Monomeric octahedral bismuth(III) benzaldehyde-N-1-alkyl thiosemicarbazones: Synthesis, characterization and biological properties

Abstract

Due to their chemical and biological properties, the interest in thiosemicarbazones and their metal complexes is increasing day by day. In this study, the effect of the substituents at the N-1 atoms of the thiosemicarbazones and the effect of halogen atoms on the type and biological properties of bismuth(III) complexes is investigated. The reactions of bismuth(III) halide with a series of benzaldehyde-N-1-alkyl-thiosemicarbazones in 1:3 M ratio yield bismuth(III) halide complexes: {BiBr3(eta(1)-S-Hbztsc)3} (1), {BiCl3(eta(1)-S-Hbzmtsc)(3)} (2), {BiBr3(eta(1)-S-Hbzmtsc)(3)} (3), {[BiCl3(eta(1)-S-Hbzetsc)(3)].CH3OH} (4) and {BiBr3(eta(1)-S-Hbzetsc)(3)} (5). Complexes 1-5 were characterized by a number of different spectroscopic methods. The crystal structures of complexes 1-5 and the free ligand benzaldehyde-N-methyl-thiosemicarbazone were determined by X-ray diffraction. Complexes 1-5 were tested for their in vitro cytotoxic activity against human breast adenocarcinoma (MCF-7) cell line. Complexes 1-5 showed low cytotoxic activity. The antibacterial activities of 1-5 and their free ligands against four strains bacteria of Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli have been examined. The results indicated that bismuth(III) complexes 1-5 are most active against E. coli and, among them, complex 4 exhibits the highest activity. Lipoxygenase (LOX) inhibitory activity of the bismuth(III) halide complexes 1-5 and the free ligands has been detected experimentally. The IC50 values indicate that bismuth(III) halide complexes 1-5 have a higher enzyme inhibition potential than free ligands and cisplatin.