Effect of flexible bis-pyridyl-bis-amide ligands and dicarboxylates on the assembly and properties of multifunctional Cu(ii) metal-organic coordination polymers

Article abstract of DOI:10.1039/c3dt50202c

A series of multifunctional Cu(ii) metal-organic coordination polymers based on three flexible bis-pyridyl-bis-amide ligands and four aromatic dicarboxylates, namely [Cu(3-dpye)(3-NPA)(H₂O)]·3H ₂O (1), [Cu(3-dpye)_0.5(5-AIP)(H₂O)] (2), [Cu(3-dpye)(1,3-BDC)]·3H₂O (3), [Cu₃(3-dpye)(1,2- BDC)₂(μ₂-OH)₂] (4), [Cu₃(3-dpyb) (1,2-BDC)₂(μ₂-OH)₂] (5), [Cu(3-dpyh) _0.5(1,2-BDC)]·H₂O (6), [Cu(3-dpyh) _0.5(5-AIP)(H₂O)] (7) [3-dpye = N,N′-bis(3- pyridinecarboxamide)-1,2-ethane, 3-dpyb = N,N′-bis(3-pyridinecarboxamide)- 1,4-butane, 3-dpyh = N,N′-bis(3-pyridinecarboxamide)-1,6-hexane, 3-H ₂NPA = 3-nitrophthalic acid, 5-H₂AIP = 5-aminoisophthalic acid, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid, 1,2-H₂BDC = 1,2-benzenedicarboxylic acid], have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, PXRD, TG and single crystal X-ray diffraction. X-ray analyses reveal that the seven Cu(ii) complexes show three kinds of different 2D layer structures (for complexes 1, 2, 3, 6 and 7) and a 3D coordination framework (for complexes 4 and 5), exhibiting the (4⁴·6²) topology for 1, (4²· 6³·8)(4²·6) topology for isostructural complexes 2 and 7, (4²·6⁷·8)(4 ²·6) topology for complex 3, (3·4·5) ₂(3·4²·5·8⁶) ₂(3²·8·9²·10)(4 ²·8²·10²) topology for isostructural complexes 4 and 5, and the (4²·6 ³·8)(4²·6) topology for complex 6, respectively. In complexes 1-7, the bis-pyridyl-bis-amide ligands adopt a μ₂-bridging mode in 1, 2, 3, 6 and 7 (via ligation of two pyridyl nitrogen atoms) and a μ₄-bridging coordination mode in 4 and 5 (via ligation of two pyridyl nitrogen atoms and two carbonyl oxygen atoms), which play an important role in determining the dimensionality of the title complexes. The aromatic dicarboxylates serve as a linker (for 1) and three-connected nodes (for 2-7) to bridge the adjacent Cu(ii) ions, respectively, leading to the formation of various topological structures, which indicate both the substitute group and position of carboxyl group of the dicarboxylates play significant roles in the construction of the title complexes. The fluorescent, electrochemical and photocatalytic properties of complexes 1-7 have also been investigated.

Full text of DOI:10.1039/c3dt50202c

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Effect of flexible bis-pyridyl-bis-amide ligands and
dicarboxylates on the assembly and properties of
multifunctional Cu(II) metal–organic coordination
polymers†
Cite this: Dalton Trans., 2013, 42, 8375
Xiuli Wang,* Jian Luan, Hongyan Lin, Qilin Lu, Chuang Xu and Guocheng Liu
A series of multifunctional Cu(II) metal–organic coordination polymers based on three flexible bis-pyridyl-
bis-amide ligands and four aromatic dicarboxylates, namely [Cu(3-dpye)(3-NPA)(H2O)]·3H2O (1), [Cu(3-
dpye)0.5(5-AIP)(H2O)] (2), [Cu(3-dpye)(1,3-BDC)]·3H2O (3), [Cu3(3-dpye)(1,2-BDC)2(μ2-OH)2] (4), [Cu3(3-
dpyb)(1,2-BDC)2(μ2-OH)2] (5), [Cu(3-dpyh)0.5(1,2-BDC)]·H2O (6), [Cu(3-dpyh)0.5(5-AIP)(H2O)] (7) [3-dpye =
N,N’-bis(3-pyridinecarboxamide)-1,2-ethane, 3-dpyb
=
N,N’-bis(3-pyridinecarboxamide)-1,4-butane,
3-dpyh = N,N’-bis(3-pyridinecarboxamide)-1,6-hexane, 3-H2NPA = 3-nitrophthalic acid, 5-H2AIP = 5-amino-
isophthalic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 1,2-H2BDC = 1,2-benzenedicarboxylic acid],
have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, PXRD, TG
and single crystal X-ray diffraction. X-ray analyses reveal that the seven Cu(II) complexes show three kinds
of different 2D layer structures (for complexes 1, 2, 3, 6 and 7) and a 3D coordination framework (for
complexes 4 and 5), exhibiting the (44·62) topology for 1, (42·63·8)(42·6) topology for isostructural com-
plexes 2 and 7, (42·67·8)(42·6) topology for complex 3, (3·4·5)2(3·42·5·86)2(32·8·92·10)(42·82·102) topology
for isostructural complexes 4 and 5, and the (42·63·8)(42·6) topology for complex 6, respectively. In com-
plexes 1–7, the bis-pyridyl-bis-amide ligands adopt a μ2-bridging mode in 1, 2, 3, 6 and 7 (via ligation of
two pyridyl nitrogen atoms) and a μ4-bridging coordination mode in 4 and 5 (via ligation of two pyridyl
nitrogen atoms and two carbonyl oxygen atoms), which play an important role in determining the
dimensionality of the title complexes. The aromatic dicarboxylates serve as a linker (for 1) and three-con-
nected nodes (for 2–7) to bridge the adjacent Cu(II) ions, respectively, leading to the formation of various
topological structures, which indicate both the substitute group and position of carboxyl group of the
dicarboxylates play significant roles in the construction of the title complexes. The fluorescent, electro-
chemical and photocatalytic properties of complexes 1–7 have also been investigated.
Received 20th January 2013,
Accepted 18th March 2013
DOI: 10.1039/c3dt50202c
www.rsc.org/dalton
structures, such as organic ligands,7 systematic pH value,8
Introduction
template effect9 and reaction temperature,10 may play impor-
Metal–organic coordination polymers have been given more tant roles in the process of the self-assembly. Therefore, sig-
research attention recently, not only for their intriguing variety nificant interest has arisen in the structural tuning of
of architectures and topologies,1 but also for their potential coordination polymers through rational design and selection
applications as multifunctional materials with the properties of organic building blocks, such as O-donor ligands and
of luminescence,2 electrochemistry,3 magnetism,4 catalysis,5 N-donor ligands. The dicarboxylates as multidentate O-donor
and gas storage.6 Although a large amount of such polymers ligands possess the following characteristics: firstly, the dicar-
have been obtained by the self-assembly of metal ions and boxylate ligands possess multiple potential coordination sites
organic ligands, the influencing factors of the ultimate involving two –COOH groups and substitute group, which will
be more conducive to coordinate with metal centers in the
metal–organic coordination polymers and can be considered
Department of Chemistry, Bohai University, Jinzhou, 121000, P. R. China.
as connecting nodes or linkers to construct specific structures
and topologies; secondly, they could serve as hydrogen
E-mail: wangxiuli@bhu.edu.cn; Fax: +86-416-3400158; Tel: +86-416-3400158
†Electronic supplementary information (ESI) available: IR Spectra, TG, and
bonding donors or acceptors to build high-dimensional supra-
additional figures. CCDC 889598, 889600, 889599, 889597, 891322, 891323 and
molecular networks.11 Based on the above two points, in the
909348. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c3dt50202c
last decades, the dicarboxylates are usually used as the
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8375

View Article Online
Paper
Dalton Transactions
auxiliary ligands combining with various N-donor ligands to
construct novel architectures.12
In the recent years, the combination of bis-pyridyl-bis-
amide ligands and carboxylate ligands can be regarded as an
effective strategy to prepare attractive metal–organic coordi-
nation frameworks with different dimensionalities, which
attracted great interest from researchers.13 Several groups have
reported the assembly of rigid or semi-rigid bis-pyridyl-bis-
amide ligands with metal salts and some inorganic anions or
various carboxylates.14 Our group also have been focusing our
attention on the utilization of rigid or semi-rigid bis-pyridyl-
bis-amide ligands combining with polycarboxylates in the con-
struction of coordination polymers with diverse structures and
multifunctional complexes.15 However, reports on the coordi-
nation complexes of flexible bis-pyridyl-bis-amide ligands are
still limited.16 To the best of our knowledge, only quite a few
examples based on the flexible N,N′-bis(3-pyridinecarboxa-
mide)-1,2-ethane (3-dpye) with –(CH2)2– backbone or N,N′-bis-
(3-pyridinecarboxamide)-1,4-butane (3-dpyb) with backbone of
–(CH2)4– and polycarboxylates mixed ligands have been
reported by us and others.17
Scheme 2 The outline of complexes 1–7.
topological analyses of these polymers have been represented
and discussed. In addition, the fluorescent, electrochemical,
and photocatalytic properties of 1–7 have also been investi-
gated below in detail.
In order to further explore the effect of flexible bis-pyridyl-
bis-amide ligands with different spacer length and various
coordination modes, as well as the dicarboxylates with
different substitute group or position of carboxyl groups, on
Results and discussion
Structural description
Crystal structure description of [Cu(3-dpye)(3-NPA)
the assembly and structures of multifunctional Cu(II) metal– (H2O)]·3H2O (1). X-ray crystallography reveals that complex 1
organic coordination polymers, in this work, three flexible bis- crystallizes in the monoclinic system with space group P21/c.
pyridyl-bis-amide ligands 3-dpye, 3-dpyb, N,N′-bis(3-pyridine- There is one Cu(II) ion, one 3-dpye ligand, one 3-NPA anion,
carboxamide)-1,6-hexane (3-dpyh) (Scheme 1) have been one coordinated water molecule, and three lattice water mole-
designed and used as the main ligands, four aromatic dicar- cules in the asymmetric unit of complex 1. The crystallographi-
boxylate ligands, 3-nitrophthalic acid (3-H2NPA), 5-amino- cally independent Cu(II) ion showing a distorted pyramid
isophthalic acid (5-H2AIP), 1,3-benzenedicarboxylic acid (1,3- geometry {CuN2O3}, is coordinated by two nitrogen atoms
H2BDC), 1,2-benzenedicarboxylic acid (1,2-H2BDC) have been from two 3-dpye ligands [Cu1–N2 = 2.014(2) Å, Cu1–N4 = 2.027(2)
introduced to the Cu(II)/flexible bis-pyridyl-bis-amide systems. Å], three oxygen atoms from two 3-NPA anions and one
As a result, seven coordination polymers have been obtained coordinated water molecule [Cu1–O1 = 1.9751(18), Cu1–O5 =
under hydrothermal conditions (Scheme 2), namely [Cu(3-dpye)- 1.9768(19), Cu1–O1W = 2.4513(25) Å] (Fig. 1a). In complex 1,
(3-NPA)(H2O)]·3H2O (1), [Cu(3-dpye)0.5(5-AIP)(H2O)] (2), The ligand 3-dpye adopts a μ2-bridging coordination mode
[Cu(3-dpye)(1,3-BDC)]·3H2O (3), [Cu3(3-dpye)(1,2-BDC)2(μ2- connecting the neighbouring Cu(II) ions to form a meso-helical
OH)2] (4), [Cu3(3-dpyb)(1,2-BDC)2(μ2-OH)2] (5), [Cu(3- [Cu-3-dpye]n chain (Fig. 1b). Furthermore, the adjacent [Cu-3-
dpyh)0.5(1,2-BDC)]·H2O (6), [Cu(3-dpyh)0.5(5-AIP)(H2O)] (7). To dpye]n chains are linked by the 3-NPA anions with a bis(mono-
our knowledge, metal–organic coordination complexes con- dentate) coordination mode to form a 2D network (Fig. 1d), in
structed by the 3-dpyh and organic carboxylates mixed ligands which the 3-NPA also connect Cu(II) ions through its two car-
have not been found up to now. The crystal structures and boxyl oxygen atoms in the opposite direction to build 1D
[Cu-3-NPA] left- and right-helix chains (Fig. 1c and Scheme S1a†).
For perspicuous representation, it is necessary to simplify the
building blocks from the 2D metal–organic network. Each
Cu(II) is surrounded by two 3-dpye ligands and two 3-NPA
ligands, which can be defined as a 4-connected node. The
3-dpye and 3-NPA serve as a simple linear linker and a ‘V’-like
linker, respectively. Topological analysis reveals that the 2D
layer of complex 1 represents a 4-connected network with
(44·62) topology (Fig. 1e), in which two kinds of hexagon
[Cu4(3-dpye)2(3-NPA)2] loops with dimensions of ca. 13.79 ×
17.58 Å2 (loop A) and 15.33 × 16.26 Å2 (loop B) can be found.
Additionally, the 2D layers are linked by the O–H⋯O hydrogen
Scheme 1 The structures of ligands 3-dpye, 3-dpyb and 3-dpyh.
8376 | Dalton Trans., 2013, 42, 8375–8386
bonding interactions between O1W of the coordinated water
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
molecule. Each Cu(II) ion is five-coordinated by two nitrogen
atoms from the amino group of 5-AIP ligand [Cu1–N1 = 2.056(3)
Å] and pyridyl group of the 3-dpye ligand [Cu1–N2 = 2.027(3) Å],
one oxygen atom from the coordinated water molecule
[Cu1–O1W = 2.327(3) Å], and two carboxyl oxygen atoms [Cu1–
O1 = 1.944(2) Å, Cu1–O4 = 2.001(2) Å] belonging to two
different 5-AIP anions to furnish a distorted pyramid geometry
(Fig. 2a for 2 and Fig. S8† for 7). The nitrogen atoms from
3-dpye ligand and 5-AIP anion occupy the apexes and the other
three coordinated oxygen atoms are located in the equatorial
plane. As depicted in Fig. 2b and Scheme S1b, S1g,† each 5-AIP
anions adopting a tri(monodentate) coordination mode links
three Cu(II) ions to construct a 1D [Cu-5-AIP] ladder-like struc-
ture. Such adjacent [Cu-5-AIP] ladders are connected by the
μ2-bridging 3-dpye ligands to form a 2D layer motif, which is
shown in Fig. 2c. Furthermore, each Cu(II) ion can be con-
sidered as a four-connected node and 5-AIP can be regarded as
a three-connected node, and the 3-dpye can be regarded as a
linear linker, thus the resultant structure of 2 is a binodal 3,4-
connected 2D network with the point symbol of (42·63·8)(42·6),
in which the large hexagonal [Cu4(3-dpye)2(5-AIP)2] loop is
approximately 13.70 × 20.84 Å2 in complex 2 (15.57 × 26.46 Å2
in complex 7) (Fig. 2d for 2 and Fig. S9† for 7). The 2D layers
are further connected by hydrogen bonding interactions to
form the 3D supramolecular structure, as shown in Fig. S2.†
The N–H⋯O hydrogen bonding interaction is formed between
Fig. 1 (a) ORTEP drawing of complex 1 with thermal ellipsoids at 50% prob-
ability (the H atoms and lattice water molecules have been omitted for clarity.);
(b) the meso-helical [Cu-3-dpye] chain along the a-axis; (c) the [Cu-3-NPA] left-
and right-handed helical chains along the a-axis; (d) view of the 2D layer in
complex 1; (e) the simplified representation of 2D layer in complex 1.
molecule and O7 of the carbonyl group from 3-dpye ligand
[O(1W)–H(1WA)⋯O(7), 2.7486 Å, 166°], generating a 3D supramo-
lecular structure (Fig. S1†). The hydrogen bonding data are
summarized in Table S1.†
Crystal structure description of [Cu(3-dpye)0.5(5-AIP)(H2O)]
(2). Crystal structure analyses reveal that complexes 2 and 7
are isostructural, so complex 2 is discussed here as the repre-
sentative example. Single crystal X-ray diffraction analysis
Fig. 2 (a) ORTEP drawing of complex 2 with thermal ellipsoids at 50% prob-
ability (the H atoms have been omitted for clarity.); (b) view of the 1D [Cu-5-AIP]
ladder-like chain in complex 2; (c) view of the 2D layer in complex 2; (d) the sim-
ˉ
reveals that 2 is in triclinic crystal system with P1 space group.
The asymmetric unit of 2 contains one Cu(II) ion, half of
3-dpye ligand, one 5-AIP anion and one coordinated water plified representation of 2D layer in complex 2.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8377

View Article Online
Paper
Dalton Transactions
the nitrogen atom (N3) from amino of 3-dpye and the oxygen considered as a five-connected node, whilst 3-dpye is regarded
atom O3 from carboxyl group of 5-AIP with N(3)–H(3B)⋯O(3), as a linker, and the final structure of 3 is a binodal 3,5-con-
3.3684 Å, 169°. The hydrogen bonding data are summarized in nected network with the point symbol of (42·67·8)(42·6)
Table S3.†
(Fig. 3d). The 2D network of 3 contains two types of hexagon
Crystal structure description of [Cu(3-dpye)(1,3-BDC)]·3H2O [Cu4(3-dpye)2(1,3-BDC)2] loops with dimensions ca. 15.24 ×
(3). Complex 3 was obtained by the similar procedure used for 15.75 Å2 (loop A) and 11.46 × 20.82 Å2 (loop B). Although two
complex 2, except that 1,3-H2BDC was used instead of 5-H2AIP. similar Cu(II) polymers based on the 3-dpye and 1,3-BDC
ˉ
It crystallizes in triclinic crystal system with P1 space group. mixed ligands have been reported, their crystal structures are
The asymmetric unit of 3 consists of one Cu(II) ion, one 3-dpye different.17 Biradha et al.17a reported the complex [Cu(3-
ligand, one 1,3-BDC anion, and three lattice water molecules. dpye)2(1,3-BDC)2]·6H2O, which represented a 0D species with a
Each Cu(II) ion is five-coordinated and displays a distorted protonated carboxyl group and a monodentate 3-dpye ligand.
pyramid geometry supplied by three carboxyl oxygen atoms More recently, our group17b also obtained a 3D polymer [Cu(3-
from three different 1,3-BDC anions [Cu1–O2 = 2.0272(18) Å, dpye)(1,3-BDC)(H2O)]·H2O exhibiting a 3-fold interpenetrating
Cu1–O3 = 1.9692(18) Å, Cu1–O6 = 2.220(2) Å], and two pyridyl structure. The formation of the 0D species may be ascribed to
nitrogen atoms from two 3-dpye ligands [Cu1–N1 = 2.035(2) Å, the solvothermal synthetic method, whilst the 3D and 2D fra-
Cu1–N3 = 2.027(2) Å] (Fig. 3a). In 3, the Cu(II) ions are con- meworks may be caused by the systematic pH in the same
nected by 1,3-BDC ligands with a bi(monodentate) bridging reactant.
mode to form a 1D [Cu-1,3-BDC] ladder-like structure (Fig. 3b
Crystal structure description of [Cu3(3-dpye)(1,2-BDC)2(μ2-
and Scheme S1c†). In addition, the adjacent metal Cu(II) ions OH)2] (4). Crystal structure analyses reveal that complexes 4
are connected by two μ2-bridging 3-dpye ligands to construct a and 5 are isostructural, so complex 4 is discussed here as an
1D [Cu-3-dpye] polymer chain (Fig. S3†). The neighboring [Cu- example. Single crystal X-ray diffraction analysis reveals that
1,3-BDC] ladder-like chains are linked by 3-dpye ligands to complex 4 is a 3D coordination polymer constructed from
form a 2D layer, as shown in Fig. 3c. Each 1,3-BDC can be con- Cu(II) ions, μ2-OH groups, 3-dpye ligands and 1,2-BDC anions.
sidered as a three-connected node and Cu(II) ion can be There are two crystallographically independent Cu(II) ions in 4.
The Cu1 ion is four-coordinated by two carboxyl oxygen atoms
from two different 1,2-BDC anions [Cu1–O1 and Cu1–O1#1,
1.941(3) Å], and two oxygen atoms from two coordinated
μ2-OH [Cu1–O6 and Cu1–O6#1, 1.895(2) Å], showing a distorted
tetrahedron coordination geometry. While the Cu2 ion is five-
coordinated by two carboxyl oxygen atoms from two different
1,2-BDC ligands [Cu2–O2 = 1.973(2) Å, Cu2–O3 = 1.964(2) Å],
one carbonyl oxygen atom from a 3-dpye ligand [Cu2–O5 =
2.4613(29) Å], one pyridyl nitrogen atom from another 3-dpye
ligand [Cu2–N1 = 2.070(3) Å], and one oxygen atom from a
coordinated μ2-OH group [Cu2–O6 = 1.895(2) Å], exhibiting a
distorted tetragonal pyramid coordination geometry (Fig. 4a
for 4 and Fig. S4† for 5). The 1,2-BDC components adopting a
bidentate–monodentate coordination mode alternately link
the Cu1 and Cu2, resulting in a 1D [Cu-1,2-BDC] zigzag chain
(Fig. 4b and Scheme S1d–e†) with the non-bonding Cu1⋯Cu2
distance of 3.5070(5) Å, Cu2⋯Cu2A distance of 3.5434(6) Å,
and Cu1⋯Cu1A distance of 8.3526(10) Å (distances: 3.3499(4) Å,
3.4145(5) Å, and 8.0878(8) Å in complex 5). As shown in
Fig. 4c, the 3-dpye ligand displays a μ4-bridging coordination
mode via ligation of two pyridyl nitrogen atoms and two carbo-
nyl oxygen atoms, which is different from the μ2-bridging
3-dpye in complexes 1–3. Therefore, μ4-bridging 3-dpye ligands
and μ2-OH connected the Cu(II) ions to form a 2D layer, in
which the large square-shape loops [Cu6(3-dpye)2(μ2-OH)4] are
approximately 13.80 × 13.92 Å2 in complex 4 (13.95 × 14.92 Å2
in complex 5) (Fig. S5†). Furthermore, the 1D [Cu(1,2-BDC)]
zigzag chains link these adjacent 2D layers to form an intri-
guing 3D net (Fig. S6†). It is necessary to simplify the building
blocks from the 3D metal–organic framework. Each Cu1 is sur-
Fig. 3 (a) ORTEP drawing of complex 3 with thermal ellipsoids at 50% prob-
ability (the lattice water molecules and H atoms have been omitted for clarity);
rounded by two 1,2-BDC ligands and two μ2-OH, which can be
(b) view of the 1D Cu-1,3-BDC ladder-like chain in complex 3; (c) view of the 2D
layer of complex 3; (d) the simplified representation of 2D layer for complex 3.
regarded as a four-connected node, and Cu2 is linked by two
8378 | Dalton Trans., 2013, 42, 8375–8386
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
Fig. 5 (a) ORTEP drawing of complex 6 with thermal ellipsoids at 50% prob-
ability. The lattice water molecules and H atoms have been omitted for clarity.
Symmetry code: #1 − x + 2, −y, −z + 1; (b) view of the 1D Cu-1,2-BDC double
chain in complex 6; (c) view of the 2D layer in complex 6; (d) the simplified rep-
resentation of 2D layer in complex 6.
and four carboxyl oxygen atoms from four different 1,2-BDC
ligands [Cu1–O1 = 1.952(3) Å, Cu1–O2 = 1.979(2) Å, Cu1–O4 =
1.941(3) Å, Cu1–O4#1 = 1.941(3) Å], showing a tetragonal
pyramid geometry. Each 1,2-BDC ligand adopts a monoden-
tate-bidentate bridging mode to connect three Cu(II) ions,
forming an infinite 1D [Cu-1,2-BDC] zigzag double chain in 6
(Fig. 5b and Scheme S1f†). The 1D double chains are further
connected by μ2-bridging 3-dpyh ligands to form the 2D layer
(Fig. 5c). Each Cu(II) can be considered as a four-connected
node and 1,2-BDC can be considered as a three-connected
node, and the structure of 6 is a binodal 3,4-connected 2D
network with the point symbol of (42·63·8)(42·6). There exist a
large hexagonal [Cu4(3-dpyh)2(1,2-BDC)2] loop of approxi-
mately 21.46 × 23.72 Å2 in complex 6 (Fig. 5d). Furthermore,
such 2D layers are further linked together by two O–H⋯O
hydrogen bonding interactions, one is between O1W of the
coordinated water molecule and O9 of the carbonyl group
from 3-dpyh ligand [O(1W)–H(1WA)⋯O(9), 2.8592 Å, 151°],
and the other is between O1W of the coordinated water mol-
ecule and O3 of the carboxyl group from 1,2-BDC ligand
[O(1W)–H(1WA)⋯O(3), 2.7340 Å, 177°], generating a 3D supramo-
lecular structure (Fig. S7†). The hydrogen bonding data are
summarized in Table S4.†
Fig. 4 (a) ORTEP drawing of complex 4 with thermal ellipsoids at 50% prob-
ability. The H atoms have been omitted for clarity. Symmetry code: #1 − x + 1,
−y, −z; (b) view of the 1D Cu-1,2-BDC chain in complex 4; (c) view of the 2D
layer in complex 4; (d) the simplified representation of 3D net in complex 4.
1,2-BDC ligands, two 3-dpye ligands and one μ2-OH, which can
be considered as a five-connected node. The 3-dpye ligand acts
as a 4-connector to bridge four Cu2 ions, and the 1,2-BDC
ligand serves as a 3-connector to link three Cu(II) ions (one
Cu1 ion and two Cu2 ions), thus the resulting structure of 4 is
a
novel 3,4,4,5-connected net with point symbol of
(3·4·5)2(3·42·5·86)2(32·8·92·10)(42·82·102) (Fig. 4d).
Crystal structure description of [Cu(3-dpyh)0.5(1,2-
BDC)]·H2O (6). Complex 6 was obtained by a similar procedure
to that of 4, except that 3-dpyh was used instead of 3-dpye.
X-ray structural analysis reveals that complex 6 is a 2D network
ˉ
in triclinic crystal system with P1 space group. As shown in
Fig. 5a, the asymmetric unit of complex 6 contains one Cu(II)
ion, one 1,2-BDC anion, half of 3-dpyh ligand, and one lattice
Effect of the dicarboxylates and flexible bis-pyridyl-bis-amide
ligands on the assembly and structures of the complexes
water molecule. Each Cu(II) is five-coordinated by one pyridyl As is well-known, dicarboxylates usually play an important role
nitrogen atom from a 3-dpyh ligand [Cu1–N1 = 1.993(3) Å], in constructing the target complexes. Complexes 1–4 show the
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8379

View Article Online
Paper
Dalton Transactions
effect of intrinsic structures for these dicarboxylates on the complex 6, the largest [Cu4(3-dpyh)2(1,2-BDC)2] loop (21.46 ×
final topologies: the 3-NPA and 5-AIP contain two carboxyl 23.72 Å2) was constructed. So the coordination modes and the
groups and one nitro or amino group, while the 1,3-BDC and spacer length of bis-pyridyl-bis-amide ligands also show an
1,2-BDC only possess two carboxyl groups in different pos- important effect on the dimensionalities and structures of the
itions. For 1, each 3-NPA anion, as a ‘V’-like linker, bridges two title complexes.
Cu(II) ions to generate a 1D zigzag chain, which is extended by
IR analysis
3-dpye to a 2D 4-connected (44·62) topology. In 2, each 5-AIP
anion, as a 3-connected node, links three Cu(II) ions to gener- The IR spectra of complexes 1–7 are determined in the
ate a 1D ladder-like chain, which is further connected by frequency range of 500–4000 cm−1, as shown in Fig. S10(a–g).†
3-dpye into a 2D 3,4-connected (42·63·8)(42·6) topology. Com- The strong peaks at 1625 and 1245 cm−1 for 1, 1614 and
pared with 5-AIP, the 1,2-BDC or 1,3-BDC has less coordination 1284 cm−1 for 2, 1612 and 1288 cm−1 for 3, 1613 and
sites, however, both are also serving as 3-connected nodes in 1207 cm−1 for 4, 1641 and 1201 cm−1 for 5, 1620 and
3 and 4. The different angles between the two carboxyl groups 1296 cm−1 for 6, 1618 and 1201 cm−1 for 7, may be attributed
in 1,3-BDC and 1,2-BDC anions (120° and 60°, respectively) to the asymmetric and symmetric vibrations of carboxyl
result in different Cu(II)-carboxylate motifs in 3 and 4. In 3, groups. The bands around 1650 cm−1 for 1, 1678 cm−1 for 2,
each 1,3-BDC anion links the Cu(II) ions to yield a 1D ladder- 1670 cm−1 for 3, 1643 cm−1 for 4, 1660 cm−1 for 5, and
like chain, which is further extended by the 3-dpye ligands 1651 cm−1 for 6, 1660 cm−1 for 7, are characteristic of the car-
into a 2D layer with (42·67·8)(42·6) topology. However, in 4, bonyl groups. The presence of the characteristic bands at
each 1,2-BDC anion links the Cu(II) ions to generate a 1D 1560, 1479, 1433, 1348 cm−1 for 1, 1556, 1479, 1415,
zigzag chain, which is further extended by the 3-dpye ligands 1363 cm−1 for 2, 1544, 1475, 1431, 1369 cm−1 for 3, 1550,
into
a
3D framework with (3·4·5)2(3·42·5·86)2(32·8·92·10) 1473, 1402, 1320 cm−1 for 4, 1544, 1479, 1400, 1319 cm−1 for
(42·82·102) topology. Comparing 3 with 4, it is clear that 5, 1581, 1483, 1400, 1359 cm−1 for 6, 1558, 1479, 1415,
the positions of the carboxyl groups show an important 1363 cm−1 for 7, suggest the νC–N stretching vibrations of
influence on the coordination mode of 3-dpye and structures the pyridyl ring of the 3-dpye, 3-dpyb or 3-dpyh ligands.
of the complexes. Comparing 1 with 4, or 2 with 3, it is not For complexes 1–3 and 6–7, the strong absorption peaks
difficult to find that the substitute groups of dicarboxylates observed at 3344, 3439, 3487, 3433, and 3363 cm−1 indicate
also show some effect on the final structures. In addition, the presence of –OH groups of water molecules. The bands at
complexes 6 and 7 based on the same 3-dpyh ligand and 3420 and 3404 cm−1 can be assigned to stretching and
different dicarboxylates exhibit different 2D topological struc- bending vibrations of μ2-OH groups for complexes 4–5,
tures, which also indicate the effect of dicarboxylates on the respectively.
final structures. Therefore, we can conclude that both the sub-
stitute group and position of carboxyl group of the dicarboxy-
X-ray powder diffraction and thermogravimetric analyses
lates play significant roles in the construction of the title The X-ray powder diffraction (XRPD) patterns for complexes
complexes.
1–7 are presented in Fig. S11.† The as-synthesized patterns are
It is clear that the bis-pyridyl-bis-amide ligands also show in good agreement with the corresponding simulated ones,
obvious effect on the final architectures. In complexes 1–4, the indicating the phase purities of the samples.
3-dpye ligand adopts two kinds of coordination modes:
To estimate the stability of the title complexes, thermogravi-
μ2-bridging mode in 1–3 with 2D topological structures, and metric (TG) analyses are performed for complexes 1–7
μ4-bridging mode in 4 with 3D topological structure, which indi- (Fig. S12†). The TG curves of complexes 1–3 and 6–7 show two
cate that the coordination mode of 3-dpye show a great effect weight loss steps in the temperature range of 20–770 °C. The
on the dimensionality of complexes. Complexes 4–6 based on first weight loss stages start at 40 °C up to 171 °C for 1, 67 °C
the same 1,2-BDC anion also exhibit the effect of coordination up to 89 °C for 2, 69 °C up to 116 °C for 3, 56 °C up to 75 °C
modes of bis-pyridyl-bis-amide ligands on the dimensionality for 6, 72 °C up to 152 °C for 7, with the weight loss of about
of target complexes. As described above, 4 and 5 are isostruc- 11.63% for 1, 4.04% for 2, 9.34% for 3, 4.51% for 6, 3.78% for
tural 3D frameworks, in which both the 3-dpye and 3-dpyb 7, corresponding to the loss of the water molecules (calcd
show μ4-bridging mode, while in complex 6, the 3-dpyh adopts 11.71% for 1, 4.55% for 2, 9.78% for 3, 4.41% for 6, 3.91% for
a μ2-bridging mode, resulting in the formation of a 2D 7). The second weight loss occurring from 352 °C to 550 °C for
network. Similarly, the isostructural complexes 2 and 7 based 1, 148 °C to 607 °C for 2, 168 °C to 580 °C for 3, 221 °C to
on the same dicarboxylate 5-AIP and different bis-pyridyl-bis- 512 °C for 6, 255 °C to 434 °C for 7, may suggest the decomp-
amide ligands further show that the coordination mode of the osition of organic ligands. The weight losses are about 75.23%
bis-pyridyl-bis-amide play a key role in the final networks. In for 1, 74.85% for 2, 75.63% for 3, 75.76% for 6, 78.85% for 7,
addition, the spacer length of bis-pyridyl-bis-amide ligands in correspondence with the calculated value of 75.28% for 1,
also show a subtle effect on the final structures. In the iso- 75.24% for 2, 75.73% for 3, 75.98% for 6, 78.70% for 7,
structural 4 and 5, the large loops [Cu6(3-dpye)2(μ2-OH)4] in 4 respectively. The remaining weights (13.14% for 1, 21.11% for
and [Cu6(3-dpyb)2(μ2-OH)4] in 5 are different in size. When the 2, 15.03% for 3, 19.73% for 6, 17.37% for 7) correspond to the
ligand 3-dpyh with the longest spacer –(CH2)6– was used in percentage (13.01% for 1, 20.21% for 2, 14.49% for 3, 19.61%
8380 | Dalton Trans., 2013, 42, 8375–8386
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
for 6, 17.39% for 7) of Cu and O components in CuO.
Results of the TG analyses of complexes 4–5 show that the
two complexes possess similar thermal stabilities: the
curve appears as a straight line up to 212 °C for 4 and 167 °C
for 5, respectively. Beyond this temperature, the organic com-
ponents (1,2-BDC and 3-dpye/or 3-dpyb) begin to decompose.
When the temperature is up to 429 °C for 4 and 587 °C for 5,
the weight lost about 70.26% for 4, 71.43% for 5 (calcd 70.77%
for 4, 71.74% for 5), and the frameworks (29.74% for 4,
28.57% for 5) finally collapse to CuO (29.23% for 4, 28.26%
for 5).
Fluorescent properties
In the recent years, the fluorescent properties of a variety of
transition metal complexes have been reported. The Zn/Cd
complexes are the most commonly reported fluorescent com-
pounds, because the d10 metal ions not only possess various
coordination numbers and geometries, but also exhibit lumi-
nescent properties when bound to functional ligands.18 The
Cu(II) complexes do not contain d10 metal centers, but a series
of fluorescent Cu(II) complexes have been reported.19 Density
functional theory calculation indicates that the fluorescence
may be mainly attributed to the coupling of ligand-to-metal
charge transfer (LMCT) and metal-centered transitions.18
Therefore, the fluorescent properties of complexes 1–7 were
investigated in the solid state at room temperature. To under-
stand the nature of these emission bands, we also examined
the fluorescent properties of the free ligands. As shown in
Fig. 6a, the free 3-dpye ligand displays fluorescence with an
emission maximum at 385 nm (λex = 340 nm), while the fluor-
escent emission bands of complexes 1–4 are λem = 400 nm for
1, 382 nm for 2, 413 nm for 3, 400 nm for 4 (λex = 320 nm for
1–3, and λex = 310 nm for 4), respectively. As far as we know,
the polycarboxylates (3-NPA, 5-AIP, 1,3-BDC and 1,2-BDC) show
very weak π*–n transitions and contribute a little to the photo-
luminescence of the title complexes at room temperature.20
For complex 2, the fluorescence is similar to that of the free
ligand 3-dpye, which may probably be attributed to the intrali-
gand π*→π charge transitions.21 For complexes 1, 3 and 4, it is
clear that an obvious red-shifted (15 nm for 1 and 4, 28 nm for
3) emission band has been observed comparing with the free
3-dpye. Therefore, the fluorescence behavior of 1, 3 and 4 can
be attributed to the ligand-to-metal charge-transfer (LMCT),
which is similar to the reported d10 metal complexes with
Fig. 6 The emission spectra of complexes 1–7 and the free ligands (a) 3-dpye,
N-donor ligands.22 The differences of fluorescence behavior (b) 3-dpyb and (c) 3-dpyh.
for complexes 1–4 are probably caused by the different coordi-
nation environment of Cu(II) ions with N-donor ligands. In
complex 1, 3, and 4, the neighboring Cu(II) ions are linked by architectures. The results further highlight that photolumines-
3-dpye ligands building 1D chains, while in 2 the Cu(II) ions cent behavior has a close relationship with the coordination
and 3-dpye ligands have not constituted a 1D chain. As shown environment of metal ions and the structures of the title com-
in Fig. 6b, the free 3-dpyb ligand displays fluorescence with an plexes.23 As shown in Fig. 6c, the free 3-dpyh ligand displays
emission maximum at 388 nm (λex = 320 nm), while the fluor- fluorescence with an emission maximum at 400 nm (λex
=
escent emission band of complex 5 is λem = 400 nm (λex 320 nm), while the strong fluorescent emission band of com-
=
320 nm), which also can be attributed to the ligand-to-metal plexes 6 and 7 is λem = 398 nm and 396 nm (λex = 320 nm),
charge-transfer (LMCT).20 The similar fluorescent emission which may also probably be attributed to the intraligand π*→π
bands for complexes 4 and 5 may be due to their isostructural charge transitions. The fluorescent properties of 1–7 indicates
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8381

View Article Online
Paper
Dalton Transactions
that they may be anticipated as potential photoactive
materials, especially for complex 6.
Electrochemical behaviors
Fig. 7 and Fig. S13† show the cyclic voltammograms of com-
plexes 1–7 bulk-modified carbon paste electrodes (1-, 2-, 3-, 4-,
5-, 6-, 7-CPE) in 0.01 M H2SO4–0.5 M Na2SO4 aqueous solution.
It can be seen that an obvious redox couple was observed in
the potential range of +700 to 100 mV for 1-CPE, +550 to
150 mV for 2-CPE, +500 to −450 mV for 3-CPE and 6-CPE, +600
to 250 mV for 4-CPE and 5-CPE, +600 to 200 mV for 7-CPE.
The mean peak potential E1/2 = (Epa + Epc)/2 is 40 mV for 1,
+45 mV for 2, −73 mV for 3, +45 mV for 4, +36 mV for 5,
−25 mV for 6, +50 mV for 7 (100 mV s−1), which could be
attributed to the redox of Cu(II)/Cu(I).24 The differences of the
mean peak potentials and peak currents among the title com-
plexes may be attributed to the different coordination environ-
ment of Cu(II) and the final composition and structures of the
title complexes.25 The cyclic voltammograms of all the
Cu-CPEs showed reversible or quasi-reversible redox couple of
Cu(II)/Cu(I). Compared with other groups’ works,26 the reversibil-
ity of CVs with the title complexes are better.
Scan rates effect on the electrochemical behaviors of the
1–7-CPE were investigated in the potential range of +700 to
100 mV, +550 to 150 mV, +500 to −450 mV, +600 to 250 mV,
+600 to 250 mV, +500 to −450 mV, +600 to 200 mV in 0.01 M
H2SO4–0.5 M Na2SO4 aqueous solution, respectively. As shown
in Fig. 8 and Fig. S14,† with the scan rates increasing from
20 to 280 mV s−1 for 1-, 2-, 3-, 6-, 7-CPE, and 20 to 200 mV s−1 for
4-, 5-CPE, the peak potentials of the 1–7-CPE change gradually:
the cathodic peak potentials gradually shift to the negative
direction and the corresponding anodic peak potentials shift
to the positive direction. The insets of Fig. 8 and Fig. S14†
show that the peak currents are proportional to the scan rates
up to 280 mV s−1 for 1-, 2-, 3-, 6-, 7-CPE, and to 200 mV s−1 for
4-, 5-CPE, respectively, suggesting that the redox processes for
1–7-CPE are surface controlled.27
Fig. 8 Cyclic voltammograms of the 1-CPE in 0.1 M H2SO4–0.5 M Na2SO4
aqueous solution at different scan rates (from inner to outer: 20, 40, 60, 80,
100, 120, 140, 160, 180, 200, 220, 240, 260, 280 mV s−1). The inset shows the
plots of the anodic and cathodic peak currents against scan rates.
Fig. S15† shows cyclic voltammograms for the electrocataly-
tic reduction of nitrite at a bare CPE and the 1-, 2-, 4-, 5-, 7-
CPE in 0.01 M H2SO4–0.5 M Na2SO4 aqueous solution. There is
no redox peak at the bare CPE at the presence of nitrite in the
potential range of +550 to 150 mV and +600 to 250 mV. With
the addition of nitrite, the reduction peak currents increase
gradually while the corresponding oxidation peak currents
decrease gradually at the 1-, 2-, 4-, 5-, 7-CPE. We also examined
the electrocatalytic reduction of nitrite at the 3-, 6-CPE,
however, there is no obvious reduction peak. Thus, the results
indicate that 1-, 2-, 4-, 5-, 7-CPE exhibit electrocatalytic activity
toward the reduction of nitrite.
Photocatalytic property
It is well known that some coordination polymers have been
reported to be good catalysts for the photo-degradation of
organic dyes in recent years. But most of these polymers are
constructed from the polyoxometalates building blocks.28 By
contrast, the investigations on the photocatalytic activities of
metal–organic coordination polymers are less.29 Here the
photocatalytic performance of complexes 1–7 for the degra-
dation of methylene blue (MB) were investigated through a
typical process: 150 mg powder of the title complexes was dis-
persed in the MB solution (10.0 mg L−1), magnetically stirred
in the dark for 0.5 h to ensure the equilibrium of the working
solution. The solution was then exposed to UV irradiation
from a 125 W Hg lamp and kept continuously stirring. 3.0 mL
of sample was taken out every 30 min for analysis. The photo-
catalytic properties of title complexes are shown in Fig. 9 and
Fig. S16.† It can be seen that the absorption peak of MB
decreased obviously along with the reaction time for the title
complexes. Moreover, the concentrations of MB (C) against
reaction time (t) of the title complexes were plotted. The calcu-
lation results show that approximately 80% of MB had been
decomposed after 240 min with 3 and 6 as photocatalysts and
the dissociation of MB was no more than 5% without any
Fig. 7 Cyclic voltammograms of 1-CPE (+700 to 100 mV) in 0.01 M H2SO4–0.5 M
Na2SO4 aqueous solution. Scan rate: 100 mV s−1
.
8382 | Dalton Trans., 2013, 42, 8375–8386
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
one electron to return to its stable state. During the photocata-
lytic process of complexes 1–7, the central Cu(II) ions and the
ligands are involved. In order to return to its stable state for
HOMO, the charge transfer excited state (bis-pyridyl-bis-amide
ligands and aromatic polycarboxylates) was oxygenated water
molecules to generate the ·OH radicals.31 Thus, the ·OH active
species could decompose the MB to complete the photocataly-
tic process. In order to investigate the stability of complexes
1–7 as photocatalysts, we repeated the IR patterns of com-
plexes 1–7 after the photocatalytic experiments, and the IR
spectra are almost identical with those of the as-prepared
samples (Fig. S10†). Control experiments were also carried out
for the complexes. The CuCl2·2H2O, four aromatic dicarboxy-
lates (3-H2NPA, 5-H2AIP, 1,3-H2BDC and 1,2-H2BDC), and
three flexible bis-pyridyl-bis-amide ligands (3-dpye, 3-dpyb and
3-dpyh) were added to the MB solution under UV irradiation,
respectively. However, they did not show observable photocata-
lytic activities. In addition, it shows no obvious MB degra-
dation in the dark. The results indicate that complexes 1–7
may be good candidates for the photocatalytic degradation of
MB, which would have potential photocatalytic activity in the
reduction of some other organic dyes.
Conclusions
Three flexible bis-pyridyl-bis-amide ligands (3-dpye, 3-dpyb, 3-dpyh)
with different spacers were introduced into the copper(II)–
dicarboxylates systems and five 2D and two 3D multifunc-
tional Cu(II) coordination polymers were obtained. In these
polymers, the dicarboxylates exhibit different coordination
modes or coordination capacities due to their different substi-
tute group or position of carboxyl groups, and connect the
Cu(II) ions to form different metal-dicarboxylates chains, which
reveals their great effect on the formation of the ultimate
coordination architectures. In addition, three flexible bis-
pyridyl-bis-amide ligands adopt two types of coordination
modes: a μ2-bridging mode in 1–3 (for 3-dpye), 6 and 7 (for
3-dpyh), a μ4-bridging coordination mode in 4 and 5 (for 3-dpye
and 3-dpyb), which plays an important role in determining the
dimensionality of the title complexes. Both the four dicarboxy-
lates and the three flexible bis-pyridyl-bis-amide ligands with
different spacer length play important roles in the construc-
tion and properties of the versatile copper complexes. The title
complexes exhibit intense fluorescence emissions, good elec-
trochemical behaviors and excellent photocatalytic activities,
which may make them potential candidates for luminescent,
electrochemical and photocatalytic materials.
Fig. 9 (a–b) Absorption spectra of the MB solution during the decomposition
reaction under UV irradiation with the presence of complex 3 and 6. (c) Photo-
catalytic decomposition rates of MB solution under UV irradiation with the use
of the title compounds and no crystal in the same conditions.
catalyst. As is known, the differences of photocatalytic activi-
ties of metal–organic coordination polymers may be attributed
to the different central metals and organic ligands, as well as
the final structures of the complexes.30 In the presence of UV
light, there is an electron transfer from the highest occupied
Experimental section
General considerations
molecular orbital (HOMO) to the lowest unoccupied molecular All reagents and solvents for syntheses were purchased from
orbital (LUMO). The electron of the excited state in the LUMO commercial sources and used without further purification.
is usually very unstable, while the HOMO strongly demands The ligand 3-dpye, 3-dpyb and 3-dpyh were synthesized by the
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8383

View Article Online
Paper
Dalton Transactions
reported procedure.32 Elemental analyses (C, H, N) were per- adjust the systematic pH. Green block crystals of 4 were obtained
formed on a Perkin-Elmer 240C element analyzer. FT-IR (yield: ca. 30% based on Cu). Anal. Calcd for C30H22Cu3N4O12: C
spectra (KBr pellets) were obtained on a Shimadzu FT-IR 8400 43.84, H 2.68, N 6.82. Found: C 43.81, H 2.69, N 6.86%. IR (KBr,
spectrometer. Powder XRD investigations were carried out with cm−1): 3884w, 3743w, 3419w, 3186w, 3082w, 2356s, 1718m,
an Ultima IV with D/teX Ultra diffractometer at 40 kV, 40 mA 1643s, 1550m, 1473m, 1402s, 1207m, 1137w, 1091w, 1045w,
with Cu Kα (λ = 1.5406 Å) radiation. Thermogravimetric data 947w, 891w, 821m, 744m, 657m, 601s, 555w, 515w.
for complexes 1–7 were carried out on a Pyris Diamond
thermal analyzer. Fluorescence spectra were recorded at room thesis method of 5 is similar to that of 4 except for ligand
temperature on Hitachi F-4500 fluorescence/phosphor- 3-dpyb (0.030 g, 0.1 mmol) as the substitute of 3-dpye, and the
Synthesis of [Cu3(3-dpyb)(1,2-BDC)2(μ2-OH)2] (5). The syn-
a
escence spectrophotometer. A CHI 440 electrochemical work- different amount of NaOH (0.016 g, 0.40 mmol) was added to
station connected to a Digital-586 personal computer was used adjust the systematic pH. Blue block crystals of 5 were
for control of the electrochemical measurements and for data obtained (yield: ca. 34% based on Cu). Anal. Calcd for
collection. A conventional three-electrode system was used C32H26Cu3N4O12: C 45.22, H 3.06, N 6.59. Found: C 45.21, H
with an SCE as reference electrode, a platinum wire as auxili- 3.09, N 6.56%. IR (KBr, cm−1): 3857w, 3801w, 3404m, 3062w,
ary electrode and the modified electrodes as the working elec- 2358m, 1641s, 1544s, 1479m, 1400s, 1319m, 1201m, 1157m,
trodes, respectively. UV-Vis absorption spectra were obtained 1107m, 1033w, 827w, 806w, 752m, 700m, 651w, 584w.
using a SP-1900 UV-Vis spectrophotometer.
Synthesis of [Cu(3-dpyh)0.5(1,2-BDC)]·H2O (6). The synthesis
method of 6 is similar to that of 4 except for ligand 3-dpyh
(0.033 g, 0.1 mmol) as the substitute of 3-dpye, and the
Preparation of complexes 1–7
Synthesis of [Cu(3-dpye)(3-NPA)(H2O)]·3H2O (1). A mixture different amount of NaOH (0.016 g, 0.40 mmol) was added to
of CuCl2·2H2O (0.034 g, 0.2 mmol), 3-dpye (0.027 g, 0.1 mmol), adjust the systematic pH. Blue block crystals of 5 were
3-H2NPA (0.032 g, 0.15 mmol), H2O (12 mL) and NaOH obtained (yield: ca. 32% based on Cu). Anal. Calcd for
(0.017 g, 0.42 mmol) was stirred for 30 min at room tempera- C17H16CuN2O6: C 50.02, H 3.92, N 6.87. Found: C 50.01, H
ture and then transferred to a 25 mL Teflon-lined autoclave 3.90, N 6.89%. IR (KBr, cm−1): 3433w, 3197w, 3064w, 2920w,
and kept at 120 °C for 4 days. After slowly cooling to room 2854w, 2360m, 1620s, 1581s, 1554s, 1510w, 1483m, 1400s,
temperature, blue block crystals of 1 were obtained (yield: ca. 1359s, 1296w, 1203m, 1143m, 1070w, 1035w, 831m, 792m,
33% based on Cu). Anal. Calcd for C22H25CuN5O12: C 42.93, H 700m, 651w, 572w.
4.06, N 11.38. Found: C 42.95, H 4.03, N 11.36%. IR (KBr,
Synthesis of [Cu(3-dpyh)0.5(5-AIP)(H2O)] (7). The synthesis
cm−1): 3803w 3732w, 3344m, 2869w, 2362m, 1651s, 1625s, method of 7 is similar to that of 6 except for ligand 5-H2AIP
1560s, 1531s, 1479m, 1433m, 1348s, 1303m, 1245w, 1174w, (0.027 g, 0.15 mmol) as the substitute of 1,2-H2BDC, and the
1126w, 1068w, 891w, 855m, 783m, 752m, 702s, 663w, 569w.
different amount of NaOH (0.014 g, 0.36 mmol) was added to
Synthesis of [Cu(3-dpye)0.5(5-AIP)(H2O)] (2). The synthesis adjust the systematic pH. Green block crystals of 7 were
method of 2 is similar to that of 1 except for ligand 5-H2AIP obtained (yield: ca. 30% based on Cu). Anal. Calcd for
(0.027 g, 0.15 mmol) as the substitute of 3-H2NPA, and the C17H22CuN3O8: C 44.36, H 4.78, N 9.13. Found: C 44.38, H
different amount of NaOH (0.016 g, 0.40 mmol) was added to 4.79, N 9.15%. IR (KBr, cm−1): 3857w, 3364m, 3261m, 3078m,
adjust the systematic pH. Green block crystals of 2 were 2931m, 2333m, 1660s, 1618s, 1558s, 1479m, 1415m, 1363s,
obtained (yield: ca. 35% based on Cu). Anal. Calcd for 1321m, 1201w, 1143w, 1112m, 1021w, 962w, 933w, 777m,
C15H14CuN3O6: C 45.47, H 3.54, N 10.61. Found: C 45.46, H 734s, 684m, 624m, 584w, 551w.
3.55, N 10.63%. IR (KBr, cm−1): 3735w, 3357m, 3126m, 3082w,
Preparation of complexes 1–7 bulk-modified CPEs. The
2360m, 2333m, 1678s, 1614m, 1556s, 1475w, 1415s, 1363s, complexes 1–7 bulk-modified CPEs (1-, 2-, 3-, 4-, 5-, 6-, 7-CPE)
1334m, 1284w, 1224w, 1197w, 1172w, 1112m, 1064w, 960m, were fabricated by mixing 0.50 g graphite powder and 0.030 g
781m, 707w, 597w.
complexes 1–7 in an agate mortar for approximately 30 min to
Synthesis of [Cu(3-dpye)(1,3-BDC)]·3H2O (3). The synthesis achieve a uniform mixture; then 0.16 mL paraffin oil was
method of 3 is similar to that of 2 except for ligand 1,3-H2BDC added and stirred with a glass rod.33 The homogenized
(0.025 g, 0.15 mmol) as the substitute of 5-H2AIP, and the mixture was packed into a 3 mm inner diameter glass tube
different amount of NaOH (0.012 g, 0.30 mmol) was added to and the tube surface was wiped with weighing paper. The elec-
adjust the systematic pH. Green block crystals of 3 were obtained trical contact was established with the copper wire through the
(yield: ca. 28% based on Cu). Anal. Calcd for C22H24CuN4O9: C back of the electrode. The bare CPE was prepared by a similar
47.83, H 4.35, N 10.15. Found: C 47.81, H 4.39, N 10.17%. IR process without complexes 1–7.
(KBr, cm−1): 3876w, 3649w, 3365w, 3197w, 2333m, 1612s, 1544s,
1475m, 1431m, 1369s, 1319m, 1288w, 1272w, 1201w, 1168w,
X-Ray crystallography
1062w, 1035w, 825w, 742m, 721m, 700m, 655w, 520w.
Crystallographic data for complexes 1–7 were collected on a
Synthesis of [Cu3(3-dpye)(1,2-BDC)2(μ2-OH)2] (4). The syn- Bruker SMART APEX II with Mo Kα (λ = 0.71073 Å) by ω and θ
thesis method of 4 is similar to that of 2 except that ligand 1,2- scan mode. All the structures were solved by direct methods
H2BDC (0.025 g, 0.15 mmol) was used instead of 5-H2AIP, and SHELXS program of the SHELXTL package.34 For complexes
the different amount of NaOH (0.014 g, 0.36 mmol) was added to 1–7, the crystal parameters, data collection, and refinement
8384 | Dalton Trans., 2013, 42, 8375–8386
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
Table 1 Crystallographic data for complexes 1–7
Complex
1
2
3
4
5
6
7
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C
22H25CuN5O12 C15H14CuN3O6 C22H24CuN4O9 C30H22Cu3N4O12 C32H26Cu3N4O12 C17H16CuN2O6 C17H22CuN3O8
615.01
Monoclinic
P21/c
9.0931(6)
13.8662(10)
20.4468(15)
90
92.7390(10)
90
2575.1(3)
4
395.83
Triclinic
ˉ
P1
551.99
Triclinic
ˉ
P1
821.14
Triclinic
ˉ
P1
849.19
Triclinic
ˉ
P1
407.86
Triclinic
ˉ
P1
459.92
Triclinic
ˉ
P1
6.9268(7)
10.0557(11)
11.1566(13)
104.553(2)
99.146(2)
98.756(2)
727.43(14)
2
10.004(3)
10.719(3)
11.754(3)
106.938(5)
101.838(5)
92.317(4)
1173.2(6)
2
8.3526(10)
8.6543(10)
10.7547(13)
85.213(2)
75.719(2)
80.446(2)
742.20(15)
1
8.0878(7)
8.8044(8)
11.3643(10)
85.133(2)
75.9090(10)
87.445(2)
781.81(12)
1
5.9159(12)
11.620(2)
12.661(3)
74.184(4)
80.552(4)
81.929(4)
821.9(3)
2
8.9363(10)
10.1567(12)
10.7519(12)
80.852(2)
79.235(2)
74.262(2)
916.69(18)
2
γ (°)
V (Å3)
Z
Dc (g cm−3
)
1.586
0.922
1268
1.807
1.563
1.837
1.804
1.648
1.666
μ (mm−1
F (000)
)
1.544
404
0.992
570
2.205
413
2.097
429
1.368
418
1.245
476
Reflection collected 14 512
4182
2824
232
0.0223
1.006
0.0432
0.0978
6230
4091
325
0.0165
1.048
0.0356
0.0925
3804
2586
223
0.0107
1.049
0.0306
0.0867
4135
2747
232
0.0107
1.064
0.0284
0.0822
3721
2836
241
0.0296
0.984
0.0447
0.0992
4680
3196
262
0.0166
1.040
0.0441
0.1154
Unique reflections
Parameters
Rint
5046
361
0.0342
1.055
0.0418
0.1106
GOF
R1a [I > 2σ(I)]
wR2b (all data)
a R1 = Σ||Fo| − |Fc||/Σ|Fo|. b wR2 = Σ[w(Fo2 − Fc2)2]/Σ[w(Fo2)2]1/2
.
results are summarized in Table 1. Selected bond distances
and bond angles are listed in Table S1.† Hydrogen bonding
geometries of complexes 1, 2 and 6 are summarized in Tables
S2–S4.† CCDC 889598, 889600, 889599, 889597, 891322,
891323, and 909348 for complexes 1–7 contain the supplemen-
tary crystallographic data in this paper.
4 (a) X. M. Zhang, Y. Q. Wang, Y. Song and E. Q. Gao, Inorg.
Chem., 2011, 50, 7284; (b) T. Stamatatos, G. Vlahopoulou,
C. Raptopoulou, V. Psycharis, A. Escuer, G. Christou and
S. Perlepes, Eur. J. Inorg. Chem., 2012, 19, 3121.
5 (a) X. C. Zhu, S. W. Wang, S. L. Zhou, Y. Wei, L. J. Zhang,
F. H. Wang, Z. J. Feng, L. P. Guo and X. L. Mu, Inorg.
Chem., 2012, 51, 7134; (b) M. Tonigold, Y. Lu,
A. Mavrandonakis, A. Puls, R. Staudt, J. Möllmer, J. Sauer
and D. Volkmer, Chem.–Eur. J., 2011, 17, 8671.
Acknowledgements
6 (a) Y. P. He, Y. X. Tan, F. Wang and J. Zhang, Inorg. Chem.,
2012, 51, 1995; (b) W. Y. Gao, W. M. Yan, R. Cai,
K. Williams, A. Salas, L. Wojtas, X. D. Shi and S. Q. Ma,
Chem. Commun., 2012, 48, 8898.
7 (a) J. Zhang, E. Chew, S. M. Chen, J. H. Pham and X. H. Bu,
Inorg. Chem., 2008, 47, 3495; (b) J. H. Qin, L. F. Ma, Y. Hu
and L. Y. Wang, CrystEngComm, 2012, 14, 2891.
The supports of the National Natural Science Foundation of
China (No. 20871022, 21171025), New Century Excellent
Talents in University (NCET-09-0853), the Natural Science
Foundation of Liaoning Province (No. 201102003) and
Program of Innovative Research Team in University of Liaoning
Province (LT2012020) are gratefully acknowledged.
8 (a) L. F. Ma, L. Y. Wang, D. H. Lu, S. Batten and J. G. Wang,
Cryst. Growth Des., 2009, 9, 1741; (b) L. Z. Yang, L. Jiang,
X. L. Feng and T. B. Lu, CrystEngComm, 2008, 10, 649.
9 (a) G. G. Luo, H. B. Xiong and J. C. Dai, Cryst. Growth Des.,
2011, 11, 507; (b) E. Escudero-Adán, J. Benet-Buchholz and
A. Kleij, Inorg. Chem., 2008, 47, 410.
References
1 (a) Y. Tezuka and H. Oike, J. Am. Chem. Soc., 2001, 123,
11570; (b) K. Kasai, M. Aoyagi and M. Fujita, J. Am. Chem.
Soc., 2000, 122, 2140; (c) D. Kumar, A. Das and P. Dastidar,
Inorg. Chem., 2007, 46, 7351; (d) C. Livage, P. Forster, 10 (a) J. W. Ye, J. Y. Zhang, L. Ye, D. Xie, T. Xu, G. Li and
N. Guillou, M. Tafoya, A. Cheetham and G. Férey, Angew.
Chem., Int. Ed., 2007, 119, 5981.
2 (a) B. M. Ji, D. S. Deng, X. He, B. Liu, S. B. Miao, N. Ma,
W. Z. Wang, L. G. Ji, P. Liu and X. F. Li, Inorg. Chem., 2012,
G. L. Ning, Dalton Trans., 2008, 5342; (b) Y. L. Gai,
F. L. Jiang, K. C. Xiong, L. Chen, D. Q. Yuan, L. J. Zhang,
K. Zhou and M. C. Hong, Cryst. Growth Des., 2012, 12,
2079.
51, 2170; (b) L. Q. Mo, J. H. Jia, L. J. Sun and Q. M. Wang, 11 Y. F. Hsu, W. Hsu, C. J. Wu, P. C. Cheng, C. W. Yeh,
Chem. Commun., 2012, 48, 8691.
3 (a) K. Hanson, L. Roskop, N. Patel, L. Griffe, P. Djurovich,
W. J. Chang, J. D. Chen and J. C. Wang, CrystEngComm,
2010, 12, 702.
M. Gordon and M. Thompson, Dalton Trans., 2012, 41, 12 G. M. Sun, Y. M. Song, Y. Liu, X. Z. Tian, H. X. Huang,
8648; (b) Q. Ma, M. L. Zhu, C. X. Yuan, S. S. Feng, L. P. Lu
and Q. M. Wang, Cryst. Growth Des., 2010, 10, 1706.
Y. Zhu, Z. J. Yuan, X. F. Feng, M. B. Luo, S. J. Liu, W. Y. Xu
and F. Luo, CrystEngComm, 2012, 14, 5714.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 8375–8386 | 8385

View Article Online
Paper
Dalton Transactions
13 (a) G. X. Liu, K. Zhu, H. M. Xu, S. Nishihara, R. Y. Huang
and X. M. Ren, CrystEngComm, 2010, 12, 1175; (b) J. Y. Lee,
(b) X. J. Wang, Y. H. Liu, C. Y. Xu, Q. Q. Guo, H. W. Hou
and Y. T. Fan, Cryst. Growth Des., 2012, 12, 2435.
C. Y. Chen, H. M. Lee, E. Passaglia, F. Vizza and 22 L. Zhang, J. L. Zhao, Q. P. Lin, Y. Y. Qin, J. Zhang,
W. Oberhauser, Cryst. Growth Des., 2011, 11, 1230;
(c) C. Y. Wang, Z. M. Wilseck, R. M. Supkowski and
P. X. Yin, J. K. Cheng and Y. G. Yao, Inorg. Chem., 2009,
48, 6517.
R. L. LaDuca, CrystEngComm, 2011, 13, 1391; (d) G. M. Sun, 23 (a) Y. Y. Liu, Z. H. Wang, J. Yang, B. Liu, Y. Y. Liu and
H. X. Huang, X. Z. Tian, Y. M. Song, Y. Zhu, Z. J. Yuan,
W. Y. Xu, M. B. Luo, S. J. Liu, X. F. Feng and F. Luo, Crys-
tEngComm, 2012, 14, 6182; (e) S. Pandey, P. P. Das,
A. K. Singh and R. Mukherjee, Dalton Trans., 2011, 40,
10758.
J. F. Ma, CrystEngComm, 2011, 13, 3811; (b) J. S. Hu,
Y. J. Shang, X. Q. Yao, L. Qin, Y. Z. Li, Z. J. Guo,
H. G. Zheng and Z. L. Xue, Cryst. Growth Des., 2010, 10,
2676.
24 (a) A. Salimi, V. Alizadeh and H. Hadadzadeh, Electroanaly-
sis, 2004, 16, 1984; (b) B. K. Santra, P. N. Reddy,
G. Neelakanta, S. Mahadevan, M. Nethajia and
A. R. Chakravartya, J. Inorg. Biochem., 2002, 89, 191;
(c) H. Y. Lin, X. L. Wang, H. L. Hu, B. K. Chen and
G. C. Liu, Solid State Sci., 2009, 11, 643.
14 (a) C. W. Yeh, J. D. Chen and J. C. Wang, Polyhedron, 2008,
27, 3611; (b) S. Pandey, P. P. Das, A. K. Singh and
R. Mukherjee, Dalton Trans., 2011, 40, 10758;
(c) H. R. Khavasi and B. M. Sadegh, Cryst. Growth Des., 2012,
12, 4798; (d) Z. Z. Yuan, F. Luo, Y. M. Song, G. M. Sun,
X. Z. Tian, H. X. Huang, Y. Zhu, X. F. Feng, M. B. Luo, 25 S. Hazra, S. Majumder, M. Fleck, N. Aliaga-Alcalde and
S. J. Liu and W. Y. Xu, Dalton Trans., 2012, 41, 12670. S. Mohanta, Polyhedron, 2009, 28, 3707.
15 (a) X. L. Wang, B. Mu, H. Y. Lin and G. C. Liu, J. Organomet. 26 (a) Y. Y. Deng, F. Q. Liu and Y. L. Jin, Transition Met. Chem.,
Chem., 2011, 696, 2313; (b) X. L. Wang, B. Mu, H. Y. Lin,
G. C. Liu, A. X. Tian and S. Yang, CrystEngComm, 2012, 14,
1001; (c) X. L. Wang, H. Y. Lin, B. Mu, A. X. Tian, G. C. Liu
2012, 37, 309; (b) S. Hazra, S. Majumder, M. Fleck,
N. Aliaga-Alcalde and S. Mohanta, Polyhedron, 2009, 28,
3707.
and N. H. Hu, CrystEngComm, 2011, 13, 1990; 27 (a) E. H. Kim, D. I. Kim, H. S. Lee, J. C. Byun, J. H. Choi
(d) X. L. Wang, B. Mu, H. Y. Lin, S. Yang, G. C. Liu,
A. X. Tian and J. W. Zhang, Dalton Trans., 2012, 41, 11074.
16 (a) S. Muthu, J. K. Yip and J. Vittal, J. Chem. Soc., Dalton
and Y. C. Park, Polyhedron, 2007, 26, 85; (b) X. L. Wang,
H. Y. Zhao, H. Y. Lin, G. C. Liu, J. N. Fang and B. K. Chen,
Electroanalysis, 2008, 20, 1055.
Trans., 2001, 3577; (b) M. Sarkar and K. Biradha, Chem. 28 (a) P. P. Sahoo, S. Sumithra, G. Madras and T. G. Row,
Commun., 2005, 2229; (c) Y. Liang, F. K. Zhao, Q. L. Wang
and Y. Y. Niu, J. Chem. Crystallogr., 2011, 41, 763.
17 (a) L. Rajput and K. Biradha, Polyhedron, 2008, 27, 1248;
Inorg. Chem., 2011, 50, 8774; (b) Y. H. Guo, C. W. Hu,
X. L. Wang, Y. H. Wang and E. B. Wang, Chem. Mater.,
2001, 13, 4058.
(b) X. L. Wang, J. Luan, Q. L. Lu, H. Y. Lin and C. Xu, 29 (a) S. Zhou, Z. G. Kong, Q. W. Wang and C. B. Li, Inorg.
J. Organomet. Chem., 2012, 719, 1.
18 Y. J. Cui, Y. F. Yue, G. D. Qian and B. L. Chen, Chem. Rev.,
2012, 112, 1126.
Chem. Commun., 2012, 25, 1; (b) Y. Q. Chen, S. J. Liu,
Y. W. Li, G. R. Li, K. H. He, Y. K. Qu, T. L. Hu and X. H. Bu,
Cryst. Growth Des., 2012, 12, 5426.
19 (a) Y. Gong, T. Wu, J. H. Lin and B. S. Wang, CrystEng- 30 J. Guo, J. Yang, Y. Y. Liu and J. F. Ma, CrystEngComm, 2012,
Comm, 2012, 14, 5649; (b) Y. Bai, G. J. He, Y. G. Zhao, 14, 6609.
C. Y. Duan, D. B. Dang and Q. J. Meng, Chem. Commun., 31 H. X. Yang, T. F. Liu, M. N. Cao, H. F. Li, S. Y. Gao and
2006, 1530; (c) J. P. Zou, Q. Peng, Z. Wen, G. S. Zeng, R. Cao, Chem. Commun., 2010, 46, 2429.
Q. J. Xing and G. C. Guo, Cryst. Growth Des., 2010, 10, 2613. 32 (a) S. Muthu, J. K. Yip and J. J. Vittal, J. Chem. Soc., Dalton
20 (a) S. Q. Zang, Y. Su, Y. Z. Li, Z. P. Ni and Q. J. Meng, Inorg.
Chem., 2006, 45, 174; (b) S. S. Chen, Y. Zhao, J. Fan,
Trans., 2002, 4561; (b) S. Muthu, J. K. Yip and J. J. Vittal,
J. Chem. Soc., Dalton Trans., 2001, 3577.
T. A. Okamura, Z. S. Bai, Z. H. Chen and W. Y. Sun, Cryst- 33 F. A. Schultz and T. Kuwana, J. Electroanal. Chem., 1965, 10,
EngComm, 2012, 14, 3564. 95.
21 (a) J. X. Xu, R. Y. Wang, Y. M. Li, Z. Y. Gao, R. Yao, S. Wang 34 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystal-
and B. L. Wu, Eur. J. Inorg. Chem., 2012, 20, 3349;
logr., 2008, 64, 112.
8386 | Dalton Trans., 2013, 42, 8375–8386
This journal is © The Royal Society of Chemistry 2013