Copper(II) complexes with tridentate N-(benzoyl)-N′-(salicylidine)-hydrazine and monodentate N-heterocycles: Investigations of intermolecular interactions in the solid state

Ternary copper(II) complexes having the general formula [Cu(bhs)(hc)], with a tridentate Schiff base, N-(benzoyl)-N′-(salicylidine)-hydrazine (H2bhs) and monodentate N-heterocycles (hc=3,5-dimethylpyrazole, pyrazole, imidazole, and pyridine), are described. The complexes were characterized by elemental analysis, spectroscopic and cryomagnetic measurements and X-ray crystallography. Analytical data, infrared and electronic spectral features and molar conductivity values are consistent with the proposed molecular formula and the +2 oxidation state of the metal ion in these complexes. Cryomagnetic and EPR spectral measurements showed weak antiferromagnetic spin-exchange in all four complexes. In each complex, the metal ion is in N2O2 square-plane constituted by the phenolate-O, the imine-N, and the deprotonated amide-O donor bhs2− and the sp2 N-donor neutral heterocycle. In the solid state, the complexes having 3,5-dimethylpyrazole, imidazole, and pyridine as the heterocyclic ligand, exist as centrosymmetric dimeric species due to weak apical coordination of the metal bound phenolate-O. On the other hand, only one of the two molecules present in the asymmetric unit of the complex containing pyrazole forms the centrosymmetric dimeric species due to weak apical coordination of the metal bound amide-O. In the crystal lattice, intermolecular π-π, C-H⋯π, C-H⋯N, O-H⋯N and N-H⋯O interactions involving the complex and the solvent molecules lead to one- and two-dimensional supramolecular structures.