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Dual Binding Mode of Methylmethanetriacetic Acid to Tripodal Amidopyridine Receptors

A series of tripodal amidopyridine receptors capable of selective recognition of methylmethanetriacetic acid (MMTA) in organic solvents is described. Intramolecular hydrogen-bonding groups, built into some of the receptors, were designed as preorganization devices. Binding was studied by NMR titrati...

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Bibliographic Details
Published in:Journal of organic chemistry 2002-12, Vol.67 (25), p.8832-8841
Main Authors: Ballester, Pablo, Capó, Magdalena, Costa, Antoni, Deyà, Pere M, Gomila, Rosa, Decken, Andreas, Deslongchamps, Ghislain
Format: Article
Language:English
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Summary:A series of tripodal amidopyridine receptors capable of selective recognition of methylmethanetriacetic acid (MMTA) in organic solvents is described. Intramolecular hydrogen-bonding groups, built into some of the receptors, were designed as preorganization devices. Binding was studied by NMR titration, variable temperature NMR experiments, 2D-NMR, isothermal titration calorimetry, and single-crystal X-ray crystallography. The results reveal that a balancing act between inter- and intramolecular hydrogen-bonding interactions in the complexes governs both the dynamics and the geometry of binding. Receptor 1b (without intramolecular hydrogen-bonding groups) features a simple symmetric MMTA binding geometry with optimal enthalpic interactions. In sharp contrast, receptor 1a (with intramolecular hydrogen-bonding groups) reveals a temperature-dependent dual binding mode where MMTA can bind in two completely different geometries. The two solution binding geometries of 1a·MMTA were unraveled by NMR experiments and correlated to the X-ray structures.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo025787l