SusChEM: Water Oxidation by Homogeneous Manganese Catalysts

本研究由化学系化学合成项目资助，由美国加州大学伯克利分校化学系的Jeremy M.印第安纳州大学化学和生物化学系的史密斯研究了明确的锰催化剂如何将水转化为氧气。大自然已经学会了利用可见光将水转化为氧气。这个过程被称为光合作用，并在一个复杂的生物蛋白质中使用锰。在该项目中，正在研究较小的锰化合物，以提供关于光合作用氧形成的基本信息，并提供基于廉价、丰富的金属的新催化剂，供实验室或化学工业使用。该项目的一个重要组成部分是对学生进行生物无机和能源化学方面的培训。本计画利用合成、光谱及物理研究探讨锰大环配合物氧化水的机制。模块化催化剂设计允许引入官能团，从而能够系统地研究质子和氢原子传输以及金属辅因子对催化剂性能的影响。一个家庭的锰吡啶并吡喃化合物作为功能模型的光系统II的氧释放复合物。这项工作旨在：（1）实验验证计算提出的通过这些络合物进行水氧化的机制，（2）确定吡啶并吡喃立体电子性质对催化选择性和活性的影响，以及（3）描绘第二配位层对催化活性的影响，包括质子和氢原子中继以及氧化还原无辜金属的存在。这些物种的光谱，反应性和机理研究提供了相关的见解生物水氧化机制，特别是关键的O-O键形成步骤。化合物通过X射线衍射、NMR、EPR和IR的标准物理方法进行表征，而催化行为通过电化学测量和标准机械探针的组合进行研究。

In this project funded by the Chemical Synthesis Program of the Chemistry Division, Professor Jeremy M. Smith, Department of Chemistry and Biochemistry, Indiana University, investigates how well-defined manganese catalysts convert water into oxygen. Nature has learned to convert water to oxygen using visible light. This process is called photosynthesis and uses manganese in a complicated biological protein. In this project, smaller managanese compounds are being studied both to provide basic information on photosynthetic oxygen formation and to provide new catalysts, based on inexpensive, abundant metals, for use in the laboratory or by the chemical industry. An important part of the project involves the training of students in bioinorganic and energy chemistry. This project utilizes synthetic, spectroscopic and physical studies to investigate the mechanism of water oxidation by manganese macrocyclic complexes. The modular catalyst design allows for the introduction of functional groups, enabling systematic studies into the effect of proton and hydrogen atom transport as well as metal cofactors on catalyst performance. A family of manganese pyridinophane compounds serve as functional models for the oxygen evolving complex of Photosystem II. This work sets out to: (1) experimentally validate a computationally-proposed mechanism for water oxidation by these complexes, (2) determine the impact of pyridinophane stereoelectronic properties on catalytic selectivity and activity, and (3) delineate the effect of the second coordination sphere on catalytic activity, including the presence of proton and hydrogen atom relays, and redox-innocent metals. Spectroscopic, reactivity and mechanistic investigations of these species provide insights relevant to the biological water oxidation mechanism, particularly the key O-O bond forming step. Compounds are characterized by standard physical methods of X-ray diffraction, NMR, EPR, and IR, while catalytic behavior is investigated by a combination of electrochemical measurements and standard mechanistic probes.