Ligand K-Edge X-ray Absorption Spectroscopy of [Fe4S4]1+,2+,3+ Clusters: Changes in Bonding and Electronic Relaxation upon Redox
- 12 June 2004
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 126 (26) , 8320-8328
- https://doi.org/10.1021/ja0484956
Abstract
Sulfur K-edge X-ray absorption spectroscopy (XAS) is reported for [Fe4S4]1+,2+,3+ clusters. The results are quantitatively and qualitatively compared with DFT calculations. The change in covalency upon redox in both the [Fe4S4]1+/2+ (ferredoxin) and the [Fe4S4]2+/3+ (HiPIP) couple are much larger than that expected from just the change in number of 3d holes. Moreover, the change in the HiPIP couple is higher than that of the ferredoxin couple. These changes in electronic structure are analyzed using DFT calculations in terms of contributions from the nature of the redox active molecular orbital (RAMO) and electronic relaxation. The results indicate that the RAMO of HiPIP has 50% ligand character, and hence, the HiPIP redox couple involves limited electronic relaxation. Alternatively, the RAMO of the ferredoxin couple is metal-based, and the ferredoxin redox couple involves extensive electronic relaxation. The contributions of these RAMO differences to ET processes in the different proteins are discussed.Keywords
This publication has 38 references indexed in Scilit:
- Electronic Structure Contributions to Electron-Transfer Reactivity in Iron−Sulfur Active Sites: 3. Kinetics of Electron TransferInorganic Chemistry, 2003
- Atomic resolution structures of oxidized [4fe-4s] ferredoxin from Bacillus thermoproteolyticus in two crystal forms: systematic distortion of [4fe-4s] cluster in the proteinJournal of Molecular Biology, 2002
- S K-edge X-ray Absorption Studies of Tetranuclear Iron−Sulfur Clusters: μ-Sulfide Bonding and Its Contribution to Electron DelocalizationJournal of the American Chemical Society, 2000
- Influence of Charge and Polarity on the Redox Potentials of High-Potential Iron-Sulfur Proteins: Evidence for the Existence of Two GroupsBiochemistry, 1995
- Three-Dimensional Solution Structure of the Oxidized High Potential Iron-Sulfur Protein from Chromatium vinosum through NMR. Comparative Analysis with the Solution Structure of the Reduced SpeciesBiochemistry, 1995
- EPR Study of the [Fe4S4]+ State in Single Crystals of (Et4N)3[Fe4S4(SCH2Ph)4]: g-Tensors of Kramers Doublets of the S = 3/2 Ground StateJournal of the American Chemical Society, 1995
- Ligand K-edge x-ray absorption spectroscopic studies: metal-ligand covalency in a series of transition metal tetrachloridesJournal of the American Chemical Society, 1995
- Active-site electronic structure contributions to electron-transfer pathways in rubredoxin and plastocyanin: direct versus superexchangeJournal of the American Chemical Society, 1993
- New structural insights into the iron-molybdenum cofactor from Azotobacter vinelandii nitrogenase through sulfur K and molybdenum L x-ray absorption edge studiesJournal of the American Chemical Society, 1988
- Valence bond description of antiferromagnetic coupling in transition metal dimersThe Journal of Chemical Physics, 1981