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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.

SUBMITTER: Krzystek J

PROVIDER: S-EPMC8966373 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Determination by high-frequency and -field EPR of zero-field splitting in iron(IV) oxo complexes: implications for intermediates in nonheme iron enzymes.

Krzystek J J England Jason J Ray Kallol K Ozarowski Andrew A Smirnov Dmitry D Que Lawrence L Telser Joshua J

Inorganic chemistry 20080404 9

[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. ...[more]

PMID: 18386920

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Nonheme oxo-iron(IV) intermediates form an oxyl radical upon approaching the C-H bond activation transition state.

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