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Chloride-selective electrodes based on "two-wall" aryl-extended calix[4]pyrroles: combining hydrogen bonds and
Jad Sabek1, Louis Adriaenssens, Tomàs Guinovart
1Department of Analytical and Organic Chemistry, Rovira i Virgili University, Marcel⋅lí domingo s/n, 43007 Tarragona (Spain); Institute of Chemical Research of Catalonia (ICIQ), Avda. Països Catalans 16, 43007 Tarragona (Spain).
Abstract:
The performance of chloride-selective electrodes based on "two-wall" aryl-extended calix[4]pyrroles and multiwall carbon nanotubes is presented. The calix[4]pyrrole 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. Calix[4]pyrrole, bearing a p-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.
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