Synthesis of Diiron(IV)-Oxo Complexes of Relevance to Methane Monoyxgenase

描述（由申请人提供）：项目摘要：在几乎所有的好氧生物中发现，具有非血红素铁中心的氧活化酶通常用于执行要求苛刻的转化。该研究项目的主要目的是通过合成和表征高价铁-氧代络合物来深入了解铁酶的氧活化性质，该络合物模拟关键催化中间体的结构和反应性。特别是，将采用新的策略来产生复合物，模拟可溶性甲烷单加氧酶（MMO），一种酶，使用氧气将甲烷转化为甲醇的反应物种。通过允许某些细菌利用甲烷作为其唯一的碳和能量来源，MMO每年从大气中消除近10亿吨这种强效温室气体。此外，在工业上复制MMO反应以提供产生甲醇、化学原料和潜在能源的环境清洁手段方面存在相当大的兴趣。因此，高价二铁物种的研究具有巨大的生物，环境和技术意义。sMMO催化循环中的关键步骤涉及甲烷通过被称为中间体Q的表征不佳的二铁（IV）-氧代物种的氧化。在最近成功地产生单核铁（IV）-氧代配合物的基础上，该提案描述了两种原始路线，用于合成中间体Q的小分子模型，重现其双-氧代-二铁（IV）“金刚石核心”。用电子吸收光谱、共振拉曼光谱、穆斯堡尔谱和X-射线吸收光谱等多种光谱和结构方法对所得配合物进行了表征，并考察了它们对有机底物的反应活性。这一结果有望进一步加深我们对中间体Q的几何和电子结构的理解，并为生物体系中氧活化机制提供新的见解。此外，该项目可能导致甲烷氧化仿生催化剂的开发。相关性：通过合成复制重要生物物种的结构和反应性的小分子铁复合物，这项研究提案旨在更好地了解人类和其他生物体中需要在酶中的铁中心进行氧活化的过程。此外，该项目可能导致开发新的催化剂，使化学家能够使用氧气进行碳氢化合物的环境友好型转化，从而减少大气中的污染和温室气体水平。

DESCRIPTION (provided by applicant): Project Summary: Found in nearly all aerobic organisms, oxygen-activating enzymes with non-heme iron centers are often employed to perform demanding transformations. The major aim of this research project is to gain insights into the nature of oxygen activation at iron enzymes through the synthesis and characterization of high-valent iron-oxo complexes that mimic the structure and reactivity of key catalytic intermediates. In particular, novel strategies will be employed to generate complexes that model the reactive species of soluble methane monooxygenase (MMO), an enzyme that uses oxygen to convert methane to methanol. By allowing certain bacteria to utilize methane as their sole source of carbon and energy, MMOs eliminate nearly a billion tons of this potent greenhouse gas from the atmosphere each year. Moreover, there is considerable interest in replicating the MMO reaction industrially in order to provide an environmentally-clean means of generating methanol, a chemical feedstock and potential energy source. Thus, the study of high-valent diiron species carries enormous biological, environmental, and technological implications. The crucial step in the sMMO catalytic cycle involves the oxidation of methane by a poorly- characterized diiron(IV)-oxo species known as intermediate Q. Building upon the recent success in generating mononuclear iron(IV)-oxo complexes, this proposal describes two original routes for the synthesis of small-molecule models of intermediate Q that reproduce its bis-oxo-diiron(IV) "diamond core". The resulting complexes will be characterized with a variety of spectroscopic and structural methods, such as electronic absorption, resonance Raman, M"ssbauer and X-ray absorption spectroscopies, and their reactivites towards organic substrates will be examined. The results are expected to advance our current understanding of the geometric and electronic structures of intermediate Q, and provide new insights into mechanism of oxygen activation in biological systems. Additionally, this project may lead to the development of biomimetic catalysts for methane oxidation. Relevance: By synthesizing small-molecule iron complexes that replicate the structures and reactivities of important biological species, this research proposal aims to better understand those processes in humans and other organisms that require oxygen activation at iron centers in enzymes. Additionally, this project may lead to the development of new catalysts that will allow chemists to use oxygen to carry out environmentally- friendly transformations of hydrocarbons, thereby reducing pollution and levels of greenhouse gases in the atmosphere.