CN bond orientation in metal carbonitride endofullerenes:A density functional theory study

The geometric and electronic structures of scandium carbonitride endofullerene Sc₃CN@C_2n (2n=68, 78, 80, 82, and 84) and Sc(Y)NC@C₇₆ have been systematically investigated to identify the preferred position of internal C and N atoms by density functional theory (DFT) calculations combined with statistical mechanics treatments. The CN bond orientation can generally be inferred from the molecule stability and electronic configuration. It is found that Sc₃CN@C_2n molecules have the most stable structure with C atom locating at the center of Sc₃CN cluster. The CN bond has trivalent form ofCN^3- and connects with adjacent three Sc atoms tightly. However, in Sc(Y)NC@C₇₆ withNC^-, the N atom always resides in the center of the whole molecule. In addition, the stability of Sc₃CN@C_2n has been further compared in terms of the organization of the corresponding molecular energy level. The structural differences between Sc₃CN@C_2n and Sc₃NC@C_2n are highlighted by their respected infrared spectra.