New Ru(II)–dmso complexes with heterocyclic hydrazone ligands towards cancer chemotherapy

• Published in: Polyhedron 2008-05, Vol.27 (7), p.1917-1924
• Main Authors: Mahalingam, Viswanathan, Chitrapriya, Nataraj, Fronczek, Frank R., Natarajan, Karuppannan
• Format: Article
• Language: English
• Subjects: Antibacterial activity; Cyclic voltammetry; DNA-binding; Hydrazone ligands; Ru(II)–dmso complexes; Trans influence
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2008.02.036

A series of new Cl–Ru(II)–dmso complexes containing heterocyclic hydrazone ligands have been synthesized and characterized. The hydrazone ligands behave as neutral bidentate ligands. The redox properties of the complexes were studied by cyclic voltammetry. The substituents present in the hydrazone ligands affect the redox behavior. The antibacterial activity of the ligands and the complexes were studied in terms of minimum inhibitory concentration (MIC). The complexes were found to bind Herring sperm ds DNA in mixed modes. The synthesis and characterization of ruthenium(II) complexes, [RuCl 2(dmso) 2(bfmh)] ( 1; dmso = dimethyl sulfoxide, bfmh = benzoic acid furan-2-ylmethylene-hydrazide), [RuCl 2(dmso) 2(btmh)]( 2; btmh = benzoic acid thiophen-2-ylmethylene-hydrazide), [RuCl 2(dmso) 2(bfeh)]( 3; bfeh = benzoic acid (1-furan-2-yl-ethylidene)-hydrazide) and [RuCl 2(dmso) 2(bpeh)]( 4; bpeh = benzoic acid (1-pyridin-2-yl-ethylidene)-hydrazide) are described. The ligands, when treated with either cis-[RuCl 2(dmso) 4] or trans(Cl)–[RuCl 2(dmso) 2(bpy)], resulted in the same products. This has been confirmed by IR spectra and single crystal X-ray diffraction studies. The redox behaviors of the complexes have been found to be strongly dependent on the electronic nature of the moieties present in the hydrazone ligands. The binding of the complexes to Herring sperm DNA has been studied by absorption titration and cyclic voltammetry. But, due to the random change in the absorption on the addition of DNA, only a qualitative result rather than a quantitative result has been obtained. All the complexes have been found to bind DNA through different modes to different extents. The antibacterial properties of the ligands and the complexes have been studied against five pathogenic bacteria and also the minimum inhibitory concentrations (MIC) of all the ligands and complexes 2 and 4 have been evaluated.