O2 reduction by a functional heme/nonheme bis-iron NOR model complex.

O(2) reactivity of a functional NOR model is investigated by using electrochemistry and spectroscopy. The electrochemical measurements using interdigitated electrodes show very high selectivity for 4e O(2) reduction with minimal production of partially reduced oxygen species (PROS) under both fast and slow electron flux. Intermediates trapped at cryogenic temperatures and characterized by using resonance Raman spectroscopy under single-turnover conditions indicate that an initial bridging peroxide intermediate undergoes homolytic O--O bond cleavage generating a trans heme/nonheme bis-ferryl intermediate. This bis ferryl species can oxygenate 2 equivalents of a reactive substrate.