This research focuses on the synthesis and photochemistry of new super photoacids, including their application to biological and photoresist systems. Proton transfer represents one of the two most fundamental processes in nature, yet techniques for studying the dynamics of this process have relied on relatively inefficient, commercially-available materials. This is in contrast to electron transfer, which has seen an overwhelming synthetic, mechanistic, and dynamic effort. Although many similarities exist between the two, including solvent-dependent kinetics rationalized through Marcus theory, photoexcitation creates electrochemical driving forces, which are readily rationalized by an analysis of oxidation/reduction potentials. The occurrence of proton transfer in the excited state presents unique opportunities to study the chemistry and dynamics of this fundamental process using ultrafast time-resolved techniques, if the electronic structure of the excited state can be understood. This project involves the design and synthesis of new substrates that test concepts of structure, driving force, and entropy and that allow correlations to be made with theory. This approach uses a knowledge of the electronic structure of excited-states of acids to design molecules which exhibit enhanced excited-state acidity. Some of these, which are termed "super" photoacids, are the strongest reversible photoacids known. Synthetic methodologies will be developed to achieve molecules whose photoacidity can be tailored thereby providing new methods for studies of proton transfer reactions and novel polymerization catalysts. The research introduces graduate and postdoctoral students to new concepts in acid-base chemistry and kinetics, and to the methodologies to examine these transient effects.
With this award, the Organic and Macromolecular Chemistry Program supports the research of Professor Laren Tolbert of the School of Chemistry and Biochemistry at Georgia Institute of Technology. Professor Tolbert will focus his research efforts on the synthesis and excited state chemistry of molecules, called photoacids, whose acid-base properties change on optical excitation. These molecules, which can exhibit immense, but transient, changes in acid-base properties, provide new methods to study acid-base chemistry, and novel approaches to photoactivated, polymerization catalysts. Professor Tolbert is expanding his research efforts through collaborations with Professors Robert Dickson in his Department, Juergen Ruehe of Frieburg University and Menachim Gutman at the University of Tel Aviv. Through Professor Tolbert's research, graduate and postdoctoral students will be exposed to new concepts in acid-base chemistry, and the methodology to examine these transient effects.