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 Sc(3)NC unit in three representative fullerene cages, namely, C(68), C(78) and C(80), by means of density functional computations. The geometries, electronic and electrochemical redox properties of the corresponding EMFs, Sc(3)NC@C(2n) (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 Sc(3)NC@C(80). Notably the lowest-energy isomer of Sc(3)NC@C(78) has a non-IPR C(78) outer cage, the possibility to accommodate five atoms inside a fullerene as small as C(68) 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 (13)C nuclear magnetic resonance spectra were also computed to assist future experimental characterization.