Electroreduction of C-60 in aprotic solvents .3. Voltammetric study, at microelectrode, of C-60(n-) (n=0 to 4) solvation in the absence of supporting electrolyte

Solvent effects on the electroreductions of C-60((x-1)-/n-)(n = 1 to 4) were studied in eleven single aprotic solvents and in different pyridine-acetonitrile binary solvent mixtures. For that purpose, voltammetric reversible half-wave potentials, E(1/2), of the electroreduction steps were determined at a 10 mu m diam Pt disk microelectrode in the absence of supporting electrolyte. In this way, concomitant ion-pairing effects, operative in the presence of supporting electrolyte, were eliminated. The E(1/2) values were corrected for the ohmic drop of potentials and correlated with solvent polarity parameters in order to account for the stabilizing solvent role. The observed differences of E(1/2) values in different solvents were discussed in terms of weak ion-dipole interactions. The voltammetric studies of specific solvation in pyridine-acetonitrile mixtures in the absence of supporting electrolyte have shown no changes of acetonitrile solvation and the loss of at least two pyridine molecules from the solvation shell of C-60(n-)(n = 0 and 1) accompanying each of the first two C-60(n-1)-/n- electroreductions.