Detection of Ligand-Substitution Intermediates in the Photoreactions of Bis(2,2′-bipyridine)butanediamineruthenium(II) Complex Using Electrospray Ionization Mass Spectrometry

Abstract

Abstract The photolysis of [Ru(bpy)2(bn)]2+ (bpy = 2,2′-bipyridine, bn = 1,4-butanediamine) in acetonitrile and acetone by light of wavelength longer than 420 nm was studied by electrospray ionization mass spectrometry (ESI-MS). The results were different from those of two other amine complexes, [Ru(bpy)2(en)]2+ and [Ru(bpy)2(tn)]2+ (en = ethylenediamine and tn = 1,3-propanediamine). An analysis of the irradiation time course revealed that one end of the bn ligand is quickly dissociated to form a solvent-coordinated complex, [Ru(bpy)2(bn)(AN)]2+ (AN = acetonitrile), and its protonated complex, [Ru(bpy)2(bn + H)(AN)]3+. These solvent-coordinated complexes were not observed in the photochemical reactions of the en or tn complex. The difference in photolysis is due to the fact that the coordination of the bn ligand in [Ru(bpy)2(bn)]2+ is less stable than the en or tn ligand. Both the en and tn complexes formed oxygenated complexes, while the bn complex did not form such a complex. This can be explained by the incorporation of singlet oxygen during the photochemical reaction.