X-RAY ABSORPTION STUDIES OF HEME AND NON-HEME IRON MODELS: APPLICATION TO BIOINO

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 在我们以前的建议进行的研究中，开发了一种新的方法来分析和解释铁的L-边缘跃迁强度分布的总和微分轨道共价（DOC）。 结果表明，积分铁的L边强度可以用来获得配合物的总共价。 此外，开发了一种投影方法，该方法允许从L-边多重峰强度分布实验确定各个与轨道和DOC相关的组的共价性。 前面的研究是本文提出的一系列研究的基础。在先前的建议中开发的方法将扩展到表现出金属-配体电荷转移的络合物和非立方对称的络合物。 扩展的方法将被应用和校准σ-供体-π-受体复合物，在血红素与非血红素铁键合的性质及其与反应性的关系，本提案的一个主要焦点的研究中的一个重要步骤。 数据将从一些特定的血红素复合物中获得，并与先前研究的非血红素复合物进行比较。 特别感兴趣的是不同基态电子构型的低自旋亚铁血红素系统之间的电子结构差异。 此外，这项拟议的研究将提供基础，确定一系列的配合物，作为模型的酶细胞色素c氧化酶的电子结构。 这些模型的共价性和DOC的测定应提供洞察这种酶的电子结构和差异相关的O-O键裂解的酶，但不是模型。 最后，本文的工作将开始我们对高价铁卟啉的电子结构的研究。 使用两个非血红素铁（IV）配合物来定义Fe（IV）离子的电子贡献，我们将接下来研究最近的Fe（IV）=O模型化合物的电子结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In studies performed during our previous proposals, a new methodology was developed for analyzing and interpreting iron L-edge transition intensity distributions in terms of the total and differential orbital covalency (DOC). It was found that the integrated iron L-edge intensity could be used to obtain the total covalency of the complex. Furthermore, a projection methodology was developed which allows the covalency of the individual symmetry-related sets of orbitals and the DOC to be experimentally determined from the L-edge multiplet intensity distribution. The previous study serves as a foundation for the series of studies proposed here. The methodology developed during the previous proposal will be expanded to complexes that exhibit metal-to-ligand charge transfer and complexes of non-cubic symmetry. The expanded methodology will be applied and calibrated to sigma-donor-pi-acceptor complexes, an essential step in the study of the nature of heme versus non-heme iron bonding and its relation to reactivity, a major focus of this proposal. Data will be obtained from a number of specific heme complexes and compared to the non-heme complexes of the previous study. Of special interest are the electronic structural differences amongst low-spin ferriheme systems of different ground state electronic configurations. Additionally, this proposed research will provide the groundwork for determining the electronic structure in a series of complexes that serve as models of the enzyme cytochrome c oxidase. The determination of covalency and DOC of these models should provide insight into the electronic structure of this enzyme and differences related to the O-O bond cleavage in the enzyme but not the model. Finally, the proposed research will begin our study of the electronic structure of high valent Fe-porphyrins. Using two non-heme iron(IV) complexes to define the electronic contributions of the Fe(IV) ion, we will next study the electronic structure of a recent Fe(IV)=O model compound.