Self-assembly and structures of new transition metal complexes with phenyl substituted pyrazole carboxylic acid and N-donor co-ligands

Article abstract of DOI:10.1016/j.ica.2011.11.015

Five new transition metal complexes, [Ni(HL¹) ₂(2,2′-bipy)]·3H₂O (1), [Ni(HL ¹)₂(4,4′-bipy)] (2), [Co(HL¹) ₂(4,4′-bipy)]·5H₂O (3), [Ni ₂(HL²)₄·(4,4′-bipy)·(H ₂O)₂]·4H₂O (4), [Co(HL²) ₂·(4,4′-bipy)] (5) (H₂L¹ = 5-phenyl-1H-pyrazole-3-carboxylic acid; H₂L² = 3-phenyl-1H-pyrazole-4-carboxylic acid; 2,2′-bipy = 2,2′-bipyridine; 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized. Complex 1 exhibits a monomeric structure, 2 and 3 display 1D chain structures, 4 and 5 possess 3D metal-organic frameworks with 1D channels, and all extend to 3D supramolecular networks via rich hydrogen bonds. Complex 4 shows a new (4,6)-connected network with (4⁴·5 ⁸·6³)(5⁴·6·8) topology, while 5 exhibits a NaCl-like network with (4¹²·6³) topology. The thermal stabilities of complexes 1-5 and powder XRD of 4 and 5 were investigated. Furthermore, the antibacterial activities of the title complexes against the tested bacteria were studied and compared to the activities of the corresponding free ligands.

Full text of DOI:10.1016/j.ica.2011.11.015

Inorganica Chimica Acta 383 (2012) 277–286
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Self-assembly and structures of new transition metal complexes with phenyl
substituted pyrazole carboxylic acid and N-donor co-ligands
a
a
b
Chong-Bo Liu a, , Yun-Nan Gong , Yuan Chen , Hui-Liang Wen
⇑
a School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang, Jiangxi 330063, China
b State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi 330047, China
a r t i c l e i n f o
a b s t r a c t
Five new transition metal complexes, [Ni(HL1)2(2,20-bipy)]ꢀ3H2O (1), [Ni(HL1)2(4,40-bipy)] (2), [Co(HL1)2
(4,40-bipy)]ꢀ5H2O (3), [Ni2(HL2)4ꢀ(4,40-bipy)ꢀ(H2O)2]ꢀ4H2O (4), [Co(HL2)2ꢀ(4,40-bipy)] (5) (H2L1 = 5-phenyl-
1H-pyrazole-3-carboxylic acid; H2L2 = 3-phenyl-1H-pyrazole-4-carboxylic acid; 2,20-bipy = 2,20-bipyri-
dine; 4,40-bipy = 4,40-bipyridine) have been synthesized and characterized. Complex 1 exhibits a mono-
meric structure, 2 and 3 display 1D chain structures, 4 and 5 possess 3D metal-organic frameworks with
1D channels, and all extend to 3D supramolecular networks via rich hydrogen bonds. Complex 4 shows a
new (4,6)-connected network with (44ꢀ58ꢀ63)(54ꢀ6ꢀ8) topology, while 5 exhibits a NaCl-like network with
(412ꢀ63) topology. The thermal stabilities of complexes 1–5 and powder XRD of 4 and 5 were investigated.
Furthermore, the antibacterial activities of the title complexes against the tested bacteria were studied and
compared to the activities of the corresponding free ligands.
Article history:
Received 18 July 2011
Received in revised form 11 October 2011
Accepted 8 November 2011
Available online 27 November 2011
Keywords:
Pyrazole carboxylic acid
N-donor co-ligands
Transition metal complexes
Channels
Ó 2011 Elsevier B.V. All rights reserved.
Homohelix chain
Properties
1. Introduction
3-phenyl-1H-pyrazole-4-carboxylic acid (H2L2) [27–30], to investi-
gate the influence of different positions of carboxylate groups on
In recent years, considerable research efforts have been directed
towards the design and synthesis of metal–organic complexes not
only because of their fascinating structural diversities, but also
due to their potential applications in ion exchange, biological activ-
ities, magnetic and porous materials [1–7]. In general, the structures
of the complexes depend on the combination of several factors,
including metal ions, organic ligands, pH value, reaction tempera-
ture, etc. [8–11]. So, proper selection of metal ions and organic
ligands is a key issue in designing and self-assembly of new
metal–organic complexes.
Especially, multidentate carboxylate ligands with N- and O-do-
nors have received much more attention due to their high access
to metals, to form 3d, 4f or 3d–4f metal–organic complexes, and pyr-
azole carboxylic acid compound is a good example of N- and O-do-
nors ligands and regarded as one kind of elegant ligands [12–17].
Whereas, very few complexes of pyrazole carboxylic acids except
3,5-pyrazoledicarboxylic acid have been reported [18–24]. One phe-
nyl group is introduced to pyrazole carboxylic acid, which increases
the structures. On the other hand, metal ions due to their different
radii and coordination geometry, and auxiliary ligands due to their
different sizes and coordination modes, often have significant effect
on the formation and the structures of complexes [31–33]. In partic-
ular, 4,40-bipy as linear bridging auxiliary ligand is often used to con-
struct high-dimensional porous metal–organic frameworks [34,35].
Herein we report the syntheses and the structures of five new tran-
sition metal complexes with H2L1 and H2L2, and N-donor co-ligands:
[Ni(HL1)2(2,20-bipy)]ꢀ3H2O (1), [Ni(HL1)2(4,40-bipy)] (2), [Co(HL1)2
(4,40-bipy)]ꢀ5H2O (3), [Ni2(HL2)4ꢀ(4,40-bipy)ꢀ(H2O)2]ꢀ4H2O (4), [Co
(HL2)2ꢀ(4,40-bipy)] (5).
2. Experimental
2.1. Materials and measurements
5-Phenyl-1H-pyrazole-3-carboxylic acid (H2L1) and 3-phenyl-
1H-pyrazole-4-carboxylic acid (H2L2) were prepared according to
literature method [27–30]. All other reagents were commercially
available and used without further purification. Elemental analysis
of C, H and N were carried out with an Elementar Vario EL analyzer.
Infrared spectra were recorded with a Nicolet Avatar 360 FT-IR spec-
trometer using the KBr pellet technique. H NMR spectra were
recorded at 400 MHz on a Bruker WH400 DS spectrometer. Thermal
stability studies were carried out on a ZRY-2P Thermal Analyzer.
the possibility of
p
–
p
and C–Hꢀ ꢀ ꢀ
p interactions, and help to
construct high-dimensional supramolecular structures [25,26]. In
this paper, we synthesized two kinds of phenyl substituted pyrazole
carboxylic acid: 5-phenyl-1H-pyrazole-3-carboxylic acid (H2L1) and
⇑
Corresponding author. Tel./fax: +86 791 6453231.
E-mail address: cbliu@nchu.edu.cn (C.-B. Liu).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.11.015

278
C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
X-ray powder diffraction patterns were recorded on D8 ADVANCE
X-ray diffractometer.
nous pressure. Green block crystals were obtained. Yield: 36.5%.
Anal. Calc. for C50H48N10Ni2O14: C, 53.12; H, 4.37; N, 12.39. Found:
C, 53.49; H, 4.12; N, 12.55%. IR data (KBr pellet, m
/cmꢁ1): 3147 m,
2.2. Synthesis of [Ni(HL1)2(2,20-bipy)]ꢀ3H2O (1)
1607 m, 1537 m, 1490 m, 1402 m, 1327 s, 1220 w, 959 m, 915
w, 810 m, 758 w, 693 m.
A mixture of NiCl2ꢀ6H2O (0.024 g, 0.1 mmol), H2L1 (0.019 g,
0.1 mmol), 2,20-bipyridine (0.016 g, 0.1 mmol), NaOH (0.15 mL,
0.65 M) and distilled water (10 mL) was sealed in a Teflon-lined
stainless reactor (23 mL) and heated 120 °C for 72 h under autoge-
nous pressure. Blue block crystals were obtained. Yield: 43.5%.
Anal. Calc. for C30H28NiN6O7: C, 56.01; H, 4.35; N, 13.07. Found:
2.6. Synthesis of [Co(HL2)2ꢀ(4,40-bipy)] (5)
The synthesis of 5 was similar with that of 4, only that 0.1 mmol
CoCl2ꢀ6H2O was used instead of 0.1 mmol NiCl2ꢀ6H2O. Red block
crystals were obtained. Yield: 58.5%. Anal. Calc. for C30H22N6CoO4:
C, 61.12; H, 3.76; N, 14.26. Found: C, 61.45; H, 3.52; N, 14.03%. IR
C, 56.46; H, 4.18; N, 13.55%. IR data (KBr pellet, m
/cmꢁ1): 3409 s,
1602 s, 1495 m, 1413 s, 1337 s, 1207 w, 1023 m, 957 w, 918 w,
829 m, 761 m.
data (KBr pellet, m
/cmꢁ1): 1615 m, 1545 s, 1488 m, 1433 m, 1334
s, 1275 w, 1083 m, 957 s, 899 m, 805 m, 768 w, 701w.
2.3. Synthesis of [Ni(HL1)2(4,40-bipy)] (2)
2.7. X-ray crystallographic study
The synthesis of 2 was similar with that of 1, only that 0.1 mmol
4,40-bipyridine was used instead of 0.1 mmol 2,20-bipyridine,
NaOH aqueous solution was reduced to 0.1 mL and the tempera-
ture of the reaction mixture was 150 °C. Blue block crystals were
obtained. Yield: 54.5%. Anal. Calc. for C30H22NiN6O4: C, 61.15; H,
3.76; N, 14.27. Found: C, 61.33; H, 3.55; N, 14.55%. IR data (KBr
The X-ray single-crystal data of complexes 1–5 were recorded on
a Brucker APEX II area detector diffractometer with a graphite-
monochromated Mo Ka radiation (k = 0.71073 Å). Semi-empirical
absorption corrections were applied to the title complexes using
the SADABS program [36]. The structures were solved by direct meth-
ods [37] and refined by full-matrix least squares on F2 using SHELXL-97
[38]. All non-hydrogen atoms were refined antisotropically.
Hydrogen atoms were placed in geometrically calculated positions.
Experimental details for X-ray data collection of 1–5 are presented
in Table 1, selected bond lengths are listed in Table 2, and the types
of hydrogen bonds are listed in Table 3.
pellet, m
/cmꢁ1): 1634 s, 1583 s, 1488 m, 1414 s, 1339 s, 1297 s,
1209 m, 1097 m, 942 w, 807 m, 663 w.
2.4. Synthesis of [Co(HL1)2(4,40-bipy)]ꢀ5H2O (3)
The synthesis of 3 was similar with that of 2, only that 0.1 mmol
CoCl2ꢀ6H2O was used instead of 0.1 mmol NiCl2ꢀ6H2O and the tem-
perature of the reaction mixture was 90 °C. Red block crystals were
obtained. Yield: 42.3%. Anal. Calc. for C30H32CoN6O9: C, 53.02; H,
4.75; N, 12.37. Found: C, 53.25; H, 4.52; N, 12.65%. IR data (KBr pel-
2.8. Antibacterial testing
The in vitro antibacterial activities of H2L1 and H2L2, and com-
plexes 1–5 were tested against Gram positive bacteria: Staphylo-
coccus aureus, Canidia albicans and Bacillus subtilis, and Gram
negative bacteria: Escherichia coli and Pseudomonas aeruginosa by
minimum inhibitory concentration (MIC) method. The compounds
were dissolved in DMF with twofold serial dilutions from 200 to
let, m
/cmꢁ1): 3134 m, 1608 s, 1495 m, 1413 s, 1337 m, 1208 m,
1073 m, 974 w, 889 w, 824 m, 761 m, 685 m.
2.5. Synthesis of [Ni2(HL2)4ꢀ(4,40-bipy)ꢀ(H2O)2]ꢀ4H2O (4)
A mixture of NiCl2ꢀ6H2O (0.024 g, 0.1 mmol), H2L2 (0.019 g,
0.1 mmol), 4,40-bipyridine (0.016 g, 0.1 mmol), NaOH (0.15 mL,
0.65 M) and distilled water (10 mL) was sealed in a Teflon-lined
stainless reactor (23 mL) and heated 120 °C for 72 h under autoge-
6.25 lg/mL. Sterile micro tubes were filled with 1 mL of serial two-
fold dilutions of compounds. A growth tube (broth plus inoculum)
and a sterility control tube (broth only) were included in each time.
The tubes were incubated at 37 °C for 24 h. MICs were defined as
Table 1
Crystal data for complexes 1–5.
Complex
1
2
3
4
5
Empirical formula
Formula weight
T (K)
C
30H28NiN6O7
C30H22NiN6O4
589.25
296(2)
C30H32CoN6O9
679.55
296(2)
C50H48Ni2N10O14
1130.41
296(2)
C30H22CoN6O4
589.47
296(2)
643.29
296(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
rhombohedral
R3c
27.013(8)
27.013(8)
21.432(7)
90
monoclinic
Cc
tetragonal
P4322
11.4214(5)
11.4214(5)
24.2401(11)
90
monoclinic
I2/a
12.6652(9)
11.4083(8)
34.571(3)
90
monoclinic
C2/c
24.038(3)
12.7537(16)
11.8640(15)
90
ꢀ
14.483(4)
17.050(5)
13.026(4)
90
a
(°)
b (°)
90
120
13544(7)
18
121.296(3)
90
2748.7(14)
4
90
90
3162.1(2)
4
97.5210(10)
90
4952.2(6)
4
110.073(2)
90
3416.3(7)
4
c
(°)
V (Å3)
Z
F(000)
6012
1.420
2.49–25.50
0.701
1216
1.424
2.39–27.50
0.753
1412
1.427
2.45–25.50
0.605
2344
1.516
2.41–27.50
0.840
1212
1.146
2.36–25.50
0.541
Dcalc (mg mꢁ3
h range (°)
)
l
(mmꢁ1
)
GOF
Reflections/collected
Unique (Rint
R1, wR2 [I > 2
R1, wR2 (all data)
2.373
34149/2813
0.0568
0.0399, 0.0476
0.0617, 0.0491
1.392
11751/5819
0.0404
0.0460, 0.0942
0.0503, 0.0957
1.036
24585/2953
0.0363
0.0433, 0.1141
0.0510, 0.1214
1.014
21392/5657
0.0319
0.0420, 0.0897
0.0594, 0.1005
1.078
13039/3186
0.0498
0.0452, 0.1296
0.0547, 0.1354
)
r(I)]

C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
279
Table 2
Selected bond lengths (Å) for complexes 1–5.
1
Ni(1)–O(1)
Ni(1)–N(1)
Ni(1)–N(3)
2.0656(14)
2.0867(17)
2.0595(18)
Ni(1)–O(1)#1
Ni(1)–N(1)#1
Ni(1)–N(3)#1
2.0657(14)
2.0867(17)
2.0594(18)
Symmetry operation: #1 x + 2/3, y ꢁ 2/3, ꢁz + 13/6
2
Ni(1)–O(2)
Ni(1)–N(2)
Ni(1)–N(5)
2.058(2)
2.095(3)
2.050(3)
Ni(1)–O(3)
Ni(1)–N(4)
Ni(1)–N(6)#1
2.109(2)
2.114(3)
2.069(3)
Symmetry operation: #1 x + 1/2, y + 1/2, z
3
Co(1)–O(1)
Co(1)–N(1)
Co(1)–N(3)
2.059(3)
2.113(3)
2.178(4)
Co(1)–O(1)#1
Co(1)–N(1)#1
Co(1)–N(4)#2
2.059(3)
2.113(3)
2.161(3)
Symmetry operations: #1 ꢁx + 1, y, ꢁz; #2 x, y + 1, z
4
Ni(1)–O(1)
Ni(1)–O(5)
Ni(1)–N(3)
Ni(2)–O(4)#3
Ni(2)–N(1)
Ni(2)–N(6)
2.0392(18)
Ni(1)–O(1)#1
Ni(1)–O(5)#1
Ni(1)–N(4)#2
Ni(2)–O(4)#4
Ni(2)–N(1)#5
Ni(2)–N(6)#5
2.0391(18)
2.102(2)
2.159(3)
2.0943(18)
2.123(2)
2.067(2)
2.102(2)
2.133(3)
2.0944(18)
2.123(2)
2.067(2)
Symmetry operations: #1 ꢁx + 1/2, y, ꢁz + 1; #2 x, y + 1, z; #3 x + 1/2, ꢁy + 1, z; #4 ꢁx, yꢁ1/2, ꢁz + 1/2; #5 ꢁx + 1/2, ꢁy + 1/2, ꢁz + 1/2
5
Co(1)–O(1)#1
Co(1)–N(1)
Co(1)–N(3)
2.1444(15)
2.111(2)
2.195(2)
Co(1)–O(1)#2
Co(1)–N(1)#3
Co(1)–N(3)#3
2.1444(15)
2.111(2)
2.195(2)
Symmetry operations: #1 ꢁx + 1/2, y + 1/2, ꢁz + 3/2; #2 x, ꢁy, z + 1/2; #3 ꢁx + 1/2, ꢁy + 1/2, ꢁz + 2
the lowest concentrations of compounds which inhibit the growth
of microorganisms, DMF was inactive under applied conditions.
respectively. Furthermore, 4,40-bipy molecules act as bridging
ligand linking the Ni(II) ions into 1D chain (Fig. 4a). In 2, there
are rich N–Hꢀ ꢀ ꢀO hydrogen bonds between N–H of pyrazole rings
and carboxylate oxygen atoms, and C–Hꢀ ꢀ ꢀO hydrogen bonds be-
tween
3. Results and discussion
C–H of pyridine rings and carboxylate oxygen atoms (Table 3),
which extend 1D chains into a 3D supramolecular network with
rhombus channels (ca. 11.19 ꢂ 11.19 Å2) along the c axis (Fig. 4b).
3.1. Crystal structure of [Ni(HL1)2(2,20-bipy)]ꢀ3H2O (1)
Single crystal X-ray diffraction analysis reveals that the asym-
metric unit of complex 1 contains one Ni(II) ion, two HL1 ligands,
one 2,20-bipy and three lattice water molecules. Each Ni(II) ion in
complex 1 lies on an inversion center and coordinates to six atoms:
two carboxylate oxygen atoms and two nitrogen atoms from two
HL1 ligands, another two nitrogen atoms from one 2,20-bipy mole-
cule, as shown in Fig. 1. In 1, HL1 and 2,20-bipy ligands adopt N,O-
chelating and N,N-chelating modes to coordinate to Ni(II) ion (as
shown in Scheme 1a), respectively, and the phenyl and pyrazole
rings of HL1 ligands are twisted by an angle of 5.1°. In 1, there exist
abundant hydrogen bonds: (a) between lattice water molecules
and carboxylate oxygen atoms; (b) between N–H of pyrazole rings
and lattice water molecules; (c) between C–H of phenyl or pyridine
rings and lattice water molecules (Table 3). Each monomeric entity
of complex 1 is linked with neighbors via O–Hꢀ ꢀ ꢀO hydrogen bonds
to give rise to 1D zig-zag chain along the c axis (Fig. 2a), which ex-
tend to a 3D supramolecular network via N–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀO
hydrogen bonds (Fig. 2b).
3.3. Crystal structure of [Co(HL1)2(4,40-bipy)]ꢀ5H2O (3)
Complex 3 crystallize in chiral space group P4322, as a new
example of homochiral crystallization of helical coordination poly-
mers. In complex 3, Co(II) ion is coordinated by four nitrogen
atoms from two HL1 ligands and two 4,40-bipy molecules, different
from 2, leaving two trans-positions for two carboxylate oxygen
atoms of two HL1 ligands (Fig. 5). In 3 HL1 ligands only have one
orientation, and the phenyl and pyrazole rings are almost coplanar
with the dihedral angle of 1.9°. In 3, each HL1 ligand chelates one
Co(II) ion, and each 4,40-bipy molecule bridges two Co(II) ions,
which lead to 1D chains, furthermore, O–Hꢀ ꢀ ꢀO hydrogen bonds
between carboxylate oxygen atoms and lattice water molecules
and N–Hꢀ ꢀ ꢀO hydrogen bonds between N–H of pyrazole rings and
lattice water molecules join the chains to a 3D supramolecular net-
work, as shown in Fig. 6a. An interesting feature of complex 3 is its
double-stranded homohelical chain structure, the repeating unit of
which can be described as – (O4. . .HL1)–4n, and the pitch of the he-
lix running along the c-axis is the same as its length (24.24 Å), two
antiparallel helical chains with the same chirality interwine to
form a left-handed double helix, as shown in Fig. 6b.
3.2. Crystal structure of [Ni(HL1)2(4,40-bipy)] (2)
As shown in Fig. 3, each Ni(II) ion in complex 2 coordinates to
six atoms: four nitrogen atoms from two HL1 ligands and two
4,40-bipy molecules, leaving two cis-positions for two carboxylate
oxygen atoms of two HL1 ligands. Similar to 1, HL1 ligands also
adopt N,O-chelating mode coordinating to Ni(II) ion in 2. However,
there are two orientations of HL1 ligands in 2 with the dihedral
angles between phenyl and pyrazole rings of 9.3° and 22.3°,
3.4. Crystal structure of [Ni2(HL2)4ꢀ(4,40-bipy)ꢀ(H2O)2]ꢀ4H2O (4)
Single crystal X-ray diffraction shows that complex 4 contains
two crystallographically independent Ni(II) centers. As shown in
Fig. 7, Ni1 is not located at a symmetry center and coordinates to

280
C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
Table 3
Hydrogen bonding geometry (Å and °) for complexes 1–5.
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
\DHA
1
O(3)–H(1W)ꢀ ꢀ ꢀO(2)#1
O(3)–H(2W)ꢀ ꢀ ꢀO(2)#2
O(4)–H(3W)ꢀ ꢀ ꢀO(1)#3
N(2)–H(2)ꢀ ꢀ ꢀO(3)#4
C(10)–H(10)ꢀ ꢀ ꢀO(3)#4
C(14)–H(14)ꢀ ꢀ ꢀO(4)#5
C(14)–H(14)ꢀ ꢀ ꢀO(4)#6
0.84
0.84
0.83
0.87
0.93
0.93
0.93
1.95
1.95
1.96
1.89
2.34
2.35
2.35
2.779(2)
2.756(2)
2.771(18)
2.751(2)
3.243(4)
3.282(3)
3.282(3)
172.9
160.8
166.7
173.3
165.0
178.0
178.0
Symmetry operations: #1 ꢁx + 2/3, ꢁy + 4/3, ꢁz + 4/3; #2 x + 1, y, z ꢁ 1; #3 x, y, z ꢁ 1; #4 ꢁx + y + 1/3, ꢁx + 5/3, z + 2/3; #5 ꢁx + y + 1/3, yꢁ1/3, ꢁz + 4/3; #6 ꢁx + y + 1/3,
y + 1/3, z + 5/6
2
N(1)–H(1)ꢀ ꢀ ꢀO(4)#1
0.86
0.86
0.93
0.93
0.93
0.93
2.02
1.94
2.54
2.47
2.54
2.47
2.854(4)
2.755(5)
3.461(5)
3.271(4)
3.434(4)
3.047(5)
163.6
156.9
173.0
144.0
162.0
120.0
N(3)–H(3A)ꢀ ꢀ ꢀO(4)#1
C(24)–H(24)ꢀ ꢀ ꢀO(2)#1
C(25)–H(25)ꢀ ꢀ ꢀO(3)#1
C(29)–H(29)ꢀ ꢀ ꢀO(2)#1
C(30)–H(30)ꢀ ꢀ ꢀO(1)#1
Symmetry operation: #1 x, ꢁy, z + 1/2
3
O(3)–H(1W)ꢀ ꢀ ꢀO(1)#1
O(3)–H(2W)ꢀ ꢀ ꢀO(4)#2
O(4)–H(3W)ꢀ ꢀ ꢀO(5)#3
O(4)–H(4W)ꢀ ꢀ ꢀO(2)#1
O(4)–H(4W)ꢀ ꢀ ꢀO(2)#4
O(5)–H(5W)ꢀ ꢀ ꢀO(2)#5
N(2)–H(3)ꢀ ꢀ ꢀO(3)#3
N(2)–H(3)ꢀ ꢀ ꢀO(4)#6
0.84
0.83
0.87
0.90
0.90
0.80
0.86
0.86
2.16
1.56
2.57
2.39
2.46
2.54
1.93
2.52
2.902(7)
2.379(13)
3.235(17)
3.000(8)
3.223(11)
3.050(10)
2.677(7)
3.226(10)
147.7
164.6
133.7
124.7
142.4
123.1
145.1
140.3
Symmetry operations: #1 x, y, z + 1; #2 ꢁx + 1, ꢁy + 1, ꢁz + 7/4; #3 ꢁx + 1, y, ꢁz + 1; #4 ꢁx, y, ꢁz + 1; #5 ꢁx + 1, y, z + 1/4; #6 ꢁx + 1, y, z ꢁ 3/4
4
O(5)–H(1W)ꢀ ꢀ ꢀO(6)
O(5)–H(2W)ꢀ ꢀ ꢀO(2)
O(6)–H(3W)ꢀ ꢀ ꢀO(7)#1
O(7)–H(6W)ꢀ ꢀ ꢀO(2)
O(7)–H(5W)ꢀ ꢀ ꢀO(3)#2
N(2)–H(2A)ꢀ ꢀ ꢀO(4)#3
N(5)–H(5A)ꢀ ꢀ ꢀO(3)#3
0.83
0.83
0.83
0.84
0.84
0.86
0.86
1.96
1.93
2.32
2.04
2.30
2.21
1.96
2.772(3)
2.721(3)
2.855(4)
2.770(4)
2.887(3)
2.746(3)
2.728(3)
166.5
160.6
123.1
145.3
127.8
120.0
148.1
Symmetry operations: #1 ꢁx + 1, ꢁy + 1, ꢁz + 1; #2 x + 1/2, ꢁy + 1, z; #3 ꢁx, y ꢁ 1/2, ꢁz + 1/2
5
N(2)–H(2D)ꢀ ꢀ ꢀO(2)#1
0.86
0.93
1.91
2.41
2.679(3)
2.981(4)
148.8
120.0
C(11)–H(11)ꢀ ꢀ ꢀO(1)#2
Symmetry operations: #1 ꢁx + 1/2, y + 1/2, ꢁz + 3/2; #2 x, ꢁy, z + 1/2
O
M
(b)
(a)
C
O
O
C
Ph
Ph
HN
N
O
HN
N
M
M
Scheme 1. The coordination modes of H2L1 (a) and H2L2 (b) ligands in the title
complexes.
Fig. 1. The coordination environment of Ni(II) ion in complex 1 with 30% thermal
ellipsoids. All hydrogen atoms are omitted for clarity (symmetry operation: A: x + 2/
3, y ꢁ 2/3, ꢁz + 13/6).
between phenyl and pyrazole rings of 11.4° and 49.3°, respectively.
HL2 and 4,40-bipy ligands link the Ni(II) ions into a 3D metal–or-
ganic framework with 1D channels (ca. 6.17 ꢂ 8.27 Å2) along the
a axis (Fig. 8a). Moreover, the lattice water molecules are trapped
in the channels through O–Hꢀ ꢀ ꢀO hydrogen bonds between carbox-
ylate oxygen atoms and water molecules (Table 3).
In 4, a better insight into the 3D framework can be achieved by
application of a topological approach, each Ni1 links two HL2
ligands and two 4,40-bipy molecules, which can be viewed as a
four-connected node, and each Ni2 links six HL2 ligands, which
six atoms: four oxygen atoms from two HL2 ligands and two water
molecules, and two nitrogen atoms from two 4,40-bipy molecules.
However, Ni2 is located at a symmetry center and surrounded by
two oxygen atoms and four nitrogen atoms from six HL2 ligands.
In 4, HL2 ligands adopt bis(monodentate) bridging mode (as shown
in Scheme 1b), and have two orientations with the dihedral angles

C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
281
Fig. 2. (a) View of 1D zig-zag chain of complex 1 along the c axis; (b) The 3D supramolecular network of 1 along the c axis, the phenyl rings of HL1 ligands are omitted for
clarity.
3.5. Crystal structure of [Co(HL2)2ꢀ(4,40-bipy)] (5)
The Co(II) ion in complex 5 lies on an inversion center, displaying
a distorted octahedral geometry, coordinating to two carboxylate
oxygen and two nitrogen atoms from two HL2 ligands, another
two nitrogen atoms from two 4,40-bipy molecules, as shown in
Fig. 9. In 5, HL2 ligands adopt the same coordination mode as it in
4, while there is only one orientation of HL2 ligand with the dihedral
angle between phenyl and pyrazoe rings of 52.4°. In 5, HL2 ligands
link the Co(II) ions into a 2D layer structure, and 4,40-bipy molecules
further link these 2D layers to a 3D metal–organic framework with
1D channels along the b axis, the size of the channel is about
11.43 ꢂ 8.71 Å2 based on the distance between adjacent Co atoms
(Fig. 10a).
Topologically, each Co(II) ion links four HL2 ligands and two
4,40-bipy molecules, which can be viewed as a six-connected node,
so the overall structure can be simplified to a six-connected NaCl-
like network with (412ꢀ63) topology (Fig. 10b).
Fig. 3. The coordination environment of Ni(II) ion in complex 2 with 30% thermal
ellipsoids. All hydrogen atoms are omitted for clarity (symmetry operation: A: x + 1/2,
3.6. Effect of the reaction system on structural diversity
y + 1/2, z).
3.6.1. The position of carboxylate group on the pyrazole ring
In complexes 1–3, every H2L1 ligand only joins one metal ion,
and in complexes 4 and 5, every H2L2 ligand links two metal ions;
can be viewed as a six-connected node, so the overall structure can
be simplified to an unusual (4,6)-connected network with
(44ꢀ58ꢀ63)(54ꢀ6ꢀ8) topology, as shown in Fig. 8b. To the best of our
knowledge, such a (4,6)-connected network of complex 4 is first
reported, which is different from other typical (4,6)-connected
net [39–42].
and complex 1 show monomeric structure, complexes 2 and 3 ex-
hibit 1D structures, while 4 and 5 display 3D metal–organic frame-
works, as shown in Scheme 2. To the same metal ion and auxiliary
ligand, complexes 4 and 5 with H2L2 ligand exhibit higher dimen-
sionality than complexes 2 and 3 with H2L1 ligand because the
angular between the carboxylate group and the nitrogen coordi-

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C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
Fig. 4. (a) View of the 1D chain of complex 2 along the c axis; (b) The 3D supramolecular network with rhombus channels of 2 along the c axis.
3.6.2. Metal ions
With the same ligands H2L1 and 4,40-bipy, Ni complex (2) and Co
complex (3) exhibit different structures. In 2, both pyrazoe nitrogen
atoms and carboxylate oxygen atoms are in cis-positions, while in 3,
both pyrazoe nitrogen atoms and carboxylate oxygen atoms are in
trans-positions [43]. Moreover, complex 2 exhibits a 3D supramolec-
ular network with rhombus channels, while complex 3 displays a 3D
supramolecular network consisting of double-stranded homohelix
chains. With the same ligands H2L2 and 4,40-bipy, Ni complex (4)
and Co complex (5) also show different structures. Complex 4
contains binuclear asymmetric units, and exhibits a 3D (4,6)-con-
nected framework with (44ꢀ58ꢀ63)(54ꢀ6ꢀ8) topology, while 5 consists
of mononuclear units, and displays a 3D six-connected NaCl-like
framework with (412ꢀ63) topology. Furthermore, there are two ori-
entations of H2L1 and H2L2 ligands in Ni complexes (2 and 4), respec-
tively, while only one orientation of H2L1 and H2L2 ligands in Co
complexes (3 and 5), respectively. These differences on the struc-
tures of complexes 2 and 3 as well as complexes 4 and 5 indicate that
a subtle distinction of ionic radius will lead to a completely different
structure of complexes for the same ligand and coligand.
3.6.3. Auxiliary ligands
Fig. 5. The coordination environment of Co(II) ion in complex 3 with 30% thermal
ellipsoids. All hydrogen atoms are omitted for clarity (symmetry operations: A:
ꢁx + 1, y, ꢁz; B: x, y + 1, z).
To the same H2L1 ligand and Ni(II) ion, complexes 1 and
[Ni(HL1)2(H2O)2] (6) reported by our group [30] exhibit monomeric
structures, while 2 displays 1D structure. To the same H2L2 ligand
and Ni(II) ion, complex 4 possesses 3D metal–organic framework,
but [Ni(HL2)2(H2O)2] (7) also reported by our group [30] exhibits
1D structure. These results indicate that auxiliary ligand 4,40-bipy
help to enhance the dimensionality of complexes due to its bridging
ability, while 2,20-bipy only joins one metal ion and goes against the
formation of high dimensional structures.
nate sites in H2L2 is bigger than that in H2L1. In addition, complexes
4 and 5 both contain 1D channels, which show that the angular be-
tween O- and N-coordination sites in H2L2 help the formation of
microporous structures.

C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
283
Fig. 6. (a) The 3D supramolecular network consisting of homohelix chains of 3 along the c axis, the phenyl rings of HL1 ligands are omitted for clarity. (b) A left-handed double
helical chain consisting of two antiparallel helical chains.
Fig. 7. The coordination environment of Ni(II) ions in complex 4 with 30% thermal
ellipsoids. All hydrogen atoms are omitted for clarity (symmetry operations:
A: ꢁx + 1/2, y, ꢁz + 1; B: x, y + 1, z; C: x + 1/2, ꢁy + 1, z; D: ꢁx, y ꢁ 1/2, ꢁz + 1/2; E:
ꢁx + 1/2, ꢁy + 1/2, ꢁz + 1/2).
In addition, of five complexes, only complex 3 crystallize in chi-
ral group, although H2L1 and H2L2 ligands are chiral compounds. In
general, how to design or make a chiral feature from pairs of enan-
tiomer relies on the understanding of ligands and crystal packing,
especially the latter. It remains challenge for the chemists to obtain
homochiral crystallization of helical coordination polymers
through spontaneous enantiomer selection.
3.7. Thermogravimetric analyses and powder X-ray diffraction
Thermogravimetric (TG) analyses of complexes 1–5 were carried
out to examine their thermal stabilities, as shown in Fig. 11. The
observed TG curve reveals that complex 1 1ost its lattice water mol-
ecules at the first weight loss of 8.1% (calcd. 8.4%) from 81 to 124 °C.
The TG curve shows a plateau from 124 to 239 °C, then further
decomposition began at 239 °C. There are no water molecules in
complex 2, and it was stable up to about 334 °C and then began to
Fig. 8. (a) The 3D metal–organic framework of complex 4 with 1D channels along
decompose with a continuous weight up to above 800 °C. The TG
the a axis, the lattice water molecules are shown by spacing-filling model. (b)
Schematic representation of a new (4,6)-connected network with (44ꢀ58ꢀ63)(54ꢀ6ꢀ8)
curve of complex 3 reveals a weight loss of 12.9% from 45 to
196 °C, which corresponds to the loss of five lattice water molecules
topology.

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C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
Fig. 9. The coordination environment of Co(II) ion in complex 5 with 30% thermal
ellipsoids. All hydrogen atoms are omitted for clarity (symmetry operations:
A: ꢁx + 1/2, y + 1/2, ꢁz + 3/2; B: x, ꢁy, z + 1/2; C: ꢁx + 1/2, ꢁy + 1/2, ꢁz + 2).
Ni2+/2,2 -bipy
(1) [Ni(HL1)2(2,2 -bipy)]·3H2O (0D)
COOH
Ph
Ni2+/4,4 -bipy
(2) [Ni(HL1)2(4,4 -bipy)]
(1D)
(H2L1)
N
HN
Co2+/4,4 -bipy
Ni2+/4,4 -bipy
(3) [Co(HL1)2(4,4 -bipy)]·5H2O (1D)
COOH
NH
Ph
(4) [Ni2(HL2)4·(4,4 -bipy)·(H2O)2]·4H2O] (3D)
(H2L2)
N
Co2+/4,4 -bipy
(5) [Co(HL2)2·(4,4 -bipy)]
(3D)
Scheme 2. Schematic synthesis procedure and the relationship between the
dimensionality and the organic ligands of complexes 1–5.
(calcd. 13.3%). Increasing temperature led to the further decomposi-
tion began at 196 °C. For complex 4, the TG curve displays that the
first weight loss of 9.9% from 65 to 133 °C, corresponding to the loss
of two coordinated water molecules and four lattice water mole-
cules (calcd. 9.6%). The residue remain stable below 268 °C, and it
begins to decompose subsequently above 268 °C. Similar to complex
2, there are no water molecules in complex 5, and it was stable up to
about 252 °C and then began to decompose with a continuous
weight loss up to above 800 °C.
Fig. 10. (a) The 3D metal–organic framework of complex 5 with 1D channels along
the b axis. (b) Schematic representation of a six-connected NaCl-like network with
(412ꢀ63) topology.
According to the TG analyses, powder XRD patterns of com-
plexes 4 and 5 were recorded. For complex 4, the powder XRD pat-
terns of the sample at 50 and 150 °C are not the same although
very similar, which indicates the change of the frameworks after
the removal of lattice and coordinated water molecules. Above
290 °C, the powder XRD patterns change completely, suggesting
the collapse of the framework (Fig. 12a). The powder XRD patterns
for complex 5 at 100 and 240 °C are the same, indicating that the
structural integrity of the framework is maintained. The further
decomposition starts at 250 °C, and above 350 °C, the powder
XRD patterns change completely, suggesting the collapse of the
framework (Fig. 12b).
negative bacteria: E. coli and P. aeruginosa at MIC values between
6.25 and 50 lg/mL. The complexes have more activities than corre-
sponding free ligands against the tested bacteria. This would imply
that the chelation could facilitate the ability of a complex to cross a
cell membrane and can be explained by Tweedy’s chelation theory
[44]. Chelation considerably reduces the polarity of the metal ion
because of partial sharing of its positive charge with the donor
groups. Such chelation could enhance the lipophilic character of
the metal atom, which subsequently favor its permeation through
the lipid layers of cell membrane [45].
3.8. Antibacterial activity results
4. Conclusions
The antibacterial activities of H2L1 and H2L2 ligands, and com-
plexes 1–5 have been carried out against the selected microorgan-
isms. From the results given in Table 4, it has been observed that all
selected compounds show antibacterial activities against Gram
positive bacteria: S. aureus, C. albicans and B. subtilis, and Gram
Five new transition metal complexes have been synthesized
based on phenyl substituted pyrazole carboxylic acid and N-donor
co-ligands. The structural versatilities for the title complexes re-
veal that different substitution positions of carboxylate group on

C.-B. Liu et al. / Inorganica Chimica Acta 383 (2012) 277–286
285
Table 4
Minimal inhibitory concentration (MIC) values of H2L1 and H2L2 ligands, and the title
(a)
100
80
60
40
20
complexes against the tested bacteria (lg/mL).
Complex 1
Complex 2
Complex 3
Compound
S. aureus
C. albicans
B. subtilis
E. coli
P. aeruginosa
H2L1
25
25
50
50
25
H2L2
50
25
25
50
50
1
2
3
4
5
12.5
12.5
6.25
12.5
12.5
12.5
6.25
12.5
12.5
12.5
25
25
6.25
25
6.25
25
12.5
25
12.5
25
6.25
12.5
12.5
12.5
12.5
the pyrazole ring, metal ions and auxiliary ligands have significant
effect on the formation and the structures of the resulting com-
plexes. The 3D metal–organic frameworks with 1D channels of
complexes 4 and 5 also show that microporous structures can be
obtained by changing the angular between O- and N-coordination
sites for pyrazole carboxylic acid. In addition, the antibacterial
activities screening showed that the complexes have more activity
than corresponding free ligand against the tested bacteria.
0
200
400
600
800
Temperature(oC)
(b)
100
Complex 4
Complex 5
80
60
40
20
Acknowledgments
This work was supported by the Natural Science Foundation of
China (Grant No. 20961007), the Aviation Fund (Grant No. 2010ZF5
6023) and the Young Scientists Program of Jiangxi Province (Grant
No. 2008DQ00600).
Appendix A. Supplementary material
0
200
400
600
800
Temperature(oC)
CCDC 824364 (for 1), 824365 (for 2), 824366 (for 3), 824367 (for
4) and 824368 (for 5) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/j.ica.
2011.11.015.
Fig. 11. TG curves of complexes 1–3 (a) and 4 and 5 (b).
(a)
290oC
270oC
150oC
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