Water Oxidation in Synthetic heme Oxidase Models

描述（由申请人提供）：拟议的研究描述了用于将水氧化成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，假设最初的 O-O 键形成应该可以通过活化水分子对高度氧化性和亲电子的氧金属单元的亲核攻击来实现。有两个因素对于实现该反应至关重要：1）产生足够反应性的缺电子氧金属单元，2）在关键的 O-O 键形成过程中对质子的管理。所提出的催化剂通过建议适当连接的 Fe(V)-氧代单元将被积极地处理以与水形成 O-O 键，从而解决了这些问题。 Fe (V)-oxo 物质的反应性将使用一类新型的咔咯衍生的“hangman”配体进行调整，该配体将氢键功能定位在四吡咯赤道环境平面上方。合成的结构将分两个阶段进行评估：最初的 Fe(V)-氧代生成，然后是随后的 O-O 键形成和 O2 释放。在这方面，所提出的机制类似于细胞色素 P450 功能的微观逆转，其中 O2 被裂解以提供水和高价铁氧中间体。因此，预计拟议的研究将为细胞色素 P450 单加氧酶的机制和能量需求提供视角。此外，拟议研究的长期成功代表了将水转化为分子氧和氢用作燃料的可能性。这样的计划将有助于减少全球对化石燃料燃烧的依赖，通过减少环境污染，极大地改善公众健康，特别是在城市地区。长期暴露于化石燃料燃烧污染所带来的风险是一个主要且日益严重的公共卫生问题。因此，采用新的非碳能源预计将直接改善人类健康，特别是在城市地区。该提案描述了水氧化催化剂的设计和评估，该催化剂可用作生产氢气（一种无污染燃料）计划的一部分。

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.