A Novel Ditopic Receptor and Reversal of Anion Binding Selectivity in the Presence and Absence of Bound Cation

Tumcharern, Gamolwan; Tuntulani, Thawatchai; Coles, Simon J.; Hursthouse, M. B.; Kilburn, Jeremy D.

doi:10.1021/ol035894h

Cited by 83 publications

(28 citation statements)

References 11 publications

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“…To permit anion recognition, two urea moieties were introduced onto the calix [4] In 2003, Kilburn and coworkers reported ditopic receptor 1.29 (Figure 1.14), a system that coordinates alkali metal cations via the oxygen atoms, while binding the anion in a hydrogen bonding donor pocket formed by the two thiourea groups. 44 In the absence of the Na + cation, receptor 1.29 binds the acetate anion selectively over the diphenyl phosphate anion. However, in the presence of the Na + cation, the selectivity is reversed.…”

Section: Ion Pair Receptors Based On Urea Groups For Anion Recognitionmentioning

confidence: 99%

Calix[4]pyrrole-Based Ion Pair Receptors

2014

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Ion pair receptors, which are able to bind concurrently both a cation and an anion, often display higher selectivity and affinity for specific ion pairs than simple ion receptors capable of recognizing primarily either a cation or an anion. This enhancement in recognition function is attributable to direct or indirect cooperative interactions between cobound ions via electrostatic attractions between oppositely charged ions, as well as to positive allosteric effects. In addition, by virtue of binding the counterions of the targeted ion, ion pair receptors can minimize the solvation of the counterions, which can otherwise have a negative effect on the interactions between the receptors and the targeted ions. As a result of their more favorable interactions, ion pair receptors are attractive for use in applications, such as extraction and sensing, where control of the binding interactions is advantageous. In this Account, we illustrate this potential in the context of ion pair receptors based on the calix[4]pyrrole scaffold. Both simple ditopic ion pair receptors, containing sites for the recognition of a single anion and single cation, and so-called multitopic ion pair receptors will be discussed. The latter systems differ from conventional, so-called ditopic ion pair receptors in that they contain more than one binding site for a given targeted ion (e.g., a cation). This permits a level of selectivity and control over binding function not normally seen for simple ion or ion pair receptors containing one or two binding sites, respectively. Calix[4]pyrroles are macrocyclic compounds consisting of four pyrrole units linked via fully substituted sp 3 hybridized meso carbon atoms. They are effective receptors for Lewis basic anions (e.g., halides) in typical organic media and under certain conditions will recognize ion pairs containing charge diffuse cations, such as a small alkylammonium, imidazolium, or cesium cations. The calix[4]pyrrole framework is further attractive in that it is relatively easy to modify. In particular, functionalization of the β-pyrrolic carbon and meso-carbon atoms with simple crown ethers or calix[4]arene crown ethers can produce heteromultitopic ion pair receptors containing more than two cation binding sites. This allows the interactions between receptors and ions to be manipulated on a higher level than can be achieved using simple ion receptors or heteroditopic ion pair receptors and has made these systems attractive for use in ion transport, recognition, and extraction. Recent progress in developing calix[4]pyrroles as both multitopic and more conventional ion pair receptors is summarized in this Account. The emphasis will be on our own work.

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Section: Ion Pair Receptors Based On Urea Groups For Anion Recognitionmentioning

confidence: 99%

Calix[4]pyrrole-Based Ion Pair Receptors

2014

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“…[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.…”

Section: Introductionmentioning

confidence: 99%

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

Gross

Schmidtchen

Antonius

et al. 2008

Chemistry A European J

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Calix[4]pyrrole–chloride interactions are affected not only by the choice of countercation in halogenated solvents, but show a specific dependence on the way in which these cations are bound within the electron rich, bowl‐like calix[4]pyrrole cavity formed upon chloride anion complexation. In dichloromethane, the affinities of simple meso‐octamethylcalix[4]pyrrole (1) for methyl‐, ethyl‐, and n‐butylammonium chlorides are on the order of 105, 104, and 102 M−1, respectively, as determined from isothermal titration calorimetry (ITC) analyses. These cation‐dependent anion affinity effects, while clearly evident, are less pronounced in other halogenated solvents, such as 1,2‐dichloroethane. Support for the proposed cation complexation selectivity is provided by solid state X‐ray crystallographic analyses.

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“…A more recent example is Kilburn's ditopic receptor 3 which coordinates the metal cation via the calixarene oxygens, and binds the anion in a hydrogen bonding pocket formed by the two thiourea groups. [9] A conceptually different receptor for separated ions is Gellman's macrocyclic phosphine oxide 3. [10] Hydrogen bonding with a monoalkylammonium cation on one face of the macrocycle induces receptor polarization and preorganization which promotes association with a Cl -counter-ion on the reverse face.…”

Section: Ditopic Receptors For Separated Ionsmentioning

confidence: 99%