Calix[4]arene dibenzocrown ethers as caesium selective extractants

Abstract

A series of 1,3-dialkyloxycalix[4]arene dibenzocrown ethers were synthesized in the fixed 1,3-alternate conformation with good yields by the reaction of 1,3-dialkyloxycalix[4]arenes with dibenzodimesylate in the presence of caesium carbonate. The three dimensional 1,3-alternate conformation was confirmed by X-ray crystal structure. Upon two phase extraction, NMR studies on the ligand–metal complex, single ion and competitive ion transport experiments through a bulk liquid membrane, 1,3-dipropyloxycalix[4]arene dibenzocrown-6, in which two benzo groups are symmetrically attached to the crown-6 linkage, gave one of the most efficient and selective extractabilities for caesium ion over other alkali metal ions. From supported liquid membrane experiments using 1 and 3 as organic carriers, permeation coefficients of the caesium ion were estimated to be 0.42 and 0.27 cm h–1, respectively. The selectivity of caesium over sodium ion was observed to increase with permeation time.