Electron transfer from tetrathiafulvalenes to photoexcited C-70 studied by observing transient absorption in the near-IR region

The photoinduced electron transfer between C-70 and tetrathiafulvalene or bis(ethylenedithio)tetrathiafulvalene in polar and nonpolar solvents and their mixture has been investigated by nanosecond laser photolysis/transient absorption spectroscopy in the visible and near-IR regions. The transient absorption bands of the triplet state of C-70 observed in polar solvents decayed upon addition of tetrathiafulvalenes accompanied by the appearance of the transient absorption bands of the radical anion of C-70. In benzene, the quenching of the triplet state of C-70 was observed without the appearance of the radical anion of C-70 within a nanosecond laser purse, suggesting a collisional quenching of the triplet state of C-70 with tetrathiafulvalenes. The quantum yield for the formation of the radical anion via the triplet state of C-70 Was about 1 for tetrathiafulvalene in benzonitrile. The quantum yield decreased in less polar solvents. The back electron transfer rates were also evaluated in polar solvents.