title: Determination by high-frequency and -field EPR of zero-field splitting in iron(IV) oxo complexes: implications for intermediates in nonheme iron enzymes.
abstract: [Fe(IV)O](2+) species have been implicated as the active form of many nonheme iron enzymes. The electronic structures of iron(IV) oxo complexes are thus of great interest. High-frequency and -field electron paramagnetic resonance is employed to determine accurately the spin Hamiltonian parameters of two stable complexes that contain the FeO unit: [FeO(TMC)(CH 3CN)](CF 3SO 3) 2, where TMC = tetramethylcyclam and [FeO(N4py)](CF 3SO 3) 2, where N4Py = bis(2-pyridylmethyl)bis(2-pyridyl)methylamine. Both complexes exhibit zero-field splittings that are positive, almost perfectly axial, and of very large magnitude: D = +26.95(5) and +22.05(5) cm (-1), respectively. These definitive experimental values can serve as the basis for further computational studies to unravel the electronic structures of such complexes.
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA.
authors.forename: J
authors.initials: J
authors.lastname: Krzystek
authors.forename: Jason
authors.initials: J
authors.lastname: England
authors.forename: Kallol
authors.initials: K
authors.lastname: Ray
authors.forename: Andrew
authors.initials: A
authors.lastname: Ozarowski
authors.forename: Dmitry
authors.initials: D
authors.lastname: Smirnov
authors.forename: Lawrence
authors.initials: L
authors.lastname: Que
authors.forename: Joshua
authors.initials: J
authors.lastname: Telser
mesh_terms: D003494:Cyclamates / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004798:Enzymes / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D019159:Nonheme Iron Proteins / Q000737:chemistry*; D010084:Oxidation-Reduction; D011725:Pyridines / Q000737:chemistry
chemical_list: D003494:Cyclamates; D004798:Enzymes; D058085:Iron Compounds; C431844:N4Py compound; D019159:Nonheme Iron Proteins; D011725:Pyridines