Synthesis, structures, catalytic, and anticancer activities of some coordination compounds involving two new triazole derivatives

Article abstract of DOI:10.1080/00958972.2015.1042375

Five N-heterocyclic carboxylate-based coordination complexes, [Co(L¹)₂(H₂O)₂]·2H₂O (1), [Cd(L¹)₂(H₂O)₂]·2H₂O (2), [Co(L²)(H₂O)₃] (3), [Ni(L²)(H₂O)₃] (4), and [Cu₂(L²)₂(H₂O)₂] (5), have been synthesized and characterized by elemental analysis, IR spectroscopy, Powder X-ray diffraction, thermogravimetric analyses, and single-crystal X-ray crystallography, where HL¹ is 2-((5-amino-1H-1,2,4-triazol-3-yl)thio)acetic acid and H₂L² is 2-((5-amino-1-(carboxymethyl)-1H-1,2,4-triazol-3-yl)thio)acetic acid. In these complexes, the hydrogen bonds (H-bonds) play an important role in their packing structures. Complex 1 has nine H-bonds showing a 3-D sqc38 topology. Complex 2 has 17 H-bonds exhibiting a 3-D hxl network. Complexes 3 and 4 are isomorphic, both of which possess ten H-bonds to present a 3-D btc topology. Complex 5 with eight H-bonds forms a 2-D sq1 structure. In addition, complex 3 catalyzes the decolorization of methyl orange. Meanwhile, 1, 3, and 5 show certain anticancer activities to inhibit the growth of HepG2 cells.

Full text of DOI:10.1080/00958972.2015.1042375

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Synthesis, structures, catalytic,
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new triazole derivatives
a
a
b
a
Dan Xiao , Ying-Hui Yu , Zi-Shi Wang , Chun-Hui Yu , Guang-Feng
ab
a
a
a
Hou , Yan-Mei Chen , Xian-Feng Gong , Dong-Sheng Ma & Jin-
ab
Sheng Gao
a
School of Chemistry and Materials Science, Heilongjiang
University, Harbin, China
b
Engineering Research Center of Pesticide of Heilongjiang
University, Heilongjiang University, Harbin, China
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Journal of Coordination Chemistry, 2015
http://dx.doi.org/10.1080/00958972.2015.1042375
Synthesis, structures, catalytic, and anticancer activities of
some coordination compounds involving two new triazole
derivatives
DAN XIAO†, YING-HUI YU†, ZI-SHI WANG‡, CHUN-HUI YU†,
GUANG-FENG HOU*†‡, YAN-MEI CHEN†, XIAN-FENG GONG†,
DONG-SHENG MA*† and JIN-SHENG GAO†‡
†School of Chemistry and Materials Science, Heilongjiang University, Harbin, China
‡Engineering Research Center of Pesticide of Heilongjiang University, Heilongjiang University,
Harbin, China
(Received 2 November 2014; accepted 26 March 2015)
Five N-heterocyclic carboxylate based coordination complexes are synthesized which all show
hydrogen bonding supramolecular structures, and the photocatalytic and anticancer activities of them
are investigated.
1
Five N-heterocyclic carboxylate-based coordination complexes, [Co(L )
2
(H
2
O)
2
2
]·2H
2
O (1), [Cd
1
2
2
2
(
L )
(H
2 2
O)
2
]·2H
2
O (2), [Co(L )(H
2
O)
3
] (3), [Ni(L )(H
O)
2 3
] (4), and [Cu
2
(L )
2
(H O)
2
] (5), have been
synthesized and characterized by elemental analysis, IR spectroscopy, Powder X-ray diffraction,
1
thermogravimetric analyses, and single-crystal X-ray crystallography, where HL is 2-((5-amino-1H-
2
1,2,4-triazol-3-yl)thio)acetic acid and H
2
L
is 2-((5-amino-1-(carboxymethyl)-1H-1,2,4-triazol-3-yl)
thio)acetic acid. In these complexes, the hydrogen bonds (H-bonds) play an important role in their
packing structures. Complex 1 has nine H-bonds showing a 3-D sqc38 topology. Complex 2 has 17
H-bonds exhibiting a 3-D hxl network. Complexes 3 and 4 are isomorphic, both of which possess ten
H-bonds to present a 3-D btc topology. Complex 5 with eight H-bonds forms a 2-D sq1 structure. In
addition, complex 3 catalyzes the decolorization of methyl orange. Meanwhile, 1, 3, and 5 show
certain anticancer activities to inhibit the growth of HepG2 cells.
Keywords: Crystal structure; Triazole; Hydrogen bond; Catalytic property
*
Corresponding authors. Email: hougf@hlju.edu.cn (G.-F. Hou); 1986011@hlju.edu.cn (D.-S. Ma)
2015 Taylor & Francis
©

2
D. Xiao et al.
1. Introduction
Construction of nitrogen-containing heterocycles (N-heterocycles) has attracted significant
interest owing to their enormous structural diversity and intriguing molecular topologies as
well as promising applications as functional materials in catalysis, sorption, ion exchange,
sensors, nonlinear optics, magnetism, etc. [1–3]. It is well-known that some simple
N-heterocyclic ligands, such as pyridine, imidazole, pyrazine, and triazole, could be easily
obtained and modified. Therefore, decoration of carboxylic acid groups to these N-heterocy-
cles has become a simple and effective approach to prepare multidentate ligands. As multi-
dentate ligands, the obtained N-heterocyclic carboxylates possess both oxygen and nitrogen
donors, which can coordinate with metal ions [4–6]; pyridine-2,n-dicarboxylic acids (n = 3,
5
, 6) (scheme S1, see online supplemental material at http://dx.doi.org/10.1080/00958972.
2
015.1042375) are examples. Several examples have been reported including 3d–4f
heterometallic coordination complexes as selective luminescent probes [7–12].
In addition to six-membered N-heterocycles, five-membered rings such as imidazole, tria-
zole, etc. can also be modified by carboxylic acid groups to construct new ligands, however,
the reports of which are relatively few. In 2007, Du et al. found that reaction of 2-(4-pyri-
dyl)thiazole-4-carboxylic acid (Hptca) (scheme S1) with different divalent metal ions could
lead to diverse metal-organic supramolecular architectures in different dimensions [13]. In
2
1
012, Hou et al. reported a series of coordination complexes based on 2-((1H-1,2,4-triazol-
-yl)methyl)-1H-imidazole-4,5-dicarboxylic acid (H tmidc) (scheme S1) exhibiting unique
3
structures and excellent magnetic properties [14]. Triazole and its derivatives usually have
good biological activities [15, 16], which could be maintained in their coordination
complexes [17]. However, reports of the biological activities of triazole complexes are still
limited. Some N-heterocyclic carboxylate ligands reported in recent years are listed in
scheme S1.
We present here two N-heterocyclic carboxylate ligands, 2-((5-amino-1H-1,2,4-triazol3-
1
yl)thio)acetic acid (HL ) and 2-((5-amino-1-(carboxymethyl)-1H-1,2,4-triazol-3-yl)thio)
2
acetic acid (H L ), which are synthesized from 5-amino-1H-1,2,4-triazole-3-thiol with
2
chloroacetic acid. The amino- and mercapto-groups are introduced into the triazole ring
considering the following points: (a) the existence of –NH , –NO , and –OH groups
2
2
could enhance the performance of the triazole derivatives in biological activities and gas
adsorption properties [18–21] and (b) the –NH and –SH groups can be easily further
2
decorated with carboxylate and other functional groups [22]. Five complexes are con-
1
2
structed by HL or H2L reacting with transition metals in different conditions: [Co
1
1
2
2
(
(
L ) (H O) ]·2H O (1), [Cd(L ) (H O) ]·2H O (2), [Co(L )(H O) ] (3), [Ni(L )(H O) ]
2 2 2 2 2 2 2 2 2 3 2 3
2
4), and [Cu (L ) (H O) ] (5). Noticeably, there are abundant hydrogen bonds (H-bonds)
2
2
2
2
in these complexes. Though hydrogen bonds are not normally as strong as coordinate
bonds, their combined influence can make a huge impact on the resulting network
[
23–26], due to the fact that complementary H-bonding interactions contribute signifi-
cantly to shaping the hierarchical supramolecular structure. When a metal-organic com-
plex is formed, the noncoordinated nitrogen donor sites can H-bond forming a
supramolecular structure [27]. These five complexes with free –NH groups, uncoordi-
2
nated N of triazole, and the crystallization water molecules are good candidates for
constructing supramolecular architectures (scheme 1).

New triazole derivatives
3
N
NH
HN
NH SCN
4
C
NH
NH
NH
2
HS
N
ATT
H
2
N
2
N
NH
HOOC
NH2
ci
d
S
HL1
a
N
tic
ce
a
I
C
ro
H
,
l
o
h
H
O
C
N
NH
Na
,
3
O
a
2C
NH
2
N
C
HS
N
hl
or
CO
oa
ce
N
ti
c a
a2
ATT
cid
COOH
3
, N
N
N
aO
H
,
H
HOOC
C
NH
2
I
S
H2L2
N
1
2
Scheme 1. The synthetic route of HL and H
2
L .
2
2
. Experimental
.1. Materials and method
All solvents and reagents for the syntheses were commercially available and used as
received. Elemental analyses were performed on a PerkinElmer-2400 Series II analyzer. IR
spectra were recorded on a PerkinElmer precisely Spectrum 100 apparatus from 450 to
−
1
1
4
000 cm . The dry sample powder is mixed with KBr for IR spectra. The H-NMR spec-
tra were recorded on a Bruker 400 MHz NMR spectrometer (USA) using DMSO as a sol-
vent. Powder X-ray diffraction (PXRD) measurements were performed on a Bruker D8
Advance X-ray diffractometer using Cu-Kα radiation (λ = 1.5418 Å), in which the X-ray
tube was operated at 40 kV and 40 mA at room temperature and compared to simulated pat-
terns. The UV–vis spectra were recorded on a PerkinElmer lambda 25 using distilled water
as a solvent. Thermogravimetric measurements were performed on a PerkinElmer TGA 7
analyzer.
1
2
2
.2. Preparation of HL and H L
2
1
2
HL and H L were prepared from the same reactants, 5-amino-1H-1,2,4-triazole-3-thiol
2
and 2-chloroacetic acid under different molar ratio and reaction conditions.
Step 1: A mixture of aminoguanidine bicarbonate (27.78 g, 0.2 mol), ammonium thio-
cyanate (8.27 g, 0.24 mol), and 10 mL of distilled water was added into a 250-mL three-
necked flask equipped with a motor stirrer, a thermometer, and a tail gas absorption device.
The resulting solution was heated to 80 °C under stirring until no air bubbles were
observed, and the produced water was then removed by vacuum distillation. Concentrated
hydrochloric acid (27.6 mL) was added dropwise to the above mixture and kept stirring for
1
h. After that, 22 mL aqueous solution (40%) of NaOH was added dropwise, and the
resulting solution was heated and refluxed for 2 h, which was then cooled to room tempera-
ture. The white gray crude product was obtained by filtration after the pH was adjusted to 1
by concentrated hydrochloric acid. Recrystallization of the crude product from water gives
1
white pure 5-amino-1H-1,2,4-triazole-3-thiol (ATT) with a yield of 80.1%. H-NMR

4
D. Xiao et al.
−
1
(
1
400 MHz, DMSO) δ: 12.26 (s, 1H), 12.04 (s, 1H), 5.72 (s, 2H). IR (KBr, cm ): 3378(m),
644(s), 1584(m), 1481(m), 1231(s), 1135(m), 1066(w), 1025(m). Elemental Analysis (%):
Found (Calcd) for ATT: C, 20.72 (20.68); H, 3.45 (3.47); N, 48.22 (48.24).
Step 2: A mixture of ATT 11.6 g (0.1 mol), sodium carbonate 10.6 g (0.1 mol), and
sodium hydroxide 4 g (0.1 mol) was added into 100 mL of water under stirring, and then,
the reaction system was cooled to 10 °C and kept for 15 min to get a clear solution. Then,
50 mL water solution containing chloroacetic acid (11.3 g, 0.12 mol) and sodium hydroxide
(
4.8 g, 0.12 mol) was added dropwise [chloroacetic acid (20.8 g, 0.22 mol) and sodium
2
hydroxide (8.8 g, 0.22 mol) were used for synthesis of H L ]. The resultant solution was
2
heated to reflux with stirring for 8 h, cooled to room temperature, and then, the pH was
adjusted to about 2 with concentrated hydrochloric acid. After stirring for 20 min, the pro-
1
duct of 2-((5-amino-1H-1,2,4-triazol-3-yl)thio)acetic acid HL with a yield of 75.2% was
2
obtained [2-((5-amino-1-(carboxymethyl)-1H-1,2,4-triazol-3-yl)thio)acetic acid H L with a
2
1
1
−1
yield of 73.4%]. HL : H-NMR (400 MHz, DMSO) δ: 3.50 (s, 2H, CH ). IR (KBr, cm ):
2
1
586 (s), 1411 (s), 1281 (w), 1215 (m), 1083 (m), 897 (w). Elemental Analysis (%): Found
1
2
1
(Calcd) for HL : C, 27.45 (27.58); H, 3.52 (3.47); N, 32.25 (32.17). H L : H-NMR
2
(
400 MHz, DMSO) δ: 6.41 (s, 2H, CH ), 4.57 (s, 2H, CH ), 3.78 (s, 2H, NH ). IR (KBr,
2
2
2
2
−
1
cm ): 1730 (s), 1676 (s). Elemental Analysis (%): Found (Calcd) for H L : C, 31.08
2
(31.03); H, 3.44 (3.47); N, 24.11 (24.13).
2
.3. Syntheses of 1–5
.3.1. Syntheses of [Co(L ) (H O) ]∙2H O (1). A mixture of HL (0.5 mmol, 0.087 g),
1
1
2
2
2
2
2
CoCl ·6H O (0.5 mmol, 0.12 g) and 5 mL distilled water was added into a 20-mL Teflon-
2
2
lined autoclave and the pH adjusted to 7 by NaOH solution (4 M). The autoclave was
heated at 120 °C for 72 h. After cooling slowly to room temperature, pink block crystals
were obtained. Yield: 171.8 mg (72% yield based on Co). Elemental analysis (%): Found
(
Calcd) for C H CoN O S : C, 20.17 (20.13); H, 3.78 (3.80); N, 23.41 (23.48). IR (KBr,
8 18 8 8 2
−
1
cm ): 1632 (s), 1570 (s), 1499 (s), 1400 (s), 1367 (m), 1287 (m), 1242 (s), 1116 (m), 1072
(m), 1012 (w), 939 (m), 906 (s).
1
2
.3.2. Synthesis of [Cd(L ) (H O) ]·2H O (2). The preparation of 2 was similar to that
2
2
2
2
of 1 except that the CdCl ·2.5H O (0.5 mmol, 0.114 g) was used instead of CoCl ·6H O,
2
2
2
2
and the pH was adjusted to 8–9. Colorless block crystals were filtered and washed with dis-
tilled water. Yield: 132.7 mg (50% yield based on Cd). Elemental analysis (%): Found
(
Calcd) for C H CdN O S : C, 18.13 (18.10); H, 3.47 (3.42); N, 21.05 (21.11). IR (KBr,
8 18 8 8 2
−
1
cm ): 1649 (s), 1570 (s), 1494 (s), 1394 (m), 1380 (m), 1282 (m), 1249 (s), 1110 (m),
1
062 (m), 1022 (w), 925 (m), 901 (m).
2
2
2
.3.3. Synthesis of [Co(L )(H O) ] (3). A mixture of H L (0.5 mmol, 0.115 g),
2
3
2
CoCl ·6H O (1.5 mmol, 0.36 g), and 5 mL distilled water was added into a 20-mL Teflon-
2
2
lined autoclave and the pH adjusted to 7 by NaOH solution (4 M). The autoclave was
heated at 120 °C for 72 h. After slowly cooling to room temperature, purple block crystals
were obtained. Yield: 324.3 mg (63% yield based on Co). Elemental analysis (%): Found
(
Calcd) for C H CoN O S: C, 21.03 (21.00); H, 3.49 (3.52); N, 16.31 (16.33). IR (KBr,
6 12 4 7

New triazole derivatives
5
−
1
cm ): 1670 (m), 1581 (s), 1514 (m), 1398 (m), 1329 (s), 1272 (w), 1130 (m), 1022 (w),
9
48 (m), 862 (w), 729 (m), 667 (w).
2
2
.3.4. Synthesis of [Ni(L )(H O) ] (4). The preparation of 4 was similar to that of 3
2
3
except that Ni(CH COO) ·4H O (0.3 mmol, 0.075 g) was used instead of CoCl ·6H O.
3
2
2
2
2
3
9.1 mg light green diamond-shaped crystals were obtained (38% yield based on Ni). Ele-
mental analysis (%): Found (Calcd) for C H NiN O S: C, 21.07 (21.01); H, 3.56 (3.53);
6
12
4 7
−
1
N, 16.31(16.34). IR (KBr, cm ): 1669 (m), 1585 (s), 1511 (m), 1409 (m), 1322 (s), 1275
(w), 1225 (m), 1118 (m), 1019 (w), 955 (m), 854 (w), 719 (m), 661 (m).
2
2
2
.3.5. Synthesis of [Cu (L ) (H O) ] (5). The mixture of H L (0.25 mmol, 0.058 g), Cu
2 2 2 2 2
(
NO ) ·3H O (0.5 mmol, 0.121 g), acetonitrile (5 mL), distilled water (5 mL), and a drop
3 2 2
of NaOH (4 M) was kept stirring for 30 min and then filtered. The filtrate was slowly
evaporated at room temperature to obtain dark green block-shaped crystals in a few days.
Yield: 73.3 mg (47% yield based on Cu). Elemental analysis (%): Found (Calcd) for
−1
C H Cu N O S : C, 23.10 (23.12); H, 2.61 (2.59); N, 17.95 (17.97). IR (KBr, cm ):
1
2
16
2 8 10 2
1
6
642 (s), 1564 (s), 1495 (m), 1372 (s), 1319 (m), 1258 (w), 1123 (m), 955 (w), 725 (m),
01 (m).
2
.4. X-ray crystallography
Suitable single crystals of 1–5 were carefully selected under an optical microscope and
glued to thin glass fibers. Crystallographic data for all complexes were collected with a Sie-
mens SMART CCD diffractometer with graphite-monochromated Mo Ka radiation
(
λ = 0.71073 Å) at T = 293(2) K. Data processing was accomplished using SAINT. The2
structures were solved using direct methods and refined by full-matrix least-squares on F
using SHELX–97 [28]. All non-hydrogen atoms were refined anisotropically. A summary
of the crystallographic data and structure refinement parameters for 1–5 are given in table
1
. Selected bond lengths and angles for 1–5 are given in table S1. Hydrogen bond
parameters for 1–5 are given in table S2. CCDC 1015799–803 contain the supplementary
crystallographic data for 1–5.
2
.5. Decolorization of MO
The decolorization experiment of MO is conducted in a 250-mL glass beaker. In this experi-
−
1
ment, 50 mL MO sample with the original concentration of 15 mg L is used and six
parallel experiments conducted at the same time. All experiments were carried out under
conditions of sunlight and room temperature. The concentration of MO is measured by the
UV maximum absorption wavelength at 464 nm.
2
.6. Anticancer activity test for HepG2 cells
5
−1
The HepG2 cells with density of 1 × 10 cells mL were seeded in 96-well plates and 1, 3,
and 5 were added with the final concentration of 150 μM. After culturing for 24 h, the
supernatant was taken out of the well plates and 100 μL sterilized 0.9% sodium chloride

6
D. Xiao et al.

New triazole derivatives
7
solution was added to wash the well plates, and then, the supernatant was discarded again.
Then, 100 μL new culture solution and 20 μL MTT (3-(4,5-dimethyl-thiazol-2)-2,5-diphe-
nyl tetrazole bromide) dyeing liquid were added to the incubator. After 4 h, the supernatant
was removed in the plates and 150 μL DMSO was added to each well and vibrated for
1
0 min in the micro-oscillator. The inhibition rates for HepG2 cells were calculated by the
absorbance value A of the solution measured by enzyme immunoassay instrument.
Ablank ꢀ A
dosing group
Inhibition rate ð%Þ ¼
ꢁ 100%
A
blank
3
3
. Results and discussion
.1. Crystal structure descriptions
Complexes 1–4 were hydrothermally synthesized and 5 was obtained by volatilizing its
supersaturated solution. Influence of the reaction conditions on the synthesis of 1–4 was
also investigated, such as temperature, molar ratio of the reactants, solvent, pH as well as
the filling degree of the autoclave. The pH value plays a key role in the formation of 1–4.
Figure 1. (a) The coordination environment of Co(II) in 1. (b) The details of nine H-bonds in the asymmetric unit.
(
c) Side view of 3-D H-bonding network along the c axis. (d) Schematic illustration of the 3-D 6-connected sqc1
12 3
network with a point symbol (4 ·6 ) formed by H-bonds (the lattice water molecules were excluded). (e) 3-D
1
36
48
7
4-connected sqc38 network with a point symbol of (3 ·4 ·5 ) of 1. Symmetry code: I = 1 − x, −y, 1 − z.

8
D. Xiao et al.
Figure 2. (a) The coordination environment of Cd(II) in 2. (b) The details of eight H-bonds of the asymmetric
6
6
3
unit excluding the lattice water molecules. (c) 2-D H-bonding hxl network with a point symbol of (3 ·4 ·5 ). (d) 17
H-bonds of the asymmetric unit containing lattice waters. (e) 3-D 12-connected sqc19 network with a point symbol
24
36
6
of (3 ·4 ·5 ).
1
2
Both L and L decompose when the reaction temperature is higher than 170 °C. For the
synthesis of 5, experiments were tried under other conditions, but no suitable single crystals
were obtained.
Complex 1. Single-crystal X-ray analysis shows that 1 crystallized in the monoclinic sys-
1
tem with P2 /c space group. The asymmetric unit of 1 consists of a half of Co(II), one L ,
1
one coordinated water, and one crystallization water. As shown in figure 1(a), Co ion is six-
coordinate with slightly distorted octahedral geometry surrounded by two oxygens and two
I
I
1
nitrogens (O1, O1 , N1, and N1 ) from two crystallographic independent L ligands and
I
two waters (O3 and O3 ). The Co1–O distances are 2.101(1)–2.124(2) Å, while Co1–N
bond length is 2.136(2). The angles around Co ion are 84.85(6)–180°.
In 1, one asymmetric unit has nine H-bonds [figure 1(b)] to connect the adjacent units
and lattice water molecules leading to a 3-D supramolecular structure [figure 1(c)]. When
1
the lattice water is excluded, one [Co(L ) (H O) ] building block would connect other six
2
2
2
1
2
3
blocks to get a sqc1 topology with a point symbol of (4 ·6 ) [figure 1(d)]. However, the
lattice waters fill in the cavities to form H-bonds with the coordinated water, the carboxylate
groups, and the uncoordinated N of L , which further intertwines with the sqc1 network
into a 14-connected sqc38 network with a point symbol of (3 ·4 ·5 ) simplified by the
TOPOS program [29] [figure 1(e)].
1
3
6
48
7

New triazole derivatives
9
Figure 3. (a) The coordination environment of Co(II) in 3. (b) The details of ten H-bonds. (c) 3-D structure of 3
built up by H-bonds. (d) Schematic illustration of the 3-D 9-connected btc network with a point symbol of
9
19
8
(
3 ·4 ·5 ).
Complex 2. Complex 2 also crystallized in the monoclinic system with P2 /c space
1
1
group. The asymmetric unit consists of one Cd(II), two L ligands, two coordinated waters,
and two lattice waters [figure 2(a)]. Cd1 is six-coordinate with slightly distorted octahedral
geometry surrounded by two oxygens and two nitrogens (O1, O3, N1, and N5) from two
1
crystallographic independent L ligands and two water ligands (O5 and O6). The Cd–O dis-
tances are 2.326(3)–2.350(2) Å and the Cd–N bond lengths are 2.263(3)–2.264(3) Å. When
the lattice water molecules are not considered, there are eight H-bonds in the asymmetric
1
unit of 2 [figure 2(b)], which link another six [Cd(L ) (H O) ] moieties to build up a 2-D
2
6
2
3
2
6
6
-connected hxl topology with a point symbol of (3 ·4 ·5 ) [figure 2(c)]. The lattice water
1
molecules fill in the cavities of this hxl network and form H-bonds with [Cd(L ) (H O) ]
2
2
2
moieties. As a result, the neighboring sheets are further pillared to construct a 3-D
supramolecular architecture, which can be simplified to 12-connected sqc19 network with a
2
4
36
6
point symbol of (3 ·4 ·5 ).
Complex 3. Single-crystal X-ray analysis shows that 3 and 4 are essentially isomorphic,
so only the structure of 3 is described here in detail. Complex 3 crystallized in the triclinic
2
system with Pī space group. The asymmetric unit of 3 consists of one Co(II), one L , and
three coordinated waters [figure 3(a)]. Co1 is also six-coordinate with slightly distorted
octahedral geometry, but surrounded by two oxygens and one nitrogen (O2, O3, and N1)
2
2
from L and three water ligands (O5, O6, and O7). In 3, L is tridentate with Co1, being

1
0
D. Xiao et al.
Figure 4. (a) The molecular structure of 5. (b) The details of eight H-bonds. (c) 2-D structure of 5 formed by
4
2
H-bonds. (d) Schematic illustration of the sq1 topology of 5 with a point symbol of (4 ·6 ). Symmetry codes:
I = 1 − x, y, 1.5 − z.
1
different from that of 1, in which the L is bidentate. The Co1–O distances are 2.037
(
2)–2.152(2) Å and the Co1–N bond length is 2.141(2) Å, similar to those of 1.
2
The crystal structure of 3 shows the self-organizing behavior of [Co(L )(H O) ] building
2
3
blocks derived from a variety of H-bonds. The asymmetric unit of 3 with ten H-bonds
2
[
figure 3(b)] links adjacent nine [Co(L )(H O) ] moieties leading to a supramolecular 3-D
2 3
network [figure 3(c)]. Furthermore, this network can be simplified to btc net structure with
9
19
8
2
a point symbol of (3 ·4 ·5 ), when the [Co(L )(H O) ] moieties are seen as 9-connected
2
3
nodes [figure 3(d)].
Complex 5. Complex 5 also crystallized in the triclinic system with Pī space group. The
results of crystallographic analysis reveal that the asymmetric unit of 5 consists of one Cu
2
(
II), one L ,and one coordinated water ligand. Figure 4(a) shows the molecular structure of
5
, in which Cu1 is five-coordinate with slightly distorted square pyramidal geometry
I
2
defined by three oxygens and one nitrogen (O1, O1 , O3, and N1) from one L and one
water (O5). The Cu1–O distances are 1.908(3)–2.323(3) Å and the Cu1–N bond length is
1
.977(3) Å. Each molecule of 5 possesses eight H-bonds [figure 4(b)] linking the adjacent
four molecules into a 2-D wavelike structure [figure 4(c)]. If the molecule can be seen as a
-connected node, the sheet could be simplified to sq1 topology with a point symbol of
4
4
2
(4 ·6 ) [figure 4(d)].

New triazole derivatives
11
3
.2. PXRD and TGA studies
In order to characterize the phase purity of other crystalline materials, PXRD patterns for
–5 were performed at room temperature (figure S2). The location and intensity of diffrac-
1
tion peaks of calculated and experimental patterns match well, indicating that these com-
plexes were synthesized as a single phase.
Thermogravimetric experiments of 1–5 were carried out in the atmosphere from 30 to
8
00 °C. The TGA curves of 1–5 are shown in figure S3. The TG curve of 1 suggests that 1
exhibits four main steps of weight losses. The first weight loss is at 104–166 °C, corre-
sponding to loss of two lattice water molecules and two coordinated waters (found 14.75%,
Calcd 15.08%). The second step of weight loss from 166 to 320 °C corresponds to the
1
removal of carboxyl from one L (found 9.06%, Calcd 9.21%). The third step of
1
3
20–495 °C is consistent with decomposition of the decarboxylated L (found 28.59%,
Calcd 27.23%). The fourth step of 30.16% from 495 to 585 °C can be attributed to decom-
1
1
position of the other L (Calcd 32.89%). In short, two HL ligands are lost in a continuous
fashion from 166 to 585 °C (found 67.93%, Calcd 69.13%) with residue of CoO (found
1
5.42%, Calcd 15.69%). Complex 2 loses its lattice and coordinated waters from 108 to
1
62 °C (found 12.59%, Calcd 13.56%). The mass loss of 27.60% between 162 and 366 °C
1
1
can be attributed to loss of L (Calcd 29.57%), then the decomposition of the other L
occurred from 366 to 538 °C (found 30.27%, Calcd 32.60%) with the residue of CdO
found 25.57%, Calcd 24.11%). Complexes 3 and 4 are isomorphic with similar TG curves.
(
The first weight loss could be ascribed to loss of three coordinated waters (108–160 °C,
found 14.93%, Calcd 15.73% for 3, 112–183 °C, found 14.62%, Calcd 15.74% for 4). The
second weight loss may correspond to loss of two carboxyl groups (160–358 °C, found
2
3.32%, Calcd 25.64% for 3, 183–354 °C, found 27.89%, Calcd 25.66% for 4). The third
2
and the fourth weight losses are equivalent to loss of the other residues of L (358–541 °C,
found 39.36%, Calcd 41.96% for 3, and 354–519 °C, found 39.14%, Calcd 41.98% for 4).
The remaining weight can be ascribed to CoO for 3 (found 23.58%, Calcd 21.83%) and
NiO for 4 (found 21.07%, Calcd 21.78%). Complex 5 exhibits three weight loss stages.
The first 5.89% (Calcd 5.77%) from 54 to 174 °C corresponds to loss of two coordinated
waters. The second and the third stage, occurring between 174 and 530 °C (found 80.21%,
2
Calcd 81.40%) are equivalent to decomposition of two H L ligands with residue of CuO
2
(found 12.52%, Calcd 12.83%).
3
.3. Effect of different processes on decolorization of MO
In order to investigate the effect of these complexes on dye decolorization, MO solutions
were exposed under six different processes: (a) direct photolysis under solar light
irradiation; (b) 10 drops of hydrogen peroxide under solar light irradiation; (c) complex
3
-H O system under solar light irradiation; (d) complex 3 under solar light irradiation; (e)
2 2
2
H L -H O system under solar light irradiation; (f) CoCl -H O system under solar light
2
2
2
2
2 2
irradiation. The results are shown in figure 5. Obviously, almost no decolorization of MO
solution was observed in a, b, e, and f. The removal rate of MO solution was about 37.5%
after 17 h in process (d) when complex 3 acted as catalyst [figure 5(d)]. Interestingly, about
8
0.7% of MO was decolorized after 17 h in the case of 0.058 mmol of 3 in the presence of
H O [figure 5(c)]. The results imply that 3 has visible light photocatalytic activity for
2
2
decolorization of MO at atmospheric conditions, while, when H O was utilized as oxidant
2
2
[
30, 31], the catalytic efficiency is significantly improved.

1
2
D. Xiao et al.
Figure 5. UV–vis spectra of the different processes for decolorization of MO in aqueous solution: (a) direct
photolysis under solar light irradiation; (b) 10 drops of hydrogen peroxide under solar light irradiation; (c) 3-H
system under solar light irradiation; (d) 3 as catalyst under solar light irradiation; (e) catalytic decolorization by
2 2
O
2
H
2
L -H
2
O
2
system under solar light irradiation; (f) CoCl
2
-H
2 2
O system under solar light irradiation. Experimental
−
1
conditions: [MO]
0
= 15 mg·L ; CH2O2 = 30%; initial pH 5.8; N(Catalyst) = 0.058 mmol.
3.4. Anticancer activities
In 1970s, Rosenberg found that platinum compounds have anticancer activity, which
opened up a new direction for cancer drug research as a new class of potent antitumor
1
2
agents [32]. Considering the biologically active triazole groups in HL and H L [33–36],
2
the cytotoxicity tests of this series of complexes were carried out. The cytotoxicity tests for

New triazole derivatives
13
Figure 6. Results of MTT assay of 1, 3, and 5 on HepG2 cells at concentration ranging from 0 to 150 μM.
1
, 3, and 5 were assessed by the MTT assay. The HepG2 cells were incubated in the
presence of 1, 3, and 5 in different concentrations for 24 h.
The assay was performed in triplicate, and the results of MTT assay on HepG2 cells with
complexes concentration ranging from 0 to 150 μM are shown in figure 6. Complexes 1, 3,
and 5 showed obvious inhibitory activities on HepG2 cells under tested concentrations for
2
5
4 h. The HepG2 cell inhibition rate increased with increasing concentrations of 1, 3, and
. Complexes 3 and 5 exhibit much better inhibitory activities than 1. More than 40% of
HepG2 cells could be inhibited in the presence of 75 μM of 3 or 5.
4
. Conclusion
1
2
Five complexes based on N-heterocyclic carboxylate ligands HL or H L and transition
2
metals have been hydrothermally/solvothermally synthesized. The remarkable feature of the
structure of this series of complexes is the existence of many H-bonds. It can be attributed
1
2
to both HL and H L having multiple H-bonds donor and acceptor groups as well as the
2
existence of water molecules. There are nine H-bonds in 1, seventeen H-bonds in 2, ten
H-bonds in 3 and 4, and eight H-bonds in 5. In these five complexes, the intermolecular
H-bonds drive the building blocks to form 3-D or 2-D supramolecular architectures with
complicated topologies. 3 shows good visible light photocatalytic activity for the decol-
orization of MO at atmospheric conditions. Complexes 1, 3, and 5 have obvious anticancer
activities for inhibiting the growth of HepG2 cells.

1
4
D. Xiao et al.
Supplementary material
Electronic Supplementary Information (ESI) available: X-ray crystallographic files in CIF
format, table of selected bond lengths and bond angles, hydrogen bonds lengths and angles,
FT-IR and PXRD spectra and TGA curves. See doi: 10.1039/b000000x/.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by the National Natural Science Foundation of China [grant number
2
1371052]; Heilongjiang Province Science and Technology Project [grant number GZ13A002].
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