XAS CHARACTERIZATION OF HIGH-VALENT IRON DIMERS RELEVANT TO METHANE MONOOXGENASE

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他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。 本课题的主要目的是研究高价铁氧配合物的合成、表征及其在C-H键选择性活化催化剂中的应用。我们稳定高价二铁单元的策略涉及通过使用强供电子配体来增加铁离子处的电子密度。对于第一代的配体，这些涉及强供电子的s-和p-供体，即酚盐。这些配合物的详细研究，特别是通过X射线吸收光谱（XAS），揭示了1）的氧化是配体为中心的，而不是金属为中心的和2）氧化的物种解离成单核物种。我们使用这些结果的配体设计的优化。新的双核配体的第二代已被合成和第一次调查的FeIIFeII，FeIIFeIII，和FeIIIFeIII配合物证明这些配合物的适用性，产生高价双核配合物，这应该导致金属为中心的氧化，并应具有更高的稳定性作为双核实体。我们建议使用XAS调查的分子和电子结构的母配合物在溶液中，以及一个和两个电子的氧化物种。

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. The aim of the current project is the synthesis and characterization of high-valent Fe-oxo complexes and their application as catalysts for selective C-H bond activation. Our strategy for stabilizing high-valent diiron units involves increasing the electron density at the iron ions by using strongly electron-donating ligands. For the ligands of the first generation, these involved strongly electron-donating s- and p-donors, namely phenolates. Detailed investigations of these complexes, particularly by -ray absorption spectroscopy (XAS), revealed that 1) the oxidation is ligand-centered and not metal-centered and 2) the oxidized species dissociate into mononuclear species. We used these results for the optimization of the ligand design. The new dinucleating ligands of the second generation have been synthesized and first investigations on their FeIIFeII, FeIIFeIII, and FeIIIFeIII complexes demonstrate the suitability of these complexes for generating high-valent dinuclear complexes, which should result in metal-centered oxidations and should possess higher stability as dinuclear entities. We propose the use of XAS to investigate the molecular and electronic structures of the parent complexes in solution as well as of the one- and two-electron oxidized species.