Studies on mono- and dinuclear bisoxime copper complexes with different coordination geometries

Article abstract of DOI:10.1007/s11243-010-9344-3

Two new mono- and dinuclear Cu(II) complexes, namely [CuL ¹]0.5H₂O (1) and [(Cu₂(L²) ₂)(DMF)]· 0.5DMF (2) (H₂L¹ = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(p

Full text of DOI:10.1007/s11243-010-9344-3

Transition Met Chem (2010) 35:419–426
DOI 10.1007/s11243-010-9344-3
Studies on mono- and dinuclear bisoxime copper complexes
with different coordination geometries
•
Wen-Kui Dong Jun-Feng Tong Yin-Xia Sun
•
•
•
Jian-Chao Wu Jian Yao Shang-Sheng Gong
•
Received: 5 January 2010 / Accepted: 11 February 2010 / Published online: 19 March 2010
Ó Springer Science+Business Media B.V. 2010
Abstract Two new mono- and dinuclear Cu(II) com-
plexes, namely [CuL1]Á0.5H2O (1) and [(Cu2(L2)2)(DMF)]Á
0.5DMF (2) (H2L1 = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phe-
nyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}
ethane; H2L2 = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-
pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}pro-
pane), have been synthesized and characterized by X-ray
crystallography. The unit cell of complex 1 contains two
crystallographically independent but chemically identical
[CuL1] molecules and one crystalline water molecule,
showing a slightly distorted square-planar coordination
geometry and forming a wave-like pattern running along
the a-axis via hydrogen bonding and pÁÁÁp stacking inter-
actions. Complex 2 has a dinuclear structure, comprising
two Cu(II) atoms, two completely deprotonated phenolate
bisoxime (L2)2- moieties (in the form of enol), and both
coordinated and hemi-crystalline DMF molecules. Com-
plex 2 has square-planar and square-pyramidal geometries
around the two copper centers, whose basic coordination
planes are almost perpendicular and form an infinite three-
dimensional supramolecular network structure involving
intermolecular C–HÁÁÁN, C–HÁÁÁO, and C–HÁÁÁp(Ph)
hydrogen bonding and pÁÁÁp stacking interactions of
neighboring pyrazole rings.
Introduction
Bisoxime compounds have received much attention recently,
not only because the O-alkyloxime groups in these com-
plexes resist metathesis of the C=N bonds [1–4] but also
because the large electronegativity of the oxygen atoms is
expected to affect strongly the electronic properties of the
N2O2 coordination sphere, which can lead to different and
novel properties and structures of the resulting complexes [5,
6]. Bisoximes are fascinating and versatile chelating ligands,
which have been used to form neutral complexes with a
number of divalent transition metal ions through the loss of
the two hydroxyl protons [4, 7, 8].
In the past years, we have prepared a series of complexes
of transition metals with bisoxime ligands and investigated
their coordination behavior, solvent effects, supramolecular
architectures, and other properties [2, 6, 7, 9–11]. As a part
of our comprehensive efforts toward synthesis and structural
characterization of these new materials, we now report on
two new Cu(II) complexes, namely [CuL1]Á0.5H2O (1) and
[(Cu2(L2)2)(DMF)]Á0.5DMF (2) (H2L1 = 1,2-bis{[(Z)-(3-
methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]
methyleneaminooxy}ethane; H2L2 = 1,3-bis{[(Z)-(3-methyl-
5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-
aminooxy}propane), obtained by the complexation of two
bisoximes with Cu(II) in different solvents (Scheme 1). We
discuss their coordination behavior, the influence of solvent,
and the effects of variations in ligands in the formation and
structure of the complexes.
W.-K. Dong (&) Á J.-F. Tong Á Y.-X. Sun Á J.-C. Wu Á
J. Yao Á S.-S. Gong
Experimental
School of Chemical and Biological Engineering,
Lanzhou Jiaotong University, 730070 Lanzhou,
People’s Republic of China
4-Benzoyl-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one (BMPP)
from East China Normal University Chemical Plant was
e-mail: dongwk@126.com
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Transition Met Chem (2010) 35:419–426
Scheme 1 Synthesis of H2L1
and H2L2 (n = 0, H2L = H2L1;
n = 1, H2L = H2L2) and
structural formulae of
complexes 1 and 2
(S = solvent DMF)
Ph
Ph
O
N
O
N
MeOH
N
N
Cu
N
N
n
O
O
Ph
Ph
Ph
O
O
N
Ph
Ph
Complex 1
O
N
n
H2N O O NH2
EtOH; 55°C
Ph Ph
N
N
N
N
N
N
N
N
O
O
O
N
N
Ph
Ph
Ph
O
Cu
Cu
Ph
Ph
Ph
O
BMPP
H2L
MeOH+DMF
O
O
O
O
N
N
N
N
O
O
Ph
S
N
N
N
N
Ph
Ph
Complex 2
used without further purification. The other reagents and
solvents were analytical grade reagents from Tanjin Chem-
ical Reagent Factory.
ethanol and ethanol–hexane (1:4) (3 9 4 mL). The product
was purified by recrystallization from ethanol and dried
under vacuum, yielding a white powder (Yield 0.2035 g,
69%, M.P. 191–193 °C). Found: C, 70.4; H, 5.2; N, 13.8.
Calcd. for C36H32N6O4 (%): C, 70.6; H, 5.3; N, 13.7.
Carbon, hydrogen, and nitrogen were analyzed with a
GmbH VariuoEL V3.00 automatic elemental analyzer.
Elemental analyses for Cu were determined with an
IRIS ER/SÁWP-1 ICP atomic emission spectrometer.
FTIR spectra were recorded on a VERTEX70 FT-IR
spectrophotometer, with samples prepared as KBr (4,000–
500 cm-1) and CsI (500–100 cm-1) pellets. UV–vis
spectra were taken on a Shimadzu UV-240 spectropho-
tometer. Electrolytic conductance measurements were
made with a DDS-11A type conductivity bridge using
1.0 9 10-3 mol L-1 solutions in DMF at room tempera-
ture. Melting points were measured by the use of a
microscopic melting point apparatus made by the Beijing
Taike instrument limited company, and the thermometer
was uncorrected. TG–DTA analyses were carried out in an
N2 atmosphere at a heating rate of 5 °C/min in the tem-
perature range 25–900 °C on a ZRY-1P thermoanalyzer,
using an Al2O3 crucible. X-ray single-crystal structure
determination was carried out on a Bruker Smart APEX
CCD diffractometer.
Synthesis of H2L2
1,3-Bis(aminooxy)propane was synthesized using an anal-
ogous method to that reported earlier [12].
A colorless ethanol solution (4 mL) of 1,3-bis(amino-
oxy)propane (56.4 mg, 0.531 mmol) was slowly added to a
yellow ethanol solution (4 mL) of BMPP (300.5 mg,
1.08 mmol), and the mixture was stirred for 24 h at 55 °C.
After cooling to room temperature, the precipitate was
filtered off and washed successively with ethanol and
ethanol–hexane (1:4) (3 9 4 mL). The product was puri-
fied by recrystallization from ethanol and dried under
vacuum, yielding a white powder (Yield 0.2617 g, 77%,
M.P. 194–195 °C). Found: C, 70.8; H, 5.4; N, 13.5. Calcd.
for C37H34N6O4 (%): C, 70.9; H, 5.5; N, 13.4.
Preparation of complex 1
Synthesis of H2L1
A pale-blue MeOH solution (2 mL) of copper acetate
monohydrate (4.3 mg, 0.022 mmol) was added dropwise to
a colorless MeOH solution (4 mL) of H2L1 (5.1 mg,
0.0083 mmol) at room temperature. The color of the
solution immediately turned brown. The mixture was fil-
tered, and the filtrate was left standing at room temperature
to crystallize for about 3 weeks. With evaporation of the
solvent, brown needle-like single crystals suitable for
X-ray crystallographic analysis were obtained. Found: C,
63.1; H, 4.3; N: 12.5; Cu, 9.2. Calcd. for [CuL1]Á0.5H2O
(C36H31CuN6O4.5) (%): C, 63.3; H, 4.6; N, 12.3; Cu, 9.3.
1,2-Bis(aminooxy)ethane was synthesized by a similar
1
method to that reported earlier [12]. H NMR (400 MHz,
CDCl3, d, ppm): 3.79 (s, 4H), 5.52 (s, 4H). H2L1 was
synthesized according to a method analogous to that
reported earlier [13]. A colorless ethanol solution (4 mL)
of 1,2-bis(aminooxy)ethane (43.2 mg, 0.469 mmol) was
slowly added to a yellow ethanol solution (4 mL) of BMPP
(267.2 mg, 0.961 mmol), and the mixture was stirred for
24 h at 55 °C. After cooling to room temperature, the
precipitate was filtered off and washed in succession with
123

Transition Met Chem (2010) 35:419–426
421
Preparation of complex 2
As expected, there are no obvious m(O–H) or m(N–H)
absorption bands near 3,400 and 3,145 cm-1 in the free
bisoximes H2L1 and H2L2. H2L1 and H2L2 exhibit char-
A pale-blue methanol solution (5 mL) of copper chloride
dihydrate (2.8 mg, 0.016 mmol) was added dropwise to
a colorless DMF solution (5 mL) of H2L2 (4.0 mg,
0.006 mmol) at room temperature. The color of the mixing
solution immediately turned brown. The mixture was fil-
tered, and the filtrate was allowed to stand at room tem-
perature for about 3 weeks. With evaporation of the mixed
solvent, brown block-like single crystals suitable for X-ray
crystallographic analysis were gained. Found: C, 63.4; H,
5.0; 12.8; Cu, 8.5. Calcd. for [(Cu2(L2)2)(DMF)]Á0.5DMF
(C78.5H74.5Cu2N13.5O9.5) (%): C, 63.4; H, 5.1; N, 12.7; Cu,
8.6.
acteristic C=N stretching bands at 1,618 and 1,620 cm-1
,
respectively, assigned to the pyrazole ring, and for com-
plexes 1 and 2, the corresponding bands were observed at
1,597 and 1,608 cm-1, respectively, indicating red shifts of
21 and 12 cm-1. The oxime C=N bands are 1,593 and
1,595 cm-1 for H2L1 and H2L2, respectively. Both of these
are red shifted by 29 cm-1 in complexes 1 and 2 [16].
Hence, the red shift of the oxime C=N of the chain is
bigger than that of the ring, owing to coordination of the
azomethine nitrogen to the copper center. Bands in the
range of 1,535–1,423 cm-1 were attributed to the aromatic
C=C skeleton vibrations. The spectrum of complex 1
shows new bands at 3,279 and 1,638 cm-1 which could be
attributed to crystalline water. A weak band at 1,724 and
1,722 cm-1 for the free bisoximes H2L1 and H2L2 is absent
in the spectra of the corresponding complexes, which is
attributed to the carbonyl oxygen coordinating to the cop-
per center. Weak bands at 509 and 441 cm-1 for complex 1
and at 538 and 439 cm-1 for complex 2 are assigned to
m(Cu–N) and m(Cu–O) [17], respectively, consistent with
the literature values [18–20].
The UV–vis absorption spectra of H2L1 and H2L2 and
their corresponding complexes 1 and 2 were determined in
1 9 10-4 mol L-1 DMF solution. The spectra of free H2L1
and H2L2 exhibit absorption peaks at ca. 273 and 273 nm,
respectively. Complexes 1 and 2 have similar UV–vis
spectra, with maxima at ca. 272 and 269 nm, respectively.
These peaks can all be assigned to the p–p* transitions of
the benzene and pyrazole rings. The small hypsochromic
shifts of ca. 1–4 nm for the complexes are consistent with
coordination between Cu(II) and the ligands.
Crystal structure determination and refinement
Single-crystal X-ray diffraction data were collected at
298 K on a BRUKER SMART APEX II CCD diffrac-
tometer with graphite monochromated Mo-Ka radiation
˚
(k = 0.71073 A). The LP factor semi-empirical absorption
corrections were applied using the SADABS program [14].
The structure was solved by direct methods and refined
by the full-matrix least-squares method on F2 using the
SHELXTL crystallographic software package [15]. The
non-hydrogen atoms were refined anisotropically; hydrogen
atoms were positioned geometrically (C–H = 0.93, 0.96
˚
and 0.97 A) and were refined as riding, with Uiso(H) = 1.20
or 1.50 Ueq(C). The crystal data and experimental param-
eters relevant to the structure determination are listed in
Table 1.
Results and discussion
Thermal stability studies were performed for both com-
plexes. The TG curve of complex 1 can be divided into two
stages, and the first stage is at 116–167 °C. The weight loss
corresponding to this temperature range is 1.5%, which
roughly coincides with the value of 1.3% calculated for the
loss of a hemi-crystalline water molecule from the outer
coordination sphere of complex 1. The solid remains stable up
to 240 °C, and the second weight loss starts at around 255 °C,
with decomposition of the compound. The TG curve shows
around 87% total mass loss at 800 °C, indicating complete
loss of the L1 unit. The main residual product was CuO, with a
value of 12.3% (theoretical value 11.7%).
Complexes 1 and 2 with new tetradentate bisoxime chelating
ligands have been synthesized and characterized by molar
conductance, IR and UV–vis spectra, TG–DTA and X-ray
crystallography analyses. Both complexes are soluble in both
DMF and DMSO but not soluble in CHCl3, DCM, EtOH,
MeOH, MeCN, THF, acetone, ethyl acetate, or n-hexane.
Noticeably, only complex 1 displays good stability in air at
room temperature but complex 2 is markedly unstable. The
free bisoximes (H2L1 and H2L2) are both soluble in all of the
aforementioned solvents. The molar conductance values of
complexes 1 and 2 in 1.0 9 10-3 mol L-3 DMF solutions
are 2.2 and 2.9 X-1 cm2 mol-1, respectively, indicating
that these complexes are non-electrolytes.
The TG curve of complex 2 can be divided into three
stages. The first stage is at 70–86 °C. The weight loss
corresponding to this temperature range is 2.9%, again
corresponding to a value of 2.6% calculated for the loss of
a hemi-crystalline DMF molecule from the outer coordi-
nation sphere. The second stage starts from 101 to 181 °C
with a weight loss of 5.5%, which corresponds to the loss
The FTIR spectra of H2L1 and H2L2 together with their
corresponding complexes 1 and 2 were recorded in the
4,000–400 cm-1 region, and the most important bands are
given in Table 2.
123

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Transition Met Chem (2010) 35:419–426
Table 1 Crystal data and structure refinement parameters for complexes 1 and 2
Complex
1
2
Empirical formula
Formula weight (g mol-1
C36H31CuN6O4.5
683.21
C78.50H74.50Cu2N14O9.50
1486.10
)
Crystal system, space group
Temperature (K)
Triclinic; P - 1
298(2)
Triclinic; P - 1
298(2)
˚
Unit cell dimensions (A, °)
a = 12.768(1)
b = 13.036(2)
c = 21.811(2)
a = 80.304(2)
b = 80.155(2)
c = 63.925(1)
3194.8(6)
a = 13.178(1)
b = 13.980(1)
c = 22.021(2)
a = 72.040(1)
b = 75.727(1)
c = 77.361(2)
3
˚
V (A )
3694.7(6)
Z, Calculated density (mg/m3)
4; 1.420
2; 1.336
Absorption coefficient (mm-1
h range for data collection (°)
Limiting indices
)
0.736
0.643
1.75–25.02
1.55–25.02
-15 B h B 15, -12 B k B 15, -21 B l B 25
1,416
-15 B h B 15, -16 B k B 9, -26 B l B 26
1,548
F (000)
Crystal size (mm)
0.34 9 013 9 0.06
16,822/11,066
[R(int) = 0.0805]
Full-matrix least-squares on F2
11,066/0/860
0.24 9 0.14 9 0.05
19,725/12,902
Reflections collected/unique
[R(int) = 0.0528]
Full-matrix least-squares on F2
12,902/6/986
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2r(I)]
R indices (all data)
1.033
0.912
R1 = 0.0933, wR2 = 0.2107a
R1 = 0.1757, wR2 = 0.2408
1.837 and -0.854
757702
R1 = 0.0695, wR2 = 0.1741b
R1 = 0.1500, wR2 = 0.2114
0.783 and -0.513
757711
-3
)
˚
Max, min Dq (e A
CCDC
a
b
w = 1/[r2(Fo2) ? (0.097P)2], w = 1/[r2(Fo2) ? (0.1015P)2], where P = (Fo2 ? 2F2c)/3
Table 2 Principal FTIR bands for the bisoximes and their complexes (cm-1
)
Compound
m(C–H)
m(C=O)
m(C=N) ring
m(C=N) chain
m(Cu–N)
m(Cu–O)
m(C=C) benzene ring skeleton
H2L1
3,059
3,063
3,061
3,047
1,724
–
1,618
1,597
1,620
1,608
1,593
1,564
1,595
1,566
–
–
1,535, 1,499, 1,458
1,525, 1,493, 1,435
1,533, 1,501, 1,458
1,516, 1,456, 1,423
Complex 1
H2L2
509
–
441
–
1,722
–
Complex 2
538
439
of one coordinated DMF (theoretical mass loss 5.1%). The
solid remains stable up to 216 °C, and the third weight loss
starts at around 223 °C, with decomposition of the com-
pound. The TG curve shows around 80% total mass loss at
650 °C, indicating complete removal of the L2 unit. The
main residual product was CuO, with a value of 11%
(theoretical value 10.8%).
chemically identical mononuclear [CuL1] molecules (A
and B) and one crystalline water molecule (Fig. 1). Mol-
ecules A and B both consist of one Cu(II) atom and one
(L1)2- unit (in the enol tautomeric form). Each Cu(II)
center is tetra-coordinated and lies in the cis-N2O2 donor
site of the ligand. Consequently, the coordination envi-
ronment around the Cu(II) center can be described as a
slightly distorted square-planar geometry. Compared with
molecule A, molecule B is similar in the overall structure
but distinct in some bond distances and angles (Table 3).
Description of the crystal structures
˚
The Cu1 atom for molecule A is 0.038 A out of the N2O2
X-ray crystallographic analysis reveals that complex 1
crystallizes in the triclinic system, space group P-1, and the
unit cell contains two crystallographically independent but
coordination plane, while the Cu2 atom for molecule B is
˚
0.031 A out of the N2O2 coordination plane.
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Transition Met Chem (2010) 35:419–426
423
Fig. 1 The ORTEP view of the
crystal structure with thermal
ellipsoids was drawn at the 30%
probability for complex 1, and
hydrogen atoms have been
omitted for clarity
˚
stabilizing the structure of the crystal. The neighboring
units are linked into an infinite one-dimensional chain by
intermolecular hydrogen bonding (O9–H9CÁÁÁO6 and C38–
H38AÁÁÁO9) forming a five-membered ring with a graph
motif R22(5), and hydrogen bonding (O9–H9ÁÁÁN10 and
C51–H51ÁÁÁO9) that can be described as an R22(7) motif and
produces an eight-membered ring. The packing diagram
shows that complex 1 forms a wave-like pattern running
along the a-axis via weaker pÁÁÁp stacking interactions
between two neighboring pyrazole rings as well as the
benzene and metal chelate rings (Table 5).
Table 3 Selected bond distances (A) and bond angles (°) for com-
plexes 1 and 2
Complex 1
Complex 2
Bond lengths
Cu(1)–O(4)
Cu(1)–O(3)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(2)–O(8)
Cu(2)–O(7)
Cu(2)–N(7)
Cu(2)–N(8)
1.919(5)
1.930(5)
1.952(6)
2.037(6)
1.908(5)
1.938(5)
1.948(6)
2.023(6)
Cu(1)–O(7)
Cu(1)–O(3)
Cu(1)–N(1)
Cu(1)–N(7)
Cu(2)–O(8)
Cu(2)–O(4)
Cu(2)–N(8)
Cu(2)–N(2)
Cu(2)–O(9)
1.894(4)
1.912(4)
1.995(5)
1.999(5)
1.916(4)
1.932(4)
1.973(5)
1.989(5)
2.643(9)
X-ray crystal structure analysis shows that complex 2
has a dinuclear structure, consisting of two Cu(II) atoms,
two deprotonated (L2)2- units (in the enol form), one
coordinated DMF ligand, and a hemi-crystalline DMF
molecule (Fig. 3). The center Cu1 atom is tetra-coordi-
nated in a trans-N2O2 plane by two oxime nitrogen (N1,
N7) atoms and two oxygen (O3, O7) atoms of two
deprotonated (L2)2- units, displaying a slightly distorted
square-planar coordination motif. The center Cu2 atom is
penta-coordinated by two oxime nitrogen (N2, N8) atoms
and two oxygen (O4, O8) atoms of two (L2)2- units
defining the cis-N2O2 basal plane, plus one carbonyl oxy-
gen (O9) atom from a DMF ligand occupying the apical
position. Therefore, the coordination environment around
Cu2 is best regarded as a slightly distorted square-pyra-
midal geometry with the distance of the apical oxygen O9
atom to the N2O2 basal plane being 2.642. The center atom
Cu1 is 0.085 out of the N2O2 coordination plane, while
the deviation of Cu2 atom from the N2O2 basal plane is
0.124. An interesting feature is that the basal plane of Cu1
and the equatorial plane of Cu2 are almost perpendicular,
making a dihedral angle of 84.97° to each other, and the
long distance (Cu1ÁÁÁCu2 = 7.082) between two coppers
suggests that there is no interaction between these two
metal centers.
Bond angles
O(4)–Cu(1)–O(3)
O(3)–Cu(1)–N(1)
O(3)–Cu(1)–N(2)
O(8)–Cu(2)–O(7)
O(7)–Cu(2)–N(7)
O(7)–Cu(2)–N(8)
O(4)–Cu(1)–N(1)
O(4)–Cu(1)–N(2)
N(1)–Cu(1)–N(2)
O(8)–Cu(2)–N(7)
O(8)–Cu(2)–N(8)
N(7)–Cu(2)–N(8)
82.5(2)
91.5(2)
161.1(3)
83.0(2)
92.0(2)
161.6(3)
164.7(2)
91.4(2)
98.4(3)
165.2(2)
90.5(2)
98.2(3)
O(7)–Cu(1)–O(3)
O(7)–Cu(1)–N(1)
O(3)–Cu(1)–N(1)
O(7)–Cu(1)–N(7)
O(3)–Cu(1)–N(7)
N(1)–Cu(1)–N(7)
O(8)–Cu(2)–O(4)
O(8)–Cu(2)–N(8)
O(4)–Cu(2)–N(8)
O(8)–Cu(2)–N(2)
O(4)–Cu(2)–N(2)
N(8)–Cu(2)–N(2)
O(8)–Cu(2)–O(9)
O(4)–Cu(2)–O(9)
N(8)–Cu(2)–O(9)
N(2)–Cu(2)–O(9)
170.2(2)
88.8(2)
90.8(2)
92.4(2)
91.2(2)
160.9(2)
87.2(2)
91.5(2)
148.1(2)
162.7(2)
92.1(2)
98.1(2)
79.8(2)
89.0(2)
122.2(2)
82.9(2)
As shown in Fig. 2, molecules of complex 1 are con-
nected by intramolecular C–HÁÁÁO hydrogen bonding and
C–HÁÁÁp(Ph) interactions (Table 4), which play a role in
123

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Transition Met Chem (2010) 35:419–426
Fig. 2 Diagram showing
hydrogen bonds and pÁÁÁp
interactions for complex 1.
Hydrogen atoms, except those
involved in hydrogen bonds,
have been omitted for clarity
˚
˚
Table 5 pÁÁÁp stacking interaction (A, °) for complexes 1 and 2
Table 4 Hydrogen bonding distances (A) and bond angles (°) for
complexes 1 and 2
˚ ˚ ˚
DCC (A) CgI-prep (A) CgJ-prep (A)
Ring 1 Ring 2
a
D–HÁÁÁA
D–H
HÁÁÁA
DÁÁÁA
D–HÁÁÁA
Complex 1
Complex 1
Cg4
Cg9
Cg5
1.93(2) 3.654(4)
3.336 (3)
-3.350(3)
C15–H15ÁÁÁO3
C36–H36ÁÁÁO4
C38–H38AÁÁÁO9
C51–H51ÁÁÁO9
C55–H55ÁÁÁO7
C68–H68ÁÁÁO8
O9–H9DÁÁÁN10
O9–H9CÁÁÁO6
C6–H6BÁÁÁCg10a
C23–H23BÁÁÁCg12a
C59–H59BÁÁÁCg16a
Complex 2
0.93
0.93
0.97
0.93
0.93
0.93
0.85
0.85
0.93
0.96
0.96
2.33
2.32
2.58
2.84
2.29
2.33
2.12
2.29
2.93
3.26
2.98
2.93(1)
2.896(9)
3.254(3)
3.584(5)
2.866(9)
2.88(1)
122
120
127
139
120
117
139
120
121
115
115
Cg15
2.3(4) 3.682(5) -3.469(3)
3.448(4)
Complex 2
Cg1
Cg1X
0
3.303(3) -3.174(2)
-3.173(2)
Symmetry codes: (X) 1 - x, 1 - y, -z. DCC = distance between
ring centroids; a = dihedral angle between planes I and J; CgI-
perp = perpendicular distance of Cg(I) from ring J; CgJ-perp (MeJ–
perp) = perpendicular distance of Cg(J) from ring I (perpendicular
distance of Cg(I) from metal J). Cg4, Cg5, Cg9, and Cg15 for com-
plex 1 are the centroids of atoms N5\N6\C20–C22, N9\N10\C39–
C41, Cu1\O4\C20\C21\C24\N2, and C50–C55; Cg1 for complex 2 is
the centroid of atoms N3\N4\C4–C6
2.923(4)
3.090(4)
3.52(2)
3.490(1)
3.49(1)
As shown in Fig. 4, there are a large number of intra-
molecular C–HÁÁÁO and C–HÁÁÁp(Ph) hydrogen bonding
interactions (Table 4) in the molecular unit of complex 2
and C–HÁÁÁO hydrogen bonds form an S(6) motif produc-
ing a six-membered ring and stabilizing the molecular
structure. Intermolecular hydrogen bonds between C44–
H44ÁÁÁN4, 78–H78ÁÁÁO4, and C79–H79ÁÁÁN6 (Table 4) link
three neighboring molecules into a three-polymeric struc-
ture. Adjacent molecular units are linked together by pÁÁÁp
stacking interactions between two neighboring pyrazole
rings and intermolecular C–HÁÁÁp(Ph) interactions to give
an infinite three-dimensional supramolecular network
structure.
C1–H1BÁÁÁO7
0.97
0.93
0.93
0.97
0.96
0.93
0.96
0.93
0.96
0.93
0.95
0.93
0.96
0.93
2.51
2.22
2.31
2.38
2.54
2.23
2.54
2.41
2.59
2.55
2.39
2.93
2.82
2.95
3.107(8)
2.849(8)
2.903(9)
2.985(7)
3.35(1)
2.871(8)
3.49(4)
2.938(8)
3.41(2)
3.12(4)
3.11(3)
3.729(7)
3.33(1)
3.592(9)
119
124
121
120
141
126
173
116
142
119
132
145
114
127
C16–H16ÁÁÁO3
C37–H37ÁÁÁO4
C38–H38BÁÁÁO3
C44–H44A ÁÁÁN4i
C57–H57ÁÁÁO7
C61–H61AÁÁÁN14
C70–H70ÁÁÁO8
C76–H76CÁÁÁO9
C78–H78ÁÁÁO4ii
C79–H79AÁÁÁN6iii
C14–H14ÁÁÁCg8biv
C44–H44CÁÁÁCg11b
C66–H66ÁÁÁCg8b
To sum up, the structure of complex 2 is obviously
different from complex 1. Complex 2 is a dinuclear
structure with two ligand units, whereas complex 1 is a
mononuclear structure with one ligand unit. Moreover, the
central Cu(II) (Cu1) atoms in complexes 1 and 2 are all
tetra-coordinated in the N2O2 plane, but the coordination
Symmetry codes: (i) x - 1, y, z; (ii) -x ? 1, -y ? 1, -z ? 1; (iii) x ? 1,
y, z; (iv) 1 - x, 1 - y, 1 - z
Cg10a, Cg12a, and Cg16a for complex 1 are the centroids of atoms C8–
C13, C26–C30, and C61–C66, respectively. Cg8b and Cg11b for complex
2 are the centroids of atoms C15–C20 and C46–C51, respectively
123

Transition Met Chem (2010) 35:419–426
425
Fig. 3 The ORTEP view of the
crystal structure with thermal
ellipsoids was drawn at the 30%
probability for complex 2, and
hydrogen atoms have been
omitted for clarity
Fig. 4 Diagram showing
hydrogen bonds and pÁÁÁp
interactions for complex 2.
Hydrogen atoms, except those
involved in hydrogen bonds,
have been omitted for clarity
modes of the N2O2 donor sites are especially different.
These adopt the cis-conformation and come from the same
ligand unit in complex 1, whereas they adopt the trans-
conformation and come from two ligand units in complex 2.
These differences may be explained by the templating
effect resulting from the different ligands. When the O-
alkyl chain length increases, the L2- moieties become more
flexible and long enough to accommodate two Cu(II) atoms
so as to resist the steric effect of the phenyl group at position
1 of the ligands. So the complex is a mononuclear structure
when the O-alkyl chain length is short (two CH2 groups),
while a dinuclear structure is obtained when the O-alkyl
chain is longer (three CH2 groups).
five. But in complex 1, there is no solvent coordinating to
the central Cu(II) atom, and the coordination number of the
Cu(II) atoms is four. These differences may be attributed to
the solvent effect.
Conclusion
Two new mono- and dinuclear Cu(II) complexes with
bisoxime ligands derived from 4-acyl-pyrazolone and O-
alkyldiamines of varying O-alkyl backbone chain lengths
have been synthesized and structurally characterized by X-
ray crystallography. Because of the different performance
of the ligands and the introduction of solvent molecules,
the complexes present different structural features. As the
O-alkyl chain length increases in the resulting complexes,
the L2- moieties become more flexible and long enough to
In addition, in complex 2, oxygen (O9) from one DMF
ligand coordinates to one Cu(II) atom (Cu2) if one con-
˚
siders Cu2-O9 with distance of a 2.642 A as a weak bond.
The coordination numbers of the Cu(II) atoms are four and
123

426
Transition Met Chem (2010) 35:419–426
4. Kalarani N, Sangeetha S, Kamalakannan P, Venkappayya D
(2003) Russ J Coord Chem 29:845
5. Dong WK, He XN, Yan HB, Lv ZW, Chen X, Zhao CY, Tang XL
(2009) Polyhedron 28:1419
6. Akine S, Dong WK, Nabeshima T (2006) Inorg Chem 45(12):
4677
7. Dong WK, Zhu CE, Wu HL, Ding YJ, Yu TZ (2007) Synth React
Inorg Met-Org Nano-Met Chem 37:61
accommodate two Cu(II) atoms so as to resist the steric
effect of the phenyl at position 1 of ligand. So the complex
is mononuclear when the O-alkyl chain length is short,
while a dinuclear structure is obtained when the O-alkyl
chain is larger. In addition, the coordination environment
around Cu(II) changes from square-planar in complex 1 to
square-pyramidal in complex 2 with the introduction of a
solvent ligand in complex 2.
8. Akine S, Taniguchi T, Nabeshima T (2004) Inorg Chem 43:6142
9. Dong WK, Sun YX, Zhang YP, Li L, He XN, Tang XL (2009)
Inorg Chim Acta 362:117
10. Dong WK, Chen X, Sun YX, Yang YH, Zhao L, Xu L, Yu TZ
(2009) Spectrochim Acta Part A 74:719
11. Dong WK, Duan JG, Guan YH, Shi JY, Zhao CY (2009) Inorg
Chim Acta 362(4):1129
Supplementary material
12. Dixon DW, Weiss RH (1984) J Org Chem 49:4487
13. Dong WK, Duan JG, Liu GL (2007) Trans Met Chem 32:702
14. Sheldrick GM (1996) SADABS, siemens area detector absorption
Crystallographic data have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary
publication, No. CCDC 757702 and 757711 for complexes
1 and 2, respectively. Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Telephone: ?44-01223-762910;
Fax: ?44-1223-336033; 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.
¨
corrected software. University of Gottingen, Germany
15. Sheldrick GM (1997) SHELXTL NT, version 5.1; program for
¨
solution and refinement of crystal structures. University of Got-
tingen, Germany
16. Bovio B, Cingolani A, Marchetti F, Pettinari C (1993) J Orga-
nomet Chem 458:39
17. Sen S, Talukder P, Dey SK, Mitra S, Rosair G, Hughes DL, Yap
GPA, Pilet G, Gramlich V, Matsushita T (2006) Dalton Trans
1758
18. Dong WK, Shi JY, Xu L, Zhong JK, Duan JG, Zhang YP (2008)
Appl Organometal Chem 22(2):89
19. Dong WK, Feng JH, Yang XQ (2007) Synth React Inorg Met-Org
Nano-Met Chem 37(3):189
20. Dong WK, Feng JH, Wang L, Xu L, Zhao L, Yang XQ (2007)
Trans Met Chem 32(8):1101
Acknowledgments This work was supported by the Foundation of
the Education Department of Gansu Province (No. 0904-11) and the
‘JingLan’ Talent Engineering Funds of Lanzhou Jiaotong University,
which are gratefully acknowledged.
References
1. Akine S, Taniguchi T, Nabeshima T (2001) Chem Lett 30(7):682
2. Akine S, Taniguchi T, Dong WK, Nabeshima T (2005) J Org
Chem 70(5):1704
3. Dong WK, Zhao CY, Sun YX, Tang XL, He XN (2009) Inorg
Chem Commun 12:234
123