Electronic Structure of an [FeFe] Hydrogenase Model Complex in Solution Revealed by X-ray Absorption Spectroscopy Using Narrow-Band Emission Detection.
High-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection, supported by density functional theory calculations (XAES-DFT), was used to study a model complex, ([Fe(μ-adt)(CO)(PMe)] (1, adt = S-CH-(NCHPh)-CH-S), of the [FeFe] hydrogenase active site. For 1 in powder mater...
| Publicado en: | Journal of the American Chemical Society Vol. 134; no. 34; pp. 14142 - 14158 |
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| Autores principales: | , , , , , |
| Formato: | Artículo |
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American Chemical Society
8/29/2012
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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=80073561&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 80073561 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: 8/29/2012 vid: 134 iid: 34 pid: 997 pub: American Chemical Society artinfo: ui: 80073561 10.1021/ja304970p ppf: 14142 ppct: 16 formats: tig: atl: Electronic Structure of an [FeFe] Hydrogenase Model Complex in Solution Revealed by X-ray Absorption Spectroscopy Using Narrow-Band Emission Detection. aug: au: Leidel, Nils Chernev, Petko Havelius, Kajsa G. V. Schwartz, Lennart Ott, Sascha Haumann, Michael affil: Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany Department of Chemistry, Uppsala University, Ångström Laboratories, 75120 Uppsala, Sweden su: Quantum chemistry Density functionals Solution (Chemistry) Hydrogen-ion concentration Molecular orbitals Chemical inhibitors Molecular structure sug: subj: Quantum chemistry Density functionals Solution (Chemistry) Hydrogen-ion concentration Molecular orbitals Chemical inhibitors Molecular structure ab: High-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection, supported by density functional theory calculations (XAES-DFT), was used to study a model complex, ([Fe(μ-adt)(CO)(PMe)] (1, adt = S-CH-(NCHPh)-CH-S), of the [FeFe] hydrogenase active site. For 1 in powder material (1), in MeCN solution (1′), and in its three protonated states (1H, 1Hy, 1HHy; H denotes protonation at the adt-N and Hy protonation of the Fe-Fe bond to form a bridging metal hydride), relations between the molecular structures and the electronic configurations were determined. EXAFS analysis and DFT geometry optimization suggested prevailing rotational isomers in MeCN, which were similar to the crystal structure or exhibited rotation of the (CO) ligands at Fe1 (1, 1Hy) and in addition of the phenyl ring (1H, 1HHy), leading to an elongated solvent-exposed Fe-Fe bond. Isomer formation, adt-N protonation, and hydride binding caused spectral changes of core-to-valence (pre-edge of the Fe K-shell absorption) and of valence-to-core (Kß2,5 emission) electronic transitions, and of Kα RIXS data, which were quantitatively reproduced by DFT. The study reveals (1) the composition of molecular orbitals, for example, with dominant Fe-d character, showing variations in symmetry and apparent oxidation state at the two Fe ions and a drop in MO energies by ~1 eV upon each protonation step, (2) the HOMO-LUMO energy gaps, of ~2.3 eV for 1 and ~2.0 eV for 1′, and (3) the splitting between iron d(z) and d(x-y) levels of ~0.5 eV for the nonhydride and ~0.9 eV for the hydride states. Good correlations of reduction potentials to LUMO energies and oxidation potentials to HOMO energies were obtained. Two routes of facilitated bridging hydride binding thereby are suggested, involving ligand rotation at Fe1 for 1Hy or adt-N protonation for 1HHy. XAES-DFT thus enables verification of the effects of ligand substitutions in solution for guided improvement of [FeFe] catalysts. 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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