Squaramido-based receptors: Molecular recognition of carboxylate anions in highly competitive media

Prohens, Rafel; Tomàs, Salvador; Morey, Jeroni; Deyà, Pere M.; Ballester, Pablo; Costa, Antoni

doi:10.1016/s0040-4039(97)10728-6

Cited by 89 publications

(51 citation statements)

References 17 publications

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“…Atoms of the two non-equivalent receptoranion complexes were named by adding a final "a" and "b" suffix to the same atom-naming scheme. [8] Acceptor atom 7(32) Br (1) with the "b" suffix. Each "a" and "b" centrosymmetrically related pair is characterised by two face-to-face p-stacked phenyl rings that show the same value of the centroid-centroid distance: 3.70(1) for the "a" molecular couple and 3.72(1) for the "b" molecular couple.…”

Section: Resultsmentioning

confidence: 99%

“…[6] It has been recently demonstrated that synthons that contain covalently linked bipyridine and urea fragments, which profit from the template effect of four Ni II ions, self-assemble to encapsulate a sulfate ion in water, thereby forming a complex of unprecedented stability. [7] More recently, thanks to the pioneering work of Costas group, [8] another neutral subunit capable of establishing, like complexes with all the investigated anions. X-ray diffraction studies on the chloride and bromide complex salts confirmed the 1:1 stoichiometry and indicated the establishment of bifurcated hydrogen-bond interactions between the squaramide-based receptor and the halide anion that involved both 1) amide NÀH and 2) aryl proximate CÀH fragments, for a total of four bonds.…”

Section: Introductionmentioning

confidence: 99%

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The Squaramide versus Urea Contest for Anion Recognition

Amendola

Bergamaschi

Boiocchi

et al. 2010

Chemistry A European J

185

139

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The interaction of a neutral squaramide-based receptor, equipped with two 4-nitrophenyl substituents (R(sq)), with halides and oxoanions has been studied in MeCN. UV/Vis and (1)H NMR spectroscopy titration experiments clearly indicated the formation of 1:1 hydrogen bonding [R(sq)X](+) complexes with all the investigated anions. X-ray diffraction studies on the chloride and bromide complex salts confirmed the 1:1 stoichiometry and indicated the establishment of bifurcated hydrogen-bond interactions between the squaramide-based receptor and the halide anion that involved both 1) amide N-H and 2) aryl proximate C-H fragments, for a total of four bonds. Probably due to the contribution of C-H fragments, complexes of R(sq) with halides are 1 to 2 orders of magnitude more stable than the corresponding ones with the analogous urea-based receptor that contains two 4-nitrophenyl substituents (R(ur)). In the case of oxoanions, R(sq) forms complexes, the stability of which decreases with the decreasing basicity of the anion (H(2)PO(4) (-)>NO(2) (-) approximately HSO(4) (-)>NO(3) (-)), and is comparable to that of complexes of the urea-based receptor R(ur). Such a behaviour is ascribed to the predominance of different contributions: electrostatic interaction for halides, acid-to-base 'frozen' proton transfer for oxoanions. Finally, with the strongly basic anions F(-) and CH(3)COO(-), R(sq) first gives genuine hydrogen-bond complexes of 1:1 stoichiometry; then, upon addition of a second anion equivalent, it undergoes deprotonation of one N--H fragment, with the simultaneous formation of the dianion hydrogen-bond complexes, [HF(2)](-) and [CH(3)COOHCH(3)COO](-), respectively. In the case of the urea-based derivative R(ur), deprotonation takes place with fluoride but not with acetate. The apparently higher Brønsted acidity of R(sq) with respect to R(ur) reflects the capability of the squaramide receptor to delocalise the negative charge formed on N--H deprotonation over the cyclobutene-1,2-dione ring and the entire molecular framework.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Squaramide versus Urea Contest for Anion Recognition

Amendola

Bergamaschi

Boiocchi

et al. 2010

Chemistry A European J

185

139

View full text Add to dashboard Cite

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“…The enantioselective recognition of chiral carboxylates is also an important goal, because several pharmaceutical compounds possess this functional group. Efficient synthetic receptors for carboxylate anion recognition have been obtained by incorporating in more complex structures charged guanidinium, amidinium, or ammonium groups (2) and neutral H-bonding donor groups such as (thio) ureas (7), pyrroles (8), activated amides (9,10), and trifluoromethyl alcohols (11). Only a few examples are known where natural amino acids are used as binding units in biomimetic receptors for carboxylate recognition (12).…”

mentioning

confidence: 99%

Biomimetic macrocyclic receptors for carboxylate anion recognition based on C -linked peptidocalix[4]arenes

Sansone¹,

Baldini²,

Casnati³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Two neutral macrobicyclic anion receptors 4 and 6, containing a calix[4]arene in the cone conformation, two L-alanine units, and a 2,6-diacylpyridine or a phthaloyl bridge, are described. The x-ray crystal structure of the acetone complexes of the pyridine containing macrocycle 6 shows the four amide NH groups to be in close proximity to the chiral pocket delimited by the pyridine and one aromatic nucleus of the calix[4]arene. This conformation is also the most stable in acetone-d6 solution, as proven by one-and twodimensional NMR spectral measurements. Electrospray ionization-MS and 1 H NMR experiments reveal that the two ligands strongly bind carboxylate anions in acetone solution. H-bonding interactions between the carboxylate anions and the amide NH groups, together with ͞ stacking, are invoked to explain the efficiency and the selectivity of these anion receptors.

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“…Sie sind bereits seit 1998 als effektive Anionenrezeptoren in konkurrierenden Lçsungsmitteln (wie DMSO) bekannt. [28] Seit der Jahrtausendwende wurde über zahlreiche Quadratsäureamid-Anionenrezeptoren berichtet, [29] und es wird angenommen, dass deren Effektivität teilweise auf eine Steigerung der Aromatizität des Quadratsäureamidrings als Folge der Komplexierung des Anions zurückzuführen ist. [30] Dies veranschaulicht ein Vergleich von Diarylquadratsäureamiden und analogen Harnstoffen durch Fabbrizzi und Mitarbeiter.…”

Section: Neue N-h- O-h-und C-h-haltige Rezeptorenunclassified

Supramolekulare Chemie von Anionen: von der Erkennung zur chemischen Anwendung

Evans

Beer

2014

Angewandte Chemie

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Seit der Jahrtausendwende fanden bemerkenswerte Fortschritte bei der Bindung und dem Nachweis von Anionen statt, die teilweise von den Erkenntnissen zur Ausnutzung von Wasserstoffbrücken ebenso wie den zuvor selten eingesetzten Anionen‐π‐Wechselwirkungen und Halogenbrücken angetrieben wurden. Die supramolekulare Chemie von Anionen wurde indes substantiell über die Anionenerkennung hinaus weiterentwickelt und umfasst nun verschiedene Disziplinen. Große Fortschritte wurden bei der Synthese von Makrocyclen und ineinandergreifenden molekularen Architekturen mit Anionen als Templaten erzielt, während die Untersuchung von anionischen Transmembrantransportern aus dem Nichts heraus zu einem rasch wachsenden Forschungsgebiet erblühte. Die supramolekulare Chemie der Anionen kam außerdem in verschiedenen Anwendungsbereichen wie der Katalyse, der Ionenextraktion und der Verwendung von Anionen als Impuls für molekulare Systeme zum praktischen Einsatz.

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Squaramido-based receptors: Molecular recognition of carboxylate anions in highly competitive media

Cited by 89 publications

References 17 publications

The Squaramide versus Urea Contest for Anion Recognition

The Squaramide versus Urea Contest for Anion Recognition

Biomimetic macrocyclic receptors for carboxylate anion recognition based on C -linked peptidocalix[4]arenes

Supramolekulare Chemie von Anionen: von der Erkennung zur chemischen Anwendung

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