Comparative study of the bimolecular electron transfer of fullerenes (C60/C70) and 9,9-disubstituted fluorenes by laser flash photolysis.

Photoinduced bimolecular electron transfer processes of fullerenes (C60/C70) with fluorene derivatives, namely 9,9-bis(4-amino-3-methylphenyl)fluorene (BAMF), 9,9-bis(4-amino-3-fluorophenyl)fluorene (BAFF) and 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (BAHF) have been comparatively studied in benzonitrile by nanosecond laser photolysis technique in the visible/near-IR regions. By the selective excitation of C60/C70 using 532 nm laser light, it has been proved that electron transfer takes place from the ground state fluorenes to the triplet excited state of C60/C70. The observed rates and efficiencies of the electron transfer processes are found to be significantly associated with the substitution patterns on the 9,9-bisphenylfluorenes, and to be correlative with the free energy changes on the basis of the Rehm-Weller relation.