Singlet Molecular Oxygen: Not a Major Product of the Reaction between Tris(2,2'-bipyridine)ruthenium(3+) and Superoxide Radical Anions

Article abstract of DOI:10.1021/ja00216a018

Time-resolved infrared luminescence and computer-aided kinetic modeling have been used to demonstrate that singlet molecular oxygen, O2 (¹Δ_g), is not formed during the electron-transfer reaction between Ru(bpy)3³⁺ and O2^.- ions in aqueous media.This is in direct contrast to what has been claimed earlier.As far as we are able to determine, the only singlet oxygen formed photolytically in a reaction mixture containing Ru(bpy)3²⁺, MV²⁺, and O2 is that generated by energy transfer between Ru(bpy)3²⁺ and ground-state oxygen.Radiolytic and electrochemical measurements have established that the bleaching of the singlet oxygen trap ADPA^2-, which occurs with a quantum yield of 0.12+/-0.01 when H2O or D2O solutions containing Ru(bpy)3²⁺, MV²⁺, O2, and ADPA^2- are photolyzed is to be attributed to the oxidation of ADPA^2- by Ru(bpy)3³⁺; from the computer modeling of the system a rate constant value of ca. 10⁷ M^-1s^-1 for the latter reaction has been evaluated.