Non-covalently bonded 2D-3D metal-organic frameworks from the reactions of Cd(II) and Zn(II) with 3,5-dimethylpyrazole and carboxylate ligands

Article abstract of DOI:10.1016/j.poly.2013.04.056

Seven new complexes, namely Cd(Hdmpz)₂(L1)₂ (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = N-phenylmaleamate), Cd(Hdmpz) ₄(L2)₂ (2) (L2 = 1,3-benzodioxole-5-carboxylate), Zn ₂(μ-dmpz)₂(Hdmpz)₂(L3)₂ (3) (L3 = 2-chloronicotinate), Zn(Hdmpz)₂(L4)₂ (4) (L4 = 3,5-dinitrobenzoate), Zn(Hdmpz)₂(HL5)₂ (5) (HL5 = 5-chlorosalicylate), Cd(Hdmpz)₂(HL6) (6) (HL6 = 5-sulfosalicylate) and Cd₂(Hdmpz)₄(L7)₂ (7) (L7 = maleate), have been synthesized from the self-assembly of the Zn/Cd ions, 3,5-dimethylpyrazole and carboxylate ligands at room temperature. All the complexes were structurally characterized by different techniques, including elemental analysis, IR spectra, TG and single crystal X-ray diffraction analysis. The X-ray studies suggest that these complexes display mononuclear to dinuclear structures with a tetrahedral geometry around each zinc center, and an octahedral geometry around each cadmium center. The pyrazole ligands in all the compounds except compound 3 are coordinated only in the monodentate fashion by its neutral N group. In 2, 3, 4, 5 and 6, the carboxylate groups behave as monodentate ligands. The COO^- group in 1 and the SO₃^- group in 6 both coordinate to the metal in a chelating bidentate fashion. The carboxylates in 7 functioned as a tetradentate bridging ligand. The uncoordinated oxygen atom of the carboxylate group in all of the compounds forms intramolecular hydrogen bonds with the N-H group of the coordinated 3,5-dimethylpyrazole ligand. On the basis of the X-ray crystallographic study, the rich intra- and intermolecular non-covalent interactions, such as classical hydrogen bonds, CH-Cl, CH ₃-Cl, Cl?Cl, Cl?O, C-H?O, CH₃? O, C-H?π, CH₂?π, CH₃-π, O-π and π-π interactions, are analyzed. The various non-bonding interactions in these compounds are responsible for different structures, such as sheet, 3D network and 3D layer structures. The thermal stabilities of 1-7 were examined and the results show that the complexes seem to be good candidates for novel hybrid inorganic-organic materials with good thermal stability.

Full text of DOI:10.1016/j.poly.2013.04.056

Polyhedron 60 (2013) 10–22
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Non-covalently bonded 2D–3D metal–organic frameworks from the
reactions of Cd(II) and Zn(II) with 3,5-dimethylpyrazole and carboxylate
ligands
a
b
a
a
a
a
Shou-wen Jin a, , Yanfei Huang , Da-qi Wang , Hao Fang , Tianyi Wang , Peixia Fu , Liangliang Ding
⇑
a Tianmu College ZheJiang A & F University, Lin’An 311300, PR China
b Department of Chemistry, Liaocheng University, Liaocheng 252059, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Seven new complexes, namely Cd(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = N-phenylma-
leamate), Cd(Hdmpz)4(L2)2 (2) (L2 = 1,3-benzodioxole-5-carboxylate), Zn2( -dmpz)2(Hdmpz)2(L3)2 (3)
Received 4 January 2013
Accepted 27 April 2013
Available online 10 May 2013
l
(L3 = 2-chloronicotinate), Zn(Hdmpz)2(L4)2 (4) (L4 = 3,5-dinitrobenzoate), Zn(Hdmpz)2(HL5)2 (5)
(HL5 = 5-chlorosalicylate), Cd(Hdmpz)2(HL6) (6) (HL6 = 5-sulfosalicylate) and Cd2(Hdmpz)4(L7)2 (7)
(L7 = maleate), have been synthesized from the self-assembly of the Zn/Cd ions, 3,5-dimethylpyrazole
and carboxylate ligands at room temperature. All the complexes were structurally characterized by dif-
ferent techniques, including elemental analysis, IR spectra, TG and single crystal X-ray diffraction analy-
sis. The X-ray studies suggest that these complexes display mononuclear to dinuclear structures with a
tetrahedral geometry around each zinc center, and an octahedral geometry around each cadmium center.
The pyrazole ligands in all the compounds except compound 3 are coordinated only in the monodentate
fashion by its neutral N group. In 2, 3, 4, 5 and 6, the carboxylate groups behave as monodentate ligands.
Keywords:
Structure
Supramolecules
3,5-Dimethylpyrazole
Carboxylate
Non-covalent bonding interactions
The COOꢀ group in 1 and the SO3 group in 6 both coordinate to the metal in a chelating bidentate fash-
ꢀ
ion. The carboxylates in 7 functioned as a tetradentate bridging ligand. The uncoordinated oxygen atom
of the carboxylate group in all of the compounds forms intramolecular hydrogen bonds with the N–H
group of the coordinated 3,5-dimethylpyrazole ligand. On the basis of the X-ray crystallographic study,
the rich intra- and intermolecular non-covalent interactions, such as classical hydrogen bonds, CH–Cl,
CH3–Cl, Clꢁ ꢁ ꢁCl, Clꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁO, CH3ꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁ
p
, CH2ꢁ ꢁ ꢁ
p, CH3–p, O–p and p–p interactions, are ana-
lyzed. The various non-bonding interactions in these compounds are responsible for different structures,
such as sheet, 3D network and 3D layer structures. The thermal stabilities of 1–7 were examined and the
results show that the complexes seem to be good candidates for novel hybrid inorganic–organic materials
with good thermal stability.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
ions and the functionality of the ligands. Aside from the coordina-
tion bonding interactions, hydrogen bonding, p–p stacking interac-
Metal coordination polymers have attracted great current inter-
est in coordination chemistry because of their intriguing structures
and potential as functional materials [1–3]. Studies in this field
have been focused on the design and construction of novel coordi-
nation frameworks and the relationships between their structures
and properties. It is still a great challenge to predict the exact
structures and compositions of the assembly products built by
coordination bonds and/or hydrogen bonds in crystal engineering.
The framework structure of the coordination polymers is primarily
dependent upon the coordination preferences of the central metal
tions, solvent molecules, counterions and the ratio of the metal salt
to the organic ligand also influence the formation of the ultimate
architectures. Therefore, systematic research on this topic is still
important for understanding the roles of these factors in the for-
mation of metal coordination frameworks.
Research on metal carboxylates has always been intriguing in
that they play important roles not only in synthetic chemistry,
with the essence of the labile coordination modes of the carboxyl-
ate group and having architectures such as open and porous frame-
works [4,5], but also for their biologic activities [6,7] and
physiological effects [8,9]. A versatile carboxylate anion can adopt
a wide range of bonding modes, including monodentate, symmet-
ric and asymmetric chelating, and bidentate and monodentate
bridging [10].
⇑
Corresponding author. Tel./fax: +86 571 6374 6755.
E-mail address: jinsw@zafu.edu.cn (S.-w. Jin).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.04.056

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
11
Pyrazole and its derivatives have been widely employed in
2.2. Synthesis of the complexes
polypyrazolylborates to stabilize a variety of organometallic and
coordination compounds [11,12]. Up until now, a variety of com-
plexes containing pyrazole (Hdmpz) ligands have been synthesized
and employed in coordination chemistry or organometallic chem-
istry [13–15]. Many complexes with simple pyrazole ligand, both
in the terminal as well as the bridging mode, are also available
[16–18], but complexes with the presence of both carboxylic acids
and pyrazole derivatives are not very common, except for some re-
cently reported examples in the literature [19]. We have been
working on coordination compounds with mixed carboxylate and
pyrazole derivative ligands [20]. The pyrazole ligand and the car-
boxylate ligand appear to possess similar steric requirements
and, to a certain extent, similar bonding capabilities. In order to
understand the influence of the carboxylate residue in the forma-
tion of new complexes and the role weak non-covalent interactions
play in forming the final supramolecular frameworks, we selected
carboxylic acids bearing the NH, CONH, OH, Cl, NO2 and SO3H
units, which are good groups for forming hydrogen bonds and
some other non-bonding interactions [21]. Thus, in the following
we report the synthesis, structural characterization and thermal
behavior of Zn and Cd complexes of a combination of 3,5-dimeth-
ylpyrazole (Hdmpz) and different carboxylate ligands (Scheme 1),
namely Cd(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5-dimethylpyrazole,
L1 = N-phenylmaleamate), Cd(Hdmpz)4(L2)2 (2) (L2 = 1,3-benzodi-
2.2.1. Synthesis of Cd(Hdmpz)2(L1)2 (1)
A solution of Cd(CH3COO)2ꢁ2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (12 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and N-phenylmaleamic acid (HL1) (0.0765 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colorless crystals formed, which were
filtered off, washed with MeOH and dried under vacuum to afford
0.0510 g of the product. Yield: 74.45% (Based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere: Calc.
for C30H32CdN6O6 (685.02): C, 52.55; H, 4.67; N, 12.26. Found: C,
52.49; H, 4.61; N, 12.22%. IR (KBr disc, cmꢀ1): 3421w (
3267m ( s(NH)), 3097m, 2986m, 2876m, 1662s (C@O), 1623s (
COO)), 1494s ( s(COO)), 1446m, 1390m, 1333m, 1276m, 1235m,
m
as(NH)),
m
m
as(-
m
1171m, 1085m, 1024m, 969m, 888m, 814m, 756m, 712m, 663m,
619m.
2.2.2. Synthesis of Cd(Hdmpz)4(L2)2 (2)
A solution of Cd(CH3COO)2ꢁ2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to an EtOH solution (8 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 1,3-benzodioxole-5-carboxylic acid (HL2)
(0.0664 g, 0.4 mmol), under continuous stirring. The solution was
stirred for about 2 h at room temperature and the solution became
turbid. Afterwards, a few drops of conc. ammonia were added until
the solution became clear. The solution was filtered into a test tube
and after several days colorless crystals were formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0330 g of the product. Yield 79.79% (based on Hdmpz). Elemental
analysis performed on crystals exposed to the atmosphere: Calc for
oxole-5-carboxylate), Zn2(l-dmpz)2(Hdmpz)2(L3)2 (3) (L3 = 2-
chloronicotinate), Zn(Hdmpz)2(L4)2 (4) (L4 = 3,5-dinitrobenzoate),
Zn(Hdmpz)2(HL5)2 (5) (HL5 = 5-chlorosalicylate), Cd(Hdmpz)2(-
HL6) (6) (HL6 = 5-sulfosalicylate) and Cd2(Hdmpz)4(L7)2 (7)
(L7 = maleate).
2. Experimental section
C
36H42CdN8O8 (827.18): C, 52.23; H, 5.08; N, 13.54. Found: C,
52.19; H, 4.99; N, 13.45%. IR (KBr): 3417w ( as(NH)), 3243w ( s(-
NH)), 2932m, 2668m, 2554m, 2519m, 2335m, 1716m, 1623s ( as(-
COO)), 1575m, 1534m, 1476m, 1440m, 1415s ( s(COO)), 1372m,
1313m, 1258m, 1155m, 1095m, 1027m, 888m, 849m, 806m,
767m, 668m, 622m.
2.1. Materials and physical measurements
m
m
m
The chemicals and solvents used in this work are of analytical
grade and available commercially and they were used without fur-
ther purification. The FT-IR spectra were recorded from KBr pellets
in the range 4000–400 cmꢀ1 on a Mattson Alpha-Centauri spec-
trometer. Microanalytical (C, H, N and S) data were obtained with
a Perkin–Elmer Model 2400II elemental analyzer. Thermogravi-
metric analyses (TGA) were studied by a Delta Series TA-SDT
Q600 in a N2 atmosphere between room temperature and 800 °C
(heating rate10 °C minꢀ1) using Al crucibles.
m
2.2.3. Synthesis of Zn2(l-dmpz)2(Hdmpz)2(L3)2 (3)
A solution of Zn(CH3COO)2ꢁ2H2O (0.0220 g, 0.1 mmol) in 5 mL
of EtOH was added to a MeOH solution (10 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 2-chloronicotinic acid (HL3) (0.0628 g,
NO2
Cl
HO
O
N
OH
O
HO
O
H
N
O
O
O
NO2
HO
O
HL4
HL3
HL2
HL1
HO
O
HO
OH
O
O
O
HO
O
OH
S
N
NH
OH
HO
O
Cl
H3L6
Scheme 1. The ligands used in this paper.
H2L5
H2L7
Hdmpz

12
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, a small amount of precipitate
formed, then a few drops of conc. ammonia were added until the
precipitate dissolved completely. The clear solution was filtered
into a test tube and after several days colorless block crystals
formed, which were filtered off, washed with MeOH and dried un-
der vacuum to afford 0.0320 g of the product. Yield: 77.45% (Based
on Hdmpz). Elemental analysis performed on crystals exposed to
the atmosphere: Calc. for C32H36Cl2N10O4Zn2 (826.35): C, 46.47;
H, 4.36; N, 16.94. Found: C, 46.41; H, 4.27; N, 16.89%. IR (KBr disc,
(KBr disc, cmꢀ1): 3584s (
3139m, 2951m, 2867m, 1669s (
1297s ( (C–O)), 1267m, 1226m, 1165m, 1093m, 1036m, 936v,
m
(OH)), 3466m (
mas(NH)), 3257m (ms(NH)),
m(C@O)), 1539m, 1488m, 1361m,
m
889m, 823v, 749m, 677m, 611v.
2.2.7. Synthesis of Cd2(Hdmpz)4(L7)2 (7)
A solution of Cd(CH3COO)2ꢁ2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (10 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and maleic acid (H2L7) (0.0232 g, 0.2 mmol),
under continuous stirring. The solution was stirred for 2 h at room
temperature, the solution became turbid, then a few drops of conc.
ammonia were added until the solution became clear. The clear
solution was filtered into a test tube and after several days color-
less block crystals formed, which were filtered off, washed with
MeOH, and dried under vacuum to afford 0.0320 g of the product.
Yield: 76.42% (based on Hdmpz). Elemental analysis performed on
crystals exposed to the atmosphere: Calc. for C28H36Cd2N8O8
(837.45): C, 40.12; H, 4.30; N, 13.37. Found: C, 40.06; H, 4.26; N,
cmꢀ1): 3435w (
2874m, 1617s (
s(COO)), 1375m, 1293m, 1235m, 1178m, 1064m, 1013m, 969m,
mas(NH)), 3269w (
ms(NH)), 3146m, 3062m, 2953m,
mas(COO)), 1582m, 1551m, 1503m, 1456m, 1426s
(m
856m, 798m, 753m, 698m, 647m, 610m.
2.2.4. Synthesis of Zn(Hdmpz)2(L4)2 (4)
A solution of Zn(CH3COO)2ꢁ2H2O (0.0220 g, 0.1 mmol) in 5 mL
of EtOH was added to a MeOH solution (12 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 3,5-dinitrobenzoic acid (HL4) (0.0848 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colorless crystals formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0540 g of the product. Yield: 79.43% (Based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere: Calc.
for C24H22N8O12Zn (679.87): C, 42.36; H, 3.24; N, 16.47. Found: C,
13.31%. IR (KBr disk, cmꢀ1): 3456m (
3161w, 3067w, 2983m, 2864m, 2575m, 2519m, 2328m, 1625m,
mas(NH)), 3254w (ms(NH)),
1570s (m ms(-
as(COOꢀ)) 1547m, 1513m, 1463m, 1416m, 1383s (
COOꢀ)), 1275m, 1229m, 1163w, 1120w, 1047m, 1006m, 945m,
888m, 834m, 791w, 714m, 692m, 644m, 604m.
2.3. X-ray crystallography
Suitable crystals were mounted on a glass fiber on a Bruker
SMART 1000 CCD diffractometer operating at 50 kV and 40 mA
42.29; H, 3.18; N, 16.45%. IR (KBr disc, cmꢀ1): 3462br (
3273m ( s(NH)), 3154m, 3076m, 2993m, 2975w, 2871m, 1621s
as(COO)), 1583m, 1525s ( as(NO2)), 1464m, 1422s ( s(COO)),
1381m, 1319s ( s(NO2)), 1283m, 1242m, 1173m, 1112m, 1066m,
mas(NH)),
using Mo K
a radiation (0.71073 Å). Data collection and reduction
m
were performed using SMART and SAINT software [22]. The structures
were solved by direct methods, and the non-hydrogen atoms were
subjected to anisotropic refinement by full-matrix least squares on
F2 using the SHELXTL package [23]. Hydrogen atom positions for all of
the structures were found in a difference map. Further details of
the structural analysis are summarized in Tables 1 and 2. Selected
bond lengths and angles for complexes 1–7 are listed in Table 3,
and the relevant hydrogen bond parameters are provided in
Table 4.
(m
m
m
m
975m, 891m, 843m, 790m, 738m, 677m, 636m, 604m.
2.2.5. Synthesis of Zn(Hdmpz)2(HL5)2 (5)
A solution of Zn(CH3COO)2ꢁ2H2O (0.0220 g, 0.1 mmol) in 5 mL
of EtOH was added to an EtOH solution (4 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 5-chlorosalicylic acid (H2L5) (0.0690 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colorless crystals formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0490 g of the product. Yield: 81.57% (Based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere: Calc.
for C24H24Cl2N4O6Zn (600.74): C, 47.94; H, 3.99; N, 9.32. Found: C,
3. Results and discussion
3.1. Preparation and general characterization
Complexes 1–7 were prepared in MeOH or EtOH at room tem-
perature via the combination of the metalate acetate, Hdmpz,
and the corresponding carboxylic acid. The corresponding crystals
suitable for X-ray crystallography analysis were grown upon addi-
tion of a few drops of conc. ammonia solution, giving yields of
74.45–86.40%.
47.89; H, 3.92; N, 9.22%. IR (KBr disc, cmꢀ1): 3497m (
3286m s(NH)), 3089m, 2947m, 2869m, 1604s as(COO)),
1553m, 1400s ( s(COO)), 1331m, 1274m, 1211m, 1167m, 1075m,
mas(NH)),
(m
(m
m
986m, 912m, 842m, 768m, 716m, 668m, 605m.
During the reaction, the acetate ligand has been substituted by
the corresponding carboxylate ions. In 1, 2, 4, 5, 6 and 7 only the
pyrazole group exists, while 3 possesses both the pyrazole and
the pyrazolate units. These compounds are not soluble in most
common solvents. The infrared spectra of 1–7 were consistent with
their molecular compositions. Compound 1 contains a carboxyl
2.2.6. Synthesis of Cd(Hdmpz)2(HL6) (6)
A solution of Cd(CH3COO)2ꢁ2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (7 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 5-sulfosalicylic acid dihydrate (H3L6)
(0.1016 g, 0.4 mmol), under continuous stirring. The solution was
stirred for about 2 h at room temperature, the solution became tur-
bid, then a few drops of conc. ammonia were added until the solu-
tion became completely clear. The clear solution was filtered into a
test tube and after several days colorless block crystals formed,
which were filtered off, washed with MeOH and dried under vac-
uum to afford 0.0450 g of the product. Yield: 86.40% (Based on
Hdmpz). Elemental analysis performed on crystals exposed to the
atmosphere: Calc. for C17H20CdN4O6S (520.83): C, 39.17; H, 3.84;
N, 10.75; S, 6.14. Found: C, 39.13; H, 3.78; N, 10.67; S, 6.07%. IR
group with the chelating bidentate coordination mode, with
CO2) and
s(CO2) bands at 1623 and 1494 cmꢀ1 respectively (with
value of 129 cmꢀ1). The IR spectra of 2–5 display characteristic
carboxylate bands in the range 1604–1623 cmꢀ1 for
as(CO2) and
1400–1426 cmꢀ1 for
s(CO2) [24]. The frequency differences be-
tween as(CO2) and
s(CO2) are in the range 191–208 cmꢀ1 for
mas(-
m
a
D
m
m
m
m
compounds 2–5. This suggests a unidentate coordination mode
for the carboxylate ligands infs compounds 2–5. Compound 6 dis-
plays strong IR peaks for COOH groups. There are coordinated neu-
tral Hmdpz ligands in all of the seven compounds, which is further

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
13
Table 1
Summary of X-ray crystallographic data for complexes 1–3.
1
2
3
Formula
Formula weight
T (K)
C
30H32CdN6O6
C36H42CdN8O8
827.18
298(2)
C32H36Cl2N10O4Zn2
826.35
298(2)
685.02
298(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
monoclinic
C2
18.4619(17)
7.9510(5)
12.0791(11)
90
120.123(2)
90
1533.6(2)
2
0.71073
triclinic
P1
0.71073
monoclinic
P2(1)/n
8.6544(8)
14.5510(16)
14.6941(14)
90
91.9380(10)
90
1849.4(3)
2
1.484
1.492
848
ꢀ
9.0250(8)
10.6849(9)
10.9631(11)
74.4380(10)
85.208(2)
74.6380(10)
981.95(16)
1
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc. (Mg/m3)
Absorption coefficient, mmꢀ1
F(000)
1.483
0.764
700
1.399
0.615
426
Crystal size (mm)
h (°)
Limiting indices
0.40 ꢂ 0.39 ꢂ 0.32
0.45 ꢂ 0.37 ꢂ 0.22
0.25 ꢂ 0.19 ꢂ 0.12
2.69–25.02
ꢀ10 6 h 6 10, ꢀ17 6 k 6 16,
ꢀ17 6 l 6 13
9311
2.55–25.00
2.34–25.02
ꢀ21 6 h 6 21, ꢀ8 6 k 6 9,
ꢀ14 6 l 6 10
3830
ꢀ10 6 h 6 10, ꢀ12 6 k 6 12,
ꢀ13 6 l 6 9
Reflections collected
4941
Reflections independent (Rint
)
2130 (0.0292)
1.058
3418 (0.0236)
1.070
3253 (0.0661)
0.893
Goodness-of-fit (GOF) on F2
R indices [I > 2
R indices (all data)
r
(I)]
0.0204, 0.0519
0.0205, 0.0519
0.259 and ꢀ0.302
0.0308, 0.0763
0.0327, 0.0786
0.377 and ꢀ0.652
0.0473, 0.0955
0.0898, 0.1106
0.406 and ꢀ0.302
Largest difference in peak and hole
(e Åꢀ3
)
Table 2
Summary of X-ray crystallographic data for complexes 4–7.
4
5
6
7
Formula
Formula weight
T (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
24H22N8O12Zn
C24H24Cl2N4O6Zn
600.74
298(2)
0.71073
triclinic
C17H20CdN4O6S
520.83
298(2)
0.71073
orthorhombic
Cmc2(1)
14.7358(13)
9.3354(11)
14.3430(12)
90
90
90
1973.1(3)
4
1.753
C28H36Cd2N8O8
837.45
298(2)
0.71073
triclinic
679.87
298(2)
0.71073
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
11.4450(10)
11.6569(11)
12.4901(13)
77.755(2)
78.377(2)
61.9900(10)
1427.6(2)
10.236(3)
11.906(3)
12.380(3)
115.277(3)
98.918(3)
92.119(3)
1338.8(6)
2
8.2815(7)
13.8825(14)
15.7906(16)
90.8640(10)
92.9230(10)
94.187(2)
1807.9(3)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
2
Dcalc. (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
1.582
0.938
696
1.490
1.162
616
1.538
1.230
840
)
1.256
1048
Crystal size (mm)
h (°)
Limiting indices
0.45 ꢂ 0.41 ꢂ 0.32
2.37–25.02
ꢀ11 6 h 6 13, ꢀ13 6 k 6 13,
ꢀ10 6 l 6 14
7173
0.49 ꢂ 0.41 ꢂ 0.39
2.62–25.02
ꢀ12 6 h 6 12, ꢀ14 6 k 6 11,
ꢀ10 6 l 6 14
6680
0.41 ꢂ 0.40 ꢂ 0.40
0.34 ꢂ 0.12 ꢂ 0.10
2.58–24.99
2.47–25.02
ꢀ17 6 h 6 17, ꢀ8 6 k 6 11,
ꢀ14 6 l 6 17
4745
ꢀ9 6 h 6 9, ꢀ16 6 k 6 11,
ꢀ18 6 l 6 18
8521
Reflections collected
Reflections independent (Rint
)
4942 (0.0237)
1.054
4627 (0.0246)
1.023
1728 (0.0354)
1.076
6150 (0.0540)
1.050
Goodness-of-fit (GOF) on F2
R indices [I > 2
R indices (all data)
Largest difference in peak and
hole (e Åꢀ3
r
(I)]
0.0378, 0.0874
0.0547, 0.0968
0.243 and ꢀ0.461
0.0389, 0.0964
0.0597, 0.1118
0.413 and ꢀ0.419
0.0198, 0.0486
0.0204, 0.0490
0.412 and ꢀ0.352
0.0817, 0.1935
0.1573, 0.2495
2.647 and ꢀ1.859
)
confirmed by the presence of characteristic NH bands in the region
3500–3200 cmꢀ1 [25]. Weak absorptions observed in the range
3000–2800 cmꢀ1 can be attributed to aromatic C–H and the ole-
finic CH group of the anions in 1 and 7.
ratio of 1:2:4, yielding pure Cd(Hdmpz)2(L1)2 upon addition of a
few drops of conc. ammonia solution. The structural determination
revealed that Cd, L1 and Hdmpz are present in a 1:2:2 ratio in the
molecular complex 1, and the asymmetric unit is shown in Fig. 1.
Complex 1 crystallizes as monoclinic colorless crystals in the space
group C2 with two formula units in the unit cell. Each Cd ion is
octahedrally coordinated by four oxygen atoms of two L1 ligands
and by two nitrogen atoms of two different monodentate pyrazole
ligands, generating a distorted trigonal prismatic geometry (Fig. 1).
Herein the L1 ligand is coordinated to the Cd ion in a chelating
3.2. Crystal structure description
3.2.1. Crystal and molecular structure of Cd(Hdmpz)2(L1)2 (1)
Compound 1 was prepared by the reaction of Cd(CH3COO)2ꢁ2H2-
O, N-phenylmaleamic acid (HL1) and Hdmpz in MeOH solvent in a

14
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
Table 3
O(7)–Cd(2)–O(6)
O(2)–Cd(2)–O(6)
82.0(3)
93.3(3)
N(5)–Cd(2)–O(6)
N(7)–Cd(2)–O(6)
92.3(4)
86.7(4)
Selected bond lengths [Å] and angles [°] for 1–7.
1
Symmetry transformations used to generate equivalent atoms for 1: #1 ꢀx + 1, y,
ꢀz.
Cd(1)–N(1)
Cd(1)–O(2)
O(2)–C(6)
N(1)–Cd(1)–N(1)#1
N(1)#1–Cd(1)–O(1)
O(1)#1–Cd(1)–O(2)
2.258(2) Cd(1)–O(1)
2.379(2) O(1)–C(6)
1.243(4) O(3)–C(9)
2.379(2)
1.267(3)
1.231(4)
96.86(8)
89.30(8)
81.8(1)
Symmetry transformations used to generate equivalent atoms for 2: #1 ꢀx, ꢀy + 2,
ꢀz + 1.
108.4(1)
102.31(8)
98.17 (8)
N(1)–Cd(1)–O(1)
N(1)–Cd(1)–O(2)
O(2)–Cd(1)–O(2)#1
Symmetry transformations used to generate equivalent atoms for 6: #1 ꢀx + 1, y, z;
#2 ꢀx + 1, ꢀy + 1, z + 1/2; #3 x, y ꢀ 1, z.
Symmetry transformations used to generate equivalent atoms for 7: #1 ꢀx + 1,
ꢀy + 2, ꢀz; #2 ꢀx + 1, ꢀy + 2, ꢀz + 1.
2
Cd(1)–O(1)
Cd(1)–N(3)
O(2)–C(11)
O(3)–C(18)
O(4)–C(18)
O(1)–Cd(1)–N(1)
O(1)–Cd(1)–N(3)
N(1)#1–Cd(1)–N(3)
2.348(2) Cd(1)–N(1)
2.373(2) O(1)–C(11)
1.269(3) O(3)–C(14)
1.421(4) O(4)–C(15)
1.412(4) O(1)#1–Cd(1)–N(1)
2.364(2)
1.247(3)
1.382(3)
1.378(3)
90.05(7)
90.89(7)
87.44(7)
Table 4
Hydrogen bond distances and angles in the studied structures of 1–7.
D–Hꢁ ꢁ ꢁA
d(D–H) [Å] d(Hꢁ ꢁ ꢁA) [Å] d(Dꢁ ꢁ ꢁA) [Å] <(DHA) [°]
89.95(7)
89.11(7)
92.56(7)
O(1)#1–Cd(1)–N(3)
N(1)–Cd(1)–N(3)
1
N(3)–H(3)ꢁ ꢁ ꢁO(1)#2 0.86
2.12
1.99
2.942(3)
2.815(3)
161.1
161.2
N(2)–H(2)ꢁ ꢁ ꢁO(3)
0.86
3
Zn(1)–O(1)
Zn(1)–N(2)
O(1)–C(1)
O(1)–Zn(1)–N(3)
N(3)–Zn(1)–N(2)
N(3)–Zn(1)–N(4)
1.947(3) Zn(1)–N(3)
1.964(4) Zn(1)–N(4)
1.242(5) O(2)–C(1)
1.956(3)
2.010(4)
1.221(5)
109.6(1)
109.6(1)
110.5(1)
2
N(2)–H(2)ꢁ ꢁ ꢁO(2)#1 0.86
1.95
1.93
2.751(3)
2.749(3)
154.9
159.1
N(4)–H(4)ꢁ ꢁ ꢁO(2)
0.86
106.7(1)
O(1)–Zn(1)–N(2)
O(1)–Zn(1)–N(4)
N(2)–Zn(1)–N(4)
3
112.9(1)
107.5(1)
N(5)–H(5)ꢁ ꢁ ꢁO(2)
0.86
1.88
2.693(5)
156.5
4
4
N(4)–H(4)ꢁ ꢁ ꢁO(2)
0.86
0.86
2.09
1.97
2.838(3)
2.756(3)
145.6
150.9
Zn(1)–O(7)
Zn(1)–N(1)
O(1)–C(11)
O(7)–C(18)
O(7)–Zn(1)–O(1)
O(1)–Zn(1)–N(1)
O(1)–Zn(1)–N(3)
1.951(2) Zn(1)–O(1)
1.951(2)
1.989(2)
1.232(3)
N(2)–H(2)ꢁ ꢁ ꢁO(8)
1.983(2) Zn(1)–N(3)
1.278(3) O(2)–C(11)
1.275(3) O(8)–C(18)
5
O(6)–H(6)ꢁ ꢁ ꢁO(5)
O(3)–H(3)ꢁ ꢁ ꢁO(2)
N(4)–H(4)ꢁ ꢁ ꢁO(5)
N(2)–H(2)ꢁ ꢁ ꢁO(2)
0.82
0.82
0.86
0.86
1.83
1.88
2.07
1.96
2.555(3)
2.603(3)
2.821(4)
2.767(4)
147.1
145.7
145.3
154.9
1.230(3)
95.81(9)
110.24(9)
117.00(9)
O(7)vZn(1)–N(1)
O(7)–Zn(1)–N(3)
N(1)–Zn(1)–N(3)
112.48(9)
112.21(9)
108.71(9)
6
5
O(2)–H(2A)ꢁ ꢁ ꢁO(3)
0.82
1.71
2.40
2.15
2.485(5)
2.929(3)
2.956(4)
156.1
120.2
155.0
Zn(1)–O(1)
Zn(1)–N(1)
O(1)–C(11)
O(3)–C(13)
O(5)–C(18)
O(1)–Zn(1)–O(4)
O(4)–Zn(1)–N(1)
O(4)–Zn(1)–N(3)
1.925(2) Zn(1)–O(4)
1.933(2)
2.004(3)
1.247(4)
1.268(3)
1.337(4)
113.6(1)
105.4(1)
104.8(1)
N(2)–H(2)ꢁ ꢁ ꢁO(2)#2 0.86
1.977(3) Zn(1)–N(3)
1.275(4) O(2)–C(11)
1.357(4) O(4)–C(18)
1.250(4) O(6)–C(20)
N(2)–H(2)ꢁ ꢁ ꢁO(5)#6 0.86
7
N(8)–H(8)ꢁ ꢁ ꢁO(7)#2 0.86
1.99
2.16
2.12
1.97
2.809(15)
2.882(16)
2.870(15)
2.797(16)
159.4
141.6
146.1
161.8
102.0(1)
113.5(1)
117.6(1)
O(1)–Zn(1)–N(1)
O(1)–Zn(1)–N(3)
N(1)–Zn(1)–N(3)
N(6)–H(6)ꢁ ꢁ ꢁO(1)
N(4)–H(4)ꢁ ꢁ ꢁO(6)
0.86
0.86
N(2)–H(2)ꢁ ꢁ ꢁO(3)#1 0.86
6
Symmetry transformations used to generate equivalent atoms for 1: #2 ꢀx + 1/2,
y ꢀ 1/2, ꢀz.
Cd(1)–N(1)
Cd(1)–O(3)#3
O(1)–C(6)
O(3)–C(8)
O(5)–S(1)
N(1)#1–Cd(1)–O(1)#2 102.56(8)
N(1)#1–Cd(1)–O(4)#1
O(3)#3–Cd(1)–O(4)#1
2.278(3) Cd(1)–O(1)#2
2.495(3) Cd(1)–O(4)
1.245(5) O(2)–C(6)
1.349(5) O(4)–S(1)
1.446(4) N(1)#1–Cd(1)–N(1)
2.293(3)
2.500(3)
1.269(5)
1.453(2)
118.2(1)
84.09(8)
87.02(9)
Symmetry transformations used to generate equivalent atoms for 2: #1 ꢀx, ꢀy + 2,
ꢀz + 1.
Symmetry transformations used to generate equivalent atoms for 6: #1 ꢀx + 1, y, z;
#2 ꢀx + 1, ꢀy + 1, z + 1/2; #3 x, y ꢀ 1, z; #4 ꢀx + 1, ꢀy + 1, z ꢀ 1/2; #5 x, y + 1, z; #6
ꢀx + 1, ꢀy, z + 1/2.
N(1)#1–Cd(1)–O(3)#3
O(1)#2–Cd(1)–O(4)#1
90.99(9)
81.07(8)
Symmetry transformations used to generate equivalent atoms for 7: #1 ꢀx + 1,
ꢀy + 2, ꢀz; #2 ꢀx + 1, ꢀy + 2, ꢀz + 1.
7
Cd(1)–O(4)#1
Cd(1)–O(5)
Cd(1)–N(1)
Cd(2)–O(7)
Cd(2)–O(8)#2
Cd(2)–N(7)
O(1)–C(1)
O(3)–C(4)
O(5)–C(5)
O(7)–C(8)
O(4)#1–Cd(1)–O(3)
O(3)–Cd(1)–O(5)
O(4)#1–Cd(1)–N(1)
O(3)–Cd(1)–N(1)
O(3)–Cd(1)–O(1)
N(3)–Cd(1)–O(1)
O(7)–Cd(2)–O(8)#2
O(7)–Cd(2)–O(2)
O(8)#2–Cd(2)–O(2)
N(5)–Cd(2)–N(7)
2.363(9) Cd(1)–O(3)
2.371(9) Cd(1)–N(3)
2.365(8)
2.407(12)
2.437(9)
2.36(1)
2.383(9)
2.44(1)
1.28(2)
1.28(1)
1.30(2)
1.29(2)
89.4(3)
95.6(4)
88.6(4)
91.8(4)
93.3(3)
87.0(4)
92.4(4)
88.3(4)
94.3(4)
93.8(4)
bidentate fashion, whilst the pyrazole ligand is coordinated only in
the monodentate terminal fashion with its neutral nitrogen group
bonding to the Cd ion. The coordination mode of Cd is similar to
the reported compounds [Cd(La)2(Hdmpz)2] where La = R–C6H4-
COO– [R = H, 2-Cl, 4-OH, 2-OH] [26].
The location of H2 in 1, bound to nitrogen and not to oxygen
atoms, is consistent with the different acidic characters of pyrazole
and N-phenylmaleamic acid [27], and is also confirmed by the dif-
ference electron density map with which to find the H atoms. The
Cd–N and Cd–O distances are 2.258(2) and 2.379(2) Å, respectively,
indicating that the cadmium atom belongs to the inner coordina-
tion sphere [28]. The angles around the Cd atom range from
55.13(7)° to 153.71(8)°.
2.41(1)
2.33(1)
2.36(1)
2.44(1)
1.31(2)
1.31(1)
1.29(2)
1.32(2)
88.7(3)
86.5(3)
90.1(4)
93.1(4)
83.5(3)
92.4(4)
93.3(4)
85.4(4)
86.2(3)
92.0(4)
Cd(1)–O(1)
Cd(2)–N(5)
Cd(2)–O(2)
Cd(2)–O(6)
O(2)–C(1)
O(4)–C(4)
O(6)–C(5)
O(8)–C(8)
O(4)#1–Cd(1)–O(5)
O(4)#1–Cd(1)–N(3)
O(5)–Cd(1)–N(3)
N(3)–Cd(1)–N(1)
O(5)–Cd(1)–O(1)
N(1)–Cd(1)–O(1)
N(5)–Cd(2)–O(8)#2
N(5)–Cd(2)–O(2)
O(7)–Cd(2)–N(7)
O(8)#2–Cd(2)–N(7)
Moreover 1 is not an ionic species consisting of a monocationic
Cd(II) complex and carboxylate counterions. In 1, the oxygen atom

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
15
Fig. 1. Molecular structure of complex 1 showing the atomic numbering scheme at the 30% ellipsoid probability level.
of the CONH moiety of L1, far from the Cd ion at a distance of
3.2.2. Crystal and molecular structure of Cd(Hdmpz)4(L2)2 (2)
4.585 Å, is involved in intramolecular hydrogen bonding (N(2)–
H(2)ꢁ ꢁ ꢁO(3)) with an N–O distance of 2.815(3) Å and H–O distance
of 1.99 Å.
Crystals of 2 contain a mononuclear complex of the formulae
Cd(Hdmpz)4(L2)2 (Fig. 3). Compound 2 crystallizes as triclinic col-
orless block crystals in the space group P1, and there is one asym-
ꢀ
The root mean square (rms) deviations of the phenyl ring in the
anion with the C10–C15 atoms and the pyrazole ring with N1, and
N2 atoms are 0.0036 and 0.0059 Å, respectively, and the above two
rings intersected at an angle of 138.3°. The dihedral angle between
the phenyl ring and the plane defined by the amide group (–
NHCO–) in the same anion is 149.6° (for the amide group H1–
N1–C4@O3). The conformations of the N–H and C@O bonds in
the amide segment of the structure are anti to each other. Further,
the conformation of the amide O atom is anti to the H atom at-
tached to the adjacent C atom (Fig. 1).
The C(7)@C(8) bond distance (1.325(4) Å) is appropriate for a
simple C@C double bond, due to the significant non-coplanarity
of the carboxyl group and the olefinic group (the plane defined
by the carboxylate group is almost perpendicular to the plane de-
fined by the amide and the olefinic groups, which is different from
the crystal structure of N-phenylmaleamic acid [29]), but the
C(7)@C(8) bond distance is somewhat shortened compared with
the corresponding values (1.335 and 1.344 Å) in the neutral mole-
cule [29]. The C–O bond distance for O(1)–C(6) (1.267(3) Å) is
somewhat longer than the O(2)–C(6) (1.243(4) Å) bond, and the
reason for this may be that O(1) is involved in a stronger H-bond
than O(2) (Table 4).
The mononuclear units are linked together in a head to tail fash-
ion via the N–Hꢁ ꢁ ꢁO (N(3)–H(3)ꢁꢁꢁO(1)#2, 2.942(3) Å, 161.1°, #2
ꢀx + 1/2, y ꢀ 1/2, ꢀz) hydrogen bond and C–Hꢁ ꢁ ꢁO associations be-
tween the same olefinic CH group of the anion and one coordinated
O atom of the carboxylate group and the O atom of the CONH
group, with C–O distances of 3.424–3.461 Å, forming a 1D chain
running along the diagonal direction of the ab plane. In this regard,
the olefinic CH (C(8)H(8)) functions as a bifurcate donor in gener-
ating the C–Hꢁ ꢁ ꢁO associations. In the chain, the Cd cations are lin-
early arranged, with a distance of 10.051 Å between two adjacent
Cd cations. The 1D chains are further held together by an inter-
chain N–Hꢁ ꢁ ꢁO (N(3)–H(3)ꢁ ꢁ ꢁO(1)#2, 2.942(3) Å, 161.1°, #2
ꢀx + 1/2, y ꢀ 1/2, ꢀz) hydrogen bond and C–Hꢁ ꢁ ꢁO associations be-
tween the olefinic CH group of the anion and one coordinated O
atom of the carboxylate group and the O atom of the CONH group,
with C–O distances of 3.424–3.461 Å, forming a 2D square grid
sheet extending along the ab plane (Fig. 2). The 2D square grid
metric structural unit in its cell content. Each Cd ion is octahedrally
coordinated by two oxygen atoms of two monodentate L2 ligands
and by four nitrogen atoms belonging to four monodentate pyra-
zole ligands, with a CdN4O2 binding set. The Cd ion is located at
the inversion center (0, 1, 0.5). The CdN4O2 unit possesses coordi-
nation distances and angles in the ranges 2.3478(17)–2.3726(19) Å
and 87.44(7)–180.0°, respectively. The Cd–N and Cd–O bond
lengths are of comparable values.
In 2, the non-bonded oxygen atoms, far enough from the Cd
ions at a distance of 3.709 Å, are involved in two intramolecular
hydrogen bonds (N(4)–H(4)ꢁ ꢁ ꢁO(2) and N(2)–H(2)ꢁ ꢁ ꢁO(2)#1, #1
ꢀx, ꢀy + 2, ꢀz + 1) with N–O distances ranging from 2.749(3) to
2.751(3) Å, and H–O distances of 1.93–1.95 Å. Herein every non-
bonded oxygen atom forms two hydrogen bonds in a bifurcated
mode.
The mononuclear units are connected together via CH2–p asso-
ciations between the CH2 group from the 1,3-benzodioxole unit of
the anion and the aromatic ring of the pyrazole, with a C–Cg dis-
tance of 3.672 Å, and CH–O interactions between the phenyl CH
of L2 and the O atom of the 1,3-benzodioxole group, with a C–O
distance of 3.558 Å, to form a 1D chain. In the chain, the Cd–Cd dis-
tance is 12.022 Å. The 1D chains are extended in parallel in the
same plane, which has a dihedral angle of ca 60° with the bc plane,
to form a 2D sheet (Fig. 4), yet there are no connections between
these chains in the same plane. The sheets further stacked along
the direction that is perpendicular to its extending direction to
form a 3D network structure. There are also no interactions be-
tween these sheets.
3.2.3. Crystal and molecular structure of Zn2(l-dmpz)2(Hdmpz)2(L3)2
(3)
The structural determination revealed that compound 3, of the
formula Zn2( -dmpz)2(Hdmpz)2(L3)2, crystallizes as monoclinic
l
colorless crystals in the centrosymmetric space group P2(1)/n with
two formula units in the unit cell. As illustrated in Fig. 5, the asym-
metric unit consists of one ZnII cation, one pyrazole molecule, one
pyrazolate unit and one carboxylate ligand. The pyrazolate unit
acts as an N,N0-exobidentate ligand, keeping the two zinc ions at
a non-bonding distance of ca. 3.534 Å. The complex molecule is
dinuclear and consists of a ZnII atom positioned at the center of a
sheets are further combined together by CH–p interactions be-
tween the phenyl CH of the anion and the aromatic ring of the an-
ion, with a C–Cg distance of 3.515 Å, to form a 3D square grid layer
structure. Herein the chains from adjacent sheet layers are inter-
sected at an angle of ca. 30° with each other, while the chains in
the third sheet layer are parallel to the chains in the first sheet
layer, as are the chains in the second sheet layer and the fourth
sheet layer.
planar six-membered [Zn(l-dmpz)2Zn] unit; each single unit has
a four-coordinate zinc ion with three Zn–N bonds (one Zn–Npyrazole
and two Zn–Npyrazolato) and one Zn–Ocarboxylate bond. The bridging
Zn–N distance of 1.96 Å (average) is shorter than the terminal
Zn–N distance of 2.010(4) Å, which is similar to the reported values
[30]. The carboxylate groups coordinate in a monodentate manner
with a Zn(1)–O(1) distance of 1.947(3) Å. The distance (3.364 Å)

16
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
Fig. 2. Packing diagram of compound 1 showing the square grid sheet structure extending along the ab plane.
Fig. 3. Molecular structure of complex 2 showing the atomic numbering scheme at the 30% thermal ellipsoid probability level.
Fig. 4. The sheet structure of compound 2 extended in the direction that has a dihedral angle of ca 60° with the bc plane.
between the non-bonded oxygen atom and the zinc ion is too large
for the oxygen to coordinate with the metal ion. The coordination
arrangement around zinc in complex 3 is a distorted tetrahedron
with coordination angles in the range 106.68(13)–112.92(13)°.
The geometrical parameters of this species closely match those re-
cently reported for the analogous [{Zn(
Hpz⁄)}2] [31] (Hpz⁄ = 4-acetyl-3-amino-5-methylpyrazole) and
[{Zn( -C2H5COO)( -pz)(Hpz)}2] [30] complexes.
In complex 3, the non-bonded oxygen atom of the carboxylate
group forms an intramolecular hydrogen bond, N(5)–H(5)ꢁ ꢁ ꢁO(2),
l-C2H5COO)(l
-pz⁄)(-
l
l

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
17
Fig. 5. Molecular structure of complex 3 showing the atomic numbering scheme at the 30% ellipsoid probability level.
with N(5)–O(2) and H(5)ꢁ ꢁ ꢁO(2) distances of 2.693(5) and 1.88 Å,
3.2.4. Crystal and molecular structure of Zn(Hdmpz)2(L4)2 (4)
respectively. There also exists an intramolecular Cl–O contact be-
tween the Cl atom of the anion and the coordinated O atom of
the carboxylate group, with a Cl–O distance of 2.905 Å; in this case
the Cl–O contact is somewhat stronger than the reported example
[32].
Compound 4 crystallizes in the triclinic system with the space
ꢀ
group P1. An asymmetric unit of Zn(Hdmpz)2(L4)2 contains one
tetrahedrally coordinated Zn(II) ion, two monodentate L4 anions
and two Hdmpz groups, which is shown in Fig. 7. The molecular
structure of 4 resembles the related [Zn(CH3COO)2(ML)2] monomer
(ML = a monodentate nitrogen ligand), like the bisimidazole [33]
and bis-pyridine [34] complexes.
The ZnN2O2 moiety has coordination distances and angles in the
ranges 1.951(2)–1.989(2) Å and 95.81(9)–117.00(9)°, respectively;
thus the overall coordination arrangement resembles that found in
the compounds [Zn(Hpz)2(Me3NCH2CO2)](ClO4)2 [30] and
{[Zn(CH3COO)2(Hpz)2]ꢁCH3COOH} (Hpz = pyrazole) [19]. Although
the distortion in the ZnN2O2 moiety is somewhat differently ori-
ented in the latter two compounds, the angles around the zinc
atoms are in the range 98.94(19)–117.30(18)° and 95.73(7)–
118.34(8)°, respectively.
In 4, the non-bonded oxygen atoms, far enough from the Zn ions
with distances of 3.084 and 3.364 Å, are involved in two intramo-
lecular hydrogen bonds (N(2)–H(2)ꢁ ꢁ ꢁO(8) and N(4)–H(4)ꢁ ꢁ ꢁO(2)
with the N–O distances ranging from 2.756(3) to 2.838(3) Å and
H–O distances of 1.97–2.09 Å).
The mononuclear units are linked together via CH3–O interac-
tions between the 3-CH3 and 5-CH3 groups of the pyrazole and
the nitro groups, with C–O distances of 3.546 and 3.378 Å respec-
tively to form a 1D chain running along the c axis direction. Such
The adjacent dinuclear moieties are connected through a C–
Hꢁ ꢁ ꢁO interaction between the 4-CH group on the pyrazolato ring
and the non-bonded O atom (with a C–O distance of 3.516 Å)
and a CH3–Cl association between the 5-CH3 group of the pyrazole
and Cl of the anion, with a C–Cl distance of 3.654 Å, to a form 1D
chain. The 1D chains are further joined together by an interchain
C–Hꢁ ꢁ ꢁ
p interaction, existing between 4-CH on the pyrazole ring
and the pyrazolato ring in parallel neighboring chains (with a dis-
tance of 4-C on the pyrazole ring to the pyrazolato ring of 3.741 Å),
and a CH3ꢁ ꢁ ꢁ
p interaction between 5-CH3 on the pyrazole ring and
the aromatic ring of the anion, with a C–Cg distance of 3.601 Å, to
form a 2D sheet extending in the direction that is inclined at an an-
gle of ca. 60° with the ac plane (Fig. 6). The sheets are further
stacked along the direction that is perpendicular to its extending
direction by intersheet CH–O (between the 4-CH group of the
pyrazolato ring and the non-bonded O atom of the carboxylate
group of L3, with a C–O distance of 3.516 Å) and CH3–Cl (between
the 5-CH3 group of the pyrazole ring and the Cl atom of the anion,
with a C–Cl distance of 3.654 Å) associations to form a 3D network
structure.
Fig. 6. The sheet structure of 3 extending in the direction that is inclined at an angle of ca. 60° with the ac plane.

18
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
Fig. 7. Molecular structure of complex 4 showing the atomic numbering scheme at the 30% ellipsoid probability level.
chains are joined together by CH3–
p
interactions between the 5-
sponding anions and cations in the first sheet layer, as are the
corresponding anions and cations in the second sheet layer and
the fourth sheet layer.
CH3 group of the pyrazole ring and the aromatic ring of the anion,
with a C–Cg distance of 3.484 Å, to form a 2D grid sheet extending
parallel to the ac plane (Fig. 8). In the sheet the neighboring Zn–Zn
separation along the c axis direction is 12.490 Å and the neighbor-
ing Zn–Zn separation along the a axis direction is 11.445 Å. The
grid sheets are further stacked along the b axis direction via an
intersheet CH3–O association between the 3-CH3 group of the pyr-
azole ring and the non-bonded O atom of the anion, with a C–O dis-
3.2.5. Crystal and molecular structure of Zn(Hdmpz)2(HL5)2 (5)
Compound 5 crystallizes in the triclinic system with the space
group Pbar1. The asymmetric unit of Zn(Hdmpz)2(HL5)2 contains
one four-coordinated Zn(II) ion, two HL5 anions and two Hdmpz
groups, which is shown in Fig. 9. The Zn–O distances are
1.925(2)–1.933(2) Å and the Zn–N distances are 1.977(3) and
2.004(3) Å, which are similar to the corresponding bond distances
in 4.
In 5, the non-bonded oxygen atoms, far enough from the Zn ions
with distances of 3.145 and 3.371 Å, are involved in two intramo-
lecular hydrogen bonds, N(2)–H(2)ꢁ ꢁ ꢁO(2) and N(4)–H(4)ꢁ ꢁ ꢁO(5),
with N–O distances ranging from 2.767(4) to 2.821(4) Å and H–O
distances of 1.96–2.07 Å. Because of the presence of an intramolec-
tance of 3.494 Å, and an O–p association between the non-bonded
O atom of the carboxylate group of the 3,5-dinitrobenzoate and the
phenyl ring of the anion, with an O–Cg distance of 3.112 Å, to form
a 3D layer structure. In this regard, adjacent sheets are slipped
some distance from each other along the a and c axis directions,
respectively. The corresponding anions and cations in neighboring
sheet layers are arranged antiparallel, while the corresponding an-
ions and cations in the third sheet layer are parallel to the corre-
Fig. 8. The grid sheet structure of compound 4 extended parallel to the ac plane.

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
19
The mononuclear units are linked together via CH3–O interac-
tions between the 5-CH3 group of the pyrazole ring and the phenol
group, with a C–O distance of 3.108 Å, to form a 1D chain. Two
such chains are joined together by a
p–p association between
the aromatic ring of the pyrazole and the phenyl ring of the anion,
with a Cg–Cg distance of 3.333 Å, to form a double chain structure.
The double chains are connected together by a CH–O association
between the 4-CH group of the pyrazole ring and the phenol group,
with a C–O separation of 3.458 Å, and a CH–Cl association between
the 5-CH3 group of the pyrazole ring and the Cl atom of HL5, with
C–Cl a distance of 3.543 Å, to form a 2D sheet extending parallel to
the bc plane (Fig. 10). The sheets are further stacked along the a
axis direction by a Cl–Cl bond, with a Cl–Cl separation of 3.448 Å,
to form a 3D network structure. Here the Cl–Cl bond distance is
somewhat shorter than our previously reported data [37].
3.2.6. Crystal and molecular structure of Cd(Hdmpz)2(HL6) (6)
Compound 6, of the formula Cd(Hdmpz)2(HL6), crystallizes as
orthorhombic crystals in the centrosymmetric space group
Cmc2(1), and there are four formula units in its cell content. The
asymmetric unit contains one Cd, one HL6 and one pyrazole Li-
gand. The SO3H and OH groups are both deprotonated, while the
ꢀ
COOH group remains protonated. The SO3 group is coordinated
Fig. 9. Molecular structure of complex 5 showing the atomic numbering scheme at
to Cd in a chelating bidentate fashion, whilst all the other groups,
namely the COOH, phenolate and pyrazole, coordinated to Cd in
monodentate fashion (Fig. 11). The COOH group is coordinated to
Cd by its carbonyl unit and the pyrazole by its neutral N moiety.
The Cd–N distance is 2.278(3) Å and the Cd–O distances are
2.495(3)–2.500(3) Å. The angles around the Cd atom range from
56.09(11)° to 166.50(10)°.
the 30% ellipsoid probability level.
ular hydrogen bond between the carboxylate groups and the phe-
nol groups (O(6)–H(6)ꢁ ꢁ ꢁO(5), 2.555(3) Å; O(3)–H(3)ꢁ ꢁ ꢁO(2),
2.603(3) Å) in the anion, it is generally expected and found that
the carboxylate groups are essentially coplanar with the benzene
rings [torsion angles C13–C12–C11–O2, 6.09°, C22–C19–C18–O5,
2.46°]. For the presence of this O–Hꢁ ꢁ ꢁO hydrogen bond (Table 4)
between the phenol OH groups and the uncoordinated oxygen
atoms of the carboxylate group of HL5, there exists a S11(6) loop
motif in the anion. This feature is similar to that found in salicylic
acid [33] and in the previously reported structure of a deproto-
nated compound based on o-hydroxy benzoic acid derivatives
[35]. As expected, the O–O separations 2.555(3)–2.603(3) Å (mean:
2.579 Å) are essentially at the upper limit of the documented data
[2.531(4)–2.570(4) Å] [36] because of the planarity of the hydro-
gen bonded carboxylate unit, but they are slightly contracted com-
pared with the non-deprotonated examples (2.547–2.604 Å, mean:
2.588 Å), as a result of the deprotonation.
The Cd atom and the anions are linked together to form a hon-
eycomb structure extending parallel to the bc plane (Fig. 12). The
pyrazoles coordinate to the Cd atoms from both faces of the honey-
comb, i.e. both pyrazoles are protruded from the honeycomb plane
in opposite directions. In the honeycomb intermolecular and intra-
molecular N–Hꢁ ꢁ ꢁO hydrogen bonds exist between the neutral NH
unit of the pyrazole ring and the OH of the carboxyl group and the
ꢀ
O atom of the SO3 group, an intramolecular O–Hꢁ ꢁ ꢁO hydrogen
bond also exists between the COOH group and the phenolate
group, with an O–O separation of 2.485(5) Å. The honeycombs
are further stacked along the a axis direction by an intersheet
CH–O association between 4-CH of the pyrazole group and the
Fig. 10. Packing diagram of compound 5 with the sheet structure extended parallel to the bc plane.

20
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
ions with the remaining two oxygen atoms. This coordinating
mode is different from the corresponding compound Zn2(-
Hdmpz)4(L2)2 (H2L2 = maleic acid) [20a].
The CdN2O4 unit possesses coordination distances and angles in
the ranges 2.326(10)–2.437(10) Å and 82.0(3)–179.7(4)°, respec-
tively. The C(2)@C(3) and C(6)@C(7) bond distances (1.354(18)
and 1.347(19) Å), although longer than the corresponding values
of the documented compound [20a], relate to a simple C@C double
bond, due to the significant non-coplanarity of the carboxyl and
olefinic groups.
The rms deviations of the two pyrazole rings coordinated to Cd1
are 0.0167 (for the ring with N1 and N2) and 0.0188 Å (for the ring
bearing N3 and N4). The pair of pyrazoles coordinated to the same
Cd centre have dihedral angles of 61° for Cd1 and 54.1° for Cd2. The
rms deviations of the two pyrazole rings coordinated to Cd2 are
0.0227 Å for the ring with N5 and N6, and 0.0158 Å for the ring
with N7 and N8. The dihedral angles between the pyrazole rings
coordinated to different Cd cations are 35.7°, 40.6°, 61.7° and 19.9°.
The carboxylates and the Cd anions form a 1D chain running
along the c axis direction. In the chain, adjacent Cd–Cd separations
are 5.009 and 5.025 Å. The interchain Cd–Cd distance is 8.281 Å. In
the chain, the chelated carboxylates and Cd generate a seven-
membered ring, whilst two carboxylates and two Cd centres pro-
duce an eight-membered ring, then the seven-membered and
eight-membered rings repeat along the chain, and these two kinds
of rings are fused together. The pyrazole molecules are attached to
the chain via Cd–N bonds. In the chain an N–Hꢁ ꢁ ꢁO interaction also
exists, arising from the NH moiety of a pyrazole ligand and the O
atom of a carboxylate group that did not bond with the same metal
ion as the pyrazole donor. The 1D chains are joined together via an
interchain CH–O association between the olefinic CH of the anion
and a carboxylate group, with a C–O distance of 3.505 Å, to form
a sheet structure (Fig. 14).
Fig. 11. Molecular structure of complex 6 showing the atomic numbering scheme
at the 30% ellipsoid probability level.
ꢀ
SO3 unit, with a C–O distance of 3.375 Å, to form a 3D network
structure.
3.2.7. Crystal and molecular structure of Cd2(Hdmpz)4(L7)2 (7)
Crystals of 7 contain the dinuclear Cd2(Hdmpz)4(L7)2 (Fig. 13).
Compound 7 crystallizes as triclinic colorless blocks in the space
ꢀ
group P1, and there are two formula units in its cell. Each Cd is
octahedrally coordinated by four oxygens of three different L7 an-
ions and by two nitrogens, belonging to two monodentate pyra-
zoles ligands, with a CdN2O4 bonding set. The malonate anion
coordinates to one metal ion in a chelating form with two of the
four oxygen atoms, and further bridges the neighboring two metal
3.3. Thermogravimetry (TG)
The TGA studies showed that 1 is stable below 160 °C. Its
decomposition begins at 165.2 °C. The weight loss of 27.91% in
Fig. 12. The honeycomb structure of compound 6 extending parallel to the bc plane.

S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
21
Fig. 13. Molecular structure of complex 7 showing the atomic numbering scheme. To prevent crowding, the atomic numbering scheme is not shown.
Fig. 14. The grid sheet structure of compound 7 produced via CH–O associations.
the temperature range 165.2–259.5 °C is caused by the loss of the
two pyrazole molecules (Calc. 28.03%). The weight loss of 55.31%
from 269.2 to 426.7 °C arises from the loss of two L1 ligands (Calc.
55.47%). Compound 2 is stable below 150 °C. The weight loss of
46.29% in the temperature range 157.7–245.1 °C is caused by the
loss of the four pyrazole molecules (Calc. 46.42%). The weight loss
of 39.69% from 286.7 to 421.8 °C is due to the loss of the two L2 li-
gands (Calc. 39.89%). For 3 the first weight loss of 23.03% in the
temperature range 152.9–251.4 °C is attributed to the loss of the
terminal pyrazole molecules (Calc. 23.23%). The second weight loss
of 37.43% from 289.6 to 421.8 °C is due to the loss of the two L3 li-
gands (Calc. 37.75%) and the third weight loss of 22.64% in the tem-
perature range 443.7–617.9 °C corresponds approximately to the
release of the bridging pyrazoles (Calc. 22.99%). For 4, the weight
loss of 28.16% (Calc. 28.24%), corresponding to the loss of two
Hdmpz molecules, was observed in the temperature range
169.3–282.9 °C, and there is a weight loss of 61.90% between
302.6 and 487.8 °C, which is due to the loss of the two carboxylate
ligands (Calc. 62.07%). For 5, the first weight loss stage occurs be-
tween 163.1 and 256.0 °C, and corresponds to the removal of
2 mol of Hdmpz ligands (Calc.: 31.96%, Found: 31.87%). The second
stage between 268.9 and 434.2 °C is accompanied by a mass loss of
56.71% for two 5-chlorosalicylates (Calc.: 57.09%). Complex 6 expe-
riences a first weight loss of 36.71% in the temperature range
166.2–259.7 °C, which is due to the loss of the pyrazole molecules
(Calc. 36.86%). The second weight loss of 41.34% was observed be-
tween 297.4 and 439.1 °C, and is attributed to the loss of the
bonded carboxylate ligands (Calc. 41.47%). For 7, the first weight
loss of 45.67% (Calc. 45.85%) corresponds to the loss of four Hdmpz
molecules in the temperature range 159.7–254.6 °C, and the sec-
ond weight loss of 27.14% between 283.2 and 421.3 °C arises from
the loss of the two L7 ligands (Calc. 27.22%).
4. Summary
In summary, a series of mononuclear to dinuclear divalent Zn/
Cd complexes with 3,5-dimethylpyrazole and different carboxylate

22
S.-w. Jin et al. / Polyhedron 60 (2013) 10–22
[10] (a) C. Policar, F. Lambert, M. Cesario, I. Morgenstern-Badarau, Eur. J. Inorg.
Chem. (1999) 2201;
ligands were synthesized and structurally characterized. These
complexes exhibit 2D sheet, 3D network to 3D layer structures.
The central metal ions are coordinated in N2O4, N4O2, N3O and
N2O2 fashions. A distorted octahedral geometry in the case of Cd
and a tetrahedral geometry for Zn were observed in the X-ray
studies.
(b) P.R. Levstein, R. Calvo, Inorg. Chem. 29 (1990) 1581;
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The crystallographic studies demonstrated that in these com-
plexes, the metal centers are coordinated by 3,5-dimethylpyrazole
and there are no deprotonated 3,5-dimethylpyrazole anions except
for compound 3. In addition, the carboxylate groups act as mono-
dentate ligands toward the metal ion in 2, 3, 4, 5 and 6. The COOꢀ
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ꢀ
group in 1 and SO3 in 6 both coordinate to the metals in a chelat-
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radentate bridging ligand. The strong structural propensity toward
tetracoordination in the Zn compounds seems to disfavor the for-
mation of ‘paddlewheel’ dimeric complexes [34,38]. The non-
bonded O atoms of the carboxylate ligands in all the compounds
are involved in the formation of intramolecular hydrogen bonds
with the N–H group of 3,5-dimethylpyrazole. It is worth noting
that the H-bonds in complexes 2–5 are intracomplex and do not
contribute to the formation of an extended architecture, while in
complexes 6 and 7 H-bonds are located in the polymeric groups
and do not extend their dimensionality.
[17] (a) J.E. Cosgriff, G.B. Deacon, Angew. Chem., Int. Ed. Engl. 37 (1998) 286;
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Trans. (2006) 2479;
Complexes 1–7 have abundant intra- and intermolecular weak
interactions (including classical hydrogen bonds, CH–Cl, CH3–Cl,
Clꢁ ꢁ ꢁCl, Clꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁO, CH3ꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁ
p
, CH2ꢁ ꢁ ꢁ
p, CH3–p, O–p
(b) R. Sarma, D. Kalita, J.B. Baruah, Dalton Trans. (2009) 7428;
(c) U.P. Singh, P. Tyagi, S. Pal, Inorg. Chim. Acta 362 (2009) 4403.
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(b) S.W. Jin, D.Q. Wang, J. Coord. Chem. 64 (2011) 1940.
[21] (a) P. Metrangolo, H. Neukirch, T. Pilati, G. Resnati, Acc. Chem. Res. 47 (2005)
386;
and interactions) in their crystals, which lead to the formation
p–p
and stabilization of the final structures.
Acknowledgments
(b) T.R. Shattock, K.K. Arora, P. Vishweshwar, M.J. Zaworotko, Cryst. Growth
Des. 8 (2008) 4533;
(c) K. Biradha, G. Mahata, Cryst. Growth Des. 5 (2005) 61;
(d) B.Q. Ma, P. Coppens, Chem. Commun. (2003) 504;
(e) D.J. Berry, C.C. Seaton, W. Clegg, R.W. Harrington, S.J. Coles, P.N. Horton,
M.B. Hursthouse, R. Storey, W. Jones, Cryst. Growth Des. 8 (2008) 1697;
(f) L. Fa´bia´n, N. Hamill, K.S. Eccles, H.A. Moynihan, A.R. Maguire, L.
McCausland, S.E. Lawrence, Cryst. Growth Des. 11 (2011) 3522.
[22] Bruker, SMART and SAINT, Bruker AXS Inc., Madison, WI, USA, 2004.
[23] SHELXTL-PC, version 5.03, Siemens Analytical Instruments, Madison, WI, 1994.
[24] Y.P. Wu, D.S. Li, F. Fu, W.W. Dong, L. Tang, Y.Y. Wang, Inorg. Chem. Commun.
13 (2010) 1005.
We gratefully acknowledge the financial support of the Educa-
tion Office Foundation of Zhejiang Province (project No.
Y201017321) and the financial support of the Xinmiao project of
(2012R412027) the Education Office Foundation of Zhejiang
Province.
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