Electron Paramagnetic Resonance and Mössbauer Spectroscopy and Density Functional Theory Analysis of a High-Spin' Fe-Oxo Complex.
High-spin Fe-oxo species are known to be kinetically competent oxidants in non-heme iron enzymes. The properties of these oxidants are not as well understood as the corresponding intermediate-spin oxidants of heme complexes. The present work gives a detailed characterization of the structurally simi...
| Publicado en: | Journal of the American Chemical Society Vol. 134; no. 23; pp. 9775 - 9785 |
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| Autores principales: | , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
6/13/2012
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=77218843&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 77218843 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 6/13/2012 vid: 134 iid: 23 pid: 997 pub: American Chemical Society artinfo: ui: 77218843 10.1021/ja303224p ppf: 9775 ppct: 10 formats: tig: atl: Electron Paramagnetic Resonance and Mössbauer Spectroscopy and Density Functional Theory Analysis of a High-Spin' Fe-Oxo Complex. aug: au: Gupta, Rupal Lacy, David C. Bominaar, Emile L. Borovik, A. S. Hendrich, Michael P. affil: Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States Department of Chemistry, University of California-Irvine, 1102 Natural Sciences H, Irvine, California 92697, United States su: Electron paramagnetic resonance spectroscopy Mössbauer spectroscopy Density functionals Oxidizing agents Iron compounds Oxo compounds sug: subj: Electron paramagnetic resonance spectroscopy Mössbauer spectroscopy Density functionals Oxidizing agents Iron compounds Oxo compounds ab: High-spin Fe-oxo species are known to be kinetically competent oxidants in non-heme iron enzymes. The properties of these oxidants are not as well understood as the corresponding intermediate-spin oxidants of heme complexes. The present work gives a detailed characterization of the structurally similar complexes [FeHbuea(O)], [FeHbuea(O)], and [FeHbuea(OH)] (Hbuea = tris[ (N'-tert-butylureayla- to)-N-ethylene]aminato) using Mössbauer and dual-frequency/dual-mode electron paramagnetic resonance (EPR) spectroscopies. The [FeHbuea(O)] complex has a high-spin (S = 2) configuration imposed by the C-symmetric ligand. The EPR spectra of the [FeHbuea(O)] complex presented here represent the first documented examples of an EPR signal from an Fe-oxo complex, demonstrating the ability to detect and quantify Fe species with EPR spectroscopy. Quantitative simulations allowed the determination of the zero-field parameter, D = +4.7 cm, and the species concentration. Density functional theory (DFT) calculations of the zero-field parameter were found to be in agreement with the experimental value and indicated that the major contribution to the D value is from spin-orbit coupling of the ground state with an excited S = 1 electronic configuration at 1.2 eV. O isotope enrichment experiments allowed the determination of the hyperfine constants A = 10 MHz for [FeHbuea(O)] and A = 8 MHz, A = 12 MHz for [FeHbuea(OH)]. The isotropic hyperfine constant (A = -16.8 MHz) was derived from the experimental value to allow a quantitative determination of the spin polarization (ρ = 0.56) of the oxo p orbitals of the Fe-oxo bond in [FeHbuea(O)]. This is the first experimental determination for non-heme complexes and indicates significant covalency in the Fe-oxo bond. High-field Mössbauer spectroscopy gave an Fe A tensor of (+5.6, +5.3, -10.9) MHz and A = -25.9 MHz for the [FeHbuea(O)] complex, and the results of DFT calculations were in agreement with the nuclear parameters of the complex. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2012 holdings: @attributes: islocal: N |
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