A "through-shell" binding isotope effect

(Graph Presented) Small, but very significant: Partial separation of two hemicarceplexes which differed only in the degree of guest deuteration could be achieved by normal-phase chromatography (see picture). The difference in retention time arises from a variation in the interaction between the hemicarceplex and the silica surface as a consequence of a 0.005-Å difference in the C-H and C-D bond lengths of the guest molecules.