New Ru(II)–DMSO complexes of ON/SN chelates: Synthesis, behavior of Schiff bases towards hydrolytic cleavage of CN bond, electrochemistry and biological activities

The reaction of cis-[RuCl2(DMSO)4] with salicylaldehyde semicarbazone in ethanol resulted in the chemoselective cleavage of the CN bond of the Schiff base, forming a complex in which the semicarbazide remains coordinated to the metal, as observed previously with trans-[RuCl2(DMSO)4]. In another set of reactions of cis-[RuCl2(DMSO)4] with 4-aminoantipyrine derivatives of salicylaldehyde, 2-hydroxy-1-naphthaldehyde and o-vanillin, CN cleavage was observed in all three cases yielding the same compound, [RuCl2(DMSO)2(4-aminoantipyrine)]. However, when the reactions, under the same experimental conditions, were extended to unsubstituted/N-substituted thiosemicarbazones of salicylaldehyde and 2-hydroxy-1-naphthaldehyde, no cleavage was observed. All the new complexes were characterized by analytical and spectroscopic techniques. The structures of two of the complexes, [RuCl2(DMSO)2(semicarbazide)]·2H2O and [RuCl2(DMSO)2(4-aminoantipyrine)], were determined by single crystal XRD and are in support of the cleavage. The electrochemistry of the complexes was studied by cyclic voltammetry. Further, the preliminary DNA-binding ability and antibacterial activity of the complexes were studied.

New Ru(II)–DMSO complexes of ON/SN chelates have been synthesized and characterized. The reaction of cis-[RuCl2(DMSO)4] with different o-hydroxy Schiff base ligands of 4-aminoantipyrine in ethanol yielded the same compound, [RuCl2(DMSO)2(4-aminoantipyrine)] through the hydrolytic cleavage of the CN bond of the Schiff bases. This phenomenon was not observed for similar thiosemicarbazone ligands. This observation has been explained on the basis of ketoamine–enolimine tautomerism. Electrochemistry, DNA-binding ability (preliminary) and antibacterial activity of the new complexes have also been studied.Figure optionsDownload as PowerPoint slide