Three new two-dimensional metal-organic coordination polymers derived from bis(pyridinecarboxamide)-1,4-benzene ligands and 1,3-benzenedicarboxylate: Syntheses and electrochemical property

Article abstract of DOI:10.1016/j.jorganchem.2010.12.009

Three new metal-organic coordination polymers, [Co(3-bpcb)(1,3-BDC)] ·H₂O (1), [Co(4-bpcb)(1,3-BDC)]·2H₂O (2) and [Cu(4-bpcb)(1,3-BDC)]₂·0.5(4-bpcb) (3), have been hydrothermally synthesized using N,N′-bis(3-pyridinecarboxamide)-1,4- benzene (3-bpcb) or N,N′-bis(4-pyridinecarboxamide)-1,4-benzene (4-bpcb) and 1,3-benzenedicarboxylate (1,3-H₂BDC) mixed ligands and characterized by elemental analyses, IR, TG, XRPD and single-crystal X-ray diffraction. Complexes 1-2 exhibit the similar two-dimensional (2D) network with different undulation degrees and dimensions, owing to different N positions from the 3-bpcb and 4-bpcb ligands. 1,3-BDC ligand in complexes 1 and 2 shows two coordination modes. The adjacent 2D layers for 1-2 are further linked by hydrogen bonding interactions to form a three-dimensional (3D) supramolecular network. Complex 3 possesses infinite 3-fold interpenetrating 2D network composed of three kinds of Cu-4-bpcb one-dimensional (1D) chains and 1,3-BDC ligands, in which 1,3-BDC only shows one coordination mode. The 2D network is further extended into 3D supramolecular framework by hydrogen bonding interactions. The non-coordinated 4-bpcb ligands existing in the 2D network connect with adjacent 2D layers through the hydrogen bonding interactions. In addition, the electrochemical behaviors and the fluorescence property of complexes 1-3 have been reported.

Full text of DOI:10.1016/j.jorganchem.2010.12.009

Journal of Organometallic Chemistry 696 (2011) 2313e2321
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Three new two-dimensional metal-organic coordination polymers derived from
bis(pyridinecarboxamide)-1,4-benzene ligands and 1,3-benzenedicarboxylate:
Syntheses and electrochemical property
*
Xiu-Li Wang , Bao Mu, Hong-Yan Lin, Guo-Cheng Liu
Faculty of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new metal-organic coordination polymers, [Co(3-bpcb)(1,3-BDC)]$H2O (1), [Co(4-bpcb)(1,3-
BDC)]$2H2O (2) and [Cu(4-bpcb)(1,3-BDC)]2$0.5(4-bpcb) (3), have been hydrothermally synthesized
using N,N0-bis(3-pyridinecarboxamide)-1,4-benzene (3-bpcb) or N,N0-bis(4-pyridinecarboxamide)-1,4-
benzene (4-bpcb) and 1,3-benzenedicarboxylate (1,3-H2BDC) mixed ligands and characterized by
elemental analyses, IR, TG, XRPD and single-crystal X-ray diffraction. Complexes 1e2 exhibit the similar
two-dimensional (2D) network with different undulation degrees and dimensions, owing to different N
positions from the 3-bpcb and 4-bpcb ligands. 1,3-BDC ligand in complexes 1 and 2 shows two coor-
dination modes. The adjacent 2D layers for 1e2 are further linked by hydrogen bonding interactions to
form a three-dimensional (3D) supramolecular network. Complex 3 possesses infinite 3-fold inter-
penetrating 2D network composed of three kinds of Cu-4-bpcb one-dimensional (1D) chains and 1,3-
BDC ligands, in which 1,3-BDC only shows one coordination mode. The 2D network is further extended
into 3D supramolecular framework by hydrogen bonding interactions. The non-coordinated 4-bpcb
ligands existing in the 2D network connect with adjacent 2D layers through the hydrogen bonding
interactions. In addition, the electrochemical behaviors and the fluorescence property of complexes 1e3
have been reported.
Received 14 September 2010
Received in revised form
30 November 2010
Accepted 7 December 2010
Keywords:
Hydrothermal synthesis
Metal-organic coordination polymer
Crystal structure
Electrochemistry
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
carboxyl groups. To the best of our knowledge, numerous excellent
metal-organic coordination polymers based on 1,3-H2BDC ligand
Remarkable progress has been achieved in the research of
metal-organic coordination polymers in recent years, not only
because of their fascinating structural diversities and framework
topologies, but also due to their potential applications in the fields
of catalysis, luminescence, gas adsorption, nonlinear optics (NLO)
and magnetic materials [1e4]. The rational design and construction
of these metal-organic coordination polymers mainly depend on
proper choice of the transition metal ions and the judicious selec-
tion of the multifunctional ligands [5]. It is known that aromatic
polycarboxylate ligands as a kind of multifunctional ligands have
attracted extensive attention, owing to their versatile coordination
modes and structural features [6,7]. In particular, 1,3-benzenedi-
carboxylate (1,3-H2BDC) is one of the most successful poly-
carboxylate ligands with the characteristic of their angular
bifunctionality [8] and appropriate connectivity [9e11] of two
have been reported [12e14].
On the other hand, the organic N-containing ligands, particu-
larly long multipyridyl organic bridging ligands, play an important
role in the formation of high-dimensional metal-organic coordi-
nation polymers [15,16]. As reported previously, the long and
symmetrical bipyridyl organic ligands N,N0-bis(4-pyridinecarbox-
amide)-1,4-benzene (4-bpcb) and N,N0-bis(3-pyridinecarbox-
amide)-1,4-benzene (3-bpcb) are efficient and versatile organic
ligands for the construction of abundant and novel polymer
architectures, and the structure with undulated layers have been
obtained [17,18]. The ligands 4-bpcb and 3-bpcb are chosen to
construct novel metal-organic coordination polymers in view of
their following characteristics: first, as the bifunctional ligands, the
antioxidation (stability) of 4-bpcb and 3-bpcb are improved;
second, the larger conjugated systems can be obtained through the
coordination of the lone pair from the bipyridyl N atoms with metal
atoms, which may increase flexibility of the electron cloud [19];
third, 4-bpcb and 3-bpcb with the excellent coordination ability
and their long spacers may tend to form high-dimensional
* Corresponding author. Tel.: þ86 416 3400158.
E-mail address: wangxiuli@bhu.edu.cn (X.-L. Wang).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.12.009

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X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
framework. However, the examples that employ the 4-bpcb or 3-
bpcb ligand and aromatic polycarboxylate ligands with rigid
backbones to generate high-dimensional framework are limited
[20]. Therefore, it is well worth studying the metal-organic coor-
dination polymers based on 4-bpcb or 3-bpcb and aromatic poly-
carboxylate ligands.
On the basis of the aforementioned points, we choose the long
and symmetrical bipyridyl organic ligands 4-bpcb and 3-bpcb
(Scheme 1), 1,3-H2BDC and metal salts (CoII and CuII) as reactants,
and fortunately obtain three new two-dimensional (2D) metal-
organic coordination polymers, namely [Co(3-bpcb)(1,3-BDC)]$
H2O (1), [Co(4-bpcb)(1,3-BDC)]$2H2O (2) and [Cu(4-bpcb)(1,3-
BDC)]2$0.5(4-bpcb) (3). Moreover, the electrochemical behaviors
and the fluorescence property of the three complexes are
investigated.
2. Results and discussion
Fig. 1. The coordination environment of CoII in complex 1.
2.1. Description of crystal structures
X-ray diffraction analysis reveals that complex 1 is an undulated
2D layer coordination polymer constructed from 3-bpcb and 1,3-
BDC ligands. The coordination environment of CoII atom is shown
in Fig. 1. The CoII atom is six-coordinated by two nitrogen atoms
belonging to two 3-bpcb ligands [the distances: Co(1)eN(1) 2.1459
(17) Å, Co(1)eN(2) 2.1548(17) Å], four oxygen atoms from three
1,3-BDC anions [the distances: Co(1)eO(1) 2.0370(15) Å, Co(1)eO
(2) 2.0479(17) Å, Co(1)eO(3) 2.1522(16) Å, Co(1)eO(14) 2.2831
(17) Å], showing a distorted octahedron geometry. The 3-bpcb
ligand assumes one coordination mode (Scheme 1a), namely,
bridging bidentate mode. The dihedral angle between the two
pyridyl rings of 3-bpcb ligand is 5.21ꢀ. The nitrogen atoms from the
two pyridyl rings of 3-bpcb ligands connect the adjacent CoII
atoms to build one-dimensional (1D) zigzag chain (Fig. S1). Two
carboxyls of 1,3-BDC anion show two different coordination
modes: one is bidentate bridging coordination, the other is che-
lating coordination (Scheme 1d). The 1,3-BDC ligands link CoII
atoms by two coordination modes to form another 1D ladder-like
chain, as shown in Fig. S2. The alternate connection of the two
types of 1D chain constructs a 2D sheet, as shown in Fig. 2 and
Fig. S3. Each metal CoII atom links two 3-bpcb and three 1,3-BDC
ligands, which can be defined as a 5-connected node. Each 1,3-BDC
links three metal CoII atoms, which suggest a 3-connected node.
The 3-bpcb ligating with two 5-connected CoII atoms serves as
a bridging ligand. Thus the 2D structure is best described as a (3,
5)-connected network, as shown in Fig. 2.
These 2D sheets are further extended to a three-dimensional
(3D) supramolecular network by hydrogen bonding interactions.
Some CeH/O hydrogen bonding interactions are observed in
Fig. 3. The intermolecular CeH/O hydrogen bonds are formed by
the carbon atoms C(3), C(16) and the oxygen atoms O(5), O(6) of
3-bpcb ligands, the carbon atom C(5) of 3-bpcb and the oxygen
atom O(14) of 1,3-BDC ligand. The observed distances are 3.120
(3) Å, 3.149(3) Å and 3.177(3) Å for C(3)eH(3A)/O(5), C(16)eH
(16A)/O(6) and C(5)eH(5A)/O(14), respectively.
Single crystal X-ray diffraction reveals that the structure of 2 is
also a 2D layer network, which is similar to that of complex 1 except
for small undulation. The building unit of complex 2 contains one
CoII atom, one organic ligand 4-bpcb, one 1,3-BDC ligand and two
lattice water molecules. As shown in Fig. 4, each center CoII atom
shows hex-coordination environment containing two nitrogen
atoms from two 4-bpcb ligands and four oxygen atoms from three
1,3-BDC ligands with Co(1)eN(3), Co(1)eN(4), Co(1)eO(1), Co(1)e
O(2) and Co(1)eO(3), Co(1)eO(4) bond distances of 2.1618(19) Å,
2.1664(19) Å, 2.0018(16) Å, 2.0256(15) Å, 2.1117(16) Å and 2.3006
(17) Å, respectively. The 4-bpcb ligand in complex 2 displays
bidentate coordination mode (Scheme 1b). Two nitrogen atoms of
4-bpcb bridge two CoII atoms to form a 1D chain (Fig. S4). The two
pyridyl rings of 4-bpcb ligand in complex 2 are not coplanar with
the dihedral angle of 16.73ꢀ. Two carboxyls of 1,3-BDC exhibit
different coordination modes which are similar to those in complex
1 (Scheme 1d). One carboxyl bridges CoII atoms (Co1 and Co1A), the
other carboxyl chelates CoII atoms, forming double track 1D ladder-
like chains, which is similar to complex 1. The 2D layer network is
constructed by the 4-bpcb and 1,3-BDC ligands (Fig. 5). The 2D
structure in complex 2 is also a (3, 5)-connected network due to the
same connected nodes of each metal CoII atom and each 1,3-BDC
ligand. Compared with complex 1, the 2D layer structure of
Scheme 1. Coordination modes of 3-bpcb, 4-bpcb and 1,3-BDC ligands in complexes
1e3.

X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
2315
Fig. 2. Stick and simplified representations of 2D coordination layer in complex 1.
BDC anions. That is, lattice water molecules O(1W) serve as H-
donor and interact with the oxygen atoms O(5), O(6) of 4-bpcb
ligands via hydrogen bonds [O(1W)eH(1W)/O(5) 2.829(4) Å, O
(1W)eH(2W)/O(6) 2.979(5) Å]. The N(1), N(2), C(12) from 4-bpcb
ligands and oxygen atoms O(1W), O(4) from lattice water mole-
cules and 1,3-BDC are involved in the formation of NeH/O and
CeH/O hydrogen bonds. The distances of N(1)eH(1)/O(1W), N
(2)eH(2)/O(4), and C(12)eH(12)/O(4) are 2.886(5) Å, 2.952(3) Å,
and 3.178(4) Å, respectively.
X-ray crystallography shows that complex 3 is 3-fold inter-
penetrating 2D layer coordination polymer constructed from CuII
atoms, 4-bpcb and 1,3-BDC ligands, and further extended into a 3D
supramolecular framework by hydrogen bonding interactions.
Meanwhile, the non-coordinated 4-bpcb ligands also exist in the
3D supramolecular framework. The coordination environment of
CuII atom is shown in Fig. 7, three crystallographically independent
CuII atoms [Cu(1), Cu(2) and Cu(3)] are all bridged by two nitrogen
atoms from two 4-bpcb ligands [Cu(1)eN(3) 2.007(3) Å, Cu(1)eN
(4) 2.015(3) Å, Cu(2)eN(7) 2.012(3) Å, Cu(2)eN(7A) 2.012(3) Å, Cu
(3)eN(1) 2.023(3) Å, Cu(3)eN(1A) 2.023(3) Å], chelated by four
oxygen atoms from two 1,3-BDC ligands, showing an octahedron
geometry.
Fig. 3. The 3D supramolecular network by hydrogen bonding interactions in complex 1.
complex 2 is almost flat without undulation, which is mainly due to
the difference of coordination sites between 4-bpcb and 3-bpcb
ligands.
Just as observed in Fig. 6, these neighboring layers are further
extended into a 3D supramolecular network through hydrogen
bonds among the lattice water molecules, 4-bpcb ligands, and 1,3-
In complex 3, three different 1D chains are built from three
crystallographically independent CuII atoms and 4-bpcb ligands.
These three kinds of 1D chains are of alternating emergence (eCu1-
4-bpcbe, eCu2e4-bpcbe, eCu1e4-bpcbe, eCu3e4-bpcbe)
(Fig. 8a). Although the ligand 4-bpcb shows only one coordination
Fig. 4. The coordination environment of CoII in complex 2.

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X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
Fig. 5. Stick and simplified representations of the 2D structure in complex 2.
Fig. 6. The 3D supramolecular network by hydrogen bonding interactions in complex 2.
Fig. 7. The coordination environment of CuII in complex 3.

X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
2317
Fig. 8. (a) The 1D chain structure based on CuII and 4-bpcb ligand in complex 3. (b) The 1D chain structure based on CuII and 1,3-BDC ligand in complex 3.
mode: bidentate (Scheme 1c), the dihedral angles of the two pyr-
idyl rings of 4-bpcb belonging to different 1D chain are distinct. In
the two chains of eCu2e4-bpcbe and eCu3e4-bpcbe, the two
pyridyl rings of 4-bpcb ligands are coplanar, whereas the two
pyridyl rings of 4-bpcb ligand in the eCu1e4-bpcbe chain are not
coplanar with the dihedral angle of 4.40ꢀ. In addition, the eCu2e4-
bpcbe and eCu3e4-bpcbe chains are parallel. Compared with
complexes 1 and 2, 1,3-BDC in complex 3 only shows one coordi-
nation mode, and two carboxyl groups of 1,3-BDC chelate two CuII
atoms, respectively (Scheme 1e). The 1,3-BDC ligands link CuII
atoms to form a 1D zigzag chain with Cu1/Cu2, Cu1/Cu3 distance
of 9.281 Å, 9.235 Å, respectively (Fig. 8b). Two types of 1D chains
comprised of CuII atoms and different ligands (4-bpcb or 1,3-BDC)
are linked by each other to form an undulated 2D layer network
(Fig. 9 and Fig. S5). Each metal CuII atom linked by two 4-bpcb
ligands and two 1,3-BDC ligands can imply a 4-connected node. The
4-bpcb ligating with two 4-connected CuII atoms serves as
a bridging ligand. Complex 3 adopts 3-fold interpenetrating 4-
connected 4462 topology (Fig. 10).
Fig. 11 shows that a 3D supramolecular framework is generated
via interlayer hydrogen bonding interactions. Non-coordinated
ligands 4-bpcb connect adjacent layers through the hydrogen
bonding interactions with N(9)eH(9A)/O(11) distance of 3.035
(6) Å. The nitrogen atoms N(2), N(5), N(6), and N(10) from 4-bpcb
ligands link the oxygen atoms O(8), O(5), O(2), and O(4) from 1,3-
BDC anions by way of NeH/O hydrogen bond, respectively. The
separations of N(2)eH(2A)/O(8), N(5)eH(5A)/O(5), N(6)eH
(6A)/O(2), and N(10)eH(10A)/O(4) are 3.179(5) Å, 2.870(5) Å,
2.981(5) Å, and 2.980(5) Å, respectively. In addition, the oxygen
atoms O(2), O(5), and O(8) from 1,3-BDC ligands and carbon atoms
C(30), C(40), and C(23) from the 4-bpcb ligands are involved in the
formation of CeH/O hydrogen bonds [distance: C(30)eH(30)/O
(2) 3.235(6) Å, C(40)eH(40)/O(5) 3.172(5) Å, C(23)eH(23)/O(8)
3.313(6) Å].
Fig. 9. Stick and simplified representations of the 2D structure in complex 3.

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X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
Fig. 10. Schematic perspective of 4462 3-fold interpenetrating network of complex 3.
Both complexes 1 and 2 are based on metal cobalt atoms, 1,3-
patterns are in good agreement with the corresponding simulated
ones, indicating the phase purities of the samples.
BDC anion and isomeric N,N0-bis(pyridinecarboxamide)-1,4-
benzene ligands with different N positions of the two pyridyl rings
(position 3 for 1 and 4 for 2), which result in not only the change of
the undulation degree of 2D layer network, but also the distinction
of dimensions of the 2D grids (16.201 ꢁ 7.560 Å for 1 and
19.997 ꢁ 4.195 Å for 2). For 2 and 3, CoII and CuII complexes based
on the same 4-bpcb and 1,3-BDC ligands show distinct 2D crystal
structures, which can be attributed to different valence shell elec-
tron configurations of different metal atoms [21]. Complex 2 shows
a 2D layer network comprised of a kind of Coe4-bpcb 1D chain and
1,3-BDC ligand with two coordinate modes, however, complex 3
exhibits 3-fold interpenetrating 2D network comprised of three
kinds of Cue4-bpcb 1D chains and 1,3-BDC ligands with only one
coordinate mode.
Thermogravimetric (TG) analyses are performed to estimate the
thermal stability of complexes 1e3 as shown in Figs. S12e14. The
TG curves of complexes 1e2 show two weight loss steps in
the temperature range of 30e750 ꢀC, while the TG curve of complex
3 exhibits only one weight loss stage between 20 ꢀC and 750 ꢀC. For
complexes 1e2, the first weight loss stages start at 80 ꢀC up to
120 ꢀC for 1, 75 ꢀC up to 145 ꢀC for 2, giving the weight loss of about
3.34% for 1, 6.43% for 2, corresponding to the loss of the lattice
water molecules (calcd. 3.22% for 1, 6.23% for 2). The second weight
loss occurring from 320 ꢀC to 485 ꢀC for 1, from 270 ꢀC to 470 ꢀC for
2, may suggest the decomposition of 3-bpcb or 4-bpcb and 1,3-BDC
molecules. The weight losses are about 83.32% for 1, 80.71% for 2, in
correspondence with the calculated value of 83.38% for 1, 80.79%
for 2. The remaining weights (13.34% for 1, 12.86% for 2) correspond
to the percentage (13.40% for 1, 12.98% for 2) of Co and O compo-
nents in CoO. In comparison with 1 and 2, the weight loss of
complex 3 begins at 275 ꢀC and completes by 450 ꢀC with only one
weight loss of 87.13% (calcd. 87.21%), indicating complete decom-
position of 4-bpcb and 1,3-BDC molecules to form CuO as a final
product. The percent of the residue is about 12.87%, which is in
accordance with the expected value 12.79%.
2.2. IR spectra of complexes 1e3
The main features of IR spectra for complexes 1e3 concern the
carboxylategroups of 1,3-BDC andthe 3-bpcb or4-bpcb ligand (Figs.
S6e8). Nostrong absorptionpeaks around 1700 cmꢂ1 for eCOOHare
observed, which implies that carboxyl groups of organic moieties in
the title complexes are completely deprotonated [22,23]. The strong
peaks at 1677, 1617, and 1384 cmꢂ1 for 1, 1646, 1613, and 1393 cmꢂ1
for 2, and 1665, 1614, and 1368 cmꢂ1 for 3 may be attributed to the
asymmetric and symmetric vibrations of carboxylate groups. The
presence of the expected characteristic bands at 1564, 1504, 1105,
and 712 cmꢂ1 for 1, 1567, 1496, 1093, and 735 cmꢂ1 for 2, and 1561,
1515, 1063, and 732 cmꢂ1 for 3, suggest the nCeN stretching of the
pyridyl ring of the 3-bpcb or 4-bpcb ligand.
2.4. Fluorescence property of complexes 1e3
The fluorescence property of complexes 1e3 and the free
ligands (3-bpcb and 4-bpcb) have been studied at room tempera-
ture in the solid state (Figs. S15 and S16). The free ligand 3-bpcb
exhibits the emission peak at 450 nm with the excitation at 310 nm.
For 1, upon excitation at 320 nm, it shows strong peak with the
emission at 436 nm, which is blue-shifted relative to that of the free
ligand 3-bpcb. The emission spectrum for the free 4-bpcb ligand
reveals a main peak at 470 nm with lex ¼ 310 nm. The fluorescence
peaks at about 452 nm and 469 nm are found in the emission
spectra of 2 and 3 when they are excited at 310 nm and 300 nm,
2.3. X-ray powder diffraction and thermogravimetric analyses of
title complexes
The X-ray powder diffraction (XRPD) patterns for complexes
1e3 are presented in Figs. S9e11, respectively. The as-synthesized
Fig. 11. The 3D supramolecular framework by hydrogen bonding interactions in complex 3.

X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
2319
Fig. 12. Cyclic voltammograms of 1-CPE (þ700 to þ350 mV), 2-CPE (þ800 to 0 mV), 3-CPE (þ800 to 0 mV) in 1 M H2SO4 solution for complexes 1e3. Scan rate: 100 mVsꢂ1
.
respectively. The blue-shifted emission occurs in the complex
2 while complex 3 has no significant change. It may be attributed to
the coordination environments of different metal atoms.
þ350mVandþ800to0mV,areversibleredoxpeakisobservedatthe
1-CPE and 2-CPE, respectively, which could be attributed to the redox
of CoII/CoI [27]. The mean peak potentials E1/2 ¼ (Epa þ Epc)/2 are
þ509 mV(100 mVsꢂ1)for 1-CPEandþ510mV(100mVsꢂ1)for2-CPE.
In the potential range of þ800 to 0 mV, a reversible redox peak
attributed to the redox of CuII/CuI is observed at the 3-CPE [28e30],
the mean peak potential E1/2 ¼ (Epa þ Epc)/2 are þ494 mV
(100 mVsꢂ1) for 3-CPE.
2.5. Electrochemical behaviors of complexes 1e3 modified carbon
paste electrode (1-CPE, 2-CPE, and 3-CPE)
Complexes 1e3 are all insoluble in water and common organic
solvents. Thus, the complexes 1e3 bulk-modified carbon paste elec-
trodes (1-CPE, 2-CPE, 3-CPE) are fabricated as the working electrodes
[24,25], which become the optimal choice to study the electro-
chemical property of these complexes [26]. The cyclic voltammo-
grams of the 1-CPE to 3-CPE in 1 M H2SO4 solution are recorded in
Fig. 12. It can be seen clearly that in the potential range of þ700 to
Scan rates effect on the electrochemical behavior of the 3-CPE is
investigated in the potential range of þ800 to 0 mV in 1 M H2SO4
solution. As shown in Fig. 13, with the scan rates increasing from 40
to 300 mVsꢂ1, the peak potentials changed gradually: the cathodic
peak potentials gradually shift to the negative direction and the
corresponding anodic peak potentials shifted to the positive
direction. The inset of Fig. 13 shows that the peak currents are
Fig. 13. Cyclic voltammograms of the 3-CPE in 1 M H2SO4 solution at different scan
rates (from inner to outer: 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300 mVsꢂ1). The
inset shows the plots of the anodic and cathodic peak currents against scan rates.
Fig. 14. Cyclic voltammograms of the bare CPE in 1 M H2SO4 solution containing
1.0 mmol/L KNO2 (a), 3-CPE in 1 M H2SO4 solution containing (bwd): 0.0, 2.0 and
4.0 mmol/L KNO2. Scan rate: 120 mVsꢂ1
.

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X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
Table 1
analyses (C, H, N) were performed on a PerkineElmer 240C element
analyzer. FT-IR spectra (KBr pellets) were obtained on a Magna FT-
IR 560 spectrometer. Thermogravimetric data for the complexes
1e3 were carried out on a Pyris Diamond thermal analyzer. Fluo-
rescence spectra were recorded at room temperature on a Hitachi
F-4500 fluorescence/phosphorescence spectrophotometer. X-ray
powder diffraction investigations were carried out on a Bruker AXS
Crystal data and structure refinements for complexes 1e3.
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
a(Å)
C26H20CoN4O7 C26H22CoN4O8 C61H43Cu2N10O13
559.36
Triclinic
P1
577.39
Triclinic
P1
1251.15
Triclinic
P1
8.601(5)
10.064(5)
13.771(5)
98.444(5)
98.080(5)
99.451(5)
1146.4(10)
2
10.067(1)
10.4787(11)
14.271(2)
106.793(2)
104.070(2)
104.935(1)
1307.9(3)
2
12.400(2)
13.722(2)
17.556(3)
77.925(2)
80.552(2)
73.759(2)
2786.7(8)
2
D8-Advanced diffractometer with Cu-K
a
(l
¼ 1.5406 Å) radiation in
b(Å)
c(Å)
the 2
q
range of 5e50ꢀ. A CHI 440 electrochemical workstation
a
(ꢀ)
(ꢀ)
connected to a Digital-586 personal computer was used for control
of the electrochemical measurements and for data collection. A
conventional three-electrode system was used with an SCE as
reference electrode, a platinum wire as auxiliary electrode and the
modified electrode as the working electrode, respectively.
b
g
(ꢀ)
V(Å3)
Z
Dcalc(g cmꢂ3
)
1.609
0.807
1.461
0.713
1.491
0.840
m
(mmꢂ1
)
F(000)
566
590
0.814/0.892
6637
4521
0.0164
0.994
0.0370
0.1157
0.470
1282
4.2. Preparation
Minimum/maximum trans 0.856/0.886
0.777/0.860
28,420
13,544
0.0944
0.974
0.0660
0.0714
0.580
Total reflections
Unique reflections
Rint
GOF
R1(I > 2
9077
4018
4.2.1. Synthesis of [Co(3-bpcb)(1,3-BDC)]$H2O (1)
0.0126
1.049
0.0286
0.0805
0.701
ꢂ0.357
P
A mixture of CoCl2$2H2O (0.035 g, 0.20 mmol), 3-bpcb (0.032 g,
0.10 mmol), 1,3-H2BDC (0.033 g, 0.20 mmol), H2O (12 mL) and
NaOH (0.017 g, 0.43 mmol) was stirred for 30 min at room
temperature and then transferred to a 25 mL Teflon-lined autoclave
and kept at 120 ꢀC for 4 days. After slow cooling to room temper-
ature, orange red block crystals of 1 were obtained (yield: ca. 34%
based on Co). Anal. Calc. for C26H20CoN4O7: C 55.78, H 3.58, N 10.01.
Found: C 55.81, H 3.54, N 10.03%. IR (KBr, cmꢂ1): 3407(w), 3261(w),
3148(w), 3081(w), 2342(m), 1677(s), 1617(s), 1564(s), 1504(s), 1471
(s), 1384(s), 1311(m), 1278(w), 1218(m), 1105(m), 1051(w), 1019(w),
972(w), 912(w), 872(w), 826(m), 712(s), 633(m), 565(w).
s
(I))
wR2(I > 2
s(I))
Drmax(e Åꢂ3
)
)
Drmin(e Åꢂ3
ꢂ0.398
ꢂ0.489
P
P
P
R1
¼
jFoj ꢂ jFcj/ jFoj, wR2
¼
[w(Fo2 ꢂ Fc2)2]/ [w(Fo2)2]1/2
.
proportional to the scan rates up to 300 mVsꢂ1, suggesting that the
redox process for 3-CPE is surface-controlled.
Fig. 14 shows cyclic voltammograms for the electrocatalytic
reduction of nitrite at a bare CPE and the 3-CPE in 1 M H2SO4
solution. There is no redox peak at the bare CPE at the presence of
nitrite in the potential range of þ800 to 0 mV. With the addition of
nitrite, the reduction peak currents increase markedly while the
corresponding oxidation peak currents decrease markedly at the 3-
CPE. The results indicate that 3-CPE possesses good electrocatalytic
activity toward the reduction of nitrite.
4.2.2. Synthesis of [Co(4-bpcb)(1,3-BDC)]$2H2O (2)
The synthesis method of 2 is similar to that of 1 except for ligand
4-bpcb as the substitute of 3-bpcb, and the different amount of
NaOH (0.019 g, 0.47 mmol) was added to adjust the systematic pH
(yield: ca. 31% based on Co). Anal. Calc. for C26H22CoN4O8: C 54.04,
H 3.81, N 9.70. Found: C 54.08, H 3.77, N 9.67%. IR (KBr, cmꢂ1): 3446
(w), 3316(w), 3063(w), 2347(w), 2316(w), 1646(s), 1613(s), 1567(s),
1496(s), 1451(m), 1393(s), 1314(s), 1276(m), 1217(m), 1171(w), 1093
(m), 1054(m), 1003(m), 917(w), 904(w), 840(s), 735(s), 671(s), 618
(w).
3. Conclusions
In summary, we have successfully synthesized three new metal-
organic coordination polymers, [Co(3-bpcb)(1,3-BDC)]$H2O (1), [Co
(4-bpcb)(1,3-BDC)]$2H2O (2) and [Cu(4-bpcb)(1,3-BDC)]2$0.5(4-
bpcb) (3), which based on mixed 3-bpcb or 4-bpcb and 1,3-BDC
ligands. Complexes 1e3 all exhibit 2D layer structures and are ulti-
mately extended into 3D supramolecular framework by hydrogen
bonding interactions. The different N positions of the two pyridyl
rings have influence on dimensions and undulation degree of 2D
networks for complexes 1e2. The selection of different metal atoms
plays an important in changing the structures of complexes 2e3.
Complex 2 contains a kind of Co-4-bpcb 1Dchain and1,3-BDC ligand,
while complex 3 with 3-fold interpenetrating network consists of
three kinds of Cu-4-bpcb 1D chains and 1,3-BDC ligands. In addition,
the non-coordinated 4-bpcb ligands in complex 3 consolidate the 3D
supramolecular framework by hydrogen bonding interactions.
Electrochemical and fluorescent properties of complexes 1e3 reveal
that the three complexes may possess potential applications in the
field of electrochemistry and fluorescence.
4.2.3. Synthesis of [Cu(4-bpcb)(1,3-BDC)]2$0.5(4-bpcb) (3)
A mixture of CuCl2$2H2O (0.045 g, 0.26 mmol), 4-bpcb (0.060 g,
0.19 mmol), 1,3-H2BDC (0.033 g, 0.20 mmol), H2O (12 mL) and
NaOH (0.018 g, 0.45 mmol) was stirred for 30 min at room
temperature and then transferred to a 25 mL Teflon-lined autoclave
and kept at 120 ꢀC for 4 days. After slow cooling to room temper-
ature, purple block crystals of 3 were obtained (yield: ca. 27% based
on Cu). Anal. Calc. for C61H43Cu2N10O13: C 58.51, H 3.44, N 11.19.
Found: C 58.47, H 3.46, N 11.22%. IR (KBr, cmꢂ1): 3506(w), 3377(w),
3313(w), 3145(w), 2372(w), 1665(s), 1614(s), 1561(s), 1515(s), 1484
(w), 1400(s), 1368(s), 1315(s), 1271(m), 1225(m), 1172(w), 1114(w),
1063(m), 953(w), 913(m), 836(m), 732(m), 674(m).
4.2.4. Preparation of complexes 1e3 bulk-modified carbon paste
electrode
The 1-CPE was fabricated as follows: 0.5 g graphite powder and
0.035 g complex 1 were mixed and ground together by agate
mortar and pestle for about half an hour, and then 0.21 mL paraffin
oil was added and stirred with a glass rod. The homogenized
mixture was used to pack 3 mm inner diameter glass tubes to
a length of 0.8 cm. The electrical contact was established with the
copper stick, and the surface of the 1-CPE was polished by weighing
paper. In a similar manner, 2-, and 3-CPEs were made with
complexes 2e3.
4. Experimental
4.1. Materials and measurements
All chemicals were purchased from commercial sources and
used without further purification. The ligands 4-bpcb and 3-bpcb
were synthesized by the literature methods [31]. Elemental

X.-L. Wang et al. / Journal of Organometallic Chemistry 696 (2011) 2313e2321
2321
[3] J.A. Rood, W.C. Boggess, B.C. Noll, K.W. Henderson, J. Am. Chem. Soc. 129
(2007) 13675e13682.
4.3. X-ray crystallography study
[4] C.Y. Li, C.S. Liu, J.R. Li, X.H. Bu, Cryst. Growth Des. 7 (2007) 286e295.
[5] X.Q. Liang, X.H. Zhou, C. Chen, H.P. Xiao, Y.Z. Li, J.L. Zuo, X.Z. You, Cryst. Growth
Des 9 (2009) 1041e1053.
[6] R. Sun, Y.Z. Li, J.F. Bai, Y. Pan, Cryst. Growth Des 7 (2007) 890e894.
[7] S. Wang, J.F. Bai, H. Xing, Y.Z. Li, Y. Song, Y. Pan, M.F. Scheer, X.Z. You, Cryst.
Growth Des 7 (2007) 747e754.
[8] J.J. Perry, G.J. McManus, M.J. Zaworotko, Chem. Commun. (2004) 2534e2535.
[9] S.Y. Yang, L.S. Long, R.B. Huang, L.S. Zheng, Chem. Commun. (2002) 472e473.
[10] B. Moulton, H. Abourahma, M.W. Bradner, J. Lu, G.J. McManus, M.J. Zaworotko,
Chem. Commun. (2003) 1342e1343.
[11] H. Abourahma, G.J. McManus, B. Moulton, R.D.B. Walsh, M.J. Zaworotko,
Macromol. Symp. 196 (2003) 213e227.
[12] Y.F. Zhou, Y.J. Zhao, D.F. Sun, J.B. Weng, R. Cao, M.C. Hong, Polyhedron 22
(2003) 1231e1235.
[13] Y.F. Zhou, F.L. Jiang, D.Q. Yuan, B.L. Wu, R.H. Wang, Z.Z. Lin, M.C. Hong, Angew.
Chem. Int. Ed. 43 (2004) 5665e5668.
[14] Y.F. Zhou, D.Q. Yuan, F.L. Jiang, Y.Q. Xu, M.C. Hong, J. Mol. Struct. 796 (2006)
203e209.
X-ray diffraction analyses data for complexes 1e3 were collected
with a Bruker APEX diffractometer with Mo K
a (graphite mono-
chromator,
l
¼ 0.71073 Å). The structure was solved by direct
methods using the SHELXS program of the SHELXTL package and
refined by full-matrix least-squares methods with SHELXL [32,33].
For the complexes, all nonhydrogen atoms except the oxygen atom
(O2W) of water molecule in complex 2 were refined anisotropically,
the hydrogen atoms of the ligands 3-bpcb and 4-bpcb were gener-
ated theoretically onto the specific atoms and refined isotropically
with fixed thermal factors. The crystal parameters, data collection,
and refinement results for complexes 1e3 are summarized in Table
1. Selected bond distances and bond angles are listed in Table S1.
Hydrogen bonding geometries are summarized in Table S2.
[15] L.K. Sposato, R.L. LaDuca, Polyhedron 29 (2010) 2239e2249.
[16] D.P. Martin, R.M. Supkowski, R.L. LaDuca, Cryst. Growth Des
8 (2008)
Acknowledgments
3518e3520.
[17] J. Pansanel, A. Jouaiti, S. Ferlay, M.W. Hosseini, J.M. Planeix, N. Kyritsakas, New
J. Chem. 30 (2006) 71e76.
[18] J. Pansanel, A. Jouaiti, S. Ferlay, M.W. Hosseini, J.M. Planeix, N. Kyritsakas, New
J. Chem. 30 (2006) 683e688.
[19] Y.Y. Niu, Y.L. Song, J. Wu, H.W. Hou, Y. Zhu, X. Wang, Inorg. Chem. Commun. 7
(2004) 471e474.
Financial supports of this research by the NCET-09-0853,
National Natural Science Foundation of China (No. 20871022) and
Foundation of Liaoning Province (No.2009R03 and 2009A028) are
greatly acknowledged.
[20] X.L. Wang, H.Y. Lin, B. Mu, A.X. Tian, G.C. Liu, Dalton Trans. 39 (2010)
6187e6189.
Appendix A. Supplementary data
[21] L. Carlucci, G. Ciani, D.M. Proserpio, S. Rizzato, CrystEngComm
190e199.
5 (2003)
[22] X.J. Gu, D.F. Xue, Cryst. Growth Des 6 (2006) 2551e2557.
[23] L.J. Bellamy, The Infrared Spectra of Complex Molecules. Wiley, New York,
1958.
[24] T. Kuwana, W.G. French, Anal. Chem. 36 (1964) 241e242.
[25] F.A. Schultz, T. Kuwana, J. Electroanal. Chem. 10 (1965) 95e103.
[26] A.X. Tian, J. Ying, J. Peng, J.Q. Sha, H.J. Pang, P.P. Zhang, Y. Chen, M. Zhu,
Z.M. Su, Cryst. Growth Des 8 (2008) 3717e3724.
[27] T.V. Mitkina, N.F. Zakharchuk, D.Y. Naumov, O.A. Gerasko, D. Fenske,
V.P. Fedin, Inorg. Chem. 47 (2008) 6748e6755.
CCDC 787707, 786146 and 786147 contain the supplementary
crystallographic data for the compounds 1e3. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Appendix. Supplementary data
[28] G.G. Gao, L. Xu, W.J. Wang, W.J. An, Y.F. Qiu, Z.Q. Wang, E.B. Wang, J. Phys.
Chem. B. 109 (2005) 8948e8953.
[29] A. Salimi, V. Alizadeh, H. Hadadzadeh, Electroanalysis 16 (2004) 1984e1991.
[30] B.K. Santra, P.A.N. Reddy, G. Neelakanta, S. Mahadevan, M. Nethajia,
A.R. Chakravartya, J. Inorg. Biochem. 89 (2002) 191e196.
Crystallographic data in CIF, IR spectra, TG curves and the tables
with the selected bond lengths and bond angles can be found, in the
online version at doi:10.1016/j.jorganchem.2010.12.009.
[31] M. Sarkar, K. Biradha, Cryst. Growth Des 6 (2006) 202e208.
[32] G.M. Sheldrick, SHELXS-97, Program for the Solution of Crystal Structure.
University of Göttingen, Göttingen, Germany, 1997.
References
[33] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structure.
University of Göttingen, Göttingen, Germany, 1997.
[1] V.V. Adrabinska, Coord. Chem. Rev. 251 (2007) 1987e2016.
[2] S.L. James, Chem. Soc. Rev. 32 (2003) 276e288.