Endohedral fullerenes represent caged-clusters of carbon encapsulating metal ions, metal clusters, atoms, and molecules. Although their syntheses mainly rely on physical methods under harsh conditions, organic synthesis has been attracting interests to realize molecule-encapsulating fullerenes owing to high selectivity of fullerene cages and high yields of desired products. The "molecular surgery" was able to be applied to fullerene C70 in spite of difficulties in characterization of products due to the low symmetry compared with C60. Importantly, reflecting the larger inner space than C60, two small molecules were introduced inside open-cage C70 derivatives to afford the corresponding doubly-encapsulating C70 such as (H2O)2@C70[1] and (H2O-HF)@C70[2] in addition to mono-encapsulating H2O@C70 and HF@C70. On the other hand, applying combination of the molecular surgery and ion implantation, doubly-encapsulating (H2-N)@C70 was able to be generated, in which the atomic nitrogen interacts with the hydrogen molecule, without forming covalent bonds.[3]

References
1. Zhang, R.; Murata, M.; Aharen, T.; Wakamiya, A.; Shimoaka, T.; Hasegawa, T.; Murata, Y. Nat. Chem. 2016, 8, 435-441.
2. Zhang, R.; Murata, M.; Wakamiya, A.; Shimoaka, T.; Hasegawa, T.; Murata, Y. Sci. Adv. 2017, 3, e1602833 (6 pages).
3. Morinaka, Y.; Zhang, R.; Sato, S.; Nikawa, H.; Kato, T.; Furukawa, K.; Yamada, M.; Maeda, Y.; Murata, M.; Wakamiya, A.; Nagase, S.; Akasaka, T.; Murata, Y. Angew. Chem. Int. Ed. 2017, 56, 6488-6491.