Bis[4-chloro-2-(iminomethyl)phenolato]copper(II) methanol disolvate

The title compound, [Cu(C7H5ClNO)2]·2CH3OH, possesses crystallographic twofold symmetry, with the twofold axis passing through the central CuII ion. The metal centre is coordinated by two O atoms and two N atoms from two symmetry-related Schiff base ligands, forming a slightly distorted cis-CuN2O2 square-planar geometry. The complex molecules are linked via the solvent methanol molecules by O—H⋯O and N—H⋯O hydrogen bonds, leading to the formation of chains along the b axis.

The title compound, [Cu(C 7 H 5 ClNO) 2 ]Á2CH 3 OH, possesses crystallographic twofold symmetry, with the twofold axis passing through the central Cu II ion. The metal centre is coordinated by two O atoms and two N atoms from two symmetry-related Schiff base ligands, forming a slightly distorted cis-CuN 2 O 2 square-planar geometry. The complex molecules are linked via the solvent methanol molecules by O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, leading to the formation of chains along the b axis.
The author thanks Xi'An Medical University for financial support.

Comment
The syntheses of copper(II) complexes with Schiff base have been reported for their applications in the design and construction of new magnetic materials (Erxleben & Schumache, 2001;Stewart et al., 1961). Some of these complexes also inhibit the cellular proteasome activity (Adsule et al., 2006). As an extension of the work on structural characterization of mononuclear copper(II) complexes, the crystal structure of the title compound is reported.
Complex (I) is a mononuclear copper(II) compound. The central Cu II atom is coordinated by two O atoms and two N atoms of the two Schiff base ligands to form a slightly distorted square-planar geometry, with angles subtended at the copper(II) atoms in the range 84.48 (12)°-172.02 (10)°. The Cu-O and Cu-N bond lengths are 1.915 (2) Å and 1.939 (2) Å, respectively, which are a little longer than the corresponding value of 1.842 (3) Å and 1.837 (3) Å observed in a similar Schiff base copper(II) complex (Li & Zhang, 2004).
Intermolecular O-H···O and N-H···O hydrogen bonds involving atoms O1 and N1 from the Schiff base and O2 from the methanol (Table 1) link the molecules to form chains along the b axis. From Fig. 2, it can be seen that benzene rings from neighbouring complexes are parallel but the distance between their centroids is 3.852 (2) Å, which is longer than the distance (3.4 Å) between neighbouring base pairs in DNA (Wei et al., 2004), indicating no π···π packing interactions.

Experimental
All chemicals were of reagent grade and commercially available from the Beijing Chemical Reagents Company of China, and were used without further purification. 5-Chloro-2-hydroxybenzaldehyde (0.2 mmol, 31.32 mg), isopropylamine (0.2 mmol, 11.8 mg) and Cu(Ac) 2 (0.1 mmol 18.2 mg) were dissolved in methanol (10 ml). The mixture was stirred at room temperature for 30 min and then filtered. The filtrate was allowed to stand in air for 7 d, after which time yellow block-shaped crystals of the title compound were formed by slow evaporation of the solvent.  Fig. 1. The asymmetric unit of (I), showing 30% probability displacement ellipsoids. The dashed line indicates a hydrogen bond; symmetry code: (A) 1 -x, y, 3/2 -z.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.