This renewal award is made in the Organic Dynamics Program to support the research of Dr. Richard Weiss of Georgetown University. His research will explore in detail the ability of anisotropic media with varying rigidities, such as liquid crystalline solvents and alkylated silica particles, to alter the conformations and photoreactivities of solutes. Dissection of the factors responsible for the influence of anisotropic solvent order on solute reactivity requires a detailed knowledge of how solutes and neighboring solvent molecules interact under constrained conditions and the consequences of those interactions on both the mobility and flexibility of the reactive centers of the solutes. Specific processes to be studied include the formation of twisted intramolecular charge-transfer states, Norrish II reactions of alkanones and alkylphenones, and electron transfer reactions. In some cases, the reactive solutes will serve as a diagnostic tool of their local environments and in others the solvent will be used to determine the degree to which a solute's reactivity can be diverted by external forces. Reactivity parameters measured in the ordered and isotropic phases of the media will be compared and correlated with the sizes and shapes of a series of solutes. Initial solubilization sites and modes will be discerned from measurements that probe the macroscopic and microscopic properties of the systems. Results from these experiments should be germane to studies where dynamic intermolecular interactions are important.
