title: Dual binding mode of methylmethanetriacetic Acid to tripodal amidopyridine receptors.
abstract: 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.
authors.affiliation: Departament de Química, Universitat de les Illes Balears, 07071 Palma de Mallorca, Spain. paub@scripps.edu
authors.forename: Pablo
authors.initials: P
authors.lastname: Ballester
authors.forename: Magdalena
authors.initials: M
authors.lastname: Capó
authors.forename: Antoni
authors.initials: A
authors.lastname: Costa
authors.forename: Pere M
authors.initials: PM
authors.lastname: Deyà
authors.forename: Rosa
authors.initials: R
authors.lastname: Gomila
authors.forename: Andreas
authors.initials: A
authors.lastname: Decken
authors.forename: Ghislain
authors.initials: G
authors.lastname: Deslongchamps