Lower rim substituted tert-butyl calix[4]arenes (I).: The structure and complexing properties in ion-selective PVC membrane electrodes

Some di- and tetraamide tert-butylcalix[4]arenes were synthesized and described. Their ionophoric properties were studied in liquid membrane ion-selective electrodes. The correlation between the chemical structure (conformation in solution determined by H-1 NMR) and potentiometric ion-selectivity and complex formation constant have been studied. The PVC membrane electrodes based on tetraamides 8-11 show high sodium selectivity, are stable and long lasting. Disubstituted amides 1-7 are selective for larger and more lipophilic ions, as for example guanidinium ion. The crystal structure of the diamide 4 was determined by single crystal X-ray analysis. Crystals of 4 are triclinic, space group P-1, with: a = 16,669(8), b = 17.795(10), c = 20.984(8) Angstrom, alpha = 91.08(4)degrees, beta = 91.60(3)degrees, gamma = 90.73(4)degrees and Z = 4. Ionophore 4 posseses a distorted cone conformation and is substituted at the proximal phenol rings.