Tight and Selective Caging of Chloride Ions by a Pseudopeptidic Host
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Otros documentos de la autoría: Martí Vidal, Inés; Bolte, Michael; Burguete, M. Isabel; Vicent Barrera, Cristian; Alfonso Rodríguez, Ignacio; Luis, Santiago V.
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http://dx.doi.org/10.1002/chem.201303604 |
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Título
Tight and Selective Caging of Chloride Ions by a Pseudopeptidic HostAutoría
Fecha de publicación
2014-06Editor
WILEY-VCH Verlag GmbH & Co. KGaAISSN
0947-6539; 1521-3765Tipo de documento
info:eu-repo/semantics/articleVersión de la editorial
http://onlinelibrary.wiley.com/doi/10.1002/chem.201303604/fullPalabras clave / Materias
Resumen
The selective molecular recognition of chloride versus similar anions is a continuous challenge in supramolecular chemistry. We have designed and prepared a simple pseudopeptidic cage (1 a) that defines a cavity ... [+]
The selective molecular recognition of chloride versus similar anions is a continuous challenge in supramolecular chemistry. We have designed and prepared a simple pseudopeptidic cage (1 a) that defines a cavity suitable for the tight encapsulation of chloride. The interaction of the protonated form of 1 a with different inorganic anions was studied in solution by 1H NMR spectroscopy and ESI-MS, and in the solid state by X-ray diffraction. The solution binding data showed that the association constants of 1 a to chloride are more than two orders of magnitude higher than to any other tested inorganic anion. Remarkably, 1 a displayed a high selectivity for chloride over other closely related halides such as bromide (selectivity=111), iodide (selectivity=719), and fluoride (selectivity >1000). Binding experiments (1H NMR spectroscopy and ESI-MS) suggested that 1 a has a high-affinity (inner) binding site and an additional low-affinity (external) binding site. The supramolecular complexes with F−, Cl−, and Br− have been also characterized by the X-ray diffraction of the corresponding [1 a⋅nHX] crystalline salts. The structural data show that the chloride anion is tightly encapsulated within the host, in a binding site defined by a very symmetric array of electrostatic H-bonds. For the fluoride salt, the size of the cage cavity is too large and is occupied by a water molecule, which fits inside the cage efficiently competing with F−. In the case of the bigger bromide, the mismatch of the anion inside the cage caused a geometrical distortion of the host and thus a large energetic penalty for the interaction. This minimalistic pseudopeptidic host represents a unique example of the construction of a simple well-defined binding pocket that allows the highly selective molecular recognition of a challenging substrate. [-]
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Chemistry - A European Journal Vol. 20, no. 24, 2014Derechos de acceso
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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