Journal article
Computational studies of modified [Fe3S4] clusters: Why iron is optimal
This work reports density functional computations of metal-substituted models of biological [Fe3S4] clusters in oxidation states [MFe2S4]+/0/−1 (M = Mn, Fe, Co, Ni, Cu, Zn, and Mo). Geometry optimization with a dielectric screening model is shown to provide a substantial improvement in structure, compared to earlier used standard procedures.
The error for average Fe–S bonds decreased from 0.038 Å to 0.016 Å with this procedure. Four density functionals were compared, B3LYP, BP86, TPSS, and TPSSh. B3LYP and to a lesser extent TPSSh energies were inconsistent with experiment for the oxidized [Fe3S4]+ cluster. BP86 (and to a slightly lesser extent TPSS) was within expected theoretical and experimental uncertainties for all oxidation states, the only qualitative error being 5 kJ/mol in favor of the MS = 3/2 configuration for the [Fe3S4]+ cluster, so BP86 was used for quantitative results.
Computed reorganization energies and reduction potentials point directly towards the [Fe3S4] cluster as the superior choice of electron carrier, with the [ZnFe2S4] cluster a close second. In addition, partially and fully Mo-substituted clusters were investigated and found to have very low reorganization energies but too negative reduction potentials.
The results provide a direct rationale why any substitution weakens the cluster as an electron carrier, and thus why the [Fe3S4] composition is optimal in the biological clusters.
Language: | English |
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Year: | 2008 |
Pages: | 87-100 |
ISSN: | 18733344 and 01620134 |
Types: | Journal article |
DOI: | 10.1016/j.jinorgbio.2007.07.025 |
ORCIDs: | Kepp, Kasper Planeta |