1-(4-Carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid – A versatile ligand for the preparation of coordination polymers and mononuclear complexes

Article abstract of DOI:10.1016/j.poly.2021.115115

The straightforward and facile synthetic approaches towards four coordination polymers, {[CdL(H₂O)]·0.5H₂O}_n, {[Cd₂L₂(H₂O)₂(4,4′-bipy)]·4H₂O}_n, {[Cd₂L₂(H₂O)₂(4,4′-azpy)]·3H₂O}_n and {[CoL(H₂O)₃]·2.5H₂O}_n (4,4′-bipy = 4,4′-bipyridine; 4,4′-azpy = 4,4′-azopyridine), based on the polydentate ligand 1-(4-carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid (LH₂) and Cd(II) and Co(II) ions are reported. In addition, two mononuclear complexes, [Cu(HL)₂(DMA)] and [Cu(HL)₂(H₂O)₂], derived from the same ligand and the Cu(II) ion have been prepared. The coordination compounds have been characterized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis. Single crystal X-ray structures for each of these coordination compounds have been established. The specific surface of the 3D Cd(II)- and Co(II)-derived coordination polymers, determined through nitrogen adsorption, is negligible (S_BET < 25 m²/g).

Full text of DOI:10.1016/j.poly.2021.115115

Polyhedron 200 (2021) 115115
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Polyhedron
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1-(4-Carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid – A
versatile ligand for the preparation of coordination polymers and
mononuclear complexes
Bogdan-Ionel Bratanovici a,b, Sergiu Shova c, Vasile Lozan a,d, Ioan-Andrei Dasca˘lu a, Rodinel Ardeleanu c,
Gheorghe Roman c,
⇑
a
˘
Centre of Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry, 41A Aleea Gr. Ghica Voda, Iaßsi 700487, Romania
b Faculty of Chemistry, Al. I. Cuza University, 11 Carol I Blvd., Iaßsi 700506, Romania
c Department of Inorganic Polymers, Petru Poni Institute of Macromolecular Chemistry, 41A Aleea Gr. Ghica Voda˘, Iaßsi 700487, Romania
d Institute of Chemistry of MECR, 3 Academiei Str., MD2028 Chißsina˘u, Republic of Moldova
a r t i c l e i n f o
a b s t r a c t
Article history:
The straightforward and facile synthetic approaches towards four coordination polymers, {[CdL(H2O)]ꢀ
0.5H2O}n, {[Cd2L2(H2O)2(4,40-bipy)]ꢀ4H2O}n, {[Cd2L2(H2O)2(4,40-azpy)]ꢀ3H2O}n and {[CoL(H2O)3]ꢀ
2.5H2O}n (4,40-bipy = 4,40-bipyridine; 4,40-azpy = 4,40-azopyridine), based on the polydentate ligand 1-
(4-carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid (LH2) and Cd(II) and Co(II) ions are
reported. In addition, two mononuclear complexes, [Cu(HL)2(DMA)] and [Cu(HL)2(H2O)2], derived from
the same ligand and the Cu(II) ion have been prepared. The coordination compounds have been charac-
terized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis.
Single crystal X-ray structures for each of these coordination compounds have been established. The
specific surface of the 3D Cd(II)- and Co(II)-derived coordination polymers, determined through nitrogen
adsorption, is negligible (SBET < 25 m2/g).
Received 15 January 2021
Accepted 8 February 2021
Available online 23 February 2021
Keywords:
Coordination polymer
Dicarboxylate ligand
1,2,3-Triazole
X-ray crystal structure
Nitrogen adsorption
Ó 2021 Elsevier Ltd. All rights reserved.
1. Introduction
boxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid and
incorporating either common transition metal ions [9] or lan-
Owing to the interesting properties, considerable potential and
practical applications of coordination polymers, significant effort
has been devoted by many research groups to the preparation of
novel metal–ligand coordination entities in recent years. The com-
bination of structurally different ligands with various metal ions
can theoretically lead to a virtually infinite number of coordination
polymers. Within this vast category of coordination polymers,
coordination polymers generically known as metal–organic frame-
thanides [10,11] have been shown to be luminescent and exhibit
sensing properties towards xanthine, colchicine, simple phenols,
bicromate and metal ions. As an extension of these investigations,
the present study explores the versatility of the same rigid, tria-
zole-based dicarboxylate ligand in the generation of new coordina-
tion polymers and complexes, whose structure and properties
were subsequently examined.
works (MOFs) have gradually become
a privileged subclass
2. Experimental
because of their frequent porosity, which makes these materials
valuable for the storage of gases [1,2], gas separation and purifica-
tion [3,4], or catalysis [5,6]. In addition, MOFs have been designed
to incorporate fluorogenic chemical functionalities (either the
ligand, or the metal ion, or both) with the view to render them use-
ful for various sensing applications, i.e. the detection of biomole-
cules, environmental toxins, explosives, etc. [7,8]. Recently,
several coordination polymers derived from 1-(4-car-
2.1. Materials and methods
Methyl 4-aminobenzoate, NaNO2, NaN3, 36.5% aq. HCl, sodium,
NaOH, LiOH, Cd(NO3)2ꢀ4H2O, Co(NO3)2ꢀ6H2O and 4,40-bipyridine
(10) (4,40-bipy) were obtained from Alfa Aesar (Ward Hill, MA,
USA), while ethyl acetoacetate (2), 4,40-azopyridine (11) (4,40-azpy)
and Cu(NO3)2ꢀ3H2O were provided by Merck–Sigma–Aldrich
(Darmstadt, Germany). These chemical reagents were used
without further purification. The solvents (abs. ethanol, N.N-
dimethylformamide (DMF), N.N-dimethylacetamide (DMA),
⇑
Corresponding author.
E-mail address: gheorghe.roman@icmpp.ro (G. Roman).
https://doi.org/10.1016/j.poly.2021.115115
0277-5387/Ó 2021 Elsevier Ltd. All rights reserved.

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
dimethylsulfoxide (DMSO), methanol) were purchased from VWR
International (Radnor, PA, USA). The melting point was taken on
a MEL-TEMP capillary melting point apparatus and is uncorrected.
NMR spectra were recorded in DMSO d6 on a Bruker Avance III 400
instrument operating at 400.1 and 100.6 MHz for 1H and 13C nuclei,
respectively. Chemical shifts are reported in ppm relative to the
residual solvent peak (1H: 2.512 ppm, and 13C: 39.48 ppm). Fourier
Transform-Infrared (FT-IR) spectra were taken on a FT-IR Bruker
Vertex 70 spectrophotometer in the transmission mode using
KBr pellets. The intensity of the absorption bands is given as very
strong (vs), strong (s), medium (m), weak (w) and very weak
(vw). Elemental analysis was performed on a Vario EL III CHNS ana-
lyzer. Powder X-ray diffraction (PXRD) patterns were obtained on a
DMF (12 mL) contained in a 20 mL DuranTM glass vial with a
PTFE-coated PBT screw cap,
a
solution of Cd(NO3)2ꢀ4H2O
(370.2 mg, 1.2 mmol, 4 equiv.) in water (3 mL), followed by 65%
HNO3 (3 drops) were added. The vial was heated at 80 °C for
72 h and then allowed to slowly reach room temperature. The
resulting solid was filtered, washed sequentially with DMF
(2 ꢂ 5 mL) and methanol (3 ꢂ 10 mL), then air-dried to afford col-
orless block crystals that were suitable for single crystal X-ray
diffraction. Yield 106 mg (91.6% based on H2L). FT-IR (m
, cmꢁ1):
3585 m, 3279 m, 3159 m, 2928w, 1680 s, 1588vs, 1544vs,
1399vs, 1312 s, 1242 s, 1136 m, 1098 m, 1011 m, 866 s, 847 s,
787 s, 707 m, 673w, 543w, 458 m. Anal. Calcd. for C33H30Cd3N9O16.5
(%): C, 34.22; H, 2.59; N, 10.89. Found: C, 34.54; H, 2.37; N, 11.15.
Rigaku MiniFlex 600 diffractometer using monochromated CuKa-
´
radiation (k = 1.541874 Å) in the angular range 5–50° (2h) with a
scanning step of 0.01° and a recording rate of 1 deg minꢁ1, at room
temperature. Diffractograms were plotted using Match! software
from Crystal Impact (Bonn, Germany). Mercury software was used
to generate the simulated PXRD patterns. Thermogravimetric (TG)
measurements were performed with a STA 449F1 Jupiter instru-
ment. Sensitivity calibrations in the temperature range 30–
700 °C were carried out with indium. Approximately 20 mg of
the solid samples were weighed and placed in aluminum pans
and the TG experiments were run within a temperature range of
30 to 700 °C, with a heating rate of 5 °C/min, under an atmosphere
of dry nitrogen at a flow rate of 50 mL/min. The data was processed
with Netzsch Protens 4.2 software. Nitrogen adsorption experi-
ments were carried out with a Quantachrome NOVA 3200e surface
area and pore size analyzer. Prior to the N2 isotherm measure-
ments at 77 K, the samples were activated by solvent exchange
and degassed at 100 °C under high vacuum for 3 h. For the adsorp-
tion measurements, an amount in the range of 50–80 mg of the
samples was weighed before and after the degassing procedure
to confirm the removal of any retained solvent.
2.2.3. Synthesis of catena-poly[[(aqua-
bipyridine-
N)-m3-(1-(4-carboxylatophenyl-j2O,O0)-5-methyl-1H-
1,2,3-triazole-
j
O)cadmium(II)-hemi-m-(4,4-
j
j
N3-(4-m-carboxylato-j3O,O:O0)(2-))] dihydrate]
{[Cd2L2(H2O)2(4,40-bipy)]ꢀ4H2O}n (5)
The ligand H2L 3 (37.1 mg, 0.15 mmol, 1 equiv.) was dissolved
in DMF (6 mL) in a 20 mL DuranTM glass vial with a PTFE-coated
PBT screw cap. Separately, 4,40-bipyridine (10) (11.7 mg,
0.075 mmol, 0.5 equiv.) was dissolved in 96% ethanol (2 mL) and
Cd(NO3)2ꢀ4H2O (185.1 mg, 0.6 mmol, 4 equiv.) was dissolved in
water (4 mL). The solution of the neutral ligand was layered over
the solution of the dicarboxylic ligand, followed by the solution
of the Cd(II) salt. The vial was heated at 80 °C for 72 h and then
allowed to slowly reach room temperature. The resulting solid
was filtered, washed sequentially with DMF (2 ꢂ 5 mL) and metha-
nol (3 ꢂ 10 mL), then air-dried to yield colorless acicular crystals.
Yield 59 mg (80.3% based on H2L). FT-IR (m
, cmꢁ1): 3413 s,
3099w, 2927w, 1605vs, 1562vs, 1448 s, 1381vs, 1308 m, 1283 m,
1230w, 1134w, 1065w, 1009 m, 876 m, 844 m, 789 s, 708 m,
631 m, 546 m, 510 m, 456 m. Anal. Calcd. for C16H17CdN4O7 (%):
C, 39.20; H, 3.47; N, 11.43. Found: C, 39.51; H, 3.72; N, 11.74.
´
2.2. Synthesis
2.2.4. Synthesis of catena-poly[[(aqua-
azopyridine-
1,2,3-triazole-
j
O)cadmium(II)-hemi-m-(4,4-
j
N)-m3-(1-(4-carboxylatophenyl-j2O,O0)-5-methyl-1H-
j
2.2.1. Synthesis of 1-(4-carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-
carboxylic acid (H2L) (3)
N3-(4-m-carboxylato-j3O,O:O0)(2-))] sesquihydrate]
{[Cd2L2(H2O)2(4,40-azpy)]ꢀ3H2O}n (6)
To a solution of sodium ethoxide (freshly prepared from sodium
(460 mg, 20 mmol) and 50 mL of abs. ethanol), ethyl acetoacetate
(2)(2.6g,20mmol)wasadded,followedbyasolutionofmethyl4-azi-
dobenzoate (1) [12] (3.54 g, 20 mmol) in abs. ethanol (25 mL). The
mixture was heated at reflux temperature for 2 h, then allowed to
reach room temperature. The solid was filtered, washed with abs.
ethanol (2 ꢂ 25 mL) and air-dried at room temperature. The material
was then added to 0.2 M NaOH (200 mL) and the solution was heated
atrefluxtemperaturefor5h.Afterthecoldreactionmixturehadbeen
filtered, thesolutionwasbroughttopH5–6bythedropwiseaddition
of acetic acid under efficient stirring. The resulting solid was filtered,
washed thoroughly with distilled water and air-dried at room tem-
perature to afford the title compound as colorless microcrystals
1-(4-Carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic
acid (3) (37.1 mg, 0.15 mmol, 1 equiv.) was dissolved in DMF
(6 mL) in a 20 mL DuranTM glass vial with a PTFE-coated PBT screw
cap. Separately, 4,40-azopyridine (11) (27.6 mg, 0.15 mmol, 1
equiv.) was dissolved in DMF (2 mL) and Cd(NO3)2ꢀ4H2O
(185.1 mg, 0.6 mmol, 4 equiv.) was dissolved in water (4 mL).
The solution of the neutral ligand was layered over the solution
of the dicarboxylic ligand, followed by the solution of the Cd(II)
salt. The vial was heated at 80 °C for 72 h, and then allowed to
slowly reach room temperature. The resulting solid was filtered,
washed sequentially with DMF (2
(3 ꢂ 10 mL), then air-dried to afford dark orange crystals. Yield
64 mg (86.3% based on H2L). FT-IR (
, cmꢁ1): 3369 m, 3065w,
ꢂ
5 mL) and methanol
m
(3.4 g, 69%); Mp: 229–230 °C (dec.). FT-IR (
m
, cmꢁ1): 3411 m,
2929vw, 1665 m, 1606vs, 1562vs, 1444 s, 1383vs, 1305 m,
1282 m, 1011 m, 873 m, 856 m, 840 s, 788 m, 705 m, 579 m,
546 m. Anal. Calcd. for C16H15.95CdN5O6.4 (%): C, 38.84; H, 3.22; N,
14.16. Found: C, 39.09; H, 2.98; N, 14.27.
2868w, 2640w, 2530w, 1694vs, 1608 m, 1593w, 1516w, 1473 m,
1447w, 1313w, 1287 s, 1234w, 1121 m, 989 m, 864w, 806 m,
776 m. 1H NMR (400.1 MHz, DMSO d6) d, ppm: 2.51 (s, 3H), 7.80 (d,
J = 8.4 Hz, 2H), 8.18 (d, J = 8.4 Hz, 2H), 13.30 (br s, 2H). 13C NMR
(100.6 MHz, DMSO d6) d, ppm: 9.8, 125.4, 130.6, 132.0, 136.8, 138.6,
139.2, 162.5, 166.3. Anal. Calcd. for C11H9N3O4 (%): C, 53.44; H, 3.67;
N, 17.00. Found: C, 53.72; H, 3.49; N, 16.73.
2.2.5. Synthesis of [dimethylacetamido-
5-methyl-1H-1,2,3-triazole-(4-carboxylato-
j
O-bis(1-(4-carboxyphenyl)-
j
2N3,O)(1-))copper(II)]
[Cu(HL)2(DMA)] (7)
Separately, the ligand H2L 3 (37.1 mg, 0.15 mmol, 1 equiv.) was
dissolved in DMA (4 mL), and Cu(NO3)2ꢀ3H2O (145 mg, 0.6 mmol, 4
equiv.) was also dissolved in DMA (2 mL). The clear mixture
obtained by combining the two solutions in a 10 mL glass vial with
a PTFE-coated PP screw cap was heated at 80 °C for 72 h and then
allowed to reach room temperature over several hours. The solid
2.2.2. Synthesis of catena-poly[[(aqua-
j
O)cadmium(II)-m3-((1-(4-
carboxylatophenyl-j2O,O0)-5-methyl-1H-1,2,3-triazole-
j
N3-(4-m-
carboxylato-j3O,O:O0)(2-))] hemihydrate] {[CdL(H2O)]ꢀ0.5H2O}n (4)
To a solution of 1-(4-carboxyphenyl)-5-methyl-1H-1,2,3-tria-
zole-4-carboxylic acid (H2L) (3) (74.2 mg, 0.3 mmol, 1 equiv.) in
2

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
that formed during the heating stage was filtered and sequentially
washed with DMA (2 ꢂ 5 mL) and methanol (3 ꢂ 10 mL), then air-
dried to afford blue crystals. Yield 21 mg (43.5% based on H2L). FT-
nation with imposed restrains on positional and displacement
parameters. The molecular plots were obtained using the Olex2
program. Crystallographic data are listed in Table 1, whilst bond
lengths and angles can be found in Table S1 in the Supplementary
Information (SI). CCDC: 2,024,571 (4), 2,024,577 (5), 2,024,578 (6),
2,024,579 (7) and 2,024,580 (8).
IR (m
, cmꢁ1): 3416w, 2936w, 2870w, 2771w, 2571w, 2435w,
1935w, 1712 s, 1628 s, 1597vs, 1509 m, 1422 s, 1378 s, 1322 m,
1269 s, 1251 s, 1170 m, 1116 m, 1041 m, 1015 s, 864 m, 828 s,
804 s, 776 s, 696 m, 684w, 601w, 511 m, 440 m. Anal. Calcd. for
C26H25CuN7O9 (%): C, 48.51; H, 3.88; N, 15.23. Found: C, 48.23; H,
3.59; N, 14.94.
3. Results and discussion
2.2.6. Synthesis of [di(aqua-
1H-1,2,3-triazole-(4-carboxylato-
(HL)2(H2O)2] (8)
j
O) bis(1-(4-carboxyphenyl)-5-methyl-
3.1. Synthesis and characterization of ligand 3, coordination polymers
4–6 and 9, and complexes 7 and 8
j
2N3,O)(1-))copper(II)] [Cu
(1-(4-Carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic
acid (3) (37.1 mg, 0.15 mmol, 1 equiv.) was dissolved in DMSO
(6 mL) in a 20 mL DuranTM glass vial with a PTFE-coated PBT screw
cap. Separately, Cu(NO3)2ꢀ3H2O (145 mg, 0.6 mmol, 4 equiv.) was
dissolved in water (4 mL). The clear mixture produced by combin-
ing these two solutions was heated at 80 °C for 72 h, and then
allowed to slowly reach room temperature. The material that sep-
arated was filtered and sequentially washed with DMSO (2 ꢂ 5 mL)
and methanol (3 ꢂ 10 mL), then air-dried to afford light blue crys-
Ligand 3 has been obtained previously through a base-catalyzed
triazole ring closure reaction that employed 4-azidobenzoic acid as
the azide reagent [9,10]. Ligand 3 was prepared through a similar
Dimroth cyclization in the present study, only this synthetic vari-
ant employed methyl 4-azidobenzoate (1) as the azide reagent
instead of 4-azidobenzoic acid (Scheme 1). Methyl 4-azidoben-
zoate (1) required for this synthetic variant was prepared from
methyl 4-aminobenzoate according to a reported procedure [12].
The crude product isolated from the Dimroth ring closure was a
mixture of esters that consisted primarily of ethyl 1-(4-(ethoxycar-
bonyl)phenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylate (resulted
via transesterification of the normal reaction product) and ethyl
1-(4-(methoxycarbonyl)phenyl)-5-methyl-1H-1,2,3-triazole-4-
carboxylate (the normal reaction product) as a minor component,
according to NMR spectra. The mixture of esters was subsequently
hydrolyzed under basic conditions to afford the ligand with mod-
erate yield and excellent purity.
The structure of the key ligand 3 has been confirmed by NMR
spectroscopy. The 1H NMR spectrum of this compound (Fig. S1 in
the SI) shows a sharp singlet at d 2.56 ppm corresponding to the
protons of the methyl group, two doublets appearing as an AA0BB0
spin system in the aromatic region of the spectrum, which are
associated with the protons of the phenyl ring, and a broad off-
set signal integrating for two protons, which are attributed to the
protons of the carboxyl groups. The aliphatic region of the carbon
spectrum of ligand 3 (Fig. S2 in the SI) features the peak associated
with the carbon atom of the methyl group at d 9.77 ppm, whereas
the two signals d 166.32 and 162.47 ppm are attributed to the car-
bon atoms of the two distinct carboxyl groups. In addition, the cor-
rect number of six aromatic carbon atoms, belonging to the
benzene and triazole rings, has also been identified in the carbon
spectrum of compound 3.
tals. Yield 23 mg (51.8% based on H2L). FT-IR (m
, cmꢁ1): 3512 s,
3445 m, 2944w, 2871w, 2785w, 2614w, 2487w, 1702 s, 1661vs,
1595 s, 1419 s, 1377vs, 1311 s, 1246vs, 1139 m, 1122 s, 1015 m,
858 m, 801 m, 774 s, 695 m, 685 m, 531 m, 494 m, 442 m. Anal.
Calcd. for C22H20CuN6O10 (%): C, 44.59; H, 3.37; N, 14.18. Found:
C, 44.82; H, 3.66; N, 13.91.
2.2.7. Synthesis of catena-poly[[tri(aqua-
jO)cobalt(II)-m3-((1-(4-
carboxylatophenyl-j2O,O)-5-methyl-1H-1,2,3-triazole-
j
N3-(4-m-
´
carboxylato-j3O,O:O)(2-))]-hydrate(5/2)]{[CoL(H2O)3]ꢀ2.5H2O}n (9)
Ligand 3 (37.1 mg, 0.15 mmol, 1 equiv.) was dissolved in a mix-
ture of water (6 mL) and aqueous 0.1 M LiOH (3 mL) in a 20 mL
DuranTM glass vial with a PTFE-coated PBT screw cap under effi-
cient stirring at 40–50 °C. Separately, Co(NO3)2ꢀ6H2O (174.6 mg,
0.6 mmol, 4 equiv.) was dissolved in water (6 mL). The aqueous
solution of the metal salt was added to the solution of the ligand,
and the mixture was warmed to 80 °C over 1 h. The mixture was
kept at 80 °C for 72 h, and then gradually cooled to room temper-
ature over 14 h. The solid was filtered, washed thoroughly with
water and air-dried to afford large red block crystals that were
suitable for single crystal X-ray diffraction. Yield 45 mg (74.4%
´
based on H2L). FT-IR (m
, cmꢁ1): 3400 s, 3187 m, 2926w, 1615vs,
1553 s, 1425 s, 1400vs, 1381 s, 1310 s, 1244 m, 1137 m, 1016 m,
781 m. Anal. Calcd. for C11H18CoN3O9.5 (%): C, 32.73; H, 4.46; N,
10.41. Found: C, 32.39; H, 4.69; N, 10.11.
In order to obtain coordination polymers from this ligand that
have topologies that are distinct from the ones already reported,
numerous different experimental conditions have been tried for
the solvothermal synthesis of novel crystalline complexes derived
from ligand 3. This approach led to the isolation of crystals that
were appropriate for structure determination by single crystal X-
ray diffraction for a new cadmium-based coordination polymer
(4) when the reaction was performed in DMF in the presence of
HNO3 (Scheme 2).
2.3. X-ray crystallographic measurements
Intensity data for coordination polymer 4 were collected with
an Oxford Diffraction SuperNova diffractometer using hi-flux
micro-focus Mo K
a radiation and for compounds 5–9 on an
Oxford-Diffraction XCALIBUR E CCD device equipped with Mo K
a
radiation. The unit cell determination and data integration were
carried out using the CrysAlisPro package from Oxford Diffraction
[13]. Multi-scan absorption corrections for all the crystals were
applied. The structures were solved using the intrinsic phasing
methods of SHELXT [14] and refined by full-matrix least-squares
minimization on F2 with SHELXL [15] in the graphical interface of
Olex2 program [16]. Hydrogen atoms were placed at calculated
positions and refined in the riding model, except those attached
to oxygen atoms, which were located from Fourier maps and
refined accordingly to the intermolecular interactions. The posi-
tional parameters of disordered non-hydrogen atoms were refined
by applying combined anisotropic/isotropic refinement in combi-
In addition, nitrogen-containing neutral ligands, such as 4,40-
bipyridine (4,40-bipy) and 4,40-azopyridine (4,40-azpy), which are
able to function as pillars between the planes of a 2D coordination
polymer and presumably yield porous MOFs, have been employed
in the complexation experiments between ligand 3 and Cd(II) ions.
To the best of our knowledge, no coordination polymers derived
from ligand 3 and containing auxiliary ligands in their structure
have been reported until now. Again, several reaction conditions
were tried with the view to obtain crystalline coordination poly-
mers that could be structurally characterized by single crystal X-
ray diffraction. The use of 4,40-bipyridine (10) as an ancillary ligand
in the reaction between ligand 3 and Cd(II) ions led to crystals
3

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
Table 1
Crystal data and details of the data collection for compounds 4–8.
Compound
4
5
6
7
8
Empirical formula
Fw
C
33H30Cd3N9O16.5
C16H17CdN4O7
489.73
Pccn
20.932(2)
19.6383(19)
8.7394(12)
90
90
90
3592.5(7)
8
1.811
C16H15.95CdN5O6.4
494.29
Pccn
21.3152(8)
19.0391(8)
9.2720(4)
90
90
90
3762.8(3)
8
1.745
C26H25CuN7O9
643.07
Cm
8.0696(4)
22.9695(8)
7.7440(3)
90
112.074(5)
90
C22H20CuN6O10
591.98
P-1
1156.88
R3
20.9672(8)
20.9672(8)
8.5333(3)
90
90
120
3248.8(3)
3
1.774
space group
a [Å]
b [Å]
c [Å]
a[°]
6.8575(3)
7.2928(4)
12.9599(7)
103.954(5)
98.412(4)
104.290(4)
594.77(6)
1
b [°]
g [°]
V [Å3]
Z
1330.16(10)
2
1.606
rcalcd [g cmꢁ3
]
1.653
Crystal size [mm]
0.3 ꢂ 0.1 ꢂ 0.1
0.15 ꢂ 0.05 ꢂ 0.03
0.8 ꢂ 0.1 ꢂ 0.05
0.3 ꢂ 0.1 ꢂ 0.02
0.25 ꢂ 0.15 ꢂ 0.05
T [K]
293
293
180
180
180
m [mmꢁ1
]
1.538
1.265
1.208
0.891
0.990
2
H
range
7.62 to 49.988
4990
2532[Rint = 0.0236]
2532/70/208
0.0256
0.0549
1.067
0.26/-0.24
0.00(2)
4.148 to 50.054
11,191
2532[Rint = 0.1069]
3167/6/255
0.0598
0.0806
0.983
0.66/-0.65
–
4.278 to 50.054
8691
3321[Rint = 0.0240]
3321/0/272
0.0328
0.0747
1.066
0.89/-0.41
–
3.546 to 58.918
10,952
3229[Rint = 0.0327]
3229/2/207
0.0285
0.0544
1.045
0.58/-0.30
0.007(5)
3.318 to 50.052
5846
2108[Rint = 0.0381]
2108/0/180
0.0393
0.0771
1.072
0.33/-0.40
–
Reflections collected
Independent reflections
Data/restraints/parameters
R[1a]
wR[2b]
GOF[c]
Largest diff. peak/hole / e Åꢁ3
Flack parameter
aR1
= R||Fo| -|Fc||/R R R . R
|Fo|. bwR2 = { [w(F2o -Fc2)2]/ [w(Fo2)2]}1/2 cGOF = { [w(Fo2 -F2c)2]/(n -p)}1/2, where n is the number of reflections and p is the total number of parameters
refined.
Scheme 1. Synthesis of H2L 3 through the Dimroth cycloaddition.
Scheme 2. Synthesis of coordination compounds 4–9 from the ligand H2L (3).
under a few sets of reaction conditions, but the needle-like shape
of these crystals and their modest size, which was the consequence
of the massive separation of the crystalline solid in the initial hours
of the heating stage, precluded any definitive structure determina-
tion. Finally, the use of a ternary reaction solvent (DMF–water–
ethanol) afforded larger crystals, and coordination polymer 5 could
4

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
be isolated as crystals suitable for X-ray diffraction in 80% yield
(Scheme 2). When 4,40-azopyridine (11) was employed as an aux-
iliary ligand, coordination polymer 6 was obtained as large orange
crystals by employing a mixture of DMF and water as the solvent
(Scheme 2).
tion bands appearing between 1386 and 1136 cmꢁ1 in the IR
spectra of complexes 4–9 are indicative for the triazole ring.
Because of the partial overlap of the stretching vibrations for the
carboxylate groups and the characteristic stretching vibrations of
the triazole and phenyl rings (range of 1100–1680 cmꢁ1), the
absorption bands characteristic for DMA in complex 7 are difficult
to identify unequivocally. Absorption bands observed between 876
and 776 cmꢁ1 could be tentatively attributed to the bending vibra-
tion of a para-substituted benzene ring.
Until now, the only coordination compound based on ligand 3
and copper ions has been a polymer that was obtained under harsh
reaction conditions in low yields [9]. Therefore, several different
sets of solvothermal reaction conditions have been evaluated for
the synthesis of other copper-derived coordination polymers based
on ligand 3. By heating a mixture of the ligand and copper(II)
nitrate trihydrate in DMA at 80 °C for 72 h, blue crystals suitable
for X-ray diffraction separated gradually during the heating stage
(Scheme 2). Unfortunately, structural investigation by XRD showed
that the compound [Cu(HL)2DMA] (7) obtained under these exper-
imental conditions was a discrete mononuclear complex. Further-
more, when the same reaction was attempted in a mixture of
DMSO and water, another mononuclear complex, [Cu(HL)2(H2O)2]
(8), was isolated from the reaction mixture (Scheme 2). Use of aux-
iliary ligands such as 4,40-bipyridine (10), 4,40-azopyridine (11) or
1,2-di(4-pyridyl)ethylene in experiments aiming at preparing
coordination polymers from H2L and either copper(II) nitrate or
copper(II) acetate under various conditions did not produce mate-
rials whose structure could be properly established by single crys-
tal X-ray diffraction. Despite our efforts, the desired copper-
containing coordination polymers based on ligand 3 remained
elusive.
3.2. Crystal structures of the coordination polymers and complexes 4–
9
The X-ray diffraction study has demonstrated that compound 4
is a three-dimensional coordination polymer with the molecular
formula {[CdL(H2O)]ꢀ0.5H2O}n, which crystallizes as a pure enan-
tiomer in the Sohnke R3 space group of the trigonal system. As
shown in Fig. 1, the asymmetric part of the structure is formed
by one Cd atom, one double-deprotonated linker (L2ꢁ) and a frac-
tional number of water molecules distributed in disordered posi-
tions. The Cd atom is seven-coordinated by O6N, supplied by the
ligand L2ꢁ and one molecule of water. Its irregular coordination
polyhedron approaches a strongly distorted pentagonal bi-pyrami-
dal geometry. The double deprotonated L2ꢁ linker behaves as hex-
adentate ligand, being coordinated through both carboxylate
groups and a nitrogen atom in the triazole ring. One of the carboxy-
late group functions as a j2O,O0 bidentate-chelating group, while
Out of the several cobalt-containing solid materials that could
be isolated from the reaction of ligand 3 with cobalt(II) nitrate
under various experimental conditions, only the coordination net-
work {[Co(L)(H2O)3]ꢀ2ꢀ5H2O}n (9) separated out as large block crys-
tals that were suitable for characterization by single crystal X-ray
diffraction. A comparison between the crystallographic data for
coordination polymer 9 (available in the SI) and the data that has
been already reported in the literature [9] proved conclusively
the chemical and crystallographic identity of the two compounds.
Therefore, although the reaction conditions employed for the
preparation of compound 9 (using Co(NO3)2ꢀ6H2O as the source
of Co(II) ions, water as the solvent, in the presence of LiOH, at
80 °C for 2 days) are quite different from the ones previously
reported, the isolated crystals have the same structure as those
obtained from CoCl2ꢀ6H2O in a mixture of methanol–water at
100 °C for 2 days. Our synthetic approach provides a slightly higher
yield (74% based on H2L) than the one previously reported for the
same compound (29% based on Co, that is 58% based on H2L) [9].
The IR spectrum of ligand 3 (Fig. S3 in the SI) was examined and
the IR bands of complexes 4–9 (Fig. S4–S9 in the SI) have been
assigned relative to those identified for ligand 3. The IR spectrum
of the diacid 3 is similar to that given in a previous publication
[9] and shows the characteristic absorption bands for carboxylate
groups. Thus, the strong peak at 1694 cmꢁ1 has been attributed
the second one is coordinated in a l2-
j3O,O0:O tridentate-bridging
mode, and links two Cd atoms at a distance of 4.6650(5) Å. The
crystal packing results via the self-assembly of the asymmetric
entities, constituting a three-dimensional coordination polymer,
which exhibits parallel channels along the 001 direction (Fig. 2),
filled by co-crystallized water molecules with fractional occu-
pancy. The total solvent accessible volume after removing the
water molecules, calculated using the tool available in the Olex2
program, is 452.6 Å3 (13.9% of the unit cell volume).
The crystal structures of coordination polymers 5 and 6 are clo-
sely related, despite the presence of two different ancillary ligands
(4,40-bipyridyl in 5 and 4,40-azopyridine in 6). Both structures were
solved in the Pccn space group and had similar unit cell parameters
(see Table 1). A view of the asymmetric part for polymers 5 and 6
are shown in Fig. 3a and Fig. 3b, respectively. In both polymers, the
Cd atom exhibits an O4N2 coordination in a strongly distorted octa-
hedral environment. The sums of the deviations from 90° for all 12
cis bond angles for 5 and 6 are 81.8 and 79.41°, respectively. Unlike
its coordination mode in the network of 4, the L2ꢁ linker in 5 and 6
acts as a tridentate ligand, with a set of O3N donor atoms. Thus, the
two carboxylate groups have different coordination functions: one
carboxylate has a bridging bidentate form in a syn–anti arrange-
ment, while the second one is coordinated as a monodentate
group, the non-coordinated oxygen atom being involved as an
acceptor in hydrogen bonds with coordinated and solvate water
molecules as donors of protons (Fig. 3, a and b). As expected, the
crystal packings for these two compounds are also very similar,
and they feature a three-dimensional network with ~ 6 ꢂ 6 Å
one-dimensional rectangular channels, as shown in Fig. 4 (a and
b). The total volume of the empty channels calculated by Olex2
program represents ~ 12% relative to the total volume of the unit
cell.
to the
m
as(C@O) stretching vibration of the carboxylate groups, while
the band at 1473 cmꢁ1 was assigned to
ms(C@O) in the same groups.
The absorption bands corresponding to other bonds in the struc-
ture of the diacid 3 are detailed in Table 2.
In the IR spectra of complexes 4–9, the broad bands between
3584 and 3279 cmꢁ1 correspond to asymmetric and symmetric
OAH stretching vibrations of water molecules within the structure
of these complexes. Weak absorption bands observed immediately
below 3000 cmꢁ1 are characteristic for the
m
(CAH) vibration modes
According to the X-ray diffraction analysis, compound 7 has a
molecular crystal structure built up from the neutral mononu-
clear complex [Cu(HL)2(DMA)], which is shown in Fig. 5. No co-
crystallized solvent molecules have been found in the crystal.
The copper atom exhibits a slightly distorted O3N2 square-pyra-
midal coordination generated by two bidentate mono-deproto-
nated HLꢁ ligands in the equatorial plane and the DMA
of the methyl group. The strong absorption peaks at 1680–
1605 cmꢁ1 can be associated with asymmetric vibrations of the
carboxylate groups, while peaks at 1448–1399 cmꢁ1 can be
assigned to symmetric vibrations of the same groups [17]. The
bands in the range 1597–1509 cmꢁ1 are attributed to the charac-
teristic stretching vibrations of the phenyl rings. Various absorp-
5

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
Table 2
IR absorption bands (cmꢁ1) of ligand 3 and complexes 4–9.
3
4
5
6
7
8
9
m
(OAH)
3411
2868
1694
1473
1516
1313,1287,1234
864,806
3584,3279
2928
1680
3413
2927
1605
1448
1562
1308,1283,1230
876, 844
3369
2929
1606
1444
1562
1383,1305, 1282
856, 840
–
2936
1628
3512,3445
2944
1661
1419
1595, 1513
3400
2926
1615
1426
1553
m(–CH3)
m–a) s(COO
m–s)(COO
m(phenyl)
m(triazole)
m(Ar-H)
1399
1422
1588,1544
1312,1242,1136
847
1597,1509
1378,1322,1269
864, 828
1377,1311,1246
858,829
1381,1311, 1244
781
Fig. 1. View of the asymmetric part in the crystal structure of 4, along with labelling of the atoms. Thermal ellipsoids are shown at the 50% probability level. Only the major
component of the distorted fragment is shown. Co-crystallized water molecules are omitted for clarity. Symmetry generated fragments are shown with faded colors.
Fig. 2. Partial crystal structure packing of 4 viewed along the c axis. Co-crystallized water molecules located in the channels are drawn in the space filling mode.
6

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
Fig. 3. View of the asymmetric part in the crystal structures of 5 (a) and 6 (b), along with their atom labelling. Thermal ellipsoids are shown at the 50% probability level.
Symmetry generated fragments are shown with faded colors.
molecule in the apical position. The Cu atom is displaced from the
mean N2O2 basal plane by 0.184(2) Å towards oxygen atom O5.
The organic ligand HLꢁ behaves as a bidentate ligand that coordi-
nates through one nitrogen atom of the triazole ring and one
monodentate carboxylate group. Notably, the second carboxylic
group of the ligand is not coordinated to any metal atom. The
non-coordinated carboxylic moiety participates in the formation
of hydrogen bonds with one oxygen atom of the coordinated car-
boxylate that acts as acceptor of a proton. In turn, these hydrogen
bonds determine the formation of stripe-like 1D supramolecular
aggregates, as shown in Fig. 6.
The attempt to synthesise a copper coordination compound
based on the ligand H2L in a 1:1 DMSO–water reaction mixture
afforded compound 8 as another mononuclear complex. The crys-
tal structure of this compound consists of the neutral complex [Cu
(HL)2(H2O)2] (Fig. 7), in which the copper(II) atom occupies a spe-
cial position on the inversion center. When compared to complex
7, it is noteworthy that two bidentate HLꢁ ligands in compound
8 fulfill the same coordination function, but are coordinated in a
trans configuration. On the other hand, the copper atom adopts a
slightly distorted N2O4 octahedral polyhedron (see Table S1). The
analysis of the packing of the [Cu(HL)2(H2O)2] molecules revealed
7

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
Fig. 4. Partial crystal structure packing viewed along the c axis for 5 (a) and for 6 (b). Co-crystallized water molecules located in the channels are drawn in the space filling
mode.
that all the possibilities for hydrogen bond formation are com-
pletely realized in the crystal. Consequently, the crystal structure,
which is shown in Fig. 8, essentially results from the parallel pack-
ing of two-dimensional supramolecular networks.
The crystal structure of network 9 is identical to the one
reported previously for a coordination polymer of ligand 3 with
Co(II) ions that was obtained under different reaction conditions
[9]. The crystal data and details of the data collection for com-
pound 9 are presented in the SI.
3.3. Thermogravimetric, PXRD analysis and adsorption studies
In order to assess the robustness of the coordination architec-
ture of the compounds, thermogravimetric analysis was performed
on the crystalline materials. The curves recorded for the coordina-
tion polymers and complexes 4–9 can be found in the SI associated
with this article (Figs. S10–S15). For coordination polymer 4, the
results suggest that the initial weight loss of 7.98% which occurs
before 315 °C is associated with the complete release of water from
8

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
9.10%) from the structure of coordination polymer 6, can be
noticed in the corresponding thermogravimetric curve up to
202 °C. Next, removal of the auxiliary ligand (calcd. 18.61%) that
takes place in the temperature range 202–369 °C is most likely
to correspond at least in part to the experimental weight loss of
23.22%; the beginning of the thermal decomposition of the ligand
L2ꢁ, or even the elimination of cadmium as volatile derivatives,
might account for the difference of more than 4% between the
experimental and calculated values. The percentage for the residue
recovered at the end of the thermal decomposition of coordination
polymer 6 (21.95%) is noticeably higher than those recorded for
networks 4 or 5, but is still lower that the theoretical percentage
(25.97%, calcd. for CdO). Mononuclear complex 7 is very stable
up to 239 °C owing to the absence of any volatile solvent mole-
cules. Afterwards, a sudden weight loss of 41.28% in a very narrow
temperature range (239–269 °C) occurs, when the breaking of the
complex presumably takes place. For the mononuclear complex 8,
the thermogravimetric data shows a first stage of 5.24% weight loss
before 197 °C, owing to the elimination of two coordinated water
molecules (calcd. 6.08%). A second stage is observed in a narrow
temperature range (238 to 270 °C) and this stage can be ascribed
to the decomposition of the complex and the release of the ligand
from the material, in a manner similar to the one recorded for com-
plex 7 in the same temperature range. The results obtained from
the thermogravimetric analysis of coordination polymer 9 are sim-
ilar to those previously reported [9] for the same compound, i.e. a
weight loss of 24.82% before 290 °C, which is equivalent to the
release of three coordinated water molecules and 2.5 lattice water
molecules from the structure of this compound (calcd. 24.57%).
The experimental PXRD patterns of coordination polymers 4, 5,
6 and 9 (Fig. S16–S19 in SI) closely match the diffractograms that
were generated using the single crystal X-ray diffraction data,
which suggest that all five complexes are phase pure. In order to
ascertain the preservation of their structural integrity, a second
experimental PXRD pattern was recorded for these compounds
after their activation prior to determination of the specific surface
area. According to the results, Cd-based networks 4–6 appear to be
stable, and removal of their lattice water does not result in the col-
lapse of the network. However, removal of lattice water in coordi-
nation polymer 9 led to structural changes, as suggested by the
heavily modified PXRD pattern recorded for the sample after sol-
vent exchange. Moreover, the structural integrity of coordination
polymer 9 was definitely compromised during the thermal activa-
tion stage in the initial stage of the adsorption experiment, as
gleaned from the PXRD pattern appearing as a broad envelope of
peaks that was recorded for this particular sample at the end of
the adsorption experiment (data not shown).
Fig. 5. X-ray molecular structure of complex 7 with the atom labelling and thermal
ellipsoids at 50% probability.
the structure of the compound (one coordinated water molecule
and a half lattice water molecule, calcd. 7.00%). Interestingly, the
residue left at the end of the experiment (17.62%) does not account
for the amount of cadmium in the sample subjected to thermal
decomposition (calcd. 29.15%). As the metal in organic–inorganic
hybrid samples is usually converted into the corresponding metal
oxide under the experimental conditions of thermogravimetric
analysis, the difference between the experimental results and the-
oretical calculations in this case is even more striking; thus, the
calculated percentage of the residue is 33.30%, considering that
the residue is composed solely of cadmium oxide. A similar behav-
ior was observed for another Cd-derived coordination polymer
synthesized by our group [18]. Moreover, it was found that for sev-
eral Cd-based coordination polymers reported by different
research groups, the percentage of the solid residue resulting at
the end of thermogravimetric experiments was also lower than
the calculated content for cadmium in the respective compounds
[19–22]. Therefore, we hypothesize that, at least in these cases,
cadmium is partially removed as organic or inorganic derivatives
that are volatile at high temperatures. For coordination polymer
5, the complete removal of the water molecules (calcd. 11.02%)
in its structure corresponds to weight loss of 10.73% which is
observed at 277 °C as two gentle, continuous stages. A more signif-
icant weight loss (18.41%) has been recorded for temperatures
between 277 and 350 °C, and this loss could be tentatively
assigned to the elimination of the auxiliary ligand (calcd.
15.93%). For the higher temperatures in the 277–350 °C range,
the end of auxiliary ligand loss from polymer 5 is presumably laid
over the beginning of the decomposition of the organic linker L2ꢁ
.
Samples of coordination polymers 4, 5, 6 and 9 were activated
using the solvent exchange technique, during which the water
molecules that were trapped in the pores of the coordination poly-
mers were replaced by ethanol. Specifically, samples consisting of
large crystals and having a weight in the range of 60–80 mg were
stirred at room temperature with 5 mL of ethanol for 6 h, then the
sample was centrifuged at 6,000 rpm for 15 min, and the super-
Again, the percentage recorded for the residue at the end of the
thermal decomposition experiment for coordination polymer 5
(16.22%) is lower even than the theoretical cadmium content of
the sample (22.95%). A succession of gentle stages, that account
for a total weight loss of 8.35% due to the release of two coordi-
nated water molecules and three lattice water molecules (calcd.
Fig. 6. View of the 1D supramolecular unit in the crystal structure of 7. H-bond parameters: O4-HꢀꢀꢀO2 [O4-H 0.820 Å, HꢀꢀꢀO2 1.790 Å, O4ꢀꢀꢀO2(1 + x, y, ꢁ1 + z) 2.599(4) Å,
\O4HO2 168.7°].
9

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
Fig. 7. X-ray molecular structure of complex 8 with the atom labelling and thermal ellipsoids at 50% probability.
Fig. 8. View of the 1D supramolecular layer in the crystal structure of complex 8. Non-relevant H-atoms are omitted for clarity. H-bonds are drawn in dashed-black lines. H-
bonds parameters: O1w-HꢀꢀꢀO2 [O1w-H 0.86 Å, HꢀꢀꢀO2 2.02 Å, O1wꢀꢀꢀO2(1 -x, -y, 1 -z) 2.768(3) Å, \O1wHO2 144.5°]; O1w-HꢀꢀꢀO3 [O1w-H 0.87 Å, HꢀꢀꢀO3 2.04 Å, O1wꢀꢀꢀO3(-x, -y,
-z) 2.900(3) Å, \O1wHO3 166.9°]; O4-HꢀꢀꢀO1 [O4-H 0.82 Å, HꢀꢀꢀO1 1.80 Å, O4ꢀꢀꢀO1(-1 + x, ꢁ1 + y, ꢁ1 + z) 2.613(2) Å, \O4HO1 169.4°].
natant was removed. Fresh ethanol (5 mL) was added to the sam-
ple, which was then stirred for 22 h and centrifuged again.
Removal of the solvent afforded powder-like materials, which were
allowed to dry in the centrifugation tubes, first at room tempera-
ture for 24 h, then in a vacuum oven at 50 °C and 0.02 MPa for
4 h. The determined Brunauer-Emmett-Teller (BET) surface areas
for the activated coordination polymers were small (2.8 m2/g for
4, 1.4 m2/g for 5, 2.2 m2/g for 6 and 22.4 m2/g for 9). These low
specific surface areas, in conjunction with limited pore volume
available for adsorption processes in the micropores, suggest that
adsorption for these coordination polymers mainly occurs on the
external surface of the material as a fine powder, in the diffusion
region.
ancillary ligand in their structures, making them the first coordina-
tion polymers derived from 1-(4-carboxyphenyl)-5-methyl-1H-
1,2,3-triazole-4-carboxylic acid to present co-ligands in their struc-
tures. They were both solved in the Pccn space group and their unit
cell parameters are similar despite featuring different bipyridine
co-ligands. The use of different solvents in the reaction of the
1,2,3-triazole-containing dicarboxylate ligand with Cu(II) ions led
to distinct neutral complexes, which form 1D or 2D supramolecu-
lar arrangements. Evaluation of the specific surface of the Cd(II)-
and Co(II))-based coordination polymers produced poor results,
which indicate that the 3D networks are not useful as materials
for gas storage.
CRediT authorship contribution statement
4. Conclusions
Bogdan-Ionel Bratanovici: Investigation, Methodology, Formal
analysis, Data curation. Sergiu Shova: Investigation, Formal analy-
sis, Writing - original draft. Vasile Lozan: Formal analysis, Writing
A 1,2,3-triazole-containing dicarboxylate ligand was employed
for the synthesis of three hitherto unreported coordination poly-
mers containing Cd(II) ions and two new mononuclear complexes
based on the Cu(II) ion. In addition, a previously known Co(II)-con-
taining coordination polymer derived from the same ligand was
obtained with improved yields under different experimental con-
ditions. Single crystal X-ray analysis showed that this organic lin-
ker behaves as a tridentate ligand in these polymers, as both
carboxylate groups and N-3 in the 1,2,3-triazole ring coordinate
to the metal center. One of the Cd(II)-based coordination polymers
was obtained as a pure enantiomer in the Sohnke R3 space group of
the trigonal system. The remaining two Cd(II)-based coordination
polymers included either 4,40-bipyridine or 4,40-azopyridine as
˘
- original draft. Ioan-Andrei Dascalu: Investigation, Formal analy-
sis, Data curation. Rodinel Ardeleanu: Investigation, Data cura-
tion. Gheorghe Roman: Conceptualization, Supervision, Writing -
original draft, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
10

Bogdan-Ionel Bratanovici, S. Shova, V. Lozan et al.
Polyhedron 200 (2021) 115115
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