Photoinduced Electron Transfer in a Carotenobuckminsterfullerene Dyad

003 1 -8655/95 $05.00+0.00 0 1995 American Society for Photobiology

PHOTOINDUCED ELECTRON TRANSFER IN A CAROTENOBUCKMINSTERFULLERENE DYAD HrRosH* IMAHORI*', SERGIO CARDOSOt', DERECK TATMAN', S U Lr", LORINOSS'. GlLBERT R. SEELY', LEONIDES SERENo2, JUANACHESSA DE SILBER~, THOMAS A. MOORE$], ANA L. MOORE$'and DEVENS GUST$' 'Center for the Study of Early Events in Photosynthesis and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604,USA and ZDepartamento de Quimica y Fisica, Universidad National de Rio Cuarto, Rio Cuarto, Cbrdoba, Argentina (Received 7 August 1995; accepted 28 August 1995)

separated species car+-C;-.In CS2 solution Car-+-C;-

-

.

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'-Cdo-. which implies that internal conversion in the carotenoid is negligible. The lowest triplet level in the dyad is localized on the carotenoid and is populated in low yield from the charge-separated species. The sensitization of singlet oxygen by the fullerene component is effectively curtailed in the dyad.

INTRODUCTION

In order to explore intramolecular photochemical processes involving carotenoid polyenes and fullerenes, we have synthcsized Car