A Phosphine Oxide Functional Group Based [2]Rotaxane That Operates as a Multistable Molecular Shuttle.

A switchable [2]rotaxane based on a pyridinediamide crown ether macrocycle and a thread bearing phosphine oxide, urea, and dibenzylammonium functional groups was successfully developed and characterized by (1) H NMR and 2D NMR spectroscopy, mass spectrometry, and single-crystal analysis. The three recognition sites in the [2]rotaxane were sorted from strong to weak, according to their bonding abilities, so that the macrocycle could move along the thread from one side to the other in a directional way, operating as a multistable molecular shuttle.