Ruthenium hydrazone complexes with 1:1 and 1:2 metal-ligand stoichiometry: a comparison of biomolecular interactions and in vitro cytotoxicities

Two ruthenium(II) complexes [(RuCl)-Cl-II(PPh3)(2)(L)] (1) and [Ru-II(L)(2)] (2) were synthesized by reacting [RuCl2(PPh3)(3)] and thiophene-2-carboxylic acid (1-pyridine-2-yl-ethylidene)-hydrazide (HL) in methanol-chloroform, and characterized by elemental analysis and spectral and XRD data. The ratio of ligand to metal is 1:1 in the former complex and 2:1 in the latter. Interaction of these complexes with CT-DNA was studied using absorption and emission spectral studies; these show that both the complexes interact with CT-DNA through intercalative modes of interaction. Their BSA-binding activity results indicated the operation of static quenching mechanism and stronger binding of tryptophan residues than tyrosine residues. In vitro cytotoxicity assays against HeLa and MCF-7 cell lines showed better activity of both the complexes compared to the standard drug cisplatin. Overall, the activity of complex 2 with two units of coordinated ligand showed better activity than the other one.