Synthesis, structural, and biological evaluation of the arene-linked pyrazolyl methane ligands and their d9/d10 metal complexes

Article abstract of DOI:10.1016/j.poly.2012.08.016

A series of the p-bis[(1-pyrazolyl)methyl] benzene ligands (L ₁-L₆) in the DMSO system were synthesized. In the mean time, by using the ligands as a linker, a new family of transition metal coordination polymers, namely, [Cu₂(L₁)₂Cl ₄] (1), [Cu₂(L₂)₂Cl₄] (2), [Ag(L₂)(NO₃)] (3), [Zn₂(L ₂)₂(SCN)₄] (4) and [Cd₂(L ₂)(SCN)₄] (5) [L₁ = 1,4-bis((1H-pyrazol-1-yl) methyl)benzene; L₂ = 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl) benzene] have been constructed by the reaction of the p-bis[(1-pyrazolyl)methyl] benzene and corresponding to the transition metal compounds in a mixed solution of CH₃OH/C₂H₅OH at mild temperature condition. All the coordination polymers and p-bis[(1-pyrazolyl)methyl]benzene ligands were characterized by elemental analysis, IR spectroscopy, ¹H NMR and ¹³C NMR, and some of them were characterized by UV spectroscopy, thermogravimetric analysis, X-ray powder and X-ray single-crystal diffraction. Structural analyses reveal that the ligands L₃-L₅ (L ₃ = 1,4-bis((4-iodo-1H-pyrazol-1-yl)methyl)benzene, L₄ = 1,4-bis((4-iodo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene, L₅ = 1,4-bis((4-nitro-1H-pyrazol-1-yl)methyl)benzene,L₆ = 1,4-bis((4-nitro-3,5-dimethyl-1H-pyrazol-1-yl) methyl) benzene) are discrete organic compound molecules and the complexes 1-5 are 1D M-L-M coordination polymers, which are further interlinked via hydrogen bonds resulting in 2D or even 3D supermolecular networks. The luminescent properties of the coordination polymers 3, 4 and 5 were examined by luminescence spectra. The analytic results indicate that different metal complexes with the same ligand have different influence on the characteristic photoluminescence. Furthermore, the cytotoxicity of the ligands L₁-L₆ and complexes 1-5 were evaluated against hepG2 cells. For the ligands of L₁-L₆, the different substituents of the pyrazole ring slightly influenced the cytotoxicity of the cell. It is found that nitro-compounds have shown the highest cytotoxicity under the same concentration condition. The cytotoxic activity of the complexes 1-5 are strongly increased by the introduction of the transition metals.

Full text of DOI:10.1016/j.poly.2012.08.016

Polyhedron 47 (2012) 151–164
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structural, and biological evaluation of the arene-linked pyrazolyl
methane ligands and their d9/d10 metal complexes
a,
d
Xin-Yu Wang a, Shu-Qing Liu b, Chun-Yan Zhang b, Ge Song a, Feng-Ying Bai c, , Yong-Heng Xing , Zhan Shi
⇑
⇑
a College of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 11602, PR China
b College of Life Science, Dalian Medical University, Dalian 11602, PR China
c College of Life Science, Liaoning Normal University, Dalian 11602, PR China
d State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of the p-bis[(1-pyrazolyl)methyl] benzene ligands (L1–L6) in the DMSO system were synthesized.
In the mean time, by using the ligands as a linker, a new family of transition metal coordination polymers,
namely, [Cu2(L1)2Cl4] (1), [Cu2(L2)2Cl4] (2), [Ag(L2)(NO3)] (3), [Zn2(L2)2(SCN)4] (4) and [Cd2(L2)(SCN)4] (5)
[L1 = 1,4-bis((1H-pyrazol-1-yl)methyl)benzene; L2 = 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl)ben-
zene] have been constructed by the reaction of the p-bis[(1-pyrazolyl)methyl]benzene and corresponding
to the transition metal compounds in a mixed solution of CH3OH/C2H5OH at mild temperature condition.
All the coordination polymers and p-bis[(1-pyrazolyl)methyl]benzene ligands were characterized by ele-
mental analysis, IR spectroscopy, 1H NMR and 13C NMR, and some of them were characterized by UV
spectroscopy, thermogravimetric analysis, X-ray powder and X-ray single-crystal diffraction. Structural
analyses reveal that the ligands L3–L5 (L3 = 1,4-bis((4-iodo-1H-pyrazol-1-yl)methyl)benzene, L4 = 1,4-bis
((4-iodo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene, L5 = 1,4-bis((4-nitro-1H-pyrazol-1-yl)methyl)
benzene,L6 = 1,4-bis((4-nitro-3,5-dimethyl-1H-pyrazol-1-yl) methyl) benzene) are discrete organic com-
pound molecules and the complexes 1–5 are 1D M–L–M coordination polymers, which are further inter-
linked via hydrogen bonds resulting in 2D or even 3D supermolecular networks. The luminescent
properties of the coordination polymers 3, 4 and 5 were examined by luminescence spectra. The analytic
results indicate that different metal complexes with the same ligand have different influence on the char-
acteristic photoluminescence. Furthermore, the cytotoxicity of the ligands L1–L6 and complexes 1–5 were
evaluated against hepG2 cells. For the ligands of L1–L6, the different substituents of the pyrazole ring
slightly influenced the cytotoxicity of the cell. It is found that nitro-compounds have shown the highest
cytotoxicity under the same concentration condition. The cytotoxic activity of the complexes 1–5 are
strongly increased by the introduction of the transition metals.
Received 16 May 2012
Accepted 6 August 2012
Available online 18 August 2012
Keywords:
Arene-linked pyrazolyl methane ligands
Transition metal complexes
Cytotoxic activity
Crystal structure
Spectra properties
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
structural motifs and properties. Among the organic building
blocks, N-heterocyclic ligands have been widely employed for this
Nowadays, as one of an attractive area of metal-organic frame-
works, supramolecular coordination complexes have been preva-
lently investigated. A great deal of works have been made to
design, synthesize and characteristic functional supramolecular
complexes, because they exhibit promising application in wide
fields of structural diversity, electronic properties [1,2], crystal
engineering, supramolecular chemistry, biological activity [3,4],
catalysis, sensors, pharmaceutical chemistry, etc. [5]. Apparently,
the judicious choices of special inorganic and organic building
blocks are the key steps for designing such materials with desired
purpose. In particular, tris(pyrazolyl)borate (Tp) and tris(3,5-dim-
ethylpyrazolyl) borate (Tp⁄) are the simplest and most frequently
encountered members of the scorpionate family, which were first
developed by Trofimenko in the mid-1960s [6]. The ligand is
named commonly as ‘‘the first generation’’ scorpionate ligand
and possess an extremely versatile class of facially coordinating
N-donors due to their ease of steric and electronic modification
[7]. Therefore, they are investigated widely in a number of different
purposes, including enzyme modelling, bioinorganic chemistry [8],
polymerization catalysts [9] and SOD mimetics [10]. On the other
hand, since synthesizing a series of ‘‘the second generation’’ scorpi-
onate-like ligands of poly(pyrazolyl)-alkanes, which have preva-
lent polydentate nitrogen donor ligands [11], some researchers
have contrasted the chemistry of complexes of the neutral
⇑
Corresponding authors.
E-mail
addresses:
baifengying@yahoo.com.cn
(F.-Y.
Bai),
xingyon-
gheng2000@163.com (Y.-H. Xing).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.016

152
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
poly(pyrazolyl)alkanes with that of previously poly(pyrazol-
yl)borates. Similarly, although these ligands could also form a vari-
ety of coordination complexes with main groups and transition
metal [12], complexes with poly(pyrazolyl)alkanes remain less to
be investigated so far, because of great difficulties encountered in
the process of preparing large amounts of these N-donor species.
More recently, ‘‘the third generation’’ arene-linked a variety of
nitrogen-based ligands, including pyrazolyl-pyrimidine, pyrazol-
yl-pyridazine and pyridyl-pyridazine [13,14], were successfully
synthesized and employed [15], which are specifically functional-
ized at the non-coordinating ‘‘back’’ position to have an insight into
the substances with uncommon solid state supramolecular archi-
tectures [16].
In order to further study the key roles in directing the final
supramolecular structure, we start to extend our work by choos-
ing special linear arene-linked p-bis[(1-pyrazolyl)methyl]benzene
ligands (Lp), because the third-generation have not only rigid
backbones but also flexible bis(pyrazolyl)methane units. Usually,
the multiple coordination sites of the ligands can form the struc-
tures of higher dimensions and high symmetry. However, it is
found that examples of high-dimensional supramolecular struc-
tures (2D and 3D) based on Lp ligand are rare up to now [17]. This
phenomenon could be attributed to the linear geometry of the li-
gand where donor groups are linked by a rigid spacer and the
chelating coordination mode adopted by the bis(pyrazolyl)meth-
ane units.
Recently, a series of benzene-linked mono-, bis(pyrazolyl)meth-
ane units (the third-generation) were synthesized by introducing
different substituents into the pyrazole ring. Due to the inherent
chemistry characteristic of benzene-linker, they present many vir-
tues as follows: mono-, bis(pyrazolyl) methane units directly fused
to an benzene ring to result in the formation of binuclear metalla-
cyclic complexes, making the structures of the complexes with
higher symmetry [18]; Moreover, pyrazolyl groups can freely twist
around alkyl groups with different angles to generate different
conformations and coordination modes, and form a variety of
supramolecular coordination complexes; Additionally, it is found
that they have an effective biological activity about inhibiting can-
cer cell growth [19].
To our best knowledge, the complexes of benzene-linker re-
ported by predecessors were mainly classified into three types
as follows: (i) benzene-linked di-pyrazolyl complexes of Cu(II),
Cd(II), Co(II) [20,21]; (ii) benzene-linked tetra-pyrazolyl com-
plexes of Ag(I), Ni(II), Co(II), Ir(II), Rh(II), Zn(II)and Fe(I)
[16,22,23]; (iii) benzene-linked hexa-pyrazolyl complexes of
Zn(II) and Re(I) [16,24]. The most works were focused on type
(ii), however, benzene-linked dipyrazolyl ligands are rarely used
to prepare metal–organic complexes with interesting structures,
functional properties, especially the luminescent property of the
complexes. In this paper, our group used 1,4-bis(bromo-
methyl)benzene and pyrazole/its derivatives as raw materials, a
series of benzene ring-linked pyrazolyl methane ligands (L1–L6)
in the DMSO system were synthesized [25]. In particular, based
on this linear ligands [1,4-bis((1H-pyrazol-1-yl)methyl)ben-
zene(L1);1,4-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene(L2)],
corresponding to the complexes were designed and synthesized
firstly by regulating proper reaction conditions. Fortunately, we
obtained and characterized a series of the novel copper(II), sil-
ver(I), zinc(II) and cadmium(II) complexes. In addition, we have
tested the biological activity of the ligands L1–L6 and complexes
1–5, with the purpose of comparing the variation in biological
activity of the changing different substituted groups for ligands
and different metal complexes. In general, the aim of this
report is to give a detailed synthesis rule and further systematic
investigation on bioactivity of the ligands and corresponding
complexes.
2. Experimental
2.1. Materials and general procedure
All chemicals purchased were of reagent grade or better and
were used without further purification. Biological reagent:
Dulbecco’s modified Eagle’s medium (DMEM) was purchased from
Hycone and fetal bovine serum (FBS) was purchased from TBD
(Tian Jin, China). The trypsin was purchased from Gibco Invitrogen
Corporation (Grand Island, NY, USA). Dimethyl sulfoxide (DMSO),
3(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium (MTT) were
purchased from Sigma (St. Louis MO, USA). DMSO in cells was main-
tained at 0.5%, which had no effect on cell growth or apoptosis. The
infrared spectra were recorded on a JASCO FT/IR-480 PLUS Fourier
Transform spectrometer with pressed KBr pellets in the range
200–4000 cmꢀ1. The elemental analyses for C, H, and N were
carried out on a Perkin Elmer 240C automatic analyzer. The lumi-
nescence spectra was reported on a JASCO F-6500 spectrofluorime-
ter (solid). UV–Vis absorption spectra diffuse reflection was
recorded with a UV–Vis/NIR spectrophotometer of JASCO V–570
in the 200–2500 nm (solid sample). Thermogravimetric analyses
(TGA) were performed under N2 atmosphere at 1 aim with a heating
rate of 10 °C/min on a Perkin Elmer Diamond TG/DTA. The 1H and
13C spectra were recorded on BrukerAV-500 apparatus (CDCl3 or
DMSO-d6 as solvent, TMS internal standard). X-ray powder diffrac-
tion (PXRD) patterns were obtained on a Bruker Advance-D8
equipped with CuKa radiation, in the range 5° < 2h < 60°, with a
step size of 0.02° (2h) and an count time of 2 s per step.
2.2. Synthesis
2.2.1. Synthesis of the ligands
2.2.1.1. Precursor: 1,4-bis(bromomethyl)benzene. It was prepared as
a method previously described [27]. Briefly, 29.6 mL (0.24 mol)
dry p-xylene was introduced into the flask, stirring at 140 °C in an
oil bath. When the xylene starts boiling, 24.6 mL (0.48 mol) of dry
bromine were added dropwise over 2 h and using a 300-watt tung-
sten lamp lighted reaction. To continued at 140 °C for an additional
3 h. Then, the mixture is cooled over night and dissolved in resul-
tant of warm chloroform. And the precipitate was dissolved in fresh
chloroform solution and recrystallizing in it. Yield: 55.4 g (87.4%).
m.p.:143–146 °C. Anal. Calc. for C8H8Br2: C, 36.40; H, 3.05. Found:
C, 36.29; H, 3.37%. FT-IR (KBr, cmꢀ1): 3050, 3036(@C–H); 2972
(C–H); 1512, 1437(Cph–Cph
; C
ph@Cph); 611(C–Br). 1H NMR
(500 MHz, DMSO-d6, d/ppm): 7.43 (s, 4H, ph), 4.69 (s, 4H, –CH2).
Ligands (L1–L6) were prepared according to the similar or mod-
ified references [26,28,29]. A mixed solution of pyrazole (1.02 g,
15 mmol) (L1) or its derivates (3,5-dimethyl-1H-pyrazole (1.47 g,
15 mmol) (L2), 4-iodo-1H-pyrazol (2.19 g, 15 mmol) (L3), 4-iodo-
3,5-dimethyl-1H-pyrazole (3.33 g, 15 mmol) (L4), 4-nitro-1H-pyra-
zole (1.70 g, 15 mmol) (L5), 4-nitro-3,5-dimethyl-1H-pyrazol
(2.12 g, 15 mmol) (L6)) and 82% potassium hydroxide (1.02 g,
15 mmol) in DMSO (10 mL) were vigorously stirred at 80 °C for
1 h. Then, 1,4-bis(bromomethyl)benzene (1.98 g, 7.5 mmol) in
DMSO (15 mL) was added dropwise to the solution above over
30 min, keeping the reaction at 80 °C to continue stirring for 5–
10 h. The mixture was poured into 200 mL of H2O and an amount
of precipitates occurred. Finally, the precipitate was filtered and
dried in the air. The precipitate was dissolved in the fresh chloro-
form solution and re-crystallized from it. The characterization data
of the ligands L1–L6 were listed in Table 1 and the detailed appoint-
ments of the IR spectra data are given in Table S1.
2.2.2. Synthesis of the complexes
The complexes 1–5 were prepared by the mixed solution reac-
tion of EtOH and MeOH. The starting material (CuCl2ꢁ2H2O

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
153
Table 1
The characterization data of the ligands L1–L6.
Compounds Elemental analyses (%)
1H NMR, d, ppm
13CNMR, d, ppm
Yield, m.p.
L1
Calc. for C14H14N4:
C, 70.57; H, 5.92;
7.53 (d, 2H, H5-pz, J = 1.7 Hz), 139.62, 136.55, 129.24, 128.04, 106.02, 55.52
1.23 g (68.9%)
111.5–1121 °C
7.36 (d, 2H, H3-pz, J = 2.2 Hz),
N, 23.51. Found: C, 70.49; 7.17 (s, 4H, ph), 6.27 (t, 2H,
H, 5.88; N, 23.63%
H4-pz, J1 = J2 = 2.1 Hz),
5.30 (s, 4H, CH2)
L2
Calc. for C18H22N4:
C, 73.44; H, 7.53;
7.00 (s, 4H, ph),
147.58, 139.11, 136.68, 126.92, 105.54, 52.23, 13.48, 11.07 1.35 g (61.2%)
5.82 (s, 2H, H4-pz),
101–102 °C
N, 19.03. Found: C, 73.57; 5.16 (s, 4H, CH2),
H, 7.32; N, 19.11%
2.22 (s, 6H, 5-CH3-pz),
2.12 (s, 6H, 3-CH3-pz)
7.53 (s, 2H, H5-pz),
7.40 (s, 2H, H3-pz),
L3
L4
L5
L6
Calc. for C14H12N4I2:
C, 34.31; H, 2.47;
144.76, 136.10, 133.67, 128.37, 56.62, 56.01
2.81 g (76.5%)
157–158 °C
N, 11.43. Found: C, 34.23; 7.20 (s, 4H, ph),
H, 2.55; N, 11.38%
Calc. for C18H20N4I2:
C, 39.58; H, 3.69;
5.28 (s, 4H, CH2)
7.02 (s, 4H, ph),
5.23 (s, 4H, CH2),
149.55, 140.68, 136.29, 127.16, 63.27, 53.59, 14.04, 12.04 3.62 g (88.4%)
188–191 °C
N, 10.26. Found: C, 39.46; 2.23 (s, 6H, 5-CH3-pz);
H, 3.55; N, 10.31%
Calc. for C14H12N6O4:
C, 51.22; H, 3.68;
2.16 (s, 6H, 3-CH3-pz)
9.02 (s, 2H, H5-pz),
8.25(s, 2H, H3-pz),
135.91, 135.68, 135.04, 130.58, 128.36, 55.37
1.61 g (65.4%). 269.9–271 °C
N, 25.60. Found: C, 51.18; 7.34 (s, 4H, ph),
H, 3.59; N, 25.68%
Calc. for C18H20N6O4:
5.39 (s, 4H, CH2)
7.13 (s, 4H, ph),
146.38, 140.29, 135.26, 127.67, 53.20, 14.14, 11.69
1.78 g (61.8%), 188.5–
C, 56.24; H, 5.24; N, 21.86. 5.24 (s, 4H, CH2),
189.4 °C
Found: C,56.18; H, 5.17;
N, 21.94%
2.55 (s, 6H, 5-CH3-pz),
2.52 (s, 6H, 3-CH3-pz)
(0.0170 g, 0.1 mmol) for complexes 1 and 2, AgNO3 (0.0170 g,
0.1 mmol) for 3, ZnSO4ꢁ7H2O (0.0287 g, 0.1 mmol) for 4,
Cd(NO3)2ꢁ4H2O (0.0308 g, 0.1 mmol) for 5) and corresponding to
ligands (L1 (0.0238 g, 0.1 mmol) for 1, L2 (0.0294 g, 0.1 mmol)
for 2–5) in CH3OH (15 mL) were dissolved in a 50 mL of the con-
ical flask. After a solution of oxalic acid (0.045 g, 0.5 mmol) for 1,
KSCN (0.0292 g, 0.3 mmol) for 4 or 5 dissolved in methanol of
5 mL was added dropwise to it, a precipitate is formed immedi-
ately, then the solution was refluxed for 3 h and filtered, the pre-
cipitate was washed with methanol and then dried at room
temperature. Corresponding crystals of the complexes (1–5) suit-
able for X-ray diffraction analysis crystallized from mother liquid.
The characterization data and the detailed appointment of the IR
spectra data for complexes 1–5 were listed in Table 2 and S2,
respectively.
2.4. Cell viability assay
The viability of the cells was assessed by MTT assay [30]. To be
specific, cells were detached and seeded in a 96-well plate (5 ꢂ 104
cells/well) and after 12 h, the medium was exchanged. Compounds
in different concentrations were incubated for a period of 24 h,
during this period, 20 lL of 1-(4,5-dimethylthiazol-2-yl)-3,5-
diphenylformazan (MTT) solution (5.0 mg mLꢀ1 in PBS) were
added to each well, which was incubated for an additional 4 h. Sub-
sequently, the medium was removed carefully, and 150 lL of
DMSO was added. Cell viability was determined by absorbance
measurements at 490 nm. In fact, the absorbance we measured is
correlated to a new produced blue compound, which was named
formazan. Calculate the rate of cell viability: Rate of cell growth
inhibition = AT/AC ꢂ 100%. AC was the absorbance for control set,
the same concentration of DMSO solvent with empty synthetic
compounds; AT was treated with series of compounds at individ-
ual concentration.
2.3. Cell line and culture
HepG-2 cell line derived from a human hepatocellular carci-
noma was given by Peking Union Medical College. Cells were cul-
tured in DMEM medium supplemented with 10% FBS,
2.5. X-ray crystallographic determination
Suitable single crystals of three compounds and five complexes
were mounted on glass fibers for X-ray measurement, respectively.
Reflection data were collected at room temperature on Rigaku R-
100 U mLꢀ1 penicillin and l00 g mLꢀ1 streptomycin, being main-
l
tained at 37 °C with 5% CO2 in a humidified atmosphere.
Table 2
The characterization data of complexes 1–5.
Complexes
Molecular formula
28H28N8Cu2Cl4
Elemental analyses (%)
Yield
1
C
Calc.: C, 46.11; H, 3.79; N, 15.03.
0.0315 g (77.40%)
0.0329 g (76.69%)
0.0309 g (66.60%)
0.0358 g (75.21%)
0.0498 g (66.26%)
Found: C, 45.02; H, 3.69; N, 14.98%
Calc.: C, 50.41; H, 5.17; N, 13.06;
Found: C, 50.10; H, 5.15; N,13.02%
Calc.: C, 46.57; H, 4.78; N, 15.08.
Found: C, 46.49; H, 4.75; N, 15.02.
Calc.: C, 52.22; H, 5.58; N, 16.61.
Found: C, 55.18; H: 5.54; N, 16.59%
Calc.: C, 35.16; H, 2.95; N, 14.91. Found: C, 35.11; H, 2.92; N, 14.89%
2
3
4
5
C36H44N8Cu4Cl4
C18H22N5O3Ag
C40H44N12S4Zn2
C22H22N8Cd2S4

154
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
Table 3
ligands were fixed at calculated positions with isotropic thermal
Crystallographic data for the compounds L3, L4 and L5.a
parameters. All calculations were performed using the SHELX-97
program [32]. Crystal data and details of the data collection and
the structure refinements of ligands L3–L5 are given in Table 3
and those of the complexes 1–5 are given in Table 4. The selected
bond lengths and bond angles of the ligands L3–L5 and the com-
plexes 1–5 are listed in Table 5. The drawings for all compounds
and complexes were made with Diamond 3.2.
Compounds
L3
L4
L5
Formula
Mr (g molꢀ1
Crystal
system
Space group
a (Å)
b (Å)
c (Å)
C7H6N2I
245.04
C9H10N2I
273.09
C7H6N3O2
164.15
monoclinic
)
triclinic
monoclinic
ꢀ
P21/c
P21/c
P1
4.5306(10)
8.2058(18)
11.009(2)
73.492(2)
82.107(3)
75.042(3)
378.22(14)
2
7.5347(11)
14.945(2)
8.7180(12)
90
95.782(2)
90
11.151(2)
4.5954(9)
14.707(3)
90
106.20(3)
90
723.7(2)
4
1.507
3. Results and discussion
a
(°)
b (°)
c
(°)
3.1. Synthesis
V (Å3)
976.7(2)
4
Z
By doing a great deal of experiment, it is found that it is espe-
cially crucial to meet the higher yield and quality of both looking
for suitable pyrazole/its derivatives as a raw material and regulat-
ing proper reaction conditions. For this purpose, we designed and
synthesized different types of pyrazolyl derivatives with iodination
or nitration substituted groups at first (shown in the Scheme 1).
Then by the reaction of pyrazole/its derivatives with 1,4-bis(bro-
momethyl)benzene in the DMSO system, furthermore, we obtained
a series of L1–L6 ligands (shown in the Scheme 2). During the reac-
tion above, it is found that the reaction result is affected by the fac-
tors of steric obstacle, substitution groups and reaction conditions.
In particular, the influence of the steric obstacle of the substituted
groups on pyrazolyl derivatives is the most important. So, the reac-
tion of 3,5-dimethylpyrazole/its derivatives with 1,4-bis(bromo-
methyl)benzene were more difficult than those of pyrazole/its
derivatives(4-I/NO2 substituted on pyrazolyl ring).
To get higher yields of the target products, it is found that the
optimization reaction condition of 1,4-bis(bromomethyl)benzene
with pyrazole/its derivatives is at a molar ratio of 1:2 and starting
reaction material of 1,4-bis(bromomethyl)benzene should be
added dropwise.
By the solvent reaction method, complexes 1–5 have been suc-
cessfully generated at the first time (Scheme 3). The crystalline sol-
ids are all soluble in most polar solvent. Here we have done our
best to search for the optimistic reaction conditions for improving
Dcalc (g cmꢀ3
Crystal size
(mm)
)
2.152
1.857
0.67 ꢂ 0.19 ꢂ 0.17 0.31 ꢂ 0.22 ꢂ 0.11 0.21 ꢂ 0.16 ꢂ 0.05
F(000)
230
524
340
0.115
l
(MoK
(mmꢀ1
h (°)
a
)
4.153
3.227
)
2.66–25.00
1875
2.72–25.00
4795
3.18–27.45
6409
Reflections
collected
Independent
1299(1224)
1706(1527)
1641(961)
reflections
(I > 2 (I))
Parameters
) (eÅꢀ3
r
91
111
109
D
(q
)
0.844, ꢀ1.384
0.425, ꢀ1.879
0.156, ꢀ0.221
Goodness-of-
fit (GOF)
Ra
1.266
1.210
1.053
0.0342(0.0359)b
0.1060(0.1071)b
0.0412(0.0449)b
0.1043(0.1069)b
0.0582(0.1053)b
0.1198(0.1371)b
a
wR2
a
2
R =
R
||Fo|ꢀ|Fc||/
R
|Fo|, wR2 = {
R
[w(Fo ꢀFc2)2]/
R r(Fo)].
[w(Fo2)2]}1/2; [Fo > 4
b
Based on all data.
AXIS RAPID IP (compounds L3 and L4, complex 1) and Bruker
SMART APEX II CCD (L5 and complexes 2–5) diffractometer with
graphite monochromatized MoK
absorption corrections were performed using the SADABS program
[31]. Crystal structures were solved by the direct method. All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms of
a radiation (k = 0.71073 Å). All
Table 4
Crystallographic data for complexes 1-5.a
Complexes
1
2
3
4
5
Formula
C
14H14N4Cl2Cu
C9H11N2ClCu0.5
214.42
C9H11N2.5O1.5Ag0.5
232.14
C20H22N6S2Zn
475.93
C11H11N4S2Cd
375.79
Mr (g molꢀ1
)
372.73
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
monoclinic
C2/c
monoclinic
C2/c
triclinic
P1
triclinic
P1
ꢀ
ꢀ
8.8153(12)
12.9316(18)
13.1313(18)
90
92.685(2)
90
1495.3(4)
4
1.656
14.723(3)
8.4311(17)
17.514(4)
90
114.14(3)
90
1983.9(7)
8
1.436
11.340(2)
14.189(3)
12.358(3)
90
102.17(3)
90
1943.8(7)
8
1.587
10.038(2)
11.057(2)
11.445(2)
71.81(3)
74.48(3)
86.08(3)
1162.7(4)
2
8.9615(18)
9.0061(18)
9.1711(18)
85.29(3)
76.67(3)
76.05(3)
698.7(2)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢀ3
)
1.359
1.786
Crystal size (mm)
0.43 ꢂ 0.09x0.08
0.37 ꢂ 0.25 ꢂ 0.13
029 ꢂ 0.16 ꢂ 0.08
029 ꢂ 0.16 ꢂ 0.07
032 ꢂ 0.25 ꢂ 0.13
F(000)
756
884
944
492
370
l
(MoK
a
) (mmꢀ1
)
1.815
2.21–24.99
7357
2632
190
1.378
3.03–27.49
9429
2264
117
1.065
3.10–24.99
7415
1710
124
1.253
3.13–27.48
10768
5050
262
1.848
3.22–27.48
6897
3178
174
h (Å3)
Reflections collected
Independent reflections (I > 2
Parameters
r(I))
D
(q
) (eÅꢀ3
)
0.294, ꢀ0.292
0.401, ꢀ0.341
2.667, ꢀ0.977
1.621, ꢀ0.976
0.567, ꢀ0.609
Goodness of fit
1.067
1.027
1.120
1.107
1.244
Ra
wR2
0.0328 (0.0483)b
0.0749 (0.0804)b
0.0369 (0.0496)b
0.0822 (0.0894)b
0.0807 (0.0875)b
0.2773 (0.2828)b
0.1169 (0.1468)b
0.3395 (0.3552)b
0.0256 (0.0288)b
0.0845 (0.0986)b
a
[w(Fo ꢀFc2)2]/
R r(Fo)].
[w(Fo2)2]}1/2; [Fo > 4
a
2
R =
R
||Fo|ꢀ|Fc||/
Based on all data.
R
|Fo|, wR2 = {
R
b

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
155
Table 5
0
Selected bond distances (AÅ) and angles (°) of the compounds and complexes.*
L3
I(1)–C(2)
C(2)–C(3)
C(4)–C(5)
N(1)–N(2)
N(1)–C(4)–C(5)
2.066(6)
1.379(8)
1.503(8)
1.360(7)
111.4(5)
C(1)–N(1)
C(3)–N(2)
1.343(8)
1.328(8)
1.387(8)
1.393(8)
128.6(4)
C(1)–C(2)
C(4)–N(1)
1.383(8)
1.458(8)
1.381(8)
1.393(8)
126.4(4)
C(5)–C(6)
C(6)–C(7)
C(5)–C(7)#1
C(3)–C(2)–I(1)
C(7)–C(5)#1
C(1)–C(2)–I(1)
L4
C(3)–I(1)
C(2)–C(3)
C(4)–C(5)
C(7)–C(9)
C(9)–C(8)#1
C(2)–C(3)–I(1)
2.073(5)
1.369(7)
1.491(7)
1.379(6)
1.385(7)
124.7(3)
C(2)–N(1)
C(3)–C(4)
C(6)–N(1)
C(7)–C(8)
N(1)–N(2)
C(4)–C(3)–I(1)
1.349(6)
1.403(7)
1.447(5)
1.381(6)
1.362(5)
128.3(4)
C(1)–C(2)
C(4)–N(2)
1.501(6)
1.337(7)
1.525(6)
1.384(7)
114.1(4)
C(6)–C(7)
C(8)–C(9)#1
N(1)–C(6)–C(7)
L5
N(3)–O(1)
C(1)–C(3)#1
C(4)–N(1)
C(6)–C(7)
N(1)–C(4)–C(2)
1.221(2)
1.383(3)
1.469(3)
1.373(3)
111.79(18)
N(3)–O(2)
C(2)–C(3)
C(5)–N(2)
C(6)–N(3)
O(1)–N(3)–O(2)
1.223(3)
1.382(3)
1.321(3)
1.417(3)
122.5(2)
C(1)–C(2)
C(2)–C(4)
C(5)–C(6)
N(1)–N(2)
O(1)–N(3)–C(6)
1.380(3)
1.509(3)
1.384(3)
1.365(3)
118.7(2)
Complex 1
Cu–N(1)
Cu–Cl(2)
N(1)–Cu–N(3)
N(1)–Cu–Cl(2)
2.002(2)
2.2528(9)
153.41(9)
91.29(7)
Cu–N(3)
2.011(2)
Cu–Cl(3)
2.2306(9)
N(1)–Cu–Cl(3)
N(3)–Cu–Cl(2)
93.61(7)
89.27(7)
N(3)–Cu–Cl(3)
Cl(3)–Cu–Cl(2)
98.71(7)
150.94(4)
Complex 2
N(2)–Cu
1.977(2)
1.330(3)
180.0
Cu–Cl(1)
2.2511(8)
N(1)–N(2)
1.364(3)
90.63(6)
C(2)–N(2)
N(2)#2–Cu–N(2)
C(2)–N(2)–Cu
N(2)–Cu–Cl(1)#2
N(1)–N(2)–Cu
89.37(6)
126.4(2)
N(2)–Cu–Cl(1)
127.5(2)
Complex 3
Ag–N(2)
2.210(8)
1.34(1)
129.9(4)
47.3(4)
Ag–O(1)
2.59(1)
N(2)–N(3)
1.33(1)
C(4)–N(2)
N(2)#1–Ag–N(2)
O(1)#1–Ag–O(1)
N(2)#1–Ag–O(1)#1
116.9(4)
N(2)–Ag–O(1)#1
108.8(4)
Complex 4
Zn–N(2)
Zn–N(5)
N(2)–Zn–N(1)
N(2)–Zn–N(5)
1.93(1)
Zn–N(1)
N(3)–N(4)
N(2)–Zn–N(4)
N(1)–Zn–N(5)
1.96(1)
1.37(1)
108.7(4)
104.3(4)
Zn–N(4)
C(8)–N(4)
N(1)–Zn–N(4)
N(4)–Zn–N(5)
2.019(9)
1.37(1)
110.4(4)
114.5(4)
2.053(9)
109.9(5)
109.0(4)
Complex 5
Cd–N(3)#1
Cd–S(2)
C(2)–N(2)
2.270(4)
2.609(1)
1.341(4)
90.9(2)
102.5(1)
92.3(1)
Cd–N(4)
Cd–S(1)
2.295(3)
2.735(1)
Cd–N(2)
N(1)–N(2)
2.297(3)
1.351(4)
N(3)#1–Cd–N(4)
N(3)#1–Cd–S(2)
N(3)#1–Cd–S(1)
S(2)–Cd–S(1)
N(3)#1–Cd–N(2)
N(4)–Cd–S(2)
N(4)–Cd–S(1)
107.9(1)
92.8(1)
176.0(1)
N(4)–Cd–N(2)
N(2)–Cd–S(2)
N(2)–Cd–S(1)
88.4(1)
149.52(8)
92.99(8)
84.18(4)
*
Symmetry transformations used to generate equivalent atoms: #1: ꢀx+1, ꢀy, ꢀz for L3; #1: ꢀx+2, ꢀy, ꢀz for L5; #2: ꢀx+1/2, ꢀy+1/2, ꢀz+1 for 2; #1: ꢀx+1, y, ꢀz+1/2 for 3;
#1: ꢀx+2, ꢀy, ꢀz+1 for 5.
Scheme 1. The synthetic routes of 4-iodo-pyrazole and 4-nitro-pyrazole.
coordination ability of the ligands with metal atoms. We designed
a reaction of CuCl2ꢁ2H2O or AgNO3 and L2 with molar ratio 1:1 and
got successfully single crystals of the complexes 2 and 3, respec-
tively. However, in the same reaction system, we could not get fine
single crystals of the complexes 4 and 5. Then, the addition of KSCN
(0.3 mmol) promoted the formation of the single crystals of the
complexes 4 and 5. The results show that some small molecular re-
agents are in the favor of the crystal growing of the complexes. In
order to further study influence about coordination capability of
the ligands, we attempted to change L2 into L1, when the molar ra-
tio of starting material (CuCl2ꢁ2H2O) and L1 ligand is still 1:1, com-
plex 1 was not observed in the absolute methanol system at
ambient temperature. Later, by adding 5 equivalent aliphatic acid
(0.5 mmol), such as oxalic acid, succinic acid, glutaric acid, etc.,

156
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
Scheme 2. The synthetic routes of the ligands L1–L6.
Table 6
0
Selected bond distances (AÅ) and angles (°) of the ligands L3–L5.
Compounds
Cpz–Npz(av)
L3
L4
L5
1.335(8)
1.381(8)
1.360(7)
1.458(8)
1.503(8)
111.4(5)
1.343(7)
1.386(7)
1.362(5)
1.447(5)
1.525(6)
114.1(4)
1.321(3)
1.378(3)
1.365(3)
1.469(3)
1.509(3)
111.79(18)
Cpz–Cpz(av)
N
N
pz–Npz
pz–C–CH2
C
C
ph–C–CH2
ph–C–Npz
tion which seems to affect one of the factors for preparation of
the complexes.
3.2. Crystal structure analysis
3.2.1. Structural description of L3–L5
The asymmetric unit of the compounds L3–L5 is made up of a
half molecule (Fig. 1a–c). In the structures of the compounds, all
carbon atoms of the benzene ring form a good plane, the average
of C–C distances and C–C–C angles from the ring are consistent
with those reported in the literatures [33]. The dihedral angle be-
tween the benzene ring and the pyrazole ring is 76.5(3) for L3,
84. 6(4) for L4 and 74.7(2)° for L5, respectively. In addition, there
is a kind of hydrogen bond (C–HꢁꢁꢁO) in the molecule of L5 between
the carbon (donor) from benzene ring and oxygen (acceptor) from
Scheme 3. The synthetic routes of the complexes 1–5.
we obtained the objective complex 1. Through these experiments,
it is found that aliphatic acid in the reaction process may be as an
important organic structural directing reagent, showing that the
particular role of the molecular reagent in the reaction process
may be a sensitive reaction parameter or participation co-ordina-
Fig. 1. (a) Molecular structure of the compounds (a) for L3, (b) for L4, (c) for L5. (d) A view of a chain structure of L5.(hydrogen atoms are omitted for clarity) (#1: ꢀx+1, ꢀy, ꢀz
for L3; #1: ꢀx+1, ꢀy, ꢀz+1 for L4. #1: ꢀx+2, ꢀy, ꢀz; #2: 1ꢀx, 1ꢀy, ꢀz for L5).

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
157
Fig. 2. (a) Local coordination environment of the Cu(II) atom in the complex 1. (b) A view of a chain structure of the complex 1 (the hydrogen atoms are omitted for clarity)
(#1: 2ꢀx, ꢀy, 2ꢀz; #2: 2ꢀx, 1ꢀy, 1ꢀz).
nitryl group. The molecules are connected by the hydrogen bond
68.8(2)–78.9(1)°. Two Cu(II) atoms are bridged by one L1 ligand
to form a zigzag chain with the CuꢁꢁꢁCu distance of 10.257(1) Å
0
(C7–H7ꢁꢁꢁO2#2, 3.2204 ÅA, 162.62°, #2: 1ꢀx, 1ꢀy,ꢀz) forming an
infinite chain(Fig. 1d). The C–I distances of L3 and L4 are 2.066(6)
(Fig. 2b). Additionally, in the molecular packing, there exists a type
0
0
and 2.073(50) ÅA, respectively. As for L5, the bond length of C–NNO2
of hydrogen bond (C–HꢁꢁꢁCl) (C7–H7AꢁꢁꢁCl3, 3.4919 ÅA, 139.19°;
0
is 1.417(3) ÅA, the average distance of N–O 0 bonds of nitryl group
C11–H11AꢁꢁꢁCl3, 3.478 ÅA, 152.20°), which further enhances the sta-
0
0
is 1.222(3) ÅA (N–O, 1.46 ÅA and N@O, 1.14 ÅA), O–N–O bond angle
is 122.5(2)°.
bility of the molecular structure.
The comparison of the corresponding bond lengths and bond
angles of L3–L5 are listed in Table 6. The average bond distances
of Cpz–Cpz, Npz–Npz and Cpz–Npz from the pyrazole ring are similar
to each other, showing that the different substitution groups
(–NO2, –I) from the pyrazole ring have little influence on the corre-
sponding bond lengths of the compounds. In addition, it is found
that the corresponding bond lengths and angles of Npz–C–CH2,
3.2.2.2. [Cu0.5(L2)0.5Cl]n (2). The asymmetric unit of complex 2 is
made up of a half copper atom, a half of L2 ligand and one chlorine
atom (Fig. 3a). Each Cu(II) atom coordinates to two nitrogen atoms
from two L2 ligands and two chlorine atoms to form a parallelo-
gram geometry coordination environment. The center metal coor-
dination environment of the complex 2 is similar to that of 1. The
0
bond distances of Cu–Npz and Cu–Cl are 1.977(2) and 2.2511(8) ÅA,
respectively. The N–Cu–N bond angle is 180.0° and the angles of
N–Cu–Cl are in the range of 87.36(6)–90.63(6)°. The dihedral angle
of between benzene ring and pyrazole ring is 72.8(2)°. Adjacent
Cph–C–CH2, Cph–C–Npz of L3 and L5 are also close each other, while
that of L4 is slightly bigger than those of L3 and L5. It may be related
to the steric factor of the substituents from the pyrazolyl ring.
copper centers are separated by L2 ligand with a distance of
0
8.840(4) ÅA and extend along an axis to form a makro-radian helical
chain (Fig. 3b). The adjacent chains are further linked by intermo-
lecular weak interactions between carbon atom from benzene rin0g
3.2.2. Structural descriptions of 1–5
3.2.2.1. [Cu(L1)Cl2]n (1). X-ray single crystal diffraction analysis
shows that the asymmetric unit contains one Cu(II) atom, one L1
ligand, and two Cl atoms (Fig. 2a). The Cu(II) atom displays a dis-
torted tetrahedron geometry, and it is coordinated by two nitrogen
atoms (N1, N3) from two L1 ligands and two chlorine atoms(Cl1,
Cl2). L1 links two Cu2+ ions and adopts the bidentate coordination
and the coordinated chlorine atom (C9–H9ꢁꢁꢁCl1#3
, 3.6360 ÅA,
170.83°, #3: x, 1+y, z) to afford a 2D supermolecular network
structure along ab plane (Fig. 3c).
mode. The bond distances of Cu–Npz and Cu–Cl are in the range of
3.2.2.3. [Ag0.5(L2)0.5(NO3)]n (3). The composition of the complex 3 is
similar to that of the complex 2 except that starting material of
CuCl2ꢁ2H2O was replaced by AgNO3. The Ag(I) atom adopts a dis-
torted tetrahedron geometry with two nitrogen atoms from two
0
2.002(2)–2.011(2) and 2.2306(9)–2.2528(9) ÅA, respectively, which
is consistent with those in similar copper complexes [34]. The N–
Cu–N bond angle is 153.41(9)°, the N–Cu–Cl angles are in the range
of 89.27(7)–98.71(7)°. The dihedral angles between the pyrazole
ring and the pyrazole ring/benzene ring are in the range of
L2 ligands and two oxygen atoms from a nitrate group (Fig. 4a).
0
The lengths of Ag–N and Ag–O are 2.210(8) and 2.585(11) ÅA,

158
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
Fig. 3. (a) Local coordination environment of Cu(II) atom in 2; (b) A view of an infinite helical chain along the [010] direction in the complex 2 (the hydrogen atoms are
omitted for clarity); (c) A view of sheet structure formed by the hydrogen bonds linked helical chains in the ab plane.(a part of hydrogen atoms are omitted for clarity) (#1:
ꢀx, y, 0.5ꢀz; #2: 0.5ꢀx, 0.5ꢀy, 1ꢀz; #3: x, 1+y, z).
respectively. The axial bond angle of N–Ag–N is 129.9(4)° and the
bond angles of N–Ag–O are in the range of 108.8(4)–116.9(4)°. The
adjacent Ag atoms are linked through L2 ligand to form a 1D Ag–
L2–Ag polymeric chain along [010] direction (Fig. 4b). These paral-
binuclear unit featuring a 16-membered ring with the average of
the ZnꢁꢁꢁZn distance of 8.65 Å. The dihedral angles between pyraz-
olyl ring and phenyl ring are 86.3(9) and 86.9(9)°, respectively. The
dihedral angle between two pyrazolyl rings is 80.9(5)°. The poly-
lel chains are further connected by the hydrogen bond of C6–
mer chain propagates via b-glide (Fig. 5b), and by the C–HꢁꢁꢁS
0
0
H6BꢁꢁꢁO2 [C6–H6BꢁꢁꢁO2#3, 3.3672 ÅA, 152.70°, #3: 1ꢀx, ꢀy, ꢀz;
hydrogen bond (C5–H5AꢁꢁꢁS2#3
,
#3: ꢀx, 1ꢀy, 1ꢀz, 3.7670 ÅA,
0
0
C6#4–H6B#4ꢁꢁꢁO2#3, 3.3672 ÅA, 152.70°, #4: 1ꢀx, y, ꢀ1/2ꢀz] to give
155.05°; C11–H11ꢁꢁꢁS2#4, 3.6100 ÅA, 139.67°, #4: 1+x, y, z), further
a layer in the ac plane (Fig. 4c). When viewed along the [100]
to form an intercross-hydrogen bonding network (Fig. 5c).
-
direction, the NO3 further linked these layers to construct a 3D
supermolecular network (Fig. 4d).
3.2.2.5. [Cd(L2)0.5(SCN)2]n (5). The asymmetric unit of 5 contains
one Cd(II) atom, a half L2 ligand and two thiocyanate ions, de-
scribed as a distorted trigonal bipyramidal geometry (Fig. 6a).
The Cd center is surrounded by two N atoms and two S atoms from
four NCS groups, and one N atom from L2 ligand (Cd–N: 2.270(4)–
2.297(3) Å; Cd–S: 2.609(1), 2.735(1) Å)). Each two NCS groups bind
to two adjacent Cd2+ by the bridging bidentate coordination mode
to form a helix-chain with the CdꢁꢁꢁCd distance of 5.772(2) and
5.738(2) Å, respectively (Fig. 6b). The helix-chain is further
3.2.2.4. [Zn(L2)(SCN)2]n (4). The Zn(II) atom adopts a distorted tet-
rahedral geometry with four nitrogen atoms (N1, N2, N4, N5) from
pyrazolyl rings of two L2 ligands and two thiocyanate groups,
respectively (Fig. 5a). The bond lengths of Zn(II)–Npz and Zn(II)–
0
NSCN are 2.019(9)/2.053(9) and 1.934(10)/1.964(11) ÅA, respectively.
Analysis of molecular conformation reveals two [Zn(SCN)2] units
are linked by one L2 ligand in a trans-conformation to afford a

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
159
Fig. 4. (a) Local coordination environment of the Ag(I) atom in 3; (b) a wavelike chain viewed along [010] direction in the complex 3. (the hydrogen atoms are omitted for
clarity); (c) sheet structure formed by hydrogen bond of C6–H6BꢁꢁꢁO2 linked parallel chains in the ac plane; (d) The 3D packing framework of the complex 3. (a part of
hydrogen atoms are omitted for clarity)(#1: ꢀx+1, y, ꢀz+1/2; #2: 3/2ꢀx, 1/2ꢀy, z; #3: 1ꢀx, ꢀy, ꢀz; #4: 1ꢀx, y, ꢀ1/2ꢀz).
bridge-linked by L2 ligand to generate a laminated polymer
(Fig. 6c).
stretching vibrations of nitro-group, respectively. In addition, the
detailed appointment of the IR spectra data for ligands L1–L6 is
shown in Table S1. Comparison of IR characterization for L1–L6
found that the stretching vibration frequency of ‘‘@C–H’’ for pyraz-
olyl moiety are slightly larger than those of 3,5-di-methyl-pyrazol-
yl moiety, and the stretching vibration of @C–H for L1, L5 splits into
two peaks (3116 and 3090 cmꢀ1 for L1, 3119 and 3139 cmꢀ1 for L5).
The IR spectra data of the complexes 1–5 (Fig. S7–11) was listed
in Table S2. It is clearly found that stretching vibrations of C–
H(@C–H, –CH3, –CH2) is in the range of 3132–3030 cmꢀ1. The
strong peaks in the range of 1636–1022 cmꢀ1 account for the
appearance of C@C, C@N of the pyrazole and benzene rings, which
generate slightly blue shift through comparison of that of corre-
sponding to the ligands. For complex 3, the characteristic bands
3.3. IR spectra
The IR spectra of the ligands L1–L6 (Fig. S1–6) exhibit weak
absorption bands in the range of 3139–3030 cmꢀ1 and strong
absorption bands in the range of 824–797 cmꢀ1, indicating the
presence of the C–H(@C–H) stretching vibrations and bending
vibrations, respectively. Absorption bands at 2995–2851 cmꢀ1
should be assigned to the stretching vibrations of the C–H (–CH3,
–CH2). The bands in the region of 1638–999 cmꢀ1 are attributed
to the aromatic skeleton stretching vibration of the pyrazolyl and
benzene rings. As for L3 and L4, the bands at 608 and 595 cmꢀ1
are characteristic of C–I. As for L5 and L6, the peaks at 1530,
1561, 1328 and 1356 cmꢀ1 are due to asymmetry and symmetry
of NO3 anion are shown at 1552 cmꢀ1 for asymmetric stretching
ꢀ
vibrations and 1384 cmꢀ1 for symmetric stretching vibrations,

160
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
Fig. 5. (a) Local coordination environment of the Zn(II) atom in 4; (b) 1D Zn–L2–Zn polymeric chain of the complex 4 along [010] direction; (c) a intercross-hydrogen bonding
network formed by the hydrogen bonds(C–HꢁꢁꢁS) in the ab plane. (a part of hydrogen atoms are omitted for clarity)(#1: ꢀx, ꢀy, 1ꢀz; #2: 1ꢀx, 1ꢀy, 1ꢀz; #3: ꢀx, 1ꢀy, 1ꢀz; #4:
1+x, y, z).
which is agreement with those of the related Ag complexes [35].
There are sharp and strong absorption bands in the region of
2083–2125 cmꢀ1 for 4 and 5, which is assigned to the asymmetric
stretching frequency of the thiocyanate groups. While stretching

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
161
Fig. 6. (a) Local coordination environment of the Cd(II) atom in 5; (b) helical chain is formed through the two thiocyanate bridging the Cd(II) atoms along [001] direction in
complex 5 (a part of hydrogen atoms and SNC groups are omitted for clarity); (c) ladder-like tapes layer in the ab plane. (a part of hydrogen atoms are omitted for clarity)(#1:
ꢀx+2, ꢀy, ꢀz+1; #2: ꢀx+2, ꢀy+1, ꢀz; #3: ꢀx+2, ꢀy, ꢀz).
vibration of thiocyanate group for complex 5 splits into two strong
peaks, this is because there are two types of coordination environ-
ment of the thiocyanate group.
Additionally, the compositions of complexes 1–5 were con-
firmed by elemental analysis and X-ray powder diffraction (PXRD)
was used to confirm the phase purity of the bulk materials
(Fig. S12–16). The experiment results prove that all the peaks pre-
sented in the measured patterns closely match the simulated pat-
terns generated from single crystal diffraction data.
found that the proton resonances of pyrazolyl ring of nitro
substituted compounds (L5 and L6) move obviously to downfield,
the signals of H4-pz of L2 move to upfield (5.82 ppm for L2;
6.26 ppm for L1). Similarly, the signals in 13C NMR spectra of
ligands L1–L6 are divided into three groups according to the dif-
ferent substituted group on C4: (i) 106.02 ppm for L1 and
105.53 ppm for L2, are assigned to no substituted group on C4;
(ii) the chemical shift of 4-iodo-substituted compounds
(56.62 ppm for L3 and 63.27 ppm for L4) in upfield; (iii) the sig-
nals of 4-nitro-substituted compounds (135.04 ppm for L5 and
131.60 ppm for L6) in downfield. 1H and 13C NMR spectra of
complexes 1–5 (Table S5 and S6, Fig. S30–39) were recorded
in CDCl3 or DMSO-d6. The chemical shift of 1H NMR spectra of
the complex 1 and 2 due to ligands being coordinated to copper
atom to turn in considerably broad, which seems to indicate that
the copper complexes are paramagnetic. Compared with
chemical shift of the corresponding ligands, the chemical shift
3.4. 1H NMR spectra
The structures of these compounds (L1–L6) were further con-
l
firmed by H and 13C HMR spectra through comparison with the
spectra of the related compounds [36]. 1H and 13C NMR spectra
of ligands L1–L6 (Table S3 and S4, Fig. S18–29) were recorded in
CDCl3 or DMSO-d6. According to chemical shift of proton, it is

162
X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
of H4-pz of complexes1–3 move to downfield, however, that of
complexes 4 and 5 containing SCN groups went on upfield.
The 13C NMR spectra of all complexes are very similar and it
is almost not any influence on the compounds and the
complexes.
rigidity of the ligand and the reduction of the loss of energy
through a radiationless pathway [46], while, the emission of com-
plexes 3–5 occurs red-shifted or blue-shifted, which is probably
due to the different coordination modes and the metal centre with
the same ligand.
3.7. Thermal properties
3.5. UV–Vis absorption spectra
To examine the thermal stability of the coordination polymers,
thermogravimetric analyses (TGA) were carried out under N2
atmosphere of the complexes 1–5 (Fig. 8) in the temperature
range of 25–1000 °C. The TGA curve of 1 shows that the weight
loss of 63.34% between 152 and 714 °C is attributed to the release
of the organic ligand (Calc. 64.10%), the residue is copper chloride
(obsd: 34.41%; Calc.: 36.07%). The first weight loss in the complex
2 occurs in the range 217–335 °C, implying the removal of the
3,5-dimethyl-1H-pyrazole and methylene (obsd: 48.06%, Calc.:
47.17%). The second weight loss of 16.83% occurs in the temper-
ature range of 350–442 °C, which is ascribed to the release of the
benzene ring (Calc. 17.76%). Finally, the residue is corresponding
copper nitride (obsd: 14.35%; Calc.: 17.00%). In the complex 3, the
result shows a first major weight loss equal to 64.20% in the
range 206–299 °C, ascribed to the release of organic ligands (Calc.
63.41%). So, the framework is stable up to 206 °C, at which point
the removal of nitrate radical can ensue. The residue is corre-
sponding to silver oxide (obsd: 25.31%; Calc.: 24.96%). Complex
4–5 can keep the stability before 202 °C, and then the pyrazolyl
ring, methylene, benzene ring and thiocyanate collapse slowly
in turn. The decomposition of the remaining substance finished
at 860 °C. Finally, the residue corresponds to zinc nitride and cad-
The electronic absorption spectra of the complexes 1–5 are re-
corded. As shown in Fig. S40. Bands at 208 nm for 1, 206 nm for
2, 206 nm for 3, 208 nm for 4 and 212 nm for 5 are attributed to
the p– p–
p⁄ transition of the ligands. Compared with the p⁄ transi-
tion of the ligand L2 (214 nm), it is found that the characterization
absorption bands of the complexes 2–5 move slightly to blue-shift.
The band at 404 nm for 1 and 422 nm for 2 are assigned to the
charge transitions from the ligands to Cu(II) atom (LMCT) of
N ? Cu. The broad peak at 780 nm for 1 and 610 nm for 2 can be
caused by the d ? d⁄ transition of Cu2+ cation, respectively [37].
3.6. Luminescent properties
The fluorescence of inorganic-organic coordination polymers
especially those with the d10 metal center [38,39], is drawing sig-
nificant attention for their potential applications as fluorescent-
emitting materials, such as light-emitting diodes (LEDs) [40–42].
Hereupon, it is necessary to investigate the photoluminescent
property with the d10 metal coordination polymers. In general, as
for the d10 metal centers of the Ag(I), Zn(II) or Cd(II), the emission
band of these complexes may be assigned to the LLCT, incorpora-
tion with MLCT and LMCT [43–45]. The photoluminescence prop-
erties of complexes 3–5 and ligand (L2) were studied in the solid
state at room temperature (Fig. 7). It is found that emission bands
are observed at 301 and 417 nm ((kex = 260 nm) for L2, which can
100
80
be ascribed to the p⁄ ? n or p⁄
? p transitions of the organic li-
gand. An intense emission peak (432 nm) of complex 4 at the exci-
tation wavelength of 378 nm with slit width (3:1) is observed, and
a phenomena of red shift 15 nm occurred as compared with that of
the L2 ligand (kem = 417 nm). Strong emission bands in the range of
370–385 nm (kex = 341 nm) and 368–383 nm (kex = 324 nm) are
exhibited for the complexes 3 and 5, which occurred a blue-shifted
as compared with the L2 ligand (kem = 417 nm), respectively. The
results above match with the absorption spectra of the complexes.
The enhancement of luminescence in complexes 3–5 compared
with free ligand L2 may be attributed to the enhancement of the
60
2µmolL-1
20µmolL-1
40
200µmolL-1
20
0
L1
L2
L4
L6
Fig. 8. Effect of the different concentration of the compounds L1–L6 on the viability
of hepG2 cell.
100
80
60
2µmolL-1
40
20µmolL-1
200µmolL-1
20
0
1
2
3
4
5
Fig. 7. Solid-state emission spectra of complexes 1–5 and the ligand L2 at room
temperature.
Fig. 9. Effect of the concentration of complexes 1–5 on the viability of hepG2 cell.

X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
163
Fig. 10. HepG-2 cells were incubated with various concentrations of complex 2 for 24 h. (A) normal cell (B) 2 lmol/L (C) 20 lmol/L (D) 200 lmol/L.
mium nitride (obsd: 15.31%, 31.49% for 4; Calc.: 13.74%, 29.91%
for 5).
The effects of the various concentrations of the compound in-
duced apoptosis in hepG-2 cells. For instance, hepG2 cells were
incubated with various concentrations of complex 2 for 24 h
(Fig. 9). This figure shows the complex 2 treated cells narrowed
to go round and chromatin condensed, suggesting they are under-
going apoptosis (see Fig. 10).
3.8. Statistical analysis
Results are expressed as x s. Statistical differences were deter-
mined between groups by one-way analysis of variance (ANOVA)
and Tukey’s multiple comparison test. Statistically significant
differences between groups were defined as P < 0.05. Calcula-
tions were performed with the Graph Pad and Prism program
(Table S7).
4. Conclusion
In conclusion, a new series of M–L2–M coordination polymers
were synthesized and characterized for the first time. X-ray diffrac-
tion results that the layer structure and 3D microporous frame-
work of all the complexes were constructed by the different
ligands and metal atoms. Although the ligand displays the same
conformation and coordination mode, introducing of the small
molecular organic reagent leads to form various coordination
modes and play a key role in the construction of the high dimen-
sional architecture. Simultaneously, the photoluminescence
behaviours analysis of the different structures are theoretically sig-
nificant for understanding of the relationship between the struc-
tures and photoluminescence properties of the complexes. The
study results show that the complexes 3–5 seem to be good candi-
dates for novel hybrid inorganic–organic photoactive materials.
Furthermore, the cytotoxicity of the ligands and complexes 1–5
was evaluated against hepG2 cells. The results showed that the
complexes 1–5 provoke cell death obviously increased than the
corresponding ligands. Finally, these interesting materials hint us
to further research the rational synthetic strategy for obtaining
new complexes with potential bioactivity properties and multiple
structures.
3.9. Biological assays
The cytotoxicity of synthesized compounds L1–L6 and com-
plexes 1–5 were evaluated using a 24 h continuous exposure
against hepG2 cells in vitro at several concentrations (Figs. 7 and
8). The results showed that most compounds can suppress hepG2
cell growth. It presents the differences for a variety of compounds
according to some extent of the restriction on the growth of hepG2
cells. The rate of inhibition enhances with the concentration of
compound increasing. Among ligands, L3 and L5 precipitate at only
2
200
l
mol Lꢀ1. L2 causes 9, 16 and 28% of cell death at 2, 20 and
l
mol Lꢀ1, respectively. Similar behavior was observed for
other ligands. The Research found that the substitute of the pyraz-
olyl ring strongly influenced the cytotoxicity of the compounds.
The nitro-substituted compounds are higher inhibiting than the
other group substituted compounds at 2 l
mol Lꢀ1. For complexes
1–5, the complexes provoke cell death obviously increased than
the corresponding ligands. Therefore, the particular role of metals
in cytotoxicity may be as an important inhibitory reagent. In addi-
tion, it can be seen that different metals have different influence on
hepG2 cell growth when the ligand in the complexes is the same,
Acknowledgements
especially, at 2
l
mol Lꢀ1, there are 99% cell death in the complex
This work was supported by the grants of the National Natural
Science Foundation of China (Grant No. 21071071) and State Key
Laboratory of Inorganic Synthesis and Preparative Chemistry, Col-
3, because silver ion is more powerful to strengthen the cell mem-
brane damage.

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X.-Y. Wang et al. / Polyhedron 47 (2012) 151–164
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Appendix A. Supplementary data
CCDC 833039(L3), 833043(L4), 833044(L5), 833048(1),
833049(2), 833041(3), 833050(4) and 833040(5); contains the
supplementary crystallographic data for L3–L5 and complexes 1–
5. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2012.08.016.
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