Dimethyl sulfoxide ruthenium(II) complexes of thiosemicarbazones and semicarbazone: Synthesis, characterization and biological studies

In an attempt to synthesize Ru(II)-dmso-thiosemicarbazone complexes, a series of carbonyl compounds were selected to condense with thiosennicarbazide in ethanol in order to get the respective thiosemicarbazone ligand as the first step. All the selected carbonyl compounds yielded the expected thiosemicarbazone ligand, but the product obtained by the reaction of benzaldehyde with thiosemicarbazide in ethanol was found to show sharp IR peak characteristic of C=O group and thought to be benzaldehyde semicarbazone. When the ligands were treated with cis-[RuCl2(dmso)(4))] in ethanol, all the ligands yielded thio-semicarbazone complexes, while the suspected semicarbazone ligand resulted in orange-yellow crystalline product which has been found to be a semicarbazone complex by XRD studies. A mechanism has been proposed for the conversion of C=S to C=O during ligand preparation, which involves the role of adventitious water in ethanol. All the complexes were characterized by analytical and spectroscopic (IR, UV-Vis and H-1 NMR) methods. The redox behaviors of the complexes were studied by cyclic voltammetry. The preliminary DNA-binding ability of the complexes was studied by recording electronic absorption spectra of the complexes in presence of herring sperm DNA. Antibacterial activities of the complexes were also been evaluated against five pathogenic bacteria. (C) 2008 Elsevier Ltd. All rights reserved.