(Pyridyl)benzoazole ruthenium(III) complexes: Kinetics of ligand substitution reaction and potential cytotoxic properties

The present work investigates the kinetics of ligand substitution reaction and anticancer activities of the complexes, [{2-(2-pyridyl) benzimidazole} RuCl3] (C1), [{2-(2-pyridyl) benzoxazole} RuCl3] (C2), [{2-(2-pyridyl) benzothiazole} RuCl3] (C3) and [{1-propyl-2-(pyridin-2-yl)-H-benzoimidazole} RuCl3] (C4). The substitution kinetics reaction of the complexes with the three bio-relevant nucleophiles, viz.: thiourea (TU), 1, 3-dimethyl-2-thiourea (DMTU) and 1, 1, 3, 3-tetramethyl-2-thiourea (TMTU) was investigated under pseudo first-order conditions as a function of concentration and temperature using UV-Visible spectrophotometer. The substitution of the coordinated chloride was controlled by the electronic effect. The order of reactivity of the complexes with the nucleophiles is in the form C1 > C2 > C3 > C4 which is in line with the density functional theory (DFT) studies. The complexes showed minimal anticancer activity against the HeLa cell line, which is in contrast to the molecular docking experiments that exhibited stronger DNA binding affinities.