Crystal structure, Hirshfeld surface analysis and computational study of bis-(2-{[(2,6-di-chloro-benzyl-idene)hydrazinyl-idene]meth-yl}phenolato)cobalt(II) and of the copper(II) analogue

The title homoleptic Schiff base complexes, [M(C14H9Cl2N2O)2], for M = CoII, (I), and CuII, (II), present distinct coordination geometries despite the Schiff base dianion coordinating via the phenolato-O and imine-N atoms in each case. For (I), the coordination geometry is based on a trigonal bipyramid whereas for (II), a square-planar geometry is found (Cu site symmetry ). In the crystal of (I), discernible supra-molecular layers in the ac plane are sustained by chloro-benzene-C-H⋯O(coordinated), chloro-benzene-C-H⋯π(fused-benzene ring) as well as π(fused-benzene, chloro-benzene)-π(chloro-benzene) inter-actions [inter-centroid separations = 3.6460 (17) and 3.6580 (16) Å, respectively]. The layers inter-digitate along the b-axis direction and are linked by di-chloro-benzene-C-H⋯π(fused-benzene ring) and π-π inter-actions between fused-benzene rings and between chloro-benzene rings [inter-centroid separations = 3.6916 (16) and 3.7968 (19) Å, respectively] . Flat, supra-molecular layers are also found in the crystal of (II), being stabilized by π-π inter-actions formed between fused-benzene rings and between chloro-benzene rings [inter-centroid separations = 3.8889 (15) and 3.8889 (15) Å, respectively]; these stack parallel to [10] without directional inter-actions between them. The analysis of the respective calculated Hirshfeld surfaces indicate diminished roles for H⋯H contacts [26.2% (I) and 30.5% (II)] owing to significant contributions by Cl⋯H/H⋯Cl contacts [25.8% (I) and 24.9% (II)]. Minor contributions by Cl⋯Cl [2.2%] and Cu⋯Cl [1.9%] contacts are indicated in the crystals of (I) and (II), respectively. The inter-action energies largely arise from dispersion terms; the aforementioned Cu⋯Cl contact in (II) gives rise to the most stabilizing inter-action in the crystal of (II).