The synthesis and complexation of novel azosubstituted calix[4]arenes and thiacalix[4]arenes

Novel calix[4]arene/thiacalix[4]arene derivatives bearing arylazo moieties were prepared via a diazo-coupling reaction. Subsequent alkylation with ethyl bromoacetate via the template effect of alkali metal carbonates resulted in arylazo substituted calix[4]arene/thiacalix[4]arene tetraacetates. UV–vis spectroscopy revealed that in terms of their binding affinity towards alkali metal cations, the tetraacetate derivative displayed considerable selectivity for sodium cations (KNa+/KK+>100KNa+/KK+>100, KNa+/KLi+>175KNa+/KLi+>175).