Synthesis and Photoinduced Energy- and Electron-Transfer Processes of C60-Oligothienylenevinylene-C70 Dumbbell Compounds

Unsymmetric dumbbell molecules based on N-methylpyrrolidine[60] fullerene, oligothienylene-vinylenes (nTV; n = 2, 4), and N-methylpyrrolidine[70] fullerene, namely, C(60)nTV-C-70 were synthesized and their photophysical properties were studied. In nonpolar solvents, photoinduced energy-transfer process predominantly takes place from the singlet excited state of nTV to C-60 and C-70, as was confirmed by time-resolved emission and transient absorption spectroscopy. In polar solvent, charge-separation processes take place instead of energy transfer. The generated charge-separated radical-ion pairs decay to the neutral molecules by a fast charge-recombination process; for n = 4, a rate constant of 2 x 10(7) s(1) and lifetime of 50 ns were evaluated.