Synthesis and Extraction Properties of p-tert-Butylcalix[4]arenes with Crown-5 Ether Substituents

A series of novel lower rim calix[4] arene receptors with crown ethers moieties, i.e. 2-4, 6, 8, each of which contains 15-crown-5 ether fragment, was synthesized. The complexation properties of obtained compounds were determined through the series of alkali, alkaline earth and some transition metal picrate extraction experiments. Calixarenes with two N-carbonylaza(or benzoaza) crown-5 ether units (2, 3) are efficient extractants for alkali metal ions whereas ligands with 4-amidobenzocrown-5 ether moieties show a binding ability toward some divalent cations. The tetrasubstituted calix[4] arene 6 is an effective but non selective extractant for studied metal picrates under experimental conditions with the ligand-cation ratio 1:1.