The synthesis of some pyridyl functionalized calix[4]arenes as the sensor molecule for silver ion-selective electrodes

Abstract

25,27-Bis(6-hydroxymethyl-2-pyridylmethoxy)-26,28-dipropoxycalix[4]arene 3, its derivative 4 and 25,27-bis(6-diphenylphosphinomethylpyridylmethoxy)-26,28-dipropoxy-5,11,17,23-tetra-tert-butylcalix[4]arene 6 have been synthesized and characterized by ¹H NMR spectroscopy and elemental analysis. The X-ray crystallographic structure was obtained for 4 and shows an infinite sheet aggregate through intermolecular hydrogen bonds and bridged methanol molecules in the solid state. Ion-selective electrodes (ISE) for Ag⁺ containing 3, 4 and 6 as neutral ionophores in a PVC membrane were prepared and their selectivity coefficients for Ag⁺ (K^pot_Ag,M) were investigated against other alkali metal, alkaline-earth metal, lead, ammonium ions and some transition metal ions using the mixed-solution method. These ISEs showed excellent Ag⁺ selectivity towards most of the interfering cations examined, except for Hg²⁺ which has a relativly low interference (log K^pot_Ag,M ≤ −1.5).