Synthesis, characterization, density functional study and antimicrobial evaluation of a series of bischelated complexes with a dithiocarbazate Schiff base ligand

A nitrogen-sulfur Schiff base HL (1) derived from S-hexyldithiocarbazate and 4- methylbenzaldehyde has been reacted with different divalent metal ions in 2:1 molar ratio, producing neutral complexes (2–7) of general formula MIIL2 (where M =Ni, Cu, Zn, Cd, Pd and Pb). All compounds were characterized using established physico-chemical and spectroscopic methods. The single crystal structures of CuII and ZnII complexes are compared and discussed with those of NiII and PdII already reported by us, underlining the geometrical variations occurring in the HL ligand upon coordination. The metal complexes, as revealed by the X-ray diffraction analyses, show a square planar or tetrahedral coordination geometry, and in the former case either a cisoid or transoid configuration of chelating ligands. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations have been performed on the isolated cis/trans