Influence of ancillary ligand L in the nitric oxide photorelease by the [Ru(L)(tpy)NO]3+ complex and its vasodilator activity based on visible light irradiation

The photochemical and pharmacological studies of the novel [Ru(L)(tpy)NO](3+) L = bpy (2,2'-bipyridine), NH center dot NHq (quinonediimine) and NH2.NH(2)cat (o-phenylenediamine) were investigated in aqueous medium. The synthesized nitrosyl ruthenium complexes showed nitric oxide (NO) release under light irradiation at 355 nm for [Ru(L)(tpy)NO](3+) complex with quantum yield of 0.14 +/- 0.02, 0.47 +/- 0.03 and 0.46 +/- 0.02 mol Einstein(-1) for L = bpy, NH center dot NHq and NH2 center dot NH(2)cat, respectively, and 0.0065 +/- 0.001 mot Einstein(-1) for light irradiation at 532 nm for [Ru(NH center dot NHq)(tpy)NO](3+) complex. The photochemical pathway at 355 nm light irradiation was described as a multi-step mechanism, although at 532 nm it was better attributed to a photo-induced electron transfer. The vasorelaxation induced by NO release produced by light irradiation in visible region from physiological solution of [Ru(NH center dot NHq)(tpy)NO](3+) complex was evaluated and compared with sodium nitroprusside (SNP). The results showed very similar vasodilator power between both species. (c) 2006 Elsevier B.V. All rights reserved.