title: Kinetic and Thermodynamic Stabilization of Metal Complexes by Introverted Coordination in a Calix[6]azacryptand.
abstract: The Huisgen thermal reaction between an organic azide and an acetylene was employed for the selective monofunctionalization of a X6 -azacryptand ligand bearing a tren coordinating unit [X6 stands for calix[6]arene and tren for tris(2-aminoethyl)amine]. Supramolecular assistance, originating from the formation of a host-guest inclusion complex between the reactants, greatly accelerates the reaction while self-inhibition affords a remarkable selectivity. The new ligand possesses a single amino-leg appended at the large rim of the calixarene core and the corresponding Zn(2+) complex was characterized both in solution and in the solid state. The coordination of Zn(2+) not only involves the tren cap but also the introverted amino-leg, which locks the metal ion in the cavity. Compared with the parent ligand deprived of the amino-leg, the affinity of the new monofunctionalized X6 tren ligand 6 for Zn(2+) is found to have a 10-fold increase in DMSO, which is a very competitive solvent, and with an enhancement of at least three orders of magnitude in CDCl3 /CD3 OD (1:1, v/v). In strong contrast with the fast binding kinetics, decoordination of Zn(2+) as well as transmetallation appeared to be very slow processes. The monofunctionalized X6 tren ligand 6 fully protects the metal ion from the external medium thanks to the combination of a cavity and a closed coordination sphere, leading to greater thermodynamic and kinetic stabilities.
authors.affiliation: Laboratoire de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/06, 1050, Brussels, Belgium.|Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/08, 1050, Brussels, Belgium.|Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicologiques (CNRS UMR 8601), Université Paris Descartes Sorbonne Paris Cité, 45 rue des Saints-Pères, 75006, Paris, France.
authors.forename: Alex
authors.initials: A
authors.lastname: Inthasot
authors.affiliation: Laboratoire de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/06, 1050, Brussels, Belgium.|Ingénierie des Nanosystèmes Moléculaires, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP165/64, 1050, Brussels, Belgium.
authors.forename: Emilio
authors.initials: E
authors.lastname: Brunetti
authors.affiliation: Laboratoire de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/06, 1050, Brussels, Belgium.
authors.forename: Manuel
authors.initials: M
authors.lastname: Lejeune
authors.affiliation: Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicologiques (CNRS UMR 8601), Université Paris Descartes Sorbonne Paris Cité, 45 rue des Saints-Pères, 75006, Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Menard
authors.affiliation: Laboratoire de Cristallographie et de Résonance Magnétique Nucléaire Biologiques, (CNRS UMR 8015), Université Paris Descartes Sorbonne Paris Cité, 4, Avenue de l'Observatoire, 75006, Paris, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Prangé
authors.affiliation: Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/08, 1050, Brussels, Belgium.|Unité de Chimie des Nanomatériaux (CNANO), Université de Namur, 61 rue de Bruxelles, 5000, Namur, Belgium.
authors.forename: Luca
authors.initials: L
authors.lastname: Fusaro
authors.affiliation: Ingénierie des Nanosystèmes Moléculaires, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP165/64, 1050, Brussels, Belgium.
authors.forename: Gilles
authors.initials: G
authors.lastname: Bruylants
authors.affiliation: Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicologiques (CNRS UMR 8601), Université Paris Descartes Sorbonne Paris Cité, 45 rue des Saints-Pères, 75006, Paris, France. olivia.reinaud@parisdescartes.fr.
authors.forename: Olivia
authors.initials: O
authors.lastname: Reinaud
authors.affiliation: Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/08, 1050, Brussels, Belgium. mluhmer@ulb.ac.be.
authors.forename: Michel
authors.initials: M
authors.lastname: Luhmer
authors.affiliation: Laboratoire de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F.D. Roosevelt 50, CP160/06, 1050, Brussels, Belgium. ijabin@ulb.ac.be.
authors.forename: Ivan
authors.initials: I
authors.lastname: Jabin
authors.affiliation: Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicologiques (CNRS UMR 8601), Université Paris Descartes Sorbonne Paris Cité, 45 rue des Saints-Pères, 75006, Paris, France. benoit.colasson@parisdescartes.fr.
authors.forename: Benoit
authors.identifier: http://orcid.org/0000-0002-7595-2116
authors.initials: B
authors.lastname: Colasson
keywords: calixarenes; coordination chemistry; host-guest systems; selective functionalization; supramolecular chemistry