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

项目概述：几乎在所有有氧生物中发现，具有非血红素铁中心的氧激活酶通常用于执行苛刻的转化。本研究项目的主要目的是通过合成和表征模仿关键催化中间体结构和反应活性的高价铁氧配合物，深入了解铁酶的氧活化性质。特别是，将采用新的策略来生成模拟可溶性甲烷单加氧酶（MMO）反应物种的配合物，MMO是一种利用氧气将甲烷转化为甲醇的酶。通过允许某些细菌利用甲烷作为碳和能量的唯一来源，mmo每年从大气中消除近10亿吨这种强有力的温室气体。此外，为了提供一种环境清洁的生产甲醇（一种化学原料和潜在能源）的方法，人们对在工业上复制MMO反应非常感兴趣。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催化循环的关键步骤涉及被称为中间Q的特征不明显的二铁(IV)-氧的甲烷氧化。在最近成功生成单核铁(IV)-氧配合物的基础上，本提案描述了合成中间Q的小分子模型的两条原始路线，这些模型可以复制其双氧二铁（IV）“钻石核心”。所得到的配合物将用各种光谱和结构方法进行表征，如电子吸收光谱、共振拉曼光谱、斯堡尔光谱和x射线吸收光谱，并研究它们对有机衬底的反应性。这些结果有望进一步加深我们对中间Q的几何和电子结构的理解，并为生物系统中氧活化的机制提供新的见解。此外，该项目可能会导致甲烷氧化仿生催化剂的发展。相关性：通过合成复制重要生物物种结构和反应活性的小分子铁复合物，该研究计划旨在更好地了解人类和其他生物中需要氧激活酶中的铁中心的过程。此外，这个项目可能会导致新的催化剂的发展，这将允许化学家使用氧气进行环境友好的碳氢化合物转化，从而减少污染和大气中的温室气体水平。

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.