High-Resolution Crystallographic Studies of Short-lived Excited State and Structural Dynamics in Solids

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Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms Program of the Division of Chemistry, Professor Philip Coppens and his team will develop and apply X-ray diffraction methods for the detailed study of photo-induced processes in solids. Chemistry is often referred to as a science of molecular change; studies of reaction mechanism are therefore central to chemistry. The studies are designed to increase our understanding of photo-chemical processes in which light is converted into chemical energy. The research uses a combination of crystallography, spectroscopy and theoretical calculations to study chemical reactions which take place in either pure crystals or in multi-component, framework-forming, supramolecular solids. These supramolecular solids offer great versatility and therefore the opportunity to observe the effect of the molecular environment on reactivity. This includes the influence of steric restrictions imposed by the crystal matrix on the reaction rate and the conformation of the product, the effect of the chirality of the cavity walls on the nature of the product, and the effect of host-guest energy transfer which can enhance the reactivity or suppress it, depending on the direction of the transfer. A particularly active component of the work is the study of light-induced fleeting species in solids. Such species exist for a millionth of a second or less, but determine the course of subsequent chemical reactions and are of crucial importance in materials chemistry.The study of chemical reactivity at the atomic level is relevant for our understanding of how chemical reactions proceed and can be manipulated. Such reactions include important catalytic, solid state and physiological processes. The project concerns a frontier area of science, solid-state chemistry, which is pursued in many laboratories across the world. One of its aims is to keep the United States competitive in the field.