Synthesis and spectroscopic properties of copper(II) complexes derived from thiophene-2-carbaldehyde thiosemicarbazone. Structure and biological activity of [Cu(C6H6N3S2)2].

The synthesis, structure and spectroscopic properties on complexes with the formula Cu(Lm)2] (1) and Cu(NO3)2(HLm)2 (2), where HLm = thiophene-2-carbaldehyde thiosemicarbazone, have been developed. The molecular structure of compound 1 consists of monomeric entities. The copper(II) ions exhibit distorted square-planar geometry with both bidentate thiosemicarbazone ligands placed in a centrosymmetric way. Metal to ligand pi-backdonation is proposed to explain several structural and spectroscopic features in these complexes. The EPR spectra of compound 1 show an orthorhombic g tensor indicating the presence of weak magnetic exchange interactions. The reaction of compound 1 with glutathione causes the reduction of the metal ion and the substitution of the thiosemicarbazone ligand by the thiol ligand. This mechanism seems to be related to the cytotoxicity of this complex against Friend Erithroleukemia cells (FLC) and melanome B16F10 cells.