Direct Detection of the Ion Pair to Free Ions Transformation upon Complexation with an Ion Receptor in Non-Polar Solvents by using Conductometry

作者：Iseda Kazuya; Kokado Kenta^*; Sada Kazuki^*

来源：ChemistryOpen, 2018, 7(3): 269-274.

DOI：10.1002/open.201800014

• anions
• host-guest systems
• molecular recognition
• receptors
• supramolecular chemistry

In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride (TBACl) ion-pair salt to the free ions through complexation with meso-octamethylcalix[4]pyrrole (CP), which is a well-known receptor for chloride anions. In the presence of CP, the conductivity of TBACl increases in various non-polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non-polar solvents. In other words, CP recognizes chloride as an ion-paired salt as well as a free anion in non-polar solvents. Additionally, the TBA(CP-Cl) complex exhibited a considerably lower ion-pairing constant (K-ip) than TBACl in non-polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli-responsive soft materials in organic solvents using coulombic forces.

• 出版日期2018-3