The Inorganic, Bioinorganic, and Organometallic Program supports research in inorganic photochemistry. This research provides a fundamental basis for practical applications in the design of solar concentrators, photolithography and the treatment of certain diseases. Moreover, excited state species are being investigated in regard to various energy conversion and fuel formation schemes. This work will delineate factors influencing associative phenomena of excited-state coordination compounds. In particular the influence of donor strength on exciplex quenching and the role of donor/acceptor interactions in directing electron-transfer and energy-transfer reactions of charge-transfer (CT) states will be described in detail. Associative photosubstitution processes will also be studied. At the time same time new excited state reagents will be developed and characterized including water-soluble copper(I) complexes, copper(I) systems with high energy excited states, polynuclear systems, and photooxidizing ligand-to-metal CT states. Another objective will be to determine the influence of charge and substituent effects on copper phenanthrolines as "footprinting" reagents for DNA. Finally, the research will lead to effective photosensitizers based on conformationally constrained terpyridine ligands, and it will reveal how ligand substituents affect localization of CT states on particular ligands in mixed-ligand complexes. The methods used will include steady-state photolysis, absorption and emission spectroscopies and temperature-dependent lifetime studies. A new technique for simultaneous determination of reaction quantum yields and product spectra will also be elaborated. This research should contribute significantly to our understanding of the energies, the reactivities, and the lifetimes of excited-state transition metal complexes. It should result in the development of new DNA structure probes and potentially useful photo-induced nuclease activity.
