Investigation of a novel trinuclear μ-oxo ruthenium complex as a potential nitric oxide releaser for biological purposes

Abstract

The chemical properties of the trinuclear ruthenium complex [Ru3O(CH3COO)6(3-pic)2(NO)]PF6 (1, were 3-pic=3-picoline or 3-methylpyridine), its photochemical behavior and its ability as a vasorelaxing agent are reported in this work. It was shown that the unpaired electrons of NO and of the metal center [Ru3O]+ are tightly coupled, promoting an intermediate NMR profile between the oxidized (paramagnetic) and reduced (diamagnetic) [Ru3O]1+/0 species. From IR measurements, it was suggested that in trinuclear complexes, unlike other ruthenium compounds, the interaction of those unpaired electrons overcomes the effect of peripheral ligands and NO-backbonding on the ν(NO) frequency, which shows no dependence on the pKa values of pyridinic ligands. The photoinduced NO release was investigated by light irradiation at 337, 447, 532 and 660nm in phosphate buffer solution (pH 7.4), leading to the generation of gaseous NO0 and the solvated species [Ru3O(CH3COO)6(3-pic)2(H2O)]+ (2). Through amperometric and quimioluminescence measurements, the amount of NO(g) released were determined, showing dependence on the wavelength of irradiation. The ability of compound 1 as a vasorelaxing agent was also addressed. It was shown that, under ambient luminosity, compound 1 promotes 89% of relaxation in pre-contracted rat aorta. Molecular modeling of the novel nitrosyl, as well as characterization of the complexes [Ru3O(CH3COO)6(3-pic)2(L)]n, L=H2O, n=+1 (2), L=3-pic, n=+1 (3), L=CO, n=0 (4), are also reported.