Reduction and electrochemistry of C60 in liquid ammonia

The authors report here the reduction of C60 slurries by solvated electrons (es-) generated electrochemically in liquid ammonia and the cyclic voltammetry (CV) of the C60- solution produced. Waves corresponding to both soluble and insoluble forms of C60n- were observed, with n spanning the range 0-6 (depending on the supporting electrolyte used). C60 in solvents in which C60 and its reduced products are soluble, e.g., CH2Cl2, benzene, and toluene, showed up to five CV waves, and by use of mixed solvents at low temperature, the presence of six CV redox waves for le- reduction steps up to C606- was demonstrated, showing complete filling of the three degenerate molecular orbitals of C60. The authors previously showed that C60 was insoluble in MeCN and that redox processes of films of C60, involving doping of the films with electrolyte cation, M+ [M+ = tetra-n-butylammonium (TBA+), Li+, K+], could be observed. Studies of film mass changes with the quartz crystal microbalance (QCM) have indicated higher solubility of the reduced forms in MeCN, with the C603- form soluble in TBA+ solutions. Indeed, slurries of C60 could be reduced electrochemically in MeCN to the -3 form, which could then be oxidized to insoluble films on the electrode. The authors now describe experiments in liquid NH3 at -70 degrees C, where C60 slurries are dissolved by reaction with es-. 16 refs., 1 fig., 1 tab