Fullerene as an electron buffer: Charge transfer in Li@C60

Electronic properties of neutral and charged Li@C60 complexes have been analyzed. The partial charge of the Li atom in complexes with total charges ranging from +3 to −2 has been studied. Two geometries have been considered: one with Li in the center of the C60 and one with Li 1.2 Å off-center. The calculations show that the fullerene acts as an electron buffer, with the Li charge remaining +1 regardless of the total charge and the geometry of Li@C60. We explain this with a model that includes the Coulomb interaction between the charged species, and the electron affinities and ionization potentials of Li and C60.