Photoinduced intermolecular electron transfer process of fullerene (C60) and amine-substituted fluorenes studied by laser flash photolysis

Photoinduced intermolecular electron transfer process of fullerene (C60) with 9,9-bis(4-triphenylamino)fluorene (BTAF) and 9,9-dimethoxyethyl-2-diphenylaminofluorene (DAF) in toluene and benzonitrile has been investigated by nanosecond laser photolysis technique in the visible/near-IR regions. By the selective excitation of C60 using 532 laser light, it has been proved that the electron transfer takes place from the ground states BTAF and DAF to the triplet excited state of C60 ((3)C60*) by observing the radical anion of C60 and radical cation of BTAF and DAF. It was observed that the electron transfer of BTAF/(3)C60* is more efficient than DAF/(3)C60* reflecting the effect of amine-substitutents of the fluorene moiety on the efficiency of the electron transfer process. On addition of a viologen dication (OV(2+)), the electron of the anion radical of C60 mediates to OV(2+) yielding the OV(+). These results proved that the photosensitized electron-transfer/electron-mediating processes have been confirmed by the transient absorption spectral method.