Charge Transfer Processes in Aqueous Media Revisited
Principal investigator
Charge transfer processes in aqueous media are of a huge and ongoing interest due to their vital role in biochemistry and energy conversion applications. Despite extensive body of research invested in these processes, various modes of charge transfer and dependence thereof upon the reaction conditions are still insufficiently understood. By a synergistic combination of experimental and computational approaches, we hope to make major advances in understanding of the mechanisms and kinetics of charge transfer in free radical reactions in aqueous media, particularly of the proton-coupled electron transfer (PCET). Our focus will be on the reactions of the a-hydroxyalkyl and a-aminoalkyl radicals with halogenated organic substrates, and how the product yields of such a radical-induced dehalogenation are influenced by several buffer systems. In the similar context, we also plan to study reductive properties of the hydrogen atom, which offers a fascinating prospect of exploring the PCET process at its most fundamental. The reactions will be incited by the g-radiolysis of buffered aqueous solutions, followed by the detection and quantitative measurement of the products. This will be accompanied by quantum-chemical and molecular dynamical calculations, both to help rationalize the experimental findings and to guide the experiments. Because the PCET in these systems is remarkably accompanied by a chain reaction that greatly enhances the dehalogenation yields, we intend to elucidate the favorable conditions for the PCET to occur, especially as opposed to the rival free radical substitution and addition. A successful accomplishment of the objectives will be instrumental for resolution of the central problem in the aqueous chemistry of free radicals, and that is how to rationally design the specific reaction conditions, e.g. pH, reactant and buffer concentrations, in order to steer a free-radical induced reaction and optimize the yield due to a desired reaction channel.