Synthesis, characterization, redox property and biological activity of Ru(II) carbonyl complexes containing O,N-donor ligands and heterocyclic bases.

Stable ruthenium(II) carbonyl complexes having the general composition [RuCl(CO)(PPh3)(B)(L)] (where B=PPh3, pyridine, piperidine or morpholine; L=anion of bidentate Schiff bases (Vanmet, Vanampy, Vanchx)) were synthesized from the reaction of [RuHCl(CO)(PPh3)2(B)] with bidentate Schiff base ligands derived from condensation of o-vanillin with primary amines such as methylamine, 2-aminopyridine and cyclohexylamine. The new complexes were characterized by elemental analysis, IR, UV-Vis and 1H NMR spectral data. The redox property of the complexes were studied by cyclic voltammetric technique and the stability of the complexes towards oxidation were related to the electron releasing or electron withdrawing ability of the substituent in the phenyl ring of o-vanillin. An octahedral geometry has been assigned for all the complexes. In all the above reactions, the Schiff bases replace one molecule of PPh3 and hydride ion from the starting complexes, which indicate that the Ru-N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru-P. The Schiff bases and their ruthenium(II) complexes have been tested in vitro to evaluate their activity against bacteria, viz., Staphylococcus aureus (209p) and E. coli (ESS 2231).