Calix[4]arene dibenzocrown ethers as caesium selective extractants

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