Hyperfine interactions and electron distribution in Fe(II)Fe (I) and Fe (I)Fe (I) models for the active site of the [FeFe] hydrogenases: Mössbauer spectroscopy studies of low-spin Fe(I.).
J Biol Inorg Chem
; 18(6): 609-22, 2013 Aug.
Article
em En
| MEDLINE
| ID: mdl-23700296
ABSTRACT
Mössbauer studies of [{µ-S(CH2C(CH3)2CH2S}(µ-CO)Fe(II)Fe(I)(PMe3)2(CO)3]PF6 (1 OX ), a model complex for the oxidized state of the [FeFe] hydrogenases, and the parent Fe(I)Fe(I) derivative are reported. The paramagnetic 1 OX is part of a series featuring a dimethylpropanedithiolate bridge, introducing steric hindrance with profound impact on the electronic structure of the diiron complex. Well-resolved spectra of 1 OX allow determination of the magnetic hyperfine couplings for the low-spin distal Fe(I) ([Formula see text]) site, A x,y,z = [-24 (6), -12 (2), 20 (2)] MHz, and the detection of significant internal fields (approximately 2.3 T) at the low-spin ferrous site, confirmed by density functional theory (DFT) calculations. Mössbauer spectra of 1 OX show nonequivalent sites and no evidence of delocalization up to 200 K. Insight from the experimental hyperfine tensors of the Fe(I) site is used in correlation with DFT to reveal the spatial distribution of metal orbitals. The Fe-Fe bond in [Fe2{µ-S(CH2C(CH3)2CH2S}(PMe3)2(CO)4] (1) involving two [Formula see text]-type orbitals is crucial in keeping the structure intact in the presence of strain. On oxidation, the distal iron site is not restricted by the Fe-Fe bond, and thus the more stable isomer results from inversion of the square pyramid, rotating the [Formula see text] orbital of [Formula see text]. DFT calculations imply that the Mössbauer properties can be traced to this [Formula see text] orbital. The structure of the magnetic hyperfine coupling tensor, A, of the low-spin Fe(I) in 1 OX is discussed in the context of the known A tensors for the oxidized states of the [FeFe] hydrogenases.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Compostos Ferrosos
/
Elétrons
/
Hidrogenase
/
Proteínas Ferro-Enxofre
Idioma:
En
Revista:
J Biol Inorg Chem
Assunto da revista:
BIOQUIMICA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Estados Unidos