The focus of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is the photochemistry of metal complexes adsorbed on porous Vycor glass. The colored compounds of such transition metals as ruthenium absorb light to form excited state molecules, which then undergo a variety of chemical reactions, such as electron transfer or bond cleavage. Both the reaction dynamics and the products which are formed are quite different in the pores of the glass than in solutions. In some cases the absorption of light causes the formation of charge-separated states of the sort needed for practical solar energy conversion. The reasons for the differences between the photochemistry of transition metal complexes in Vycor glass and in solution will be explored. The effects of using mixed ligand complexes, of changing the glass environment and of changing the assembly of reaction sites will be investigated. The nature of the surface acceptor sites responsible for electron conduction along the glass surface will be explored, and laser flash photolysis experiments will be performed to determine the dynamics of the secondary thermal and photochemical reactions which follow the primary photoprocesses and account for the differences in behavior in the glass and in solution. A particular emphasis will be placed on elucidating the sequence of steps leading to catalytic intermediates, and on the factors which control the aggregation and distribution of metals and metal oxides on the glass surface.
