Salt‐Solubilization and Ion‐Pair Recognition by a Quinoline‐Substituted Crown Ether

Abstract

A novel quinoline‐substituted crown ether has been synthesized as a receptor for ion pairs and its binding behavior was investigated in various solvents. The binding of ion pairs in [D6]DMSO and in mixed [D6]DMSO/CD3CN/CDCl3 solvents was studied and the results revealed positive cooperativity effects. As a novel solubilizing agent, the crown ether can extract halide salts into organic media, especially chloride salts. ESI MS provided evidence for the formation of salt‐receptor complexes. A recycling experiment showed that the receptor can solubilize salts and can be recovered. This process can be performed as a cycle. This study validates the idea that a straightforward combination of a common anion receptor and a well‐studied cation complexation moiety enables the formation of ion‐pair receptors and solubilizers of salts in organic solvents.

Macrocycles as Ion Pair Receptors

“…2-Amido-8-aminoquinolines have been used as backbones for anion recognition. − Recognizing this, Albrecht and co-workers designed a novel receptor 243 (Figure ) that was created by joining a quinoline moiety to an 18-crown-6 ether . Receptor 243 was found to bind halides (as their TBA salts) in CDCl 3 solution per the following affinity sequence: I – < Br – < Cl – .…”

Ion‐Pair Complexation with Dibenzo[21]Crown‐7 and Dibenzo[24]Crown‐8 bis‐Urea Receptors

“…Nevertheless, ion‐pair recognition has attracted a growing interest in supramolecular chemistry and anion/cation recognition. Utilizing ion‐pair receptors in various applications such as salt solubilisation and extraction, membrane transport, catalysis, sensing, and logic gates offers a strong motive to further develop these systems. In spite of the intriguing features of ion‐pair receptors, a surprisingly limited amount of such systems have been developed so far.…”

Lithium halide ion-pair recognition with halogen bonding and chalcogen bonding heteroditopic macrocycles

“…8 The judicious exploitation of heteroditopic molecular receptors, capable of simultaneously binding cationic and anionic species, has demonstrated enormous potential in facilitating the extraction and recovery of a range of transition- [9][10][11][12][13] and alkali-metal salts. [14][15][16][17][18] However, reports of employing this strategy towards extracting lithium salts, in particular, remain scarce. [19][20][21][22][23] In general, heteroditopic receptor design typically relies on crown ether-based cation recognition sites and convergent hydrogen bond donor arrays as anion binding sites.…”