Synthesis, Characterization, and Preliminary In Vitro Anticancer Activity of Zinc Complexes Containing Amino Acid-Derived Imidazolium-Based Dicarboxylate Ligands

Academic Edi o s: Sami Ache a and
Sung-Kun (Sean) Kim
Recei ed: 4 Ma ch 2025
Re ised: 27 Ma ch 2025
Accep ed: 27 Ma ch 2025
Published: 30 Ma ch 2025
Ci a ion: Ca asco, C.J.; Pas o , A.;
Conejo, M.d.M.; Ál a ez, E.;
Calde ón-Mon año, J.M.;
López-Láza o, M.; Galindo, A.
Syn hesis, Cha ac e iza ion, and
P elimina y In Vi o An icance
Ac i i y o Zinc Complexes
Con aining Amino Acid-De i ed
Imidazolium-Based Dica boxyla e
Ligands. In . J. Mol. Sci. 2025,26, 3202.
h ps://doi.o g/10.3390/
ijms26073202
Copy igh : © 2025 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license
(h ps://c ea i ecommons.o g/
licenses/by/4.0/).
A icle
Syn hesis, Cha ac e iza ion, and P elimina y In Vi o An icance
Ac i i y o Zinc Complexes Con aining Amino Acid-De i ed
Imidazolium-Based Dica boxyla e Ligands
Ca los J. Ca asco 1, An onio Pas o 1, Ma ía del Ma Conejo 1, Eleu e io Ál a ez 2,
José Manuel Calde ón-Mon año 3, Miguel López-Láza o 3and Agus ín Galindo 1,*
1Depa amen o de Química Ino gánica, Facul ad de Química, Uni e sidad de Se illa, 41071 Se illa, Spain;
[email p o ec ed] (C.J.C.); [email p o ec ed] (A.P.); [email p o ec ed] (M.d.M.C.)
2Ins i u o de In es igaciones Químicas, CSIC-Uni e sidad de Se illa, A da. Amé ico Vespucio 49,
41092 Se illa, Spain; [email p o ec ed]
3Depa amen o de Fa macología, Facul ad de Fa macia, Uni e sidad de Se illa, 41012 Se illa, Spain;
[email p o ec ed] (J.M.C.-M.); mlopezlaza [email p o ec ed] (M.L.-L.)
*Co espondence: [email p o ec ed]
Abs ac : Coo dina ion polyme s con aining zinc and imidazolium-based dica boxyla e
ligands, [L
R
]
−
, we e syn hesized by eac ing zinc ace a e wi h HL
R
compounds, 1. The
esul ing complexes we e cha ac e ized and s uc u ally iden i ied using single-c ys al
X- ay di ac ion, e ealing polyme ic s uc u es o he complexes [Zn(L
R
)
2
]
n
(R = Gly,
2a;
β
Ala, 2b) and [Zn(L
Leu
)
2
(H
2
O)
2
]
n
(2c). In hese s uc u es, he [L
R
]
−
ligands adop a
b idging monoden a e
µ
-
κ1
-O
1
,
κ1
-O
3
coo dina ion mode, esul ing in dis o ed e ahed al
(2a,2b) o oc ahed al (2c) geome ies a ound he zinc cen e . When he syn hesis was
ca ied ou in he p esence o amino acids, mixed ligand complexes [Zn(L
R
)(aa)(H
2
O)]
n
(R = aa = Val, 2d, and R = aa = Ile, 2e) we e o med. Complexes 2d–2e we e also s uc u ally
cha ac e ized using single-c ys al X- ay c ys allog aphy, e ealing ha he ligand [L
R
]
−
main ained he same coo dina ion mode, while he zinc cen e adop ed a i e-coo dina ed
geome y. The cy o oxic ac i i y o complexes 2a–2e was e alua ed agains h ee cance
cell lines and one non-cance ous cell line. Rema kably, hese complexes exhibi ed highe
oxici y agains cance cells han agains he non-cance ous cell line, and hey showed
g ea e selec i i y han ca bopla in, a commonly used chemo he apy d ug. Al hough, in
gene al, hese complexes did no su pass he selec i i y o gemci abine, complex 2c s ood
ou o exhibi ing a selec i i y index alue simila o ha o gemci abine agains melanoma
cells. Among he se ies, compounds 2a–2c demons a ed he highes ac i i y, wi h 2a being
he only complex wi h some selec i e ac i i y agains lung cance . Complex 2b was he
mos ac i e, hough wi h low selec i i y, while complex 2c exhibi ed he highes selec i i y
o melanoma and bladde cance (selec i i y index o 3.0).
Keywo ds: zinc; an icance ; selec i i y; amino acid; imidazolium-dica boxyla e; X- ay
1. In oduc ion
The de elopmen o ansi ion me al complexes wi h an icance po en ial con inues
o be a dynamic ield o esea ch [
1
–
4
]. A key goal in his a ea is o iden i y compounds
wi h low oxici y owa d non-cance ous cells, making me als such as coppe [
5
] and
zinc [
6
,
7
] pa icula ly a ac i e o s udy due o hei ela i ely low oxici y. Zinc, in
pa icula , is an essen ial ace elemen in he human body because i is a pa o nume ous
enzymes [
8
,
9
] and plays an impo an ole in se e al biological p ocesses [
10
,
11
]. The
In . J. Mol. Sci. 2025,26, 3202 h ps://doi.o g/10.3390/ijms26073202
In . J. Mol. Sci. 2025,26, 3202 2 o 13
coo dina ion chemis y o Zn
2+
is ich and e sa ile, wi h a wide ange o well-cha ac e ized
complexes in ol ing O-, N- and S-dono ligands [
12
]. Fu he mo e, i s d
10
con igu a ion
suppo s a ious s able coo dina ion geome ies—such as e ahed al, igonal bipy amidal,
and oc ahed al—and, in gene al, he esul ing complexes a e suscep ible o easy ligand
exchange [13].
P e iously, we syn hesized and cha ac e ized zinc complexes wi h imidazolium-based
dica boxyla e amino acid-de i ed ligands [
14
], as well as ela ed sil e de i a i es ha
exhibi ed an imic obial ac i i y [
15
]. Bo h sys ems showed wa e solubili y and biocom-
pa ibili y [
14
], making hem p omising candida es o u he in es iga ion in an icance
applica ions. He e, we expand his se ies o include new zinc complexes: [Zn(L
R
)
2
]
n
(
R = Gly
,2a, and
β
Ala, 2b), [Zn(L
Leu
)
2
(H
2
O)
2
]
n
(2c), and [Zn(L
R
)(aa)(H
2
O)]
n
(
R = aa = Val
,
2d, and R = aa = Ile, 2e). Con inuing ou in e es in amino acid-de i ed ansi ion me al
complexes [
15
–
18
] and hei applica ions as an imic obial [
19
,
20
] and an icance agen s [
21
],
we now epo on he an icance ac i i y o hese zinc complexes
(2a–2e)
agains h ee
human cance cell lines: melanoma cells (MeWo), lung adenoca cinoma (A549), and blad-
de cance cells (T24). These cance s a e among he mos common in he wo ld and ha e
high mo ali y a es in ad anced s ages [
22
]. Lung cance emains he leading cause o
cance - ela ed mo ali y wo ldwide [
22
], wi h app oxima ely 40% o pa ien s diagnosed
a he me as a ic s age, whe e he i e-yea su i al a e is below 10%. Bladde cance ,
al hough associa ed wi h high su i al a es in he ea ly s ages, has a d ama ically educed
i e-yea su i al a e o less han 9% once me as asized. Melanoma, while o en ea able
in he ea ly s ages, also shows a subs an ial d op in p ognosis a he me as a ic s age, wi h
a i e-yea su i al a e o app oxima ely 35% [
23
]. Cy o oxic ac i i y was e alua ed in
compa ison wi h ha o a human non-malignan cell line (skin cells, HaCaT) o de e mine
he apeu ic selec i i y. This cell line, de i ed om adul issue, is cha ac e ized by a apid
a e o cell p oli e a ion [
24
]. Mos cance pa ien s expe ience side e ec s du ing ea men ,
o en necessi a ing dose educ ions o e en discon inua ion. These side e ec s a ise because
mos cu en cance d ugs a ge apidly di iding cells, a ec ing bo h cance cells and
heal hy cells.
2. Resul s
2.1. Syn heses and Cha ac e iza ion o Complexes 2a–2e
The eac ion o zinc ace a e wi h HL
R
compounds, 1, p oduced complexes [Zn(L
R
)
2
]
(R = Gly, 2a;
β
Ala, 2b; Leu, 2c). The iso opic na u e o he Zn(II) d
10
con igu a ion al-
lowed he isola ion o hese compounds in he solid s a e as [Zn(L
R
)
2
]
n
(2a and 2b) o
[Zn(L
Leu
)
2
(H
2
O)
2
]
n
(2c) polyme ic complexes, ea u ing ou -and six-coo dina ed zinc en i-
onmen s, espec i ely (Scheme 1). Complexes 2a–2c we e ob ained as ai -s able c ys alline
whi e solids ha a e wa e -soluble bu spa ingly soluble in o ganic sol en s. In a ed
(FTIR) spec oscopy showed b oad abso p ions o he an isymme ic COO s e ching
ib a ions o he ca boxyla e g oups in he 1655–1600 cm
−1
ange, indica ing coo dina ion
o he [L
R
]
−
ligands o zinc (Figu e S1). This coo dina ion was e idenced by he shi o
lowe wa enumbe s in compa ison o hose o he HL
R
ligand p ecu so s, 1. Symme ic
COO ib a ions we e obse ed in he 1375–1350 cm
−1
ange, and he di e ence alues
o (
ν
COO
asym
-
ν
COO
sym
) sugges ed he
κ1
-O coo dina ion o he ca boxyla e g oup [
25
],
which was consis en wi h he s uc u al cha ac e iza ion discussed la e . Simila FTIR
abso p ion pa e ns ha e been epo ed o analogous zinc de i a i es [
16
,
26
,
27
]. The
1
H
and
13
C{
1
H} NMR spec a o 2a–2c (in deu e a ed wa e ; see Figu e S1) displayed signals
co esponding o he [L
R
]
−
ligands, wi h chemical shi s di e en om hose o he HL
R
p ecu so s, 1, due o zinc coo dina ion [
28
,
29
]. The spec oscopic p ope ies o complex 2a
a e simila o hose epo ed in he bibliog aphy [26,30,31].
In . J. Mol. Sci. 2025,26, 3202 3 o 13
In .J.Mol.Sci.2025,26,xFORPEERREVIEW3o 14


p ecu so s,1,due ozinccoo dina ion[28,29].Thespec oscopicp ope ieso complex2a
a esimila  o hose epo edin hebibliog aphy[26,30,31].
Whenzincace a ewas eac edwi hHLR,1,in hep esenceo oneequi alen o an
aminoacid,L‐ alineo L‐isoleucine,complexes2dand2ewe eob ained, espec i ely
(Scheme2).Theywe eiden i iedin hesolids a easpolyme iccomplexes
[Zn(LR)(aa)(H2O)]n(R=aa=Val,2d,andR=aa=Ile,2e).Complexes2dand2ewe ealso
ob ainedasai ‐s ablewa e ‐solublec ys allinewhi esolids ha a espa inglysolublein
o ganicsol en s.Thei FTIRspec ashowedca boxyla es e ching ib a ions,againcon‐
sis en wi hκ1‐Ocoo dina ion(Figu eS1),con i medby hes uc u alcha ac e iza iono 
2dand2e(seebelow).The1Hand13C{1H}NMRspec ao  hesecomplexes,indeu e a ed
wa e ,includedsignals o bo h he[LR]−ligandsand hecoo dina edaminoacid(Figu e
S1).Fo example, hesec‐bu ylg oupo  hecoo dina edaminoacidIlein2ewasclea ly
iden i iedbyi scha ac e is icsignalsobse edin heNMRspec a(assignmen sde ailed
in heSec ion3andFigu eS1).

Scheme1.Syn hesiso complexes2a–2c(inE OH/H2Oa 70°C o 1h).

Scheme2.Syn hesiso complexes2dand2e(inE OH/H2Oa 70°C o 1h).
2.2.S uc u alCha ac e iza iono Complexes2a–2e
Theiden i ica iono complexes2ascoo dina ionpolyme sin hesolids a ewascon‐
i medusingX‐ ayc ys allog aphy.Thes uc u eo complex2awassimila  o ha p e‐
iouslydesc ibed[30,31]andisno discussedinde ailhe e(seeFigu eS6andTablesS1
andS2in heSupplemen a yMa e ials).Thecompound[Zn(LβAla)2]n,2b,c ys allizesin
hemonoclinicCCspaceg oup, o mingaone‐dimensional(1D)coo dina ionpolyme 
ha ex endsalong hebaxis(Figu e1).Zincionsa elinkedbyb idging[LβAla]–anions
Scheme 1. Syn hesis o complexes 2a–2c (in E OH/H2O a 70 ◦C o 1 h).
When zinc ace a e was eac ed wi h HL
R
,1, in he p esence o one equi alen
o an amino acid, L- aline o L-isoleucine, complexes 2d and 2e we e ob ained, e-
spec i ely (Scheme 2). They we e iden i ied in he solid s a e as polyme ic complexes
[Zn(L
R
)(aa)(H
2
O)]
n
(R = aa = Val, 2d, and R = aa = Ile, 2e). Complexes 2d and 2e we e
also ob ained as ai -s able wa e -soluble c ys alline whi e solids ha a e spa ingly soluble
in o ganic sol en s. Thei FTIR spec a showed ca boxyla e s e ching ib a ions, again
consis en wi h
κ1
-O coo dina ion (Figu e S1), con i med by he s uc u al cha ac e iza ion
o 2d and 2e (see below). The 1H and 13C{1H} NMR spec a o hese complexes, in deu e -
a ed wa e , included signals o bo h he [L
R
]
−
ligands and he coo dina ed amino acid
(
Figu e S1
). Fo example, he sec-bu yl g oup o he coo dina ed amino acid Ile in 2e was
clea ly iden i ied by i s cha ac e is ic signals obse ed in he NMR spec a (assignmen s
de ailed in he Sec ion 3and Figu e S1).
In .J.Mol.Sci.2025,26,xFORPEERREVIEW3o 14


p ecu so s,1,due ozinccoo dina ion[28,29].Thespec oscopicp ope ieso complex2a
a esimila  o hose epo edin hebibliog aphy[26,30,31].
Whenzincace a ewas eac edwi hHLR,1,in hep esenceo oneequi alen o an
aminoacid,L‐ alineo L‐isoleucine,complexes2dand2ewe eob ained, espec i ely
(Scheme2).Theywe eiden i iedin hesolids a easpolyme iccomplexes
[Zn(LR)(aa)(H2O)]n(R=aa=Val,2d,andR=aa=Ile,2e).Complexes2dand2ewe ealso
ob ainedasai ‐s ablewa e ‐solublec ys allinewhi esolids ha a espa inglysolublein
o ganicsol en s.Thei FTIRspec ashowedca boxyla es e ching ib a ions,againcon‐
sis en wi hκ1‐Ocoo dina ion(Figu eS1),con i medby hes uc u alcha ac e iza iono 
2dand2e(seebelow).The1Hand13C{1H}NMRspec ao  hesecomplexes,indeu e a ed
wa e ,includedsignals o bo h he[LR]−ligandsand hecoo dina edaminoacid(Figu e
S1).Fo example, hesec‐bu ylg oupo  hecoo dina edaminoacidIlein2ewasclea ly
iden i iedbyi scha ac e is icsignalsobse edin heNMRspec a(assignmen sde ailed
in heSec ion3andFigu eS1).

Scheme1.Syn hesiso complexes2a–2c(inE OH/H2Oa 70°C o 1h).

Scheme2.Syn hesiso complexes2dand2e(inE OH/H2Oa 70°C o 1h).
2.2.S uc u alCha ac e iza iono Complexes2a–2e
Theiden i ica iono complexes2ascoo dina ionpolyme sin hesolids a ewascon‐
i medusingX‐ ayc ys allog aphy.Thes uc u eo complex2awassimila  o ha p e‐
iouslydesc ibed[30,31]andisno discussedinde ailhe e(seeFigu eS6andTablesS1
andS2in heSupplemen a yMa e ials).Thecompound[Zn(LβAla)2]n,2b,c ys allizesin
hemonoclinicCCspaceg oup, o mingaone‐dimensional(1D)coo dina ionpolyme 
ha ex endsalong hebaxis(Figu e1).Zincionsa elinkedbyb idging[LβAla]–anions
Scheme 2. Syn hesis o complexes 2d and 2e (in E OH/H2O a 70 ◦C o 1 h).
2.2. S uc u al Cha ac e iza ion o Complexes 2a–2e
The iden i ica ion o complexes 2as coo dina ion polyme s in he solid s a e was
con i med using X- ay c ys allog aphy. The s uc u e o complex 2a was simila o ha
p e iously desc ibed [
30
,
31
] and is no discussed in de ail he e (see Figu e S6 and Tables
S1 and S2 in he Supplemen a y Ma e ials). The compound [Zn(L
βAla
)
2
]
n
,2b, c ys allizes
in he monoclinic C
C
space g oup, o ming a one-dimensional (1D) coo dina ion polyme
ha ex ends along he baxis (Figu e 1). Zinc ions a e linked by b idging [L
βAla
]
−
anions
h ough ca boxyla e unc ionali ies ha adop a
µ
-
κ1
-O
1
,
κ1
-O
3
coo dina ion mode. This
esul s in asymme ic C-O bond leng hs wi hin ca boxyla e g oups (e.g., C(6)-O(1), 1.219(7)
and C(6)-O(2), 1.268(7) Å). O he selec ed s uc u al pa ame e s a e lis ed in Table S2. The
In . J. Mol. Sci. 2025,26, 3202 4 o 13
zinc ion exhibi s a e ahed al coo dina ion geome y, as occu ed in ela ed de i a i es
[Zn(L
R
)
2
]
n
(R =
i
P , CH
2
Ph) [
16
], wi h a ou -coo dina e geome y index o
τ4
= 0.85. Non-
coo dina ed C = O g oups in ca boxyla es o m weak non-classical C = O
. . .
H-C hyd ogen
bonds wi h adjacen 1D chains (Figu e S2), esul ing in he obse ed h ee-dimensional
(3D) c ys al packing a angemen (Figu e S3).
In .J.Mol.Sci.2025,26,xFORPEERREVIEW4o 14


h oughca boxyla e unc ionali ies ha adop aμ‐κ1‐O1,κ1‐O3coo dina ionmode.This
esul sinasymme icC‐Obondleng hswi hinca boxyla eg oups(e.g.,C(6)‐O(1),
1.219(7)andC(6)‐O(2),1.268(7)Å).O he selec eds uc u alpa ame e sa elis edinTable
S2.Thezincionexhibi sa e ahed alcoo dina iongeome y,asoccu edin ela edde‐
i a i es[Zn(LR)2]n(R=iP ,CH2Ph)[16],wi ha ou ‐coo dina egeome yindexo τ4=
0.85.Non‐coo dina edC=Og oupsinca boxyla es o mweaknon‐classicalC=O…H‐C
hyd ogenbondswi hadjacen 1Dchains(Figu eS2), esul ingin heobse ed h ee‐di‐
mensional(3D)c ys alpackinga angemen (Figu eS3).

Figu e1.1Dcoo dina ionpolyme o complex2balignedalong hebaxiswi hellipsoidso  he
ORTEP ep esen a iondisplayedwi h50%p obabili y.
Complex2cc ys allizesin he igonalspaceg oupP3221, o minga wo‐dimensional
(2D)me al–o ganic amewo kwhe ezincionsa ein e connec edbyb idging[LLeu]–an‐
ions h oughca boxyla e unc ionali ies.Theasymme icuni o 2cconsis so aZn2+ion,
a[LLeu]–ligand,andonewa e molecule(Figu e2a).Anin amolecula hyd ogenbondis
obse edbe ween hewa e ligandandoneoxygena omo  heca boxyla e(O(5)...O(2)
dis anceo 2.649(3)Å).Thezinccen e adop sadis o edoc ahed alcoo dina iongeom‐
e y,su oundedbysixoxygena oms om[LLeu]–,wa e ligands,and hei symme y‐
ela edcoun e pa s(Figu e2b).Eachca boxyla eg oupiscoo dina ed ozincinamono‐
den a emode,μ‐κ1‐O1,κ1‐O3,leading oasymme icC‐Odis ances(e.g.,C(5)‐O(1),1.254(3)
andC(5)‐O(2),1.237(3)Å).Theasymme yin hesecondca boxyla eg oupislessp o‐
nounced(C(11)‐O(3),1.252(3)andC(11)‐O(4),1.248(3)Å)because heO(4)a ompa ici‐
pa esinanin e molecula hyd ogenbondwi h hewa e ligand(O(5)...O(4)#1dis anceo 
2.683(3)Å).Theo he selec eds uc u alpa ame e sa esumma izedinTableS2.The
pseudo‐ ansa angemen o  heca boxyla eg oupsin he[LLeu]–ligand( o sionangleCca ‐
boxy–Cchi al–C′chi al–C′ca boxyo app oxima ely106°) acili a esasqua ela ice opology(sql,
Figu eS4c),c ea inga2Ddis ibu iono lamella shee s(Figu eS4a,b).
Complexes2dand2ec ys allizein hemonoclinicspaceg oupsC2andP21, espec‐
i ely.Theasymme icuni so 2dand2econ ainaZn(II)ion, heimidazoliumdica box‐
yla eligand([LVal]– o 2dand[LIle]– o 2e),abiden a eaminoacidligand( aline o 2d
andisoleucine o 2e),andonewa e molecule(Figu e3).Anin amolecula hyd ogen
bondisobse edwi hin hisuni be ween hecoo dina edaminoacidNH2g oupand
oneoxygena omo  heca boxyla eg oupo [LR]–(N(3)...O(1)dis anceo 2.962(4)Å o 2d
andN(3)...O(3)dis anceo 2.993(11)Å o 2e).Theg ow ho  heasymme icuni s o ms
1Dpolyme ics uc u es(Figu eS5a o 2d)inwhich heb idgingligands,[LVal]–and[LIle]–
,coo dina e ozincionsinamonoden a emode,μ‐κ1‐O1,κ1‐O3,asoccu edin2a–2c.In
bo hcomplexes, hezinccen e exhibi sabipy amidal igonalgeome yinwhich he
equa o ialposi ionsa eoccupiedby h eeoxygendono a omso wa e , heca boxyla e
Figu e 1. 1D coo dina ion polyme o complex 2b aligned along he baxis wi h ellipsoids o he
ORTEP ep esen a ion displayed wi h 50% p obabili y.
Complex 2c c ys allizes in he igonal space g oup P3
2
21, o ming a wo-dimensional
(2D) me al–o ganic amewo k whe e zinc ions a e in e connec ed by b idging [L
Leu
]
−
anions h ough ca boxyla e unc ionali ies. The asymme ic uni o 2c consis s o a Zn
2+
ion,
a [L
Leu
]
−
ligand, and one wa e molecule (Figu e 2a). An in amolecula hyd ogen bond is
obse ed be ween he wa e ligand and one oxygen a om o he ca boxyla e (O(5)
. . .
O(2)
dis ance o 2.649(3) Å). The zinc cen e adop s a dis o ed oc ahed al coo dina ion geome y,
su ounded by six oxygen a oms om [L
Leu
]
−
, wa e ligands, and hei symme y- ela ed
coun e pa s (Figu e 2b). Each ca boxyla e g oup is coo dina ed o zinc in a monoden a e
mode,
µ
-
κ1
-O
1
,
κ1
-O
3
, leading o asymme ic C-O dis ances (e.g., C(5)-O(1), 1.254(3) and
C(5)-O(2), 1.237(3) Å). The asymme y in he second ca boxyla e g oup is less p onounced
(C(11)-O(3), 1.252(3) and C(11)-O(4), 1.248(3) Å) because he O(4) a om pa icipa es in an
in e molecula hyd ogen bond wi h he wa e ligand (O(5)
. . .
O(4)#1 dis ance o 2.683(3)
Å). The o he selec ed s uc u al pa ame e s a e summa ized in Table S2. The pseudo- ans
a angemen o he ca boxyla e g oups in he [L
Leu
]
−
ligand ( o sion angle C
ca boxy
–C
chi al
–
C
′chi al
–C
′ca boxy
o app oxima ely 106
◦
) acili a es a squa e la ice opology (sql, Figu e
S4c), c ea ing a 2D dis ibu ion o lamella shee s (Figu e S4a,b).
Complexes 2d and 2e c ys allize in he monoclinic space g oups C
2
and P2
1
, espec-
i ely. The asymme ic uni s o 2d and 2e con ain a Zn(II) ion, he imidazolium dica boxy-
la e ligand ([L
Val
]
−
o 2d and [L
Ile
]
−
o 2e), a biden a e amino acid ligand ( aline o 2d
and isoleucine o 2e), and one wa e molecule (Figu e 3). An in amolecula hyd ogen
bond is obse ed wi hin his uni be ween he coo dina ed amino acid NH
2
g oup and
one oxygen a om o he ca boxyla e g oup o [L
R
]
−
(N(3)
. . .
O(1) dis ance o 2.962(4) Å o
2d and N(3)
. . .
O(3) dis ance o 2.993(11) Å o 2e). The g ow h o he asymme ic uni s
o ms 1D polyme ic s uc u es (Figu e S5a o 2d) in which he b idging ligands, [L
Val
]
−
and [L
Ile
]
−
, coo dina e o zinc ions in a monoden a e mode,
µ
-
κ1
-O
1
,
κ1
-O
3
, as occu ed
in 2a–2c. In bo h complexes, he zinc cen e exhibi s a bipy amidal igonal geome y in
which he equa o ial posi ions a e occupied by h ee oxygen dono a oms o wa e , he
ca boxyla e o isoleucine, and one o he ca boxyla e g oups o he [L
Val
]
−
o [L
Ile
]
−
ligand.
In 2d, he asymme y o he h ee ca boxyla e C-O dis ances is clea ly obse ed, while
in 2e, he asymme y is mo e p onounced in he isoleucine ligand (C(16)-O(5), 1.239(13)
In . J. Mol. Sci. 2025,26, 3202 5 o 13
and C(16)-O(6), 1.264(13) Å) compa ed o he [L
Ile
]
−
ligand. O he selec ed s uc u al
pa ame e s a e de ailed in Table S2. The 3D packing occu s h ough in e molecula hy-
d ogen bonds be ween he wa e ligand and one oxygen a om o he ca boxyla e g oup
( o 2d: O(7)
. . .
O(5)#1 and O(7)
. . .
O(3)#2 dis ances o 2.610(4) and 2.727(4) Å, espec i ely;
Figu e S5b).
In .J.Mol.Sci.2025,26,xFORPEERREVIEW5o 14


o isoleucine,andoneo  heca boxyla eg oupso  he[L
Val
]
–
o [L
Ile
]
–
ligand.In2d, he
asymme yo  he h eeca boxyla eC‐Odis ancesisclea lyobse ed,whilein2e, he
asymme yismo ep onouncedin heisoleucineligand(C(16)‐O(5),1.239(13)andC(16)‐
O(6),1.264(13)Å)compa ed o he[L
Ile
]
–
ligand.O he selec eds uc u alpa ame e sa e
de ailedinTableS2.The3Dpackingoccu s h oughin e molecula hyd ogenbondsbe‐
ween hewa e ligandandoneoxygena omo  heca boxyla eg oup( o 2d:
O(7)
...
O(5)#1andO(7)
...
O(3)#2dis anceso 2.610(4)and2.727(4)Å, espec i ely;Figu e
S5b).


(a)(b)
Figu e2.(a)ORTEP ep esen a iono  heasymme icuni o 2c,wi hellipsoidsdisplayedwi h50%
p obabili y.(b)Polyme ic2cg ow hshowing heoc ahed alcoo dina iono zinc.


(a)(b)
Figu e3.ORTEP ep esen a iono asymme icuni so 2d(a)and2e(b),wi hellipsoidsdisplayed
wi h50%p obabili y.
2.3.E alua iono An icance Ac i i y
Thecy o oxici yo complexes2wase alua edin i obyde e mining hehal inhib‐
i o yconcen a ions(IC
50
)agains  ou humancelllines:wild‐ ypeBRAFmelanoma
(MeWo),lungadenoca cinoma(A549),bladde cance (T24),andnon‐cance ousskin
ke a inocy es(HaCaT).TheIC
50
 alueswe ecalcula ed omcell iabili y aluesob ained
a e 72ho exposu eo  hed ug ocellsusing he esazu inassay.The iabili y esul s,
Figu e 2. (a) ORTEP ep esen a ion o he asymme ic uni o 2c, wi h ellipsoids displayed wi h 50%
p obabili y. (b) Polyme ic 2c g ow h showing he oc ahed al coo dina ion o zinc.
In .J.Mol.Sci.2025,26,xFORPEERREVIEW5o 14


o isoleucine,andoneo  heca boxyla eg oupso  he[L
Val
]
–
o [L
Ile
]
–
ligand.In2d, he
asymme yo  he h eeca boxyla eC‐Odis ancesisclea lyobse ed,whilein2e, he
asymme yismo ep onouncedin heisoleucineligand(C(16)‐O(5),1.239(13)andC(16)‐
O(6),1.264(13)Å)compa ed o he[L
Ile
]
–
ligand.O he selec eds uc u alpa ame e sa e
de ailedinTableS2.The3Dpackingoccu s h oughin e molecula hyd ogenbondsbe‐
ween hewa e ligandandoneoxygena omo  heca boxyla eg oup( o 2d:
O(7)
...
O(5)#1andO(7)
...
O(3)#2dis anceso 2.610(4)and2.727(4)Å, espec i ely;Figu e
S5b).


(a)(b)
Figu e2.(a)ORTEP ep esen a iono  heasymme icuni o 2c,wi hellipsoidsdisplayedwi h50%
p obabili y.(b)Polyme ic2cg ow hshowing heoc ahed alcoo dina iono zinc.


(a)(b)
Figu e3.ORTEP ep esen a iono asymme icuni so 2d(a)and2e(b),wi hellipsoidsdisplayed
wi h50%p obabili y.
2.3.E alua iono An icance Ac i i y
Thecy o oxici yo complexes2wase alua edin i obyde e mining hehal inhib‐
i o yconcen a ions(IC
50
)agains  ou humancelllines:wild‐ ypeBRAFmelanoma
(MeWo),lungadenoca cinoma(A549),bladde cance (T24),andnon‐cance ousskin
ke a inocy es(HaCaT).TheIC
50
 alueswe ecalcula ed omcell iabili y aluesob ained
a e 72ho exposu eo  hed ug ocellsusing he esazu inassay.The iabili y esul s,
Figu e 3. ORTEP ep esen a ion o asymme ic uni s o 2d (a) and 2e (b), wi h ellipsoids displayed
wi h 50% p obabili y.
2.3. E alua ion o An icance Ac i i y
The cy o oxici y o complexes 2was e alua ed
in i o
by de e mining he hal in-
hibi o y concen a ions (IC
50
) agains ou human cell lines: wild- ype BRAF melanoma
(MeWo), lung adenoca cinoma (A549), bladde cance (T24), and non-cance ous skin ke -
a inocy es (HaCaT). The IC
50
alues we e calcula ed om cell iabili y alues ob ained
a e 72 h o exposu e o he d ug o cells using he esazu in assay. The iabili y esul s,
summa ized in Table 1(as
µ
M concen a ions) and illus a ed in Figu e 4, also include
he alues o he selec i i y index (SI). The SI was calcula ed by di iding he IC
50
alue
in he non-cance ous cells by ha in he cance cells [
32
]. The highe he SI alue, he

In . J. Mol. Sci. 2025,26, 3202 6 o 13
highe he selec i i y o he compound agains cance cells. This pa ame e also allows o
a compa ison o he selec i i y o he in es iga ed compound wi h he selec i i y o he
s anda d an icance d ug. Fo compa ison, he cy o oxici y o wo clinical an icance d ugs,
ca bopla in and gemci abine, as well as imidazolium dica boxyla e p ecu so ligands (HL
R
,
1) was e alua ed unde iden ical expe imen al condi ions (see iabili y g aphs in Figu e 4
and Figu e S7). Complexes 2demons a ed cy o oxic ac i i y agains he h ee cance cell
lines, wi h IC
50
alues anging om 75 o 312
µ
M (Table 1), while he HL
R
p ecu so ligands,
1, did no show cy o oxici y (IC
50
> 3000
µ
M, see Figu e S7). Two no ewo hy obse a ions
can be d awn om Table 1. Fi s , al hough complexes 2exhibi ed lowe selec i i y com-
pa ed o gemci abine, hey showed g ea e selec i i y han ca bopla in, a well-es ablished
clinical an icance d ug. Ca bopla in is used o he ea men o o a ian cance , lung
cance , bladde cance , and head and neck cance . Second, hese zinc-based complexes
we e mo e cy o oxic o cance cells han o non-malignan HaCaT cells, unde sco ing hei
po en ial he apeu ic selec i i y.
Table 1. IC
50
alues (
µ
M) and selec i i y indexes (SIs) o zinc complexes es ed agains human cell
lines a.
Complex
IC50 (Mean ±SEM; pValue s. HaCaT)
(Selec i i y Index, Mean ±SEM)
HaCaT
(Non-Malignan
Ke a inocy e)
A549
(Lung Adenoca cinoma) MeWo
(Melanoma) T24
(Bladde Cance )
2a 260.2 ±20.0 156.3 ±3.7; 0.0214
(1.7 ±0.2) 126.5 ±1.9; 0.0071
(2.1 ±0.2) 124.4 ±5.5; 0.0101
(2.1 ±0.2)
2b 185.0 ±33.7 131.8 ±11.2; 0.1048
(1.4 ±0.1) 108.7 ±2.2; 0.1139
(1.7 ±0.3) 108.5 ±3.9; 0.1183
(1.7 ±0.3)
2c 231.4 ±7.4 202.4 ±7.6; 0.0965
(1.1 ±0.1) 75.7 ±1.9; 0.0001
(3.1 ±0.0) 83.2 ±3.8; 0.0001
(2.8 ±0.1)
2d 328.9 ±77.8 283.3 ±59.7; 0.1027
(1.1 ±0.1) 227.7 ±66.4; 0.1403
(1.6 ±0.5) 238.9 ±74.5; 0.2019
(1.6 ±0.5)
2e 343.9 ±12.5 311.7 ±3.2; 0.1299
(1.1 ±0.1) 162.3 ±19.3; 0.0032
(2.2 ±0.3) 194.6 ±37.7; 0.0157
(1.9 ±0.3)
Ca bopla in 35.9 ±3.8 42.9 ±1.4; 0.2188
(0.8 ±0.1) 100.4 ±17.4; 0.0182
(0.4 ±0.0) 22.1 ±2.6; 0.0130
(1.7 ±0.2)
Gemci abine
(nM) 22.1 ±3.1 5.6 ±0.1; 0.0130
(4.0 ±0.5) 7.3 ±0.7; 0.0270
(3.3 ±0.8) 2.3 ±0.3; 0.0062
(9.3 ±0.4)
a
A e 72 h o ea men , cell iabili y was measu ed using he esazu in assay. IC
50
alues a e gi en as he mean
alue ob ained om a leas h ee independen expe imen s
±
s anda d e o o he mean (SEM) (see Sec ion 3 o
mo e de ails). The selec i i y index (SI) alues we e calcula ed as he a e age o he IC
50
alues in he HaCaT non-
cance ous cell line di ided by he IC
50
alue in he cance cell line ob ained in each independen expe imen . Fo
he calcula ion o he
µ
M concen a ion, he molecula weigh o he monome o he co esponding coo dina ion
polyme was used.
Fo lung adenoca cinoma (A549), 2a demons a ed mode a e ac i i y wi h some
selec i i y, while he emaining complexes showed limi ed e icacy. The IC
50
alues o
2a–2c a e compa able o hose epo ed o a elmisa an zinc de i a i e ha con ains only
O-dono ligands (IC
50
75
µ
M) [
33
]. In pa icula , o he zinc complexes wi h N- o S-dono
ligands show lowe IC
50
alues
≤
10
µ
M) [
7
], sugges ing a ligand-dependen e ec [
34
–
36
].
In he case o T24 bladde cance cells, complexes 2a–2c exhibi ed IC
50
alues be ween 83
and 124
µ
M (Table 1), wi h 2c showing he highes selec i i y (close o 3). These esul s a e
consis en wi h ela ed zinc complexes [
37
]. A pa icula ly s ong IC
50
o T24 cells was
In . J. Mol. Sci. 2025,26, 3202 7 o 13
p e iously epo ed o an oxoapo phine–zinc complex, al hough he ee ligand i sel also
showed signi ican cy o oxici y (IC
50
9.12
µ
M) [
38
]. In melanoma cells (MeWo), complexes
2a–2c achie ed he bes IC
50
alues (~75
µ
M o 2c, Table 1), bu no compa able s udies
we e iden i ied in he li e a u e in ol ing his melanoma sub ype [
6
,
7
]. Impo an ly, he
selec i i y o 2c agains his cance was high, su passing ca bopla in and app oaching
ha o gemci abine (see Figu e S8). In e es ingly, he iabili y o melanoma cells exposed
o 145
µ
M o 2c was educed o less han 3%, while he iabili y o non-malignan cells
emained high (~85%). On he con a y, e en a he highes concen a ions o gemci abine
es ed, he cell iabili y o melanoma cells did no d op below 35%, while he iabili y o
non-malignan cells dec eased o 13% (Figu e 4). The educed an icance ac i i y o he
2d–2e complexes, compa ed o 2a–2c, can be a ibu ed o he biden a e coo dina ion o he
amino acid ligand. Zinc elease h ough dissocia ion would be mo e hinde ed due o he
chela e e ec han obse ed in complexes 2a–2c, which ha e only monoden a e ligands.
P e ious s udies sugges ed ha cy o oxici y in zinc complexes, wi h a educ ion in le els
o he mu p53 p o ein, was associa ed wi h he elease o zinc ions by dissocia ion [
39
]. The
p esence o chela ing amino acid ligands in 2d–2e hinde s his dissocia ion, hus educing
i s e icacy. Ou esul s on he an icance ac i i y o hese compounds a e p elimina y and
equi e
in i o
s udies o con i m hei an icance e ec s and e eal po en ial oxici ies in
no mal cell ypes beyond ke a inocy es. None heless, he selec i i y indices obse ed in
ou panel o cell lines a e highe han hose o se e al commonly used an icance d ugs
(see Table S3), suppo ing he ele ance o ou in i o indings.
In .J.Mol.Sci.2025,26,xFORPEERREVIEW7o 14


In hecaseo T24bladde cance cells,complexes2a–2cexhibi edIC
50
 aluesbe ween83
and124μM(Table1),wi h2cshowing hehighes selec i i y(close o3).These esul s
a econsis en wi h ela edzinccomplexes[37].Apa icula lys ongIC
50
 o T24cellswas
p e iously epo ed o anoxoapo phine–zinccomplex,al hough he eeligandi sel 
alsoshowedsigni ican cy o oxici y(IC
50
9.12μM)[38].Inmelanomacells(MeWo),com‐
plexes2a–2cachie ed hebes IC
50
 alues(~75μM o 2c,Table1),bu nocompa able
s udieswe eiden i iedin heli e a u ein ol ing hismelanomasub ype[6,7].Im‐
po an ly, heselec i i yo 2cagains  hiscance washigh,su passingca bopla inand
app oaching ha o gemci abine(seeFigu eS8).In e es ingly, he iabili yo melanoma
cellsexposed o145μMo 2cwas educed oless han3%,while he iabili yo non‐
malignan cells emainedhigh(~85%).On hecon a y,e ena  hehighes concen a ions
o gemci abine es ed, hecell iabili yo melanomacellsdidno d opbelow35%,while
he iabili yo non‐malignan cellsdec eased o13%(Figu e4).The educedan icance 
ac i i yo  he2d–2ecomplexes,compa ed o2a–2c,canbea ibu ed o hebiden a e
coo dina iono  heaminoacidligand.Zinc elease h oughdissocia ionwouldbemo e
hinde eddue o hechela ee ec  hanobse edincomplexes2a–2c,whichha eonly
monoden a eligands.P e iouss udiessugges ed ha cy o oxici yinzinccomplexes,
wi ha educ ioninle elso  hemu p53p o ein,wasassocia edwi h he eleaseo zinc
ionsbydissocia ion[39].Thep esenceo chela ingaminoacidligandsin2d–2ehinde s
hisdissocia ion, hus educingi se icacy.Ou  esul son hean icance ac i i yo  hese
compoundsa ep elimina yand equi ein i os udies ocon i m hei an icance e ec s
and e ealpo en ial oxici iesinno malcell ypesbeyondke a inocy es.None heless, he
selec i i yindicesobse edinou panelo celllinesa ehighe  han hoseo se e alcom‐
monlyusedan icance d ugs(seeTableS3),suppo ing he ele anceo ou in i o ind‐
ings.

Figu e 4. E ec o complexes 2, ca bopla in and gemci abine, on he iabili y o human non-malignan
cells (HaCaT) and human cance cells (A549, MeWo, and T24). The cells we e exposed o eagen s o
72 h, and cell iabili y was measu ed using he esazu in assay. Da a ep esen mean
±
SEM om a
leas h ee independen expe imen s. Fo s a is ical analysis, he - es (pai ed, wo- ailed) was used.
*p< 0.05, ** p< 0.01, and *** p<0.001 (simila ep esen a ions o ma ks + o #).
In . J. Mol. Sci. 2025,26, 3202 8 o 13
3. Ma e ials and Me hods
3.1. Gene al
All syn he ic p epa a ions and o he ope a ions we e ca ied ou unde ae obic con-
di ions. Sol en s we e pu i ied and d ied app op ia ely p io o use, using s anda d
p ocedu es. Cell cul u e eagen s we e pu chased om Biowes (Nuaillé, F ance). Re-
sazu in was pu chased om Sigma, gemci abine was ob ained om P ize , and ca bopla in
was ob ained om Te a. O he chemicals we e ob ained om comme cial sou ces and used
as supplied. In a ed spec a we e eco ded on a Pe kinElme FT-IR Spec um Two spec-
opho ome e (Wal ham, MA, USA) using he ATR echnique. NMR spec a we e eco ded
on B uke AMX-300 o A ance III spec ome e s (Bille ica, MA, USA) a he Cen o de
In es igaciones, Tecnología e Inno ación (CITIUS) o he Uni e si y o Se illa, wi h
1
H and
13
C{
1
H} NMR shi s e e enced o esidual signals om deu e a ed sol en s. All da a a e
epo ed in ppm down ield om Si(CH
3
)
4
. Elemen al analyses (C, H, N) we e conduc ed
by he CITIUS o he Uni e si y o Se illa on an Elemen al LECO CHNS 93 analyze (LECO
Co po a ion, S . Joseph, MI, USA). Bis-imidazolium p ecu so s we e p epa ed acco ding
o he li e a u e expe imen al me hods [
28
,
29
,
40
]. Complex 2a was p epa ed wi h sligh
di e ences om he p ocedu e epo ed [30].
3.2. Syn hesis
3.2.1. Complexes [Zn(LR)2]n,2a and 2b
A solu ion o Zn(AcO)
2·
2H
2
O (0.110 g, 0.5 mmol) in 10 mL o e hanol was added
o HL
Gly
(0.184 g, 1 mmol) dissol ed in he smalles amoun o a 3:1 e hanol–wa e
mix u e. The esul ing solu ion was s i ed o 1 h a 70
◦
C. The sol en was hen e-
mo ed unde educed p essu e and an oil was ob ained, which was ec ys allized in a 1:1
dime hyl o mamide–wa e mix u e. The compound [Zn(L
Gly
)
2
]
n
,2a, was ob ained as an
o -whi e solid (0.59 g, 47 %). IR (ATR, cm−1): 3140 (w), 3081 (w), 3003 (w), 2876 (w), 2168
(w), 1652 ( s,
νas
COO), 1562 (s), 1433 (m), 1416 (m), 1379 ( s), 1362 ( s), 1350 ( s,
νs
COO),
1323 (m), 1290 ( s), 1207 (w), 1188 (m), 1167 (s), 1109 (m), 1035 (m), 976 (w), 870 (m), 802
(s), 674 ( s), 636 (s), 585 ( s), 496 (s), 442 (m), 431 (m).
1
H NMR (300 MHz, D
2
O): 8.68 (b ,
2H, CH
im
), 7.38 (d,
3
J
HH
= 2 Hz, 4H, CH
im
), 4.77 (s, 8H, CH
2
COO).
13
C{
1
H} NMR (D
2
O,
75 MHz): 172.3 (COO), 137.2 (N-CH
im
-N), 123.2 (CH
im
), 51.9 (CH
2
COO). Elemen al Anal.
Calc. o C
17
H
21
N
5
O
9
Zn (2a + DMF): C, 40.45; H, 4.19; N, 13.87. Found: C, 39.68; H, 3.48;
N, 13.52%.
Complex [Zn(L
βAla
)
2
]
n
,2b, was p epa ed ollowing he same me hod, using HL
βAla
(212 mg, 1 mmol) and Zn(AcO)
2·
2H
2
O (110 mg, 0.5 mmol); 2b was ob ained as a pale whi e
solid (0.096 g, 39 %). IR (ATR, cm
−1
): 3383 (m), 3142 (m), 3108 (m), 3007 (w), 2965 (w), 1604
( s,
νas
COO), 1569 ( s), 1559 ( s), 1450 (m), 1395 ( s), 1372 ( s,
νs
COO), 1325 (s), 1300 (s),
1244 (m), 1229 (m), 1182 (s), 1150 ( s), 1100 (m), 1066 (m), 1023 (w), 988 (w), 943 (m), 864
(m), 825 (m), 775 (m), 755 (m), 650 (s), 634 (s), 604 (s), 559 (m), 532 (m), 519 (m), 434 (w), 418
(w).
1
H NMR (300 MHz, D
2
O): 8.70 (b , 2H, CH
im
), 7.44 (d,
3
J
HH
= 2 Hz, 4H, CH
im
), 4.36
( ,
3
J
HH
= 7 Hz, 8H, CH
2
CH
2
COO), 2.72 ( ,
3
J
HH
= 7 Hz, 8H, CH
2
CH
2
COO).
13
C{
1
H} NMR
(D
2
O, 75 MHz): 178.1 (COO), 136.0 (N-CH
im
-N), 122.2 (CH
im
), 46.7 (CH
2
CH
2
COO), 37.1
(CH
2
CH
2
COO). Elemen al Anal. Calc. o C
18
H
22
N
4
O
8
Zn (2b): C, 44.32; H, 4.55; N, 11.49.
Found: C, 44.17; H, 4.65; N, 11.31%.
3.2.2. Complex [Zn(LLeu)2(H2O)2]n,2c
The expe imen al me hod was simila o 2a,b, using HL
Leu
(296 mg, 1 mmol) and
Zn(AcO)
2·
2H
2
O (109 mg, 0.5 mmol). F om c ys alliza ion in a DMF:H
2
O 1:1 mix u e 2c
was ob ained as a pale whi e solid wi h he o mula [Zn(L
Leu
)
2
(H
2
O)
2
]
n
(0.165 g, 47 %). IR
(ATR, cm
−1
): 3143 (w), 2956 (m), 2871 (w), 1621 ( s,
νas
COO), 1467 (w), 1435 (w), 1372 ( s,
In . J. Mol. Sci. 2025,26, 3202 9 o 13
νs
COO), 1284 (w), 1234 (w), 1156 (m), 900 (w), 827 (w), 738 (w), 698 (m), 651 (m), 618 (w),
501 (ws), 418 (w).
1
H NMR (300 MHz, D
2
O): 8.93 (b , 1H, CH
im
), 7.50 (d,
3
J
HH
= 1.3 Hz,
2H, CH
im
), 4.86 (dd,
3
J
HH
= 10.2, 5.5 Hz, 2H, CHCOO), 1.95 (m, 4H, (CH
3
)
2
CHCH
2
), 1.24
(hp,
3
J
HH
= 6.6 Hz, 2H, (CH
3
)
2
CHCH
2
), 0.82 (d,
3
J
HH
= 6.6 Hz, 3H, (CH
3
)
2
CHCH
2
), 0.81 (d,
3
J
HH
= 6.6 Hz, 3H, (CH
3
)
2
CHCH
2
CH).
13
C{
1
H} NMR (D
2
O, 75 MHz): 174.9 (COO), 135.4
(N-CH
im
-N), 121.7 (CH
im
), 63.57 (CHCOO), 40.67 ((CH
3
)
2
CHCH
2
), 24.5 ((CH
3
)
2
CHCH
2
),
21.99 ((CH
3
)
2
CHCH
2
), 20.29 ((CH
3
)
2
CHCH
2
). Elemen al Anal. Calc. o C
30
H
50
N
4
O
10
Zn
(2c): C, 52.06; H, 7.28; N, 8.10. Found: C, 54.94; H, 7.29; N, 8.05%.
3.2.3. Complexes [Zn(LR)(aa)(H2O)]n,2d and 2e
[Zn(LVal)(Val)(H2O)]n,2d.
Following he same me hod as in 2a, using he p ecu so HL
Val
(134 mg, 0.5 mmol)
and Zn(AcO)
2·
2H
2
O (110 mg, 0.5 mmol) in he p esence o L- aline (58 mg, 0.5 mmol).
Complex 2d was ob ained as a pale whi e solid a e c ys alliza ion om a DMF:H
2
O 3:1
mix u e. Yield: 0.135 g (56%). IR (ATR, cm
−1
): 3296 (w), 3260 (w), 3138 (w), 2970 (w),
2873 (w), 1607 ( s,
νas
COO), 1586 ( s), 1466 (m), 1414 (m), 1375 ( s,
νs
COO), 1330 (m),
1306 (m), 1263 (w), 1236 (m), 1181 (w), 1156 (m), 1121 (w), 1095 (m), 1064 (m), 1015 (w),
987 (w), 950 (w), 916 (w), 863 (w), 847 (w), 816 (w), 789 (w), 773 (m), 749 (s), 730 (m), 703
(s), 665 (m), 635 (s), 614 (s), 585 (m), 543 (w), 502 (m), 453 (w), 423 (w), 409 (w).
1
H NMR
(
300 MHz
, D
2
O): 8.90 ( , 1H,
3
J
HH
= 1.8 Hz, CH
im
), 7.52 (d,
3
J
HH
= 1.8 Hz, 2H, CH
im
), 4.53
(d,
3JHH = 8.1 Hz
, 2H, NCHCOO), 3.40 (b d, 1H,
3
J
HH
= 3 Hz, NCHCOO Val), 2.39 (hp,
2H,
3
J
HH
= 6.9 Hz, CH(CH
3
)
2
), 2.26 (m, 1H, CH(CH
3
)
2
Val), 0.96–0.90 (m, 9H, CH(CH
3
)
2
),
0.84–0.79
(m, 9H, CH(CH
3
)
2
).
13
C{
1
H} NMR (D
2
O, 75 MHz): 173.8 (COO), 135.7 (N-CH
im
-
N), 122.0 (CH
im
), 71.5 (NCHCOO), 59.5 (NCHCOO Val), 31.1 (CH(CH
3
)), 29.5 (CH(CH
3
)
Val), 18.6 (CH(CH
3
)), 18.4 (CH(CH
3
) Val), 17.5 (CH(CH
3
)), 15.8 (CH(CH
3
) Val). Elemen al
Anal. Calc. o C
18
H
31
N
3
O
7
Zn (2d): C, 46.31; H, 6.69; N, 9.00. Found: C, 46.70; H, 6.53; N,
8.81%.
[Zn(LIle)(Ile)(H2O)]n,2e.
Following he same me hod as in 2a, using he HL
Ile
p ecu so (149 mg, 0.5 mmol)
and Zn(AcO)
2·
2H
2
O (110 mg, 0.5 mmol) in he p esence o L-isoleucine (66 mg, 0.5 mmol).
Complex 2e was ob ained as a pale whi e solid a e c ys alliza ion om a DMF:H
2
O
3:1 mix u e. Yield: 0.11 g (42%). IR (ATR, cm
−1
): 3136 (w), 2968 (m), 2933 (w), 2881
(w), 1631 ( s,
νas
COO), 1615 ( s), 1584 ( s), 1512 (s), 1460 (m), 1421 (w), 1363 ( s,
νs
COO), 1329 (s), 1307 (m), 1256 (m), 1234 (w), 1155 (m), 1099 (w), 1062 (w), 1026 (w), 961
(w), 919 (w), 870 (w), 840 (w), 746 (s), 709 (m), 649 (m), 615 (m), 559 (s), 537 (s), 455 (s).
1
H NMR (300 MHz, D
2
O): 8.89 ( ,
3
J
HH
= 2 Hz, 1H, CH
im
), 7.51 (d,
3
J
HH
= 2 Hz, 2H,
CH
im
), 4.56 (d,
3
J
HH
= 8.1 Hz, 2H, NCHCOO), 3.42 (b , 1H, NCHCOO Ile), 2.17 (m, 2H,
CH
3
CHCH
2
CH
3
), 1.95 (m, 1H, CH
3
CHCH
2
CH
3
Ile), 1.25–1.11 (m, 6H, CH
3
CHCH
2
CH
3
),
0.97-0.88 (m, 9H, CH
3
CHCH
2
CH
3
), 0.82-0.76 (m, 9H, CH
3
CHCH
2
CH
3
).
13
C{
1
H}-NMR
(D
2
O, 75 MHz): 173.9 (COO), 135.6 (N-CH
im
-N), 122.0 (CH
im
), 70.5 (NCHCOO), 59.1
(NCHCOO Ile), 36.9 (CH
3
CHCH
2
CH
3
), 36.5 (CH
3
CHCH
2
CH
3
Ile), 24.6 (CH
3
CHCH
2
CH
3
),
23.8 (CH
3
CHCH
2
CH
3
Ile), 15.2 (CH
3
CHCH
2
CH
3
Ile), 15.1 (CH
3
CHCH
2
CH
3
), 11.2
(CH
3
CHCH
2
CH
3
Ile), 10.3 (CH
3
CHCH
2
CH
3
). Elemen al Anal. Calc. o C
21
H
34
N
3
O
7
Zn
(2e): C, 49.86; H, 6.77; N, 8.31. Found: C, 51.23; H, 7.50; N, 8.46%.
3.3. Cell Lines and Cell Viabili y Assays
HaCaT cells (human ke a inocy es) [
24
] A549 (human lung adenoca cinoma), MeWo
(human melanoma), and T24 (human u ina y bladde ca cinoma) we e pu chased om
Cell Lines Se ice (CLS). The cells we e main ained in Dulbecco’s Modi ied Eagle Medium