Quantum Chemical Insight into Metallofullerenes M2C98: M2C2@C96 or M2@C98, Which Will Survive?

Systematic studies on M2C98 (M = Sc, Y, La, Gd, Lu) series by means of density functional theory (DFT) methods disclose that having large concentrations within the temperature interval of fullerene formation, the metal-carbide endohedral fullerenes M2C2@C-98 are found to be more stable than the dimetallofullerenes M-2@C-98. When encapsulating M2C2 clusters, three types of C-96 cages will present excellent thermodynamic stabilities and become the largest metal-carbide endohedral fullerenes so far. The dynamic mechanisms of the internal C-2 moieties in the most important M2C2@C-96 species have been discussed, which provide profound understanding of metal carbide endohedral fullerenes. Moreover, C-13 NMR and IR spectra have been simulated to aid further experimental identification and characterization.