Threading the Calix[5]arene Annulus

Di-n-alkylammonium ions (such as 2⋅H+) thread the annulus of calix[5]arene 1 to yield stable [2]pseudorotaxanes. The ease of formation of this hitherto unknown family of interpenetrated supermolecules is predominantly determined by salt ion-pairing effects, whereas the time course of the threading/dethreading process depends on the length of the cation alkylammonium chains.