Triptycene‐Derived Oxacalixarenes as New Wheels for the Synthesis of [2]Rotaxanes: Acid–Base‐ and Metal‐Ion‐Switchable Complexation Processes

A pair of triptycene‐derived oxacalixarenes, 1 a and 1 b , containing two naphthyridine subunits have been synthesized by a convenient one‐pot approach. Macrocycles 1   a and 1   b are diastereomers, with 1   a being a cis isomer with a boat‐like 1,3‐alternate conformation and 1   b being a trans isomer with a curved boat‐like conformation in the solid state. Both 1   a and 1   b have fixed conformations in solution at room temperature, as revealed by variable‐temperature 1 H NMR spectroscopy experiments. It was found that oxacalixarenes 1   a and 1   b could both form 1:1 [2]pseudorotaxane‐type complexes with paraquat derivatives with different functional groups in solution and in the solid state, which resulted in the further synthesis of a pair of novel isomeric [2]rotaxanes. Moreover, the controlled dethreading and rethreading processes of the [2]pseudorotaxanes were also easily achieved by acid–base stimuli or Hg 2+ association/dissociation.