Fundamental Studies of Electron Transfer in Supramolecular Systems

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Professor David H. Waldeck, of the Department of Chemistry at the University of Pittsburgh, is supported by the Organic and Macromolecular Chemistry Program for his studies of electron transfer in supramolecular systems. Time-resolved fluorescence spectroscopy will be used to study photoinduced electron transfer in well-defined supramolecular systems. The studies will explore fundamental issues of solvation and electronic coupling that are important to chemical reactivity and supramolecular chemistry. By studying electron transfer in a rigid unimolecular system which has electron donor and acceptor units on opposite sides of a molecular cleft, the importance of non-bonded contacts between the electron clouds of the donor and acceptor groups and other molecules can be assessed. Studies will be performed for two types of systems, one in which a molecular moiety is covalently bound to the rigid bridge and lies in the cleft and one in which a guest molecule hydrogen bonds to a receptor located on the bridge. Molecular solvation models, the dependence of coupling on electronic character, the transition from weak to strong coupling, and the influence of nuclear motion will be explored.Electron transfer between distinct molecular units is the primary event in many natural (e.g., photosynthesis) and technological (e.g., corrosion) processes. In addition, electron transfer is a relatively simple chemical transformation amenable to rigorous and quantitative study. On a broader level, electron transfer and charge displacement are central elements of most chemical reactions. Nonetheless, our understanding of how the two electron clouds of non-bonded molecules interact with one another, an essential element of any chemical transformation, is not well understood. With the support of the Organic and Macromolecular Chemistry Program, Professor David H. Waldeck, of the Department of Chemistry at the University of Pittsburgh, is carrying out studies designed to investigate and quantify fundamental aspects of electron transfer reactions that involve electron tunneling through non-bonded contacts.