| 1. |
- Beyler, Maryline, et al.
(författare)
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Pentacoordinate iron complexes as functional models of the distal iron in [FeFe] hydrogenases
- 2011
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 47:42, s. 11662-11664
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Tidskriftsartikel (refereegranskat)abstract
- Mononuclear pentacoordinate iron complexes with a free coordination site were prepared as mimics of the distal Fe (Fe(d)) in the active site of [FeFe] hydrogenases. The complexes catalyze the electrochemical reduction of protons at mild overpotential.
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| 2. |
- Ezzaher, Salah, et al.
(författare)
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Directing protonation in [FeFe] hydrogenase active site models by modifications in their second coordination sphere
- 2010
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 46:31, s. 5775-5777
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Tidskriftsartikel (refereegranskat)abstract
- Subtle changes in the second coordination sphere of [Cl(2)bdtFe(2)-(CO)(4)(Ph2P-CH2-X-CH2-PPh2)] (bdt = benzene-1,2-dithiolate, X = NCH3, NCH2CF3, CH2) that do not influence the electronic character of the Fe-2 center can however direct protonation to three different sites: the N in the bis-phosphane, the Fe-Fe bond or the bdt-S.
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| 3. |
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| 4. |
- Leidel, Nils, et al.
(författare)
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Site-Selective X-ray Spectroscopy on an Asymmetric Model Complex of the [FeFe] Hydrogenase Active Site
- 2012
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 51:8, s. 4546-4559
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Tidskriftsartikel (refereegranskat)abstract
- The active site for hydrogen production in [FeFe] hydrogenase comprises a diiron unit. Bioinorganic chemistry has modeled important features of this center, aiming at mechanistic understanding and the development of novel catalysts. However, new assays are required for analyzing the effects of ligand variations at the metal ions. By high-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection (XAS/XES = XAES) and density functional theory (DFT), we studied an asymmetrically coordinated [FeFe] model complex, [(CO)(3)Fe(I)1-(bdtCl(2))-Fe-2(I)(CO)(Ph2P-CH2-NCH3-CH2-PPh2)] (1, bdt = benzene-1,2-dithiolate), in comparison to iron-carbonyl references. K beta emission spectra (K beta(1,3), K beta') revealed the absence of unpaired spins and the low-spin character for both Fe ions in 1. In a series of low-spin iron compounds, the K beta(1,3) energy did not reflect the formal iron oxidation state, but it decreases with increasing ligand field strength due to shorter iron-ligand bonds, following the spectrochemical series. The intensity of the valence-to-core transitions (K beta(2,5)) decreases for increasing Fe-ligand bond length, certain emission peaks allow counting of Fe-CO bonds, and even molecular orbitals (MOs) located on the metal-bridging bdt group of 1 contribute to the spectra. As deduced from 3d -> 1s emission and 1s -> 3d absorption spectra and supported by DFT, the HOMO-LUMO gap of 1 is about 2.8 eV. K beta-detected XANES spectra in agreement with DFT revealed considerable electronic asymmetry in 1; the energies and occupancies of Fe-d dominated MOs resemble a square-pyramidal F(0) for Fe1 and an octahedral Fe(II) for Fe2. EXAFS spectra for various K beta emission energies showed considerable site-selectivity; approximate structural parameters similar to the crystal structure could be determined for the two individual iron atoms of 1 in powder samples. These results suggest that metal site- and spin-selective XAES on [FeFe] hydrogenase protein and active site models may provide a powerful tool to study intermediates under reaction conditions.
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| 5. |
- Singh, Pradyumna S., et al.
(författare)
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(I,0) Mixed-Valence State of a Diiron Complex with Pertinence to the [FeFe]-Hydrogenase Active Site : An IR, EPR, and Computational Study
- 2009
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:23, s. 10883-10885
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Tidskriftsartikel (refereegranskat)abstract
- Biphenyl-2,2'-dithiolate (bpdt) bridged Fe-2(bpdt)(CO)(6) (1) undergoes two sequential electrochemically quasi-reversible reductions. The one-electron reduction product 1(-) is unusually stable against irreversible structural changes and could be characterized by IR and EPR spectroscopy supported by computational methods. Reduction to the (I,0) state does not trigger bridging coordination of CO but partial deligation of the dithiolate in 1(-) that ultimately forms a diamagnetic dimerization product.
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