Synthesis of [2]Rotaxane‐Based pH‐Responsive Molecular Switch Involving a [23]Crown Ether Wheel, Dibenzylammonium and Methyl Triazolium Recognition Stations

Abstract A bistable [2]rotaxane based on dibenzylammonium (DBA + )/methyl triazolium (MTA + ) stations and [23]crown ether (X23C7) wheel component has been obtained in excellent yield. The crown ether X23C7 predominantly occupies the DBA + station, in the bistable [2]rotaxane. On addition of the base, the crown ether X23C7 shuttles across to the MTA + station. Acid treatment led to the restoration of X23C7 back to the DBA + station. Due to this reversibility, a pH‐responsive molecular switch has been obtained. This is the first example of a [23]crown ether, a smaller analogue of [24]crown ether, exhibiting shuttling motion in any crown ether‐based mechanically interlocked molecules.