Structural Determination on Yb@C78 Reveals an Unexpected Relationship of Yb@C2n (2n = 74–80)

Abstract

With combined quantum chemical and statistical thermodynamic methods, we performed a systemic investigation on the endohedral metallofullerene, Yb@C78, in order to determine its cage structure and the metal position. Our results revealed that Yb@C78 possesses an IPR-satisfying cage structure, C2v(24107)-C78, which is obviously different from the cage structures of previously found C78-based metallofullerenes. Interestingly, the internal metal is found to be located upon a pyracylene motif apart from the 2-fold axis of the C2v(24017)-C78 cage, displaying another new example of metallofullerenes with the internal metal locating asymmetrically. The reason why ytterbium exhibits such an anomalous location stems from a comprehensive effect of the three main following factors: coordination number of ytterbium, surface curvature release, and electrostatic interaction. More importantly, an unexpected relationship among the cage structures of Yb@C2n (2n = 74–80) through C2 insertion and Stone–Wales transformations is found, offering opportunities to further investigate the formation mechanism of endohedral fullerenes.