He INCORPORATION INTO SMALL CAGE COMPOUNDS: A COMPUTATIONAL STUDY

Abstract

Endohedral cage compounds have been considered as possible candidate species for molecular memories. One class of such endohedrals is represented by cage complexes with encapsulated He. They have been vigorously studied and recently He@C 20 H 20 has been prepared as the yet smallest member of the family. In this report, computations are carried out on three hypothetical endohedral systems: He@C 14 H 16 (iso-garudane and garudane cages), He@C 20, and compared with the available He@C 60 and He@C 20 H 20 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@C 14 H 16 must obviously be less likely than He@C 20 H 20 as they require a larger cage expansion. The computed 3He NMR shifts are quite sensitive to the cage environment. Kinetic stabilization of He-encapsulates is also discussed.