FULLERENES LINKED TO PHOTOSYNTHETIC PIGMENTS

The synthesis and photochemical characterization of two porphyrin-full erene dyads, two zinc porphyrin-fullerene dyads, and a carotenobuckmin sterfullerene are reviewed. In these molecules, the fullerene first ex cited singlet state may be formed by direct excitation or by singlet-s inglet energy transfer from the attached pigment. In polar solvents, t he dominant singlet-state decay pathway is photoinduced electron trans fer to yield the pigment radical cation and fullerene radical anion. T his charge-separated state has a long lifetime relative to the time co nstant for charge separation. In toluene, in cases where photoinduced electron transfer is slow for thermodynamic reasons, the fullerene sin glet state decays by intersystem crossing, and the resulting triplet e nergy is partitioned between the components of the dyad according to t heir triplet energies. The results suggest that fullerenes can be valu able components of photochemically active multicomponent molecular sys tems.