title: Triptycene-derived oxacalixarenes as new wheels for the synthesis of [2]rotaxanes: acid-base- and metal-ion-switchable complexation processes.
abstract: A pair of triptycene-derived oxacalixarenes, 1a and 1b, containing two naphthyridine subunits have been synthesized by a convenient one-pot approach. Macrocycles 1a and 1b are diastereomers, with 1a being a cis isomer with a boat-like 1,3-alternate conformation and 1b being a trans isomer with a curved boat-like conformation in the solid state. Both 1a and 1b have fixed conformations in solution at room temperature, as revealed by variable-temperature (1)H NMR spectroscopy experiments. It was found that oxacalixarenes 1a and 1b 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.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Shu-Zhen
authors.initials: SZ
authors.lastname: Hu
authors.forename: Chuan-Feng
authors.initials: CF
authors.lastname: Chen