Allosteric effects in a tetrapodal imidazolium-derived calix[4]arene anion receptor.
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.
Willans
Charlotte E
CE
School of Chemistry, University of Leeds, Leeds, UK LS2 9JT.
Anderson
Kirsty M
KM
Potts
Lydia C
LC
Steed
Jonathan W
JW
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*
D000838:Anions; D001965:Bromides; D002712:Chlorides; D007093:Imidazoles; D009566:Nitrates; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes