Studies of Olefin Triplets and Triplet Biradicals

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This renewal award is made in the Organic Dynamics Program in support of the research of Dr. Richard Caldwell. Alkene triplets and triplet biradicals will be studied (1) by conventional organic mechanistic methods to determine chemical outcomes and infer the nature of the intermediates; (2) by laser flash photolysis to determine transient lifetimes and intersystem crossing rates, and energies and kinetic properties of transients, and; (3) by CAS-MCSCF computations of spin-orbit coupling in small model systems. The results will lead to a fundamental understanding of triplet biradicals and olefin triplets, specifically their energetics and energy surfaces, conformations, dynamics, and ultimately the role of all of these in determining the outcomes of photochemical processes. Among the triplet reactions which will be studied are ring-opening rearrangements, olefin addition reactions, and intersystem crossing of olefin triplets. Understanding the fundamental properties and mechanistic behavior of biradical intermediates will provide the chemist with the tools to design new chemical reactions of alkene triplets and extend their role in synthetic photochemistry.