Syntheses, supramolecular structures and antibacterial activities of five helical transition complexes with 5-chloro-1-phenyl-1H-pyrazole-3,4-dicarboxylic acid

Article abstract of DOI:10.1002/cjoc.201201009

Five new transition metal complexes [Cu(HL)₂(H ₂O)₂] (1), [Cu(HL)₂(phen)] (2), [Cu(HL) ₂(H₂O)]₂(4,4'-bipy) (3), [Zn(HL) ₂(H₂O)₂]·(4,4'-bipy) (4),

Full text of DOI:10.1002/cjoc.201201009

FULL PAPER
DOI: 10.1002/cjoc.201201009
Syntheses, Supramolecular Structures and Antibacterial
Activities of Five Helical Transition Complexes with
5-Chloro-1-phenyl-1H-pyrazole-3,4-dicarboxylic Acid
Hong Liu,a,b Chongbo Liu,*,a,b Yunnan Gong,a Yuhua Wang,a and Huiliang Wenc
a Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control,
Nanchang Hang Kong University, Nanchang, Jiangxi 330063, China
b School of Environment and Chemical Engineering, Nanchang Hang Kong University,
Nanchang, Jiangxi 330063, China
c State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang,
Jiangxi 330047, China
Five new transition metal complexes [Cu(HL)2(H2O)2] (1), [Cu(HL)2(phen)] (2), [Cu(HL)2(H2O)]2(4,4'-bipy)
(3), [Zn(HL)2(H2O)2]•(4,4'-bipy) (4), [Ag(HL)(4,4'-bipy)]n (5), (H2L＝5-chloro-1-phenyl-1H-pyrazole-3,4-
dicarboxylic acid, phen＝1,10-phenanthroline; 4,4'-bipy＝4,4'-bipyridine) have been synthesized and characterized.
Complexes 1, 2 and 4 exhibit monomeric structures, 3 shows a dinuclear structure, 5 displays 1D chain structure,
and all extend to 3D supramolecular network via rich hydrogen bonds. Complexes 1, 2, 3, 5 comprise single helical
chains, while complex 4 generates quadruple-stranded helical chains. Furthermore, the antibacterial activities of the
titled complexes against bacterial species, three Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis
and Candida albicans) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were stud-
ied and compared to the activities of free ligands by using the microdilution method.
Keywords helix, transition metal complexes, pyrazole carboxylic acid, N-donor co-ligands, antibacterial activity
Introduction
tained.[8] It has two oxo carboxylate groups and one ni-
trogen atom with suitable angle, which not only help to
construct 3d, 4f or 3d-4f supramolecular networks; but
also help to generate helical chain structure; the intro-
duction of benzene ring, which can increase the possi-
bility of C－H···O (N, π) hydrogen bonds and π-π inter-
actions, as well as induce distinctive helical structures
as a result of phenyl ring and pyrazole ring being se-
verely twisted across the C－C single bond. It is well
known that C－H···π interactions and π-π interac-
tions are very important intermolecular interactions in
the crystal lattice, which are responsible for extension of
the supramolecular network of the compound and stabi-
lization of the crystal structure.[9] In addition, auxiliary
ligands due to their different sizes and coordination
modes, often have significant effect on the formation
and the structures of complexes.[10-12] In particular,
N-donor co-ligands, such as 4,4'-bipyridine and
1,10-phenanthroline not only own the features of flexi-
ble and angular ditopic ligand contributing to helical
structures,[13] but also can act as hydrogen-bonded do-
nors and acceptors to form rich directional hydrogen
bonds, which help to construct high dimensional su-
pramolecular structure.
In recent years many interests have been focused on
the self-assembly of supramolecular complexes, because
of their intriguing structure topology and their broad
potential applications in magnetism, nonlinear optics,
luminescence, selective sensing and antimicrobial prop-
erties.[1] Among them, the designing and construction of
the helical complexes with supramolecular structure is
one of the most challenging and significant task owing
to their ubiquitous appearance in nature,[2] such as pep-
tide a-spiral structure, DNA double-helix, quartz carbon
nanotubes. Up to now, a lot of single,[3] double[4] or
multi-stranded helices[5] constructed through coordina-
tion interactions have been generated by self-assembly
process, however, helical structures constructed via hy-
drogen bonding and other supramolecular interactions
are still rare.[6] Generally, the structures of the com-
plexes depend on the combination of several factors,
including organic ligands, metal ions, pH value, reaction
temperature, etc.[7] 5-Chloro-1-phenyl-1H-pyrazole-3,4-
dicarboxylic acid (H2L) is a new example of polyfunc-
tional ligands. Its coordination chemistry has been stud-
ied and some coordination polymers have been ob-
*
E-mail: cbliu2002@163.com
Received October 17, 2012; accepted December 4, 2012; published online March 1, 2013.
Chin. J. Chem. 2013, 31, 407—414
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407

Liu et al.
FULL PAPER
On the other hand, metal ions, especially their radius
and coordination geometry, determine the extending
directions and the coordination modes of organic
ligands, which is also important for the structure of the
complexes.[14] In the present work, three transition metal
elements Cu, Zn and Ag are selected to investigate the
metal ion effects on the structures of phenyl substituted
pyrazole carboxylic acid complexes, and five complexes
[Cu(HL)2(H2O)2] (1), [Cu(HL)2(phen)] (2), [Cu(HL)2-
(H2O)]2(4,4'-bipy) (3), [Zn(HL)2(H2O)2]•(4,4'-bipy) (4),
[Ag(HL)(4,4'-bipy)]n (5), (phen＝1,10-phenanthroline;
4,4'-bipy＝4,4'-bipyridine) are synthesized under the
synergy of primary ligand and N-donor secondary
ligands, and the biological activities of H2L ligand and
its metal complexes are also evaluated by determining
MIC of inhibition against Gram-positive and Gram-
negative bacteria.
(based on Cu). Anal. calcd for C27H18Cl2CuN5O9: C
46.93, H 2.61, N 10.14; found C 47.35, H 2.26, N, 10.52;
IR data (KBr) ν: 3457 m, 3139 s, 1703 w, 1613 m, 1538
m, 1401 s, 1327 m, 1222 w, 1113 w, 1066 w, 1004 w,
－
1
778 w cm .
Synthesis of complex
4
A
mixture of
ZnSO4•7H2O (0.0284 g, 0.1 mmol), H2L (0.02 g, 0.1
mmol), 4,4'-bipy (0.016 g, 0.1 mmol ), H2O (10 mL)
－
1
and NaOH (0.2 mmol, 0.65 mol•L ) was sealed in a
Teflon-lined stainless reactor (25 mL) and heated at 90
℃ for 72 h under autogenous pressure. Colorless block
crystals were obtained. Yield 34.6% (based on Zn). Anal.
calcd for C32H24Cl2ZnN6O10: C 48.72, H 3.04, N 10.66;
found C 49.21, H 2.95, N 10.87; IR data (KBr) ν: 3432
m, 3146 s, 1715 w, 1610 s, 1511 m, 1399 s, 1367 s,
－
1
1230 w, 1168 w, 808 w cm .
Synthesis of complex 5 The synthesis of 5 was
similar with that of 4, except that 0.1 mmol AgNO3 and
0.1 mmol CoCl2•6H2O was used instead of
ZnSO4•7H2O, and the amount of NaOH in 5 is half of
that in 4. Colorless block crystals were obtained. Yield
37.5% (based on Ag). Anal. calcd for C21H14ClAgN4O4:
C 47.62, H 2.66, N 10.58; found C 47.95, H 2.33, N
10.84; IR data (KBr) ν: 1709 w, 1616 w, 1560 m, 1404 s,
Experimental
Materials and instrumentation
All the reagents except H2L ligand were commer-
cially available and used without further purification. 1H
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 Ele-
mentar analyzer. The IR spectra were recorded with a
Nicolet Avatar 360 FT-IR spectrometer using the KBr
pellet technique.
－
1
1323 w, 1261 w, 1118 w, 1006 m, 789 s cm .
X-ray crystallographic study
The X-ray single-crystal data of complexes 1－5
were recorded on a Brucker APEX II area detector dif-
fractometer with a graphite-monochromated Mo Kα
radiation (λ＝0.71073 Å). Semi-empirical absorption
corrections were applied to the title complexes using the
SADABS program.[15] The structures were solved by
direct methods[16] and refined by full-matrix least
squares on F2 using SHELXL-97.[17] All non-hydrogen
atoms were refined anisotropically. The carboxyl and
water H atoms were located from difference Fourier
map, the other hydrogen atoms were placed in geomet-
rically calculated positions. Experimental details for
X-ray data collection of 1－5 are presented in Table 1,
and the selected bond lengths and angles are listed in
Table 2, and the main hydrogen bonding lengths and
angles are listed in Table 3.
Synthesis of the complexes
Synthesis of complex 1 A mixture of CuSO4•
5H2O (0.025 g, 0.1 mmol), H2L (0.02 g, 0.1 mmol),
isonicotinic acid (0.0123 g, 0.1 mmol), 4,4'-bipy (0.016
g, 0.1 mmol), H2O (10 mL) and NaOH (0.1 mmol, 0.65
mol•L-1) was sealed in a Teflon-lined stainless reactor
(25 mL) and heated at 120 ℃ for 72 h under autoge-
nous pressure. Then cooling to room temperature, the
remaining solution was filtered and evaporated slowly
at room temperature, blue block crystals were obtained.
Yield 45.2% (based on Cu). Anal. calcd for
C22H16Cl2CuN4O10: C 41.88, H 2.54, N 8.88; found C
42.25, H 2.32, N 9.13; IR data (KBr) ν: 3444 m, 3137 s,
1702 m, 1612 m, 1541 w, 1398 s, 1249 w, 1058 m, 696
－
1
Antibacterial testing
w cm .
The in vitro antibacterial activities of the H2L ligand
and complexes 1－5 were tested against Staphylococcus
aureus, Bacillus subtilis, Candida albicans, Escherichia
coli and Pseudomonas aeruginosa by the minimum in-
hibitory concentration (MIC) method. The compounds
were dissolved in DMF with 2-fold serial dilutions from
200 to 6.25 μg/mL. Sterile micro tubes were filled with
1 mL of serial 2-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 ℃ for 24 h. MICs were defined
as the lowest concentrations of the compounds which
inhibited the growth of microorganisms, DMF was
Synthesis of complex 2 The synthesis of 2 was
similar with that of 1, only 0.1 mmol phen was used
instead of 0.1 mmol isonicotinic acid and 0.1 mmol
4,4'-bipy, and the solvent is 7 mL H2O, and 3 mL EtOH.
Blue block crystals were obtained. Yield 33.1% (based
on Cu). Anal. calcd for C34H20Cl2CuN6O8: C 52.69, H
2.58, N 10.85; found C 53.01, H 2.42, N 11.34; IR data
(KBr) ν: 1721 m, 1616 m, 1555 w, 1501 w, 1411 s, 1340
－
1
w, 1273 w, 1062 w, 864 m, 614 s cm .
Synthesis of complex 3 The synthesis of 3 was
similar with that of 1, except that isonicotinic acid was
not added, and the amount of H2L in 3 is twice of that in
1. Blue block crystals were obtained. Yield 39.8%
408
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Chin. J. Chem. 2013, 31, 407—414

Syntheses, Supramolecular Structures and Antibacterial Activities of Five Helical Transition Complexes
Table 1 Crystal data for complexes 1－5
1
2
3
4
5
Empirical formula
C22H16Cl2CuN4O10 C34H20Cl2CuN6O8 C27H18Cl2CuN5O9 C32H24Cl2ZnN6O10 C21H14ClAgN4O4
Formula weight
630.83
296(2)
Monoclinic
P21/c
775.00
296(2)
Monoclinic
C2/c
690.90
296(2)
Monoclinic
P21/c
788.84
529.68
296(2)
T/K
296(2)
Crystal system
Triclinic
P1
Monoclinic
P21/c
Space group
a/Å
8.790(2)
19.452(5)
7.352(18)
90
9.956(10)
20.998(2)
15.244(15)
90
9.216(11)
16.856(2)
18.253(2)
90
7.836(6)
9.654(8)
11.713(10)
107.528(10)
97.397(10)
93.471(10)
833.18(12)
1
11.372(16)
20.484(3)
8.899(13)
90
b/Å
c/Å
α/(°)
β/(°)
γ/(°)
106.397(3)
90
97.184(10)
90
95.937(2)
90
110.999(2)
90
V/Å3
1206.1(5)
2
3162.1(5)
4
2820.1(6)
4
1935.2(5)
4
Z
Crystal size/mm
0.23×0.17×0.06 0.16×0.04×0.04 0.18×0.16×0.14 0.27×0.21×0.19 0.14×0.12×0.06
Dc/(mg•m－
)
1.737
1.628
1.627
1.572
1.818
3
μ/mm－
1.194
0.926
1.028
0.965
1.219
1
F(000)
638
1572
1400
402
1056
θ range/(°)
2.42－25.50
0.980
2.28－27.50
1.009
2.53－25.50
1.017
2.41－25.50
1.095
2.16－25.50
1.011
Goodness-of-fit on F2/(e•Å－
No. data collected
No. unique data
Rint
)
3
9212
14061
21523
6455
14840
2248
3616
5238
3087
3602
0.032
0.066
0.054
0.014
0.032
R1, wR2 [I＞2σ(I)]
R1, wR2 (all data)
0.033, 0.071
0.047, 0.079
0.048, 0.089
0.095, 0.105
0.040, 0.079
0.078, 0.093
0.047, 0.137
0.053, 0.142
0.033, 0.067
0.048, 0.074
Largest diff. peak
0.357, －0.255
0.358, －0.377
0.288, －0.326
0.430, －0.965
1.223, －0.563
and hole/(e•Å－
)
3
Table 2 Selected bond lengths (Å) and angles (°) for complexes
1－5
Continued
5
Ag(1)－O(1) 2.568(3)
Ag(1)－N(1) 2.147(3)
1
2.144(3)
Ag(1)－N(2)#1
Cu(1)－O(4) 1.958(18)
Cu(1)－O(5) 1.948 (2)
Cu(1)－N(2) 2.486 (2)
Cu(1)－O(4)#1
Cu(1)－O(5)#1
Cu(1)－N(2)#1
1.958(18)
1.948 (2)
2.486 (2)
Symmetry operation: #1 x－1, y, z.
Symmetry operation: #1 －x＋1, －y＋1, －z＋2.
Table 3 Hydrogen bonding geometry [Å and (°)] for complexes
1－5
2
Cu(1)－O(4) 1.958(2)
Cu(1)－N(2) 2.425(2)
Cu(1)－N(3) 1.996(2)
Cu(1)－O(4)#1
Cu(1)－N(2)#1
Cu(1)－N(3)#1
1.958(2)
2.425(2)
1.996(2)
D－H···A
d(D－H) d(H···A) d(D···A) ∠(DHA)
1
O(2)－H(2A)···O(3)
0.82
1.62
1.82
1.95
2.433(3) 174.9
2.640(3) 173.2
2.764(3) 172.3
Symmetry operation: #1 －x＋2, y, －z＋1/2.
O(5)－H(1W)···O(1)#1 0.82
O(5)－H(2W)···O(2)#2 0.82
3
Cu(1)－O(1) 1.974(2)
Cu(1)－O(5) 1.989(2)
Cu(1)－O(9) 2.184(3)
Cu(1)－N(2)
Cu(1)－N(3)
Cu(1)－N(5)
4
2.121(3)
2.435(3)
1.983(2)
Symmetry operations: #1 x＋1, y, z＋1; #2 －x, －y＋1, －z＋2.
2
O(2)－H(2A)···O(3)
C(17)－H(17)···O(3)#1 0.93
C(2)－H(2)···π#2 0.93
0.82
1.69
2.30
3.02
2.505(4) 178.0
3.175(5) 156.0
3.688(3) 130.0
Zn(1)－O(1) 2.082(2)
Zn(1)－O(5) 2.042(2)
Zn(1)－N(3) 2.207(3)
Zn(1)－O(1)#2
Zn(1)－O(5)#2
Zn(1)－N(3)#2
2.082(2)
2.042(2)
2.207(3)
Symmetry operations: #1 x－1/2, y＋1/2, z; #2 －x＋3/2, －y＋
3/2, －z.
Symmetry operation: #2 －x＋1, －y＋1, －z＋1.
Chin. J. Chem. 2013, 31, 407—414
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FULL PAPER
Crystal structure of [Cu(HL)2(H2O)2] (1)
Continued
D－H···A
d(D－H) d(H···A) d(D···A) ∠(DHA)
Single crystal X-ray diffraction analysis reveal that
the asymmetric unit of complex 1 consists of one Cu(II)
ion, one HL ligand and one coordinated water molecule,
as shown in Figure 1a. The Cu(II) ion lies on an inver-
sion centre and coordinates to six atoms: two oxygen
atoms and two nitrogen atoms from two HL ligands,
another two oxygen atoms from two water molecules,
and the strong Jahn-Teller effect makes Cu(II) ion in an
elongated octahedral environment. In 1, HL ligands
show N,O-chelating coordination mode, each HL ligand
only links one Cu(II) ion (as shown in Scheme 2a), the
phenyl and pyrazole rings of HL ligand are twisted by
an angle of 41.9°. In 1, the Cu(HL)2(H2O)2 monomers
are connected through O(2)－H(2W)···O(5) hydrogen
bonds between coordinated water molecules and
uncoordinated carboxyl groups, resulting in left- and
right-handed helical chains united through Cu atoms
(Figure 2a), and the pitch of the helix running along the
a axis is the same as its length 8.79 Å. Furthermore,
helical chains are interlinked into a layer structure
through O(5)－H(1W)···O(1) hydrogen bonds between
coordinated water molecules and carboxyl oxygen at-
oms along the b-axis. In addition, face to face π-π stacks
exist between parallel phenyl planes of two neighboring
layers with the central distance of ca. 3.74 Å in 1, which
extend the 2D layers into a 3D supramolecular network,
as shown in Figure 2b.
3
O(9)－H(1W)···O(8)#1 0.83
O(9)－H(2W)···O(4)#2 0.81
1.94
1.99
1.69
1.65
2.41
2.51
2.760(4) 175.0
2.780(4) 166.0
2.510(4) 173.0
2.470(4) 178
O(3)－H(3)···O(2)
O(7)－H(7)···O(6)
0.82
0.82
C(3)－H(3A)···O(9)#3 0.93
C(26)－H(26)···O(5)#4 0.93
3.176(5) 139.0
3.307(4) 144.0
Symmetry operations: #1 x, －y＋1/2, z＋1/2; #2 －x＋2, y＋
1/2, －z＋1/2; #3 x－1, y, z; #4 －x＋2, －y＋1, －z.
4
O(5)－H(1W)···O(4)#1 0.82
O(5)－H(2W)···N(1)#2 0.82
1.97
1.86
1.68
2.55
2.791(4) 174.0
2.687(4) 174.0
2.490(5) 170.0
3.459(5) 165.0
O(3)－H(3)···O(2)
0.82
0.93
C(2)－H(2)···O(2)#3
Symmetry operations: #1 x, y＋1, z; #2 －x＋1, －y＋1, －z＋
1; #3 －x＋2, －y＋1, －z＋1.
5
O(3)－H(3A)···O(2)
C(3)－H(3)···O(4)#1
C(12)－H(12)···O(2)
0.82
0.93
0.93
1.65
2.45
2.42
2.39
2.83
2.465(5) 179.0
3.220(6) 140.0
3.348(5) 172.0
3.115(5) 135.0
3.570(5) 137.0
C(17)－H(17)···O(1)#2 0.93
C(15)－H(15)···π #3 0.93
Symmetry operations: #1 x－1, －y＋3/2, z－1/2; #2 x＋1, y, z;
#3 －x＋1, －y＋1, －z＋1.
Crystal structure of [Cu(HL)2(phen)] (2)
As shown in Figure 1b, the Cu(II) ion in complex 2
is six coordinated with two oxygen atoms and two ni-
trogen atoms from two HL ligands, another two nitrogen
atoms from one phen molecule, and the Cu(II) ion is in
an elongated octahedral geometry because of the
Jahn-Teller effect. In 2, HL and phen ligands show
N,O-chelating and N,N-chelating coordination modes
respectively. The [Cu(HL)2(phen)] monomers in 2 are
linked through C－H···O hydrogen bonds between C-H
groups of phen and carboxyl oxygen atoms giving left-
and right-handed helical chains (Figure 3a), the pitch of
the helix running along the a axis is the same as its
length (9.96 Å). As shown in Figure 3b, the helical
chains are further stacked to a 3D supramolecular net-
work along the a axis via C－H···π interactions between
C－H groups of phenyl rings of HL and pyrazole rings
(H···π distance is 3.00 Å and C－H···π angle is 125.88°).
inactive under the applied conditions.
Results and Discussion
Synthesis and characterization of ligand
H2L ligand was prepared according to the litera-
ture,[18] and the synthetic route of H2L ligand is shown
in Scheme 1. Yield ca. 85%. m.p. 239－240 ℃. Anal.
calcd for C11H7N2ClO4: C 49.55, H 2.65, N 10.51;
found C 49.83, H 2.36, N 10.95; IR (KBr) ν: 3451 m,
1698 vs, 1589 m, 1515 s, 1467 m, 1431 s, 1185 m cm ;
1H NMR (400 MHz, DMSO-d6) δ: 7.40－7.74 (m, 5H);
12.60 (d, J＝8.0 Hz, 2H).
－
1
Scheme 1 Synthesis route of H2L ligand
Crystal structure of [Cu(HL)2(H2O)]2(4,4'-bipy) (3)
H3C
As shown in Figure 1c, the Cu(II) ion in complex 3
is also in an elongated octahedral geometry, because of
the Jahn-Teller effect. And the Cu(II) ion is
six-coordinated with two oxygen atoms and two nitro-
gen atoms from two HL ligands, another oxygen atom
and another nitrogen atom from one water and one
4,4'-bipy molecule respectively. In 3, the coordination
mode of HL ligands is the same as that in 1, and
4,4'-bipy molecule adopts bridging coordination mode
O
O
AcOH
NHNH2
N
+
O
Na2SO3
H3C
O
C2H5
N
Ph
CHO
Cl
H3C
HOOC
COOH
Cl
DMF/POCl3
KMnO4/H2O
N
N
N
N
Ph
Ph
410
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Chin. J. Chem. 2013, 31, 407—414

Syntheses, Supramolecular Structures and Antibacterial Activities of Five Helical Transition Complexes
Figure 1 (a) Coordination environment of Cu(II) ions in complex 1 with 30% thermal ellipsoids; (b) Coordination environment of Cu(II)
ions in complex 2 with 30% thermal ellipsoids; (c) Coordination environment of Cu(II) ions in complex 3 with 30% thermal ellipsoids; (d)
Coordination environment of Zn(II) ions in complex 4 with 30% thermal ellipsoids; (e) Coordination environment of Ag(I) ion in com-
plex 5 with 30% thermal ellipsoids.
Figure 3 (a) View of helical chains with left-handed (pink) and
right-handed (dark red) helices of complex 2; (b) The 3D su-
Figure 2 (a) View of helical chains with left-handed (orange)
pramolecular network of 2 along the a axis.
and right-handed (yellow) helices complex 1 along the b axis; (b)
The 3D supramolecular network of 1 along the a axis.
bipy) monomers are connected through O(9)－
H(1W)···O(8) hydrogen bonds between coordinated
linking the Cu(II) ions into a dinuclear unit with Cu···Cu
distance of 11.04 Å. In 3, the [Cu(HL)2(H2O)]2(4,4'-
water molecules and uncoordinated carboxyl groups
giving left- and right-handed helical chains (Figure 4a),
Chin. J. Chem. 2013, 31, 407—414
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Liu et al.
FULL PAPER
[Zn(HL)2(H2O)2]•(4,4'-bipy) monomers are linked via
O－H···O, O－H···N and C－H···O hydrogen bonds
generating quadruple-stranded helical chains with two
left-handed and two right-handed helices (Figure 5a).
The left- and right-handed helical chains are united
through C3 atoms, and the pitch of the helix running
along the a axis is two times the length of the a axis
(15.67 Å). Moreover, the quadruple-stranded helical
chains are further packed to a 3D supramolecular net-
work through O－H···O hydrogen bonds, as shown in
Figure 5b. As is known, so far reports about single- and
double-stranded helical chains are not unusual, however,
triple-, quadruple-stranded as well as circular and cylin-
drical helical structures are rather rare, and complex 4 is
a new example of quadruple-stranded structures.[19]
Figure 4 (a) View of helical chains with left-handed (pink) and
right-handed (orange) helices of complex 3; (b) The 3D su-
pramolecular network of 3 along the b axis.
the pitch of the helix running along the b axis is the
same as its length (16.85 Å). Moreover, the helical
chains are further extended to a 2D structure via C(3)－
H(3A)···O(9) hydrogen bonds between C－H groups of
phenyl rings and coordinated water molecules, which
are further extended into a 3D supramolecular network
by O－H···O hydrogen bonds between coordinated wa-
ter molecules and carboxyl oxygen atoms, as shown in
Figure 4b.
Crystal structure of [Zn(HL)2(H2O)2]·(4,4'-bipy) (4)
In the asymmetric unit of complex 4, there is one
crystallographically independent Zn(II) ion, two HL
ligands and two coordinated water molecules and one
free 4,4'-bipy molecule. The Zn(II) ion locates on an
inversion centre, and coordinates to six atoms: two car-
boxyl oxygen atoms and two nitrogen atoms from two
HL ligands, and two oxygen atoms from two water
molecules, as shown in Figure 1d. In complex 4, HL
ligands adopt the same coordination mode, as that in
complexes 1－3; each HL ligand links one Zn(II) ion. In
4, there are abundant hydrogen bonds: (a) O－H···O
hydrogen bonds between coordinated water molecules
and carboxyl oxygen atoms; (b) O－H···N hydrogen
bonds between coordinated water molecules and nitro-
gen atoms of 4,4'-bipy; (c) C－H···O hydrogen bonds
between the C-H groups of 4,4'-bipy and carboxyl oxy-
gen atoms (Table 3). It is worthwhile noting that the
Figure 5 (a) View of quadruple-stranded hydrogen-bonded
helical chains with two left-handed (pink and turquoise) and two
right-handed (red and green) helices in complex 4; (b) The 3D
supramolecular network of 4 along the a axis.
Crystal structure of [Ag(HL)(4,4′-bipy)]n (5)
As shown in Figure 1e, the Ag(I) ion in complex 5 is
three-coordinated with one oxygen atom from one HL
ligand and two nitrogen atoms from two 4,4'-bipy
molecules. Different from 1－4, HL in complex 5 acts
as a monodentate ligand (as shown in Scheme 2b), and
4,4'-bipy molecules act as bis(monodentate) bridging
ligands, linking Ag(I) ions into 1D chain structure.
Moreover the 1D chains are further joined to a 2D layer
via C－H…O hydrogen bonds between C－H groups of
pyridine rings of 4,4'-bipy and carboxyl oxygen atoms
412
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Chin. J. Chem. 2013, 31, 407—414

Syntheses, Supramolecular Structures and Antibacterial Activities of Five Helical Transition Complexes
with single handed helical chains, as shown in Figure 6a.
To adjacent layers, the chirality of helix chain is oppo-
site. In addition, In 5, there are C－H···π interactions
between the C－H groups of 4,4'-bipy and phenyl rings
of HL of the adjacent layers (H···π distance is 2.83 Å, C
－H···π angle is 137°), and π···π interactions between
pyridine ring planes of neighboring layers with the
nearest central distance of ca. 3.73 Å in 5, which extend
the layers into a 3D supramolecular network along the a
axis (Figure 6b).
ture. Compared to the synthetic conditions of complexes
1 and 3, we find that the synthetic route of 3 is the same
with that of complex 1 except that isonicotinic acid was
not added in complex 3, but in complex 3, 4,4'-bipy
＋
molecule coordinates to Cu2 in bridging coordination
mode, while in complex 1, 4,4'-bipy molecule does not
exist, which indicate higher pH value may help 4,4'-bipy
coordinate to metal ions. In addition, isonicotinic acid or
CoCl2•6H2O was added in the syntheses of 1 and 5, re-
spectively, although they did not take part in coordina-
tion in complexes 1 and 5, complexes 1 and 5 were not
obtained without isonicotinic acid and CoCl2•6H2O re-
spectively, which indicate that isonicotinic acid and
CoCl2•6H2O might chang the pH value in the syntheses
process of 1 and 5, respectively.
Comparing the structure of complexes 3－5, to the
same ligand, different metal ion radius and coordination
number result in different metal coordination environ-
ments and thus different structures. The coordination
numbers of the metal ions in complexes 3－5 are 6, 6
and 3, respectively. The ionic radius of Cu(II), Zn(II)
and Ag(I) are almost the same, but the coordination
number reduces in sequence. Moreover, it is found that
the dimensionality of Cu(II), Zn(II) and Ag(I) com-
plexes increases while the coordination number of
Cu(II), Zn(II) and Ag(I) complexes decreases. In com-
plexes 3－5, every HL ligand only links one metal ion;
＋
and 4,4'-bipy molecules coordinate to Cu2 in bridging
coordination mode in complexes 3 and 5, while remain
＋
uncoordinated to Zn2 in complex 4, which result in the
dinuclear, monomeric and 1D chain structures of com-
plexes 3－5, respectively. Complexes 1, 2, 3 and 5
comprise single helical chains, while complex 4 con-
tains quadruple-stranded helical chains with the help of
more abundant hydrogen bonds between 4,4'-bipy and
Figure 6 (a) View of 2D layer structure with left-handed helix
chain in complex 5 along the c axis; (b) The 3D supramolecular
network of 5 along the a axis.
water molecule or carboxyl oxygen atoms, though
Scheme 2 Coordination modes of HL ligand
＋
4,4'-bipy remains uncoordinated to Zn2 in complex 4.
In conclusion, complexes 1－5 all present spiral struc-
tures under coordination bond and weak molecular in-
teractions. Besides, there are rich C－H···π interactions
and π-π stack interactions in complexes 1, 3 and 5, and
play an important role in forming three-dimensional
supramolecular structures of complexes 1, 3 and 5.
N
N
Cl
HO
Cl
HO
M
N
N
O
O
C
O
C
O
C
O
C
O
M
(a)
(b)
Antibacterial activity results
Comparison of the structures
The antibacterial activities of H2L, 4,4'-bipy and
phen ligands, and complexes 1－5 have been deter-
mined against the selected microorganisms. From the
results given in Table 4, it has been observed that pri-
mary ligand, auxiliary ligand and complex 4 show anti-
bacterial activities against the bacteria: S. aureus, C.
albicans, B. subtilis, E. coli and P. aeruginosa at MIC
values between 50 and 100 μg/mL, while the other
complexes show antibacterial activities against the
tested bacteria at MIC values between 6.25 and 50
μg/mL, which means that the inhibitory effect of most
complexes is stronger than the corresponding free
ligands. For different metal complexes, zinc complexes
H2L ligands in the titled five complexes exhibit two
kinds of coordination modes, and present the same
N,O-chelating coordination mode in complexes 1－4,
and act as a monodentate coordination mode in complex
5. So one HL ligand only connects one metal ion in
complexes 1－5. The crystal structures of complexes 1
－3 are different though the same ligand coordinates to
＋
the same metal ion (Cu2 ). Phen acts as chelating ter-
minal ligand in complex 2 and 4,4'-bipy acts as bridging
ligand in complex 3, while in complex 1, there is not
any auxiliary ligand. Complexes 1－2 exhibit mononu-
clear structures and complex 3 shows a dinuclear struc-
Chin. J. Chem. 2013, 31, 407—414
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
413

Liu et al.
FULL PAPER
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7009.
Table 4 Minimal inhibitory concentration (MIC) values of H2L,
4,4'-bipy and phen ligands, and the title complexes against the
tested bacteria (μg/mL)
Compound S. aureus B. subtilis C. albicans E. coli P. Aeruginosa
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Am. Chem. Soc. 2006, 128, 6806; (b) Yu, W.; Zhang, T. L.; Zhang, J.
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H2L
50
50
100
50
100
50
100
100
50
50
50
4,4'-bipy
phen
100
25
100
50
100
25
50
1
2
3
4
5
50
25
12.5
12.5
50
25
12.5
12.5
50
25
25
6.25
100
25
25
6.25
50
100
25
25
12.5
25
show weaker inhibition on the tested bacteria than cop-
per and silver complexes. For binary and ternary com-
plexes with the same metal ions and the same primary
ligands, binary complex (1) shows weaker inhibition
than ternary complexes (2 and 3).
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Conclusions
In conclusion, we have synthetized and characterized
five new transition metal complexes with 5-chloro-1-
phenyl-1H-pyrazole-3,4-dicarboxylic acid structurally
and antibacterially. Complexes 1, 2, 3, 5 comprise single
helical chains, while complex 4 generates quadruple-
stranded helical chains, and all extend to 3D supra-
molecular network via rich hydrogen bonds. The anti-
bacterial measurement shows the inhibitory effect of
most complexes is stronger than the corresponding free
ligands.
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Acknowledgement
This work was supported by the National Natural
Science Foundation of China (Nos. 20961007 and
21264011), the Aviation Fund (No. 2010ZF56023) and
the Young Scientists Program of Jiangxi Province (No.
2008DQ00600).
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