Metal-Dependent Stability of Pristine and Functionalized Unconventional Dimetallofullerene M2@Ih-C80

The unstable fullerene Ih-C80 can be stabilized greatly by encapsulation of two rare-earth metal atoms in its interior. Here we present a theoretical study on the electronic structures and stabilities of dimetallofullerene M2@Ih-C80 (M = Y, La, Gd, Lu). Density functional calculations demonstrate that La2@Ih-C80 has a closed-shell configuration, whereas Y2@Ih-C80 has a triplet ground state. Unlike La2@Ih-C80 with a high stability, Y2@Ih-C80 is found to be a highly reactive radical due to the unpaired electron distributed on the fullerene cage. Such characteristic properties of La2@Ih-C80 and Y2@Ih-C80 originate from the different energy levels of the metal-based molecular orbitals. Y2@Ih-C80 can be stabilized, however, through exterior functionalization with a CF3 group. Interestingly, metallofullerenes Gd2@Ih-C80 and Lu2@Ih-C80 have similar frontier molecular orbitals and chemical stabilities to those of Y2@Ih-C80.

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