Reductive electrochemistry of spiromethanofullerenes

The synthesis and electrochemical properties of spiromethanofullerenes 1-6 are described. The syntheses were achieved via the diazomethane route, and the regioisomeric distribution of bis-adducts 3 was determined by (1)H NMR, UV-vis, and HPLC analysis. The electrochemistry of these compounds in dichloromethane exhibits, besides several reversible reductions, some irreversible waves. Reductive electrolysis of 1 and 3-5 in dichloromethane leads to the removal of the addend and thus to the formation of C60. Reductive electrolysis of 1, 2 and 6 in dichloromethane leads to a different reaction, which we tentatively assign to a reaction with the solvent to form fullerene-CH2Cl products. Electrolyses in the less reactive solvent THF lead to adduct removal for 1 and 3-5. Interestingly, significant formation of bis-adducts from the corresponding monoadducts was observed for 4 and 5. These electrochemically induced reactions, namely addend removal, reaction with the solvent, and addend transfer are influenced by the structure of the addend and by the choice of solvent.