Probing the electronic structure of [2Fe-2S] clusters with three coordinate iron sites by use of photoelectron spectroscopy.
Probing the electronic structure of [2Fe-2S] clusters with three coordinate iron sites by use of photoelectron spectroscopy.
复制标题
利用光电子能谱探测具有三配位铁位点的 [2Fe-2S] 簇的电子结构。
DOI：
10.1021/jp045177k
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Wang,Lai-Sheng
中科院分区：
文献类型：
--
作者：
Fu,You-Jun;Yang,Xin;Wang,Xue-Bin;Wang,Lai-Sheng
[Fe_2S_2Cl_2-x（CN）_x]-，[Fe_2S_2（SEt）_2-xCl_x]-，[Fe_2S_2（SEt）_2-x（CN）_x]-，[Fe_2S_2Cl_2-x（OAc）_x]-（0Ac =乙酸盐）和[Fe 2S 2（SEt）2-x（OPr）x]-（OPr =丙酸盐）（x= 0−2），是由相应的[4Fe-4S]络合物的碰撞诱导解离产生的，用光电子能谱研究了它们的电子结构。所有的[2Fe-2S]配合物都含有类似于还原[2Fe]铁氧化还原蛋白的[Fe 2S 2]+核心，但具有不同的配位几何结构。对于前三个系列，其中只涉及三配位的Fe网站，测量的结合能和取代数（x）之间的线性关系进行了观察，揭示了独立的配体贡献的总电子结合能。配体的吸电子效应按SEt → Cl → CN的顺序增加，与它们的吸电子能力顺序一致。在[Fe_2S_2Cl_2-x（OAc）_x]-和[Fe_2S_2（SEt）_2-x（OPr）_x]-配合物中的羧酸根配体被观察到作为双齿配体，产生四配位铁位点。这与它们在[4Fe-4S]立方烷配合物中的单齿配位行为不同，反映了[2Fe-2S]配合物中未满足的三配位铁位的高反应活性。具有四配位铁中心的[2Fe-2S]配合物具有较低的电子结合能，即比所有三配位平面簇合物具有更高的还原活性。所有[2Fe-2S]配合物的电子结构均符合“倒能级方案”。
Five series of [2Fe-2S] complexes, [Fe2S2Cl2-x(CN)x]-, [Fe2S2(SEt)2-xClx]-, [Fe2S2(SEt)2-x(CN)x]-, [Fe2S2Cl2-x(OAc)x]-(OAc = acetate), and [Fe2S2(SEt)2-x(OPr)x]-(OPr = propionate) (x= 0−2), were produced by collision-induced dissociation of the corresponding [4Fe-4S] complexes, and their electronic structures were studied by photoelectron spectroscopy. All the [2Fe-2S] complexes contain a [Fe2S2]+core similar to that in reduced [2Fe] ferredoxins but with different coordination geometries. For the first three series, which only involve tricoordinated Fe sites, a linear relationship between the measured binding energies and the substitution number (x) was observed, revealing the independent ligand contributions to the total electron binding energies. The effect of the ligand increases in the order SEt → Cl → CN, conforming to their electron-withdrawing ability in the same order. The carboxylate ligands in the [Fe2S2Cl2-x(OAc)x]-and [Fe2S2(SEt)2-x(OPr)x]-complexes were observed to act as bidentate ligands, giving rise to tetracoordinated iron sites. This is different from their monodentate coordination behavior in the [4Fe-4S] cubane complexes, reflecting the high reactivity of the unsatisfied three-coordinate iron site in the [2Fe-2S] complexes. The [2Fe-2S] complexes with tetracoordinated iron sites exhibit lower electron binding energies, that is, higher reductive activity than the all tricoordinate planar clusters. The electronic structures of all the [2Fe-2S] complexes were shown to conform to the “inverted energy level scheme”.