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 (K-Na+/K-K+ > 100, KNa+/K-Li > 175). (c) 2007 Elsevier Ltd. All rights reserved.