Synthesizing [2]Rotaxanes and [2]Catenanes through Na(+)-Templated Clipping of Macrocycles around Oligo(ethylene glycol) Units.

Di-, tri-, and tetra(ethylene glycol) units in both dumbbell-shaped and macrocyclic molecules can be used as primary recognition units for the clipping of macrocycles in the presence of templating Na(+) ions to form corresponding [2]rotaxanes and [2]catenanes. One such tri(ethylene glycol)-containing [2]catenane behaves as a Na(+) ion-controllable molecular switch.

Molecular switch based on very weak association between BPX26C6 and two recognition units.

A [2]rotaxane has been constructed through metal ion-templated pseudorotaxane formation from a weakly interacting host (bis-p-xylyl[26]crown-6)/guest (diphenylurea derivative) complex and post-assembly modification to form another weakly interacting tertiary ammonium ion recognition site for the host. The combination of this pair of weakly interacting components allowed bifunctional (pH, Na(+) ions) switching of the crown ether unit, highlighting the potential applicability of weakly associated components within molecular switches.