Trapping N 2 and CO 2 on the Sub‐Nano Scale in the Confined Internal Spaces of Open‐Cage C 60 Derivatives: Isolation and Structural Characterization of the Host–Guest Complexes

An open‐cage C 60 tetraketone with a large opening was able to encapsulate N 2 and CO 2 molecules after its exposure to high pressures of N 2 and CO 2 gas. A subsequent selective reduction of one of the four carbonyl groups on the rim of the opening induced a contraction of the opening (→ 2 ) and trapped the guest molecules inside 2 . The thus‐obtained host–guest complexes N 2 @ 2 and CO 2 @ 2 could be isolated by recycling HPLC, and were found to be stable at room temperature. The molecular structures of N 2 @ 2 and CO 2 @ 2 were determined by single‐crystal X‐ray diffraction analyses, and revealed a short NN triple bond for the encapsulated N 2 , as well as an unsymmetric molecular structure for the encapsulated molecule of CO 2 . The IR spectrum of CO 2 @ 2 suggested that the rotation of the encapsulated molecule of CO 2 is partially restricted, which was supported by DFT calculations.