Photoinduced electron transfer and electron-mediating systems from aromatic amines to triplet states of C_(60) and C_(70) in the presence of a viologen dication

摘要

Photoinduced electron transfer between fullerenes (C_(60) and C_(70)) and various aromatic amines (AA's) in the absence and presence of a viologen dication has been studied by the transient absorption method in the visible and near-IR regions. Electron-transfer takes place from AA's to the triplet states of fullerenes (~3C_(60)~* and ~3C_(70)~*) giving the anion radicals of fullerenes (C_(60)~(·-) and C_(70)~(·-)) and the radical cations of AA's (AA~(·+). The rate constants and efficiencies of electron transfer are quite high, because of the high electron-donor abilities of AA's as their low oxidation potentials indicate. The absorption bands of AA~(·+) appeared also in the near-IR region indicating that the radical-cation center (hole) delocalizes over the entire region of each AA. On addition of an octylviologen dication (OV~(2+)) to C_(60)/C_(70)-AA systems, the electron-mediating process from C_(60)~(·-) and C_(70)~(·-) to OV~(2+) occurs yielding the viologen radical cation (OV~(·+)) with longer lifetime.