Theoretical study on monometallic cyanide cluster fullerenes MCN@C74 (M=Y, Tb).

New monometallic cyanide cluster endohedral fullerenes MCN@C74 (M=Y, Tb) have been investigated using density functional theory. Four isomers of MCN@C74 are considered based on four lowest energy C74 (2-) isomers, namely one cage with isolated pentagons and three isomers with a pentagon-pentagon junction. The results show that the variation of the cluster size has slight influence on the structures and relative stabilities of MCN@C74. The MCN@D3h(14246)-C74 derived from the only C74 cage with the isolated pentagons are predicted to possess the lowest energy. More importantly, in MCN@D3h(14246)-C74, the encapsulated YCN or TbCN cluster is triangular, similar to the results reported on YCN@Cs(6)-C82 and TbCN@C2(5)-C82. Furthermore, IR spectra and (13)C NMR spectra have also been explored to assist future experimental characterization.