Synthesis, characterization, DNA/protein binding and in vitro cytotoxic evaluation of new Ru(III) complexes containing aroylhydrazone ligands: Does hydrogen bonding influence the coordination behavior of hydrazones?

A new set of ruthenium(III) aroylhydrazone complexes [RuCl2(PPh3)(2)(HL1)] (1) and [RuCl(PPh3)(2)(L-2)] (2) were synthesized by reacting salicylaldehyde p-toluic acid hydrazone (H2L1) or 2-hydroxy-acetophenone p-toluic acid hydrazone (H2L2) and [RuCl3(PPh3)(3)] precursor complex and characterized. Single crystal X-ray diffraction data of these complexes revealed a distorted octahedral geometry around ruthenium ions fulfilled by NOP2Cl2 atoms and NO2P2Cl atoms, respectively. Though the ligands look similar in respect of structure and donor sites, the existence of H-bonding between the phenolic -OH and N2 nitrogen of the coordinated ligand H2L1 as revealed by the single crystal data of complex 1 is attributed to the non-involvement of the hydroxyl group in coordination to the ruthenium ion which is in sharp contrast to the behaviour exhibited by the ligand H2L2 in complex 2. As a result, the ligand H2L1 acted as a monobasic bidentate against the dibasic tridentate behaviour of the ligand H2L2. Binding interactions of these complexes with calf thymus-DNA (CT-DNA) estimated by absorption and emission spectroscopy did demonstrate the intercalative mode of binding. The capability of complexes 1 and 2 to bind with bovine serum albumin (BSA) protein was monitored by quenching of tryptophan and tyrosine residues using UV-Vis, fluorescence and synchronous fluorescence methods. Further, in vitro cytotoxicity of the complexes was carried out using MTT, lactate dehydrogenase (LDH), Nitric oxide (NO), reactive oxygen species (ROS) and propidium iodide (PI) staining assays against non-small cell lung cancer cell line (A549). () 2015 Elsevier B.V. All rights reserved.