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 · NHq (quinonediimine) and NH2.NH2cat (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 · NHq and NH2 · NH2cat, respectively, and 0.0065 ± 0.001 mol Einstein−1 for light irradiation at 532 nm for [Ru(NH · 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 · NHq)(tpy)NO]3+ complex was evaluated and compared with sodium nitroprusside (SNP). The results showed very similar vasodilator power between both species.