Abstract

The performance of chloride-selective electrodes based on "two-wall" aryl-extended calix4pyrroles and multiwall carbon nanotubes is presented. The calix4pyrrole receptors bear two phenyl groups at opposite meso-positions. When the meso-phenyl groups are decorated with strong electron-withdrawing substituents, attractive anion-π interactions may exist between the receptor's aromatic walls and the sandwiched anion. These anion-π interactions are shown to significantly affect the selectivity of the electrodes. Calix4pyrrole, bearing a π-nitro withdrawing group on each of the meso-phenyl rings, afforded sensors that display anti- Hofmeister behavior against the lipophilic salicylate and nitrate anions. Based on the experimental data, a series of principles that help in predicting the suitability of synthetic receptors for use as anion-specific ionophores is discussed. Finally, the sensors deliver excellent results in the direct detection of chloride in bodily fluids. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.