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Organotin‐Substituted Crown Ethers for Ditopic Complexation of Anions and Cations

“…66.5(2) O(5)-Na-(O4) 67.5 (2) to the sodium cation with an Na-N distance of 2.344(9) Å. The tin atom shows the expected tetrahedral configuration.…”

“…[1,2] Practical applications of ion-pair recognition range from complexation of zwitterionic amino acids and peptides, [3,4] the transport of ion pairs across biological membranes [5][6][7][8][9][10][11][12] to solubility enhancement of ion pairs in nonpolar solvents for ion extraction. [13] Ion-pair receptors known so far are based on the combination of crown compounds or calixarenes with (i) ammonium groups exploiting hydrogen bonding [14,15] or (ii) Lewis acidic groups.…”

Cooperative Binding of Calix[4]pyrrole–Anion Complexes and Alkylammonium Cations in Halogenated Solvents

“…[1][2][3][4][5][6] A few of these receptors have also been studied in conjunction with cation receptors in the form of binary mixtures, [7][8][9][10][11][12][13] or even more effectively as ditopic ion-pair receptors, [5,14,15] and have been shown to bind ion pairs as contact ion-pairs [7,[16][17][18][19] or spatially separated ion pairs. [20] An advantage of an ion-pair receptor over a simple ion receptor is that the number of competing interactions in solution (i.e., the formation of cation-anion pairs) is reduced.…”

Ion‐Pair Recognition by Ditopic Macrocyclic Receptors

“…The X-ray structure suggests that the macrocyclic cavity can only accommodate alkylammonium cations with small or narrow alkyl groups. This hypothesis was tested by measuring the ability of receptor 13 to bind various alkylammonium chloride salts in 85:15 CDCl 3 :DMSO-d 6 , a solvent system where host/guest exchange is rapid on the NMR time scale. As shown in Table 1, the association constant for NBu 4 •Cl is 50 M -1 .…”

“…In other words, a heteroditopic receptor that can simultaneously bind both of the salt ions. The chronological development of salt receptors has been reviewed a number of times in the past few years, [2][3][4][5][6] and so the exercise will not be repeated here. Instead, the chapter will focus on the more specific topic of ion-pair recognition.…”