Two new tetraamide calix[4](aza)crowns (4a, 4b) were synthesized and characterized by ~1H NMR, MS-FAB and elemental analysis. The interactions of the hosts with some anions were studied by UV-vis spectra. The stability constants were determined. The results indicate that the tetraamide calix[4] (aza) crowns (4a, 4b) have higher selective recognition for a planar anion (p-O_2NC_6H_4O~-) as compared to tetrahedral anions (p-O_2NC_6H_4OPO_3~(2-) and H_2PO_4~- ). The hosts (4a, 4b) and p-O_2NC_6H_4O~- formed 1 : 1 complex, respectively.

Key words: AMIDES P, calixarene, CROWN ETHER, UV, 1HNMR, MS, ELEMENTAL ANALYSIS