A Potential Visible-Light NO Releaser: Synthesis, Reactivity and Vasodilator Properties

The cis-[Ru(bpy)2(4-bzpy)(NO)](PF6)3 complex was prepared (4-bzpy = 4-benzoylpyridine), and characterized by UV-visible, infrared and nuclear magnetic resonance (NMR) spectroscopies and electrochemical techniques. The reaction with cysteine was preliminarily investigated, aiming to shed light on the potential biological mechanism for NO or HNO release mediated by thiols. Furthermore, photochemical behavior of cis-[Ru(bpy)2(4-bzpy)(NO)](PF6)3 was studied, where it was observed NO release upon ultraviolet, blue and green light irradiations. This latter long wavelength showed still good efficiency, which has not been reported for this type of complex. This feature is very important for a potential application in phototherapy. Additionally, vasorelaxant activity was investigated in rat-isolated aorta. This compound exhibited a greater maximum efficacy than sodium nitroprusside (SNP) as a blood vessel relaxant. Nevertheless, the EC50 for SNP (13.3 nmol L-1) was 52-fold smaller than the EC50 for cis-[Ru(bpy)2(4-bzpy)NO](PF6)3 (690 nmol L-1). Altogether, these results suggest this complex is a promising NO donor agent deserving further biological studies.