[Fe4S4]1+、2+、3+ 簇合物的配体 K 边 X 射线吸收光谱：氧化还原过程中键合和电子弛豫的变化

Ligand K-edge X-ray absorption spectroscopy of [Fe4S4]1+,2+,3+ clusters: changes in bonding and electronic relaxation upon redox.

作者信息

Dey Abhishek, Glaser Thorsten, Couture Manon M-J, Eltis Lindsay D, Holm R H, Hedman Britt, Hodgson Keith O, Solomon Edward I

机构信息

Department of Chemistry and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, CA 94305, USA.

出版信息

J Am Chem Soc. 2004 Jul 7;126(26):8320-8. doi: 10.1021/ja0484956.

DOI:10.1021/ja0484956

PMID:15225075

Abstract

Sulfur K-edge X-ray absorption spectroscopy (XAS) is reported for Fe(4)S(4) clusters. The results are quantitatively and qualitatively compared with DFT calculations. The change in covalency upon redox in both the Fe(4)S(4) (ferredoxin) and the Fe(4)S(4) (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.

摘要

报道了[Fe(4)S(4)](1 +、2 +、3 +)簇的硫K边X射线吸收光谱(XAS)。将结果与密度泛函理论(DFT)计算进行了定量和定性比较。在[Fe(4)S(4)](1 + / 2 +)(铁氧化还原蛋白)和[Fe(4)S(4)](2 + / 3 +)(高电位铁硫蛋白)这两种体系中，氧化还原过程中共价的变化比仅由3d空穴数变化所预期的要大得多。此外，高电位铁硫蛋白体系中的变化高于铁氧化还原蛋白体系。利用DFT计算，从氧化还原活性分子轨道(RAMO)的性质和电子弛豫的贡献方面分析了这些电子结构的变化。结果表明，高电位铁硫蛋白的RAMO具有50%的配体特征，因此，高电位铁硫蛋白氧化还原对涉及有限的电子弛豫。相比之下，铁氧化还原蛋白对的RAMO是基于金属的，铁氧化还原蛋白氧化还原对涉及广泛的电子弛豫。讨论了这些RAMO差异对不同蛋白质中电子转移过程的贡献。