Photoinduced electron transfer on the surface of silica gel

The kinetics of electron transfer between the radical cations of a series of anthracene derivatives and a variety of amine electron donors were studied on the surface of silica gel. The anthracene derivatives were excited with 355 nm radiation and formed radical cations by multi-photon ionisation. The radical cation absorption decay was measured by diffuse reflectance laser flash photolysis at wavelengths between 680 and 780 nm, depending upon the identity of the substituent of the anthracene. The decay kinetics of the radical cations were complex and non-exponential. The addition to the surface of a co-adsorbed electron donor, with an oxidation potential below that of the anthracene derivative resulted in an increase in the rate of the radical cation decay because of the electron transfer from the donor species. The kinetics of electron transfer were fitted with using the dispersive model of Albery. [Continues.]