A multiplet analysis of Fe K-edge 1s->3d pre-edge features of iron complexes
A multiplet analysis of Fe K-edge 1s->3d pre-edge features of iron complexes
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DOI：
10.1021/ja964352a
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发表时间：
1997-07-09
影响因子：
15
通讯作者：
Solomon, EI
中科院分区：
文献类型：
--
作者：
Westre, TE;Kennepohl, P;Solomon, EI
研究了亚铁和三价铁模型配合物的X射线吸收Fe-K边数据，以建立对1 s-> 3d前边特征及其对铁位电子结构的敏感性的详细理解。的能量位置和分裂，和强度分布，前边缘功能被发现系统地改变与自旋状态，氧化态，几何形状，和桥接连接（双核配合物）。一种解释1 s-> 3d前边缘特征的能量分裂和强度分布的方法，被开发用于八面体、四面体和四方锥环境中的高自旋亚铁和铁络合物以及八面体环境中的低自旋亚铁和铁络合物。在每种情况下，允许的多电子激发态，确定使用配位场理论。计算了激发态的能量，并与1 s-> 3d前边缘特征中的能量分裂进行了比较。获得了多电子激发态的电四极跃迁的相对强度，并与前边缘特征的强度图案进行了比较。分析了八面体铁位畸变为四面体和四方锥构型的影响。建立了这些扭曲的情况下，从电四极和电偶极子（从3d-4p混合）强度机制的贡献的前边缘强度; 4p字符的数量和它的分布在多电子的最终状态进行了实验估计，并从密度泛函计算的理论预测相比。该方法也适用于双核配合物，并建立了一个明确的标记存在的mu-oxo铁-O-铁桥。在3d-4p混合的一般趋势的发展和讨论的一系列几何形状和氧化态的Fe配合物。提出的结果应进一步帮助铁络合物和非血红素铁酶的IS - 3D前边缘区域的解释。
X-ray absorption Fe-K edge data on ferrous and ferric model complexes have been studied to establish a detailed understanding of the 1s --> 3d pre-edge feature and its sensitivity to the electronic structure of the iron site. The energy position and splitting, and intensity distribution, of the pre-edge feature were found to vary systematically with spin state, oxidation state, geometry, and bridging ligation (for binuclear complexes). A methodology for interpreting the energy splitting and intensity distribution of the 1s --> 3d pre-edge features was developed for high-spin ferrous and ferric complexes in octahedral, tetrahedral, and square pyramidal environments and low-spin ferrous and ferric complexes in octahedral environments. In each case, the allowable many-electron excited states were determined using ligand field theory. The energies of the excited states were calculated and compared to the energy splitting in the 1s --> 3d pre-edge features. The relative intensities of electric quadrupole transitions into the many-electron excited states were obtained and compared to the intensity pattern of the pre-edge feature. The effects of distorting the octahedral iron site to tetrahedral and square pyramidal geometries were analyzed. The contributions to the pre-edge intensity from both electric quadrupole and electric dipole (from 3d-4p mixing) intensity mechanisms were established for these distorted cases; the amount of 4p character and its distribution over the many-electron final states were experimentally estimated and compared to theoretical predictions from density functional calculations. The methodology was also applied to binuclear complexes, and a clear marker for the presence of a mu-oxo Fe-O-Fe bridge was established. General trends in 3d-4p mixing are developed and discussed for a series of geometries and oxidation states of Fe complexes. The results presented should further aid in the interpretation of the Is - 3d pre-edge region of iron complexes and non-heme iron enzymes.