Light-Induced N₂O Production from a Non-heme Iron–Nitrosyl Dimer

Abstract

Two non-heme iron–nitrosyl species, [Fe₂(<i>N</i>‑Et‑HPTB)­(O₂CPh)­(NO)₂]­(BF₄)₂ (<b>1a</b>) and [Fe₂(<i>N</i>‑Et‑HPTB)­(DMF)₂(NO)­(OH)]­(BF₄)₃ (<b>2a</b>), are characterized by FTIR and resonance Raman spectroscopy. Binding of NO is reversible in both complexes, which are prone to NO photolysis under visible light illumination. Photoproduction of N₂O occurs in high yield for <b>1a</b> but not <b>2a</b>. Low-temperature FTIR photolysis experiments with <b>1a</b> in acetonitrile do not reveal any intermediate species, but in THF at room temperature, a new {FeNO}⁷ species quickly forms under illumination and exhibits a ν­(NO) vibration indicative of nitroxyl-like character. This metastable species reacts further under illumination to produce N₂O. A reaction mechanism is proposed, and implications for NO reduction in flavo­diiron proteins are discussed