Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: Synthesis, structural characterization and biological studies

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO2(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV–vis, ESR, 1H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H4L1) and the semicarbazone (H4L2) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO2(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H3L3) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H4L1 ligand showed a higher antibacterial effect than the free ligand while the other ligands (H4L2 and H3L3) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.