Syntheses, crystal structures, properties of metal coordination polymers based on a novel semi-rigid aromatic carboxylate ligand

Article abstract of DOI:10.1016/j.poly.2016.12.008

A set of new metal coordination polymers constructed from a novel semi-rigid aromatic carboxylate ligand, namely, [M(L)(4PBI)(H₂O)]_n(M?=?Ni, Co and Cu for 1, 2 and 3, respectively) and [Cd(L)(4PBI)]_n(4) (H₂L?=?3

Full text of DOI:10.1016/j.poly.2016.12.008

Accepted Manuscript
Syntheses, crystal structures, properties of metal coordination polymers based
on a novel semi-rigid aromatic carboxylate ligand
Cui-Cui Wang, Gui-Mei Tang, Yong-Tao Wang, Jin-Hua Wang, Yue-Zhi Cui,
Seik Weng Ng
PII:
S0277-5387(16)30659-3
DOI:
http://dx.doi.org/10.1016/j.poly.2016.12.008
POLY 12366
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
21 October 2016
6 December 2016
7 December 2016
Please cite this article as: C-C. Wang, G-M. Tang, Y-T. Wang, J-H. Wang, Y-Z. Cui, S. Weng Ng, Syntheses, crystal
structures, properties of metal coordination polymers based on a novel semi-rigid aromatic carboxylate ligand,
Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.12.008
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

-submitted to Polyhedron_revised_1
Syntheses, crystal structures, properties of metal coordination polymers based on a novel semi-
rigid aromatic carboxylate ligand
Cui-Cui Wanga, Gui-Mei Tang*,a, Yong-Tao Wang*,a, Jin-Hua Wanga, Yue-Zhi Cuia and Seik Weng
Ngb
aDepartment of Chemical Engineering, Shandong Provincial Key Laboratory of Fine Chemicals, Qilu
University of Technology, Jinan, 250353, China
bChemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
*Corresponding authors. E-mail: ceswyt@qlu.edu.cn (Y.-T. Wang); meiguit@163.com (G.-M. Tang)
Fax: int code +86 0531 8963 1207. Tel: +86 0531 8963 1207.
ABSTRACT
A set of new metal coordination polymers constructed from a novel semi-rigid aromatic carboxylate
ligand, namely, [M(L)(4PBI)(H2O)]n (M = Ni, Co and Cu for 1, 2 and 3, respectively) and
[Cd(L)(4PBI)]n (4) (H2L = 3-(1-carboxyethyl) benzoic acid; 4PBI = 2-(pyridin-4-yl)-(1H)-
benzoimidazole), have been synthesized by the hydrothermal reaction, which were characterized by
element analyses, FT-IR, UV-Vis diffuse reflection spectra, X-ray single-crystal diffraction, powder X-
ray diffraction, and thermogravimetric analyses (TGA). Complexes 1, 2 and 3 are iso-structural. They
form a one-dimensional (1D) linear chain structure connected by semi-rigid aromatic anion and further
assemble into a three-dimensional (3D) supramolecular framework by π···π stacking and hydrogen
bonding interactions. Complex 4 possesses two bi-nuclear units and displays two-dimensional (2D)
layer which can further extend to a 3D supramolecular architecture via hydrogen bonding and weak
packing interactions. Moreover, the luminescent property of complex 4 was investigated in the solid
state at room temperature.

Keywords: hydrothermal reaction; 3-(1-carboxyethyl) benzoic acid; 2-(pyridin-4-yl)-(1H)-
benzoimidazole; Crystal structures; Luminescence

1. Introduction
During the past few decades, the rational design and construction of metal coordination polymers
(MCPs) based on crystal engineering strategies have received great attention [1] because they possess
novel structures and charming properties with potential applications in various areas such as
photoluminescence [2], ion exchange [3], gas separation and storage [4], catalysis [5] and magnetism
[6]. Typically, luminescent materials have been extensively explored for their diverse functionalities
and application in sensing and optical device [7]. It is well known that the design and synthesis of
MCPs with expected structures are still challenges for researchers. The syntheses of coordination
polymers are mainly dependent on several factors such as centre metal ions [8] organic ligands [9],
inorganic/organic anions [10], the ratios of metals and organic ligands [11], pH values [12], reaction
temperature [13] and reaction time [14]. Among these, the organic ligands and centre metals play vital
roles in the synthesis of MCPs [15]. Nevertheless, how to reasonably construct the expected
architectures with unique properties is still a huge challenge. Selective design of organic ligands is
usually crucial for the formation of these novel coordination frameworks [16]. Up to date, a variety of
MCPs based on the multicarboxylates and flexible N-containing ligands have been constructed [17].
The aromatic multicarboxylate ligands have been intensely investigated due to their strong coordination
ability and structure diversity [18]. However, the development and investigation of MCPs based on the
semi-rigid aromatic carboxylate ligand still remain sparse. In this respect, we have designed one novel
semi-rigid aromatic di-carboxylate ligand, 3-(1-carboxyethyl) benzoic acid (H2L) (Scheme 1), which
display some specific features: i) the H2L ligand has two carboxylic groups that may be completely or
partially deprotonated, including various coordination modes and allowing interesting structures; ii) The
uncoordinated oxygen atoms act as acceptors in hydrogen bonding which can be advantageous to
solidify the whole structures; iii) it can become in the formation of anion, which can make the final
product become neutral structures and improve their thermal properties; iv) the existence of -CH- group
can make one of carboxylate groups freely rotate in order to involve the coordination geometries of the
specific metal ions, which can construct the specific structures of metal coordination polymers. Thus,

the exploring and design of the metal coordination polymers with the semi-rigid aromatic carboxylate
ligand remain a challenge in field of MCPs, which will enrich and extend the content of the
coordination chemistry and metal coordination polymers.
Additionally, the use of neutral auxiliary ligands such as N-donor ligands to the synthetic system of
aromatic acids with metal ions is helpful to construct specific structures with interesting properties [19].
The ligand of 2-(pyridin-4-yl)-1H-benzoimidazole (4PBI) usually act as one of N-donor ligands. The
4PBI ligand can adopt different conformations according to the geometric needs of different metal ions,
and acts as donor and acceptor of hydrogen bondings [20]. Additionally, it can effectively improve the
donated electron ability of benzoimidazole rings and makes it exhibit strong collaborative coordination
ability with organic carboxylate ligands, which would be a powerful ligand for the construction of
MCPs with diverse structures.
Herein, we would like to report the synthesis and characterization of four coordination polymers
based on a semi-rigid aromatic bicarboxylate ligand and N-donor ligand, namely, [M(L)(4PBI)(H2O)]n
(M = Ni, Co and Cu for 1, 2 and 3, respectively) and [Cd(L)(4PBI)]n (4) (H2L = 3-(1-carboxyethyl)
benzoic acid; 4PBI = 2-(pyridin-4-yl)-1H-benzoimidazole), which have been obtained under
hydrothermal conditions. These MCPs have been characterized by FT-IR, UV-Vis spectra, single
crystal X-ray diffraction, and powder X-ray diffraction. To the best of our knowledge, there is no report
that MCPs containing this semi-rigid aromatic carboxylate ligand are synthesized and characterized.
The thermogravimetric analyses (TGA) for complexes 1-4 were also discussed in details. Additionally,
the fluorescence property of complex 4 was studied.
2. Experimental section
2.1. Materials and measurements
Sodium hydroxide was purchased from Tian Jin Guang Cheng Chemical Reagent Limited
Corporation. 1,2-phenylene diamine was purchased from Sinopharm Chemical Reagent Limited
Corporation. Nickel nitrate, Cobalt sulfate, Cadmium sulfate and Copper sulfate were obtained from
Shanghai Chemical Reagent Corporation, Guang Zhou Chemical Reagent Factory, Shang Hai Chemical

Reagent Two Factory and Lai Yang Economic and Technological Development Zone Fine Chemical
Factory, respectively. Polyphosphoric acid (PPA) was purchased from Aladdin Industrial Corporation.
The ligand 3-(1-carboxyethyl) benzoic acid (L) and 2-(pyridin-4-yl)-(1H)-benzoimidazole (4PBI) were
synthesized according to literature procedures [21] [22].The reagents and solvents employed were used
as received without further purification.
Elemental analyses were performed on an Elementar vario EL III microanalyser. The FT-IR
spectra were recorded from KBr pellets in the range 400-4000 cm−1 on a Bruker spectrometer. Powder
X-ray diffraction (PXRD) was recorded on a Bruker D8 Advance diffractometer at 40 kV, 40 mA with
a Cu-target tube and a graphite monochromator. 2θ falls in the range of 5-60°. The experimental PXRD
patterns are in good agreement with the corresponding simulated ones except for the relative intensity
variation because of the preferred orientations of the crystals. Therefore, the phase purity of the as-
synthesized products is substantiated. UV-Vis spectra was recorded on a Shimadzu UV-2550
spectrometer. Diffuse reflectance UV-Vis spectra were recorded on a Shimadzu UV-2550 spectrometer
equipped with an integrating sphere at room temperature in the range of 250-800 nm, in which barium
sulfate (BaSO4) powder was used as a reference. Solid-state fluorescent studies were conducted on a
HITACHI F-4500 system. Thermogravimetric analysis (TGA) data were collected with a TA SDT
Q600 analyzer in N2 at a heating rate of 10 °C min−1 in the range of 20-900 °C.
2.2. Synthesis of 3-(1-carboxyethyl) benzoic acid (H2L)
A mixture of 3-(1-cyanoethyl)benzoic acid (17.5 g, 0.1 mol), NaOH (10 g, 0.25 mol) and distilled
water (100 mL) was refluxed on a steam bath for 7 h. After cooling to room temperature, the mixture
was adjusted to pH 3 by the concentrated HCl solution. Subsequently, the mixture was allowed to cool
to room temperature. Finally, the colorless crystal was collected by vacuum filtration. Yield (94.9%,
o
16.610 g). M.p. 158-160 C. IR (KBr, cm-1): 2997(w), 2895(w), 1699(s), 1583(m), 1456(m), 1416(m),
1286(m), 1230(m), 1060(w), 937(br), 733(w), 686(w), 561(w).
2.3. Synthesis of 2-(pyridin-4-yl)-(1H)-benzoimidazole (4PBI)

Isonicotinic acid (1.477 g, 0.011 mol) and 1, 2-phenylene diamine (1.081 g, 0.010 mol) were
mixed and grinded. To the reactions mixture, polyphosphoric acid (10 ml) was added. Subsequently, the
reaction mixture was heated periodically under the irradiation of microwave. After the completed
reaction, two blocks of ice were added to the mixture. When the reaction mixture was cooled to room
temperature, pure water (30 ml) was poured to the mixture solution. The pH value of the solution was
adjusted to 7 by adding the NaOH solution (10%). Finally, the solid product was collected and further
crystallized from pure water to give a needle-like crystal. Yield (85.9%, 1.675 g). M.p. 226-228 oC. The
microanalyses of compound 4PBI are in good accordance with that reported previously [23].
2.4. Synthesis of [Ni(L)(4PBI)(H2O)]n (1)
.
A mixture of Ni(NO3)2 6H2O (0.0290 g, 0.1 mmol), 4PBI (0.0195 g, 0.1 mmol), NaOH (0.0072 g,
0.18 mmol), H2L (0.0194 g, 0.1 mmol) and water (6 ml) were heated at 160 °C for 3 days in a 15 ml
Teflon-lined vessel container. The reaction mixture was cooled to room temperature at a rate of 5 °C h−1.
Green block crystals of complex 1 suitable for X-ray diffraction analysis were obtained (0.027 g, Yield:
58.18%) based on Ni (NO3)2. Elemental analysis calcd (%) for C22H19NiN3O5 (464.10): C, 56.94; H,
4.13; N, 9.05; found: C, 56.81; H, 4.11; N, 9.01. IR (KBr, cm-1): 3067(w), 2970 (w), 1616(m), 1597(m),
1564(s), 1531(s), 1447(s), 1406(s), 1317(m), 1282(m), 1238(w), 1126(w), 1061(w), 1022(m), 972(m),
916(m), 866(m), 847(w), 818(m), 788(w), 761(m), 743(s), 694(m), 640(w), 563(w), 516(w), 438(w).
2.5. Synthesis of [Co(L)(4PBI)(H2O)]n (2)
.
The preparation of complex 2 was similar to that 1 except that CoSO4 7 H2O (0.0280 g, 0.1 mmol)
.
was instead of Ni(NO3)2 6H2O. The dark-red block crystals of complex 2 suitable for X-ray diffraction
analysis were obtained (0.027 g, Yield: 58.14 %) based on CoSO4. Elemental analysis calcd (%) for
C22H19CoN3O5 (464.34): C, 56.91; H, 4.12; N, 9.05; found: C, 56.86; H, 4.09; N, 9.05. IR (KBr, cm-1):
3065(w), 1614(m), 1541(m), 1437(m), 1400(s), 1315(m), 1281(w), 1227(w), 1142(w), 1105(w),
1063(w), 1018(w), 964(w), 837(w), 814(w), 748(s), 567(m), 520(w), 440(w), 407w).
2.6. Synthesis of [Cu(L)(4PBI)(H2O)]n (3)

.
The synthesis preparation of complex 3 was similar to that of 1 except that CuSO4 5H2O (0.0250 g,
.
0.1 mmol) was instead of Ni(NO3)2 6H2O and the mixture were heated at 120 °C. The dark-green block
crystals of complex 3 suitable for X-ray diffraction analysis were obtained (0.025 g, Yield: 53.31%)
based on CuSO4. Elemental analysis calcd (%) for C22H19CuN3O5 (468.96): C, 56.35; H, 4.08; N, 8.96;
found: C, 56.19; H, 4.10; N, 8.93. IR (KBr, cm-1): 3063(w), 2972(w), 2758(w), 1620(s), 1593(m),
1528(s), 1452(s), 1435(m), 1406(s), 1319(m), 1288(m), 1240(w), 1128(w), 1076(w), 1060(w), 1028(w),
970(m), 914(w), 885(w), 841(w), 814(m), 785(w), 764(m), 748(s), 642(w), 565(w), 525(w), 444(w).
2.7. Synthesis of [Cd(L)(4PBI)]n (4)
.
The synthetic procedure for 4 was similar to that for 1 except that CdSO4 3/8 H2O (0.026 g, 0.1
.
mmol) was instead of Ni(NO3)2 6H2O. The brown needle crystals of complex 4 suitable for X-ray
diffraction analysis were obtained (0.042g, Yield: 84.03 %) based on CdSO4. Elemental analysis calcd
(%) for C22H17CdN3O4 (499.81): C, 52.82; H, 3.40; N, 8.40; found: C, 52.95; H, 3.39; N, 8.43. IR (KBr,
cm-1): 3414(br), 3061(w), 2963(w), 1620(s), 1566(s), 1539(s), 1445(s), 1400(s), 1384(s), 1323(m),
1283(w), 1240(m), 1072(w), 1014(w), 976(w), 910(w), 847(w), 818(m), 777(w), 748(s), 696(m),
660(w), 590(w), 559(w), 513(w), 432(w).
2.8. X-Ray crystallography
Single-crystal structure determinations of the ligand 4PBI and four complexes were measured by
an Agilent Technologies SuperNova Dual diffractometer equipped with graphite–monochromator Mo
Kα radiation (λ = 0.71073 Å). The lattice parameters were obtained by a least-squares refinement of the
diffraction data. All the measured independent reflections were used in the structural analysis, and semi-
empirical absorption corrections were applied using the CrysAlis PRO program [24]. The program
SAINT was used for integration of the diffraction profiles [25]. The structure was solved by direct
methods using the SHELXS program of the SHELXTL package and refined with SHELXL [26]. All
non-hydrogen atoms were located in successive difference Fourier syntheses. The final refinement was
performed by full-matrix least-squares methods with anisotropic thermal parameters for all the non-
hydrogen atoms based on F2. Except hydrogen atom bonded oxygen atom, the hydrogen atoms were

first found in difference electron density maps, and then placed in the calculated sites and included in
the final refinement in the riding model approximation with displacement parameters derived from the
parent atoms to which they were bonded. Special computations for the crystal structure discussions
were carried out with PLATON for Windows [27]. A summary of the crystallographic data and
structure refinements are listed in Table 2. Selected bond lengths and angles are given in Table 3.
Corresponding hydrogen bonding data for 4PBI and its complexes 1-4 are listed in Table 4.
3. Results and discussions
3.1. FT-IR Spectra
The IR spectra of H2L, 4PBI, and complexes 1-4 are shown in Fig. S1. The free ligand H2L
exhibits wide peak characteristic vOH stretching band at 2986 cm-1, while the vOH stretching band of
complexes 1-4 are observed at 2970, 2976, 2972 and 2963 cm-1, respectively. The strong peak at 1691
cm-1 is ascribed to the –COOH functional groups for H2L. It is noteworthy that the carboxylate groups
of L in complexes 1-4 are completely deprotonated because of the absence of the vibration band in the
range of 1760-1680 cm-1 attributed to the –COOH functional groups. The presence of characteristic
bands is observed at 1564 and 1406 cm-1, 1541 and 1400 cm-1, 1593 and 1406 cm-1, and 1539 and 1400
cm-1 for 1-4, respectively, which may be attributed to the asymmetric and symmetric vibrations of the
carboxylate groups. These results reveal that the O atoms of the carboxylate group are engaged in
coordinating to the metal ions in these complexes. In addition, the moderate peaks at 1605, 1589 and
1455 cm-1 suggest the existence of the frame vibration of benzene ring in free H2L ligand, and the
moderate broad peak at 943 cm-1 is attributed to vO-H bending vibration of free H2L ligand. Additionally,
the free ligand of H2L exhibit wide and loose peaks at nearly by 2884 cm-1 characteristic vC-H stretching
band of –CH3 in H2L ligand and the moderate peak of 753 cm-1 is ascribed to δ=CH bending vibration of
H2L ligand.
For another free 4PBI ligand, the characteristic vN-H stretching band at 3431 cm-1 and the weak
peak at 3055 cm-1 suggests that frame vibration of benzene ring in 4PBI ligand. The strong peaks of
1610 and 1436 cm-1 are ascribed to vC=C and vC=N vibration of benzimidazole in 4PBI ligand,

respectively. The moderate peak at 692 cm-1 is assigned to vC-H stretching vibration of pyridine ring in
4PBI ligand. In complexes 1-4, it are observed at 1616 and 761 cm-1 for 1; 1614 and 748 cm-1for 2;
1620 and 748 cm-1 for 3; 1620 and 748 cm-1 for 4, suggesting that there exists the formation of
coordination from nitrogen atom of 4PBI. In addition, the moderate peak at 743 cm-1 is attributed to
δ=CH bending vibration of benzene ring in 4PBI ligand and the weak peak 1112 cm-1 is attributed to δC-H
bending vibration of pyridine ring in 4PBI ligand. Tshe characteristics the stretching and bending
vibration of the -OH groups of the water absorption bands at 3067, 3065 and 3063 cm-1 for complexes
1-3, respectively, providing the evidence for the coordinated water molecules.
3.2. UV–Vis absorbance and diffuse reflectance spectra
The UV–Vis spectra [28] of the free ligands H2L and 4PBI in N,N-dimethylforamide (DMF)
solution are presented in Table 1 and Fig. 2a. The UV–Vis spectrum of the free ligands H2L and 4PBI
exhibits one absorption peak at 278 and 313 nm, respectively, which can be assigned to the π–π*
transition.
To evaluate the electronic absorbance feature of complexes 1-4, the diffuse reflectance spectra
were obtained using BaSO4 as standard at room temperature. The experimental results are depicted in
Fig. 2b. Complexes 1-3 display obviously the absorbance bands in the uvioet to visible region; while
there exist the bands only falling in the uvioet range for complex 4. In the electronic spectra, all of
complexes display the bands at the uvioet region, which are observed at 263 and 321 nm for complex 1,
267 and 322 for 2, 271 and 319 nm for 3, 271 and 320 nm for 4, respectively. The bands at about 270
nm can be assigned to the π-π* transition of L ligand, while the UV bands found originating in the π-π*
transition of the 4PBI are obseved in the expected positions at about 320 nm.
As illustrated in Fig. 2b, for complex 1, one broad band falling in the visible region in the electronic
spectra are observed at 552 nm, which can be attributed to the [3A2g→3T1g(F)] transition [29]. The
spectrum of complex 2 exhibits a broad band at 623 nm that have intensities consistent with spin-
allowed d–d transitions, which may be tentatively assigned to the transition of [4T1g(F)→ 4T1g(P)] [30].
On the basis of diffuse reflection spectrum of complex 3, distorted octahedral geometry around Cu(II)

ion is suggested. The spectrum shows a low intensity broad band at 523 nm which is ascribed to the [2Eg
→2T2g(F)] transition [31].
3.3. Structure description of complexes 1, 2 and 3
The single crystal X-ray structural analysis reveals that complexes 1-3 are a one-dimension (1D)
polymer and crystallize in the form of the monoclinic space group P21/n, and they are isostructural
structures. As a matter of convenience, complex 1 is employed as a representative structure to be
described in details. As shown in Fig. 3a, the asymmetric unit contains one Ni (II) ion, one 4PBI ligand,
one L ligand, and one coordinated water molecule. The Ni(II) centre takes a distorted octahedral
geometry via coordinating to one pyridine-yl nitrogen atom (N1) of one 4PBI ligand, four carboxylic
oxygen atoms (O1A, O2A, O3 and O4) of two L ligands plus one oxygen atom (O1W) of one
coordinated water molecule. The Ni-O bond distances in 1 range from 2.0330(2)–2.1540(2) Å and the
Ni-N bond distance is 2.0580(2) Å (Table 3). The average Ni-O distance is 2.0964 Å, which are slightly
longer than the common Ni-O distance 2.06 Å, and is in agreement with those found in documents [32].
The Co-O bond distances in 2 fall in the range of 2.0450(2)–2.1957(18) Å and the Co-N bond length is
2.0990(2) Å. The average Co-O distance is 2.1286 Å and Co-N distance is 2.0990 Å, which is slightly
longer than the common Co-O and Co-N distances of 1.9400 and 1.9600 Å, respectively. The Cu-O
distances in 3 fall in the range of 1.9720(3)–2.4640(2) Å and the Cu-N distance is 1.9940(3) Å (Table 3).
The average bond length of Cu-O is 2.1662 Å, which is in agreement with those found in literatures
published previously [32]. As shown in Fig. 3b, each adjoining pair of Ni (II) ions is connected by L
ligands to form a 1D chain along the crystallographic b axis.
The supramolecular structures mainly depend on three kinds of interactions: the coordination
bonds, the strong hydrogen bonds, and packing interactions. The O–H···O intermolecular hydrogen
bond is generated through the oxygen atoms from the coordinated water molecules and the carboxylic
oxygen atoms form the L ligands. These bond lengths and angles are 1.92(3) Å and 168(3)° for 1,
1.88(3) Å and 167(3)° for 2, and 1.80(3) Å and 174(4)° for 3, respectively, through which 1D polymeric

chains are extended to a two-dimensional (2D) supramolecular layer along the crystallographic c axis
(Fig. 3c).
In an addition, there exist two kinds of O–H···N hydrogen bonds and three kinds of C–H···O
hydrogen bonds in 1-3 (Fig. 3d and Table 4): (a) The O–H···N intermolecular hydrogen bonds occur
between the oxygen atoms of the coordinated water molecules and the nitrogen atoms of the 4PBI
ligands. These bond lengths and bond angles are 1.88(2) Å and 170(4)° for 1, 1.87(2) Å and 170(3)° for
2, and 1.86(2) Å and175(5)° for 3, respectively. (b) The O–H···N intermolecular hydrogen bondings
generate between the oxygen atoms from the L ligands and nitrogen atoms of the 4PBI ligands. These
bond lengths and bond angles are 1.84(2) Å and 170(4)° for 1, 1.83(2) Å and 171(3)° for 2, and 1.81(3)
Å and 176(3)° for 3, respectively. (c) The C–H···O intermolecular hydrogen bondings originate from the
carbon atoms from the 4PBI ligands and oxygen atoms of the L ligands. These bond lengths and bond
angles is 2.35 Å and 125° for 1, and these bond lengths and bond angles fall in the range of are 2.40–
2.54 Å and 126–160° for 2, and 2.48–2.54 Å and 130–160° for 3, respectively. (d) The C–H···O
intermolecular hydrogen bondings construct between the carbon atoms from the 4PBI ligands and
oxygen atoms of the coordination water molecules. These bond lengths and bond angles are 2.60 Å and
156° for 1, 2.57 Å and 157° for 2, and 2.53 Å and 160° for 3, respectively. Furthermore, another type of
C–H···O intermolecular hydrogen bond is generated through the oxygen atoms from L ligands and the
carbon atoms from L ligands for 1. These bond lengths and bond angles are 2.58Å and 140° for 1, Apart
from these hydrogen bonding interactions, it is worth noting that there exist two kinds of weak π···π
packing interactions between the aromatic rings. One occurs between the imidazole groups and phenyl
ones (3.6010(17), 3.5843(16) and 3.636(2) Å for 1, 2 and 3, respectively) and the other do between two
phenyl groups (3.6434(16), 3.6663(14) and 3.6183(17) Å for 1, 2 and 3, respectively). Additionally,
k
another types of π···π packing interactions are observed in 3 (Cg(2)···Cg(1)k, 2.6365(15) Å, x, y, z;
l
Cg(3)···Cg(1)l, 2.6365(15) Å, -1/2+x, 1/2–y, -1/2+z). Finally, the 3D supramolecular framework is
obtained by a variety of hydrogen bonds and π···π stacking interactions (Fig.3d).
3.4. Structure description of complex 4

The results of the X-ray crystallographic analysis illustrate that complex 4 is a 2D network and it
crystallizes in the triclinic space group P-1. As depicted in Fig. 4a, the asymmetric unit of complex 4 is
made of two unique cadmium ions, three L ligands and two 4PBI ligands. The central Cd1 ion is seven
coordinated by two nitrogen atoms of two different 4PBI ligands and five oxygen atoms of three L
ligands. Seven O-donor atoms from L ligands form at the base plane of the distorted pentagonal
bipyramid, and the vertexes of the distorted pentagonal bipyramid are made of two nitrogen atoms from
two 4PBI ligands. The Cd1 center derivate from the base plane about 0.0500(2) Å. Similar to that of
Cd1, Cd2 adopts distorted pentagonal bipyramid with five oxygen atoms of three L ligands and two
nitrogen atoms of two different 4PBI ligands. The base plane of the pentagonal bipyramid consists of
seven oxygen atoms from three L ligands, and the apexes of bipyramid are occupied by two nitrogen
atoms from two 4PBI ligands. The central Cd2 ion is slightly from the base plane about 1.5566(3) Å.
The bond distances of Cd-O and Cd-N fall in the range of 2.251(3)–2.481 Å and 2.318(4)–2.360(3) Å
(Table 3), respectively, which are normal values in some documents [32]. The bond angles of O-Cd-O,
O-Cd-N and N-Cd-N in range of are 54.26(8)–157.12(8)°, 82.19(11)–109.76(12)° and 163.86(12)–
164.60(12)°, respectively. Interestingly, there are two kinds of coordination modes for L ligands: one
ligand acts as a bi-dentate mode; another does as the mono-dentate mode. As a result, one binuclear Cd
structure was formed (Fig. 4a). Two Cd centers (Cd1 and Cd2) are connected by one 4PBI ligand and
one L ligand (Fig. 4a). In other words, these binuclear units are further extended to a 2D layer through
4PBI and L ligands (Fig. 4b).
Interestingly, it is observed that there exist four kinds of hydrogen bonds (Fig. 4c and Table 4): (a)
e
The intermolecular hydrogen bonds of N–H···O (N(3)–H(3)···O(2)e 1.92 Å, 1-x, 2-y, -z; N(6)–
a
H(6)···O(6)a 1.94 Å, 1-x, 1-y, 1-z) (Table 4) are generated through nitrogen atoms of 4PBI ligand and
oxygen atoms of L ligand. (b)The intermolecular hydrogen bondings of C–H···O (C(7)–H(7)···O(5)f 2.49
f
a
Å, 1-x, 2-y, 1-z; C(17)–H(17)···O(1)a 2.51 Å, 1-x, 1-y, 1-z.) are observed through carbon atoms of L
ligand and oxygen atoms of L ligand. (c) The hydrogen bondings of C–H···O (C(21)–H(21)···O(8)a 2.45
a
f
f
Å, 1-x, 1-y, 1-z; C(24)–H(24)···O(2) f 2.57 Å, 1-x, 2-y, -z; C(33)–H(33)···O(3)f 2.42 Å, 1-x, 2-y, 1-z;

g
a
C(34)–H(34)···O(2)g 2.34 Å, x, y, 1+z; C(36)–H(36)···O(6)a 2.58 Å, 1-x, 1-y, 1-z; C(22)–H(22)···O(6)
2.36 Å) occur from L ligand and carbon atoms of 4PBI ligand.
Except from these hydrogen bonds, there exist weak C–H···π interactions between C13–H13F and
j
the phenyl ring (C27-C32) (j -x, 2-y, 1-z), where the distance of C–H···π is 3.450 Å and the angle is
124°. These supramolecular interactions extend the 2D supramolecular layers to a 3D supramolecular
framework along the crystallographic b axis (Fig. 4c).
To investigate the topological structure of the complex 4, the Cd(II) atoms can be regarded as five
connecting nodes, whereas the L, 4PBI ligands act as linear linker which bridges two adjacent Cd(II)
atoms. Thus, the whole network is simplified to the (3,5), (4,5), (6,5) topological structure, which is
same to those found in some 2D MCPs (Fig. 4d) [33]. Interestingly, the present topological network is
non-uniform topological structure, which is obviously different from those documented in literatures
[34].
3.5. Coordination modes of L in complexes 1-4
According to the structure descriptions mentioned above, we could find that the two carboxylate
groups of L ligand exhibit two kinds of coordination modes (Scheme 2). In complexes 1-3, L is
completely deprotonated. The coordination modes of two carboxyl groups in L are same and display a
µ2-η1:η1:η1:η1 coordination mode (Scheme 2a), which coordinates with metal ions such as, Ni2+, Co2+,
and Cu2+ for 1-3, respectively. However, in complex 4, the L ligand is partially deprotonated, and the
two carboxyl groups of L adopt the completely different coordination modes, that is, µ2-η1:η1:η1:η1
(Scheme 2a) and µ3-η1:η1:η2:η1 (Scheme 2b). From the viewpoint of the present results, it is obvious that
the diverse coordination modes of carboxylate groups resulted in the structural differences of complexes
1-4.
3.6. Effects of the central metals on the structures
As mentioned above, we could see that the central metal ions play important roles in the final
structures of 1-4. The difference coordination numbers of central metal ions are an important reason for
the complex with different structural motifs. The coordination number (CN) of Cd ions in 4 (CN = 7) is

larger than that of Ni ions, Co ions and Cu ions in 1-3 (CN = 6), which may be attributed to the fact that
the radius of Cd ions is larger than that of Ni ions, Co ions and Cu ions. Additionally, in complexes 1-3,
the coordination numbers around metal centers are uniform, which may be assigned to the similarity
radius of Ni ions, Co ions and Cu ions. The present results provide us with the fact that suitable metal
ions may be a good candidate for the construction of MCPs with diverse dimensionalities.
3.7. Effects of 4PBI ligands on the structures
Apart from the effects of the coordination modes for L and the metal ions, the 4PBI ligand show
different coordination modes in complexes 1-4, respectively (Scheme 2c and 2d). As illustrated in
Scheme 2c, in complexes 1-3, there exists mono-dentate mode for 4PBI ligand. However, bis-dentate
bridging mode of 4PBI ligand is observed in complex 4 (Scheme 2d). The present results indicate that
the 4PBI ligands also significant effects on the formation of the final structures. For complexes 1-3,
they have a 1D chain. When the 4PBI ligands were conducted to the reaction system of 1-3, a 3D
supramolecular framework network is found. Complex 4 exhibits a 2D layer structure. When the 4PBI
ligands were introduced into the reaction system of 4, another 3D supramolecular architecture is
observed. Obviously, the auxiliary ligands also play an important role in the construction of the final
structures.
3.8. Powder X-ray diffraction (XRD)
To confirm the pure phase of these complexes, PXRD experiment has been carried out. As
illustrated in Fig.5-8, the peak positions of the simulated and experimental PXRD patterns are in good
accordance with each other, which illustrates the phase purity of the products [35].
3.9. Thermogravimetic analyses (TGA)
In order to characterize the compounds more fully in terms of thermal stability, the thermal
behaviors of 1–4 were examined by TGA. As illustrated in Fig. 9-12, all of the TGA curves for 1-3 are
o
similar. The TGA curves show that first weight loss occurs in the range of 29-164 C (obsd 1%, calcd
o
o
3.9%) for 1, 31-166 C (obsd 1%, calcd 3.9%) for 2, and 27-144 C (obsd 1%, calcd 3.8%) for 3,
respectively, which corresponds to the loss of coordination water molecules. The present results indicate

that there exist strong hydrogen bonds among the water molecules. The framework starts to collapse in
the temperature range of 247-800 oC (obsd 77%, calcd 78%) for 1, 206-800 oC (obsd 60%, calcd 78.3%)
o
for 2, and 184-800 C (obsd 75%, calcd 82%) for 3, respectively, revealing the departure of organic
ligands. The remaining weight is attributed to the final product of Ni2O3 (obsd 22%, calcd 18%) for 1,
Co2O3 (obsd 39%, calcd 17.8%) for 2, and CuO (obsd 24%, calcd 17%) for 3, respectively. The TGA
o
curve of 4 reveals that first weight loss falls from 190 to 538 C (obsd 97.5%, calcd 74.3%), showing
the departure of organic ligands. Finally, the final residual can be assigned to the formation of CdO
(obsd 25%, calcd 25.7%) for 4.
3.10. Luminescent spectra
The luminescence properties of complexes containing d10 metals have been intensely researched
owing to their potential applications in photochemistry and sensors [36]. Therefore, in this paper, the
photoluminescence properties of complex 4, L, and 4PBI were investigated in the solid state at room
temperature. As shown in Fig. 13, the main emission peak of L is found at 414 nm (λex = 286 nm). In an
addition, the two maximum emission peaks of 4PBI are located at 411 nm and 516 nm (λex = 280 nm),
respectively. The emission bands of these free ligands are probably caused by the π* → π or π* → n
transitions [37]. Complex 4 displays emission band located at 459 nm with excitation at 317 nm.
Compared with the emission spectrum of L and 4PBI ligands, red-shifts of emission bands for 4 have
been observed. Since the Cd2+ ions are difficult to oxidize or to reduce due to their d10 configuration, the
emission of complex 4 is neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal charge
transfer (LMCT) in nature [38]. The emission of the complex may be assigned to the intraligand
fluorescence emission. The present results indicate that complex 4 can be one of promising candidates
for luminescent materials.
4. Conclusions
In summary, we have successfully designed and developed a set of metal coordination polymers based
on the semi-rigid aromatic carboxylate group, which display interesting structural motifs with different
dimensionalities. The present results indicate that the metal centers and the bridging ligand play a key

role in final structures, which confirms the significant potential of constructing structures based on
semi-rigid aromatic acid and N-donor ligands, and provides an animated example to construct novel
metal coordination polymers. Furthermore, the fluorescent property of 4 makes it one of the promising
candidates for photoluminescent material. Currently, the design and explore of other metal coordination
polymers based on the semi-rigid aromatic carboxylate groups, which show the specific motifs and
interesting properties, is on the way at our laboratory.
Acknowledgements
This work was financially supported by the Project of Shandong Province Higher Educational Science
and Technology Program (J09LB03), Shandong Distinguished Middle-aged Young Scientist
Encouragement and Reward Foundation (BS2011CL034), and Program for Scientific Research
Innovation Team in Colleges and Universities of Shandong Province. Prof. Yue-Zhi Cui gratefully
thanks to the National Natural Science Foundation of China (No. 21276149).
Appendixes A. supplementary material
CCDC 994678-994681 contain the supplementary crystallographic data of the ligand and its complex
for
this
article.
These
data
can
be
obtained
free
of
charge
via
http://www.ccdc.cam.ac.uk/data_request/cif, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK. Telephone: +44 01223 762910 Facsimile: +44 01223 336033;
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.
References
[1]
(a) V. N. Vukotic, S. J. Loeb, Chem. Soc. Rev. 41 (2012) 5896; (b) O. M. Yaghi, M. O’Keeffe,
N. W. Ockwig, H. K. Chae, M. Eddaoudi, J. Kim, Nature 423 (2003) 705; (c) J.-P. Zhang, Y.-B.
Zhang, J.-B. Lin, X.-M. Chen, Chem. Rev. 112 (2012) 1001; (d) M. Li, D. Li, M. O’Keeffe, O.
M. Yaghi, Chem. Rev. 114 (2014) 1343; (e) X. Kong, H. Deng, F. Yan, J. Kim, J. A. Swisher, B.
Smit, O. M. Yaghi, J. A. Reimer, Science 341 (2013) 882.
[2]
(a) J. Heine, K. Muller-Buschbaum, Chem. Soc. Rev. 42 (2013) 9232; (b) M. D. Allendorf, C. A.
Bauer, R. K. Bhakta, R. J. T. Houk, Chem. Soc. Rev. 38 (2009) 1330; (c) J. Rocha, L. D. Carlos,
F. A. A. Paz, D. Ananias, Chem. Soc. Rev. 40 (2011) 926; (d) Y. Cui, Y. Yue, G. Qian, B. Chen,
Chem. Rev. 112 (2012) 1126; (e) L. Zhou, J. Zhang, Y. Z. Li, H. B. Du, CrystEngComm 15

(2013) 8989; (f) X. H. Chang, Y. Zhao, M. L. Han, L. F. Ma, L. Y. Wang, CrystEngComm 16
(2014) 6417.
[3]
[4]
(a) B. Manna, A. K. Chaudhari, B. Joarder, A. Karmakar, S. K. Ghosh, Angew. Chem. Int. Ed.
52 (2013) 998; (b) A. Aijaz, P. Lama, P. K. Bharadwaj, Inorg. Chem. 49 (2010) 5883; (c) L. Mi,
H. Hou, Z. Song, H. Han, H. Xu, Y. Fan, S.-W. Ng, Cryst. Growth Des. 7 (2007) 2553.
(a) N. A. Ramsahye, G. Maurin, S. Bourrelly, P. L. Llewellyn, T. Devic, C. Serre, T. Loiseau, G.
Ferey, Adsorption 13 (2007) 461; (b) M. Zhang, Z. J. Pu, X. L. Chen, X. L. Gong, A. X. Zhu, L.
M. Yuan, Chem. Commun. (Camb.) 49 (2013) 5201; (c) S. J. Alesaadi, F. Sabzi, Int. J.
Hydrogen Energy 40 (2015) 1651; (d) K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald,
E. D. Bloch, Z. R. Herm, T.-H. Bae, J. R. Long, Chem. Rev. 112 (2012) 724; (e) J.-R. Li, J.
Sculley, H.-C. Zhou, Chem. Rev. 112 (2012) 869; (f) H. Furukawa, K. E. Cordova, M. O'Keeffe,
O. M. Yaghi, Science 341 (2013) 974; (g) B. Seoane, J. Coronas, I. Gascon, M. E. Benavides, O.
Karvan, J. Caro, F. Kapteijn, J. Gascon, Chem. Soc. Rev. 44 (2015) 2421.
[5]
(a) J. W. Liu, L. F. Chen, H. Cui, J. Y. .Zhang, L. Zhang, C. Y. Su, Chem. Soc. Rev. 43 (2014)
6011; (b) B. Gole, A. K. Bar, A. Mallick, R. Banerjee, P. S. Mukherjee, Chem. Commun.
(Camb.) 49 (2013) 7439; (c) A. Dhakshinamoorthy, H. Garcia, Chem. Soc. Rev. 43 (2014)
5750; (d) M. Yoon, R. Srirambalaji, K. Kim, Chem. Rev. 112 (2012) 1196; (e) A. H. Chughtai,
N. Ahmad, H. A. Younus, A. Laypkov, F. Verpoort, Chem Soc Rev 44 (2015) 6804; (f) L. Liu,
Z.-B. Han, S.-M. Wang, D.-Q. Yuan, S. W. Ng, Inorg. Chem. 54 (2015) 3719; (g) Z. H. Xu, L. L.
Han, G. L. Zhuang, J. Bai, D. Sun, Inorg. Chem. 54 (2015) 4737; (h) H. Zhang, J. H. Lv, K. Yu,
C. M. Wang, C. X. Wang, D. Sun, B. B. Zhou, Dalton Trans. 44 (2015) 12839; (i) J.-H. Wang,
G.-M. Tang, Y.-T. Wang, Y.-Z. Cui, J.-J. Wang, S. W. Ng, Dalton Trans. 44 (2015) 17829; (j)
J.-H. Wang, E. Zhang, G.-M. Tang, Y.-T. Wang, Y.-Z. Cui, S. W. Ng, J. Solid State Chem. 241
(2016) 86.
[6]
(a) E. Coronado, G. Minguez Espallargas, Chem. Soc. Rev. 42 (2013) 1525; (b) M. Kurmoo,
Chem Soc Rev 38 (2009) 1353; (c) C. W. Ingram, L. Liao, J. Bacsa, I. Harruna, D. Sabo, Z. J.
Zhang, Cryst. Growth Des. 13 (2013) 1131; (d) G. W. Xu, Z. L. Wang, G. X. Wen, S. S. Guo, D.
S. Li, J. Zhang, Inorg. Chem. Commun. 55 (2015) 17; (e) M.-H. Zeng, Z. Yin, Y.-X. Tan, W.-X.
Zhang, Y.-P. He, M. Kurmoo, J. Am. Chem. Soc. 136 (2014) 4680; (f) C.-F. Wang, R.-F. Li, X.-
Y. Chen, R.-J. Wei, L.-S. Zheng, J. Tao, Angew. Chem. Int. Ed. 54 (2015) 1574.
(a) S. J. Liu, Y. B. Huang, Z. J. Lin, X. F. Li, R. Cao, RSC Advances 3 (2013) 9279; (b) X. Z.
Song, S. Y. Song, C. Qin, S. Q. Su, S. N. Zhao, M. Zhu, Z. M. Hao, H. J. Zhang, Cryst. Growth
Des. 12 (2012) 253; (c) L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. Van Duyne, J.
T. Hupp, Chem. Rev. 112 (2012) 1105; (d) A. Ramdass, V. Sathish, M. Velayudham, P.
Thanasekaran, S. Umapathy, S. Rajagopal, RSC Adv. 5 (2015) 38479.
(a) H. L. Jiang, B. Liu, Q. Xu, Cryst. Growth Des. 10 (2010) 806; (b) Y. Yang, J. Yang, P. Du,
Y. Y. Liu, J. F. Ma, CrystEngComm 16 (2014) 1136; (c) L. L. Wen, F. M. Wang, X. K. Leng, M.
M. Wang, Q. J. Meng, H. Z. Zhu, J. Inorg. Organomet. Polym. 20 (2010) 313; (d) Y.-T. Wang,
G.-M. Tang, W.-Z. Wan, Y. Wu, T.-C. Tian, J.-H. Wang, C. He, X.-F. Long, J.-J. Wang, S. W.
Ng, CrystEngComm (2012) 3802; (e) Y.-T. Wang, S.-C. Yan, G.-M. Tang, C. Zhao, T.-D. Li,
Y.-Z. Cui, Inorg. Chim. Acta 376 (2011) 492; (f) Y. T. Wang, G. M. Tang, Y. Wu, X. Y. Qin, D.
W. Qin, J. Mol. Struct. 831 (2007) 61.
[7]
[8]
[9]
(a) A. Y. Robin, K. M. Fromm, Coord. Chem. Rev. 250 (2006) 2127; (b) Y. T. Wang, G. M.
Tang, Y. Q. Wei, T. X. Qin, T. D. Li, J. B. Ling, X. F. Long, Inorg. Chem. Commun. 12 (2009)
1164; (c) Y. T. Wang, G. M. Tang, T. D. Li, J. C. Yu, Y. Q. Wei, J. B. Ling, X. F. Long, Aust. J.
Chem. 63 (2010) 336.
[10] (a) H. Wang, D. Zhang, D. Sun, Y. Chen, L.-F. Zhang, L. Tian, J. Jiang, Z.-H. Ni, Cryst. Growth
Des. 9 (2009) 5273; (b) H. Y. Bai, J. F. Ma, J. Yang, Y. Y. Liu, W. Hua, J. C. Ma, Cryst.
Growth Des. 10 (2010) 995; (c) R.-J. Wei, J. Tao, R.-B. Huang, L.-S. Zheng, Eur. J. Inorg.
Chem. (2013) 916.
[11] X. H. Bu, W. Chen, W. F. Hou, M. Du, R. H. Zhang, F. Brisse, Inorg. Chem. 41 (2002) 3477.

[12] (a) M. L. Han, X. H. Chang, X. Feng, L. F. Ma, L. Y. Wang, CrystEngComm 16 (2014) 1687;
(b) D. C. Zhong, W. G. Lu, J. H. Deng, CrystEngComm 16 (2014) 4633.
[13] (a) Y. B. Go, X. Wang, E. V. Anokhina, A. J. Jacobson, Inorg. Chem. 44 (2005) 8265; (b) J. H.
Wang, G. M. Tang, Y. T. Wang, T. X. Qin, S. W. Ng, CrystEngComm 16 (2014) 2660; (c) L.
Cheng, J. Wang, Q. Qi, X. Zhang, H. Yu, S. Gou, L. Fang, CrystEngComm 16 (2014) 10056.
[14] P. M. Forster, N. Stock, A. K. Cheetham, Angew. Chem. Int. Ed. 44 (2005) 7608.
[15] (a) B. Chen, L. Wang, Y. Xiao, F. R. Fronczek, M. Xue, Y. Cui, G. Qian, Angew. Chem. Int. Ed.
48 (2009) 500; (b) T. Li, X. Liu, Z.-P. Huang, Q. Lin, C.-L. Lin, Q.-G. Zhan, X.-D. Xu, Y.-P.
Cai, Inorg. Chem. Commun. 39 (2014) 70; (c) Y. T. Wang, G. M. Tang, Z. W. Qiang,
Polyhedron 26 (2007) 4542; (d) Y. T. Wang, T. X. Qin, C. Zhao, G. M. Tang, T. D. Li, Y. Z.
Cui, J. Y. Li, J. Mol. Struct. 938 (2009) 291.
[16] (a) B. H. Ye, M. L. Tong, X. M. Chen, Coord. Chem. Rev. 249 (2005) 545; (b) Y.-Z. Zheng, Z.
Zheng, X.-M. Chen, Coord. Chem. Rev. 258–259 (2014) 1; (c) N. N. Adarsh, P. Dastidar, Chem.
Soc. Rev. 41 (2012) 3039; (d) F. A. Almeida Paz, J. Klinowski, S. M. F. Vilela, J. P. C. Tome, J.
A. S. Cavaleiro, J. Rocha, Chem. Soc. Rev. (2012) 1088; (e) Y. He, B. Li, M. O'Keeffe, B.
Chen, Chem. Soc. Rev. 43 (2014) 5618; (f) S. Kitagawa, K. Uemura, Chem. Soc. Rev. 34 (2005)
109; (g) F. A. A. Paz, J. Klinowski, S. M. F. Vilela, J. P. C. Tome, J. A. S. Cavaleiro, J. Rocha,
Chem. Soc. Rev. 41 (2012) 1088; (h) Q. L. Zhu, Q. Xu, Chem. Soc. Rev. 43 (2014) 5468; (i) H.-
L. Jiang, T. A. Makal, H.-C. Zhou, Coord. Chem. Rev. 257 (2013) 2232; (j) C. Pettinari, A.
Tăbăcaru, S. Galli, Coord. Chem. Rev. 307, Part 1 (2016) 1; (k) C. B. Aakeroy, N. R.
Champness, C. Janiak, CrystEngComm 12 (2010) 22.
[17] (a) L. P. Zhang, J. F. Ma, J. Yang, Y. Y. Pang, J. C. Ma, Inorg. Chem. 49 (2010) 1535; (b) Y. G.
Ran, J. X. Xie, Y. J. Mu, L. F. Zhang, B. Han, Inorg. Chim. Acta 425 (2015) 17; (c) S. Y. Zhang,
Z. J. Zhang, W. Shi, B. Zhao, P. Cheng, Inorg. Chim. Acta 363 (2010) 3784; (d) Y. Yan, C. D.
Wu, X. He, Y. Q. Sun, C. Z. Lu, Cryst. Growth Des. 5 (2005) 821; (e) J.-H. Wang, G.-M. Tang,
T.-X. Qin, S.-C. Yan, Y.-T. Wang, Y.-Z. Cui, S. Weng Ng, J. Solid State Chem. 219 (2014) 55;
(f) Y.-Q. Zheng, H.-L. Zhu, J.-L. Lin, W. Xu, F.-H. Hu, J. Solid State Chem. 201 (2013) 1; (g) L.
Cheng, J. Wang, H.-Y. Yu, X.-Y. Zhang, S.-H. Gou, L. Fang, J. Solid State Chem. 221 (2015)
85.
[18] (a) C. Ding, X. Rui, C. Wang, Y. Xie, CrystEngComm 16 (2014) 1010; (b) H. S. Wang, W. Shi,
J. Xia, H. B. Song, H. G. Wang, P. Cheng, Inorg. Chem. Commun. 10 (2007) 856; (c) W. Sun, J.
Liu, H. Liu, Z. Liu, Polyhedron 109 (2016) 1.
[19] (a) Y. H. Zhou, J. Inorg. Organomet. Polym. 23 (2013) 1189; (b) C.-C. Wang, J.-H. Wang, G.-M.
Tang, Y.-T. Wang, Y.-Z. Cui, S. W. Ng, J. Coord. Chem. 68 (2015) 3918; (c) Y. T. Wang, G. M.
Tang, J. Coord. Chem. 60 (2007) 2139; (d) Y. T. Wang, G. M. Tang, Y. C. Zhang, W. Z. Wan, J.
C. Yu, T. D. Li, Y. Z. Cui, J. Coord. Chem. 63 (2010) 1504; (e) Y. T. Wang, W. Z. Wan, G. M.
Tang, Z. W. Qiang, T. D. Li, J. Coord. Chem. 63 (2010) 206.
[20] (a) Y. Yang, M. H. Zeng, L. J. Zhang, H. Liang, J. Coord. Chem. 62 (2009) 886; (b) C. K. Xia,
C. Z. Lu, X. Y. Wu, Q. Z. Zhang, H. J. Zhang, D. M. Wu, Polyhedron 26 (2007) 941; (c) N.
Kundu, A. Audhya, S. M. T. Abtab, S. Ghosh, E. R. T. Tiekink, M. Chaudhury, Cryst. Growth
Des. 10 (2010) 1269; (d) C. J. Wang, K. F. Yue, Z. X. Tu, L. L. Xu, Y. L. Liu, Y. Y. Wang,
Cryst. Growth Des. 11 (2011) 2897; (e) M. X. Li, H. Wang, S. W. Liang, M. Shao, X. He, Z. X.
Wang, S. R. Zhu, Cryst. Growth Des. 9 (2009) 4626; (f) X. P. Li, M. Pan, S. R. Zheng, Y. R. Liu,
Q. T. He, B. S. Kang, C. Y. Su, Cryst. Growth Des. 7 (2007) 2481; (g) H. Wang, M. X. Li, M.
Shao, X. He, Polyhedron 26 (2007) 5171; (h) F. Li, Y. Kang, Y. M. Dai, J. A. Zhang, Inorg.
Chem. Commun. 14 (2011) 228; (i) T. Lu, X. Xu, H. Li, Z. Li, X. Zhang, J. Ou, M. Mei, Dalton
Trans. 44 (2015) 2267; (j) I. Elguraish, K. Zhu, L. A. Hernandez, H. Amarne, J. Luo, V. N.
Vukotic, S. J. Loeb, Dalton Trans. 44 (2015) 898; (k) C. K. Xia, C. Z. Lu, X. Y. Wu, L. J. Chen,
Q. Z. Zhang, J. J. Zhang, D. M. Wu, Inorg. Chim. Acta 359 (2006) 4639; (l) L. J. Chen, X. He,
C. K. Xia, Q. Z. Zhang, J. T. Chen, W. B. Yang, C. Z. Lu, Cryst. Growth Des. 6 (2006) 2076;
(m) C. K. Xia, C. Z. Lu, Q. Z. Zhang, X. He, J. J. Zhang, D. M. Wu, Cryst. Growth Des. 5
(2005) 1569.

[21] M. Allegretti, R. Bertini, M. C. Cesta, C. Bizzarri, R. D. Bitondo, V. D. Cioccio, E. Galliera, V.
Berdini, A. Topai, G. Zampella, V. Russo, N. D. Bello, G. Nano, L. Nicolini, M. Locati, P.
Fantucci, Saverio Florio, F. Colotta, J. Med. Chem. 48 (2005) 4312.
[22] S. Park, J. Jung, E. J. Cho, Eur. J. Org. Chem. 2014 (2014) 4148.
[23] S. Y. Lin, Y. Isome, E. Stewart, J. F. Liu, D. Yohannes, L. B. Yu, Tetrahedron Lett. 47 (2006)
2883.
[24] CrysAlisPro, Oxford Diffraction Poland (2009).
[25] Bruker, AXS, SAINT Software Reference Manual; Madison: WI (1998).
[26] (a) G. M. Sheldrick, SHELXTL NT Version 5.1. Program for Solution and Refinement of
Crystal Structures; University of Göttingen: Germany (1997); (b) G. M. Sheldrick, Acta
Crystallogr. Sect. A 64 (2008) 112.
[27] A. L. Spek, J. Appl. Cryst. 36 (2003) 7.
[28] T. Mathavan, S. Umapathy, M. A. Jothirajan, A. M. F. Benial, Spectrosc. Lett. 45 (2012) 588.
[29] (a) B. K. Das, S. J. Bora, M. Chakrabortty, L. Kalita, R. Chakrabarty, R. Barman, J. Chem. Sci.
118 (2006) 487; (b) E. Viñuelas-Zahínos, M. A. Maldonado-Rogado, F. Luna-Giles, F. J.
Barros-García, Polyhedron 27 (2008) 879.
[30] (a) M. A. Maldonado-Rogado, E. Viñuelas-Zahínos, F. Luna-Giles, F. J. Barros-García,
Polyhedron 26 (2007) 5210; (b) F. J. Barros-García, A. Bernalte-García, F. Luna-Giles, M. A.
Maldonado-Rogado, E. Viñuelas-Zahínos, Polyhedron 25 (2006) 52; (c) E. Viñuelas-Zahínos, F.
Luna-Giles, P. Torres-García, A. Bernalte-García, Polyhedron 28 (2009) 4056.
[31] M. V. Angelusiu, S. F. Barbuceanu, C. Draghici, G. L. Almajan, Eur. J. Med. Chem. 45 (2010)
2055.
[32] X.-M. Chen, J.-W. Cai, Single-Crystal Structural Analysis Principles and Practices; the Science
Press: Beijing (2003).
[33] D. Sun, L. L. Han, S. Yuan, Y. K. Deng, M. Z. Xu, D. F. Sun, Cryst. Growth Des. 13 (2013) 377.
[34] (a) Z. Su, J. Fan, T.-a. Okamura, W. Y. Sun, N. Ueyama, Cryst. Growth Des. 10 (2010) 3515;
(b) H. Furukawa, N. Ko, Y. B. Go, N. Aratani, S. B. Choi, E. Choi, A. O. Yazaydin, R. Q. Snurr,
M. O'Keeffe, J. Kim, O. M. Yaghi, Science 329 (2010) 424.
[35] A. C. Tella, S. O. Owalude, J. Mater. Sci. 49 (2014) 5635.
[36] (a) X. L. Wang, J. Luan, H. Y. Lin, M. Le, G. C. Liu, Dalton Trans. 43 (2014) 8072; (b) H. Wu,
W. J. Sun, T. Shi, X. Z. Liao, W. J. Zhao, X. Yang, CrystEngComm 16 (2014) 11088.
[37] Y. Gong, J. Li, J. Qin, T. Wu, R. Cao, J. Li, Cryst. Growth Des. 11 (2011) 1662.
[38] (a) M. Xue, G. S. Zhu, Q. R. Fang, X. D. Guo, S. L. Qiu, Inorg. Chem. Commun. 9 (2006) 603;
(b) B. Valeur, Molecular Fluorescence Principles and Applications; WILEY-VCH: Weinheim
(2002).

Scheme 1. Structures of H2L and 4PBI ligands
Scheme 2. The coordination modes for ligand L (a,b) and 4PBI (c,d)

3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
H L
2
4PBI
200 300 400 500 600 700 800
Wavelength (nm)
Fig. 1. UV-Visible absorbance spectra of the free ligands H2L and 4PBI in DMF solution.
100
80
60
1
2
3
4
40
20
300
400
500
600
700
800
Wavelength (nm)
Fig. 2. UV–Visible diffuse reflectance spectra of complexes 1-4 in solid state.

(a)
(b)
(c)
(d)

Fig. 3. (a) A perspective view of the coordination geometry of the Ni (II) centre in 1. (b) A 1D chain
along the c axis in 1. (c) A 2D surpramolecular network formed by hydrogen bond interactions in 1. (d)
The packing diagram of 1 along the b axis
(a)
(b)

(c)
(d)
Fig. 4. (a) A perspective view of the coordination geometry of the Cd centre in 4 and the bis-nucleic
structure in 4. (b) A 2D layer along the crystallographic bc plane. (c) The packing diagram of 4. (d) The
topology structure of 4.
b
a
0
10
20
30
40
50
60
2
(o)
θ
Fig. 5. Powder X-ray diffraction (PXRD) plots for 1. (a) simulated; (b) experimental

b
a
0
10
20
30
40
50
60
o
2 ( )
θ
Fig. 6. PXRD plots for 2. (a) simulated; (b) experimental
b
a
0
10
20
30
40
50
60
o
2θ ( )
Fig. 7. PXRD plots for 3. (a) simulated; (b) experimental

b
a
0
10
20
30
40
50
60
o
2θ ( )
Fig. 8. PXRD plots for 4. (a) simulated; (b) experimental
100
80
60
40
20
200
400
600
800
Temperature ( )
oC
Fig. 9. TGA curve of 1.

100
80
60
40
200
400
600
800
Temperature ( )
OC
Fig. 10. TGA curve of 2.
100
80
60
40
20
200
400
600
800
Temperature ( )
OC
Fig. 11. TGA curve of 3.

100
80
60
40
20
200
400
600
800
Temperature ( )
OC
Fig. 12. TGA curve of 4.
100
4PBI
H L
80
60
40
20
0
2
4
400
500
600
700
Wavelength (nm)
Fig. 13. The solid-state emission spectra of complex 4, 4PBI and H2L ligand.

Table 1. The UV–Vis spectral data of H2L and 4PBI
Compound
L
4PBI
A
C (10-4) (M)
2.78
1.84
λmax(nm)
278
314
lgε
4.98
6.25
Solvent
DMF
DMF
0.27
3.31
Table 2. Crystal data and structure refinement data for 1-4
Compound reference
Chemical formula
Formula Mass
Crystal system
a/Å
b/Å
c/Å
α/°
β/°
1
2
3
4
C22H19N3NiO5 C22H19CoN3O5 C22H19CuN3O5 C22H17CdN3O4
464.11
Monoclinic
10.5053(7)
13.1794(7)
14.5680(8)
90.00
106.672(7)
90.00
1932.2(2)
100(2)
464.33
Monoclinic
10.4737(7)
13.1355(6)
14.6668(8)
90.00
106.884(7)
90.00
1930.84(19)
100(2)
468.94
Monoclinic
10.4805(9)
13.4316(8)
14.7788(13)
90.00
108.109(10)
90.00
1977.4(3)
100(2)
499.79
Triclinic
12.5721(5)
2.6827(4)
13.4256(6)
89.999(3)
74.554(4)
69.597(4)
1923.69(13)
100(2)
γ/°
Unit cell volume/Å3
Temperature/K
Space group
P21/n
P21/n
P21/n
P-1
No. of formula units per unit cell, Z
Radiation type
4
4
4
4
Mo Kα
1.047
17712
Mo Kα
0.931
17462
Mo Kα
1.146
19536
Mo Kα
1.171
18605
Absorption coefficient, µ/mm-1
No. of reflections measured
No. of independent reflections
Rint
4461
4474
4574
8887
0.0485
0.0486
0.1170
0.0584
0.1237
1.075
0.0486
0.0432
0.1154
0.0571
0.1285
1.023
0.0596
0.0526
0.1298
0.0776
0.1470
1.036
0.0430
0.0409
0.0843
0.0628
0.0978
1.040
Final R1 values (I>2σ(I))a
Final wR(F2) values (I>2σ(I))
Final R1 values (all data)
Final wR (F2) values (all data)b
Goodness of fit on F2
CCDC number
994678
994679
994680
994681
aR1=∑Fo-Fc/∑Fo.bwR2=[∑[w(Fo -Fc2)2]/∑[w(Fo ) ]]1/2.
2
2 2
Table 3. Selected bond lengths (Å) and angles (°) for complexes 1-4.
1
Ni(1)-O(1)
2.154(2)
2.057(2)
2.106(2)
89.17(8)
113.41(9)
98.30(8)
92.36(9)
168.50(8)
89.75(8)
93.60(9)
62.20(8)
Ni(1)-O(1W)
2.033(2)
Ni(1)-O(2)
Ni(1)-N(1)
2.058(2)
2.132(2)
62.85(8)
148.07(8)
88.43(8)
107.15(8)
176.17(9)
87.25(8)
92.67(8)
Ni(1)-O(3)a
Ni(1)-O(4)a
O(1)-Ni(1)-O(1W)
O(1)-Ni(1)-N(1)
O(1)-Ni(1)-O(4)a
O(1W)-Ni(1)-N(1)
O(1W)-Ni(1)-O(4)a
O(2)-Ni(1)-O(3)a
N(1)-Ni(1)-O(3)a
O(3)a-Ni(1)-O(4)a
2
O(1)-Ni(1)-O(2)
O(1)-Ni(1)-O(3)a
O(1W)-Ni(1)-O(2)
O(1W)-Ni(1)-O(3)a
O(2)-Ni(1)-N(1)
O(2)-Ni(1)-O(4)a
N(1)-Ni(1)-O(4)a
Co(1)-O(1)
2.1957(18)
2.0940(19)
2.1407(17)
89.68(7)
114.42(7)
145.81(7)
92.55(8)
Co(1)-O(1W)
2.045(2)
2.099(2)
2.1675(18)
61.41(7)
89.55(8)
97.99(7)
108.52(7)
87.28(7)
Co(1)-O(2)
Co(1)-N(1)
Co(1)-O(3)a
Co(1)-O(4)a
O(1)-Co(1)-O(1W)
O(1)-Co(1)-N(1)
O(1)-Co(1)-O(3)a
O(1W)-Co(1)-N(1)
O(1W)-Co(1)-O(4)a
O(1)-Co(1)-O(2)
O(1W)-Co(1)-O(2)
O(1)-Co(1)-O(4)a
O(1W)-Co(1)-O(3)a
O(2)-Co(1)-O(4)a
169.03(7)