Topological and metal ion effects on the anion binding abilities of new heteroditopic receptors derived from p-tert-butylcalix[4]arene

Article abstract of DOI:10.1016/j.tetlet.2011.04.014

Two derivatives of p-tert-butylcalix[4]arenes 1 and 2 containing diethyl ester and amidoferrocene units as cation and anion binding sites, respectively, have been synthesized. Both compounds were isomeric with different topology for accommodating ions. ¹H NMR spectroscopy, cyclic voltammetry, and square-wave voltammetry were used to study the binding abilities of receptors 1 and 2 toward anions. Both receptors were found to bind Br^- and I ^- selectively in the presence of Na⁺. The electrochemically oxidized ferrocenium form of para-isomer 2 in the free form was found to sense AcO^- selectively, but demonstrated a negative sensing in the presence of Na⁺. In contrast, the electrochemically oxidized ferrocenium form of meta-isomer 1 was found to enhance sensing of AcO^- and Cl^- in the presence of Na⁺.