Construction of chlorido-bridged dinuclear copper(II) complexes with similar tridentate schiff bases

Article abstract of DOI:10.1134/S0022476613060206

Two new chlorido-bridged dinuclear copper(II) complexes [Cu ₂Cl₂(L¹)₂] (1) and [Cu ₂Cl₂(L²)₂] (2), where L1 and L2 are the deprotonated form of Schiff bases 2-[1-(2-mo

Full text of DOI:10.1134/S0022476613060206

Journal of Structural Chemistry. Vol. 54, No. 6, pp. 1140-1144, 2013
Original Russian Text © 2013 S.-S. Qian, H.-H. Li, Z.-L. You, H.-L. Zhu
CONSTRUCTION OF CHLORIDO-BRIDGED DINUCLEAR
COPPER(II) COMPLEXES WITH SIMILAR
TRIDENTATE SCHIFF BASES
S.-S. Qian,1 H.-H. Li,2 Z.-L. You,2 and H.-L. Zhu1
UDC 548.73:541.49:543.422
1
2
Two new chlorido-bridged dinuclear copper(II) complexes [Cu2Cl2(L )2] (1) and [Cu2Cl2(L )2] (2), where
1
2
1
L and L are the deprotonated form of Schiff bases 2-[1-(2-morpholin-4-ylethylimino)ethyl]phenol (HL )
and 2-[1-(2-piperidin-1-ylethylimino)ethyl]phenol respectively, are prepared and structurally characterized
by elemental analysis, IR spectra, and single crystal X-ray crystallography. Complex 1 crystallizes in the
monoclinic space group P21/c with unit cell dimensions a = 8.0816(2) Å, b = 19.1780(3) Å, c =
3
9.6757(3) Å, β = 106.465(2)°, V = 1438.13(6) Å , Z = 2, R1 = 0.0409, and wR2 = 0.1085. Complex 2
crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 7.7640(10) Å, b =
3
19.930(3) Å, c = 9.628(2) Å, β = 103.890(3)°, V = 1446.2(4) Å , Z = 2, R1 = 0.0634, and wR2 = 0.1316.
Each Cu atom in the complexes is coordinated by three donor atoms of the Schiff bases and by two
bridging Cl atoms, forming square pyramidal geometry. The Cl anions are preferred bridging groups for the
construction of dinuclear copper complexes with tridentate Schiff bases.
DOI: 10.1134/S0022476613060206
Keywords: Schiff base, copper complex, dinuclear complex, crystal structure.
Dinuclear complexes with bridging groups are currently attracting much attention for their interesting structures and
wide applications [1-3]. The Schiff bases derived from salicylaldehyde and its derivatives are a kind of versatile ligands in
coordination chemistry. The rational design and construction of dinuclear complexes with Schiff bases are of particular
interest in coordination and structural chemistry. As is well known, halide and pseudohalide groups can link two or more
metal atoms, yielding various polynuclear complexes [4-8]. In this paper, two new dinuclear Schiff base copper(II)
1
2
1
2
complexes with chloride bridges [Cu2Cl2(L )2] (1) and [Cu2Cl2(L )2] (2), where L and L are the deprotonated form of Schiff
1
bases 2-[1-(2-morpholin-4-ylethylimino)ethyl]phenol (HL ) and 2-[1-(2-piperidin-1-ylethylimino)ethyl]phenol (HL )
2
(Scheme 1) respectively, were successfully prepared and characterized.
Scheme 1. Schiff bases
1
School of Life Sciences, Shandong University of Technology, ZiBo, P. R. China; hailiang_zhu@163.com.
2
Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, P. R. China. The text was
submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 54, No. 6, pp. 1110-1114, November-December, 2013.
Original article submitted May 16, 2012; revised June 26, 2012.
1140
0022-4766/13/5406-1140 © 2013 by Pleiades Publishing, Ltd.

Experimental. Materials and measurements. Starting materials, reagents and solvents (analytical grade) were
purchased from commercial suppliers and used without further purification. Elemental analyses were performed on a Perkin-
Elmer 240C elemental analyzer. The IR spectra were recorded on a Jasco FT/IR-4000 spectrometer as KBr pellets in the range
–1
4000-200 cm . Single crystal structural X-ray diffraction was carried out on a Bruker SMART 1000 CCD area diffractometer.
Synthesis of the Schiff bases. The Schiff bases were synthesized by the same method as described here. To the
methanolic solution (50 ml) of 2-acetylphenol (1.0 mmol each) was added a methanolic solution (50 ml) of amines (1.0 mmol
each) under stirring. The mixtures were stirred for 30 min at room temperature to give a yellow solution. The solvent was
evaporated to give a gummy product of the Schiff bases.
1 –1
For HL : Yield 87%. Characteristic IR data: 1612 cm . Anal. Calc. for C14H20N2O2: C, 67.7%; H, 8.1%; N, 11.3%.
2
–1
Found: C, 67.5%; H, 8.2%; N, 11.2%. For HL : Yield 91%. Characteristic IR data: 1612 cm . Anal. Calc. for C15H22N2O:
C, 73.1%; H, 9.0%; N, 11.4%. Found: C, 73.2%; H, 9.0%; N, 11.2%.
1
1
Synthesis of the complexes. [Cu2Cl2(L )2] (1): To the methanolic solution (10 ml) of HL (0.025 g, 0.1 mmol) was
added a methanolic solution (10 ml) of CuCl2·2H2O (0.017 g, 0.1 mmol) under stirring. The mixture was stirred for 30 min at
room temperature to give a blue solution. After keeping the solution in air for a few days, blue block-shaped crystals of 1,
suitable for the X-ray crystal structural determination, formed at the bottom of the vessel on slow evaporation of the solvent.
–1
The crystals were isolated, washed three times with methanol and dried in air. Yield 61%. Characteristic IR data (cm ): 1600
(s), 1235 (m). Anal. Calc. for C28H38Cl2Cu2N4O4: C, 48.6%; H, 5.5%; N, 8.1%. Found: C, 48.3%; H, 5.7%; N, 8.2%.
1
2
[Cu2Cl2(L )2] (2): Complex 2 was synthesized by the similar method as that described for 1, with HL replaced by
2
HL (0.025 g, 0.1 mmol). The blue block-shaped single crystals of 2 were isolated, washed three times with methanol and
–1
dried in air. Yield 53%. Characteristic IR data (cm ): 1598 (s), 1231 (m). Anal. Calc. for C30H42Cl2Cu2N4O2: C, 52.3%; H,
6.1%; N, 8.1%. Found: C, 52.5%; H, 6.2%; N, 8.0%.
X-ray crystallography. Diffraction intensities for the complexes were collected at 298(2) K using a Bruker
SMART 1000 CCD area-detector diffractometer with MoKα radiation (λ = 0.71073 Å). The collected data were reduced with
the SAINT program [9], and multi-scan absorption correction was performed using the SADABS program [10]. The
structures were solved by direct methods. The complexes were refined against F 2 by the full-matrix least-squares method
using SHELXTL [11]. All of the non-hydrogen atoms were refined anisotropically. Hydrogen atoms were placed in
calculated positions and constrained to ride on their parent atoms. The ethylene group in 1 is disordered over two distinct
sites with occupancies of 0.459(2) and 0.541(2). The crystallographic data for the complexes are summarized in Table 1.
Selected bond lengths and angles are given in Table 2.
1
2
Results and discussion. Chemistry. The HL and HL Schiff bases were synthesized by the reaction of equimolar
quantities of 2-acetylphenol with 2-morpholin-4-ylethylamine and 2-piperidin-1-ylethylamine, respectively, in methanol. The
elemental analysis data are in good agreement with the chemical formulas proposed for the compounds. Complexes 1 and 2
1
2
were synthesized by the reaction of the HL and HL Schiff bases with CuCl2⋅2H2O in methanol under ambient conditions.
Structure description of the complexes. Single crystal X-ray diffraction shows that the complexes are structurally
similar to halido-bridged dinuclear copper(II) compounds (Fig. 1 for 1, Fig. 2 for 2). Each complex possesses a crystallographic
inversion center symmetry, with the inversion center located at the midpoint of two Cu atoms. The Cu⋯Cu distances are
3.724(1) Å in 1 and 3.614(1) Å in 2, which are within the values observed in the chlorido-bridged Schiff base copper(II)
complexes deposited in CSD.
In the complexes, the Schiff bases behave as monoanionic and tridentate ligands that coordinate to Cu atoms through
three NNO donor atoms. Each Cu atom in the complexes is five-coordinated in a square pyramidal geometry, with the basal
plane defined by the NNO donor atoms of the correspondding Schiff base ligand and by one bridging Cl atom, and with the
apical position occupied by the another bridging Cl atom. The average trans angles are 167.0(2)° in 1 and 168.2(2)° in 2. The
Cu atoms deviate from the least-squares planes defined by the four basal donor atoms by 0.161(1) Å for 1 and 0.197(1) Å for
2, toward the apical donor atoms. In 1 and 2, the coordinate bond lengths related to the Cu atoms are comparable to each
1141

TABLE 1. Crystallographic Data and Refinement Parameters for the Complexes
Complex
1
C28H38Cl2Cu2N4O4
692.6
2
C30H42Cl2Cu2N4O2
688.7
Formula
Mr
T, K
298(2)
298(2)
Crystal shape/color
Crystal size, mm
Crystal system
Space group
a, b, c, Å; β, deg
Block / blue
0.18×0.17×0.17
Monoclinic
P21/c
Block / blue
0.23×0.20×0.20
Monoclinic
P21/c
8.0816(2), 19.1780(3), 9.6757(3);
106.465(2)
7.7640(10), 19.930(3), 9.628(2);
103.890(3)
3
V, Å
1438.13(6)
2
1446.2(4)
2
Z
–3
1.599
1.581
Dc, g⋅cm
–1
1.706
1.691
μ(MoKα), mm
F(000)
Independent/Observed reflections
(I ≥ 2σ(I ))
716
716
3111/2561
2717/1802
Min. and max. transmission
0.749 and 0.760
191
0.697 and 0.728
182
Parameters
Restraints
16
0
GOOF on F 2
1.043
0.978
a
0.0409, 0.1085
0.0504, 0.1151
0.0634, 0.1316
0.1020, 0.1468
R1, wR2 [I ≥ 2σ(I )]
a
R1, wR2 (all data)
2
0
2
2 1/2
2
aR = F – F /F , wR = [∑w(F – c )/∑w(F0 ) ] .
F
1
0
c
0
2
TABLE 2. Selected Bond Distances (Å) and Angles (deg) for the Complexes
1
Cu1–O1
Cu1–N2
Cu1–Cl1A
Cu1–N1
Cu1–Cl1
1.895(2)
2.073(3)
2.832(1)
1.972(3)
2.280(1)
O1–Cu1–N1
N1–Cu1–N2
90.1(1)
85.5(1)
176.8(1)
106.8(1)
95.4(1)
O1–Cu1–N2
O1–Cu1–Cl1
N2–Cu1–Cl1
N1–Cu1–Cl1A
Cl1–Cu1–Cl1A
157.2(1)
90.6(1)
95.1(1)
89.7(1)
87.1(1)
N1–Cu1–Cl1
O1–Cu1–Cl1A
N2–Cu1–Cl1A
2
Cu1–O1
Cu1–N2
Cu1–Cl1A
Cu1–N1
Cu1–Cl1
1.888(4)
2.044(4)
2.287(2)
1.966(4)
2.692(2)
O1–Cu1–N1
N1–Cu1–N2
N1–Cu1–Cl1A
O1–Cu1–Cl1
N2–Cu1–Cl1
90.5(2)
85.0(2)
179.6(1)
108.2(1)
94.8(1)
O1–Cu1–N2
O1–Cu1–Cl1A
N2–Cu1–Cl1A
N1–Cu1–Cl1
156.8(2)
89.7(1)
94.7(1)
93.0(1)
87.3(1)
Cl1–Cu1–Cl1A
other and also comparable to the corresponding values observed in other similar chlorido-bridged copper(II) complexes with
Schiff bases [4, 12-16].
Coordination number 5 for copper(II) complexes is very common. The question arises as to whether the
coordination polyhedra around the Cu atoms can be described as a distorted square pyramid or a trigonal bipyramid. Further
information can be obtained by determining the structural index τ that represents the relative amount of trigonality (square
pyramid τ = 0; trigonal bipyramid τ = 1); τ = (β – α)/60°, α and β being the two largest angles around the metal atom [17].
1142

Fig. 1. Perspective view of the molecular structure of 1 with the
atom labeling scheme. Thermal ellipsoids are drawn at the 30%
probability level. Only the major component of the disordered
group is shown.
Fig. 2. Perspective view of the molecular structure of 2 with the
atom labeling scheme. Thermal ellipsoids are drawn at the 30%
probability level.
The τ values are 0.33 in 1 and 0.38 in 2. From the τ values it can be concluded that Cu atoms in the complexes adopt a
distorted square pyramidal coordination.
–1
IR spectra. In the IR spectra of the complexes, the strong absorption bands at ca. 1600 cm can be assigned to the
azomethine stretching frequencies of the Schiff base ligands, whereas for the free Schiff bases the corresponding bands are
–1
1
2
observed at 1612 cm for HL and HL . The shift of these bands towards lower frequencies on complexation suggests the
–1
coordination to Cu atoms through the imine N atoms. The ν(C–O) mode is present as middle bands at 1235 cm for 1 and
–1
–1
1231 cm for 2. The weak bands indicative of the Cu–O, Cu–N, and Cu–Cl bonds are located in the region 550-300 cm .
Conclusions. The present paper reports the synthesis and crystal structures of two new chlorido-bridged dinuclear
copper(II) complexes with similar tridentate Schiff bases. The Cl anions are preferred bridging groups for the construction of
1143

dinuclear copper(II) complexes with Schiff bases. The present dinuclear copper(II) complexes may serve as interesting
magnetic materials.
Supplementary information. CCDC-825212 (1) and 825213 (2) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge at http://www.ccdccam.ac.uk/const/retrieving.html or from the
Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033 or
e-mail: deposit@ccdc.cam.ac.uk.
REFERENCES
1. S.-F. Lou, X. Zheng, Y. Chen, and X.-Y. Qiu, J. Struct. Chem., 52, No. 6, 1091-1097 (2011).
2. Z.-L. You, Y. Lu, N. Zhang, B.-W. Ding, H. Sun, P. Hou, and C. Wang, Polyhedron, 30, No. 13, 2186-2194 (2011).
3. R.-H. Hui, P. Zhou, and Z.-L. You, J. Struct. Chem., 51, No. 6, 1201-1204 (2010).
4. S. Thakurta, P. Roy, G. Rosair, C. J. Gómez-García, E. Garribba, and S. Mitra, Polyhedron, 28, No. 4, 695-702 (2009).
5. F. Nepveu, F.-J. Bormuth, and L. Walz, J. Chem. Soc. Dalton Trans., No. 6, 1213-1216 (1986).
6. M. E. Bluhm, M. Ciesielski, H. Gorls, O. Walter, and M. Doring, Inorg. Chem., 42, No. 26, 8878-8885 (2003).
7. Z.-L. You and H.-L. Zhu, Z. Anorg. Allg. Chem., 632, No. 1, 140-146 (2006).
8. J. Manzur, A. M. Garcia, A. Vega, and A. Ibanez, Polyhedron, 26, No. 1, 115-122 (2007).
9. Bruker, SMART and SAINT, Bruker AXS Inc., Madison, Wisconsin, USA (2002).
10. G. M. Sheldrick, SADABS, Univ. Göttingen, Germany (1996).
11. G. M. Sheldrick, SHELXL-97, Univ. Göttingen, Germany (1997).
12. H.-Y. Liu, F. Gao, D.-Z. Niu, and J.-L. Tian, Inorg. Chim. Acta, 362, No. 11, 4179-4184 (2009).
13. Y. M. Chumakov, V. I. Tsapkov, I. G. Filippova, G. Bocelli, and A. P. Gulea, Crystallogr. Rep., 53, No. 4, 619-625
(2008).
14. N. Zhang and Z.-L. You, Transition Met. Chem., 35, No. 4, 437-440 (2010).
15. S. Nayak, P. Gamez, B. Kozlevcar, A. Pevec, O. Roubeau, S. Dehnen, and J. Reedijk, Polyhedron, 29, No. 11, 2291-
2296 (2010).
16. H. Adams, D. E. Fenton, S. R. Haque, S. L. Heath, M. Ohba, H. Okawa, and S. E. Spey, J. Chem. Soc. Dalton Trans.,
No. 12, 1849-1856 (2000).
17. A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn, and G. C. Verschoor, J. Chem. Soc. Dalton Trans., No. 7, 1349-1356
(1984).
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