Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, Mülheim an der Ruhr, 45470, Germany.
J Am Chem Soc. 2010 Dec 15;132(49):17578-87. doi: 10.1021/ja107793e. Epub 2010 Nov 17.
Despite extensive investigations of the active site of the [FeFe] hydrogenases, many details concerning the properties of the "hydrogen converting cluster" are not yet fully understood. The complexity of the so-called H-cluster is one of the main difficulties in studying the properties of its components. The present study is aimed at the mixed-valence EPR active Fe2(μ-CO)(CO)3(CN)2{MeSCH2C(Me)(CH2S)2} that is structurally closely related to the redox active binuclear part of the H-cluster in its CO-inhibited oxidized state. In this work, we present a characterization of this compound by advanced pulse EPR methods. The accurate determination of the (57)Fe, (1)H, (2)H, (14)N, and (15)N electron nuclear hyperfine interactions provided a very detailed picture of the electronic structure of this complex. A theoretical study using density functional theory (DFT) calculations identified possible isomers of the compound and further refined the knowledge about its properties. It was found that upon one electron oxidation of the parent Fe(I)-Fe(I) complex, the dominant mixed-valence Fe(I)-Fe(II) species is the one in which the CN ligand of the iron center that is distal to the thioether moves from the basal to the apical position. The unpaired spin distribution of the model complex is found to be clearly different from that of the native H-cluster. These differences are discussed and provide new insight into the functional features of the [FeFe] hydrogenase active site.
尽管人们对 [FeFe] 氢化酶的活性部位进行了广泛的研究，但许多关于“氢转化簇”性质的细节仍未完全理解。所谓 H 簇的复杂性是研究其组成部分性质的主要困难之一。本研究旨在研究与 CO 抑制氧化态下 H 簇的氧化还原活性双核部分在结构上密切相关的混合价 EPR 活性 Fe2(μ-CO)(CO)3(CN)2{MeSCH2C(Me)(CH2S)2}。在这项工作中，我们通过先进的脉冲 EPR 方法对该化合物进行了表征。（57）Fe、（1）H、（2）H、（14）N 和（15）N 电子核超精细相互作用的精确测定提供了该配合物电子结构的非常详细的图像。使用密度泛函理论 (DFT) 计算的理论研究确定了该化合物的可能异构体，并进一步完善了对其性质的认识。结果发现，在母体 Fe(I)-Fe(I) 配合物的单电子氧化过程中，占据主导地位的混合价 Fe(I)-Fe(II) 物种是铁中心的 CN 配体从基位移到顶端位置的物种。模型配合物的未配对自旋分布明显不同于天然 H 簇的分布。讨论了这些差异，并为 [FeFe] 氢化酶活性部位的功能特征提供了新的见解。
