(2-{[2-Carboxylato-1-(4-chlorophenyl)ethyl]iminomethyl}phenolato-κ3 O,N,O′)(1H-imidazole-κN 3)copper(II) monohydrate

The CuII atom of the title complex, [Cu(C16H12ClNO3)(C3H4N2)]·H2O, has a distorted square-planar coordination geometry formed by a tridentate Schiff base dianion and an imidazole ligand. The imidazole is nearly coplanar with the coordination plane, the dihedral angle between the planes being 3.73 (12)°. In the Schiff base ligand, the two benzene rings are oriented at a dihedral angle of 75.87 (12)°. O—H⋯O and N—H⋯O hydrogen bonding is present in the crystal structure. One H atom of the uncoordinated water molecule is disordered equally over two sites.


Related literature
Transition metal complexes of salicylaldehyde-peptides and salicylaldehyde-aminoacid Schiff bases are non-enzymatic models for pyridoxal amino acid systems, which are of importance as key intermediates in many metabolic reactions of amino acid catalyses by enzymes, see: Bkouche-Waksman et al. (1988); Wetmore et al. (2001); Zabinski & Toney (2001). For the preparation, structural characterization, appropriate spectroscopy and magnetic studies of Schiff-base complexes derived from salicylaldehyde and amino acids, see: Ganguly et al. (2008) and references cited therein. For Schiff bases derived from -amino acids, see: Vančo et al. (2008).

Comment
Transition metal complexes of salicylaldehyde-peptides and salicylaldehyde-amino acid Schiff base are non-enzymatic models for pyridoxal-amino acid systems, which are of considerable importance as key intermediates in many metabolic reactions of amino acids catalyzed by enzymes (Zabinski et al., 2001;Wetmore et al., 2001;Bkouche-Waksman et al.,1988).
Considerable effort has been devoted to the preparation, structural characterization, appropriate spectroscopy and magnetic studies of Schiff-base complexes derived from salicylaldehyde and amino acids and reduced salicylidene amino acid (Ganguly et al., 2008), but little attention has been given to Schiff base derived from β-amino acid (Vančo et al., 2008). Herein, we report the structure study of [Cu(L)(C 3 H 4 N 2 )] . H 2 O (H 2 L= Schiff bases derived from glycylglycine and salicylaldehyde, The complex crystallizes in the monoclinic space group C2/c. The title molecule,is characterized by a square-planar Cu II coordination with the deprotonated tridentate Schiff base dianion and one imidazole molecule in the basal plane (Fig. 1). Hydrogen bond between the coordinated imidazole molecule and the carboxyl oxygen atom of an adjacent, symmetry related CuL unit leads to the formation of a [CuL(C 3 H 4 N 2 )] 2 dimer. Hydrogen bond between water molecule and CuL unit further link the dimers into two-dimension layers (Fig. 2).
3-Amino-3-(4-chlorophenyl) propionic acid (10 mmol) was dissolved and refluxed in absolute methanol (40 ml) containing LiOH . H 2 O (10 mmol). After cooled to room temperature, a solution of salicylaldehyde (10 mmol) in absolute methanol was added slowly with stirring over 10 min. Then Cu(NO 3 ) 2 (10 mmol) was added to the HLLi solution and the resulting solution was adjusted to the pH = 9-11 by 1.0 mol/L NaOH solution. After stirring at room temperature for 30 min, imidazole (10 mmol) was added to the solution with stirring. The resulting clear solution was then filtered. The filtrate was allowed to evaporate slowly at room temperature. After several days dark green crystals suitable for X-ray diffraction were obtained.

Refinement
One H atom of the lattice water molecule is equally disordered over two sites. The water H atoms were placed in chemical sensitive positions and refined with distance restraint of O-H = 0.85 Å and U iso (H) = 1.2U eq (O). Other H atoms were positioned geometrically and constrained as riding atoms with C-H = 0.93-0.98 Å and N-H = 0.86 Å, U iso (H) = 1.2U eq (C,N). Fig. 1. The structure of the title complex with atom numbering scheme; thermal ellipsoids are drawn at 40% probability level. (

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.