Synthesis and Structure of Oxacalix[2]arene[2]triazines of an Expanded π-Electron-Deficient Cavity and Their Interactions with Anions

Novel macrocyclic anion receptors based on the principle
of anion−π
interactions were reported. By means of both post-macrocyclization
modification protocol and the stepwise fragment coupling approach,
functionalized oxacalix[2]­arene[2]­triazines bearing two other electron-deficient
(hetero)­aromatic rings on the lower rim were efficiently synthesized.
The resulting oxacalix[2]­arene[2]­triazine macrocycles adopt 1,3-alternate
conformation, yielding therefore an expanded electron-deficient cavity
or space consisting of two triazine rings and two appending aromatic
rings. Spectroscopic titration study showed the selective interaction
of the pentafluorophenyl-substituted oxacalix[2]­arene[2]­triazine with
azide and fluoride in solution with the binding constants (K1:1) ranging from 1.33 × 103 to 3.52 × 103 M–1.