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, C-68, C-78 and C-80, by means of density functional computations. The geometries, electronic and electrochemical redox properties of the corresponding EMFs, Sc3NC@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 Sc3NC@C-80. Notably the lowest-energy isomer of Sc3NC@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 C-13 nuclear magnetic resonance spectra were also computed to assist future experimental characterization.NSFC [20773018, 20873067, 20673088, 20425312, 20721001, 20423002]; 973 Program [2007CB815307]; NSF, USA [CHE-0716718]; Institute for Functional Nanomaterials (NSF) [0701525]; US Environmental Protection Agency (EPA) [RD-83385601