NC unit trapped by fullerenes: a density functional theory study on Sc3NC@C(2n) (2n = 68, 78 and 80).

Endohedral metallofullerenes (EMFs) with a trapped cluster size larger than four are rather scarce. Inspired by a recent experimental observation, we explored the possibility of encapsulating an unusual Sc3NC unit in three representative fullerene cages, namely, C68, C78 and C80, by means of density functional computations. The geometries, electronic and electrochemical redox properties of the corresponding EMFs, Sc3NC@C2n (2n = 68, 78 and 80), were investigated. These novel EMFs all have very favorable binding energies, implying a considerable possibility for experimental realization. The recently observed m/z = 1121 peak in the mass spectroscopy was characterized as Sc3NC@C80. Notably the lowest-energy isomer of Sc3NC@C78 has a non-IPR C78 outer cage, the possibility to accommodate five atoms inside a fullerene as small as C68 is also intriguing. Moreover, the intracluster and metal-cage covalent interactions were revealed by a quantum theory of atoms in molecules study. Infrared absorption spectra and 13C nuclear magnetic resonance spectra were also computed to assist future experimental characterization.