The dimeric and two-dimensional copper(II) complexes constructed from salicylic acid and 4,4′-bipyridine

Article abstract of DOI:10.1016/S1387-7003(03)00173-4

Two novel complexes, [Cu₂(Hsal)₄(4,4′-bipyridine)(H₂ O)₂(DMF)₂] (1) (H₂sal=salicylic acid) and {([Cu(Hsal)₂(4,4′-bipyridine)](H₂O) (H₂sal)}_n (2), were synthesized by layered-solution method and structurally characterized. Geometries of copper atoms in both complexes exhibit square pyramidal. Complex 1 is a dimer and hydrogen bonds between water and DMF molecules extend the structure into 1D hydrogen bonding network. Complex 2 consists of two-dimensional square framework structure.

Full text of DOI:10.1016/S1387-7003(03)00173-4

Inorganic Chemistry Communications 6 (2003) 1051–1055
www.elsevier.com/locate/inoche
The dimeric and two-dimensional copper(II) complexes
constructed from salicylic acid and 4,40-bipyridine
a,
b
Long-Guan Zhu *, Susumu Kitagawa
a
Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou 310027, PR China
b
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Yoshida,
Sakyo-ku, Kyoto 606-8501, Japan
Received 18 April 2003; accepted 11 May 2003
Published online: 16 June 2003
Abstract
Two novel complexes, [Cu2(Hsal)4(4,40-bipyridine)(H2O)2(DMF)2] (1) (H2sal ¼ salicylic acid) and {[Cu(Hsal)2(4,40-bipyri-
dine)](H2O)(H2sal)}n (2), were synthesized by layered-solution method and structurally characterized. Geometries of copper atoms
in both complexes exhibit square pyramidal. Complex 1 is a dimer and hydrogen bonds between water and DMF molecules extend
the structure into 1D hydrogen bonding network. Complex 2 consists of two-dimensional square framework structure.
Ó 2003 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structure; Copper complex; Salicylic acid; 4,40-Bipyridine; Dimer; Network
1. Introduction
tained and show dimeric and two-dimensional (2D)
networks, respectively, namely [Cu2(Hsal)4(4,40-bipy)
(H2O)2(DMF)2] (1) and {[Cu(Hsal)2(4,40-bipy)](H2O)
(H2sal)}n (2).
In numerous works dealing with coordination poly-
mers, 4,40-bipyridine (4,40-bipy) has been extensively
used in the construction of framework structures [1,2].
Many kinds of frameworks have been widely con-
structed by this ligand, for example, ladder, zig-zag,
diamond, railroad, brick wall, hexagonal grid and
square grid [3–7]. Moreover the coordination modes of
4,40-bipyridine have been very attractive, such as
monodentate [8,9], singly hydrogen bonding [10], doubly
hydrogen bonding [11] and protonated ligands [12]. We
combined salicylic acid (H2sal), which is of current in-
terest in both structural and biological viewpoints, with
4,40-bipyridine to synthesize three one-dimensional (1D)
complexes [13], {trans-[Cu(Hsal)2(4,40-bipy)](DMF)}n,
{cis-[Cu(Hsal)2(4,40-bipy)](2H2O)}n, and [Cu2(Hsal)4
(4,40-bipy)]n. Recently, two novel complexes based on
same building blocks (H2sal and 4,40-bipy) were ob-
2. Experimental
2.1. Synthesis
2.1.1. Preparation of complex 1
Crystals were grown by layer method using three-layer
solution in a slender tube with a 0.8 cm diameter. The
bottom layer was 4 ml water containing 0.05 mol/l
Cu(CH3COO)2 Á H2O, the middle layer was 4 ml DMF
solution containing 0.05 mol/l pyrazine and 0.2 mol/l
salicylic acid (H2sal) and the upper layer was 4 ml meth-
anol containing 0.05 mol/l 4,40-bipyridine. After some
days later sky-blue needle crystals were obtained. Anal.
Calcd for CuC22N2O8H23, C, 52.12, N, 5.53, H, 4.57%.
Found: C, 51.99, N, 5.57, H, 4.44%. IR (KBr, cmÀ1):
1655(s), 1649(s), 1613(m), 1598(m), 1483(s), 1449(s),
1414(m), 1389(s), 1364(s), 1248(s), 1145(w), 1029(w),
823(w), 754(m), 670(m), 645(w), 589(w), 497(w).
* Corresponding author. Tel.: +8657187963867; fax: +865718795
1895.
E-mail address: chezlg@zju.edu.cn (L.-G. Zhu).
1387-7003/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(03)00173-4

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L.-G. Zhu, S. Kitagawa / Inorganic Chemistry Communications 6 (2003) 1051–1055
Table 1
Crystallographic data for 1 and 2
2.1.2. Preparation of complex 2
The synthesis was carried out using the same proce-
dure as in 1. The upper layer was 7 ml methanol con-
taining 0.05 mol/l 4,40-bipyridine, the bottom layer was 7
ml water solution containing 0.05 mol/l Cu(CH3COO)2 Á
H2O and the middle layer was 4 ml mixture solution of
water and methanol (ratio of methanol/water was 1:1)
containing 0.05 mol/l pyrazine and 0.2 mol/l H2sal. Af-
ter some days later crystals were obtained. Anal. Calcd
for CuC31O10N2H26: C, 57.27, N, 4.31, H, 4.03%.
Found: C, 57.04, N, 4.31, H, 3.97%. IR (KBr pellet,
cmÀ1): 1611(s), 1590(s), 1571(m), 1561(m), 1485(s),
1449(s), 1393(s), 1300(m), 1254(s), 1223(m), 1158(m),
866(m), 815(m), 757(s), 700(w), 670(m), 645(w), 531(w),
504(w), 425(w).
Crystal parameter
Compound 1
Compound 2
Empirical formula
Formula weight
Color/habit
CuC22N2O8H23
506.98
Sky blue/needle
CuC31O10N2H26
650.10
Deep blue/brick
Size (mm  mm  mm)
Crystal system
Space group
0.10 Â 0.15 Â 0.80 0.50 Â 0.15 Â 0.05
Triclinic
P-1(#2)
Triclinic
P-1(#2)
Unit cell dimensions
ꢀ
a (A)
ꢀ
7.6287(8)
11.974(2)
12.731(1)
101.078(4)
95.677(1)
97.156(1)
1123.3(3)
2
7.2491(8)
11.113(1)
19.572(2)
93.847(6)
100.202(3)
97.277(5)
1532.8(3)
2
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
3
ꢀ
V (A )
Z
Dc (g cmÀ3
)
1.499
1.023
1.408
0.772
2.2. Crystallography
l(Mo-KaÞ (mmÀ1
)
F ð000Þ
524
8419
670
10501
Data were collected on a Rigaku Mercury CCD dif-
fractometer with graphite-monochromated Mo-Ka ra-
Reflections collected
Independent reflections
4835 (Rint ¼ 0:021) 6302 (Rint ¼ 0:032)
ꢀ
R
0.036
0.044
0.054
0.067
diation (k ¼ 0:71069 A). Structures were solved by
Rw
Largest difference peak
ꢀ
and hole (e A
direct methods and refined by least-squares procedures
on F 2. The H atoms attached to water molecules were
found by difference Fourier syntheses. Other H atoms
were geometrically fixed and were allowed to ride on
0.48, )0.41
0.72, )0.74
À3
)
atoms to which they are attached. The same isotropic
thermal parameter was used for all H atoms and refined.
The weighting schemes were based on counting statis-
tics. All calculations were performed with the help of
Texsan programs. The drawings of the molecules were
realized with the help of ORTEP-3 for Windows [14].
Details of data collections and refinements are given in
Table 1.
3. Results and discussion
3.1. Synthesis
Two complexes were separated from solutions con-
taining pyrazine weak base. Many efforts to obtain new
complexes without pyrazine have led to three 1D com-
plexes reported before except 1 and 2 [13]. The dimeric
complex is very stable in solution even kept over 3
months. In the synthetic procedure of complex 1, at least
three compounds were obtained, one was [Cu2(pyz)
(sal)2(MeOH)2]n and well established in our lab [15], and
other two were blue crystals, which were easily separated
them from their shapes and colors because one (complex
1) is sky-blue needle crystals, and another (complex 3) is
crisp blue brick crystals. It is very difficult to collect data
for complex 3. In the synthetic procedure of complex 2,
similar phenomenon was observed and several com-
plexes could be obtained. While deep blue brick crystals
were different from those well characterized before.
Thus complex 2 was separated.
Fig. 1. An ORTEP view of the dimeric structure of complex 1.

L.-G. Zhu, S. Kitagawa / Inorganic Chemistry Communications 6 (2003) 1051–1055
1053
Synthetic environments in both synthetic procedures
of complexes 1 and 2 were only different in solvents of
middle layers. Therefore DMF is key to formation of
the dimer compared with complex 2. It is suggested that
the energy barrier for conversion between complexes 1
and 2 is small.
bonding network could be constructed (see Fig. 2).
Recently some dimeric complexes with 4,40-bipyridine
ligand were reported, but it is still relatively limited and
kept unknown for formation mechanism. Comparing
with other dimeric complexes with 4,40-bipyridine linker,
complex 1 shows similar bond lengths associated with
M–N distances [9,16,17].
3.2. Structural description
3.2.2. Description of complex 2
3.2.1. Description of complex 1
An ORTEP view of the structure for 2 is shown in
Fig. 3 and selected bond lengths and angles are listed in
Table 3. The geometry around copper(II) has five-co-
ordinate and involves two nitrogen atoms from two 4,40-
An ORTEP view of the structure for 1 is shown in
Fig. 1 and selected bond lengths and angles are listed in
Table 2. Complex 1 consists of a dimer associated five-
coordinate Cu(II) centers (separation of Cu Á Á Á 4,40-bi-
ꢀ
py Á Á Á Cu is 11.050 A) in a square pyramidal CuNO4
chromophore, the basal plane being formed by one ni-
trogen atom of 4,40-bipyridine, two oxygen atoms of two
deprotonated HsalÀ ligands, and one water molecule.
The coordination of copper center is completed by one
large apical copper–oxygen atom distance from
monodentate terminal of DMF. The conformation of
two rings of 4,40-bipyridine is co-planar. The bond
lengths and angles in the salicylate anions are in the
normal range. The water molecule forms hydrogen bond
with DMF of neighboring dimer, thus 1D hydrogen
Fig. 2. 1D hydrogen bonding network of complex 1.
Fig. 3. An ORTEP view of the crystal structure of complex 2.
Table 2
ꢀ
Selected bond lengths (A) and bond angles (°) for 1
Bond lengths
Cu(1)–O(1)
Cu(1)–O(7)
Cu(1)–N(1)
C(1)–O(2)
1.966(2)
1.974(2)
2.007(2)
1.254(3)
1.349(4)
1.457(6)
1.447(4)
1.252(3)
1.349(4)
1.342(4)
1.397(4)
1.379(4)
Cu(1)–O(4)
Cu(1)–O(8)
C(1)–O(1)
C(1)–C(2)
1.960(2)
2.290(2)
1.269(3)
1.484(4)
1.226(3)
1.312(3)
1.272(3)
1.493(4)
1.336(3)
1.368(4)
1.368(4)
C(3)–O(3)
C(20)–O(8)
N(2)–C(20)
C(8)–O(4)
C(8)–C(9)
N(2)–C(21)
N(2)–C(22)
C(8)–O(5)
C(10)–O(6)
N(1)–C(19)
C(16)–C(17)
C(18)–C(17)
N(1)–C(15)
C(15)–C(16)
C(19)–C(18)
Bond angles
O(1)–Cu(1)–O(4)
O(1)–Cu(1)–O(8)
O(4)–Cu(1)–O(7)
O(4)–Cu(1)–N(1)
O(7)–Cu(1)–N(1)
165.95(6)
89.67(6)
89.75(9)
89.79(8)
172.70(7)
O(1)–Cu(1)–O(7)
O(1)–Cu(1)–N(1)
O(4)–Cu(1)–O(8)
O(7)–Cu(1)–O(8)
O(8)–Cu(1)–N(1)
87.05(9)
91.66(8)
104.26(7)
95.71(7)
91.46(7)

1054
L.-G. Zhu, S. Kitagawa / Inorganic Chemistry Communications 6 (2003) 1051–1055
Table 3
Table 4
Bond lengths of Cu–O and Cu–N in complex 2 and reported one
ꢀ
Selected bonths (A) and bond angles (°) for complex 2
[Cu(Hsal)2(4,40-bipy)]
Bond lengths
Bond length
[Cu(Hsal)2(py)2]
Cu(1)–O(1)
Cu(1)–O(4)
Cu(1)–N(2)
C(1)–O(2)
1.948(3)
1.940(3)
2.020(3)
1.264(5)
1.350(5)
1.257(6)
1.352(10)
1.342(5)
1.391(6)
1.378(5)
1.334(6)
1.381(6)
1.395(5)
Cu(1)–O(3*)
Cu(1)–N(1)
C(1)–O(1)
2.363(3)
2.019(3)
1.273(5)
1.480(5)
1.267(6)
1.479(6)
1.332(6)
1.382(6)
1.362(6)
1.346(6)
1.391(6)
1.377(6)
Cu(1)–O(1)
Cu(1)–O(4)
Cu(1)–O(3)
Cu(1)–N(2)
Cu(1)–N(1)
1.967(1)
1.974(2)
2.503(2)y
2.040(2)
2.024(2)
1.948(3)
1.940(3)
2.363(3)
2.020(3)
2.019(3)
C(1)–C(2)
C(8)–O(4)
C(8)–C(9)
C(3)–O(3)
C(8)–O(5)
Symmetry code: y, 1 þ x, y, z.
C(10)–O(6)
N(1)–C(19)
C(16)–C(17)
C(18)–C(19)
N(2)–C(24)
C(21)–C(22)
C(23)–C(24)
N(1)–C(15)
C(15)–C(16)
C(17)–C(18)
N(2)–C(20)
C(20)–C(21)
C(22)–C(23)
1D linear network. Therefore the combination of
[Cu(Hsal)2] motifs and 4,40-bipyridine ligands leads to a
2D network (see Fig. 4). The free salicylic acid forms
hydrogen bonding with water molecule, and two com-
ponents further form hydrogen bonds with coordinated
HsalÀ ligands. The dihedral angle of two rings of 4,40-
bipyridine is 44.89 °. Separations of Cu Á Á Á Cu in the
Bond angles
O(1)–Cu(1)–O(3*) 95.9(1)
O(1)–Cu(1)–N(1) 90.4(1)
O(1)–Cu(1)–O(4)
O(1)–Cu(1)–N(2)
O(3*)–Cu(1)–N(1)
O(4)–Cu(1)–N(1)
N(1)–Cu(1)–N(2)
174.6(1)
88.2(1)
89.9(1)
92.4(1)
177.3(1)
O(3*)–Cu(1)–O(4) 79.4(1)
O(3*)–Cu(1)–N(2) 92.5(1)
network of complex
2
for Cu Á Á Á bipy Á Á Á Cu and
ꢀ
Cu Á Á Á Hsal Á Á Á Cu are 11.113 and 7.249 A, respectively.
Two salicylates have different coordination modes; one
is monodentate while another bears a novel bind mode,
which serves as a bridging ligand.
O(4)–Cu(1)–N(2)
89.2(1)
Symmetry code: *, À1 þ x, y, Àz.
bipyridine ligands and three oxygen atoms from two
HsalÀ ligands. The atoms O(1), N(1), N(2) and O(4) are
sitting in a basal plane while oxygen O(3*) is in apical
position. Two HsalÀ ligands are arranged as pincerlike
pattern around copper atom, which is similar to the
extended structure of [Cu(Hsal)2]n in [Cu(Hsal)2(py)2]n
complex [18]. While in the case of 4,40-bipyridine, the
structure is more compact than that of [Cu(Hsal)2(py)2]n
(see Table 4). Because of the bridging property of l-
HsalÀ, the motifs of [Cu(Hsal)2] in 2 were extended into
Supplementary data
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been de-
posited with the Cambridge Crystallographic Data
Center as supplementary publication Nos., CCDC-
208749 and CCDC-208750 for complexes 1 and 2.
Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB2,
1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk).
Acknowledgements
The financial support from the National Natural
Science Foundation of China (No. 50073019) (to L.G.
Zhu) is gratefully acknowledged.
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