Nitric oxide is produced in mammals in part to help defend against invading foreign pathogens, and to combat this defense mechanism, certain pathogens express nitric oxide reductases (NORs), which convert NO to N2O via: 2NO + 2e- + 2H+→ N2O + H2O. Microbes such as cyanobacteria use a flavin containing diiron protein (FDPnor) for the reduction of NO to N2O. A number of questions remain regarding the mechanism of FDPnor, including the timing of electron-transfer to FeNO intermediates. This presentation will describe a new mononuclear nonheme iron(II) complex that has been designed to bind and activate NO. The synthesis and characterization of a new iron-nitrosyl complex, [Fe(NO)(Me3TACN)((OSiPh2)2O)], is reported. Vibrational analysis by resonance Raman spectroscopy shows that this {FeNO}7 complex ({FeNO}n: Enemark-Feltham notation; n = Fe d-electrons + NO (π*) electrons) has a highly activated N–O bond (ν(N–O) = 1680 cm-1). This N-O stretch is remarkably close to that observed for the mononitrosyl intermediate in FDPnor (ν(N–O) = 1681 cm-1). The {FeNO}7 complex produces N2O in THF upon addition of H2O, providing a novel example of a mononuclear, nonheme {FeNO}7 complex that generates N2O in the absence of external reductants. The spectroscopic characterization (UV-vis, 1H-NMR, EPR, Mössbauer, X-ray absorption) of these species will be discussed, together with supporting density functional theory calculations.

N2O production from a nonheme mononuclear {FeNO}7 complex in the absence of an exogenous reductant

ACS Fall 2021

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