The Mean Activity Coefficients of Fullerenehexamalonates Th-C66(COO-M+)12 in Aqueous Solutions.

The Poisson-Boltzmann equation has been solved for the spherical cell model of a fullerenehexamalonate solution to obtain the contributions of the macroion and its counterions to the total electrostatic free energies. The contribution of the macroion is large and positive, whereas the contribution of the counterions is small and negative. From these data the concentration dependence of the activity coefficients of the macroion and counterions have been calculated, as well as the mean activity coefficient of the fullerenehexamalonate electrolyte. Calculated values for the mean activity coefficient have been compared with the existing experimental data and a good agreement has been observed.