The behavior of intermolecular interactions in fresh and aged solutions of fullerene C60 in neat N-methyl-2-pyrrolidone (NMP), as well as in NMP/xylene mixed solvents, were studied by the methods of ultraviolet-visible spectroscopy and dynamic light scattering (DLS). It has been experimentally shown that the aging of the C60/NMP solution leads to the disappearance of the characteristic maximum of molecular absorption at ∼330 nm with smoothing, as well as to an increase in the optical absorption intensity. The latter depend on the formation of “C60- NMP”complexes, as well as on the transition of fullerene molecules to the nanocluster state. Increasing the xylene content in the C60/NMP leads to significant changes in charge transfer between solute and solvent (“C60-NMP”, “C60-C60”) at a fixed concentration of fullerene. The latter leads to the reorganization of nanoparticles, which proceeds with the destruction of molecular complexes. In this case, using the DLS method, it was found that the geometric dimensions of the synthesized C60 nanoclusters decrease.