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1
A wa e educ ion p ocess pe o med by zinc me al in e y mild
condi ions
Ma ía J. Rome o,ᵃ Rosa Ped ido,*ᵃ Ana M. González-Noya,ᵇ Miguel Ma ínez-Cal o,ᵃ Guille mo
Za agozaᶜ and Manuel R. Be mejo*ᵃ
Recei ed (in XXX, XXX) X h XXXXXXXXX 200X, Accep ed X h XXXXXXXXX 200X
5
Fi s published on he web X h XXXXXXXXX 200X
DOI: 10.1039/b000000x
Wa e educ ion can be elec ochemically p omo ed by
zinc unde e y mild condi ions, as demons a ed by he
o ma ion o he complex [Zn(H
2
O)
6
][Zn
3
(SAlDs)
3
(
μ
3
-O)],
10
whose anion consis s o a Zn
3
O
4
clus e inco po a ing a
μ
3
-oxo anion.
The s udy o polynuclea coo dina ion compounds wi h no el
me al co es1 has expe ienced inc eased in e es in he las wo
15
decades due o hei po en ial applica ions as unc ional
ma e ials,2 ca alys s3 o models o ac i e si es in
me alloenzymes.4 In pa icula , nume ous zinc clus e complexes
ha e been assembled in o de o ep oduce some enzyma ic
beha iou s.5 Fo example, i is well known ha zinc(II) ions can
20
p omo e hyd oly ic eac ions by coo dina ing a nucleophilic
wa e o lowe i s pKa wi hou he complica ion o adical
eac ions.6 Addi ionally, he abili y o zinc(II) o adop a a ie y
o coo dina ion numbe s and geome ies, combined wi h i s
apid ligand exchange capaci y, allows i o accommoda e he
25
s uc u al ea angemen s ha mus occu du ing he cou se o
many chemical eac ions.2,4
Nume ous examples o polynuclea zinc complexes ea u ing
oxo anions coo dina ed o he me al cen es ha e been epo ed
o da e. Mos o hese compounds we e syn hesized by
30
employing chemical me hods ha in ol e he in oduc ion o
dioxygen,7 wa e 8 o ca bon dioxide9 in o he eac ion media
o /and by using diffe en basic agen s.7,10 In hese cases, zinc
me al o zinc coo dina ion compounds hemsel es a e able o
ca y ou elec on ans e o hyd olysis p ocesses, eleasing in o
35
he media oxo o hyd oxo anions ha could ac as po en ial
ligands.
On he o he hand, he efficien ca aly ic educ ion o wa e by
zinc me al o he gene a ion o hyd ogen is one o he mos
challenging chemical ans o ma ions in indus y a p esen ,
40
since hyd ogen could be conside ed as a clean ene gy sou ce i i
is p oduced using enewable elec ici y. This eac ion is ca ied
ou by employing special condi ions, which in ol e he ca e ul
con ol o ac o s such as p essu e and empe a u e11 o he
p esence o sui able ca alys s (Pd, P , Ni, Rh, Mn).12
45
Du ing he las ew decades ou g oup and o he s ha e employed
Schiff base ligands de i ed om salicylaldehyde o assemble
polynuclea complexes.13 I is also well known ha zinc(II) ions
ha e a s ong affini y o a oma ic sul onamides.
Wi h he aim o p epa ing new polynuclea zinc complexes ha
50
po en ially could bind oxo anions and may ha e ca aly ic
ac i i y, we ha e designed he new ligand 5-(dime hylamino)-
N-(2-(2-hyd oxybenzylideneamino)phenyl)naph halene-1-
sul onamide, named H2L (Scheme 1).
He ein we epo a zinc clus e complex assembled a e a
55
wa e educ ion p ocess ca ied ou unde mild condi ions by
coo dina ed Zn2+ ions in an elec ochemical cell.
Equimolecula condensa ion o salicylaldehyde and N-(2-
aminophenyl)-5-(dime hylamino)-1-naph halenesul onamide
ga e ise o he [N2O] iden a e ligand H2L (Scheme 1).
60
Elec ochemical oxida ion o a zinc pla e14 in he p esence o a
degassed comme cial ace oni ile solu ion o H2L yielded he
neu al solid complex [Zn(H2O)6][Zn3(L)3(μ3-O)] (1), which was
eadily cha ac e ised by analy ical and spec oscopic echniques.
The MALDI-TOF mass spec um o 1 exhibi s peaks
65
co esponding o he [Zn(H2O)6][Zn3(L)3(μ3-O)] agmen a ion,
hus confi ming he p oposed molecula o mula in solu ion. The
s oichiome y o his compound was u he confi med by i s
mola conduc i i y alue, which is compa ible wi h a 1 a io; 1
elec oly e compound.15
70
Slow e apo a ion o he mo he liquo s yielded g een c ys als
co esponding o he complex [Zn(H2O)6][Zn3(L)3(μ3-O)]·
3CH3CN·H2O (1·3CH3CN·H2O), which was comple ely
cha ac e ised, including by X- ay diff ac ion. I should be no ed
ha his p ocess is o ally ep oducible and all a emp s o ob ain
75
he solid complex 1 o he c ys alline 1·3CH3CN·H2O unde he
same expe imen al condi ions ga e iden ical esul s.
The s uc u e o 1·3CH3CN·H2O consis s o a inuclea anionic
complex [Zn3(L)3(μ3-O)]2- and a hexaaquo ca ion [Zn(H2O)6]2+,
sol a ed by wo ace oni ile and h ee wa e molecules (Fig. 1 and
80
2). The anionic en i y [Zn3(L)3(μ3-O)]2- is buil by h ee
molecules o dianionic ligand [L]2- bound o h ee zinc(II) ions
h ough a [N2O] dono sys em, oge he wi h an oxo anion
coo dina ed in a μ3-b idging mode. Each phenol oxygen
es ablishes a μ2-oxo b idge be ween wo zinc cen es.
85
55
90
Scheme 1 Ligand H2L.
95
2
| Jou nal Name, [yea ],
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This jou nal is © The Royal Socie y o Chemis y [yea ]
5
10
15
Fig. 1 Ball and s ick ep esen a ion o he anionic clus e [Zn3(L)3(μ3-O)]2-
in 1·3CH3CN·H2O. The [Zn(H2O)6]2+ coun e ion, sol a e ace oni ile and
wa e molecules a e omi ed o cla i y.
20
25
Fig. 1 Ball and s ick ep esen a ion o he anionic clus e
30
[Zn3(L)3(m3-O)]2_ in 1_3CH3CN_H2O. The [Zn(H2O)6]2+
coun e ion,
sol a e ace oni ile and wa e molecules a e omi ed o
cla i y.
35
Fig. 2
Hyd ogen bonding in e ac ions be ween wo [Zn
3
(L)
3
(
μ
3
-
O)]
2-
molecules and he [Zn(H
2
O)
6
]
2+
ca ion.
This coo dina ion mode allows he assembly o a Zn3O4 cen al
40
co e, which could be desc ibed as a pseudo-cube wi h a acan
posi ion a he opposi e e ex o he oxygen a om O1. The me al
and he phenol oxygen a oms in he Zn3O4 co e desc ibe one six-
membe ed me allacycle wi h a chai - ype con o ma ion (Fig. S2,
ESI), while he coo dina ion o he μ3-oxo anion gi es ise o
45
h ee ou -membe ed me allacycles, which co espond o he
h ee aces o he dis o ed pseudo-cube.
The zinc(II) ions a e loca ed in [N2O3] pen acoo dina ed
en i onmen s in he inuclea clus e , wi h dis o ed squa e-
py amidal geome ies, acco ding o hei calcula ed τ pa ame e s
50
(τ1 = 0.28, τ2 = 0.04, τ3 = 0.15).16 A weak in amolecula
in e ac ion be ween he Zn2 a om and one oxygen a om om he
dansyl g oup [Zn2···O52, 2.681(3) A˚] is also obse ed (Fig. 1).
The Zn–N and Zn–O bond dis ances a e simila o hose ound in
o he salen polynuclea Zn(II) complexes.5d,17–19 The Zn···Zn
55
bond dis ances in his anionic clus e (close o 3.1 Å) a e sligh ly
longe han he sum o he an de Waals adii o wo zinc a oms
(2.8 Å).20,21 These dis ances a e in he o de o hose ound in
o he polynuclea zinc(II) complexes wi h μ2-oxo,17 μ3-oxo,22 and
μ4-oxo23 b idges.
60
The hexaaquo coun e ion appea s be ween wo clus e molecules
o [Zn3(L)3(μ3-O)]2- (Fig. 2) due o he es ablishmen o nume ous
hyd ogen bond con ac s (Table S2, ESI).
A his poin he o igin o he μ3-oxo anion in compound 1 mus
be analysed. Conside ing all he li e a u e epo s conce ning he
65
ca aly ic ac i i y o Zn2+,24 we p opose ha his anion was
gene a ed in si u by means o a wa e educ ion p ocess ca alysed
by zinc(II) ions du ing he elec ochemical syn hesis o he
zinc(II) complex. To confi m ou p oposal, he elec ochemical
syn hesis was epea ed unde an ine a mosphe e, bu employing
70
comple ely d y ace oni ile. Unde hese condi ions a complex
wi h a Zn2(L)2 s oichiome y (2) was isola ed bu his apidly
e ol ed in solu ion o o m complex 1.25 I is clea om hese
findings ha he absence o wa e in he medium a oided he
ca aly ic con e sion o he dime in o he inuclea clus e and
75
he e o e ha he p esence o wa e is essen ial o gene a e
complex 1.
A possible mechanism o he o ma ion o complex 1 would
in ol e wo diffe en edox p ocesses (Scheme 2). In he fi s
s age, he zinc anode unde goes an oxida ion o gene a e Zn2+
80
ions, while he sul onamide N–H and phenoxo O–H bonds om
he ligand H2L a e educed o gi e he bidep o ona ed [L]2-. The
coo dina ion o wo bidep o ona ed ligands o wo Zn(II) ions
would esul in a dime ic compound wi h μ2-phenoxo b idges
be ween he wo me al cen es (I).26 The pa icula p e e ences o
85
Zn(II) in e ms o coo dina ion numbe would p o ide a sui able
ke nel o coo dina ion o one addi ional wa e molecule om he
medium o one o he me al cen es, hus one o he zinc(II) ions
achie es a pen acoo dina ed en i onmen (II).24 Since he elec o-
chemical oxida ion o he Zn pla e would con inue in he cell
90
once he Zn2(L)2 dime is o med, aqueous Zn(II) ions
{[Zn(H2O)6]2+} and wo elec ons a e eleased in o he solu ion.
One o hese elec ons would pe o m a me al–wa e bond
educ ion, gene a ing a coo dina ed hyd oxo anion (III).27 This
hyd oxo anion, which ac s as a μ2-oxo b idge, would be able o
95
inco po a e a new zinc(II) ion and a hi d anionic ligand uni in o
he complex (IV). In he final s ep, he inuclea complex would
expe ience a second educ ion on he zinc–OH bond, c ea ing an
O2- anion ha would comple e he pen acoo dina ed en i onmen
o he hi d me al cen e ([Zn3(L)3(μ3-O)]2-).
100
This jou nal is © The Royal Socie y o Chemis y [yea ]
Jou nal Name, [yea ],
[ ol]
, 00–00 |
3
Scheme 2 P oposed mechanism o he o ma ion o 1.
The coexis ence o Zn2+, e-, H2O, Zn2L2 and L2- in solu ion
5
makes he o ma ion o compound 1 possible, wi h he oxo
anion being he key piece in he assembly o he inuclea
clus e . We mus s ess ha all he ca aly ic educ ion s ages
yield hyd ogen gas, which is libe a ed om he ca hode
h oughou he p ocess.
10
An elec ochemical wa e educ ion p ocess ca alysed by Zn2+
ions in he p esence o he ligand H2L leads o he o ma ion
o a μ
3
-oxo anion, which ac s as he key componen in he
assembly o he inuclea zinc clus e [Zn3(L)3(μ
3
-O)]2-.
The main ad an ages o he elec ochemical me hod o
15
achie e he wa e educ ion in he p esence o zinc me al a e
(i) i s ep oducibili y and (ii) he use o e y mild condi ions,
since he eac ion occu s in he absence o educing agen s,
basic eagen s o ex e nal ca alys s.
20
Financial suppo om Xun a de Galicia
(INCITE09E2R209074ES), Minis e io de Educación y
Ciencia and ERDF (EU) (CTQ2007-62185/BQU). We also
acknowledge EU COST D31 Ac ion “Func ional Helica es”
(D31/0008/04). R. Ped ido hanks Xun a de Galicia o an
25
“Isid o Pa ga Pondal” con ac .
No es and e e ences
a Depa amen o de Química Ino gánica, Facul ade de Química,
Uni e sidade de San iago de Compos ela, San iago de Compos ela,
30
Galicia, E-15782, Spain. Fax: +34 981597525; Tel: +34 981563100; E-
mail: osa.ped [email protected]
b Depa amen o de Química Ino gánica, Facul ade de Ciencias,
Uni e sidade de San iago de Compos ela, Lugo, Galicia, E-27002.
35
C ys al da a o 1·3CH₃CN·H₂O: (C₈₁H₈₀N₁₂O₁₄S₃Zn₃.₅₀), Mw =1770.65,
c ys al dimensions: 0.25 x 0.24 x 0.24 mm, iclinic, P-1, a = 15.344(5),
b = 16.139(5), c = 18.408(6) A˚ , a = 75.772(5)1, b = 81.362(5)1, g =
70.021(4)1, V = 4142(2) A˚ 3, Z = 1, m = 1.148 mm⁻¹, F(000) = 1830.
Radia ion l(Mo-Ka) = 0.71073 A˚, T = 293(2) K, eflec ions
40
collec ed/unique 34 313/15 033 (Rin = 0.0540), R (all da a) =0.0953,
wR (all da a) = 0.146, GOF = 0.994, max./min. esidual densi y 0.859/-
0.648 e A˚ -3. CCDC 766560.
1 (a) J.-M. Lehn, Sup amolecula Chemis y: Concep s And Pe spec i es,
45
Wiley-VCH, Weinheim, 1995; (b) E. C. Cons able, in Comp ehensi e
Sup amolecula Chemis y (Eds: J. L. A wood, J. E. D. Da ies, J-M
Lehn, D. D. Macnicol, F. Vög le), Pe gamon, Ox o d (1996).
2 (a) X.-H. Bu, H. Mo ishi a, K. Tanaka, K. Bi adha, S. Fu usho, M.
Shionoya, Chem. Commun. 2000, 971-972; (b) M. J. Hannon, V.
50
Mo eno, M. J. P ie o, E. Mold heim, E. Sle en, I. Meis e mann, C. J.
Isaac, K. J. Sande s, A. Rodge , Angew. Chem. In . Ed. 2001, 40, 880-
884; (c) D. Ga eschi, R. Sessoli, Angew. Chem. In . Ed. 2003, 42, 268-
297; (d) M. J. Hannon, L. J. Childs, Sup am. Chem. 2004, 16, 7-22; (e)
C. Pigue , M. Bo ko ec, J. Hamacek, K. Zecke , Coo d. Chem. Re .
55
2005, 249, 705-726.
3 (a) E. Shi akawa, T. Ku ahashi, H. Yoshida, T. Hiyama, Chem.
Commun. 2000, 1895-1896; (b) J. And ieu, P. B auns ein, F. Naud, R.
D. Adams, J. O ganome . Chem. 2000, 601, 43-50; (c) P. B auns ein, F.
Naud, Angew. Chem. In . Ed. 2001, 40, 680-699.
60
4 (a) W. N. Lipscomb, N. S ä e , Chem. Re . 1996, 96, 2375-2433; (b) R.
K ame , T. Gajda, Pe sp. Bioino g. Chem. 1999, 4, 209-240; (c) H.
Ca lsson, M. Haukka, E. No dlande , Ino g. Chem. 2004, 43, 5681-
5687; (d) M. Fondo, A. M. Ga cía-Deibe, N. Ocampo, J. Sanma ín, M.
R. Be mejo, Dal on T ans. 2004, 2135-2141; (e) J. Chen, X. Wang, Y.
65
Zhu, J. Lin, X. Yang, Y. Li, Y. Lu, Z. Guo, Ino g. Chem. 2005, 44
3422-3430; ( ) M. Ja enma k, S. Kappen, M. Haukka, E. No dlande ,
Dal on T ans. 2008, 993-996.
5 (a) F. Meye , P. Ru sch, Chem. Commun. 1998, 1037-1038; (b) C. He,
S. J. Lippa d, J. Am. Chem. Soc. 2000, 122, 184-185; (c) A. T ösch, H.
70
Vah emkamp, Ino g. Chem. 2001, 40, 2305-2311; (d) M. Dö ing, M.
Ciesielski, O. Wal e , H. Gö ls, Eu . J. Ino g. Chem. 2002, 1615-1621;
(e) K. Selmeczi, C. Michel, A. Mile , I. Gau ie -Luneau, C. Philouze, J.-
L. Pie e, D. Schniede s, A. Rompel, C. Belle, Chem. Eu . J. 2007, 13,
9093-9106.
75
6 (a) O. I anzo, A. Y. Ko ale ski, J. R. Mo ow, J. P. Richa d, J. Am.
Chem. Soc. 2003, 125, 1988-1993; (b) G. Feng, J. C. Ma eque-Ri as, N.
H. Williams, Chem. Commun. 2006, 1845-1847; (c) T. Ohshima, T.
Iwasaki, K. Mashima, Chem. Commun. 2006, 2711-2713; (d) C. T. Liu,
A. A. Ne e o , R. S. B own, Ino g. Chem. 2007, 46, 1778-1788; (e) L.
80
R. Gahan, S. J. Smi h, A. Ne es, G. Schenk, Eu . J. Ino g. Chem. 2009,
2745-2758.
7 R. P. Da ies, D. J. Lin on, R. Snai h, A. E. H. Whea ley, Chem.
Commun. 2000, 1819-1820.
8 (a) C.-F. Lee, K.-F. Chin, S.-M. Peng, C.-M. Che, J. Chem. Soc., Dal on
85
T ans. 1993, 467-470; (b) F. A. Co on, L. M. Daniels, L. R. Fal ello, J.
H. Ma onic, C. A. Mu illo, X. Wang, H. Zhou, Ino g. Chim. Ac a, 1997,
266, 91-102.
9 A. Bel o e, F. Calde azzo, U. Engle , J. S ähle, Ino g. Chem. 1991, 30
3778-3781.
90
10 K. Tozuda, K. Okamo o, T. Cono, Ino g. Chem. 2000, 39, 333-339.
11 M. L. Coleman, T. J. Shephe d, J. J. Du ham, J. E. Rouse, G. R. Moo e,
Anal. Chem. 1982, 54, 993-995.
12 (a) J. A. Ka hu, Anal. Chem. 1997, 69, 4728-4730; (b) S.
Mukhopadhyay, G. Ro henbe g, H. Wiene , Y. Sasson, New. J. Chem.
95
2000, 24, 305-308 and e e ences he ein; (c) M. R. Be mejo, A. Ga cía-
Deibe, J. Sanma ín, A. Sousa, N. Au angzeb, C. E. Hulme, C. A.
McAuli e, R. G.; P i cha d, M. Wa kinson, J. Chem. Soc., Chem.
Commun., 1994, 5, 645-646.
13 (a) J. Sanma ín, M. R. Be mejo, A. M. Ga cía-Deibe, O. Pi o, E. E.
100
Cas ellano, Chem. Commun. 1999, 1953-1954; (b) T. Yu, K. Zhang, Y.
4
| Jou nal Name, [yea ],
[ ol]
, 00–00
This jou nal is © The Royal Socie y o Chemis y [yea ]
Zhao, C. Yang, H. Zhang, D. Fan, W. Dong, Ino g. Chem. Commun.
2007, 10, 401-403; (c) A. W. Kleij, M. Kuil, D. M. Tooke, A. L. Spek,
J. N. H. Reek, Ino g. Chem. 2007, 46, 5829-5831 and e e ences
he ein.
14 R. Ped ido, M. J. Rome o, M. R. Be mejo, A. M. González-Noya, I.
5
Ga cía-Lema, G. Za agoza, Chem. Eu J. 2008, 14, 500-512.
15 W. J. Gea y, Coo d. Chem. Re . 1971, 7, 81-122.
16 A. W. Addison, T. N. Rao, J. Reedijk, J. Van Rijn, G. C. Ve schoo , J.
Chem. Soc., Dal on T ans. 1984, 1349-1356.
17 (a) J. Sanma ín, M. R. Be mejo, A. M. Ga cía-Deibe, A. L. Llamas-
10
Saiz, Chem. Commun. 2000, 795-796; (b) J. Sanma ín, M. R. Be mejo,
A. M. Ga cía-Deibe, I. M. Ri as, A. R. Fe nández, J. Chem. Soc.,
Dal on T ans. 2000, 4174-4181.
18 A. S. Bu lo , Y. V. Koshchienko, K. A. Lyssenko, I. S. Vasilchenko,
Y. E. Alexee , I. G. Bo odkina, M. Y. An ipin, A. D. Ga no skii, J.
15
Coo d. Chem. 2008, 61, 85-91.
19 (a) M. Miku iya, N. Tsu u, S. Ikemi, S. Ikenoue, Chem. Le . 1998,
879-880; (b) G. Xu, L. Liu, L. Zhang, G. Liu, D. Jia, J. Lang, S uc .
Chem. 2005, 16, 431.
20 A. Bondi, J. Phys. Chem. 1964, 68, 441-451.
20
21 J. E. Huheey, E. A. Kei e , R. L. Kei e , Ino ganic Chemis y:
P inciples o S uc u e and Reac i i y, 4a Ed., Ha pe Collins College
Publishe , New Yo k, 1993.
22 (a) R. Ki au a, G. Onoyama, H. Sakamo o, R. Ma suda, S.-I. No o, S.
Ki agawa, Angew. Chem. In . Ed. 2004, 43, 2684-2687; (b) C. Maxim,
25
T. D. Pasa oiu, V. C. K a so , S. Sho a, C. A. Mu yn, R. E. P.
Winpenny, F. Tuna, M. And uh, Ino g. Chim. Ac a, 2008, 361, 3903-
3911.
23 N. Lalio i, C. P. Rap opoulou, A. Te zis, A. E. Alie , S. P. Pe lepes, I.
P. Ge o hanassis, E. Manessi-Zoupa, Chem. Commun. 1998, 1513-
30
1514.
24 E. Kimu a, E. Kiku a, J. Biol. Ino g. Chem. 2000, 5, 139-155.
25 The e olu ion o Zn2(L)2 (2) o clus e 1 was ollowed by 1H NMR (See
Fig. S5 in ESI).
26 M. Do ing, M. Ciesielski, O. Wal e and H. Go ls, Eu . J. Ino g.
35
Chem., 2002, 1615–1621.
27
M. He nick and C. A. Fie ke, A ch. Biochem. Biophys., 2005,
433,
71–84.
