M@C₇₈ (M = U, Th): Inherent Topological Connectivity Existed in Thermodynamically Stable Isomers and the Possibility of an Endohedral Fullerene Containing One Heptagon Ring

Abstract

The density functional theory combined with statistical thermodynamic analyses of M@C 78 (M = U and Th) demonstrated that four isomers, M@D 3h (24109)-C 78 , M@ C 2v (24107)-C 78 , M@C 1 (22595)-C 78 , and M@C 1 (23349)-C 78 , and a nonclassical isomer, M@ C 1 (id7)-C 78 , containing one heptagon ring possess outstanding thermodynamic stabilities in the two M@C 78 series. Especially, the M@C 1 (id7)-C 78 isomer is the first nonclassical C 78 fullerene that can exist stably. Importantly, these five fullerene cages are found to be related in the form of Stone−Wales (SW) transformations. Geometric analyses disclosed that, unlike lanthanide metals, actinide metals are more likely to bond with sumanene-type hexagonal rings when they are encapsulated in IPR C 78 cages. Frontier molecular orbital analysis showed that both U and Th atoms donate four electrons to the C 78 carbon cages.

Th@C2(8)-C84 and Th@Cs(15)-C84: impact of actinide metal ions on the electronic structures of actinide endohedral metallofullerenes

“…Accordingly, An@ C 2 (8)-C 84 is more favorable than Ln@ C 2 (8)-C 84 due to the unique actinide–sumanene interaction supported by the theoretical predictions for the Th@C 2 n family. 30,37 On the other hand, the C s (15)-C 84 cage also prefers a single actinide atom due to the actinide–sumanene interaction, while a lanthanide cluster, such as Er 2 C 2 , 38 seems more favorable than a single lanthanide atom to this cage.…”