Smallest Endohedral Metallofullerenes [Mg@C 20 ] n ( n = 4, 2, 0, -2, and -4): Endo-Ionic Interaction in Superatoms.

This work reports a series of endohedral metallofullerene superatoms [Mg@C 20 ] n , where n = 4, 2, 0, -2, and -4. It was found that Mg transfers virtually all of its 3s electrons to the C 20 shell, resulting in the ionic states of Mg 2+ @[C 20 ] n -2 . Detailed calculations revealed that the superatomic electronic configuration of these clusters is 1S 2 1P 6 1D 10 1F 4- n . The first nine superatomic molecular orbitals (SAMOs), 1S 2 1P 6 1D 10 , housed with 18 electrons, are largely based on [C 20 ] n -2 with small contributions from magnesium, while the outmost SAMOs, 1F 4- n , with 4 - n extra electrons, reside solely on [C 20 ] n -2 . The interaction between the Mg 2+ ion and [C 20 ] n -2 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.