Water Oxidation in Synthetic heme Oxidase Models

描述(申请人提供)：拟议的研究描述了一种用于将水氧化为分子氧的单核铁催化剂的开发。催化剂设计元素的灵感来自于以分子氧为天然底物的酶。特别是，它假设，最初的O-O键的形成应该是通过活化水分子对高度氧化和亲电的氧金属单元进行亲核攻击来实现的。实现这一反应的两个关键因素是：1)生成一个足够活泼的缺电子氧金属单元，2)在关键的O-O键形成过程中质子的管理。建议的催化剂解决了这些问题，建议适当连接的Fe(V)-oxo单元将被能量处置以与水进行O-O键的形成。Fe(V)-oxo物种的反应性将使用一类新的由Corole衍生的“Hangman”配体来调节，这些配体将氢键官能团定位在四吡咯赤道环境的平面之上。合成的结构将分两个阶段进行评估，首先是Fe(V)-oxo的生成，然后是O-O键的形成和O2的释放。在这一点上，所提出的机制类似于细胞色素P450功能的微观逆转，其中O2被裂解来提供水和高价铁氧中间体。因此，预计拟议的研究将提供关于细胞色素P450单加氧酶的机制和能量需求的观点。此外，拟议研究的长期成功代表着将水转化为分子氧和氢用作燃料的可能性的引入。这样的计划将有助于减少全球对化石燃料燃烧的依赖，这将通过减少环境污染显著改善公众健康，特别是在城市地区。与长期暴露于化石燃料燃烧污染相关的风险是一个重大的、日益严重的公共卫生问题。因此，采用新的无碳能源有望直接改善人类健康，特别是在城市地区。该提案描述了一种水氧化催化剂的设计和评估，该催化剂可用作生产氢的方案的一部分，氢是一种无污染的燃料。

DESCRIPTION (provided by applicant): The proposed research describes the development of a mononuclear iron catalyst for the oxidation of water to molecular oxygen. Inspiration for elements of catalyst design are drawn from enzymes for which molecular oxygen is a natural substrate. In particular, it is hypothesized that initial O-O bond formation should be possible by nucleophilic attack of an activated water molecule on a highly oxidizing and electrophilic oxometal unit. Two factors are critical for realizing this reaction: 1) generation of a sufficiently reactive electron-deficient oxometal unit, and 2) management of protons during the key O-O bond forming event. The proposed catalyst addresses these concerns by suggesting that an appropriately ligated Fe(V)- oxo unit will be energetically disposed to undergo O-O bond formation with water. The reactivity of the Fe (V)-oxo species will be tuned using a new class of corrole-derived 'hangman' ligands, which position hydrogen bonding functionality above the plane of a tetrapyrrolic equatorial environment. The synthesized structures will be evaluated in two stages for initial Fe(V)-oxo generation and then subsequent O-O bond formation and O2 liberation. In this regard, the proposed mechanism resembles the microscopic reverse of cytochrome P450 function, where O2 is cleaved to furnish water and a high-valent iron-oxo intermediate. As such, it is expected that the proposed research will offer perspectives on the mechanism and energetic requirements of the cytochrome P450 monooxygenases. Additionally, long-term success of the proposed research represents an introduction to the possibility of converting water to molecular oxygen and hydrogen for use as fuels. Such a scheme would help reduce global dependence on fossil fuel combustion which would dramatically improve public health, especially in urban areas, by reducing environmental pollution. The risks associated with chronic exposure to pollution from fossil fuel combustion are a major and increasing public health concern. Consequently, the adoption of new non-carbon based energy sources is expected to directly improve human health, especially in urban areas. This proposal describes the design and evaluation of a water oxidation catalyst that could be used as part of a scheme to produce hydrogen, a non-polluting fuel.