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利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 本项目的目的是合成和表征高价铁氧配合物，并将其应用于选择性C-H键活化催化剂。我们稳定高价二铁单元的策略包括通过使用强给电子配体来增加铁离子的电子密度。对于第一代配体，它们涉及强烈的电子给体S和p-给体，即酚类化合物。对这些配合物的详细研究，特别是X射线吸收光谱(XAS)表明，1)氧化是以配体为中心的，而不是以金属为中心的；2)被氧化的物种解离成单核物种。我们将这些结果用于配体设计的优化。合成了新的第二代去核配体，对它们的FeIIFeII、FeIIFeIII和FeIIFeIII配合物的初步研究表明，这些配合物适合于生成高价双核配合物，这些配合物应该导致金属中心的氧化，并且作为双核实体应该具有更高的稳定性。我们建议使用XAS来研究母体络合物在溶液中的分子和电子结构，以及单电子和双电子被氧化物种的结构。

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. 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.