Dynamic Motion in CH 4 @C 60 . Evaluation and Evolution of the Interaction Nature in the Methane‐Fullerene Endohedral Cage

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Endohedral fullerenes permanently enclose an inner guest, leading to distinct confinement effects, where precise “molecular surgery” creates a temporary opening enabling the inclusion of small molecules before being sealed. Following this approach, the CH 4 @C 60 endohedral aggregate has been realized and characterized, with methane being located at the center of the fullerene cage. Owing to the resulting steric crowding due to CH 4 van der Waals radius slightly exceeding the available inner cavity of C 60 , a balance between steric repulsion and electronic stabilization ensures the favorable incorporation. From the evaluation of the hexanionic counterpart, CH 4 @C 60 6− , the variation of the π‐surface leads to enhanced stabilization through a slight reduction of steric hindrance. The endohedral dynamics is evaluated from molecular dynamics coupled with energy decomposition (MD+EDA), unraveling a constant dynamic bouncing and rotational endohedral motion within the cage, which modulates the interaction energies to retain the stabilization of the CH 4 @C 60 aggregate featuring multiple CH∙∙∙π interactions. Thus, the methane molecule remains under constant precession, serving as a prototypical case for exploration of free‐rotor behavior of incorporated molecules into confined situations, serving to envisage modulation of intermolecular motion domains, while retaining a favorable aggregation, encouraging further studies of flexible supramolecular devices.