Synthesis and anion coordination chemistry of new calix[4]arene pyridinium receptors

Abstract

New lower rim substituted calix[4]arene bis-pyridinium receptors L¹, L² and a novel lower rim bridged calix[4]arene pyridinium receptor L³ have been prepared and shown to bind a variety of anionic guest species. Proton NMR titration studies in deuteriated DMSO solutions reveal L¹ and L² to complex H₂PO₄⁻, Cl⁻, Br⁻, HSO₄⁻ anions with L∶2X⁻ stoichiometry with L¹ exhibiting a selectivity preference for H₂PO₄⁻. L³ forms 1∶1 stoichiometric complexes with Cl⁻ and Br⁻ of similar stability. Cyclic voltammetric investigations have demonstrated L¹ to electrochemically recognise H₂PO₄⁻ and Cl⁻ anions.