Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates

Abstract

Fe III –hypohalite complexes have been implicated in a wide range of important enzyme‐catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post‐translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme Fe III –hypohalite intermediates of possible relevance to iron halogenases. We show that Fe III ‐OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo‐ESIMS. DFT methods rationalize the pathways to the formation of the Fe III ‐OCl, and ultimately Fe IV O, species and provide indirect evidence for a short‐lived Fe II ‐OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases.