Synthesis, structural characterization and substituent effects of two copper(II) complexes with benzaldehyde ortho-oxime ligands

Article abstract of DOI:10.1007/s11243-012-9585-4

Two new Cu(II) complexes, [Cu(L¹)₂] (1) and [Cu(L²)₂] (2) (HL¹ = (E)-3-bromo-5-chloro-2- hydroxy benzaldehyde O-methyl oxime; HL² = (E)-3-bromo-5- chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analyses show that complexes 1 and 2 have similar structures, consisting of one Cu(II) atom and two L- units. In both complexes, the Cu(II) atom, lying on an inversion center, is four-coordinated in a trans-CuN ₂O₂ square-planar geometry by two phenolate O and two oxime N atoms from two symmetry-related N,O-bidentate oxime ligands. Moreover, both complexes form an infinite three-dimensional supramolecular structure involving intermolecular C-H...Br hydrogen bonds and π...π stacking interactions between the metal chelate rings and aromatic rings. Substituent effects in the two complexes are discussed. Springer Science+Business Media B.V. 2012.

Full text of DOI:10.1007/s11243-012-9585-4

Transition Met Chem (2012) 37:271–277
DOI 10.1007/s11243-012-9585-4
Synthesis, structural characterization and substituent effects
of two copper(II) complexes with benzaldehyde ortho-oxime
ligands
•
Wen-Kui Dong Gang Wang Shang-Sheng Gong
•
•
•
Jun-Feng Tong Yin-Xia Sun Xiong-Hou Gao
•
Received: 31 December 2011 / Accepted: 30 January 2012 / Published online: 22 February 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Two new Cu(II) complexes, [Cu(L1)2] (1) and
[Cu(L2)2] (2) (HL1 = (E)-3-bromo-5-chloro-2-hydroxy
benzaldehyde O-methyl oxime; HL2 = (E)-3-bromo-5-
chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been
synthesized and characterized by physicochemical and
spectroscopic methods. X-ray crystallographic analyses
show that complexes 1 and 2 have similar structures,
consisting of one Cu(II) atom and two L- units. In both
complexes, the Cu(II) atom, lying on an inversion center, is
four-coordinated in a trans-CuN2O2 square-planar geome-
try by two phenolate O and two oxime N atoms from two
symmetry-related N,O-bidentate oxime ligands. Moreover,
both complexes form an infinite three-dimensional supra-
molecular structure involving intermolecular C–HÁÁÁBr
hydrogen bonds and pÁÁÁp stacking interactions between the
metal chelate rings and aromatic rings. Substituent effects
in the two complexes are discussed.
salicylaldehyde and various amines have been used to
synthesize many complexes of copper(II) and nickel(II)
[1, 2]. In recent years, there has been enhanced interest in
the synthesis and characterization of such complexes due to
their interesting properties [3–5], and they have been
increasingly used in analytical chemistry [6], supramolec-
ular chemistry [7–9], extraction metallurgy [10], medicine
[11], insecticide [12], anti-virus [13] and other applica-
tions. Herein, two new Cu(II) complexes with mono-oxime
ligands, [Cu(L1)2] (1) (HL1 = (E)-3-bromo-5-dichoro-2-
hydroxy benzaldehyde O-methyl oxime) and [Cu(L2)2] (2)
(HL2 = (E)-3-bromo-5-dichoro-2-hydroxy benzaldehyde
O-ethyl oxime), have been synthesized and characterized
by elemental analyses, IR spectra and UV–Vis spectra. In
addition, X-ray crystallographic analyses reveal that the
structures of complexes 1 and 2 are very similar. They are
both mononuclear, and all the Cu(II) atoms are four-
coordinated. However, the bond distances and angles vary
due to the different substituents in the ligands.
Introduction
Oximes have long been used as chelating ligands in the
synthesis of transition metal complexes due to their ease of
preparation and structural variety. Those derived from
Experimental
Methoxyamine and ethoxyamine were purchased from Alfa
Aesar and used without further purification. 3-Bromo-5-
chloro-2-hydroxybenzaldehyde and the other reagents and
solvents were analytical grade from Tianjin Chemical
Reagent Factory. Elemental analyses for Cu were obtained
using an IRIS ER/SÁWP-1 ICP atomic emission spectrome-
ter. C, H and N analyses were obtained using a GmbH
VarioEL V3.00 automatic elemental analysis instrument. IR
spectra were recorded on a VERTEX70 FTIR spectropho-
tometer, with samples prepared as KBr (500–4000 cm-1) or
CsI (100-500 cm-1) pellets. UV–Vis absorption spectra
were recorded on a Shimadzu UV-2550 spectrometer. X-ray
W.-K. Dong (&) Á G. Wang Á S.-S. Gong Á J.-F. Tong Á
Y.-X. Sun
School of Chemical and Biological Engineering,
Lanzhou Jiaotong University, Lanzhou 730070,
People’s Republic of China
e-mail: dongwk@126.com
X.-H. Gao
Lanzhou Petrochemical Research Center, PetroChina,
Lanzhou 730060, People’s Republic of China
123

272
Transition Met Chem (2012) 37:271–277
Crystal structure determinations
single-crystal structures determinations were carried out on a
Bruker Smart APEX CCD diffractometer.
Single crystals of complexes 1 and 2 with approximate
dimensions of 0.38 9 0.12 9 0.06 mm and 0.21 9 0.18 9
0.07 mm were mounted on a Bruker Smart 1000 CCD area
detector. The diffraction data were collected using graphite
monochromated Mo Ka radiation (k = 0.071073 nm) at
298(2) K. The LP factor and semi-empirical absorption
corrections were applied to the intensity data. The struc-
tures were solved using the program SHELXS-97 [14] and
refined by full-matrix least-squares methods on F2 using
SHELXL-97 [14]. The non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were added theoretically.
Details of the data collection and refinements of complexes
1 and 2 are given in Table 1.
Synthesis of HL1
To
a stirred solution of 3-bromo-5-chloro-2-hydro-
xybenzaldehyde (0.2355 g, 1 mmol) in hot EtOH (5 ml)
was added an EtOH (3 ml) solution of methoxyamine
(0.0835 g, 1 mmol). After stirring the reaction mixture at
338 K for 10 h, the solvent was removed under reduced
pressure and the residue was recrystallized from ethanol to
give the title compound. Yield 0.138 g (52%). mp.
362–365 K. Anal. Calcd for C8H7BrClNO2: C, 36.3; H,
2.7; N, 5.3. Found: C, 36.4; H, 2.6; N, 5.2.
Synthesis of HL2
Results and discussion
To
a stirred solution of 3-bromo-5-chloro-2-hydro-
xybenzaldehyde (0.2355 g, 1 mmol) in hot EtOH (4 ml) was
added an EtOH solution (3 ml) of ethoxyamine (0.0976 g,
1 mmol). After stirring the reaction mixture at 338 K for
10 h, the solvent was removed under reduced pressure and
the residue was recrystallized from ethanol to give the title
compound. Yield 0.156 g (56%). mp. 340–341 K. Anal.
Calcd for C9H9BrClNO2: C, 38.8; H, 3.3; N, 5.0. Found: C,
38.9; H, 3.5; N, 4.9.
The most important FTIR bands for HL1, HL2 and com-
plexes 1 and 2 are given in Table 2. The O–H stretching
frequency of oxime-type ligands is generally expected in
the 3300–3800 cm-1 region; the bands for HL1 and HL2
are observed at 3420 cm-1 and 3411 cm-1, respectively,
due to the internal hydrogen bond OHÁÁÁN=C [15]. The free
ligands HL1 and HL2 exhibit characteristic C=N stretching
frequencies at 1608 and 1602 cm-1, while the C=N
stretching frequencies of complexes 1 and 2 were both
observed at 1606 cm-1. Hence, the C=N stretching fre-
quencies are slightly shifted upon complexation [16–18].
The Ar–O stretching frequency occurs at 1213 cm-1 for
HL1, and at 1219 cm-1 for complex 1; this band occurs at
1221 cm-1 for HL2 and at 1211 cm-1 for complex 2.
Hence, the Ar–O stretching frequency is shifted by ca.
7 cm-1 and 9 cm-1, respectively.
Synthesis of complex 1
A solution of copper(II) acetate monohydrate (0.0022 g,
0.01 mmol) in MeOH (3 ml) was added dropwise to a
solution of HL1 (0.0028 g, 0.01 mmol) in dichloromethane
(5 ml) at room temperature. The color of the mixture turned
pale yellow immediately. Upon standing at room tempera-
ture for 2 weeks, the solvent partially evaporated and yellow
prismatic single crystals suitable for X-ray crystallographic
analysis were obtained. Yield 0.0021 g (35%). Anal. Calcd
for C16H12Br2Cl2CuN2O4 (%): C, 32.5; H, 2.1; N, 4.7; Cu,
10.8. Found: C, 32.6; H, 2.1; N,4.6; Cu, 10.9.
The far-infrared spectra of complexes 1 and 2 were also
obtained in the region 500–100 cm-1 in order to observe the
Cu–O and Cu–N stretching frequencies. The FTIR spectrum
of complex 1 showed the m(Cu–N) and m(Cu–O) absorption
frequencies at 459 cm-1 and 420 cm-1 (469 cm-1 and
421 cm-1 for complex 2) [19], respectively. These assign-
ments are consistent with the literature [20–23].
Synthesis of complex 2
The UV–Vis absorption spectra of the free ligands HL1,
HL2 and their corresponding Cu(II) complexes were
determined in 5 9 10-5 mol L-1 DMF solution. The
absorption spectrum of HL1 shows a peak at 317 nm
assigned to a p–p* transition, while equivalent band is
observed at 315 nm in the spectrum of complex 1. The
absorption spectrum of HL2 shows a peak at 315 nm
assigned to a p–p* transition [24, 25], while the equivalent
peak is at 319 nm in the spectrum of complex 2. Hence, the
shift upon complexation is hypsochromic in complex 1 and
bathochromic in complex 2, perhaps due to the different
A solution of copper(II) acetate monohydrate (0.0034 g,
0.02 mmol) in MeOH (3 ml) was added dropwise to a
solution of HL2 (0.0047 g, 0.02 mmol) in dichloromethane
(3 ml) at room temperature. The color of the mixture
turned pale yellow immediately. Upon standing at room
temperature for 2 weeks, the solvent partially evaporated
and yellow prismatic single crystals suitable for X-ray
crystallographic analysis were obtained. Yield 0.0031 g
(27%). Anal. Calcd. for C18H16Br2Cl2CuN2O4 (%): C,
35.0; H, 2.6; N, 4.5; Cu, 10.3. Found: C, 34.9; H, 2.7; N,
4.4; Cu, 10.4.
123

Transition Met Chem (2012) 37:271–277
273
Table 1 Crystal data and
structure refinement parameters
for complexes 1 and 2
Compounds
Complex 1
Complex 2
Empirical formula
Formula weight
Temperature (K)
C16H12Br2Cl2CuN2O4
590.54
C18H16Br2Cl2CuN2O4
618.59
298(2)
298(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal system, space group
Monoclinic, P21/c
Triclinic, P-1
˚
Unit cell dimensions (A, 8)
a
b
c
a
b
c
4.0174(5)
8.017(1)
13.820(1)
8.058(1)
17.321(2)
8.837(1)
90
106.067(2)
100.989(1)
100.165(1)
522.4(1)
92.509(1)
90
3
˚
Volume (A )
960.8(2)
Z, Calculated density (Mg/m3)
2, 2.041
1, 1.966
Absorption coefficient (mm-1
F(000)
)
5.599
5.153
574
303
Crystal size (mm)
0.38 9 0.12 9 0.06
1.89–25.01
-4,4/-16,16/-20,14
4547/1669 [Rint = 0.0441]
98.8% (h = 25.01)
0.2190.1890.07
2.48–25.02
-7,9/-9,7/-10, 10
2693/1817 [Rint = 0.0190]
98.1% (h = 25.02)
h range for data collection (8)
Limiting indices
Reflections collected/unique
Completeness to h
Absorption correction
Max. and min. transmission
Refinement method
Semi-empirical from equivalents Semi-empirical from equivalents
0.7299 and 0.2248
Full-matrix least-squares on F2
1669/0/125
0.7143 and 0.4108
Full-matrix least-squares
1817/0/134
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I[2r(I)]
R indices (all data)
1.113
1.006
a
R1 = 0.0624, wR2 = 0.1496a
R1 = 0.0736, wR2 = 0.1544
1.294 and -0.850
R1 = 0.0326, wR2 = 0.0736b
R1 = 0.0469, wR2 = 0.0789
0.434 and -0.414
w = 1/
[r2(F2o)?(0.0689P)2?5.0095P]
b
w = 1/[r2(F2o)?(0.0395P)2],
Largest diff. peak and hole (e.A-3
)
where P = (F2o?2Fc2)/3
space group, whereas complex 2 crystallizes in the triclinic
system and P-1 space group. Both the compounds can be
described as centrosymmetric mononuclear Cu(II) com-
plexes, in which the Cu(II) center, lying on the inversion
center, is four-coordinated in a trans-CuN2O2 square-planar
geometry, with two phenolate O and two oxime N atoms
from two N,O-bidentate oxime (L1)- or (L2)- ligands.
As shown in Fig. 3, the crystal structure of complex 1 is
stabilized by intermolecular C1-H1CÁÁÁBr1 hydrogen bonds
(Table 5) with a graph-motif R22 [18], which link neigh-
bouring molecules into extended chains, forming an infinite
three-dimensional supramolecular network. Meanwhile,
intermolecular C8-H8ÁÁÁBr1 hydrogen bonds and pÁÁÁp
stacking interactions between the metal chelate ring and
aromatic ring provide further stabilization (Fig. 4 and
Table 6). In Figs. 5 and 6, in complex 2, there exist
intermolecular C7-H7ÁÁÁBr1 and C3-H3ÁÁÁO1 hydrogen
bonds both with graph-motifs R22 [8] (Table 5) and pÁÁÁp
stacking interactions (Table 6), forming an infinite three-
dimensional supramolecular structure [26–29].
Table 2 Main IR bands for the ligands and their complexes (cm-1
)
Compounds
m(O–H)
m(C=N)
m(Ar–O)
m(Cu–N)
m(Cu–O)
HL1
3420
–
1608
1606
1602
1606
1213
1219
1221
1211
–
–
Complex 1
HL2
459
–
420
–
3411
–
Complex 2
469
421
substituent effects. In addition, a new peak was observed at
377 or 371 nm in the absorption spectra of complexes 1
and 2, respectively.
Description of the crystal structures
ORTEP representations of complexes 1 and 2 are shown in
Figs. 1 and 2. Selected bond distances and angles are given
in Tables 3 and 4.
X-ray crystal structure determination reveals that com-
plex 1 crystallizes in the monoclinic system and P21/c
123

274
Transition Met Chem (2012) 37:271–277
Symmetry codes: (I) -1?X, Y, Z; (II) 2-X, 1-Y, 1-Z.
DCC = distance between ring centroids; a = dihedral
angle between planes I and J; b = Angle Cg(I)ÁÁÁCg(J) vec-
tor and normal to plane I. Cg(I)-perp = perpendicular dis-
tance of Cg(I) from ring J; Cg(J)-perp = perpendicular
distance of Cg(J) from ring I. Cg1 and Cg3 for complex 1 are
the centroids of atoms Cu1\O2\C4\C3\C2\N1 and C3–C8,
respectively; Cg1 and Cg3 for complex 2 are the centroids of
atoms Cu1\O2\C5\C4\C3\N1 and C4–C9, respectively.
Substituent effects
Fig. 1 ORTEP view of the crystal structure of complex 1 with
thermal ellipsoids drawn at the 30% probability level. Hydrogen
atoms have been omitted for clarity
The overall structures of the two complexes are found to be
identical except that the oxime portion differs by a single –
CH2– group. In both cases, two imino N and two phenolic
O atoms form a square plane around copper, with the Cu–N
bonds being slightly longer than the corresponding Cu–O
bonds. The elongation of the Cu–N bonds probably due to
the weakening of the coordination abilities of the nitrogen
atoms by the larger electronegativity of oxime oxygen
atoms. Similar elongation has been observed in Cu(II)
complexes with Salen-type ligands [30, 31]. However, due
to the presence of an extra –CH2– group in the HL2 ligand,
˚
the Cu–N bond (2.010 A) of complex 1 is longer than that
˚
Cu–N (1.992 A) of complex 2, and the Cu–O bond (1.913
˚
˚
A) of complex 1 is also longer than that Cu–O (1.878 A) of
complex 2. Meanwhile, the angle N1–Cu1–O2 (89.62°) in
complex 1 is smaller than equivalent angle (90.02°) in
complex 2. The substituent effects also give rise to the
variations in IR and UV–Vis spectra in complexes 1 and 2.
Fig. 2 ORTEP view of the crystal structure of complex 2 with
thermal ellipsoids drawn at the 30% probability level. Hydrogen
atoms have been omitted for clarity
˚
Table 3 Selected bond lengths (A) and bond angles (°) for complex 1
Bond distances
Cu(1)–O(2)#1
Cu(1)–O(2)
Cu(1)–N(1)
Cu(1)–N(1)#1
Br(1)–C(5)
Cl(1)–C(7)
1.914(5)
1.914(5)
2.01(6)
N(1)–C(2)
N(1)–O(1)
O(1)–C(1)
O(2)–C(4)
C(2)–C(3)
C(3)–C(8)
1.273(1)
1.429(8)
1.431(1)
1.305(9)
1.453(1)
1.418(1)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
1.424(1)
1.404(1)
1.391(1)
1.377(1)
1.37(1)
2.01(6)
1.899(8)
1.764(8)
Bond angles
O(2)–Cu(1)–O(2)#1
O(2)–Cu(1)–N(1)
O(2)#1–Cu(1)–N(1)
O(2)–Cu(1)–N(1)#1
O(2)#1–Cu(1)–N(1)#1
N(1)–Cu(1)–N(1)#1
C(2)–N(1)–O(1)
180.000
N(1)–O(1)–C(1)
C(4)–O(2)–Cu(1)
N(1)–C(2)–C(3)
C(8)–C(3)–C(4)
C(8)–C(3)–C(2)
C(4)–C(3)–C(2)
O(2)–C(4)–C(5)
O(2)–C(4)–C(3)
C(5)–C(4)–C(3)
109.5(6)
131.7(5)
125.4(7)
120.9(7)
116.7(7)
122.4(7)
121.3(7)
123.1(6)
115.5(7)
C(6)–C(5)–C(4)
C(6)–C(5)–Br(1)
C(4)–C(5)–Br(1)
C(7)–C(6)–C(5)
C(8)–C(7)–C(6)
C(8)–C(7)–Cl(1)
C(6)–C(7)–Cl(1)
C(7)–C(8)–C(3)
123.4(7)
117.9(6)
118.7(6)
119.1(7)
121.0(8)
119.5(6)
119.5(6)
119.9(7)
89.6(2)
90.4(2)
90.4(2)
89.6(2)
180.000
111.2(6)
127.6(5)
121.1(5)
C(2)–N(1)–Cu(1)
O(1)–N(1)–Cu(1)
#1
Symmetry transformations used to generate equivalent atoms: -x?1, -y?1, -z?1 for complex 1
123

Transition Met Chem (2012) 37:271–277
275
˚
Table 4 Selected bond lengths (A) and bond angles (°) for complex 2
Bond distances
Cu(1)–O(2)
Cu(1)–O(2)#2
Cu(1)–N(1)#2
Cu(1)–N(1)
Br(1)–C(6)
Cl(1)–C(8)
1.878(3)
1.878(3)
1.992(3)
1.992(3)
1.886(4)
1.749(4)
N(1)–C(3)
N(1)–O(1)
O(1)–C(1)
O(2)–C(5)
C(1)–C(2)
C(3)–C(4)
1.286(5)
1.423(4)
1.435(5)
1.308(5)
1.510(5)
1.427(5)
C(4)–C(5)
C(4)–C(9)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
1.403(5)
1.415(5)
1.409(5)
1.375(5)
1.373(5)
1.366(5)
Bond angles
O(2)#2–Cu(1)–O(2)
O(2)#2–Cu(1)–N(1)#2
O(2)–Cu(1)–N(1)#2
O(2)#2–Cu(1)–N(1)
O(2)–Cu(1)–N(1)
N(1)#2–Cu(1)–N(1)
C(3)–N(1)–O(1)
180.00
N(1)–O(1)–C(1)
C(5)–O(2)–Cu(1)
O(1)–C(1)–C(2)
N(1)–C(3)–C(4)
C(5)–C(4)–C(9)
C(5)–C(4)–C(3)
C(9)–C(4)–C(3)
O(2)–C(5)–C(4)
O(2)-C(5)–C(6)
109.9(3)
C(4)–C(5)–C(6)
C(7)–C(6)–C(5)
C(7)–C(6)–Br(1)
C(5)–C(6)–Br(1)
C(8)–C(7)–C(6)
C(9)–C(8)–C(7)
C(9)–C(8)–Cl(1)
C(7)–C(8)–Cl(1)
C(8)–C(9)–C(4)
116.3(4)
122.7(4)
118.7(3)
118.6(3)
119.7(4)
120.5(4)
121.2(3)
118.3(3)
120.3(4)
90.02(1)
131.1(2)
107.4(3)
124.7(4)
120.5(3)
122.6(4)
116.9(4)
123.9(3)
119.8(3)
89.8(1)
89.8(1)
90.2(1)
180.0
109.6(3)
127.1(3)
122.6(2)
C(3)–N(1)–Cu(1)
O(1)–N(1)–Cu(1)
#2
Symmetry transformations used to generate equivalent atoms: -x?1, -y?1, -z?1 for complex 2
Fig. 3 Part of the
supramolecular structure
containing hydrogen bonds for
complex 1
123

276
Transition Met Chem (2012) 37:271–277
˚
Table 5 Putative hydrogen bonds [A, °] in complexes 1 and 2
D–HÁÁÁA
d(D–H)
d(HÁÁÁA)
\DHA
d(DÁÁÁA)
Symmetric code
Complex 1
Complex 2
C8-H8ÁÁÁBr1
C1-H1CÁÁÁBr1
C7-H7ÁÁÁBr1
C3-H3ÁÁÁO1
0.931
0.960
0.930
0.930
3.049
3.015
3.037
2.600
114.9
158.2
139.5
125
3.540(3)
3.923(3)
3.793(3)
3.221(5)
2-x, -1/2?y, 1/2-z
2-x, 1-y, 1-z
2-x, -y, 1-z
1-x, -y, 1-z
Fig. 6 Diagram showing pÁÁÁp stacking interactions of complex 2
Fig. 4 Diagram showing pÁÁÁp stacking interaction for complex 1
˚
Table 6 Putative p–p stacking interactions [A, °] for complexes 1 and 2
Ring (I)
Ring (J)
a
b
DCC
Cg(I)-perp
3.427 (3)
Cg(J)-perp
Slippage
–
Complex 1
Cg1
Cg3I
2.5(3)
30.33
3.964(4)
-3.421(3)
Complex 2
Cg1
Cg3II
Cg3II
3.4(2)
0
22.51
21.65
3.769(2)
3.702(2)
3.401 (1)
3.441(2)
-3.482(2)
–
Cg3
3.441(2)
1.366
Fig. 5 Part of the 3D
supramolecular structure
showing hydrogen bonds of
complex 2
123

Transition Met Chem (2012) 37:271–277
277
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Trans Met Chem 36:21
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In conclusion, we have reported two new Cu(II) com-
plexes, [Cu(L1)2] and[Cu(L2)2] with salicyl mono-oxime
ligands. The crystal structures of the two complexes have
indicated that complexes 1 and 2 have similar structures,
consisting of one Cu(II) atom and two L- units. In both
complexes, the Cu(II) atom, lying on an inversion center, is
four-coordinated in a trans-CuN2O2 square-planar geome-
try by two phenolate O and two oxime N atoms from two
symmetry-related N,O-bidentate oxime ligands. Moreover,
both complexes form an infinite three-dimensional supra-
molecular structure involving intermolecular C–HÁÁÁBr
hydrogen bonds and pÁÁÁp stacking interactions between
metal chelate rings and aromatic rings. The abnormalities
of IR and UV–Vis spectra in the two complexes may be
caused by the substituent effect.
16. Wu HL, Yuan JK, Bai Y, Jia F, Liu B, Kou F, Kong J (2011)
Trans Met Chem 36:819
Supplementary material
17. Wu HL, Gao YC, Yu KB (2004) Trans Met Chem 29:175
18. Wu HL, Wang KT, Kou F, Jia F, Liu B, Yuan JK, Bai Y (2010) J
Coord Chem 64:2676
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as a supplementary
publication (no. CCDC-757709 for complex 1 and CCDC-
757705 for complex 2.). Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (Fax: ?44 1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk). These data can be also obtained
free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
.
19. Sen S, Talukder P, Dey SK, Mitra S, Rosair G, Hughes DL, Yap
GPA, Pilet G, Gramlich V, Matsushita T (2006) J Chem Soc
Dalton Trans 14:1758
20. Dong WK, Shi JY, Xu L, Zhong JK, Duan JG, Zhang YP (2008)
Appl Organomet Chem 22:89
21. Dong WK, Feng JH, Yang XQ (2007) Synth React Inorg Met-Org
Nano-Met Chem 37:189
22. Dong WK, Feng JH, Wang L, Xu L, Zhao L, Yang XQ (2007)
Trans Met Chem 32:1101
23. Dong WK, Tong JF, Sun YX, Wu JC, Yao J, Gong SS (2010)
Trans Met Chem 35:419
24. Wu HL, Huang XC, Yuan JK, Kou F, Jia F, Liu B, Wang KT
(2010) Eur J Med Chem 45:5324
Acknowledgments This work was supported by the Foundation of
the Education Department of Gansu Province (No. 0904-11) and the
‘Jing Lan’ Talent Engineering Funds of Lanzhou Jiaotong University,
which are gratefully acknowledged.
25. Guo CY, Wang YY, Xu KZ, Zhu HL, Shi QZ, Peng SM (2008)
Polyhedron 27:3529
26. Dong WK, Li L, Sun YX, Tong JF, Wu JC (2011) Trans Met
Chem 35:787
27. Wu HL, Jia F, Kou F, Liu B, Yuan JK, Bai Y (2011) Trans Met
Chem 36:847
28. Dong WK, Duan JG, Liu GL (2007) Trans Met Chem 32:702
29. Dong WK, Sun YX, Zhao CY, Dong XY, Xu L (2010) Polyhe-
dron 29:2087
30. Dong WK, He XN, Yan HB, Lv ZW, Chen X, Zhao CY, Tang
XL (2009) Polyhedron 28:1419
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