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

Complexes of the fullerenes C-60 and C-70 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 (h nu(CT)) for C-60 and C-70 complexes are similar and almost independent of solvent polarity. The dependence of the h nu(CT) energies on donor ionization energy were found for C-60 complexes with substituted tetrathiafulvalenes in the solid state and in toluene. In the solid state the h nu(CT) energies are similar to 0.15-0.20 eV lower than those in the solution. The linear dependence of h nu(CT) on donor ionization energy for the C-60 complexes lie similar to 0.6-0.7 eV higher than those for the TCNE: ones. (C) 1999 Elsevier Science B.V. All rights reserved.