title: Synthesis and metal ion complexation studies of proton-ionizable calix
abstract: A series of novel N-chromogenic calix[4]arene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calix[4]arene azacrown ethers were prepared by reacting 25,27-dipropyloxy-26,28-bis(5-chloro-3-oxapentyloxy) calix[4]arenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calix[4]arene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calix[4]arene azacrown ether in moderate yield. These compounds show high potassium selectivity over other metal ions as shown by two-phase extraction, bulk liquid membrane, and 1H NMR studies on a ligand-metal complex. It is assumed that the OH of the chromogenic group attached on nitrogen can assist the complexation by encapsulation of the metal.
authors.affiliation: Department of Chemistry, Konyang University, Nonsan, Korea.
authors.initials: JS
authors.lastname: Kim
authors.initials: OJ
authors.lastname: Shon
authors.initials: JW
authors.lastname: Ko
authors.initials: MH
authors.lastname: Cho
authors.initials: IY
authors.lastname: Yu
authors.initials: J
authors.lastname: Vicens