Evolution of the electronic absorption and photoluminescence spectra of the fullerene C₆₀ solutions with various concentrations in a polar solvent (N-methylpyrrolidone) was studied. Comparison with the electrooptical properties of these solutions shows that a slow (associative) fullerene-solvent interaction mechanism is operative at large (nearly saturating) concentrations (1 × 10^-3 g/cm³), whereas the solutions of relatively low concentration (less than 5 × 10^-4 g/cm³) exhibit fast complex formation between fullerene and the solvent molecules. The latter interaction significantly changes the electronic structure of fullerene.