Endohedral cage compounds have been considered as possible candidate species for molecular memories. Such endohedrals are represented by cage complexes with encapsulated He, Li, N, etc. They have been vigorously studied and recently He@C20H20 has been prepared as the yet smallest member of the family (Cross, Saunders, Prinzbach, Org. Lett. 1 (1999) 1479). In this report, computations are carried out on several hypothetical endohedral system: He@C14H16 (isogarudane and garudane cages), He@C20, He@C36 (D6h & D2d cages), Li@C36, N@C36 and compared with the available He@C60, He@C20H20, Li@C60, N@C60 species. Geometry optimizations are followed by computations of 3He NMR shifts - a useful tool for observation of He-encapsulates. The geometry optimizations can produce local energy minima for the endohedral systems, though He@C14H16 must obviously be less likely than He@C20H20 as they require a larger cage expansion. The computed 3He NMR shifts are quite sensitive to the cage environment. Kinetic stabilization of the encapsulates is also evaluated.
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