Picosecond Dynamics of Organic Ionic Intermediates

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The mechanism and consequences of rapid electron transfer reactions will be investigated using a picosecond laser flash photolysis system designed to record the absorption of transient intermediates on the order of a few picoseconds. The cycloaddition reactions to be investigated include: (1) the addition of olefins to stilbene; (2) the Paterno-Buchi reaction between benzophenone and a variety of alkenes and selected alkynes; and (3) an evaluation of the mechanism for photoreduction of aryl ketones with metal hydrides. All of the reactions to be investigated involve cycloaddition reactions which proceed via short lived intermediates. In the context of the electron transfer processes which occur in these reactions, the crucial differences between contact and solvent separated ion-pairs will be clearly delineated for the first time. %%% This grant from the Organic Dynamics Program to Professor Kevin Peters at the University of Colorado will involve the study of very fast chemical reactions which are complete in less than a billionth of a second. Reactions called cycloadditions, which are promoted by the transfer and redistribution of electrons from one molecule to another, will be monitored by a laser system capable of recording the existence of short-lived intermediate species which only exist for a few trillionths of a second. The need to understand the properties of these transient species is critical to defining the role of electron transfer in a variety of reactions of importance in biological and technological processes.