Synthesis, structure and in vitro biological activity of pyridoxal N(4)-substituted thiosemicarbazone cobalt(III) complexes

Cobalt(III) complexes containing pyridoxal N(4)-substituted thiosemicarbazone ligands with the composition [Co(HL1−2·Cl)(HL1−2·H2O)] (1–2) have been synthesized from the reaction of [CoCl2(PPh3)2] and pyridoxal N-methyl-thiosemicarbazone hydrochloride (H3L1·Cl)/pyridoxal N-phenyl-thiosemicarbazone hydrochloride (H3L2·Cl). The richness of the coordination chemistry of this ligand is highlighted by the modulation of its charge from neutral (H3L·Cl) (L) to dianionic (HL·Cl) (L2−) and monoanionic forms (HL·H2O) (L−) and coordinated as tridentate binegative mode around cobalt(III) ion by forming neutral complex. The new complexes were characterized by various analytical and spectroscopic techniques (IR, electronic, 1H NMR and ESI-Mass). The X-ray crystal structure of the complex 2, demonstrated distorted octahedral coordination geometry around the metal centre. Further, the investigation of effect of substitution (CH3 or C6H5) on terminal N(4)-nitrogen of thiosemicarbazone exhibited its influence on the potential binding and cleavage ability with DNA, BSA binding, free radical scavenging and cytotoxicity.