C 60 and C 70 Fullerene Ions in Nonpolar Liquids:  Mobility and Radiation-Chemical Changes

The drift mobilities of fullerene C60 and C70 ions were measured at several temperatures in n-pentane, neopentane, cyclohexane, tridecane, and carbon disulfide to determine the degree of solute−solvent interaction in these model systems of spherical C60 ions and ellipsoidal C70 ions in solvents of different shapes. One-component ion current decays were generally observed in the fullerene solutions using a time-of-flight pulse-conductivity technique, which indicates that ions of only one size were present in the solutions. These ions are assumed to be fullerene anions and cations formed by charge transfer from the solvents due to the higher electron affinity and lower ionization potential of the fullerenes relative to the solvents. Marked decreases of the ion mobilities were observed following γ-irradiation of the fullerene solutions, which indicate that ions larger than C60 and C70 are produced by radiolysis. These lower mobility ions may be products of radical addition to the fullerenes and/or dimerization products formed from radical or ionic precursors. Analysis of the data with the Stokes−Einstein equation leads to the conclusion that the degree of solvation of the ions is cyclohexane > neopentane ≃ n-pentane > tridecane > carbon disulfide.