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.
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