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Spins Under Pressure: A mechanistic understanding of homogeneous catalysis by high pressure EPR

压力下旋转：高压 EPR 均相催化的机理理解

基本信息

批准号：
EP/K017322/1
负责人：
Damien Murphy
金额：
$ 63.52万
依托单位：
CARDIFF UNIVERSITY
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FK017322%2F1
关键词：
Spins Under Pressure mechanistic understanding

项目摘要

Catalysis is an extremely important branch of science, which is vital in our modern society. It is estimated that about 90% of all processed chemical compounds have, at some stage of their production, involved the use of a catalyst. As a result catalysis is recognized as a key strategic priority area by EPSRC. In general, catalytic reactions are more energy efficient and, at least in the case of highly selective reactions, lead to reduced waste and undesirable compounds, which is an important consideration with dwindling global reserves of raw materials. New catalysts are being developed for use in alternative energy sources and new conversion technologies, for manufacturing of new materials, for synthesis of molecules such as pure drugs, and for the production of chemicals with minimal energy input. The importance of these developments cannot be overstated. In the past 10 years alone the Nobel Prize in Chemistry was awarded on three separate occasions for the outstanding achievement of scientists whose work has a strong bias in catalysis. Their combined work has revolutionized the field of fine chemical synthesis and chiral feedstock production using well defined and discrete homogeneous organometallic catalysts.Despite the phenomenal success of these homogeneous catalysts, further improvements and developments of new asymmetric catalysts, bio-catalysts and indeed heterogeneous catalysts will benefit from a greater understanding of the mechanistic pathways involved in the catalytic cycles. Undoubtedly a greater understanding of the mechanism can lead to enhanced performance, even with well established systems. Therefore this advancement in our mechanistic understanding of how catalysts function and operate will require the application and development of new techniques that can probe the catalytic reaction and reveal the inner workings of the mechanism in unsurpassed detail. One approach to address this is the development of a unique high pressure system enabling advanced Electron Paramagnetic Resonance (EPR) methods to be used for the first time to study catalytic reactions under extreme conditions. In many cases, paramagnetic metal centers or reaction intermediates are involved in catalytic cycles, so that EPR spectroscopy and the related hyperfine techniques, such as ENDOR and ESEEM, are ideal characterization tools to study reactions at high pressures as a means to gain further insights into reaction mechanism. Since pressure is a primary thermodynamic parameter of central importance in reaction kinetics, chemical equilibria, molecular conformations and molecular interactions, it is very important in catalysis, and becomes a crucial and available parameter to study the reaction mechanisms. Since the equilibria, selectivity, population of states, conformations of the catalyst - substrate intermediates, role of solvent interactions, can all be affected, HP-EPR will be able to examine these properties. The structure, redox states, electronic and spin states, dynamics, non-covalent interactions, conformation changes, relaxation behavior, can all be analysed by these advanced EPR techniques, using the high pressure facility as a means of controlling and enhancing mechanistic variables in order to facilitate their investigations. Pressure also influences the outcome of most chemical processes, and therefore the HP-EPR facility developed in this project can also be applied to a range of other problems in chemistry involving free radicals, from organic and inorganic reactions, to electron transfer and activation of small molecules. Specific collaborative projects in heterogeneous catalysis, spin crossover phenomena, and electron spin states in condensed media, will all be explored using this new HP-EPR assembly.

催化是一门极其重要的科学分支，在现代社会中至关重要。据估计，大约90%的加工化合物在其生产的某个阶段涉及催化剂的使用。因此，环境和战略研究中心将催化视为一个关键的战略优先领域。一般来说，催化反应更节能，至少在高选择性反应的情况下，减少了废物和不需要的化合物，这是全球原材料储备减少的重要考虑因素。正在开发新的催化剂，用于替代能源和新的转换技术，用于制造新材料，用于合成纯药物等分子，以及用于以最小的能量投入生产化学品。这些事态发展的重要性怎么强调都不过分。仅在过去的10年里，诺贝尔化学奖就曾三次颁发给那些在催化方面有重大贡献的科学家。尽管这些均相催化剂取得了惊人的成功，但对催化循环中所涉及的机理途径的更深入理解将有助于新的不对称催化剂、生物催化剂和非均相催化剂的进一步改进和开发。毫无疑问，对机制有更深入的了解可以提高业绩，即使是建立了完善的制度。因此，我们对催化剂如何起作用和操作的机械理解的进步将需要新技术的应用和发展，这些技术可以探测催化反应并以无与伦比的细节揭示该机制的内部运作。解决这一问题的一种方法是开发一种独特的高压系统，使先进的电子顺磁共振（EPR）方法首次用于研究极端条件下的催化反应。在许多情况下，顺磁性金属中心或反应中间体参与催化循环，因此EPR光谱和相关的超精细技术，如ENDOR和ESEEM，是研究高压反应的理想表征工具，作为进一步了解反应机理的手段。由于压力是反应动力学、化学平衡、分子构象和分子相互作用中的一个重要热力学参数，因此在催化反应中起着重要的作用，是研究反应机理的一个重要参数。由于平衡，选择性，状态的群体，催化剂-底物中间体的构象，溶剂相互作用的作用，都可以受到影响，HP-EPR将能够检查这些属性。结构，氧化还原状态，电子和自旋状态，动力学，非共价相互作用，构象变化，弛豫行为，都可以通过这些先进的EPR技术进行分析，使用高压设备作为控制和增强机械变量的手段，以促进其研究。压力也会影响大多数化学过程的结果，因此本项目中开发的HP-EPR设备也可以应用于涉及自由基的化学中的一系列其他问题，从有机和无机反应到电子转移和小分子的活化。在多相催化，自旋交叉现象，并在凝聚介质中的电子自旋状态的具体合作项目，都将使用这种新的HP-EPR组件进行探索。