Smallest Endohedral Metallofullerenes [Mg@C] ( = 4, 2, 0, -2, and -4): Endo-Ionic Interaction in Superatoms.

This work reports a series of endohedral metallofullerene superatoms [Mg@C], where = 4, 2, 0, -2, and -4. It was found that Mg transfers virtually all of its 3s electrons to the C shell, resulting in the ionic states of Mg@[C]. Detailed calculations revealed that the superatomic electronic configuration of these clusters is 1S1P1D1F. The first nine superatomic molecular orbitals (SAMOs), 1S1P1D, housed with 18 electrons, are largely based on [C] with small contributions from magnesium, while the outmost SAMOs, 1F, with 4 - extra electrons, reside solely on [C]. The interaction between the Mg ion and [C] was found to be predominately ionic in character. Furthermore, ultraviolet-visible spectra provide a theoretical basis for fingerprinting these clusters. It is hoped that this work will encourage the synthetic pursuit of these smallest superatomic systems.