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

Two non-heme ironnitrosyl species, [Fe-2(N-Et-HPTB)(O2CPh)(NO)(2)](BF4)(2) (1a) and [Fe-2(N-Et-HPTB)(DMF)(2)(NO)(OH)](BF4)(3) (2a), 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 1a but not 2a. Low-temperature FTIR photolysis experiments with 1a 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 nu(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.