Syntheses, crystal structures, and antibacterial activities of helical M(II) phenyl substituted pyrazole carboxylate complexes

Article abstract of DOI:10.1080/00958972.2014.896993

Six new metal complexes with two kinds of phenyl substituted pyrazole carboxylic acid, [Co(L¹)₂(4,4′-bipy)(H ₂O)₂]_n (1), [Ni(L¹) ₂(4,4′-bipy)(H₂O)₂]_n

Full text of DOI:10.1080/00958972.2014.896993

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Syntheses, crystal structures, and
antibacterial activities of helical
M(II) phenyl substituted pyrazole
carboxylate complexes
a
a
a
a
a
Hong Liu , Gao-Shan Yang , Chong-Bo Liu , Yi Lin , Yi Yang & Yun-
a
Nan Gong
a
School of Environment and Chemical Engineering, Nanchang
Hangkong University, Nanchang, PR China
Accepted author version posted online: 24 Feb 2014.Published
online: 02 Apr 2014.
To cite this article: Hong Liu, Gao-Shan Yang, Chong-Bo Liu, Yi Lin, Yi Yang & Yun-Nan Gong
(
2014) Syntheses, crystal structures, and antibacterial activities of helical M(II) phenyl substituted
pyrazole carboxylate complexes, Journal of Coordination Chemistry, 67:4, 572-587, DOI:
0.1080/00958972.2014.896993
1
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 4, 572–587, http://dx.doi.org/10.1080/00958972.2014.896993
Syntheses, crystal structures, and antibacterial activities of
helical M(II) phenyl substituted pyrazole carboxylate
complexes
HONG LIU, GAO-SHAN YANG, CHONG-BO LIU*, YI LIN, YI YANG and
YUN-NAN GONG
School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang, PR
China
(Received 25 October 2013; accepted 31 January 2014)
Six new metal complexes with two kinds of phenyl substituted pyrazole carboxylic acid,
1
1
1
[
[
3
Co(L )
2
(4,4′-bipy)(H
(4,4′-bipy)(H
2
O)
O)]
2
]
n
n
(1), [Ni(L )
(4), [Ni(L )
2
(4,4′-bipy)(H
2
O)
n
2
]
n
(2), [Cu(L )
2
(4,4′-bipy)(H
2
O)
2 n
] (3),
2
2
2
1
Co(L )
2
2
2
(4,4′-bipy)(H
2
O)]
(5), and [Cu(L )
2
(4,4′-bipy)]
n
(6) (HL =
2
-methyl-1-phenyl-1H-pyrazole-5-carboxylic acid; HL = 5-chloro-3-methyl-1phenyl-1H-pyrazole-4-
carboxylic acid; 4,4′-bipy = 4,4′-bipyridine), were prepared and structurally characterized.
Complexes 1–6 display 1-D structures and further extend to 3-D supramolecular networks by
hydrogen bonding interactions; 1–3 consist of left- and right-handed helical chains and 4–6 contain
*
Corresponding author. Email: cbliu@nchu.edu.cn
©
2014 Taylor & Francis

M(II) pyrazole carboxylates
573
zig-zag chains. Antibacterial activities of 1–6 against bacteria were studied and compared to the
activities of free ligands.
Keywords: Helix; Transition metal complexes; Pyrazole carboxylic acid; N-donor co-ligands;
Antibacterial activities
1. Introduction
Design and syntheses of coordination polymers are studied due to their versatile chemi-
cal and physical properties and potential applications in catalysis, adsorption, solvent
exchange, magnetism, bioactivity, etc. [1–10]. Construction of helical coordination poly-
mers has aroused much attention [11–15] owing to the appearance of helical structures
in proteins, collagens, quartz, single-walled carbon nanotubes, and many more natural
or artificial fiber-type derivatives [16–20], inspiring scientists to engage in syntheses of
artificial helical structures with possible applications in materials sciences, stereoselec-
tive catalysis, chemical sensing, and bioactivity [21–26]. A variety of single-, double-,
and triple-stranded helical structures have been constructed. However, the structures of
complexes depend on combination of several factors, including metal ions, organic
ligands, pH, reaction temperature, etc. [27–30], of which ligand is the most important
influence, so reasonable selection of ligand is key for achieving this target. Carboxylate
with different coordination modes has been extensively used for constructing polynu-
clear clusters, especially pyrazole carboxylic acid ligands have received much attention
owing to some interesting features: they have multiple O- and N-coordination sites
together with hydrogen bond acceptors and donors for the assembly of high-dimen-
sional 3d, 4f or 3d–4f supramolecular networks; an appropriate angle between O- and
N-coordination sites will provide the potential for formation of helices and/or micropo-
rous structures. A phenyl introduced to the pyrazole carboxylic acid enlarges the
ligand, increases the possibility of π–π and C–H⋯π interactions [31, 32], and may
induce different conformations of pyrazole carboxylic acid due to geometrical con-
straints and makes the structures of complexes diverse. Different positions of the car-
boxylate groups on the pyrazole ring may result in different supramolecular structures.
In this paper, we synthesized two phenyl substituted pyrazole carboxylic acids with dif-
ferent positions of carboxylate on the pyrazole ring: 3-methyl-1-phenyl-1H-pyrazole-5-
1
carboxylic acid (HL ) and 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid
2
(
HL ). Metal ions due to their different radii and coordination geometries, and auxiliary
ligands due to their different sizes and coordination modes, often have significant
effects on the formation and structures of complexes [33–35]. In particular, 4,4′-bipy
as a linear bridging auxiliary plays a crucial role in the advancement of coordination
polymers [36, 37]. Herein, we report syntheses and structures of six new transition
metal complexes with two kinds of phenyl substituted pyrazole carboxylic acids and
1
1
1
4
,4′-bipy: [Co(L ) (4,4′-bipy)(H O) ] (1), [Ni(L ) (4,4′-bipy)(H O) ] (2), [Cu(L ) (4,4′-
2 2 2 n 2 2 2 n 2
2
2
bipy)(H O) ] (3), [Co(L ) (4,4′-bipy)(H O)] (4), [Ni(L ) (4,4′-bipy)(H O)] (5), and
2
2 n
2
2
n
2
2
n
2
[
Cu(L ) (4,4′-bipy)] (6), which display helical character through hydrogen bonding
2 n
interactions.

5
74
H. Liu et al.
2
2
. Experimental
.1. Materials and instrumentation
1
2
All reagents, except HL and HL , were commercially available and used without purifica-
1
tion. H NMR spectra were recorded at 400 MHz on a Bruker WH400 DS spectrometer.
The elemental analyses of C, H, and N were carried out with a Flash EA 1112 Elementar
analyzer. IR spectra were recorded with a Nicolet Avatar 360 FTIR spectrometer using KBr
pellets.
1
2
2
.2. Syntheses of HL and HL
1
2
HL and HL were prepared according to the literature [38, 39], as shown in scheme 1.
1
HL , yield ca. 77.8%; m.p. 176–179 °C. Anal. Calcd for C H N O : C, 65.35; H, 4.95;
11 10 2 2
−
1
N, 13.86%. Found: C, 65.10; H, 4.87; N, 13.98%. IR data (KBr pellet, ν/cm ): 3267 m,
987 m, 1802 m, 1666 s, 1578 m, 1522 s, 1480 s, 1331 m, 1281 m. H NMR (DMSO-d ,
1
2
6
4
00 MHz) δ: 3.39 (s, 3H); 6.55 (m, 1H); 7.45–7.53 (m, 5H); 12.44 (s, 1H).
2
HL , yield ca. 82.1%; m.p. 248–250 °C. Anal. Calcd for C H ClN O : C, 55.83;
11
9
2 2
−
1
H, 3.83; N, 11.84%. Found: C, 55.50; H, 3.74; N, 12.04%. IR data (KBr pellet, ν/cm ):
1
3
077 m, 2984 m, 1706 s, 1541 s, 1509 s, 1491 m, 1395 m, 1292 m, 1126 s, 1000 s. H
NMR (DMSO-d , 400 MHz) δ: 3.32 (s, 3H); 7.40–7.74 (m, 5H); 12.87 (s, 1H).
6
1
2
Scheme 1. The synthesis of HL (a) and HL (b).

M(II) pyrazole carboxylates
575
2.3. Syntheses of 1–6
1
Complexes 1–3 have been produced by reaction of HL and 4,4′-bipy with different transi-
2
tion metal ions, while 4–6 have been obtained by the reaction of HL and 4,4′-bipy with
different transition metal ions under hydrothermal conditions.
1
2
0
.3.1. Synthesis of [Co(L ) (4,4′-bipy)(H O) ] (1). A mixture of CoCl ·6H O (0.0238 g,
2
2
2 n
2
2
1
.1 mM), HL (0.0202 g, 0.1 mM), 4,4′-bipy (0.0156 g, 0.1 mM), NaOH (0.45 mL, 0.65 M
L ), and distilled water (10 mL) were sealed in an undefiled test-tube (20 mL) and heated
−
1
at 80 °C for 5 h under autogenous pressure. Red block crystals were obtained. Yield:
2
4
8.5%. Anal. Calcd for C H CoN O : C, 58.81; H, 4.63; N, 12.86%. Found: C, 59.03; H,
32 30 6 6
.23; N, 12.98%. IR data (KBr pellet, ν/cm ): 3156 s, 1609 versus 1500 m, 1403 s, 1357
−1
s, 1216 w, 1073 w, 1027 w, 840 m, 787 m, 766 m, 696 m.
1
2
.3.2. Synthesis of [Ni(L ) (4,4′-bipy)(H O) ] (2). The synthesis of 2 was the same as
2
2
2 n
that of 1, except that Ni(NO ) ·6H O was used instead of CoCl ·6H O. Purple red block
3
2
2
2
2
crystals were obtained. Yield: 35.5%. Anal. Calcd for C H N NiO : C, 58.83; H, 4.63; N,
3
2
30
6
6
−
1
1
2.86%. Found: C, 58.94; H, 4.43; N, 13.12%. IR data (KBr pellet, ν/cm ): 3114 s, 1604
versus 1502 m, 1451 m, 1401 s, 1352 s, 1212 w, 1118 w, 1071 w, 1032 w, 838 m, 797 m,
7
69 m, 696 m.
1
2
.3.3. Synthesis of [Cu(L ) (4,4′-bipy)(H O) ] (3). The synthesis of 3 was similar to that
2 2 2 n
of 1, expect that CuCl ·5H O was used instead of CoCl ·6H O and the temperature of the
2
2
2
2
reaction mixture was 90 °C. Blue block crystals were obtained. Yield: 34.5%. Anal. Calcd
for C H CuN O : C, 58.40; H, 4.60; N, 12.77%. Found: C, 57.93; H, 4.83; N, 12.58%.
3
2
30
6 6
−1
IR data (KBr pellet, ν/cm ): 3442 s, 3120 s, 1614 versus 1501 m, 1400 versus 1339 s,
1
221 w, 1074 w, 1022 w, 986 w, 817 m, 764 m, 694 m.
2
2
0
.3.4. Synthesis of [Co(L ) (4,4′-bipy)(H O)] (4). A mixture of CoCl ·6H O (0.0238 g,
2
2
n
2
2
2
.1 mM), HL (0.0473 g, 0.2 mM), 4,4′-bipy (0.0156 g, 0.1 mM), NaOH (0.3 mL, 0.65 M
−
1
L ), and distilled water (10 mL) were sealed in a Teflon-lined stainless reactor (25 mL) and
heated at 90 °C for 72 h under autogenous pressure. Cooling to room temperature, the
remaining solution was filtered and evaporated slowly at room temperature. Red block crys-
tals were obtained. Yield: 35.5%. Anal. Calcd for C H Cl CoN O : C, 54.56; H, 3.69; N,
3
2
26
2
6 5
−
1
1
1.93%. Found: C, 54.85; H, 3.36; N, 12.35%. IR data (KBr pellet, ν/cm ): 3357 w, 3118
w, 1603 m, 1528 s, 1469 m, 1383 s, 1222 m, 1141 m, 1006 m, 809 m, 764 m.
2
2
.3.5. Synthesis of [Ni(L ) (4,4′-bipy)(H O)] (5). The synthesis of 5 was the same as
2
2
n
that of 4, except that 0.1 mM NiCl ·6H O was used instead of 0.1 mM CoCl ·6H O and
2
2
2
2
the temperature was increased to 120 °C. Green block crystals were obtained. Yield: 31.5%.
Anal. Calcd for C H Cl NiN O : C, 54.58; H, 3.69; N, 11.96%. Found: C, 54.92; H,
3
2
26
2
6 5
−
1
3
.32; N, 12.25%. IR data (KBr pellet, ν/cm ): 3371 w, 3129 w, 1601 m, 1536 s, 1468 m,
1
386 s, 1231 m, 1141 m, 1006 m, 764 m.

5
76
H. Liu et al.
2
2
5
.3.6. Synthesis of [Cu(L ) (4,4′-bipy)] (6). The synthesis of 6 was the same as that of
2
n
, except that CuSO ·5H O (0.1 mM, 0.027 g) was used instead of 0.1 mM NiCl ·6H O.
4
2
2
2
Blue columnar crystals were obtained. Yield: 37.5%. Anal. Calcd for C H Cl CuN O :
3
2
24
2
6 4
C, 55.62; H, 3.47; N, 12.16%. Found: C, 55.95; H, 3.25; N, 12.42%. IR data (KBr pellet,
−
1
ν/cm ): 3434 m, 2926 w, 1610 versus 1523 m, 1470 s, 1376 s, 1348 m, 1218 m, 1134 m,
1
004 w, 771 m.
2
.4. X-ray crystallographic study
X-ray single-crystal data of 1–6 were recorded on a Bruker APEX II area detector diffrac-
tometer with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å). Semi-empirical
absorption corrections were applied to 1–6 using SADABS [40]. The structures were solved
2
by direct methods [41] and refined by full-matrix least squares on F using SHELXL-97
[
42]. All non-hydrogen atoms were refined anisotropically. The carboxyl and water hydro-
gens were located from difference Fourier maps; the other hydrogens were placed in geo-
metrically calculated positions. Experimental details for X-ray data collection of 1–6 are
presented in table 1 and selected bond lengths are listed in table 2; the main hydrogen
bonding lengths and angles are listed in table 3.
2
.5. Antibacterial testing
1
2
The in vitro antibacterial activities of HL , HL , and 1–6 were tested against gram positive
bacteria, Staphylococcus aureus, Candida albicans and Bacillus subtilis, and Gram-negative
bacteria, Escherichia coli and Pseudomonas aeruginosa, by the minimum inhibitory
concentration (MIC) method. The compounds were dissolved in DMF with two-fold serial
−
1
dilutions from 200 to 6.25 μg mL . Sterile microtubes were filled with 1 mL of serial two-
fold dilutions of the compounds. A growth tube (broth plus inoculum) and a sterility control
tube (broth only) were included each time. The tubes were incubated at 37 °C for 24 h.
MICs were defined as the lowest concentrations of the compounds which inhibited the
growth of micro-organisms; DMF was inactive under the applied conditions.
3
3
3
. Results and discussion
.1. Description of the structures
1
.1.1. Crystal structure of [Co(L ) (4,4′-bipy)(H O) ] (1). Crystallographic analysis
2
2
2 n
1
revealed that 1–3 are isostructural. The asymmetric unit of 1 contains a half Co(II), one L ,
one water, and a half 4,4′-bipy. Co(II) in 1 coordinates to two carboxyl oxygens from two
L , two nitrogens from two 4,4′-bipy molecules, and another two oxygens from two waters
1
1
as shown in figure 1, displaying a distorted octahedral geometry. In 1, L is monodentate
(see scheme 2(a)), having two orientations with the dihedral angle of 21.90° between the
pyrazole rings in 1. The carboxylates are out of the planes of pyrazole rings with dihedral
1
angle of 63.29° and the phenyl and pyrazole rings of L ligands in 1 are twisted by an angle
of 46.25°. The 4,4′-bipy molecules are bis(monodentate) bridges, linking Co(II) ions into a

M(II) pyrazole carboxylates
577

5
78
H. Liu et al.
Table 2. Selected bond lengths (Å) for 1–6.
1
Co(1)–O(3)
Co(1)–O(2)
Co(1)–N(3)
2.083(13)
2.092(12)
2.170(2)
Co(1)–O(3)#1
Co(1)–O(2)#1
Co(1)–N(4)#2
2.083(13)
2.092(12)
2.200(2)
2
Ni(1)–O(3)
Ni(1)–O(2)
Ni(1)–N(3)
2.049(2)
2.051(2)
2.133(3)
Ni(1)–O(3)#1
Ni(1)–O(2)#1
Ni(1)–N(4)#2
2.049(2)
2.052(2)
2.107(3)
3
Cu(1)–O(2)#1
Cu(1)–O(2)
Cu(1)–N(3)
1.955(12)
1.955(12)
2.035(18)
Cu(1)–O(3)
Cu(1)–O(3)#1
Cu(1)–N(4)#2
2.418(14)
2.418(14)
2.049(18)
4
Co(1)–O(1)
Co(1)–O(3)
Co(1)–O(4)
2.079(14)
2.187(15)
2.128(15)
Co(1)–O(5)
Co(1)–N(5)
Co(1)–N(6)
2.103(16)
2.163(16)
2.155(17)
5
Ni(1)–O(1)
Ni(1)–O(3)
Ni(1)–O(4)
2.065(15)
2.116(16)
2.125(15)
Ni(1)–O(5)
Ni(1)–N(5)
Ni(1)–N(6)
2.069(17)
2.114(19)
2.092(18)
6
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(3)
2.769(15)
1.925(11)
2.018(2)
Cu(1)–O(1)#3
Cu(1)–O(2)#3
Cu(1)–N(4)#4
2.769(15)
1.925(11)
2.029(2)
Note: Symmetry operations: #1 −x + 2, y, −z + 1/2; #2 x, y + 1, z; #3 − x, −y, z; #4 x, y, −1 + z.
1-D chain (figure 2), and the dihedral angle between the pyridine rings is 50.17°. In 1, there
are abundant hydrogen bonds: (a) between coordinated water and carboxyl oxygen; (b)
between nitrogen of pyrazole and coordinated water; (c) between C–H of phenyl or pyridine
rings and carboxyl oxygen (table 3), which extend 1-D chains into a 3-D supramolecular
network consisting of left- and right-handed helical chains (figure 3); the pitch of the helix
is the same as the length of the b axis (11.30 Å).
1
3
.1.2. Crystal structure of [Cu(L ) (4,4′-bipy)(H O) ] (3). Although 1–3 are isostruc-
2
2
2 n
1
tural, the asymmetric unit of 3 is similar to 1 and 2, but L in 3 have different orientations
compared to those in 1 and 2. The dihedral angle between the pyrazole rings in 3 is 56.57°.
Carboxylates are out of the planes of pyrazole rings with dihedral angle of 37.86°, and the
1
phenyl and pyrazole rings of L in 3 are twisted by an angle of 51.75°. Each Cu(II) is
bridged by 4,4′-bipy with dihedral angle between pyridine rings of 52.66°, giving a 1-D
chain structure, and the 1-D chains are further extended into a 3-D supramolecular network
via O–H⋯N, O–H⋯O, and C–H⋯O hydrogen bonds, of which O3–H2⋯N2 and
C3–H3⋯O1 link Cu(II) ions forming left- and right-handed helical chains, and the pitch of
the helix is the same as the length of the b axis (11.15 Å), as shown in figure 4.

M(II) pyrazole carboxylates
579
Table 3. Hydrogen bonding geometry (Å and °) for 1–6.
D–H∙A
d(D–H)
d(H…A)
d(D…A)
∠(DHA)
1
O(3)–H(1W)∙∙∙O(1)
O(3)–H(2W)∙∙∙N(2)#1
C(3)–H(3)∙∙∙O(1)#2
C(7)–H(7)∙∙∙O(2)#3
C(10)–H(10)∙∙∙O(1)#4
C(12)–H(12)∙∙∙O(2)
C(17)–H(17)∙∙∙O(1)#5
0.82
0.79
0.93
0.93
0.93
0.93
0.93
2.01
2.01
2.59
2.50
2.50
2.44
2.58
2.750(19)
2.794(2)
3.445(2)
3.416(3)
3.339(3)
3.052(2)
3.401(2)
149.0
173.0
154.0
170.0
150.0
124.0
147.0
2
O(3)–H(2 W)∙∙∙O(1)
O(3)–H(1 W)∙∙∙N(2)#1
C(3)–H(3)∙∙∙O(1)#2
C(7)–H(7)∙∙∙O(2)#3
C(10)–H(10)∙∙∙O(1)#4
C(12)–H(12)∙∙∙O(1)
C(17)–H(17)∙∙∙O(2)#5
0.82
0.83
0.93
0.93
0.93
0.93
0.93
1.99
1.97
2.56
2.44
2.45
2.56
2.38
2.728(3)
2.795(3)
3.423(4)
3.362(4)
3.294(4)
3.368(4)
2.992(4)
149.0
174.0
154.0
170.0
150.0
146.0
123.0
3
O(3)–H(2 W)∙∙∙N(2)#1
C(3)–H(3)∙∙∙O(1)#2
C(12)–H(12)∙∙∙O(3)#3
O(3)–H(1 W)∙∙∙O(1)
0.85
0.93
0.93
0.82
2.12
2.58
2.45
2.10
2.942(2)
3.450(3)
3.140(2)
2.751(2)
164.0
155.0
131.0
136.0
4
O(5)–H(1 W)∙∙∙N(4)#1
O(5)–H(2 W)∙∙∙O(2)
C(17)–H(17)∙∙∙O(5)#1
C(21)–H(21B)∙∙∙O(3)
C(23)–H(23)∙∙∙Cl(1)
C(23)–H(23)∙∙∙O(1)
C(15)–H(15)∙∙∙π#2
0.83
0.83
0.93
0.96
0.93
0.93
0.93
2.07
1.72
2.55
2.60
2.61
2.35
2.85
2.880(3)
2.504(3)
3.217(4)
3.117(3)
3.436(3)
2.992(3)
3.575(5)
166.0
157.0
129.0
114.0
149.0
126.0
136.0
5
O(5)–H(1 W)∙∙∙N(4)#1
O(5)–H(2 W)∙∙∙O(2)
C(17)–H(17)∙∙∙O(5)#1
C(21)–H(21B)∙∙∙O(4)
C(23)–H(23)∙∙∙Cl(1)
C(23)–H(23)∙∙∙O(1)
C(15)–H(15)∙∙∙π#2
6
0.83
0.83
0.93
0.96
0.93
0.93
0.93
2.10
1.70
2.52
2.58
2.60
2.30
2.84
2.903(3)
2.502(4)
3.188(4)
3.113(4)
3.417(3)
2.937(3)
3.574(5)
163.0
161.0
129.0
115.0
146.0
125.0
136.0
C(12)–H(12)∙∙∙O(2)
C(16)–H(16)∙∙∙π#1
0.93
0.93
2.35
2.71
2.900(2)
3.536(2)
117.0
149.0
Note: Symmetry codes: for 1: #1 x + 1/2, −y + 1/2, z + 1/2; #2 −x + 2, −y + 1, −z; #3 −x + 3/2, −y + 1/2, −z; #4
x + 2, −y, −z; #5 x, y − 1, z; for 2: #1 x + 1/2, −y + 3/2, z + 1/2; #2 −x + 2, −y + 1, −z; #3 −x + 3/2, −y + 3/2, −z;
−
#
2
4 −x + 2, −y + 2, −z; #5 x, y − 1, z; for 3: #1 x + 1/2, −y + 1/2, z + 1/2; #2 −x + 2, −y + 1, −z; #3 −x + 2, y, −z + 1/
; for 4: #1 −x + 1, −y, −z + 1; #2 x, y − 1, z + 1; for 5: #1 −x + 1, −y + 1, −z; #2 x, y, z − 1; for 6: #1 x − 1/4,
−y + 1/4, z + 3/4.
2
3
.1.3. Crystal structure of [Co(L ) (4,4′-bipy)(H O)] (4). Crystallographic analysis
2 2 n
revealed that 4 and 5 are isostructural, so only the crystal structure of 4 is described here in
2
detail. The asymmetric unit of 4 contains one Co(II), two L , one 4,4′-bipy, and one water.
2
As shown in figure 5, in 4, Co(II) coordinates to three carboxylate oxygens from two L ,
one oxygen from a water, and another two nitrogens from two 4,4′-bipy molecules in a
2
distorted octahedral geometry. The L adopt two kinds of coordination modes in 4, one
monodentate and the other chelating–bidentate (see scheme 3(b) and (c)). For convenience,

5
80
H. Liu et al.
Figure 1. Coordination environment of Co(II) in 1 with 30% thermal ellipsoids.
1
2
Scheme 2. The coordination modes of HL and HL in 1–6.
Figure 2. 1-D chain structure of 1 with 30% thermal ellipsoids.
2
a
2b
the monodentate ligand is named as L and the chelating–bidentate ligand is named as L .
2
a
2b
The dihedral angle between the phenyl and pyrazole rings in L and L are 60.10° and
0.82°, respectively, and that between the pyrazole rings of L and L is 84.36°. In 4,
,4′-bipy is bis(monodentate) bridging with dihedral angle of 87.99° between pyridine
2
a
2b
5
4
rings, linking Co(II) ions into a 1-D zig-zag chain (figure 6). The 1-D chain structures are
further connected into a 3-D supramolecular network (figure 7) via hydrogen bonds and
C–H⋯π interactions (H⋯π distance is 2.85 Å and C–H⋯π angle is 136°).

M(II) pyrazole carboxylates
581
Figure 3. (a) View of helical chains with left-handed (green) and right-handed (orange) helices in 1 along the c
axis. (b) The 3-D supramolecular network of 1 along the b axis (see http://dx.doi.org/10.1080/00958972.2014.
896993 for color version).
Figure 4. (a) The 3-D supramolecular network of 3 along the b axis. (b) View of helical chains with left-handed
blue) helices. (c) Right-handed (green) helices in along the axis (see http://dx.doi.org/10.1080/
(
3
c
00958972.2014.896993 for color version).
2
3
.1.4. Crystal structure of [Cu(L ) (4,4′-bipy)] (6). The asymmetric unit in 6 consists
2 n
2
of a half copper(II), one L , and a half 4,4′-bipy. As shown in figure 8, the Cu(II) in 6 is
six-coordinate with four oxygens from two L and two nitrogens from two 4,4′-bipy mole-
2
cules. Cu(II) is coplanar with N3, N4B, O1, and O1A. Two pyridine nitrogens N3, N4B
and two carboxylate oxygens O2, O2A reside in equatorial positions with bond lengths
varying from 1.925(11) to 2.029(2) Å, while axial positions are occupied by O1 and O1A,
axial Cu–O bond lengths are 2.769(15) Å, and the axial bond angle is 156.47(44)°. Cu(II)
ions locate in an elongated octahedral environment because of the Jahn–Teller effect. Differ-
2
ent from 4, in 6, L only display chelating–bidentate mode; the phenyl and pyrazole rings

5
82
H. Liu et al.
Figure 5. Coordination environment of Co(II) in 4 with 30% thermal ellipsoids.
Figure 6. The 1-D zig-zag chain structure of 4 formed by 4,4′-bipy.
2
of L are twisted by an angle of 58.47°. 4,4′-Bipy in which pyridine rings are coplanar are
bis(monodentate) bridges, linking Cu(II) ions into a 1-D chain (figure 9), and the 1-D
chains are further stacked to a 3-D supramolecular network (figure 10) along the c axis via
2
C–H⋯π interactions between C–H groups of 4,4′-bipy and phenyl rings of L (H⋯π dis-
2
tance is 2.71 Å and C–H⋯π angle is 149°). The [Cu(L ) (4,4′-bipy)] monomers are joined
2
into a zig-zag chain through C(16)–H(16)⋯π interaction, as shown in figure 11.
3
.2. Comparison of the structures
1
2
2
The positions of carboxylate on the pyrazole ring for HL and HL are different, and HL
1
2
contains one more chlorine substituent. L and L display different coordination modes in
–6 (scheme 2), but the structures of corresponding complexes with L and L are very sim-
ilar. The coordination numbers of 1–6 all are six, and 1–3 with L and 4–6 with L all dis-
play 1-D structures connected by 4,4′-bipy. All are extended to 3-D supramolecular
networks via hydrogen bonding interactions, as shown in scheme 3. Complexes 1–3 with
1
2
1
1
2
1
2
L are helical chains, while helical chains are not observed in 4–6 with L , showing that the
position of carboxylate has an effect on formation of the helix.

M(II) pyrazole carboxylates
583
Figure 7. The 3-D supramolecular network of 4 along the a axis.
Figure 8. Coordination environment of Cu(II) in 6 with 30% thermal ellipsoids.
For the same ligand, 1–3 and 4 and 5 are isostructural because Co(II), Ni(II), and Cu(II)
1
ion radii are very close. In 1–3, L are monodentate with two orientations. The dihedral
angles between the planes of pyrazole ring are 21.90°, 22.50°, and 56.57° in 1–3, respec-
1
tively; the phenyl and pyrazole rings of L are twisted by an angle of 46.25°, 46.06°, and
5
1.75° in 1–3, respectively, and the dihedral angles between the pyrazole rings and the
2
carboxylates are 63.30°, 64.73°, and 37.86° in 1–3, respectively. L have two kinds of coor-
dination modes: monodentate and chelating–bidentate in 4 and 5, but only chelating–biden-
tate in 6. L have different orientations in 4–6. The dihedral angles between the planes of
2
pyrazole ring are 84.36°, 85.92°, and 64.92° in 4–6, respectively; the phenyl and pyrazole
rings of chelating–bidentate ligand are twisted by angles of 50.82°, 51.36°, and 58.47° in
4
–6, respectively, and that of monodentate ligand are twisted by angles of 60.10° and

5
84
H. Liu et al.
Figure 9. The 1-D chain structure of 6 with 30% thermal ellipsoids.
Figure 10. The 3-D supramolecular network of 6 along the c axis.
Figure 11. The zig-zag chain of 6 through C–H∙∙∙π interaction along the c axis.
60.76° in 4 and 5, respectively. Dihedral angles between the pyrazole rings and carboxyl-
ates of chelating–bidentate ligands are 17.25°, 17.18°, and 13.86° in 4–6, respectively, and
that of monodentate ligand are 9.35° and 8.65° in 4 and 5, respectively. 4,4′-Bipy molecules
have different orientations in 1–6 with dihedral angles between pyridine rings of 50.17°,
5
1.64°, 52.66°, 87.99°, and 89.55° in 1–5, respectively, and in 6, pyridine rings are copla-
nar. In 4 and 5, waters coordinate, however, there are no water molecules in 6, showing that
hydrogen bonding interactions between coordinated water and C–H groups of phenyl rings
have a significant effect on the structures of 4 and 5; metal ions can affect the coordination
2
of L .

M(II) pyrazole carboxylates
585
Scheme 3. Schematic procedure and dimensional relationship of metal ions and ligands of 1–6.
Recently, some coordination polymers based on nitrogen-heterocyclic carboxylate with
helical structures have been reported. For example, [Zn (μ -HBuPhIDC) (CH OH) ]
2
3
2
3
2
(
μ3-HBuPhIDC = 2-(p-tert-butylphenyl)-1H-imidazole-4,5-dicarboxylic acid) displays an
interesting 3-D open architecture, which contains infinite 1-D octagonal channels built by
left- and right-handed helical chains [43]. [Co(L) (H O) ] ⋅2nH O and [Ni(L) (H O) ]
2 n
2
2
2 n
2
2
2
⋅
2nH O (HL = 2-(6-oxo-6H-purin-1(9H)-yl)acetic acid) show a 2-D structure composed of
2
left- and right-handed metal-organic helices sharing common metal centers [44] with all of
the helical chains formed via coordination bonds. However, 1–3 exhibit 1-D structures and
the helical chains formed via coordination bonds as well as hydrogen bonds.
3
.3. Antibacterial activity results
1
2
The antibacterial activities of HL , HL , and 1–6 have been measured against selected
micro-organisms. From the results given in table 4, ligands show antibacterial activities
against the Gram-positive bacteria S. aureus, C. albicans, and B. subtilis, and Gram-nega-
−
1
tive bacteria E. coli and P. aeruginosa I, with MIC values between 25 and 100 μg mL ,
−
1
while MIC values of the complexes are between 6.25 and 25 μg mL . The MIC values of
1
2
−1
Table 4. MIC values of HL , HL , and 1–6 against the tested bacteria (μg mL ).
Compounds
S. aureus
C. albicans
B. subtilis
E. coli
P. aeruginosa
1
HL
HL
50
25
50
25
100
50
100
25
50
25
2
4
1
2
3
4
5
6
,4′-bipy
25
25
25
25
12.5
12.5
12.5
50
50
25
100
25
25
25
25
50
25
25
25
12.5
12.5
6.25
12.5
12.5
25
12.5
6.25
25
12.5
12.5
25
6.25
6.25
25
12.5

5
86
H. Liu et al.
1
2
1
–6 are lower than that of HL and HL , indicating that the antibacterial activities of metal
complexes are better than those of corresponding free ligands against the tested bacteria.
2
For S. aureus and P. aeruginosa, 4–6 with L show better antibacterial activities than 1–3
1
with L , while for the other bacteria, 4–6 show the same antibacterial activities as 1–3, and
some show better antibacterial activities than 1–3.
4
. Conclusion
Six new transition metal coordination polymers with two kinds of phenyl substituted pyra-
zole carboxylic acids have been obtained and characterized. Complexes 1–6 all display 1-D
structures connected by 4,4′-bipy, and all extended to 3-D supramolecular networks via
hydrogen bonding interactions and other weak intermolecular interactions. Complexes 1–3
comprise single-stranded helices, while 4–6 contain zig-zag chains. Single-crystal X-ray dif-
fraction results show that variation of the carboxylate group position lead to different struc-
tures of complexes. Metal ions, hydrogen bonds, bridging conformations of carboxylates,
and N-donor co-ligands have significant influence on the helical structures of 1–6. Antibac-
terial measurements show that the inhibitory effect of the complexes is stronger than those
of corresponding free ligands.
Supplementary material
CCDC 933049-933054 contain the supplementary crystallographic data for 1–6. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK;
Fax: (+44)1223-336-033; or E-mail: deposit@ccdc.cam.ac.uk.
Funding
This work was supported by the Natural Science Foundation of China [grant number 21264011],
[
grant number 20961007]; the Aviation Fund [grant number 2010ZF56023] and the Young
Scientists Program of Jiangxi Province [grant number 2008DQ00600].
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