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

The unstable fullerene I h -C 80 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 M 2 @ I h -C 80 (M = Y, La, Gd, Lu). Density functional calculations demonstrate that La 2 @ I h -C 80 has a closed-shell configuration, whereas Y 2 @ I h -C 80 has a triplet ground state. Unlike La 2 @ I h -C 80 with a high stability, Y 2 @ I h -C 80 is found to be a highly reactive radical due to the unpaired electron distributed on the fullerene cage. Such characteristic properties of La 2 @ I h -C 80 and Y 2 @ I h -C 80 originate from the different energy levels of the metal-based molecular orbitals. Y 2 @ I h -C 80 can be stabilized, however, through exterior functionalization with a CF 3 group. Interestingly, metallofullerenes Gd 2 @ I h -C 80 and Lu 2 @ I h -C 80 have similar frontier molecular orbitals and chemical stabilities to those of Y 2 @ I h -C 80 .