"Open rather than closed" malonate methano-fullerene derivatives. The formation of methanofulleroid adducts of Y3N@C80.

Cycloaddition of bromomalonates to Y3N@C80 unexpectedly gave rise to fulleroid derivatives with unusually high stability. Complete characterization of these derivatives is described including X-ray crystallography, 1H NMR, 13C NMR, HMQC, UV−visible, HPLC, MALDI-MS, and electrochemistry. Density functional theory calculations are also presented, which provide a rationale for the formation of the fulleroid and reveal the underlying thermodynamic basis for their stability.