Helium endohedral fullerene study

It might be mentioned that there is quite a large empty space in the interior of the fullerene molecule. It has proven possible to trap various rare-gas atoms and small molecules within the fullerene interior, and the subject has been studied in some detail. Helium and argon, for example, can be inserted into the fullerene cage at high temperatures and pressures. The resulting structures are referred to as endohedral complexes, and they can be identified by mass spectrometry. ... 

Helium ( He) (/= 1/2). The endohedral NMR chemical shifts of various known H2-H2O- and NH3-encapsulated fullerene compounds were calculated at the GIAO-B3LYP/3-21G and GIAO-HF/3-21G levels of theory with AMI- and PM3-optimised structures. The shift tendency of endohedral NMR chemical shifts were discussed and compared with that of endohedral He NMR chemical shifts.The equilibrium geometries and relative stabilities of the 19 possible isomers of C84O were studied... 

He C6o and He C7o The He NMR spectra of endohedral helium atoms were used to monitor the aromaticity of the fullerenes as a function of electron addition upon reduction. The reduction of He C6o and He C7o to their hexaan-ions was followed by a study of their He shifts [17]. The reduction was carried out with Li metal (in the presence of 2), and the NMR spectra of the anions were... 

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