Photoinduced electron transfer between fullerenes (C60/C70) and ethylenedithiotetrathiafulvalene

Electron transfer from ethylenedithiotetrathiafulvalene (EDT-TTF) to photo-excited C-60/C-70 in polar and in nonpolar solvents has been investigated by laser flash photolysis. The transient absorption band of the triplet state of C-60/C-70 (C-3(60)*/C-3(70)*) was effectively quenched by EDT-TTF with the appearance of the absorption bands of C-60(.-)/C-70(.-) ,showing that the electron transfer takes place from EDT-TTF to C-3(60)*/C-3(70)* in polar solvents. Even in non-polar solvents, a small amount of C-60(.-)/C-70(.-) disappeared by back electron transfer to (EDT-TTF)(.+) with second-order kinetics, suggesting the formation of free radical ions. The radical ions disappeared with first-order kinetics in nonpolar solvent, indicating that the radical ions are present as contact ion-pair. In the presence of O-2, the competition for the quenching of C-3(60)*/C-3(70)* takes place between electron transfer from EDT-TTF and energy transfer to O-2. Protonation reaction of C-60(.-)/C-70(.-) was also followed in the presence of appropriate proton source.