Synthesis and Anion‐Binding Properties of Novel Redox‐Active Calixarene Receptors

Abstract

AbstractA novel synthetic approach towards redox‐active calixarene‐based receptors is described in which ferrocene fragments were introduced at the lower rim through anion‐binding urea or amide connections. These derivatives were prepared in one pot by treating an amine‐containing calixarene with ferrocenecarboxylic acid in the presence of diphenylphosphoryl azide and diisopropylethylamine. This method allows a convergent approach to these receptors and is readily adaptable to the introduction of other urea substituents. The anion‐binding properties of these artificial receptors have been revealed by NMR spectroscopy and thoroughly investigated by electrochemical methods. We have assessed the importance of the urea–phosphate bonds in the observed electrochemical response by studying receptors in which the ferrocene reporters and binding fragments are closely associated or fully disconnected through a long alkyl chain. The experimental results clearly show the utmost importance of ion‐pairing effects in the electrochemical recognition process, which account for most of the transduction signal in organic apolar media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)