High-Resolution Crystallographic Studies of Chemical Reactions and Electron Distributions in Solids

在这个由实验物理化学计划支持的项目中，Philip Coppens教授和他的团队将开发X射线衍射方法，用于详细研究固体中的光致过程。 化学通常被称为分子变化的科学;因此，反应机理的研究是化学的核心。这些研究旨在增加我们对光转化为化学能的光化学过程的理解。 该研究使用晶体学，光谱学和理论计算的组合来研究纯晶体或多组分框架形成超分子固体中发生的化学反应。 后者提供了很大的通用性，因此有机会观察分子环境对反应性的影响。 这包括晶体基质对反应速率和产物构象的空间限制的影响，空腔壁的手性对产物性质的影响，以及主客体能量转移的影响，这取决于转移的方向，可以增强反应性或抑制反应性。 在开展这些活动的同时，Coppens小组将继续开发布法罗大学可转移非球面原子数据库，包括非球面原子散射因子的应用，它们在计算点电荷模型以外的分子间相互作用的静电分量中的应用，和电荷密度分析的复杂有争议的成键情况。在原子水平上的化学反应性的研究是相关的，我们的了解一般化学反应机制，包括催化和生理重要过程。 该项目涉及世界各地许多实验室所追求的科学前沿领域。 其目的之一是保持美国在该领域的竞争力。

In this project supported by the Experimental Physical Chemistry Program, Professor Philip Coppens and his team will develop 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. The latter 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. Concurrent with these activities, the Coppens group will continue development of the University at Buffalo Databank of transferable aspherical atoms,including application of aspherical atom scattering factors, their use in the calculation of the electrostatic component of intermolecular interactions beyond the point charge model, and charge density analysis of complexes with controversial bonding situations.The study of chemical reactivity at the atomic level is relevant for our understanding of chemical reaction mechanisms in general including catalytic and physiological important processes. The project concerns a frontier area of science which is pursued in many laboratories across the world. One of its aims is to keep the US competitive in the field.