 ): δ 7.76 (s, 1H, H-6), 7.75-7.72 ( m, 2H, H-10, H-3), 7. 47 (dd, 3 J = 8.4 Hz, 4 J = 2.0 Hz, 1H, H-2 ), 7.39 (d, 4 J = 2.5 Hz, 1H, H-7), 7. 23 (dd, 3 J = 9 Hz, 4 J = 2. 5 Hz , 1H, H-9), 5.30 (s, 2H, H-12), 4.66 (s, 2 H, 7 Experim en tal Sect ion 129 H-15), 3.53 (s, 3H, H-14) ; 13 C-NMR (126 MHz, CDCl 3 ): δ 155.81 (C -8), 134.35 (C-1), 133.39 (C -4), 129.63 (C-3), 12 9.27 (C-5), 128.04 (C-6 ), 127.84 (C-10 ), 127.4 7 (C-2), 119.68 (C-9), 110.07 (C-7), 94.65 (C-12), 56.26 (C -14), 34.47 (C-15); IR (ATR): ν (cm -1 ) = 3321, 2924, 2850, 2828, 1993, 1729, 1627, 1602, 1502, 1476, 1439, 1379, 1342, 1297, 1260, 1209, 1147, 1121, 1076, 985, 937, 921, 901, 861, 82 3, 755, 687, 668, 588; HRMS (APCI) calculat ed for C 13 H 13 O 2 + [M - Br ] + , m/z: 201.0910; found: 201.0912. 3,5-Di- tert -butyl-2-(methoxymethoxy)benzaldehyde (7) [84] One cle an 2 -neck round bottom flask was dried carefull y under a nitroge n atmosphere . Dry DMF (7 m L) and NaH (60% in mineral oil , 0.33 g, 13.0 mmol, 1.30 eq.) was added. Then aldeh yde 6 (2.35 g, 10.0 mmol, 1.00 eq. ) were add ed portionwise at -5 °C. After the bubbling had subsided, MOMCl (1.60 mL, 20.0 mmol, 2.00 eq.) was added dropwise to the reac tion mixture. After stirring for 1 h at room tempera ture, the reaction was completed a s checked by T L C. The mix ture was cooled to 0 °C again and distilled wa ter was added. Then the mixture was extracted with eth y l ace tate (3 25 mL) and the organic layers was combined and washed with distilled water (3 15 mL ) and brin e (15 m L), and then dried ov er Na 2 SO 4 . The solvent was removed under r educed pressure and purification b y column chromatogra ph y (pentan e/EA = 1 00:1) y ield ed product 7 (2.54 g, 9.14 mmol, 91%) as colorless oil. R f = 0.91 (p entane/ eth yl acetate, 5:1); 1 H-NMR (400 MHz, CDCl 3 ): δ 10.22 (s, 1H, H-9), 7.72 (d, 4 J = 2.6 Hz, 1H, H-3), 7. 64 (d, 4 J = 2.6 Hz, 1H, H-5), 5.02 (s, 2H, H- 7), 3.63 (s, 3H, H-8), 1.46 (s , 9H, H-13), 1.32 (s, 9H, H-11); 13 C-NMR (126 MHz, CDCl 3 ): δ191.7 (C -9), 158.0 (C-1), 146.7 (C -4), 142.9 (C-6), 130.6 (C-2), 130.2 (C -3), 123.7 (C -5), 102.3 (C -7), 57.6 (C -8), 35.2 (C-12), 34.7 (C-10), 31.3 (C-13), 30.9 (C-11); IR (ATR): ν (cm -1 ) = 2956, 2906, 2870, 1685, 1597, 1576, 1477, 1438, 1385, 1362, 1298, 1266, 1235, 1159, 1116, 1072, 956, 929, 89 4, 816, 744, 675, 649; HRMS (APCI) calculated for C 17 H 27 O 3 + [ M+H ] + , m/z: 279.1955; found: 279.1959. 7.1 Synthesi s 130 (3,5- Di -tert-butyl-2-(methoxymethoxy)phenyl)methanol (8) [8 4] To a cooled solution of aldehyde 7 (2.54 g, 9.14 mmol, 1.00 eq.) in EtOH (30 mL), Na BH 4 (0.69 g, 18.3 mmol, 2 eq.) was added portionwise at 0 °C. The r eaction was w armed to room temperature and stirred for 3 h. Then EtOH was removed, and 30 mL of water was added at 0 °C to quench the reaction. The reaction mix ture was extracted with EA (30 mL) thre e times. The combined organic layers were washed with br ine (25 mL) and dried over Na 2 SO 4 . The solvent was removed and purif ication by column chromatog raphy (pe ntane/EA = 20:1) y ielded product 8 (2.39 g, 8.51 mmol, 93 %) as a colorless oil. R f = 0.52 (pentane/ ethy l acetate, 5:1); Mp : 39 ºC; 1 H-NMR (400 MHz, CDCl 3 ): δ 7.34 (d, 4 J = 2.5 Hz, 1H, H-3), 7.28 (d , 4 J = 2.5 H z , 1H, H-5), 4 .99 (s, 2H, H-7), 4.59 (s, 2H, H- 9), 3.69 (s, 3H, H-8), 1.39 (s, 9H, H-14), 1.31 (s, 9H, H-12); 13 C- NMR (126 MHz, CDCl 3 ): δ 153.9 (C -1), 146.8 (C -4), 142.2 (C-6 ), 134.3 (C-2), 126.3 (C-3), 124.5 (C-5), 100.4 (C-7 ), 62.0 ( C-9), 57.1 (C-8), 35.2 (C -13), 34.5 (C-11), 31.5 (C-12), 31.2 (C-14) ; IR ( ATR): ν (cm -1 ) = 3391, 29 53, 290 2, 2868, 1603, 1477, 1438, 1392, 1362, 1301, 1273, 1229, 1197 , 1160, 1123, 1063, 100 8, 965, 933, 881, 818, 652, 552, 495 ; HR MS (A PCI) calculated for C 17 H 27 O 2 + [M - OH] + , m/z: 263.2006; found: 263.2009. 1-(Bromomethyl)-3,5- di -tert-butyl-2-(methoxymethoxy)benze ne (9) [84] One clea n 2-neck round bottom flask was dried care full y under a nit rogen atmosphere . Dimethy l sulfide (DMS, 1.12 mL, 15 .3 mmol, 1.80 eq. ) was added to a suspension of N-bromosuccinimide (NBS, 2.27 g , 12.8 mmol, 1.5 eq.) in dry DCM (6 m L ) at 0 °C and stirred f or 10 min. The reac tion mixture was cooled to − 20 °C and alcohol 8 (2.39 g, 8.51 mmol, 1 eq.) in dry DCM (6 mL) was added dropwise. Th e mix ture was further stirred at 0 °C for 4 h. The reaction mixture was poured into cold water (10 m L) and extracted with DCM ( 3 15 mL ). The o rganic layer w as washed with brine (10 mL) and dried over Na 2 SO 4 . The solvent was removed under reduce d pressu re. Then t he crude product was purified b y quick filtration through a sho rt plug of silica ge l to yield crude product 9 as a ye llow soli d. 7 Experim en tal Sect ion 131 2-(3,5-Di- tert - butyl-2-( methoxymethoxy)phenyl)acetonitrile (10) [84] Crude bromide 9 was then dissolved in EtOH (15 m L) and a solution of NaCN (1.03 g, 21.0 mmol, 3.0 eq.) in 3 m L of water was added to it. (CAUTI ON: NaCN is an extremely tox ic chemical and should be handled in a well maintained fume hood. The o perator should h ave appropriate protec tion at all times.) The reaction was refluxed overnig ht. The solvent was removed under reduced pressure and 80 m L of EA was added. The organic la ye r was washe d with water (5×40 m L ) , brine (40 mL) and dried over Na 2 SO 4 . The solvent was removed u nder r educed pressure and purification b y column chromatography (pentane/EA = 100:1) y ield ed produ ct 10 (1.68 g, 5.80 mm ol, 68% ov er 2 steps) as an orange crystalline solid. R f = 0.44 (pe ntane/ eth y l acetate, 20:1); Mp : 48 ºC; 1 H -NMR (500 MHz, CDCl 3 ): δ 7.34 (d, 4 J = 2.3 Hz, 1H, H-3), 7.30 (d , 4 J = 2.3 H z , 1H, H-5), 4 .96 (s, 2H, H-7), 3.93 (s, 2H, H- 9 ), 3.64 (s, 3H, H-8), 1.39 (s, 9H, H-14), 1.31 (s, 9H, H-12) ; 13 C-NMR (126 MHz , CDCl 3 ): δ 153.2 (C-1), 147.1 (C -4), 142.8 (C-6), 125.0 (C-5), 124.6 (C-2), 123. 8 (C -3), 118.9 (C-10), 10 1.0 (C-7), 57.2 (C-8), 35.3 (C-13), 34.6 (C-11), 31.4 (C -12), 31.2 (C -14), 20.3 (C-9); IR (ATR): ν (cm -1 ) = 2961, 2951, 2906, 2873, 2828, 2246 (C N), 1785, 1602, 1476, 1 460, 1441, 1411, 1402, 1393, 1361, 1315, 1273, 1232, 1197, 1159, 1120, 1073, 945, 931, 898, 892, 878, 819, 794, 776, 725, 666, 652, 623, 616, 570 ; HRMS (APCI) calcula ted for C 18 H 28 NO 2 + [M +H ] + , m/z: 290.2115; found: 290.2111. 2-(3,5-Di- tert - butyl-2-h ydroxyphenyl)acetonitrile (11) [84] MOM-protected phenol 10 (1.68 g, 5.80 mmol, 1 eq.) w as taken up in MeCN (150 mL ). Aqueous HCl (2 M, 60 mL , 20 eq.) was added to the flask and the r eaction mixture was warmed to 70 °C for 30 min. The solvent was removed under redu ced pressure and water ( 25 m L ) was added. The mixture was then extracted with DCM (3×25 mL). The organic la y e r w as washed with brine (15 m L) and dried over Na 2 SO 4 . The solvent was removed under reduced pressure and purification by column chromatograph y (pentane/EA = 40 :1) y ielded fairl y pur e 7.1 Synthesi s 132 phenol 11 . The product was further purified by r e-cr y stallization from hot pentane/c y clohexane y i eld ed pu re phenol 11 (1.01 g, 4.10 mmol, 71%) as white- yellow crystals. R f = 0.35 (p entane/ ethyl acetate, 10:1); Mp : 110 ºC; 1 H-NMR (500 MHz, CDCl 3 ): δ 7.27 (d, 4 J = 2.4 Hz, 1H, H-3), 7.21 (d, 4 J = 2.4 Hz , 1H, H-5), 4.97 (s, 1H, H-7), 3.71 (s, 2H, H-8), 1.45 (s, 9H, H-13), 1.30 (s, 9H, H-11); 13 C-NMR (126 MHz, CDCl 3 ): δ 149.6 (C-1), 143.6 (C-4), 134.7 (C -6), 124.5 (C-3), 123.8 (C-2), 118.3 (C-9), 34.4 (C-10), 34.1 (C-12), 31.5 (C-11), 30.4 (C-13), 19.3 (C-8); IR (ATR): ν (cm -1 ) = 3297, 2957, 290 6, 2867, 226 8 (CN), 1481, 1446, 1412, 1391, 1361, 1344, 1312, 1276, 1225, 1205, 1165, 1122, 925, 906, 892, 874, 824, 797, 762, 723, 675, 650, 566 ; HRMS (APCI) calcula ted for C 16 H 24 NO + [M +H ] + , m/z: 246.1852; found: 246.1858. 2-(3,5-Di-tert-butyl-2-((6-(methoxymethoxy)naphthalen-2-yl)methoxy)phenyl)acetonitrile (12) One clean 2 -neck round bott om flask was dried carefully und er a nitrogen atmosphere . To a cooled solution of phenol 11 (49 2 mg, 2.0 mmol) in DMF (2 mL), NaH (60% in mineral oil, 84 m g, 2.1 mm ol, 1.05 eq.) was adde d port ion wise at 0 °C. A fter the bubbling had subsided, benzyl bromide 5 (562 mg, 2.0 mmol, 1.00 eq.) was adde d portion wise to the reaction mixture. After 4 h of sti rring , 5 mL distil led water was ad ded. The mix ture was extracted with Ethyl acet ate (3 15 m L) and the organic la yers w ere washed with dist illed water (3 10 mL) and brine ( 10 mL), and then dried over Na 2 SO 4 . The solvent was removed under reduce d pressure and purification by column chromatography y i elded the benzyl ethe r product 12 (660 mg, 1.48 mmol, 74%) as a white- yellow solid. R f = 0. 60 (pentane/ eth y l ace tate, 10:1 ); Mp : 124.5-125 ºC; 1 H-NMR (500 MHz, CDCl 3 ): δ 7.90 (s, 1H, H-5), 7.82 (d, 3 J = 8.9 Hz, 1H, H-3), 7.81 (d, 3 J = 8.4 Hz, 1H, H-8), 7.53 (d d, 3 J = 8.4 Hz, 4 J = 1.7 Hz , 1H, H-7 ), 7.44 (d, 4 J = 2.5 Hz, 1H, H-10 ), 7.40 (d, 4 J = 2.4 Hz, 1H, H -16 ), 7.35 (d, 4 J = 2.4 Hz, 1H, H-18 ), 7. 27 (d d, 3 J = 8.9 Hz, 4 J = 2.5 Hz , 1H, H-2 ), 5.32 (s, 2H, H-11 ), 5.02 (s, 2H, H-13 ), 3.77 (s, 2H, H-20), 3.55 (s, 3H, H-12 ), 1.46 (s, 9H, H-25), 1.35 (s, 9H, H-23); 13 C-NMR (126 MHz, CDCl 3 ): δ 155.5 (C -1), 153.8 (C -14), 147.2 (C -17), 143.0 (C -19), 134.2 (C -9), 132.8 7 Experim en tal Sect ion 133 (C -6), 129.7 (C -3), 129.5 (C -4), 127.7 (C -8), 125.4 (C -5), 125.3 (C -18), 125.2 (C -7), 125.1 (C -16), 123.9 (C -15), 119.6 (C -2 ), 118.8 (C -21), 110.1 (C - 10), 94.7 (C -11), 75.8 (C - 13), 56.3 (C -12), 35.8 (C -24), 34.8 (C-22), 31.6 (C -23), 31.5 (C -25), 19.4 (C-20); IR (ATR): ν (cm -1 ) = 2962, 2899, 2360, 2252, 1631, 1603, 1477, 1441, 1375, 1225, 1151, 1078 , 986, 923, 890, 854, 821 ; HRMS (APCI) calculated for C 29 H 36 NO 3 + [M +H ] + , m/z: 446.2690; found: 446.2688. 2-(3,5-Di-tert-butyl-2-((6-(methoxymethoxy)naphthalen-2-yl)methoxy)phenyl) -2-isobutyl-4- methylpentanenitrile (13) One cl ean 2 -neck round bottom flask was dried carefully under a nitro gen atmosphere . THF (3 m L) and lithium d iisopropy l ami de ( L DA) (2.0 M in T HF, 2.22 mmol, 1.50 eq.) we re added. The mixture was cooled to -78 °C. Then a solut ion of benz y l ether 12 (660 m g, 1.48 mmol, 1.00 eq.) from the pr evious s tep dissolved in THF (2 mL) was added dropwise at -78 °C . After sti rring for 30 min, 1 -iodo-2- methylpropa ne (0.25 m L, 2.22 mmol, 1.50 equiv.) was added d ropwise to th e reaction mix ture and stirring for 30 min was c ontinued at – 78 °C. The re action was then warmed up to room temperature and sti rring was continued for 2 h. Then saturated aqueous NH 4 Cl was added dropwise (3 m L ) and THF was removed in vacuo. Afterwards, EA (15 m L ) was added and the organic la y er was wash ed with water (2 × 8 mL), f ollowed b y brine (8 m L), and then dried over N a 2 SO 4 . Subsequentl y , the solvent was removed, an d the crude product w as dried under high v acuum. The sequence w as repea ted again using the crud e mix ture. The product was furth er purified by column chromatogra ph y and yielded the α -cy ano dialk y la ted product 13 (737 m g, 1.32 mm ol, 89%) as a white-y ellow solid . R f = 0.58 (pent ane/ eth yl acetate, 20:1); Mp : 155.3-156.7 ºC; 1 H-NMR (500 MHz , CDCl 3 ): δ 7.88 (s, 1H, H-5), 7.81-7.77 ( m, 2H, H-3, H-8), 7.50 (d d, 3 J = 8.5 Hz, 4 J = 1.3 Hz , 1H, H-7 ), 7.45 (d, 4 J = 2.4 Hz, 1H, H-18 ), 7.42 (d, 4 J = 2.3 Hz, 1H, H-10 ), 7.35 (d, 4 J = 2.4 Hz, 1H, H-16 ), 7.25 (d d, 3 J = 8.9 Hz, 4 J = 2.3 Hz , 1H , H-2 ), 5.31 (s, 2H, H-11 ), 5.05 (s, 2H, H-13 ), 3.54 (s, 3H, H-12), 2.21- 2.19 (m, 2H, H-22 ), 1.85-1.81 (m, 2H, H-22 ), 1.76-1.69 (m, 2H, H-23 ), 1.43 (s, 9H, H-28), 1.35 (s, 9H, H-26), 1.02 (d, 3 J = 6.6 Hz, 6H, H-24 ), 0. 75 (d, 3 J = 6.6 Hz, 6H, H-24) ; 13 C-NMR (126 MHz, CDCl 3 ): δ 155.2 (C -1), 153.9 (C -14), 146.2 (C -17), 143.4 (C -19), 134.0 (C -9), 133.3 (C -6), 7.1 Synthesi s 134 130.6 (C -15), 129.7 (C -3), 129.5 (C -4), 127.4 (C -8), 125.7 (C -16), 125.4 (C -21), 1 25.2 (C -18), 124.8 (C -7), 124.7 (C -5), 1 19.4 (C -2), 110.2 (C - 10 ), 94.8 (C -11), 76.8 (C - 13), 56.2 (C -12), 50.1 (C -22), 46.2 (C-20), 36.3 (C -27), 34.8 (C-25), 32.3 (C -28), 31.6 (C -26), 26.2 (C-23), 24.0 (C -24), 23.6 (C-24); IR (ATR): ν (cm -1 ) = 2954, 2869, 236 1, 2229, 1636, 1607, 1507, 1467, 1439, 1388, 1363, 1333, 1260, 1218, 1170, 1147, 1118, 1078, 1001, 923, 910, 884, 864, 810, 732, 648, 476, 459, 419 ; HRMS (APCI) calculated for C 37 H 52 NO 3 + [M +H ] + , m/z: 558.3942; found: 558.3937. Silver pivalate [138] Pivalic acid (2.527 g, 24.5 mmol, 0.98 eq) was added to 25 mL H 2 O. Then NaOH (960 m g, 24 mmol, 0.96 eq) was added to this solution. After stirring for 15 min at room temperature, a solution of AgNO 3 (4.247 g , 25 mmol, 1.0 eq) in 40 mL H 2 O was added dropwise. After sti rring for 15 min at room temperature, the mixture was filtered and a white solid was collected, which was washed b y H 2 O (3 × 25 mL ), MeO H (3 × 25 mL ) and hexane (3 × 25 mL ), r espectively. After being d ried under vacuu m, silver pivalate was afforded as a white soli d with a y i eld of 80 % (4.180 g, 20 mmol). 1 H-NMR (400 MHz, DMSO- d 6 ): δ 1.10 (s, 9H,). Ethyl (E)-3- (3 -((2,4- di -tert-butyl-6- (4 -cyano-2,6-dimethylheptan-4-yl)phenoxy)methyl)-7- (methoxymethoxy)naphthalen-1-yl)acrylate (14) A 10 m L se aled tube ( with a Teflon cap , ACS Glass incorporated ) was flame dried and compound 13 (55.8 mg, 0.10 mm ol, 1.0 equiv.), Pd(OPiv) 2 (3.4 mg, 0.010 mmol, 10 mol%), AgOPiv (62.7 mg, 0.30 mmol, 3.0 equiv.) and ethyl acr y l ate (22 µ L, 0.20 m mol, 2.0 equiv.) were a dded, before DCE (1.0 mL) w as used to wash down the solids on the sides of the tube wall. The tube was then capped and submerged into a prehea ted 90 °C oil bath . The oil bath was cove red with aluminum foil to stabilize the oil bath temperature and to shield the reaction from light. After one d ay o f stirring, the tube was shaken manually to dislodge the silver salt off the sides of the wall. The reaction was stirred for a total of 7 Experim en tal Sect ion 135 42 h and then cooled do wn to room temperatur e. The re action mixture was filtered throu gh a pad of Celite and washed with EA (3 × 3 m L). Th e solvent was r emoved und er reduced pressure and purified b y column chromatograph y (p entane/ EA , 100/ 1 ) to y ield produ ct 14 (30 mg, 0.046 mmol, 46%) as a ye llow oil . R f = 0.25 (pentane/ eth yl acetate, 20:1); 1 H-NM R (500 MHz, CDCl 3 ): δ 8.45 (d, 3 J = 15.7 Hz, 1H , H-29), 7.96 (s, 1H , H-9 ), 7.85 (d, 3 J = 9.0 Hz , 1H, H-7 ), 7.80 (s, 1H, H-1 ), 7.70 (d, 3 J = 2.3 Hz, 1H, H-4 ), 7.41-7.39 (m, 2H, H-16, H-18 ), 7.33 (d d, 3 J = 9.0 Hz, 4 J = 2.3 Hz , 1H, H-6 ), 6.52 (d, 3 J = 15.7 Hz , 1H, H- 30 ), 5.34 (s, 2H, H -11 ), 5.07 (s, 2H, H-13 ), 4.32 (q, 3 J = 7. 1 Hz , 2H, H-32), 3.54 (s, 3H, H-12 ), 2.17-2.15 (m, 2H, H-22 ), 1.89-1.85 (m, 2H, H-22 ), 1.77-1. 72 (m, 2H, H-23 ), 1.43 (s, 9H, H-28), 1.37 (t, 3 J = 7.1 Hz , 3H, H-33), 1.35 (s, 9H, H- 26 ), 1.03 (d, 3 J = 6.6 Hz , 6H, H-24 ), 0.75 (d, 3 J = 6.6 Hz, 6H, H-24) ; 13 C-NMR (126 MHz, CDCl 3 ): δ 167.0 (C -31), 155.9 (C -5), 153.7 (C -14), 146.3 (C -17), 143.3 (C -19), 141.8 (C -29), 132.8 (C -10), 132.1 (C -3), 131.2 (C -2), 130.8 (C -15), 130.5 (C -7), 129. 9 (C -8), 127.3 (C -9 ), 125.6 (C -18), 125.3 (C -21), 1 24.8 (C -16), 123.9 (C - 1), 121.0 (C -30), 119.2 (C -6), 106.9 (C -4), 94.8 (C -11), 76.5 (C-13), 60.7 (C-32), 56.3 (C -12 ), 50.5 (C-22 ), 45.5 (C -20 ), 36.3 (C -27), 34.7 (C-25), 32.2 (C -28), 31.5 (C -26), 26.1 (C-23), 24.0 (C - 24), 23.6 (C-24), 14.5 (C -33); IR (ATR): ν (cm -1 ) = 2955, 2870, 2232, 1712, 1627, 1606, 1505, 1466, 1439, 1393, 1364, 1308, 1255, 1219, 1173, 1153, 1123, 1080, 1049, 1005, 976, 924, 865, 826, 809, 734, 652, 588, 557, 518 ; HRMS (APCI) calculated for C 42 H 58 NO 5 + [M +H ] + , m/z: 656.4310; found: 656.4301. Ethyl ( E )-3- (6 -((2,4- di -tert- butyl-6- (4 -cyano-2,6-dimethylheptan-4-yl)phenoxy)methyl)-2- (methoxymethoxy)naphthalen-1-yl)acrylate (15) A 10 mL sealed tube (with a Teflon cap) was flame dried and compound 13 (55.8 mg, 0.10 mmol, 1.0 equiv.), Pd(OPiv) 2 (3.4 mg , 0.010 mm ol, 10 mol%) , AgOPiv (62.7 mg, 0.3 0 mmol, 3.0 equiv.) , eth y l acrylate (22 µ L, 0.20 mmol, 2.0 equiv.) were added. DCE (1.0 mL) was use d t o wa sh down the solids on the sides of the tube wall. The tube was then capped and submerged int o a pre heated 90 °C oi l bath. The oi l bath 7.1 Synthesi s 136 was covered with aluminum foil to stabilize the oil bath temperature and to shield the reaction from light. After one d a y of stirring, the tube was shaken manu ally to dislo dge the silver salt off the sides of the wall. The reaction was stirred for a total of 4 2 h and then cooled down to room temperature. The reaction m ixture was filtered th rough a pad of Celite and washed with EA (3 × 3 mL ). The solvent was r emoved under reduced pr essure a nd purif ied by c olum n c hromatography (pentane/ EA , 100/1 ) to yield product 15 (5 mg, 0.007 mm ol, 7%) as a ye llow oil . R f = 0.30 (pentane/ eth yl acetate, 20:1); 1 H-NM R (500 MHz, CDCl 3 ): δ 8.43 (d, 3 J = 15.8 Hz, 1H , H-29), 8.19 (s, 1H, H-9 ), 7.81 (d, 3 J = 8.5 Hz, 1H, H-2 ), 7.59 (d d, 3 J = 8.5 Hz, 4 J = 1.3 Hz , 1H, H- 1 ), 7.50-7.48 (m, 2H, H- 6, H-7 ), 7.42-7.40 (m, 2H, H-16, H-18 ), 6.52 (d, 3 J = 15.8 Hz, 1H, H-30 ), 5.31 (s, 2H, H-11 ), 5.09 (s, 2H, H-13 ), 4.29 (q, 3 J = 7.1 Hz , 2H, H-32), 3.5 3 (s, 3H, H-12 ), 2.18- 2.16 (m, 2H, H-22 ), 1.84-1.80 (m, 2H, H-22 ), 1.75-1.67 (m, 2H, H-23 ), 1.44 (s, 9H, H-28), 1.36- 1.33 (m, 12H, H-26, H- 33 ), 1.01 (d, 3 J = 6.6 Hz, 6 H, H-24 ), 0.74 (d, 3 J = 6.6 Hz, 6H, H-24) ; 13 C- NMR (126 MHz, CDCl 3 ): δ 166.7 (C -31), 154.6 (C -5), 153.8 (C -14), 146.3 (C -17), 143.4 (C -19), 141.1 (C -29), 134.5 (C -10), 134.3 (C -8), 133.7 (C -4), 130.7 (C -21), 128.3 (C -2), 127.7 (C -3), 125.6 (C -16), 125.5 (C -15), 125.3 (C -1), 125.1 (C -18), 122.0 (C -30), 120.4 (C -9), 118.2 (C -6), 112.8 (C -7), 94.8 (C -11), 76.9 (C-13), 60.8 (C -32), 56.3 (C -12 ), 50.4 (C -22 ), 45.9 (C -20 ), 36.4 (C - 27), 34.8 (C-25), 32.3 (C -28), 31.6 (C -26), 26.2 ( C-23), 24.1 (C -24), 23.6 (C-24), 14.5 (C-33); IR (ATR): ν (cm -1 ) = 2959, 2236, 1715, 1637, 1604, 1467, 1439, 1387, 1363, 1 219, 1150, 1122, 1079, 1019, 975, 923, 862, 80 5, 647, 520 ; HRMS ( APCI) calculated for C 42 H 58 NO 5 + [M +H ] + , m/z : 656.4310; found: 656.4303. Ethyl ( E )-3- (3 -((2,4- di -tert- butyl-6- (4 -cyano-2,6-dimethylheptan-4-yl)phenoxy)methyl)-7- hydroxynaphthalen-1-yl)acrylate (16) MOM-protected compo und 14 (90 mg, 0.137 mmol, 1 eq.) was taken up in MeCN ( 4 m L ). Aque ous HCl (2 M, 1.4 m L , 20 eq.) was added to the flask and the reaction was warmed to 70 °C for 30 min. The s olvent was removed und e r reduced pressure and water (5 m L) was added. The water lay er was then ex tracted with DCM (3×10 mL). The combined organic layers were washed wit h brine (10 mL ) and dried over 7 Experim en tal Sect ion 137 Na 2 SO 4 . The solvent was removed under reduced pressure and pu rification b y column chromatogra ph y (pentane/EA = 20:1) yielde d a fairl y pu re p roduct. The product was further purified by re-cr y stalli zation from hot pentane/cy clohexane to y ield pure 16 (43 mg, 0.07 mmol, 52%) as ye llow oil. R f = 0.27 (pentane/ eth y l acetate, 6:1); 1 H-NMR (500 MHz, CDCl 3 ): δ 8.36 (d, 3 J = 16 Hz, 1H, H-28), 7.93 (s, 1H, H-9 ), 7.74 (s, 1H, H-1 ), 7.69 (d, 3 J = 9 Hz, 1H, H-7 ), 7. 40 (d, 3 J = 2 Hz, 1H, H-17 ), 7.35 (d, 3 J = 2 Hz , 1H, H-4 ), 7.33 (d, 3 J = 2 Hz, 1H, H-15 ), 7.05 (d d , 3 J = 9 Hz, 4 J = 2 Hz , 1H, H-6 ), 6.48 (d, 3 J = 16 Hz, 1H, H- 29 ), 5.08 (s, 2H, H-12 ), 4.31 (q, 3 J = 7 Hz , 2H, H-31), 2.15- 2.13 (m, 2H, H-21 ), 1.92-1.88 (m, 2H, H-21 ), 1.77-1.74 (m, 2H, H-22 ), 1.42 (s, 9H, H-27), 1.37 (t, 3 J = 7 Hz , 3H, H -32), 1.34 (s, 9H, H-25 ), 1.05 (d, 3 J = 7 Hz, 1H, H- 23 ), 0.76 (d, 3 J = 7 Hz , 1H, H-23) ; 13 C-NMR (126 MHz, CDCl 3 ): δ 167.6 (C -30), 155.1 (C -5), 153. 8 (C -13), 146.3 (C -16), 143.4 (C -18), 142.3 (C -28), 132.4 (C -10), 131.7 (C -3), 1 30.9 (C -14), 130.5 (C -7), 130.2 (C -2), 129.0 (C -8), 127.4 (C -9), 125.4 (C -17), 125.2 (C -20), 124.3 (C -15), 123. 6 (C -1), 120.0 (C -29), 118.6 (C -6), 105.6 (C -4), 76.7 (C-12), 60.8 (C-31), 51.0 (C-21), 44.8 (C -19), 36.2 (C -26), 34.7 (C- 24), 32.0 (C -27), 31.5 (C -25), 26.1 (C-22), 24.0 (C -23), 23.7 (C-23), 14. 5 (C-32); IR (ATR): ν (cm -1 ) = 2953, 2925, 2868, 2236, 1712, 1606, 1508, 1467, 1365, 1219, 117 3, 1120, 1031, 862, 831, 808, 798, 789, 754 ; HRMS (A PCI) calculated for C 40 H 53 N Na O 4 + [M + Na ] + , m/z: 634.3867; found: 634.3864. 2-Chloro-N-phenylbenzam id e (18) [ 129] The compound 17 (87 5 mg, 5.0 mmol, 1.0 eq.) was diss olved in anhy drous DCM (10 ml ), and added drop wise to a mix ture of aniline (0.46 mL, 5.0 mmol, 1.0 eq.) and Et 3 N (1.75 mL, 12.5 mm ol, 2.5 eq.) in DCM (10 ml). The resulting suspension was stirred for another 1 h. The mixture was diluted with water, and the or ganic la ye r separated. The wat er lay er was then extracted with DCM (3×25 mL). T he or ganic la yer w as washed with 1 M HCl (15 mL), 2 M NaOH (15 m L) and brine (15 m L) suc cessively, and then dried over Na 2 SO 4 . The solvent was removed under reduce d pressure and purification b y column chromatograph y (pentane/EA = 15:1) yielded a mide 18 (1.125 g, 4.85 mmol, 97%) as a colorless solid. 7.1 Synthesi s 138 R f = 0.53 (pentane/ eth yl acetate, 5:1); Mp : 118 ºC ; 1 H-NMR (400 MHz, CDCl 3 ): δ 7.93 (br s, 1H, H-8), 7.74 (dd, 4 J = 2.0 Hz, 3 J = 7.3 Hz, 1H, H-5 ), 7.65-7.63 (2H, H-10), 7.46 -7.34 (m, 5H, H-2, H-3, H-4, H-11), 7.19 -7.15 (m, 1H, H-12) ; 13 C-NMR (1 01 MHz , CDCl 3 ): δ 164.6 (C-7), 137.7 (C -9), 135.3 (C-6), 131.8 (C-2), 130.7 (C -1), 130.51 (C-3), 130.47 (C-5), 129.3 (C-11), 127.4 (C- 4), 125.0 (C-12), 120.3 (C -10) ; IR (ATR): ν (cm -1 ) = 3238, 3190, 3137, 3072, 3042, 2982, 2929, 2864, 2320, 2052, 1824, 1650,1640, 1622, 1598, 1 590, 1544, 1488, 1472, 1443, 1431, 1328, 1284, 1275, 1264, 1175, 1158, 1138, 1124, 1079, 1050, 1032, 1001, 988, 968, 953, 910, 894, 838, 830, 817, 793, 779, 759, 752, 724, 717, 691, 652, 628, 615, 588, 568, 559, 547, 532, 522, 506, 490, 484, 475, 463, 451, 446, 442, 428, 423, 419, 414, 410, 405 ; HRMS (ESI) calculated for C 13 H 11 ClNO + [M+H ] + , m/z: 232.0524; found: 232.0518. (2 -Chlorophenyl)(4-(pyrrolidin -1-yl)phenyl)methanone (19) [65] Under nit rogen atmosph ere, a solut ion of b enzamide 18 (1.125 g, 4.85 mmol, 1.00 eq.) in N-phen y lp y rrolidine (1.02 mL, 7.08 mmol, 1.46 eq.) was added in a 50 ml two -n ecked fl ask with a reflux condenser and stirred at 50 o C for 45 min. Phosphorusox ychloride (0.59 m L , 6.50 mmol, 1.34 eq.) was added dropwise to the mixture at 50 °C over a period of 50 min. The reaction mixture was then stirred at 150 o C for 5 h and then at room temperature for 16 h. After the TL C cont rol (ethyl acetate / pentane 1:10, R f = 0.63) indicated complete c onversion, the reac tion mix ture was mix ed with 50% HCl ( aq) (5.2 mL) and sti rred at 110 ° C for 3 h. After further TLC control (eth yl acetate / pentane 1:10, R f = 0.31) indicated complete conversion, water (35 ml) and NaOH (aq) solution (2 M, 6.5 ml) were added. The aqueous lay er was then extracted with DCM (3 × 15 mL ). The combined organic layers were washed with NaOH (aq) solution (0.2 M, 15 mL), HCl (aq ) solution (0.2 M, 15 mL) and water (2 × 15 m L), dried over Na 2 SO 4 and the solvent was removed under reduced pressure. Th e brown crude product w as purified b y column chromatogra ph y (eth y l a cetate / pentan e 1:10 to 1: 5) and y ielded 19 (627 mg, 2.19 mmol, 45%) as a yellow solid. R f = 0.31 (pentane/ eth y l acetate, 10:1); Mp : 118 ºC; 1 H-NMR (400 MHz, CDCl 3 ): δ 7.72-7.68 (m, 2H, H-9), 7.44-7.42 (m, 1H, H -4), 7.39 -7.30 (m, 3H, H-2, H-3, H-5), 6.52 (d, 3 J =9.0 Hz, 2H, 7 Experim en tal Sect ion 139 H-10), 3.39-3.36 ( m, 4H, H-12), 2.05-2.02 (m, 4H, H-13) ; 13 C-NMR (101 MHz, CDCl 3 ): δ 193.2 (C -7), 151.6 (C-11), 140. 1 (C-6), 132.9 (C-9), 131.2 (C -1), 130.3 ( C-2), 129.9 (C-3), 128.9 (C -5), 126.6 (C-4), 124.0 (C-8), 111.1 (C-10), 47.8 (C-12), 25.6 (C-13) ; I R (A TR): ν (cm -1 ) = 3065, 2975, 2955, 2923, 2870, 2845, 2663, 2614, 2446, 2320, 2158, 2041, 1916, 1704, 1635, 1581, 1539, 1483, 1468, 1458, 1450, 1441, 1430, 1400, 1358, 1322, 1294, 1275, 1255, 1235, 1196, 1151, 1126, 1056, 1034, 1001, 964, 952, 946, 927, 863, 826, 807, 791, 771, 750 , 738, 720, 694, 682, 638, 631, 580, 547, 539, 528, 523, 506, 494, 489, 485, 473, 466, 457, 441, 433, 429, 424, 414, 406, 402; HRMS (ESI) calculated f or C 17 H 17 ClNO + [M+H ] + , m /z : 286.0993; found: 286.0998. 1- (2 -Chlorophenyl)-1- (4 -(pyrrolidin -1-yl)phenyl)prop-2-yn-1-ol (20) [65] Under nitro gen atmosph ere, a solution of trimethylsilylace t ylene (0.35 m L , 2.41 mm ol, 1. 10 equiv.) in THF (10 m L) was added in a 50 ml three-necke d flask with an int ernal thermometer. At -10 °C, n- butyllithium (2.5 M in hex ane) (1.14 m L, 2.85 m mol, 1.30 equiv.) was added dropwise over a period of 30 min. The reaction mixture was stirred at -10 °C for 1 h. Then 2-chloro -4-pyrrolidinobenzophenone ( 17 ) (627 mg, 2.19 mmol , 1.00 equiv.) dissolved in abs. THF (4 ml) was added in one portion. The reaction mixture was stirred at room temperature for 4 h. A fter the TLC control (eth y l acetate / c y clohexane 1:5, R f = 0.53) indicated complete conversion, the reaction mixture was cooled to 0 °C. Then KOH (246 mg, 4.38 mmol, 2.00 equiv.) dissolved in methanol (2.5 mL ) w as added a nd the mixture was stirred at room temperature fo r 45 min. After further T LC c ontrol (ethy l acetate / cyclohexane 1:5, R f = 0.35) indicated complete dep rotection, the reaction mi xture was n eutralized to pH ~ 7 with acetic acid (0.50 ml) and water (40 ml) was added. The mixture were separ ated and the aqueous la y e r was extracted with ethy l acetate (3 × 50 ml). The combined organic layers were washed with water (2 × 30 ml) and b rine (30 mL) , and dried over Na 2 SO 4 . The solvent was removed under redu ced pressure and purification by column chromatograph y yielded product 18 (587 mg, 1.88 mmol, 86%) as a grey solid. R f = 0.35 (c y clohexane/ ethyl acetate, 10:1); Mp : 113 ºC; 1 H -NMR (400 MHz, CDCl 3 ): δ 8.04- 8.01 (m, 1H, H-3), 7.38-7 .35 (m, 4H, H-2, H-4, H-12), 7.32-7.28 (m, 1H, H-5), 6.54 (d, 3 J =8.5 Hz, 2H, H-13), 3.33-3.30 (m, 4H, H-15), 3.06 (s, 1H, H-8), 2.87 (s, 1H, H-10), 2.04-2.00 (m, 4H, H- 7.1 Synthesi s 140 16) ; 13 C-NMR (101 MH z, CDCl 3 ): δ 147.7 (C-14), 141.0 (C-6), 132.6 (C-1), 131.3 (C-2), 129.6 (C -11), 129.2 (C-3), 128. 1 (C -5), 127.7 (C-12, C-12´), 126.6 (C-4), 111.2 (C-13), 85.0 (C-9), 75.0 (C -10), 73.6 (C-7), 47.7 ( C-15), 25.6 (C-16 ) ; IR (ATR): ν (cm -1 ) = 3237, 29 64, 2950, 2876, 2830, 2324, 2112, 2049, 1980, 1895, 1802, 1608, 1570, 1511, 1486, 1465, 1441, 1432, 1402, 1358, 1313, 1286, 1256, 1210, 1181, 1158, 1141, 1130, 1113, 1061, 1038, 1019, 991, 948, 939, 904, 860, 827, 817, 792, 785, 756, 736, 730, 719, 677, 643, 618, 591, 583, 568, 562, 549, 532, 518, 510, 506, 502, 486, 477; HRMS (ESI) calculated for C 19 H 19 ClNO + [M+H ] + , m/z: 312.11 50; found: 312.1144. 2-(3,5-Di-tert-butyl-2-((6-hydroxynaphthalen -2 -yl)methoxy)phenyl)-2-isobutyl-4- methylpentanenitrile ( 23 ) MOM-protected 13 (737 mg, 1.32 mmol, 1 eq.) was taken up in MeCN (35 m L ). Aq ueous HCl (2 M, 13.2 mL, 20 eq.) was added to the flask and the reaction was warmed to 70 °C for 30 min. The solvent was removed under reduce d pressure and water (10 m L) was added. The aqueo us la y er was then extracted with DCM (3×15 mL). Th e organic layer was washed with brine and dried over Na 2 SO 4 . The solvent was removed under reduced pressure and purification b y column chromatography (pent ane/EA = 20:1) to y ield a fairly pure product. The product was fur ther purified b y re-c ry stallization from hot p entane/cyc lohex ane to y i eld pure 23 (375 m g, 0.73 mmol, 55%) as white-y ellow crystals. R f = 0.69 (pentane/ eth y l ace tate, 5:1); Mp : 156 ºC; 1 H-NMR (400 MHz, CDCl 3 ): δ 7.86 (s, 1H, H-5 ), 7.71 (d, 3 J = 8.6 Hz , 1H, H-3 ), 7.65 (d, 3 J = 8 .5 Hz, 1H, H- 8), 7.47 (d d, 3 J = 8.5 Hz, 4 J = 1.6 Hz , 1H, H-7 ), 7.40 (s, 2 H, H-17, H-15 ), 7.06-7.03 (m, 2H, H-2, H-10 ), 5.31 (br, 1H, H-11, OH ), 5.05 (s, 2H, H-12 ), 2.19- 2.17 (m, 2H, H-21 ), 1.88-1.84 (m, 2H, H-21 ), 1. 77 - 1.69 (m, 2H, H-22 ), 1.43 (s, 9H, H-27), 1.34 (s, 9H, H-25), 1.03 (d, 3 J = 6.6 Hz , 6H, H-23 ), 0.75 (d, 3 J = 6.6 Hz, 6H, H-23) ; 13 C-NMR (126 MHz, CDCl 3 ): δ 153.9 (C -13), 153.8 (C -1), 146. 2 (C -16), 143.4 (C -18) , 134.1 (C -9), 132.2 (C -6), 1 30.7 (C -14), 129.7 (C - 3) , 128.7 (C -4), 126.7 (C - 8) , 125.5 (C -17), 125.3 (C -20), 124.7 (C -5), 124.5 (C -7, C-15), 118.2 (C -2), 109.5 (C -10), 76.9 (C -12), 50.7 (C -21), 45.3 (C -19), 36.3 (C -26), 34.7 (C -24), 32.1 (C -27), 31. 5 (C -25), 26.1 (C -22), 24.0 (C -23), 23.7 (C -23); IR (ATR): ν (cm -1 ) = 336 5, 2957, 2241, 1738, 160 8, 1468, 1446, 1387 1375, 1271, 1238, 1223, 7 Experim en tal Sect ion 141 1203, 1146, 1125, 1048, 1023, 882, 851, 812, 734, 649, 553 ; HRMS (APCI) calculated for C 35 H 48 NO 2 + [M +H ] + , m/ z: 514.3680; found: 514.3669. 1,1-Bis(4-fluorophenyl)prop-2-yn-1-ol (25) [58] A 500 mL Schlenk fl ask was flame dried i n vacuo . T hen 4,4’ - difluorobenzophenone 24 (15.0 g, 68.7 mm ol, 1 eq.) and 137 mL TH F were added under nitrogen atmosphere. Afterwards, a solution of 230 mL 0.6 M ethy n y lmagnesium chloride (138 mmol, 2 eq.) w as add ed dropwise within 12 h. After complete addition, the reaction mixture was stirred for further 74 h at r.t. until TLC monitoring indicated a complete conversion of the starting material. The solution was diluted with 500 mL dieth y l ether and carefully h y d rolysed with a satura ted NH 4 Cl solution (200 mL). The separated aqu eous layer was ex tracted with di ethyl ether (3 × 300 mL). The combined organic layers wa s washed with b rine (200 mL), dried over Na 2 SO 4 a nd concentra ted in vacuo. The crude product was purified b y column chromatography (pentane/dichloromethane, 1/5) and y ielded alcohol 25 (13.1g, 53.8mmol, 78%) as pale y ellow oil . R f = 0.48 (pentane / dichloromethane, 5:1); 1 H-NMR (400 MHz , CDCl 3 ): δ 7.58-7.53 (m, 4H, H- 2), 7.04-7.00 (m, 4H, H -3), 2.90 (s, 1H, H-7 ), 2.8 0 (s, 1H, H-8) ; 13 C-NMR (101 MHz , CDCl 3 ): δ 162.5 (d, 1 J C-F = 247.3 Hz, C -4), 140.3 (d, 4 J C-F = 2.9 Hz, C -1), 128.0 (d, 3 J C-F = 8.2 Hz , C -2), 115.3 (d, 2 J C-F = 21.0 Hz, C -3), 86.1 (C-6), 76.1 (C-7), 73.5 (C-5) ; IR (ATR): ν (cm -1 ) = 3418, 3299, 3074, 2116, 1896, 1602, 1503 1410, 1322, 1300, 1220, 1189, 1156, 988, 903, 831; HRMS (ESI) calculated f or C 15 H 11 F 2 O + [M+H ] + , m/z: 2 45.0772; found: 245.0776. 7.1 Synthesi s 142 2-(3,5-Di-tert-butyl-2-((3- (2 -chlorophenyl)-3- (4 -(pyrrolidin-1-yl)phenyl)-3H- benzo[f]chrome n-8-yl)methoxy)phenyl)-2-isobu tyl-4-methylpentanenitrile (N4) In a 50 m L two -neck flask with reflux condenser, prop argyl alcohol 20 (156 m g, 0.5 mmol, 1.00 eq .), compound 23 (2 57 mg, 0.5 mmol, 1.00 eq.), freshl y distilled toluene (6.5 mL) were added under nitrogen atmosphere. At 50 °C, Aluminium oxide (Sigma Aldrich, activated, acidic, Broc kman I, pore size 58 Å) (393 mg, 3.85 mmol, 7.70 eq.) wa s added. The reaction mixture was sti rred at 1 10 °C for 1.5 h. After complete conv ersion det ectable b y th e thi n la y er ch romatography (TLC) mo nitoring (eth y l acetate / pentane 1 /2 0, R f = 0. 76 ), the re action mix ture was filtered and w ashed with hot toluene (2 × 10 ml). The solvent was removed under r educe d pressure to afford the dar k green crude product. Af ter purification b y column chromatography (silica, eth yl a cetate / pentane 1:1 00 ), the naphthopyran N4 (222 mg, 0.275 mmol, 55%) was obtained as a dark blue solid. R f = 0.76 (pentane/ ethy l acetate , 20:1); Mp : 130 ºC; 1 H-NMR (500 MHz, CD 3 CN): δ 8.03 (d, 3 J = 8.8 Hz , 1H, H-11), 7.89-7.88 (m, 2H, H-8, H- 15 ), 7.70 (d, 3 J = 8.8 Hz, 1H, H-6), 7.61 (d d, 3 J = 8.8 Hz, 4 J = 1.7 Hz , 1H, H-10), 7.45 (d, 4 J = 2.4 Hz, H-30), 7.38 (d, 3 J = 9.9 Hz, H-1), 7.38-7.36 ( m, 2H, H-28, H-18), 7. 33 -7.25 (m, 2H, H -16, H-17), 7.18-7.16 (m, 3H, H -20, H-5), 6.60 (d, 3 J = 9.9 Hz , 1H, H-2), 6.46 (d, 3 J = 8.9 Hz , 2H, H-21 ), 5.05 (s, 2H, H-25 ), 3.20-3.18 (m, 4H, H-23), 2.18-2.14 (m, 2H, H -34), 1.94-1.92 (m, 4 H, H-24), 1.87-1.82 (m, 2H, H -34), 1.67-1.62 (m, 2 H, H - 35 ), 1.39 (s, 9H, H -40 ), 1.32 (s, 9H, H-38 ), 0.98 (d, 3 J = 6.7 Hz , 6H, H- 36 ), 0.72 (d, 3 J = 6.7 Hz , 6H, H-36 ); 13 C-NMR (1 26 MHz, CD 3 CN ): δ 154 .7 (C -26), 151.2 (C -4 ), 1 48.7 (C-22 ), 147. 1 (C- 29), 144.1 (C -31 ), 142.3 (C -13), 134.0 (C-9), 132. 4 (C -18), 132.3 (C-7 ), 132.1 (C -27), 130.6 (C - 6), 130.1 (C-16), 130.0 (C -14), 129.8 (C -12), 129.7 (C -15), 129.4 (C -19), 129.3 (C -20), 127.5 (C - 17), 127.2 (C -2), 126.4 (C -8), 126.2 (C -30, C-10 ), 126.1 (C -33 ), 125.3 (C -28 ), 122.5 (C -11 ), 120.9 (C -1 ), 119.3 (C -5), 115.4 (C -13 ), 111.8 (C -21), 83 .5 (C -3), 7 7.7 (C -25), 51 .3 (C -34), 4 8.2 (C -23), 45.4 (C -32), 36.7 (C -39), 35.2 (C -37), 32.1 (C -40), 31.5 (C -38), 26.8 (C -35), 26.0 (C -24), 24.0 (C - 36 ), 23.7 (C -36 ); IR (ATR): ν (cm -1 ) = 2958, 2869, 2231, 1610, 1520, 1467, 1435, 1374, 1268, 7 Experim en tal Sect ion 143 1219, 1178, 1122, 1087, 1052, 1000, 929, 884, 814, 778, 755 ; HRMS ( APCI) ca lculated for C 54 H 64 Cl N 2 O 2 + [M +H ] + , m/z: 807.4651; found: 807.4649. 2- (2 -((3,3-Bis(4-fluorophenyl) -3H-benzo[f]chrom en-8-yl)methoxy)-3,5- di -ter t-butylphenyl)- 2-isobutyl-4-methylpentanenitrile ( N6 ) A 50 m L S chlenk flask w as flame dried in vacuo a nd naphtho l 23 (257 g, 0.5 mm ol, 1.0 eq.), p y ridini um tosy late (6.25 mg, 0.025 mmol, 5 mol%) and 12 mL DCE were added under nitrogen atmosphere. The suspension was heated to reflux. Then trimethy l orthoformate (109 µ L, 1. 0 mmol, 2.0 eq.) was added in a single portion. To thi s mixture the propargy l alcohol 25 (171 m g, 0.7 mmol, 1.4 eq.) was added dropwise via s y rin ge. The mi xture was hea ted to reflux for 48 h until TLC monitoring indicated compl ete consumption of the starting m aterial. The brown solution was cooled to r.t. a nd diluted with 10 mL dichlorometha ne. The organic la yer was washed with water (3× 10 mL) and with brine (10 mL), dried over Na 2 SO 4 and concentra ted in vacuo. After purification b y column ch romatography (silica, eth y l acetate / pentan e 1: 25), the naphthopyran N6 (300 mg, 0.405 mmol, 81%) was obtained as a pearl-white solid. R f = 0.91 (pentane/ ethyl acetate, 5:1); Mp : 93.1-94.5 ºC; 1 H-NMR (500 MHz, CDCl 3 ): δ 7.98 (d, 3 J = 9 Hz , 1H, H-11), 7.8 1 (d, 4 J = 1.5 Hz , 1H, H-8), 7.69 (d, 3 J = 8.5 Hz, 1H, H-6), 7.56 (d d, 3 J = 9 Hz , 4 J = 1.5 Hz , 1H, H-10), 7.46-7.42 (m, 2 × 2 H, H-15), 7.41-7.39 (m, 2H, H-21, H -23), 7.33 (d, 3 J = 10 Hz, 1H, H-1), 7.18 (d, 3 J = 8.5 Hz, 1H, H-5), 7.03 -6.98 (m, 2 × 2H, H-16), 6.18 (d , 3 J = 10 Hz , 1H, H-2), 5.02 (s, 2H, H-18 ), 2.22-2.09 (m, 2H, H-27), 1.85-1.81 (m, 2H, H-27), 1.75- 1.67 (m, 2H, H-28 ), 1.40 (s, 9H, H-33 ), 1.33 (s, 9 H, H-31 ), 1.01 (d, 3 J = 6. 5 Hz , 6H, H-29 ), 0.73 (d, 3 J = 6.5 Hz , 6H, H -29); 13 C-NMR (1 26 MHz , CDCl 3 ): δ 162.3 (d, 1 J C-F = 247.0 Hz, C -17), 153.8 (C -19), 150.3 (C-4), 146.1 (C-22), 143.3 (C -24), 140.6 (d, 4 J C-F = 3.0 Hz, C -14), 133.0 (C- 9), 130.6 (C-26), 130.3 ( C-6), 129.4 (C-7), 129.2 (C -12), 129.0 (d, 3 J C-F = 8.2 Hz , C-15), 127.5 (C - 2), 125.5 (C -23 ), 125.4 ( C-8), 125.3 (C -20), 125. 1 (C -10), 124.9 (C -21), 1 21.7 (C -11), 120.1 (C- 1), 118.5 (C-5), 115.2 (d, 2 J C-F = 21.2 Hz, C-16 ), 114.1 (C -13), 81.9 (C-3), 76.7 (C -18), 50.3 (C - 7.1 Synthesi s 144 27), 45.7 (C -25), 36.2 (C -32), 34.7 (C -30), 32.2 (C -33), 31.5 (C-31), 26. 1 (C-28), 24.0 (C-29), 23.5 (C -29); IR (ATR): ν (cm -1 ) = 2954, 2866, 2232, 1601, 1507, 1467, 1362, 1272, 1222, 1157, 1107, 1087, 1006, 963, 886, 834, 817, 727, 650, 551 ; HRMS (APCI) calculated for C 50 H 56 F 2 NO 2 + [M +H ] + , m/z: 740.4274; found : 740.4272. Ethyl (E)-3- (8 -((2,4- di -tert-butyl-6- (4 -cyano-2,6-dimethylheptan-4-yl)phenoxy)methyl)-3,3- bis(4-fluorophenyl)-3H-benzo[f]chromen-6-yl)acrylate (N7) A 10 m L s ealed tube (with a Teflon cap) w as flame dried and naphthop yran N6 (74 mg, 0.10 mmol, 1.0 equiv.), Pd(OPiv) 2 (3.4 mg, 0.010 mmol, 10 mol%), A gOPiv (62 .7 mg, 0.30 mmol, 3.0 equiv.), ethyl acrylate (22 µ L , 0.20 mmol, 2.0 equiv.) were added. DCE (1.0 mL) was used t o wash down the soli ds on the sides of the tube wall. The tube was then capped and subme rged into a prehea ted 100 °C oil bath. The oil bath was covere d with aluminum foil to stabilize the oil bath temperature and to shield the reaction from light. After one day of stirring, the tube was shaken manually to dislodge the silver salt off the sides of the wall. The reaction was sti rred for a total of 48 h and cooled down to room temperature. The reaction mixture was filtered through a pad of Celite and wash ed wit h EA (3 × 3 m L). The solvent was removed under reduced pressure and purified b y column chromatography (pentane/ EA , 100/1 ) to y ield naphthop y ran N7 (15 mg, 0.017 mmol , 17%) as a ye llow soli d. R f = 0.69 (pentane/ EA , 20:1); Mp : 80-81.4 ºC; 1 H -NMR (500 MHz, CDCl 3 ): δ 8.39 (d, 3 J = 16 Hz , 1H, H-14 ), 8.16 (s, 1H, H-8), 8.05 (d, 3 J = 9 Hz , 1H, H-11), 7.68 (d d, 3 J = 9 Hz, 4 J = 1.5 Hz , 1H, H-10), 7.46 (s, 1H, H-5), 7.45-7.41 (m, 2 × 2 H, H-20), 7.39-7.34 (m, 3H, H-1, H-26, H-28), 7.05-6.98 (m, 2 × 2H, H- 21), 6. 50 (d, 3 J = 16 Hz, 1H, H-15), 6.25 (d, 3 J = 10 Hz , 1H, H-2), 5.08 (s, 2H, H-23 ), 4.27 (q , 3 J = 7 Hz , 2H, H-17), 2.17 -2.09 (m, 2H, H-31 ), 1.8 6-1.81 (m, 2H, H-31 ), 1.73-1.68 (m, 2H, H-32 ), 1.42 (s, 9H, H-38 ), 1.35-1.32 (m, 12H, H-18, H-36 ), 1.02 (d, 3 J = 6.5 Hz , 6H, H-33 ), 0.73 (d, 3 J = 6.5 Hz , 6H, H -33); 13 C- NMR (1 26 MHz, CDCl 3 ): δ 166.7 (C -16), 162.4 (d, 1 J C-F = 248.2 Hz, C -22), 153.8 (C -24), 149.7 (C -4), 146.3 (C-27 ), 143. 3 (C -29), 140.7 (C -14), 7 Experim en tal Sect ion 145 140.3 (C-19), 134.0 (C-9), 133.9 (C-6), 130.8 (C- 34), 129.6 (C-12), 129.0 (d, 3 J C-F = 7.5 Hz, C- 20), 128.9 (C-2), 127.7 (C -7), 125.6 (C -28), 125. 5 (C-10 ), 125.4 (C -25 ), 124.7 (C -26), 122.4 (C - 11), 121.7 (C -15), 120.9 (C-8), 119.9 (C-1), 117.1 (C-5), 116.4 (C-13), 115 .3 (d, 2 J C-F = 21.4 Hz, C-21), 82.0 (C-3), 76.9 (C-23), 60.7 (C-17), 50.7 (C-31), 45.4 (C-30), 36.3 (C -37), 34.8 (C-35), 32.1 (C-38), 31.5 (C -36 ), 26.1 (C -32), 24.0 (C-33) , 23.6 (C-33), 14.5 (C-18 ); IR (ATR): ν (cm -1 ) = 2957, 2869, 2232, 171 3, 1633, 1589, 1537, 1507, 1468, 1440, 1396, 1 363, 1300, 1273, 1227, 1158, 1124, 1054, 1032, 1006, 928, 864, 828, 750, 683, 637, 581 ; HRMS (A PCI) calculated for C 55 H 62 F 2 NO 4 + [M +H ] + , m/z: 838.4641; found: 838.4631. Methyl 3- (2 -chlorophenyl)-3- (4 -(pyrrolidin -1-yl)phenyl)-3H-benzo[f]chromene-8- carboxylate ( N1 ) In a 250 mL two -neck flask with reflux condenser, propargy l alcohol 20 (4.00 g, 12.8 mmol, 1.00 eq .), methy l 6-hydrox y -2- naphthoate (2.59 g, 12.8 mmol, 1.00 eq.) in freshly distilled toluene (160 ml) were a dded under nitrogen atmosphere. At 50 °C, Aluminium oxide (Sigma Aldrich, activated, acidic, Broc kman I, pore siz e 58 Å) (10.07 g, 98.8 mmol, 7.70 eq.) was added. The reaction mixture was stirred at 110 °C for 1.5 h. After complete co nversion detectable b y th e thin la yer chromatogra ph y (T L C ) monitoring (eth y l acetate / pentane 1/10, R f = 0.51), the reaction mi xture was filtered and washed with hot toluene (2 × 50 ml). The solvent was removed under reduced pressure to afford the dark green c rude pro duct (5. 21 g). A fter pu rification b y column chromatogra ph y (sili ca, ethyl acetate / pentane 1: 10), the naphthop yran N1 (3.41 g, 6.88 mmol) was obtained a s a dark bl ue solid in a y ield of 54%. R f = 0.32 (eth y l acetate / pentane , 1:10); Mp : 111 °C ; 1 H-NMR (400 MHz, CDCl 3 +D 2 O): δ 8.46 (s, 1H, H-10), 8.03 (dd, 3 J = 8.8 Hz, 4 J = 1.9 Hz, 1H, H-8), 7.97 (d, 3 J = 8.8 Hz , 1H, H-7), 7.80 (dd, 3 J = 7.6 Hz, 4 J = 1.9 Hz, 1H, H-20), 7.75 (d, 3 J = 8.9 Hz, 1H, H-12), 7.35 (dd, 3 J = 7.2 Hz, 4 J = 2.0 Hz, 1H, H-17), 7 .29 (d, 3 J = 10.2 Hz, 1H, H-4), 7.28-7.19 (m, 5H, H-13, H -18, H-19, H- 22), 6.62 (d, 3 J = 10.1 Hz, 1H, H-3), 6.49 (d, 3 J = 8.7 Hz, 2H, H-23), 3.96 (s, 3H , H-28), 3.27-3.2 4 (m, 4H , H-25), 1.97-1.94 (m, 4H, H -26); 1 H-NMR (400 MHz, MeCN- d 3 ): δ 8.45 (d, 4 J = 1.6 Hz , 7.1 Synthesi s 146 1H), 8.04 (d, 3 J = 9.0 Hz, 1H), 7.98 (dd, 3 J = 8.9 Hz , 4 J = 1.8 Hz, 1H), 7.8 5-7.82 (m, 2H), 7.38- 7.36 (m, 1H), 7.34 (d, 3 J = 10.6 Hz, 1H, H -4), 7.32-7.25 (m, 2H), 7.22 (d, 3J = 8.9 Hz, 1H), 7.16- 7.12 (m, 2H, H-22), 6.60 (d , 3 J = 10.1 Hz, 1H, H- 3), 6.45-6.42 (m, 2H, H-23), 3 .90 (s, 3H, H-28), 3.18-3.15 (m, 4H, H-25), 1.93 -1.90 (m, 4H, H-26 ); 13 C-NMR (101 MHz, CDCl 3 +D 2 O): δ 167.5 (C -27), 152.6 (C-14), 14 7.6 (C-24), 141.5 (C-15), 132.3 (C-6), 131.9 (C-16), 131.8 (C-10), 131.7 (C -17), 131.3 (C-12), 129.2 (C -21), 129.0 (C-18, C-20), 128.6 (C-22), 128.4 (C-11), 126.5 (C-19), 126.13 (C-8), 126.10 (C-3), 125.1 (C-9), 121.7 (C -7), 119.4 (C-4), 119.3 (C-13), 113.9 (C-5), 83.5 (C -2), 52.3 (C-28), 47.6 (C-25), 25.5 (C-26); IR: ν (cm -1 ) = 3061, 2946, 2926, 2843, 1713, 1608, 1587, 1519, 1485, 1466, 1433, 1373, 1338, 1278, 1245, 1208, 1178, 1161, 1125, 1106, 1082, 1051, 1039, 998, 965, 920, 865, 807, 752, 710, 698, 676, 660, 633, 620, 579, 568, 552, 518; HRMS (ESI): calculated for C 31 H 27 ClNO 3 [ M+H] + : 496.1674; found: 496.1669; 3- (2 -Chlorophenyl)-3- (4 -(pyrrolidin -1-yl)phenyl)-3 H -be nzo[ f ]chromene-8-carboxylic acid ( N2 ) Under nitrogen atmosphere, the naphthop yran N1 (336 mg , 0.68 mmol.) in abs. tetra hydrofuran (100 m L) and potassium trimethylsilanolate (262 mg, 2.43 mmol.) were added. The reac tion mixture wa s st irred for 22 h a t room temperature. Although the TLC analysis (he xane/eth y l a cetate = 1/1) indicated no complete conversion at thi s time, the s olvents were removed under reduced pressure. The residue was dissolved in dichloromethane, w ater was added and the pH was adjusted to pH = 3 with a KHSO 4 (aq) solut ion (0.1 M). Th e l ayers were then separated and the a queous la y er extracted with dichloromethane (2 × 50 m L). The combined orga nic layers were dried (Na 2 SO 4 ) and the solvents removed under reduced pre ssure to afford c rude product. After purification b y column chromatography (sili ca, hexane / eth y l acetate = 1 /1), the naph thopyra n N2 (142 mg, 0.30 mmol, 44%) was received as a purple solid. R f = 0.47 (hexane / eth y l acetate, 1:1); Mp. 310 °C ; 1 H-NMR (500 MHz, DMSO- d 6 ): δ 8.33 (s, 1H, H-10), 8.05 (dd, 3 J = 8.7 Hz, 4 J = 1.3 Hz, 1 H, H -8), 7.97 (d, 3 J = 8.8 Hz, 1H, H-7 ), 7.80 (d, 3 J = 8.9 Hz, 1H, H-12), 7.75 (dd, 3 J = 7.7 Hz, 4 J = 1.8 Hz, 1H, H-20), 7.47 (d, 3 J = 10.3 Hz, 1H, 7 Experim en tal Sect ion 147 H-4), 7.41 (dd, 3 J = 7.6 Hz, 4 J = 1.4 Hz, 1H, H-17), 7.35 (td, 3 J = 7.5 Hz, 4 J = 1.6 Hz, 1H, H-19 ), 7.31 (td, 3 J = 7.5 Hz, 4 J = 1.9 Hz, 1H, H- 18), 7.17 (d, 3 J = 8.8 Hz, 1H, H-13), 7.12 (d, 3 J = 8.8 Hz, 2H, H-22), 6.55 (d, 3 J = 10.1 Hz, 1H, H-3), 6.46 (d, 3 J = 8.6 Hz, 2H, H-23), 3.18-3.16 (m, 4H, H- 25), 1.92-1.89 (m, 4H H -26); 13 C-NMR (126 MHz, DMSO - d 6 ): δ 170.2 (C-27), 150.1 (C-14), 147.0 (C-24), 141.2 (C-15), 134.9 (C-9), 131.4 (C-17), 130.9 (C-16), 130.8 (C -12), 129.8 (C-6), 129.3 (C-18), 129.2 (C-10), 128.6 (C-20), 128.5 (C-21), 128.3 (C-11), 128.2 (C-8), 128.0 (C-22), 126.7 (C-19), 125.5 (C-3), 120.2 (C-7), 119.9 (C -4), 117.6 (C-13), 113.4 (C-5), 111.0 (C-23), 82.2 (C -2), 47.1 (C-25), 24.9 (C-26); IR (A TR): ν (cm -1 ) = 3062, 2928, 1694, 1610, 1609, 1558, 1520, 1467, 1378, 1362, 1329, 1271, 1244, 1222, 1179, 1125, 1084, 1052, 1040, 1000, 966, 925, 868, 809, 754, 710; HRMS (ESI) calculated for C 30 H 24 ClNO 3 [M+H] + : 482.1517, found: 482.1502. (3 - (2 -Chlorophenyl)-3- (4 -(pyrrolidin-1-yl)phenyl)-3 H -benzo[ f ]chromen-8-yl) m ethanol (N3) In a 100 m L thre e-necked flask with internal thermometer, naphthopyran N1 (1.20 g, 2.42 mmol, 1.00 eq.) was dissolved in dichloromethane (22 mL) under nitrogen atmosphere and cool ed to -78 °C with dr y ice. A solution of D I BA L-H in toluene (20% w, 6.90 mL, 8.47 mmol, 3.50 equiv.) was added t o thi s reaction solution dropwise over a period of 60 min. After completion of the addition, the reaction mixture was sti rred at -78 °C for an additional 1 h, until TLC (eth y l acetate / pentane, 1: 5, R f = 0.07) showed complete conversion. Then eth yl acetate (55 m L) was added c autiously at -78 °C to destroy residues o f unr eacted DIBAL-H. The reaction mixture was warmed to room temperature and then dil uted with dichloromethane (150 m L) and washed with sa turated NaCl solution (300 mL). The aqueous l ayer was extracted with dichloromethane (6 x 100 ml). The combined organic la y ers were wash ed with water (100 ml ), d ried over MgSO 4 and the solvent removed under reduce d pressure. After p urification b y column chr omatography (silica, eth yl acetate / pentane 2/5), the product N3 (592 mg, 1.26 mmol) was obtained as a dark blue solid in a y i eld of 52%. R f = 0.26 ( ethyl acetate/pentane, 2:5); Mp : 120 o C; 1 H-NMR (400 MHz , DMSO- d 6 ): δ 8.05 (d, 3 J =8.8 Hz, 1H, H-11), 7.77-7.72 (m, 3H, H-8, H-14, H-25), 7.48-7.45 (m, 2H, H-4, H-12), 7.42- 7.1 Synthesi s 148 7.39 (m, 1H, H -28), 7.37-7.29 (m, 2H, H-26, H-27), 7.18 (d, 3 J =8.8 Hz, 1 H, H -7), 7.12-7.09 (m, 2H, H-18, H-18´), 6.56 ( d, 3 J =10.1 Hz, 1H, H-3), 6.44 (d, 3 J =8.8 Hz, 2H, H-19, H-19 ´), 5.27 (t, 3 J =5.7 Hz, 1H, H-16), 4.61 (d, 3 J =5.6 Hz, 2H, H - 15), 3.17 -3.14 (m, 4H, H-21, H-21´), 1.91-1.88 (m, 4H, H-22, H-22´) ; 13 C-NMR ((101 MHz, DMSO- d 6 ): δ 149.5 (C -6), 147.0 (C-20), 141.2 (C- 24), 138.0 (C-13), 131.4 (C-26), 130.9 (C-23), 12 9.7 (C-25), 129.3 (C-8), 128.8 (C-10), 128.6 (C- 28), 128.5 (C-17), 128.3 (C -9), 128.0 (C-18, C- 18´), 126.7 (C-27), 126. 2 (C -12), 125.7 (C-3), 125.1 (C-14), 121.4 (C -11), 119.9 (C-4 ), 117.9 (C -7), 113.7 (C-5), 110.9 ( C-19, C-19 ´), 82.1 (C- 2), 62.8 (C-15), 47.1 (C-21, C-21´), 24.9 (C-22, C-22´); IR: ν (cm -1 ) = 3332, 3061, 2836, 2320, 2161, 2047, 2022, 1901, 1608, 1520, 1484, 1469, 1432, 1373, 1287, 1268, 1244, 1222, 1177, 1126, 1086, 1039, 1011, 998, 9 66 , 929, 886, 841, 814, 7 80, 754, 709, 655, 636, 612, 604 , 594, 584, 578, 556, 552, 544, 527, 521, 516, 511; HR -MS (ESI): calculated for C 30 H 27 ClNO 2 [M+H] + : 468.1721; found: 468.1725. Dimethyl 2- ((6 -methylpyridin -3-yl)methylene)m alonate (ligan d 1) [111] A 10 mL Schlenk t ube was flame dried in vacuo and 6 - methylnicotinaldehy de (69.1 µ L, 0.6 mmol, 1.0 e q.), dimeth y l malonate (73.5 µL, 0.63 mm ol, 1.05 eq.), piperidine (9 µL, 0.09 mmol, 0.15 eq.), acetic acid (5.2 µL, 0.09 mmol, 0.15 eq.), 3 mL toluene were added under nitroge n atmosphere. Th e reaction mixture was stirred at 110 °C for 16 h. Then the reaction was cooled down to room tempera ture and afterwards piperidine (6 µ L, 0.06 mmol, 0.1 eq.), acetic acid (3.4 µ L , 0.06 mmol, 0.1 eq.) w ere added under nitrogen atmosphere. The reaction mix ture was stirred at 110 °C for additional 2 h. Afterwards the mi xture was cooled down to room temperature and diluted with dichloromethane, wash ed with water (10 m L). Th e or ganic la y er w as dried (Na 2 SO 4 ) and the solvent s were removed und er re duced pr essure to a fford the crud e product. A fter purification b y column chromatograph y (silica, eth y l acetate / pentane 1/2), the ligand 1 (63.5 mg, 0.27 mmol, 45%) as a white solid was received. R f = 0.55 ( eth y l acetate/pentane, 5:2); Mp : 88 o C; 1 H-NMR (500 MHz, CD Cl 3 ): δ 8.54 (d, 3 J = 2 Hz , 1H, H-6), 7.71 (s, 1H, H-8), 7.64 (d d, 3 J = 8 Hz, 4 J = 2 Hz , 1H, H-4), 7.19 (d, 3 J = 8 Hz , 1H, H-3), 3.86 (s, 3H, H-11 ), 3.85 (s , 3H, H-11 ), 2.59 (s, 3H, H-7 ); 13 C-NM R (1 26 MHz, C DCl 3 ): δ 166.7 (C -10), 164.2(C-10), 160.8 (C -2), 150.1 (C-6), 139.4 (C-8), 136.3 (C -4), 126.8 (C -9), 126.2 (C -5), 123.6 (C -3), 52.9 (C-11), 24.5 (C-7); I R: ν (cm -1 ) = 3005, 2955, 2921, 2853, 1724, 1632, 7 Experim en tal Sect ion 149 1593, 1560, 1491, 1463, 1443, 1401, 1360, 1307, 1248, 1223, 1197, 1186, 1161, 1142, 1066, 1028, 982, 969, 774, 763, 728, 706, 669, 645, 597, 555, 534, 505; Pr ocedure for nondirected C -H functionalization of compound 3 A 10 m L Schlenk tub e was flame dried i n vacuo and Pd(OA c) 2 (4.5 mg , 0.02 mmol, 10 mol% ), ligand 1 (9.4 mg , 0.04 mmol, 20 mol% ), N -acet y l gl y cine ( 7.0 mg , 0.06 mmol, 30 mol% ), AgOAc (100.2 mg, 0.6 mmol, 3.0 eq.), compound 3 (49.3 mg , 0.2 mmol, 1.0 eq. ), ethy l acrylate (65.3 µL, 0.6 mmol, 3.0 eq.), 2 mL HFI P were a dded under nitrogen a tmosphere. The tube w as then c apped and submerged into a pr eheated 90 °C oil bath. The oil bath was covered with aluminum foil to stabilize the oil bath temperature and to shield the reac tion from li ght. The reaction was stirred for a total of 24 h and then cooled down to room temperature. The solvent w as removed under reduced pressure and purified b y column chromatog raphy but the mixture of 5 products could not be separa ted. 7.2 UV/Vis Ab s orption S pectrosco py 150 7. 2 UV /V is Absorption Spect roscopy 7.2.1 General Information The set-up of UV/Vis spectroscop y measurements is display ed in Fi gure 7.1. All the experiments were carried out with an Avantes AvaSpec Dual- channel Fibe r Optic Spectrometer , which was equipped with the Ava L i ght- DH -S-BAL light sou rce ( Figure 7.1-1). A cu vette (10 mm, Quartz, Suprasil, Hellma Anal y ti cs) was applied to the experiments (Fi gure 7.1-3). All the LED lights used in this work were bou ght from Thorlabs (Figure 7.1-5). All th e absorption spectra were measured at 273 K in this work unless mentioned specially . Additional air stream cooling was emplo y e d (Figure 7.1 -7), du e to the low efficienc y of the t emperature regulator (Figure 7.1 -6) for cooling down the sample in the sample holder. Figure 7.1 The device o f UV/V is experim ents: 1) light source; 2) optical fib er in com posit e pipe; 3) cuvette hold er (equipp ed with a m agnetic stirrer below); 4 ) detecto r; 5) LED lig hts; 6) temperatu re regulator; 7) air stream cooling (picture f rom the PhD thesis of Marina Vlac jić ). 7 Experim en tal Sect ion 151 Figure 7.2 Em iss ion sp ectra of LED lights u sed in thi s work ( provided by T horlab s) . The emission spectra of LED li ghts are ex hibited in Fig ure 7.2. Furthermore, the light intensities of LED lights were detected by a Photom eter International Light IL 1400 . Therein, for the room temperature UV/Vis measurements, the y wer e detected through 1 cm interspace between lights and dete ctor, which is the same distance as the thickness of cuvette ho lder. For in -situ NMR measurements, the li ght intensit ies were detected directly from the fiber. R elevant parameters are presented in Ta ble 7.1. 7.2 UV/Vis Ab s orption S pectrosco py 152 Besides, two hol es of the cuvette holder made it possi ble to use two LED li ghts one b y one without delay (Figure 7.3). A grey filter ( NDUV510B - OD 1.0) was applied between li ght sour ce and fiber, for reducing the high power of th e li ght source of the d etector, which can induce the switching of naphthop y ra ns. The gre y filter is made of fused sil ica substrate and can absorb aroun d 90 % of the incoming light. Its transmission-spectrum is demonstrated in Figure 7.4. Table 7.1 The sp ecifica tions of LED lights applied in this wo r k. The samples were prepared with solvents of spectroscopy grade in a 25 m L volumetric flask. The concentration is 1.5×10 -5 M. All the prepared s amples were de gassed with argon balloon under ultrasound for 15 min before mea surements. All the absorption spe ctra were a nal y s ed with the software Avasoft 8.5. Th e applied para meter for recording absorption spectra in thi s work is as follows: averag e over 200 spectra, 10 ms integration time , but the shortest ti me to record a spectrum is less than 1 second (average ov er 100 spe ctra, 1 ms integra tion time). LED λ m a x (nm) Bandwidth (nm) Power a (mW/cm 2 ) Power b (mW/cm 2 ) M340L4 345 11 12 - M365LP1 367 9 110 3.86 M420L3 420 15 73 8.10 M455L3 452 18 - 4.30 M505L3 512 30 70 2.37 M565L3 550 104 84 3.20 [a] Detected in r oom temperature U V -Vis spectro scopy . [b] Detected in low tempera ture in - situ N MR measurem ents. 7 Experim en tal Sect ion 153 Figure 7.3 The set- up of two LE D lights: 1 ) cuvette wi th stirring bar; 2) 1 st LED li ght; 3) 2 nd LED light; 4) cuvette ho lder; 5) opt ical fib er in composite p ipe; 6) m agnetic stirrer; 7) air s tream cooli ng (pictu r e from the PhD t hesis of Mar i na Vlac jić ). Figure 7.4 Transmission- spectrum of grey filter (provided by Thorlabs). 7.2 UV/Vis Ab s orption S pectrosco py 154 7.2.2 Time-Resolved Experiments and Expon ential F itting The TC and TT forms of one naphthop y r an we re regarded to have the same λ max , although a deviation of λ max, TC fr om λ max, T T was observ ed duri ng the therm al back re action of N1 , N2 and N3 in TCE because of the slow k TT→TC, thermal (see Chapter 8.3, Figures 8.3, 8.4 and 8.5). The time resolved absorbance were monitored at λ max o f th e open fo rms. W hen the s ystem arrived at P SS under UV irradiation, there were thre e isomers in the equilibrium: CF, TC and TT. Once UV light was switched off, there ex ist ed two processes: TC→CF and TT→TC + TC →CF with k TT→TC, thermal < k TC→CF, thermal . The decrease of abso rbance was moni tored for N1 , N2 , N3 and N4 , and are exhibited in Fig ures 7.6 and 7.7. The thermal relaxation kinetics were calculated from time- resolved absorbance at λ max , b y fitting the ex perimental data to the biex ponential decay. Relevant parameters and the coefficients of deter mination (R 2 ) are shown in Tables 7.2 and 7.3. Figure 7.5 The structures o f naphthopyran s N1 , N2 , N3 and N4 . 7 Experim en tal Sect ion 155 Figure 7.6 The tim e-resolved absorbance at λ m a x during thermal relaxation started fr om PSS (UV) (black dots) and biexponent i al decay fitting (red l ine) at 293 K: (a) N1 i n MeCN (data fr om Chapter 4, Figure 4.5- a), (b) N2 i n MeCN (data from Chapter 4, Figure 4.6- a), (c) N3 i n Me CN (data from Chapter 4, Figure 4.5- b) and (d) N4 in MeCN ( data from Chapte r 4, Figure 4 .6-b). Table 7.2 The pa r am eters of biexpon ential fit ting durin g therm al relaxation o f N1 , N2 , N3 and N4 . a -20 0 20 40 60 80 100 120 140 160 180 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 Thermal relaxation o f N1 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0.011 58 ± 2. 59719 E-4 A1 0.117 63 ± 0. 04367 t1 10.99 457 ± 1 .5617 6 A2 0.255 96 ± 0. 04388 t2 21.21 247 ± 1 .1765 1 Reduced Chi-Sqr 1.5596E-6 R-Square (COD) 0.999 76 Ad j. R-Square 0.999 75 a) -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 0.00 0.05 0.10 0.15 0.20 0.25 Thermal relaxation o f N2 in MeCN Biexponential decay fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0.002 27 ± 7. 79076 E-5 A1 0.209 5 ± 2.1 3617E-4 t1 174.9 2971 ± 0.347 39 A2 0.032 46 ± 8. 46028 E-5 t2 2853. 19525 ± 25.1 2531 Reduced Chi-Sqr 5.050 75E-7 R-Square (COD) 0.999 18 Ad j. R-Square 0.999 18 b) 200 400 600 800 1000 1200 1400 0.0 0.1 0.2 0.3 0.4 0.5 Thermal relaxation of N3 in M eCN Biexpotential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0.011 55 ± 1. 21577 E-4 A1 0.524 76 ± 41 206.3 0606 t1 131.2 2516 ± 23474 .4349 6 A2 1.329 25 ± 41 206.3 0585 t2 131.2 2055 ± 9269. 84244 Reduced Chi-Sqr 3.386 96E-6 R-Square (COD) 0.999 58 Ad j. R-Square 0.999 58 c) 0 1000 2000 3000 4000 5000 6000 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Thermal back of N4 in M eCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0.041 24 ± 2. 32547 E-5 A1 0.013 98 ± 2. 77538 E-4 t1 101.1 5206 ± 3.947 47 A2 0.453 32 ± 2. 40169 E-4 t2 752.7 6344 ± 0.414 56 Reduced Chi-Sqr 5.810 88E-7 R-Square (COD) 0.999 94 Ad j. R-Square 0.999 94 d) k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th R 2 N1 90.9 47.1 0.118 0.256 0.012 0.99 N2 5.72 0.35 0.210 0.032 0.002 0.99 N3 7.62 (7.62076) 7.62 (7.62049) 1.329 0.525 0.012 0.99 N4 9.89 1.33 0.014 0.453 0.041 0.99 [a] 1.5×10 -5 M in acetonitrile, 293 K. 7.2 UV/Vis Ab s orption S pectrosco py 156 Figure 7.7 The tim e-resolved absorbance at λ m a x during thermal relaxation started f rom PSS (UV) (black dots) and biexpone ntial decay fitting (red l ine) at 293 K : ( a) N1 in TCE (data from Chapter 4, Figure 4.9- a), (b) N2 in T CE (data from Chapter 4, Fig ure 4.9-b), (c ) N3 in T CE ( data from Chapter 4, Figure 4.9-c) and (d) N3 in DCM (data fr om Chapter 4, Figure 4.9- d) . Table 7.3 The pa r am eters of biexpon ential fit ting durin g therm al relaxation o f N1 , N2 and N3 . a 0 1000 2000 3000 4000 0.0 0.1 0.2 0.3 0.4 Time/s Absorbance Thermal back reaction o f N1 in TCE Biexponential decay fitting Model Ex pDec2 Equation y = A1*ex p(-x/t1) + A 2*ex p(-x/t2) + y0 Plot B y0 0.00525 ± 5.48316E-5 A1 0.0118 ± 0.00954 t1 266.87087 ± 83.44315 A2 0.38058 ± 0.00963 t2 511.10608 ± 4.10415 Reduced Chi-Sqr 2.27529E-6 R-Square(COD) 0.99969 A dj. R-Square 0.99969 a) 0 200 400 600 800 1000 0.00 0.05 0.10 0.15 0.20 0.25 Thermal back reaction o f N2 in TCE Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0.018 99 ± 7. 81241 E-5 A1 0.018 51 ± 7. 62096 E-4 t1 23.44 787 ± 1 .8263 3 A2 0.205 29 ± 6. 98338 E-4 t2 162.3 7873 ± 0.592 01 Reduced Chi-Sqr 1.314 15E-6 R-Square (COD) 0.999 48 Ad j. R-Square 0.999 47 b) 0 500 1000 1500 2000 2500 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 Thermal relaxation o f N3 in TCE Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 -0.002 72 ± 3. 88648 A1 0.176 57 ± 0. 34123 t1 1868. 55589 ± 1314 .4088 A2 0.042 62 ± 3. 54559 t2 15603 .0096 8 ± 196 4829. 59112 Reduced Chi-Sqr 5.197 48E-7 R-Square (COD) 0 .9996 Ad j. R-Square 0.99 96 c) -200 0 200 400 600 800 1000 1200 1400 1600 0.0 0.1 0.2 0.3 0.4 0.5 Time/s Absorbance at 573 nm Thermal back reaction o f N3 in DCM Biexponential decay fitting Mod el Ex pDec2 Eq uation y = A1*ex p(-x/t 1) + A2* exp ( -x/t 2) + y0 Pl ot B y0 0.03266 ± 3.61845E - 5 A1 0.01719 ± 4.88855E - 4 t1 10.09994 ± 0.54294 A2 0.42184 ± 1.99888E - 4 t2 192.83295 ± 0.13144 Redu c ed C h i- 4. 0291E-7 R-Squ are( CO 0.99996 Ad j. R -Sq uare 0. 99996 d) k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th R 2 N1 3.75 1.96 0.012 0.381 0.005 0.99 N2 42.7 6.16 0.019 0.205 0.019 0.99 N3 0.535 0.064 0.177 0.043 - 0.002 0.99 N3 b 99 5.19 0.017 0.422 0.033 0.99 [a] 1.5×10 -5 M in TCE, 293 K. [b ] 1.5×10 - 5 M in DCM . 7 Experim en tal Sect ion 157 When the s y st em of N4 arrived at PSS under UV irradiation, C F, TC and TT isomers existed in the equilibrium. Upon UV light was switched off, 565 nm light was switch ed on. T wo processes were observed in the system : TC→CF and TT→TC + TC →CF . The visible light bleaching kinetics were calcula ted from time-resolved absorbance a t λ max , by fitti ng the e xperimental data to the biex ponential deca y ( Fig ure 7.8). Relevant parameters and coefficients of determination (R 2 ) are a lso depicted in Table 7.4. Figure 7.8 The tim e -resolved absorbance at λ m a x during visible lig ht irradiat ion started from PSS (UV) (black dots ) and biexpone ntial decay f itting (red line) of N4 in ace tonitrile at 29 3 K (data f rom Chapter 4, Figure 4. 7) . Table 7.4 The pa r am eters of biexpon ential fit ting of N4 during irradiation w ith visib le light. a When the system of N5 , N6 and N7 arrived at PSS under UV irradiation, CF, TC and TT isomers existed in the equilibrium. Upon UV light was s witched off, t wo processes were observed in the system : TC→CF and TT→TC + TC →CF . But the speed of process TT→TC was far slower than the speed of process T C→CF ( k TT → TC, thermal << k TC→CF, thermal ). The T T form was almost not reduce d during the short thermal relaxation time window. Thus, the thermal relaxation kinetics were calculated from time-resolved absorbance measurements at λ max , b y fitting the experimental -20 0 20 40 60 80 100 120 140 160 180 0.0 0.1 0.2 0.3 0.4 0.5 0.6 565 nm VIS of N4 in MeCN Biexponential fitting M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 -3.172 66E-4 ± 0. 00367 A1 0.266 29 ± 2 15276 .65709 t1 28.62 301 ± 17593 9.7127 3 A2 0.282 35 ± 2 15276 .65711 t2 28.62 275 ± 16593 1.8017 6 Reduced Chi-Sqr 1.30131E-4 R-Square (COD) 0.99331 Ad j. R-Square 0.992 97 Absorbance Time/s k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th R 2 N4 34.9 (34.9372) 34.9 (34.9369) 0.266 0.282 - 0.0003 0.99 [a] 1.5×10 -5 M in MeCN, 293 K. Visible l ight: 565 nm , 84 mW/ cm 2 . 7.2 UV/Vis Ab s orption S pectrosco py 158 data to a monoex ponential decay (Figure 7. 10 ). Relevant parameters and coefficients of determination (R 2 ) are pr esented in Table 7.5. Figure 7.9 The structures o f naphthopyran s N5 , N6 and N7 . Figure 7.10 The time-resolv ed absor bance at λ max during thermal relaxa tion started from PSS (UV) (black dots) and m onoexponential decay fit ting (red li ne) at 293 K: (a) N5 i n MeCN (data f rom C hapter 4, F igure 4.13- a), (b) N6 i n Me CN (data from Chapter 4, Figur e 4.13-b) and (c ) N7 i n MeCN ( data from Chapter 4, Figure 4.18). 0 10 20 30 40 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 N5 in acetonitrile Monoexponential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.03844 ± 1 .46974E-4 A1 0.11106 ± 4 .54547E-4 t1 1.57826 ± 0 .02848 Reduced Chi-Sqr 1.85424E-7 R-Square (C OD) 0.99987 Adj . R-Square 0.99983 a) -10 0 10 20 30 40 50 60 70 80 0.00 0.05 0.10 0.15 0.20 0.25 N6 in MeCN Monoexponential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot Q2 in M eC N y0 0.04076 ± 1 .84299E-4 A1 0.18863 ± 7 .38928E-4 t1 7.11212 ± 0 .05118 Reduced Chi-Sqr 7 .8374E-7 R-Square (C OD) 0.99959 Adj . R-Square 0.99957 b) 0 5 10 15 20 25 30 0.00 0.05 0.10 0.15 0.20 0.25 N7 in MeCN Monoexponential fitting M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.02985 ± 4 .56387E-4 A1 0.20547 ± 0 .00195 t1 2.49546 ± 0 .04204 Reduced Chi-Sqr 6 .8696E-6 R-Square (C OD) 0.9967 Adj . R-Square 0.99657 Absorbance Time/s c) 7 Experim en tal Sect ion 159 Table 7.5 The pa r am eters of m onoexpone nti al fitting of N5 , N6 and N7 dur ing therm al r elaxa tion. a After therm al relaxation in the UV/Vis measurements , there were onl y two isom ers, TT and CF, in the s y stem o f N5 , N6 and N7 . Upon visible light (420 nm for N5 and N6 ; 505 nm for N7 ) w as switched on, the process , TT→TC→CF ex isted in the s ystem. Wherein the process TT→TC was the rate determining step because of the faster sp eed of TC→C F . Accordingl y , the time -resolved absorbance at λ max w as studied b y usin g a mon oexponential deca y model during visible li ght irradiation (Figure 7.11). Relevant parameters and c oefficients of determination (R 2 ) are presented in Table 7.6. Table 7.6 The pa r am eters of m onoexpone nti al fitting of N5 , N6 and N7 during irradiati on with v isible light. a k TC→CF, ther mal (s -1 ) A th R 2 N5 0.634 0.038 0.99 N6 0.141 0.041 0.99 N7 0.401 0.030 0.99 [a] 1.5×10 -5 M in acetonitri le, 293 K. k TT→TC, Vis (s -1 ) A th R 2 N5 b 0.150 0.023 0.97 N6 b 0.106 0.022 0.98 N7 c 0.149 0.008 0.94 [a] 1.5×10 -5 M in acetonitri le, 293 K.[b ] Visib le light: 420 nm , 73 mW/ cm 2 . [c ] Visible lig ht : 505 nm , 70 mW/ cm 2 . 7.2 UV/Vis Ab s orption S pectrosco py 160 Figure 7. 11 T he t ime- resol ved absorbance at λ m a x during visibl e li ght irradiation (bla ck dot s) and m onoexponential decay fitting (red li ne) at 293 K: ( a) N5 in MeCN (data f rom Chapter 4, Figur e 4. 13 - a) , (b) N6 in MeCN ( data from Chapter 4, Figure 4.13-b) and (c ) N7 i n Me CN (data from Chapter 4, Fig ure 4.18). 0 10 20 30 40 50 60 70 0.022 0.024 0.026 0.028 0.030 0.032 0.034 0.036 0.038 420 nm for N5 in aceto nitrile Monoexpotential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.02307 ± 3 .90944E-4 A1 0.01494 ± 9 .58418E-4 t1 6.67353 ± 0 .90768 Reduced Chi-Sqr 9.17177E-7 R-Square (C OD) 0. 966 Adj . R-Square 0.95845 a) 0 10 20 30 40 50 60 0.020 0.025 0.030 0.035 0.040 0.045 420 nm for N6 in MeCN Monoexponential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.02153 ± 2 .2124E-4 A1 0.02066 ± 5 .85542E-4 t1 9.47662 ± 0 .55141 Reduced Chi-Sqr 5.78 961E-7 R-Square (C OD) 0.9 8171 Adj . R-Square 0 .98035 b) 0 5 10 15 20 25 0.005 0.010 0.015 0.020 0.025 0.030 505 nm for N7 in MeCN Monoexpotential fitting Absorbance Time/s M odel ExpDec1 Equation y = A 1* exp(-x/t1) + y0 Plot B y0 0.00792 ± 6 .71593E-4 A1 0.01969 ± 7 .69623E-4 t1 6.71267 ± 0 .76976 Reduced Chi-Sqr 1.83 854E-6 R-Square (C OD) 0.9 4149 Adj . R-Square 0 .93864 c) 7 Experim en tal Sect ion 161 7. 3 In -situ N MR M easurem ent The set-up of in -situ NMR measure ments is depicted in Fig ure 7.12. A 6 m optica l fibre was used for transmitting light. The light source were LED li ghts, which were connected with an attachment to the fiber (Figure 7.12 rig ht). Th e other tip of the fiber was prepared based on the li terature [1 39] and inserted into the NMR tube with the samples (F igure 7.12 left). Figure 7.12 The device of in -situ NMR m easur ements. As demonstrated in Figure 7.13, the cladding of 5 cm of the fiber was removed from one end of the fiber, which will be inserted int o the NMR tube. Then the top 3 cm fiber was sand blasted to make sure the li ght is distributed over th e whole di stance of the NMR sample (Figure 7.11 middl e). At last, the prepared end of the fiber was put into a NMR-tube insertion m ade f rom quartz glass with an absorption <300 nm. Now the other tip of fiber, which will be inser ted into the NMR tube, was prepare d well. The NMR samples were prepared with acetonit rile- d 3 in a concentration of 1×10 -2 M. At first, 0.4 mL pr epared sampl e were tr ansferred into an amber NMR tube (absorption spectrum demonstrated in Fi gure 7. 14). At second, th e prepa red NMR -tube inse rtion with a cap was put int o the NMR tube. At last, the NMR tube was carefully ins erted into the Bruker Avance III 500 MHz NMR spectrometer, which was alread y cooled down to 238 K. After one spectrum of the closed form was measured, UV light was switched on and the NMR spectra were measured one b y one with the same delay time, and all the spec tra were anal y s ed b y Topspi n 3.5pl7 software. 7.3 In -situ NMR m easurem ent 162 For 1 H NMR measure me nts, 8 sc ans we re detected per spectrum. Every sp ectrum wa s obtained in 46 s and there was 1 s delay time between two spectra. For 19 F NMR measurements, 32 scans were detected p er spectrum. Ever y spectrum was obtain ed in 66 s and there w as 1 s dela y ti me between two spectra. Figure 7.13 The prepa red NMR- tube i nsertion wi th roug hened fiber inside (le ft); the NMR- tube insertion when UV lig ht was swi tched on (m iddle); the brown N MR tube wi th prepared insertion i nside (right). Figure 7.14 The absorp tion spec t rum of am beri zed Py rex NMR tu be (provided by D eutero). 8 Appendix 163 8 . Appendix 8.1 1 H and 13 C NMR Spectra 10 9 8 7 6 5 4 3 2 1 0 ppm 3.879 7.159 7.164 7.177 7.181 7.189 7.759 7.776 7.851 7.854 7.868 7.871 7.964 7.981 8.491 10.181 3.043 2.038 1.025 1.005 1.035 1.000 0.972 7.15 7.20 ppm 8.1 1 H an d 13 C N MR Spectra 164 9 8 7 6 5 4 3 2 1 0 ppm 3.529 3.966 5.319 7.256 7.260 7.274 7.279 7.414 7.419 7.755 7.772 7.860 7.878 8.012 8.015 8.029 8.033 8.537 2.930 2.954 2.009 1.342 0.990 1.005 1.022 0.983 0.969 7.30 7.35 7.40 ppm 8 Appendix 165 9 8 7 6 5 4 3 2 1 0 ppm 3.530 4.817 5.296 7.215 7.219 7.232 7.237 7.391 7.396 7.435 7.437 7.452 7.455 7.731 7.739 7.747 7.758 3.010 2.088 2.060 0.990 1.000 1.085 3.176 7.75 ppm 7.3 7.4 ppm 8.1 1 H an d 13 C N MR Spectra 166 9 8 7 6 5 4 3 2 1 0 ppm 3.525 4.658 5.298 7.223 7.228 7.241 7.246 7.385 7.389 7.458 7.461 7.475 7.478 7.723 7.728 7.740 7.746 7.768 3.003 1.943 2.108 0.985 1.011 1.006 2.011 1.100 7.4 7.6 ppm 8 Appendix 1 67 8.1 1 H an d 13 C N MR Spectra 168 8 Appendix 169 8.1 1 H an d 13 C N MR Spectra 170 8 Appendix 171 9 8 7 6 5 4 3 2 1 0 ppm 1.347 1.459 3.545 3.771 5.023 5.322 7.258 7.260 7.263 7.276 7.280 7.344 7.348 7.401 7.406 7.437 7.442 7.523 7.527 7.540 7.543 7.798 7.810 7.814 7.827 7.902 9.110 9.041 2.937 2.028 1.991 1.967 1.441 0.995 0.997 1.010 1.009 2.028 1.000 7.3 7.4 7.5 7.6 7.7 7.8 ppm 8.1 1 H an d 13 C N MR Spectra 172 9 8 7 6 5 4 3 2 1 ppm 0.758 1.010 1.023 1.346 1.432 1.686 1.699 1.712 1.725 1.737 1.750 1.763 1.810 1.825 1.838 1.853 2.192 2.214 3.537 5.051 5.312 7.237 7.242 7.255 7.260 7.403 7.408 7.422 7.427 7.451 7.455 7.487 7.490 7.504 7.507 7.765 7.783 7.787 7.805 7.884 6.064 6.111 9.236 9.277 2.066 2.081 1.911 3.019 1.926 2.032 1.375 1.047 1.022 0.992 1.030 2.059 1.000 7.3 7.4 7.5 7.6 7.7 7.8 ppm 8 Appendix 173 9 8 7 6 5 4 3 2 1 0 ppm 0.746 0.759 1.025 1.038 1.346 1.361 1.375 1.389 1.427 1.717 1.729 1.742 1.754 1.767 1.846 1.860 1.874 1.889 2.147 2.169 3.540 4.298 4.313 4.327 4.341 5.073 5.338 6.503 6.534 7.315 7.320 7.333 7.338 7.395 7.400 7.405 7.410 7.695 7.700 7.802 7.837 7.855 7.965 8.435 8.466 6.303 6.403 9.673 3.318 9.462 2.119 2.144 2.040 3.115 2.107 2.011 1.989 0.987 0.992 2.147 0.996 0.983 1.065 0.999 1.000 7.4 7.6 7.8 8.0 8.2 8.4 ppm 2.0 ppm 1.4 ppm 8.1 1 H an d 13 C N MR Spectra 174 9 8 7 6 5 4 3 2 1 0 ppm 0.751 1.005 1.018 1.332 1.340 1.346 1.360 1.437 1.671 1.684 1.697 1.709 1.722 1.734 1.748 1.801 1.815 1.829 1.843 2.157 2.170 2.177 3.535 4.267 4.281 4.295 4.309 5.088 5.314 6.506 6.538 7.395 7.400 7.414 7.418 7.480 7.485 7.497 7.502 7.582 7.585 7.599 7.602 7.800 7.817 8.191 8.418 8.449 6.146 6.267 13.516 8.974 2.119 2.146 2.029 3.093 2.073 1.959 2.089 0.987 2.177 2.001 0.981 1.010 0.973 1.000 7.6 7.8 8.0 8.2 8.4 ppm 4.30 ppm 1.35 ppm 8 Appendix 175 9 8 7 6 5 4 3 2 1 0 ppm 0.753 0.766 1.043 1.056 1.343 1.354 1.369 1.383 1.424 1.743 1.755 1.766 1.882 1.896 1.910 1.924 2.131 2.145 2.152 4.293 4.308 4.322 4.336 5.085 6.465 6.496 7.041 7.046 7.059 7.064 7.326 7.331 7.353 7.357 7.395 7.400 7.682 7.700 7.744 7.927 8.342 8.373 6.151 6.067 13.627 9.839 2.153 2.231 2.006 2.018 1.950 0.988 1.023 0.921 1.067 1.272 0.976 1.025 1.031 1.000 7.2 7.4 7.6 7.8 8.0 8.2 8.4 ppm 4.30 4.35 ppm 1.35 ppm 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 14.487 23.726 24.052 26.121 31.531 32.062 34.762 36.267 44.869 51.022 60.816 76.765 105.665 118.586 119.990 123.596 124.340 125.253 125.401 127.463 128.993 130.263 130.568 130.930 131.728 132.471 142.288 143.399 146.280 153.779 155.112 167.595 8.1 1 H an d 13 C N MR Spectra 176 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm 7.1543 7.1729 7.1890 7.1914 7.3433 7.3474 7.3583 7.3609 7.3652 7.3790 7.3840 7.3905 7.3979 7.4047 7.4094 7.4226 7.4274 7.4354 7.4391 7.4549 7.4589 7.6319 7.6336 7.6526 7.7283 7.7332 7.7464 7.7514 7.9320 1.00 5.00 2.01 1.00 0.87 7.9 8.0 ppm 7.74 7.76 ppm 7.64 7.66 ppm 7.40 7.45 ppm 7.20 ppm 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 120.25 124.99 127.43 129.26 130.47 130.51 130.73 131.83 135.32 137.67 164.60 8 Appendix 177 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm 2.0181 2.0268 2.0348 2.0428 2.0515 3.3593 3.3700 3.3758 3.3819 3.3925 6.5057 6.5281 7.3022 7.3042 7.3208 7.3232 7.3288 7.3372 7.3475 7.3562 7.3626 7.3671 7.3759 7.3808 7.3896 7.4198 7.4386 7.6822 7.6888 7.7108 7.7172 3.83 3.96 2.00 2.93 0.95 1.91 7.70 ppm 7.44 ppm 7.35 ppm 6.55 ppm 3.40 ppm 2.05 ppm 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 25.55 47.80 111.05 123.95 126.62 128.90 129.88 130.25 131.15 132.85 140.11 151.57 193.20 8.1 1 H an d 13 C N MR Spectra 178 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm 2.0076 2.0161 2.0241 2.0318 2.0406 2.8686 3.0626 3.3006 3.3168 3.3332 6.5292 6.5505 7.2773 7.2816 7.2918 7.2961 7.3027 7.3148 7.3192 7.3469 7.3509 7.3598 7.3660 7.3769 7.3820 8.0136 8.0187 8.0294 8.0348 8.0381 4.03 0.91 0.89 4.07 2.00 1.28 4.04 0.99 8.04 ppm 7.38 ppm 7.30 7.32 ppm 6.55 ppm 3.35 ppm 3.0 ppm 2.05 ppm 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 25.60 47.65 73.61 75.04 84.99 111.19 126.63 127.67 128.11 129.20 129.57 131.29 132.63 140.98 147.73 8 Appendix 179 9 8 7 6 5 4 3 2 1 0 ppm 0.746 0.759 0.873 0.888 0.902 1.019 1.032 1.340 1.430 1.693 1.706 1.719 1.731 1.744 1.757 1.770 1.835 1.849 1.863 1.877 2.171 2.184 2.193 5.053 5.319 7.034 7.039 7.041 7.058 7.062 7.398 7.458 7.460 7.475 7.478 7.638 7.655 7.706 7.723 7.862 6.037 6.112 9.193 9.026 2.002 2.066 1.869 1.994 1.028 2.010 2.004 1.014 1.016 1.011 1.000 7.5 7.6 7.7 ppm 7.05 ppm 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 ppm 23.657 24.040 26.145 31.538 32.126 34.742 36.283 45.297 50.664 76.842 77.157 77.477 109.471 118.234 124.494 124.666 125.314 125.479 126.707 128.691 129.678 130.722 132.247 134.083 143.419 146.154 153.897 153.934 8.1 1 H an d 13 C N MR Spectra 180 8 Appendix 181 10 9 8 7 6 5 4 3 2 1 0 ppm 0.714 0.725 0.727 0.977 0.991 1.318 1.391 1.824 1.838 1.852 1.866 1.916 1.923 1.930 1.935 1.940 1.945 1.950 3.176 3.189 3.203 5.048 6.451 6.468 6.594 6.614 7.157 7.161 7.165 7.174 7.178 7.269 7.272 7.284 7.287 7.304 7.316 7.319 7.357 7.360 7.364 7.370 7.375 7.390 7.451 7.456 7.599 7.602 7.616 7.619 7.698 7.716 7.875 7.879 7.891 7.894 8.025 8.043 5.961 5.968 9.498 8.886 2.054 2.024 2.031 4.025 1.946 1.997 1.006 2.953 2.120 2.976 1.005 1.026 1.021 1.989 1.000 7.90 ppm 7.30 7.35 7.40 ppm 2.0 2.1 ppm 1.8 ppm 8.1 1 H an d 13 C N MR Spectra 182 10 9 8 7 6 5 4 3 2 1 0 ppm 0.723 0.736 1.001 1.014 1.331 1.406 1.681 1.693 1.706 1.718 1.731 1.807 1.821 1.835 1.849 2.149 2.150 2.166 2.180 5.025 6.172 6.192 6.987 7.004 7.022 7.166 7.184 7.321 7.340 7.381 7.386 7.397 7.424 7.428 7.435 7.442 7.452 7.551 7.569 7.678 7.696 7.812 7.976 7.993 6.091 6.087 9.247 9.074 2.044 2.038 1.768 1.960 0.988 4.265 1.069 1.032 2.086 4.031 0.985 1.012 1.007 1.000 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 ppm 1.8 2.0 2.2 ppm 8 Appendix 183 9 8 7 6 5 4 3 2 1 0 ppm 0.726 0.740 1.009 1.022 1.318 1.331 1.335 1.347 1.422 1.703 1.715 1.814 1.828 1.842 1.856 4.253 4.267 4.282 4.296 5.079 6.238 6.258 6.487 6.519 6.993 7.000 7.004 7.010 7.013 7.017 7.021 7.023 7.027 7.030 7.034 7.341 7.362 7.367 7.384 7.389 7.414 7.419 7.425 7.429 7.432 7.436 7.438 7.443 7.446 7.455 7.667 7.670 7.685 7.688 8.039 8.056 8.162 8.371 7.057 7.340 12.862 8.847 2.498 2.369 0.951 2.117 0.656 2.287 1.931 0.967 0.968 4.992 2.246 1.226 4.396 0.968 1.010 1.005 1.033 1.000 8.2 8.4 ppm 1.8 2.0 2.2 ppm 7.1 7.2 7.3 7.4 ppm 8.1 1 H an d 13 C N MR Spectra 184 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm 1.8559 1.8652 1.8722 1.8789 1.8882 3.1191 3.1353 3.1514 3.8851 6.4186 6.4407 6.5752 6.6005 7.0929 7.1148 7.2923 7.3009 7.3144 7.3193 7.3312 7.3364 7.3490 7.3536 7.3675 7.3719 7.4059 7.4108 7.4244 7.4289 7.4699 7.4954 7.7047 7.7095 7.7231 7.7286 7.9384 7.9429 7.9606 7.9650 7.9837 8.0060 8.1636 8.1861 8.5218 8.5260 4.01 4.01 2.97 2.04 1.02 2.04 3.13 1.00 1.01 0.99 1.03 0.98 1.00 1.00 8.55 ppm 8.20 ppm 8.00 ppm 7.72 ppm 7.50 ppm 7.42 ppm 7.35 ppm 7.10 ppm 6.60 ppm 6.45 ppm 3.90 ppm 3.15 ppm 1.90 ppm 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 24.91 47.12 52.09 82.64 110.97 113.69 119.02 119.46 122.19 124.72 125.74 126.10 126.77 127.94 128.00 128.18 128.57 129.45 130.95 131.16 131.48 131.53 131.58 140.92 147.08 151.93 166.25 120 122 124 126 128 130 132 ppm 119.02 119.46 122.19 124.72 125.74 126.10 126.77 127.94 128.00 128.18 128.57 129.45 130.95 131.16 131.48 131.53 131.58 8 Appendix 185 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm 1.8753 1.8844 1.8917 1.8986 1.9077 3.1408 3.1569 3.1731 4.6068 4.6207 5.2529 5.2670 5.2813 6.4334 6.4555 6.5444 6.5696 7.0927 7.0994 7.1214 7.1721 7.1942 7.2865 7.2913 7.3048 7.3098 7.3231 7.3290 7.3433 7.3479 7.3620 7.3663 7.3945 7.3992 7.4124 7.4135 7.4175 7.4485 7.4538 7.4702 7.4743 7.4801 7.7172 7.7303 7.7477 7.7523 7.7663 7.7714 8.0342 8.0562 3.90 3.91 1.96 0.97 1.96 1.00 1.97 1.05 2.09 1.00 1.96 2.95 0.94 8.05 ppm 7.75 ppm 7.45 ppm 7.35 ppm 7.2 ppm 6.5 ppm 5.30 ppm 4.65 ppm 3.15 3.20 ppm 1.90 ppm 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 ppm 24.92 47.14 62.78 82.09 110.94 113.64 117.89 119.93 121.44 125.10 125.66 126.24 126.67 128.02 128.34 128.47 128.59 128.78 129.30 129.66 130.92 131.42 137.97 141.19 147.02 149.51 122 124 126 128 130 132 ppm 119.93 121.44 125.10 125.66 126.24 126.67 128.02 128.34 128.47 128.59 128.78 129.30 129.66 130.92 131.42 8.1 1 H an d 13 C N MR Spectra 186 8 Appendix 187 Figure 8.1 The 1 H NMR sp ectrum of nondirecte d C-H functionalization p r oducts and their ratios (Chapter 3, T able 3.2- entry 1). 9 8 7 6 5 4 3 2 1 0 ppm 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 ppm 6.025 6.065 6.102 6.133 6.522 6.561 6.588 6.627 6.666 6.706 0.054 0.084 0.326 0.302 0.250 8.1 1 H an d 13 C N MR Spectra 188 Figure 8.2 The 1 H NMR sp ectrum of naphthopyran 2 8 (up) and the crud e 1 H NMR spec t rum of reac tion (0.17 mm ol scal e) in F igure 3.25 (Chapt er 3) using CH 2 Br 2 (0.13 mm ol) as the in ternal stan ard (down). 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 ppm 6.987 6.991 7.000 7.004 7.008 7.011 7.017 7.022 7.158 7.175 7.322 7.324 7.335 7.338 7.340 7.344 7.351 7.354 7.426 7.431 7.437 7.440 7.441 7.444 7.451 7.455 7.467 7.470 7.481 7.484 7.487 7.498 7.500 7.664 7.682 7.720 7.721 7.736 7.737 7.953 4.236 1.003 1.996 5.227 0.986 0.986 1.000 5.0 5.5 6.0 ppm 5.298 6.167 6.187 0.991 H2-28 7.0 7.1 7.2 7 .3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 ppm 5.0 5.5 6.0 ppm 1.500 0.981 CH2Br2 H2-28 8 Appendix 189 8.2 2D NMR Spectra Compound 14 - 13 C-DEPT Compound 14 - HH -COSY 180 160 140 120 100 80 60 40 20 0 ppm 14.499 23.659 24.042 26.170 27.167 31.538 32.187 50.547 56.343 60.713 76.510 94.795 106.900 119.212 120.991 123.957 124.803 125.584 127.305 130.583 141.790 8.2 2D NMR Spec tra 190 Compound 14 - HC -HMQC Compound 14 - HC -HMBC 8 Appendix 191 Compound 15 - 13 C-DEPT Compound 15 - HH -COSY 180 160 140 120 100 80 60 40 20 ppm 14.525 23.624 24.085 26.234 31.598 32.250 50.380 56.332 60.767 76.966 94.797 112.830 118.198 120.421 121.978 125.054 125.260 125.640 128.324 141.141 8.2 2D NMR Spec tra 192 Compound 15 - HC -HMQC Compound 15 - HC -HMBC 8 Appendix 193 Compound N7 - 13 C-DEPT Compound N7 - HH -COSY 8.2 2D NMR Spec tra 194 Compound N7 - HC -HMQC Compound N7 - HC -HMBC 8 Appendix 195 8.3 UV Absorpti on Spectr a Figure 8. 3 Abso rbance changes of N1 during (a) UV irradiation (left) and (b) thermal relaxation i n t he darkness ( rig ht) in tetrachloroethy lene (c = 1.5×1 0 -5 M) at 293 K. (340 nm, 12 mW/cm 2 . The arrows are presented to guide the eye through the changes in t he absorba nce, PSS: reached after 160 s, a shift of λ m a x was observed du ring the th ermal back reaction ). 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 Absorbance Wavelength (nm) 0 s 2 s 7 s 17 s 30 s 50 s 80 s 160 s 526 nm 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 0,5 0,6 Absorbance Wavelength (nm) 0 s 100 s 200 s 400 s 700 s 1300 s 4100 s 526 nm 478 nm 8.3 UV Absor p tion S pectra 196 Figure 8. 4 Abso rbance changes of N2 during (a) UV irradiation (left) and (b) ther m al rel axation in th e darkness (right) in tetrach loroethy lene (c = 1.5×10 -5 M) at 293 K . (340 nm , 12 mW/cm 2 . The arrows are presented to guide the eye thr ough the changes in the absorbanc e, PSS: reached a fter 80 s , a shift of λ m ax was observed du ring the th ermal back reaction). 300 400 500 600 700 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 Absorbance Wavelength (nm) 0s 2s 6s 15s 30s 80s 553 nm 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 Absorbance Wavelength (nm) 0s 50s 140s 290s 700s 506 nm 553 nm 8 Appendix 197 Figure 8. 5 Abso rbance changes of N3 during (a) UV irradiation (left) and (b) ther m al rel axation in th e darkness (right) i n tetrachloroe thylene (c = 1.5×10 -5 M) at 293 K. (340 nm, 12 mW/cm 2 . The arrows are presented to guide the eye through the chang es in the absorbance, PSS: reached after 160 s , a shift of λ m a x was observed du ring the th ermal back reaction). 300 400 500 600 700 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 Absorbance Wavelength (nm) 0 s 20 s 60 s 120 s 180 s 360 s 1180 s 573 nm Figure 8 .6 Abso rbance chang es of N3 during (a) UV irradiat ion (left) and ( b) ther m al rel axation in th e darkness (right) in DCM (c = 1.5×10 -5 M) at 293 K. ( 340 nm, 12 mW/cm 2 . T he arrow s are presented t o guide the ey e t hroug h the chang es in the abso r bance, P SS: r each ed after 100 s.) 300 400 500 600 700 0,0 0,1 0,2 0,3 0,4 Wavelength (nm) Absorbance 0 s 3 s 10 s 30 s 80 s 160 s 498 nm 300 400 500 600 700 800 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 Absorbance Wavelength (nm) 0 s 1000 s 2000 s 4000 s 498 nm 479 nm 300 400 500 600 700 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 Absorbance Wavelength (nm) 0 s 2 s 4 s 8 s 16 s 30 s 100 s 573 nm 8.3 UV Absor p tion S pectra 198 Figure 8.7 Absorban ce chang es of N4 during visible lig ht bleaching (565 nm, 84 m W/cm 2 ) i n MeCN (c = 1.5×10 -5 M) at 293 K. (The arrows are present ed to gu i de t he eye throug h the cha nges in the absor bance, PSS: reached a ft er 24 s.) 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0 Absorbance Wavelength (nm) 0 s 6 s 12 s 18 s 28 s 38 s 126 s 8 Appendix 199 Figure 8.8 UV i rradiation /dark cycles f or N6 in M eCN (c = 1.5×10 - 5 M) at 293 K. The grey regions sig nal the period when the sam ple was irradiated with UV light (365 nm, 110 mW/cm 2 ); non-m arked regions present the peri ods when the sample was i n the dark in the sho rt time window and totally thermal back to the initia l state will be f ound if the sam ple is in the dark for long enough time (m oni toring wavele ngth is between 425 and 426 nm ). 0 200 400 600 800 1000 0.00 0.05 0.10 0.15 0.20 0.25 N6 in acetonitrile 425 and 426 nm Absorbance Time/s 8.3 UV Absor p tion S pectra 200 Figure 8.9 UV i rradiation /dark cycles f or N7 in M eCN (c = 1.5×10 - 5 M) at 293 K. The grey regions sig nal the period when the sam ple was irradiated with UV light (365 nm, 110 mW/cm 2 ); non-m arked regions present the peri ods when t he sample was in the dark in the short time window and totally thermal back to the initia l state will be f ound if the sam ple is in the dark for long enough time (m oni toring wavele ngth is between 445 and 446 nm ). Table 8.1 Som e physical propertie s of the so lvents use d in this thesis. 0 50 100 150 200 250 0.00 0.05 0.10 0.15 0.20 0.25 N7 in MeCN 445-446 nm Absorbance Time/s Solvent Permittiv ity ε (25℃) n V iscosity , η /mPa ∙ s (25℃) b.p./ ℃ TCE 2.5 1.49 0.829 121 DCM 8.93 1.42 0.41 39.7 MeCN 35.7 1.34 0.37 81.6 8 Appendix 201 200 400 600 800 1000 1200 1400 0.0 0.1 0.2 0.3 0.4 0.5 1st circle of N3 in MeCN Biexpotential fitting Absorbance Time/s M odel ExpDec2 Equatio n y = A 1*exp(-x /t1) + A 2*exp(-x /t 2) + y0 Plot B y0 0.011 55  ± 1.21577E-4 A1 0.524 76  ± 41206.306 06 t1 131.2 2516  ± 23474.4 3496 A2 1.329 25  ± 41206.305 85 t2 131.2 2055  ± 9269.84 244 Reduced Chi-Sqr 3.38696E-6 R-Square (COD) 0.99958 Ad j. R-Square 0.999 58 0 200 400 600 800 1000 1200 0,0 0,1 0,2 0,3 0,4 0,5 2nd circle of N3 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0,006 58  ± 0,01998 A1 0,445 7  ± 0,00 217 t1 123,8 8176  ± 0,6805 5 A2 0,006 35  ± 0,01772 t2 1833, 25963 ± 8778, 70027 Reduced Chi-Sqr 3,871 55E-6 R-Square (COD) 0,999 58 Ad j. R-Square 0,99958 0 200 400 600 800 1000 0,0 0,1 0,2 0,3 0,4 0,5 3rd circle of N3 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot 3 y0 0,009 07  ± 0,00392 A1 0,420 78  ± 0,00585 t1 138,1 8017  ± 1,3722 6 A2 0,010 06  ± 0,00249 t2 676,1 2375  ± 831,77 194 Reduced Chi-Sqr 3,343 07E-6 R-Square (COD) 0,999 65 Ad j. R-Square 0,999 65 Figure 8.10 The t ime- resol ved abs orban ce at λ m ax during thermal relaxat ion (b l ack dots) and bi exponentia l decay fitting (red line) in MeCN (1.5×10 -5 M) at 293 K: (a) N3 in the 1 st c ircle, (b) N3 in the 2 nd circle and (c ) N3 in t he 3 rd circle. (Da ta from Chapter 4, Fig ure 4.5- b) Table 8.2 The param et ers of biexponenti al fitting of N3 during therm al back reaction (Chapter 4, Figure 4.5- b). a k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th R 2 1 st circle 7.62 7.62 0.223 0.221 - 0.0003 0.99 2 nd circle 8.07 0.55 0.446 0.006 0.0066 0.99 3 rd circle 7.24 1.48 0.421 0.010 0.0090 0.99 [a] 1.5×10 -5 M in MeCN, 293 K. 8.3 UV Absor p tion S pectra 202 Figure 8.11 The t ime- resol ved abs orban ce at λ m ax during thermal relaxat ion (b l ack dots) and bi exponentia l decay fitting (red line) in MeCN (1.5×10 -5 M) at 293 K: (a) N1 in the 1 st c ircle, (b) N1 in the 2 nd circle and (c ) N1 in t he 3 rd circle. (Da ta from Chapter 4, Fig ure 4.5- a) Table 8.3 The param et ers of biexponenti al fitting of N1 during therm al back reaction (Chapter 4, Figure 4.5- a) . a -20 0 20 40 60 80 100 120 140 160 180 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 Thermal relaxation o f 1st circle of N1 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 0,011 58 ± 2 ,59719 E-4 A1 0,117 63 ± 0 ,04367 t1 10,99 457 ± 1,5617 6 A2 0,255 96 ± 0 ,04388 t2 21,21 247 ± 1,1765 1 Reduced Chi-Sqr 1,559 6E-6 R-Square (COD) 0,99976 Ad j. R-Square 0,999 75 0 50 100 150 200 250 300 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 2nd circle of N1 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot 2nd circle of N1 in M eCN y0 0,011 87 ± 7 ,27521 E-5 A1 0,046 59 ± 0 ,00274 t1 4,615 69 ± 0 ,30452 A2 0,301 71 ± 0 ,00279 t2 18,72 41 ± 0 ,11468 Reduced Chi-Sqr 4,62117E-7 R-Square (COD) 0,99987 Ad j. R-Square 0,999 87 0 50 100 150 200 250 300 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 3rd circle of N1 in MeCN Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot 3rd circle of N1 in M eCN y0 0,013 03 ± 2 ,69031 E-4 A1 0,321 93 ± 0 ,02348 t1 16,05 37 ± 0 ,58205 A2 0,028 05 ± 0 ,02372 t2 35,91 961 ± 12,244 38 Reduced Chi-Sqr 2,18199E-6 R-Square (COD) 0,99946 Ad j. R-Square 0,999 44 k 1 (10 -2 s -1 ) k 2 (10 -2 s -1 ) A 1 A 2 A th R 2 1 st circle 9.09 4.71 0.118 0.256 0.012 0.99 2 nd circle 21.6 5.34 0.047 0.302 0.013 0.99 3 rd circle 6.23 2.78 0.322 0.028 0.012 0.99 [a] 1.5×10 -5 M in MeCN, 293 K. 8 Appendix 203 Figure 8.12 The time- resolved abs orbanc e at λ m ax during irradiation with visible light (black dots) and biexponenti al decay fitting (r ed l ine) in MeCN (1.5×10 -5 M) at 293 K : (a) N 4 in the 1 st circle, (b) N 4 in the 2 nd ci rcle and (c ) N4 in the 3 rd circle. ( Visible light: 56 5 nm, 84 mW/cm 2 , data from Chapter 4, Figure 4. 7) Table 8.4 The param eters of biexponen t ial fitting of N4 during irradiation with visible light (Chap t er 4, Figure 4.7). a -20 0 20 40 60 80 100 120 140 160 180 0,0 0,1 0,2 0,3 0,4 0,5 0,6 565 nm VIS of N4 in MeCN (1st circ le) Biexponential fitting M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot B y0 -3,172 66E-4 ± 0, 00367 A1 0,266 29 ± 2 15276 ,65709 t1 28,62 301 ± 17593 9,7127 3 A2 0,282 35 ± 2 15276 ,65711 t2 28,62 275 ± 16593 1,8017 6 Reduced Chi-Sqr 1,30131E-4 R-Square (COD) 0,99331 Ad j. R-Square 0,992 97 Absorbance Time/s 0 50 100 150 200 0,0 0,1 0,2 0,3 0,4 0,5 0,6 565 nm VIS of N4 in MeCN (2nd circle) Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot 2nd circle of N4 in M eCN y0 0,002 78 ± 0 ,00255 A1 0,266 66 ± -- t1 26,82 564 ± 26850 39,441 15 A2 0,280 31 ± -- t2 26,82 565 ± 25542 55,165 58 Reduced Chi-Sqr 1,16248E-4 R-Square (COD) 0,99345 Ad j. R-Square 0,993 14 0 50 100 150 200 0,0 0,1 0,2 0,3 0,4 0,5 0,6 565 nm VIS of N4 in MeCN (3rd circle) Biexponential fitting Absorbance Time/s M odel ExpDec2 Equati on y = A 1*exp(-x/t1) + A 2*exp(-x/t 2) + y0 Plot 3rd circle of N4 in M eCN y0 0,004 ± 0,00 229 A1 0,274 26 ± 1 54307 ,5472 t1 26,21 041 ± 59343 90,158 48 A2 0,276 16 ± 1 54307 ,54759 t2 26,21 041 ± 58936 00,852 96 Reduced Chi-Sqr 1,144 1E-4 R-Square (COD) 0,9933 Ad j. R-Square 0,993 01 k 1 (10 -3 s -1 ) k 2 (10 -3 s -1 ) A 1 A 2 A th R 2 1 st circle 3.49 3.49 0.266 0.282 - 0.0003 0.99 2 nd circle 3.72 3.72 0.267 0.280 0.002 0.99 3 rd circle 3.82 3.82 0.274 0.276 0.004 0.99 [a] 1.5×10 -5 M in MeCN, 293 K. Visible lig ht : 565 nm , 84 mW/cm 2 , 8.4 In -situ NMR S p ectra 204 8.4 In -s itu NMR Spectra Figure 8.13 470 MHz 19 F NMR spectra of N5 in CD 3 CN ( c = 1×10 -2 M) a t 23 8 K. (UV li ght : 365 nm, 3.86 m W/cm 2 , 500 MHz Bruker NMR spectrom eter , 2.5 h m easurements, 120 sp ectra were obtai ned.) a. I nitial state: b. After 1 m i n of 365 nm i rradiation : c. After 3 m in of 365 nm irradiati on: d. After 10 m in of 365 nm irr adiatio n: e. PSS (after 32 min of 365 nm irradiation, CF : TC : TT : AP = 10:60:8: 22, peak s at around -115.4 ppm are decom position prod ucts after long tim e irradiation) : -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm CF -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm TC TC -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm AP TT -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm 8 Appendix 205 f. after 11 m in in the dark ( CF : TC : TT : AP = 38:37 :9:16): g. after 70 m i n in the dark (CF : TC : TT : AP = 67 :9: 17 : 7): h. After 3 m in of 365 nm i rradiation ( CF : TC : TT : AP = 12: 64 : 11 :13): i. After 22 m in of 365 nm ir radiation (CF : TC : TT : A P = 9:53:11:27): -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm -112.0 -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm -112.5 -113.0 -113.5 -114.0 -114.5 -115.0 -115.5 -116.0 ppm 8.4 In -situ NMR S p ectra 206 Figure 8.14 470 MHz 19 F NMR spe ctra of N6 at 238 K in CD 3 CN. (c = 1×10 -2 M. UV: 365 nm, 3.86 m W/cm 2 . 420 nm light : 8.10 m W/cm 2 . 500 MHz Bruker NMR spectrometer. 4 h measurem ent s, 200 spectra were obtained.) a. I nitial state: b. After 1 m i n of 365 nm i rradiation : c. After 4 m in of 365 nm irradiati on: d. After 11 m in of 365 nm irr adiatio n: e. PSS (after 30 min of 365 nm irradiation, CF : TC : TT : AP = 15:72:5: 8 ): 8 Appendix 207 f. after 22 m in in the dark ( CF : TC : TT : AP = 42:52 :5:1): g. af ter 130 m in in the dark (CF : TC : TT : AP = 87:6:7:0): h. PSS (after 26 m in of 420 nm irradiation, CF : TC : TT : AP = 92:3 :0:5) 8.4 In -situ NMR S p ectra 208 i. after 19 m i n in the dark (CF : TC : TT : AP = 94:6 : 0:0): Figure 8.15 470 MHz 19 F NMR spectra of N7 at 238 K in CD 3 C N. ( c = 1×10 - 2 M, LED light: 365 nm, 3.86 m W/cm 2 . 420 nm, 8.10 m W/cm 2 . 455 nm, 4.30 mW/cm 2 . 505 nm, 2.37 mW/cm 2 . 500 MHz Bruker NMR spectrom et er. 3 h m easurem ents, 142 spectra we re obtained.) a. I nitial state (peaks at around - 115.6 and -116.0 ppm ar e byprod ucts from t he synthesis ) : b. After 1 m i n of 365 nm irradiation: c. After 2 m in of 365 nm irradia tion: 8 Appendix 209 d. After 10 m i n of 365 nm irradiation: e. PSS (after 2 4 m in of 365 nm i rradiation, CF : TC : TT : AP = 32 :53:13:2): f. After 11 m in i n the d ark (CF : T C : TT : A P = 61:25 :13:1): g. A fter 40 m in in the da rk (CF : TC : TT : AP = 80:6:14:0): 8.4 In -situ NMR S p ectra 210 h. After 12 m in of 420 nm irradiation (CF : TC : TT : AP = 53:34 :9:4): i. 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I would also like to thank all employe es of the analytic centers of the I nstitut für Chemie, Technische Univ ersität Berlin for their excellent work and strong support . I would li ke to thank Dr. Sebastian Kemper and Ms. Samantha Voges for their p rofessional help with the NMR spectrometer . I thank D r. Maria S chlangen and M r. Marc Griffel for the measurements on Mass analy sis. I n addition, I would li ke to thank Ms. Barbara-Cornelia Fischer and Ms. Juana Krone for the I R and elemental analysis measurements. I would like to thank all the members of the Rück -Braun group for their support and help. I thank Gregor, Tino, S ebastian and Pierre for useful discussion, friendly help and int eresting chatting. I thank Miro for the introduc tion of the institute. I thank Nandor and Marina for the introduction of the UV /Vis measure m ents. I thank J unjie for chatti ng with me in Chinese a nd having fun to gether after w ork. I would also like to thank Christoph for his introduction of naphthopy rans. I thank m y master students : Phil ipp and Toan. Moreov er, I a m grateful to have m emorable lunch time with Gregor, Tino, S ebastian, Nandor, Philipp , Marie, Vale und P ierre ® . I will miss the happy parties together with them befor e Coronavirus, and I hope I can drink Glühwein with them again durin g the Christmas after the disapearance of Corona virus. I would li ke to thank m y famil y, m y friends and m y wif e. 感谢我的爸爸 ，祁勇；感谢我的妈 妈，丁继武；感谢我的老婆许聪慧的支持与陪伴，爱你么么哒。另外，我还要感谢我的其 他亲戚朋友的支持和帮助，谢谢你们。 219 Finally , I would li ke to thank the China S cholarship Council (CSC) for the financial support with grant No. 20160636012 6. I would also li ke to thank the financial support from the ST IB ET program of Technische Universität Berlin and th e DAAD. 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