Synthesis, crystal structure, deoxyribose nucleic acid interaction and antitumor activity of some thiosemicarbazonatomolybdenum(VI)

Abstract

Four dioxomolybdenum(VI) complexes were synthesized by reacting [MoO2(acac)2] with thiosemicarbazone ligands derived from 5-chloro-2-hydroxybenzaldehyde (H2L1), 2-hydroxy-5-methylbenzaldehyde (H2L2), 3-tert-butyl-2-hydroxybenzaldehyde (H2L3), or 2,3-dihydroxybenzaldehyde (H2L4). In all the complexes, the ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography showed that the distorted octahedral coordination of molybdenum atom is completed by methanol molecule (D) as in [MoO2(L1D)], [MoO2(L2D)], and [MoO2(L3D)], or by an ethanol molecule as in [MoO2(L4D)]. The molecular structures of H2L2, H2L3, and all synthesized complexes were determined via single crystal X-ray crystallography. The binding properties of the ligand and the complexes with calf thymus DNA were analyzed by UV, fluorescence titration, and viscosity measurements. Gel electrophoresis shows that all complexes can cleave the pBR322 plasmid DNA. The cytotoxic properties of the complexes were studied against human colorectal cell lines. All complexes showed strong antiproliferative activities in the relative order [MoO2(L3D)]>[MoO2(L1D)]∼[MoO2(L2D)]>[MoO2(L4D)] with IC50 values of 3.2, 4.5, 4.6, and 6.4μM, respectively. The complexes exhibited greater pronounced activity than the standard reference drug, 5-fluorouracil, did (IC50=7.3μM). These studies demonstrate the potential application of dioxomolybdenum(VI) complexes in chemotherapy.