PHOTOCHEMICAL REACTIVITY OF MOLECULES TRAPPED IN SOL-GEL GLASSES

Photosensitizers trapped in porous sol-gel glasses are shown to undergo photoinduced electron transfer with molecules present in the intra-pore liquid phase. The phenomenon appears to be general, independent of molecular charge and size. The predominant mechanism involves long range electron transfer from, or to, an adsorbed solute molecule and a photosensitizer embedded in the glass. Such long range interactions are also the primary factor leading to a residual photogenerated radical ion pair which is extremely long lived (4-5 orders of magnitude longer with respect to the same process in homogeneous solutions). The results bear on artificial photosynthetic devices in which solar energy conversion and storage depends on inhibition of the energy-wasting back electron transfer reaction.