Garcia Spectrum

Introduction During the last few years, our group has been interested in taking advantage of the wealth of knowledge on aryl ketone photochemistry with the goal of developing functional solid state materials. We envision the use of robust crystalline solids with tunable photochromic properties and adjustable lifetimes as valuable elements for the construction of optical switches, information storage devices and display elements. To accomplish this, one will need to control the rates and yields of complex photochemical processes in solids, under conditions where molecular freedom is severely limited. It will be necessary to understand how the structure and environment of a solid will affect the rates and efficiencies of reactions, and how to exploit small amplitude motions and even zero point energy vibrations to accomplish desirable chemical transformations. It will also be essential to prepare materials with the required molecular order and environmental properties. Although there is ample valuable information on the selectivity and feasibility of photochemical reactions in the solid state,1,2 structure-reactivity relations based on absolute rate constants remain a major challenge. With that in mind, we have recently analyzed the photoenolization of ortho-methyl-arylketones as a test case for the study of photochemical reaction rates in rigid media.3-6 We have found that properly selected substrates may provide a great deal of information that is valuable not only for a better understanding of solid state reactivity, but also to document and analyze challenging aspects of chemical dynamics. We discovered that the photoenolization of ortho-alkyl-arylketones constitutes an ideal system for the study of quantum mechanical tunneling.4