Synthesis, characterization, photoluminescence and electrochemical studies of Ni^II, Cu^II, Zn^II, Cd^II and Pd^II complexes of the bidentate S-hexyl-β-N-(2-thienyl)methylenedithiocarbazate ligand

Divalent metal complexes of empirical formulation [ML₂] (where M(II) = Ni, Cu, Zn, Cd and Pd; L = anionic form of the 2-thiophenecarboxaldehyde Schiff base of S-hexyldithiocarbazate) have been synthesized and characterized by physico-chemical techniques. Magnetic and spectroscopic data give support to a square-planar coordination geometry for these complexes with the exception of the Zn^II and Cd^II species. The single crystal structures of the [NiL₂] and [CuL₂] complexes have been determined by X-ray diffraction analysis. In both the structurally characterized complexes the uninegatively charged bidentate ligands coordinate the metal (II) ion via the azomethine nitrogen and the thiolate sulfur atoms in a trans-planar configuration. The electrochemical properties of the Cu(II) complex have been studied by cyclic voltammetry. The voltammogram shows quasi-reversible, one electron redox process. Metal-mediated fluorescence quenching is observed on complexation of HL with all metal ions.