title: Allosteric effects in a tetrapodal imidazolium-derived calix[4]arene anion receptor.
abstract: A ditopic tetrapodal imidazolium-based 1,3-alternate calix[4]arene host binds anions as 1 : 2 complexes via a range of CH...anion hydrogen bonds. Allosteric enhancement of the affinity for the second chloride anion is observed. X-Ray crystal structures of the chloride, bromide and nitrate complexes suggest that this behaviour is linked to inter-binding site communication mediated by the calixarene framework. The imidazolium groups exist as either in-out or out-out conformers with respect to the calixarene, with the chloride complex exhibiting conformational isomorphism such that both forms are present in the same crystal structure.
authors.affiliation: School of Chemistry, University of Leeds, Leeds, UK LS2 9JT.
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Willans
authors.forename: Kirsty M
authors.initials: KM
authors.lastname: Anderson
authors.forename: Lydia C
authors.initials: LC
authors.lastname: Potts
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Steed
mesh_terms: D000838:Anions / Q000737:chemistry; D001965:Bromides / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*
chemical_list: D000838:Anions; D001965:Bromides; D002712:Chlorides; D007093:Imidazoles; D009566:Nitrates; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes