title: Prediction of high-valent iron K-edge absorption spectra by time-dependent density functional theory.
abstract: In recent years, a number of high-valent iron intermediates have been identified as reactive species in iron-containing metalloproteins. Inspired by the interest in these highly reactive species, chemists have synthesized Fe(IV) and Fe(V) model complexes with terminal oxo or nitrido groups, as well as a rare example of an Fe(VI)-nitrido species. In all these cases, X-ray absorption spectroscopy has played a key role in the identification and characterization of these species, with both the energy and intensity of the pre-edge features providing spectroscopic signatures for both the oxidation state and the local site geometry. Here we build on a time-dependent DFT methodology for the prediction of Fe K- pre-edge features, previously applied to ferrous and ferric complexes, and extend it to a range of Fe(IV), Fe(V) and Fe(VI) complexes. The contributions of oxidation state, coordination environment and spin state to the spectral features are discussed. These methods are then extended to calculate the spectra of the heme active site of P450 Compound II and the non-heme active site of TauD. The potential for using these methods in a predictive manner is highlighted.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chandrasekaran
authors.forename: S Chantal E
authors.initials: SC
authors.lastname: Stieber
authors.forename: Terrence J
authors.initials: TJ
authors.lastname: Collins
authors.forename: Lawrence
authors.initials: L
authors.lastname: Que
authors.forename: Frank
authors.initials: F
authors.lastname: Neese
authors.forename: Serena
authors.initials: S
authors.lastname: DeBeer
mesh_terms: D020134:Catalytic Domain; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D006899:Mixed Function Oxygenases / Q000737:chemistry; D008958:Models, Molecular; D011789:Quantum Theory; D013997:Time Factors; D056928:X-Ray Absorption Spectroscopy
chemical_list: D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D007501:Iron; D006899:Mixed Function Oxygenases; C433064:taurine-alpha-ketoglutarate dioxygenase