Synthesis, characterization, DNA binding and catalytic activities of Ru(III) complexes

A new series of azo dye ligands 4-(4-hydroxy-5-(aryldiazenyl)-2-thioxothiazol-3(2H)-yl)benzenesulfonamide (HLn) were synthesized by the coupling of 3-sulfamoylphenylrhodanine with aniline and its p-derivatives. These ligands and their Ru(III) complexes of the type trans-[Ru(Ln)2(bipy)]Cl were characterized by elemental analysis, IR, 1H NMR and UV-Visible spectra as well as magnetic and thermal measurements. The molar conductance measurements proved that all the complexes are electrolytes. IR spectra show that the ligands (HLn) act as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (NN-) and oxygen atom of the deprotonated OH group of the rhodanine moiety, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The molecular and electronic structures of the ligands (HLn) were also studied using quantum chemical calculations. The calf thymus DNA binding activity of the ligands (HLn) was studied by absorption spectra measurements. The Ru(III) complexes were tested as a catalysts for the dehydrogenation of benzylamine to benzonitrile with N-methylmorpholine-N-oxide as co-oxidant at room temperature.