Lower rim substituted tert-butyl calix[4]arenes (Part IV).: Calix[4]arene-crown ethers as ionophores in plasticized PVC-membrane electrodes

We present the synthesis and characterization of p-tert-butylcalix[4]arene-crown ethers (compounds 2-4) with different length of the polyethylenoxy bridge between the distal phenolic CH groups. The studied compounds show selectivity for sodium, potassium or cesium ions. The correlation was made between the stereochemical structure of the ligands and potentiometrically determined ion-selectivity and complex formation constants. The crystal and molecular structure of the p-tert-butylcalix[4]arene-crown-5 complex with potassium iodide have been determined by single crystal X-ray diffraction study.