Biological activity of complexes derived from thiophene-2-carbaldehyde thiosemicarbazone. Crystal structure of [Ni(C 6H 6N 3S 2) 2]

The crystal structure of [Ni(L III) 2] ( 1), where HL III = thiophene-2-carbaldehyde thiosemicarbazone, consists of monomeric entities where the nickel(II) ions exhibit distorted square planar geometry. The two bidentate thiosemicarbazone ligands are centrosymmetric. C⋯S van der Waals’ links and nonbonded intramolecular interactions are present in the structure. The biological activity of 1 is compared to that of the free ligand, and the cobalt(III) ( 2) and copper(II) ( 3) derivatives. The observed order of cytotoxicity against melanoma B16F10 and Friend erythroleukemia cells is: 1≤ligand< 2< 3. A structure–activity correlation using Extended-Hückel MO calculations is described.