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

The reaction of cis-[RuCl2(DMSO)(4)] with salicylaldehyde semicarbazone in ethanol resulted in the chemo-selective cleavage of the C=N 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, C=N 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)(semi-carbazide)]center dot 2H(2)O 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. (C) 2010 Elsevier Ltd. All rights reserved.