Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O-2 and NO and Mechanistic Insights into Metal-Mediated Peroxynitrite Decomposition

We report the formation of a new copper peroxynitrite (PN) complex [Cu-II(TMG(3)tren)(kappa(1)-OONO)](+) (PN1) from the reaction of [Cu-II(TMG(3)tren)(O-2(.-))](+) (1) with NO(g). at -125 degrees C. The first resonance Raman spectroscopic characterization of such a metal-bound PN moiety supports a cis kappa(1)-(-OONO) geometry. PN1 transforms thermally into an isomeric form (PN2) with kappa(2)-O,O '-(-OONO) coordination, which undergoes O-O bond homolysis to generate a putative cupryl (LCuII-O-.) intermediate and NO2.. These transient species do not recombine to give a nitrato (NO3-) product but instead proceed to effect oxidative chemistry and formation of a Cu-II-nitrito (NO2-) complex (2).