Donor-Acceptor Electronic Coupling at Long and Short Range

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This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports Professors Harry B. Gray, Bruce S. Brunschwig and Jay R. Winkler at the California Institute of Technology to examine factors that modulate electronic coupling interactions between donors and acceptors. Studies of electron tunneling through vitrified solvents will probe long-range (weakly coupled) systems, while short-range interactions (strongly coupled D-A complexes) will be investigated using Stark spectroscopy. In particular, detailed investigations of temperature dependences will probe the role of non-Condon effects in promoting ET in disordered media. A better understanding of D-A electronic couplings will shed new light on the factors that control electron flow in biological systems and also will aid the development of organic semiconductors and electronic devices. This research program will test the validity of superexchange coupling models and elucidate empirically the dependence of electronic coupling distance decay factors on the electronic and structural properties of the bridging medium. Studies of electron tunneling through vitrified solvents should provide key insights into long-range electronic coupling interactions. Stark spectroscopy has been selected as the method of choice to elucidate short-range couplings in strongly coupled D-A complexes. Since the development of the first organic field effect transistor in the late 1980s, there has been increasing interest in using organic molecules in electronic devices. Electron transport through organic media plays a central role in these devices, so that the proposed research may provide critical new insights to improve these devices. Students will receive training in inorganic and physical chemistry together with applications in biology. They will also participate in a special topics course in advanced inorganic chemistry, which brings together outside visitors, faculty, postdocs, graduate students, and undergraduates for wide ranging, in-depth discussions of current topics in physical inorganic chemistry.