Synthesis and Structure of Upper-Rim 1,3-Alternate Tetraoxacalix[2]arene[2]triazine Azacrowns and Change of Cavity in Response to Fluoride Anion

The upper-rim 1,3-alternate tetraoxacalix[2]arene[2]triazine azacrowns were constructed effectively by macrocyclic condensation reaction of diamines with dichlorinated tetraoxacalix[2]arene[2]triazine intermediates that were synthesized from the stepwise fragment coupling reactions of 3,5-dihydroxybenzoic acid esters with cyanuric chlorides. Because of the formation of conjugation of amino groups with triazine rings, tetraoxacalix[2]arene[2]triazine azacrowns existed in a mixture of syn- and anti-isomeric forms. Both fluorescence titration and 1H NMR spectroscopic study showed that tetraoxacalix[2]arene[2]triazine azacrowns interacted with fluoride anion, leading to cavity changes of the host molecules.