Synthesis and characterization of thiosemicarbazonato molybdenum(VI) complexes: In vitro DNA binding, cleavage, and antitumor activities

Abstract

Four dioxomolybdenum(VI) complexes were synthesized by the reaction of [MoO2(acac)2] with thiosemicarbazone ligands derived from 5-chloro-2-hydroxy-benzaldehyde (1), 2-hydroxy-5-methoxybenzaldehyde (2), 2-hydroxy-5-methylbenzaldehyde (3), or 5-tert-butyl-2-hydroxybenzaldehyde (4). In all complexes, the ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography results show that the distorted octahedral coordination of the molybdenum atom is completed by a methanol molecule (D), as in 1a, 3a, and 4a, or by H2O, as in 4a. The molecular structures of 1, 2, and the complexes were determined by single-crystal X-ray crystallography. The binding properties of the ligand and complexes with calf thymus DNA (CT DNA) were investigated by UV titration, fluorescence titration, and viscosity measurements. Gel electrophoresis assay results show that the complexes can cleave the pBR 322 plasmid DNA. The cytotoxic activities of the complexes were investigated against human colorectal cell lines. All complexes showed high anticancer activities in the order, 4a>1a≫3a>2a, according to their IC50 values (3.4, 3.5, 6.4, and 6.9μM, respectively).