Energies of charge transfer for C60 and C70 complexes in solutions and in the solid state

Complexes of the fullerenes C60 and C70 with various donors have been studied in solution and in the solid state by electronic absorption spectroscopy. Charge transfer (CT) bands are found in the 620–1300 nm range. It is shown that in solution the CT energies (hνCT) for C60 and C70 complexes are similar and almost independent of solvent polarity. The dependence of the hνCT energies on donor ionization energy were found for C60 complexes with substituted tetrathiafulvalenes in the solid state and in toluene. In the solid state the hνCT energies are ∼0.15–0.20 eV lower than those in the solution. The linear dependence of hνCT on donor ionization energy for the C60 complexes lie ∼0.6–0.7 eV higher than those for the TCNE ones.