Optical spectroscopy of C-60 complexes.

Complexes of fullerene C-60 With different organic donors have been studied by optical absorption spectroscopy in solutions and in solid state. Charge transfer bands were found for C-60 complexes with tetrathiafulvalenes, pyr anylidene and xantenyl in the 600-1300 nm range. It is shown that the energ ies corresponding to the maxima of charge transfer bands (hv(CT)) for C60 c omplexes in solution are almost independent of solvent polarity. The hv(CT) values for the complexes in solid state are similar to 0.15-0.20 eV less t han in solution. The dependence of the hv(CT) values on donor ionization po tentials (I-P) for C-60 complexes with tetrathiafulvalenes in solid state w as found to be hv(CT) = 0.82 I-P - 3.93 eV. The lowering of the intensity w as observed for the C60 transitions at 420-540 nm in absorptoin spectra of single crystals of some C-60 complexes obviously due to isolation of C-60 m olecules.