The small reorganization energy of C60 in electron transfer

Porphyrin-linked fullerene 1 and porphyrin-linked quinone 2 have been designed and synthesized to evaluate the size and shape effect of fullerene in electron transfer. For evaluation of such an effect C60 and benzoquinone with comparable reduction potentials have been chosen and linked with a porphyrin, where a relatively rigid spacer ensures similar separation distance and nature of the inteervening bonds between the redox pair. Accelerated charge separation and deceleratd charge recombination were observed in 1 compared with 2 by picosecond fluorescence lifetime measurements and time-resolved transient absorption spectroscopy. They may be explained by the smaller reorganization energy in C60 compared with those in small acceptors.