SYNTHESIS, CHARACTERIZATION AND SUPEROXIDE-DISMUTASE MIMETIC ACTIVITYOF RUTHENIUM(III) OXIME COMPLEXES

Vicinal carbonyl-oxime and oxime-imine ligands were used in the synthe sis of new Ru-III oxime complexes and the isolated chelates were chara cterized by elemental analysis, electrical conductance and magnetic mo ment measurements. I.r., u.v.-vis. and e.s.r. spectroscopic analysis m ethods were also employed. The spectral data were utilized to compute the important ligand field parameters B, beta and Dq. The carbonyl-oxi me ligand coordinates through the nitrogen of =N-OH to form a five-mem bered chelate ring. Replacement of the C=O group by C=N-NH2 induces th e =N-OH group to coordinate through the oxygen, forming thereby a six- membered chelate ring. The quadridentate tetraaza ligand (L-7) coordin ates with Ru-III through its nitrogen donors in the equatorial positio n with loss of one of the oxime protons and concomitant formation of a n intramolecular hydrogen bond. The spectral and magnetic results sugg est a slightly distorted octahedral environment around the Ru-III ion. The superoxide dismutase (SOD) mimetic activity of the prepared compl exes was assessed for their ability to inhibit the reduction of nitrob lue tetrazolium (NBT). The results demonstrate that most of the comple xes have promising SOD-mimetic activity. A probable mechanism for the catalytic scavenging of O-2(-) by Ru-III oximes is proposed.