Recognition and Extraction of Cesium Hydroxide and Carbonate by Using a Neutral Multitopic Ion-Pair Receptor

Current approaches to lowering the pH of basic media rely on the addition of a proton source. An alternative approach is described herein that involves the liquid-liquid extraction-based removal of cesium salts, specifically CsOH and Cs₂ CO₃ , from highly basic media. A multitopic ion-pair receptor (2) is used that can recognize and extract the hydroxide and carbonate anions as their cesium salts, as confirmed by ¹ H NMR spectroscopic titrations, ICP-MS, single-crystal structural analyses, and theoretical calculations. A sharp increase in the pH and cesium concentrations in the receiving phase is observed when receptor 2 is employed as a carrier in U-tube experiments involving the transport of CsOH through an intervening chloroform layer. The pH of the source phase likewise decreases.