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Paper
Dalton Trans., 2008, 4282 - 4287, DOI: 10.1039/b803441a
The inducing NO-vasodilation by chemical reduction of coordinated nitrite ion in cis-[Ru(NO2)L(bpy)2]+ complex
Zênis Novais da Rocha, Mario Sérgio Pereira Marchesi, Josiane Cristina Molin, Claure N. Lunardi, Katrina M. Miranda, Lusiane Maria Bendhack, Peter C. Ford and Roberto Santana da Silva
The synthesis of [Ru(NO2)L(bpy)2]+ (bpy = 2,2
-bipyridine and L = pyridine (py) and pyrazine (pz)) can be accomplished by addition of [Ru(NO)L(bpy)2](PF6)3 to aqueous solutions of physiological pH. The electrochemical processes of [Ru(NO2)L(bpy)2]+ in aqueous solution were studied by cyclic voltammetry and differential pulse voltammetry. The anodic scan shows a peak around 1.00 V vs. Ag/AgCl attributed to the oxidation process centered on the metal ion. However, in the cathodic scan a second peak around -0.60 V vs. Ag/AgCl was observed and attributed to the reduction process centered on the nitrite ligand. The controlled reduction potential electrolysis at -0.80 V vs. Ag/AgCl shows NO release characteristics as judged by NO measurement with a NO-sensor. This assumption was confirmed by ESI/MS+ and spectroelectrochemical experiment where cis-[Ru(bpy)2L(H2O)]2+ was obtained as a product of the reduction of cis-[RuII(NO2)L(bpy)2]+. The vasorelaxation observed in denuded aortic rings pre-contracted with 0.1 
mol L-1 phenylephrine responded with relaxation in the presence of cis-[RuII(NO2)L(bpy)2]+. The potential of rat aorta cells to metabolize cis-[RuII(NO2)L(bpy)2]+ was also followed by confocal analysis. The obtained results suggest that NO release happens by reduction of cis-[RuII(NO2)L(bpy)2]+ inside the cell. The maximum vasorelaxation was achieved with 1 × 10-5 mol L-1 of cis-[RuII(NO2)L(bpy)2]+ complex.
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