Novel Ru(II) oximato complexes with silent oxygen atom: Synthesis, chemistry and biological activities

A series of octahedral complexes, [Ru(CO)(EPh3)2(bhmh)] (E = P or As; H2bhmh = benzoic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide), [Ru(CO)(EPh3)2(ihmh)] (H2ihmh = isonicotinic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide), [Ru(CO)(EPh3)2(hhmh)] (H2hhmh = 2-hydroxy-benzoic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide) have been prepared by a facile procedure. X-ray structure determination of three of the complexes revealed that the hydrazone ligand coordinates through the imine and the oxime nitrogen and the amide oxygen atoms. In all the complexes, the N–OH moiety of the oxime is deprotonated to give an N–O− species and this oxygen atom did not coordinate to the central metal atom. The oxidation–reduction processes for each of these complexes have been determined in CH3CN by cyclic voltammetry. The complexes displayed two oxidation couples and one irreversible reduction response between +1.6 and −1.6 V. The trend in the half wave potentials reflects the electronic nature of the hydrazone ligand. Antibacterial activity of the ligands and the complexes has been evaluated against five pathogenic bacteria. The binding of the complexes with herring sperm DNA has also been investigated by UV–Vis spectroscopy and cyclic voltammetry.