Protonation of a Spherical Macrotricyclic Tetramine: Water Inclusion, Allosteric Effect, and Cooperativity.
Fiche publication
Date publication
juillet 2018
Journal
ChemPlusChem
Auteurs
Membres identifiés du Cancéropôle Est :
Pr LEHN Jean-Marie
Tous les auteurs :
Graf E, Harrowfield J, Kintzinger JP, Lehn JM, Le Moigne J, Rissanen K
Lien Pubmed
Résumé
The spherical macrotricyclic cryptand tetramine "C24" (1) displays remarkable protonation behaviour. It undergoes protonation in four successive steps for which pK values of 11.17±0.05, 10.28±0.04, 6.00±0.06 and 3.08±0.08 have been determined at 298 K. The unusually close values for the first two protonations provide evidence for the encapsulation of a water molecule serving as effector for the second protonation, which is consistent with earlier observations that the exchange of protons bound in the diprotonated species with solvent protons is unusually slow and that O NMR spectra show the presence of an oxygen centre in the same species quite distinct from that of solvent water. Encapsulation of water is also observed in the solid state in the picrate salt of the triprotonated form of 1 and has been characterised by means of X-ray structural determination.
Mots clés
cooperative effects, cryptands, hydrogen bonds, macrocycles, protonation
Référence
Chempluschem. 2018 Jul;83(7):605-611