PHOTOINDUCED ELECTRON-TRANSFER IN A CAROTENOBUCKMINSTERFULLERENE DYAD

A carotenoid-fullerene dyad has been synthesized by condensing a carot enoid amine with an acid group attached to C-60 by a cyclopropane-base d linkage. The lowest excited singlet state of the fullerene is strong ly quenched by electron transfer from the carotenoid moiety to generat e the charge-separated species Car(+)-C-60(.-). In CS2 solution Car(+) -C-60(.-) has a rise time of 0.8 ps and decays by charge recombination in 534 ps. Light absorbed by either chromophore produces a high yield of Car(+)-C-60(.-), which implies that internal conversion in the car otenoid is negligible. The lowest triplet level in the dyad is localiz ed on the carotenoid and is populated in low yield from the charge-sep arated species. The sensitization of singlet oxygen by the fullerene c omponent is effectively curtailed in the dyad.