A series of novel N-chromogenic calixarene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calixarene azacrown ethers were prepared by reacting 25,27-dipropyloxy- 26,28-bis(5-chloro-3-oxapentyloxy) calixarenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calixarene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calixarene 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.
ASJC Scopus subject areas
- Organic Chemistry