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-pi 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 (K-1:1) ranging from 1.33 x 10(3) to 3.52 x 10(3) M-1.