title: Calix[4]pyrrole as a chloride anion receptor: solvent and countercation effects.
abstract: The interaction of calixpyrrole with several chloride salts has been studied in the solid state by X-ray crystallography as well as in solution by isothermal titration calorimetry (ITC) and (1)H NMR spectroscopic titrations. The titration results in dimethylsulfoxide, acetonitrile, nitromethane, 1,2-dichloroethane, and dichloromethane, carried out using various chloride salts, specifically tetraethylammonium (TEA), tetrapropylammonium (TPA), tetrabutylammonium (TBA), tetraethylphosphonium (TEP), tetrabutylphosphonium (TBP), and tetraphenylphosphonium (TPhP), showed no dependence on method of measurement. The resulting affinity constants (K(a)), on the other hand, were found to be highly dependent on the choice of solvent with K(a)'s ranging from 10(2)-10(5) M(-1) being recorded in the test solvents used for this study. In dichloromethane, a strong dependence on the countercation was also seen, with the K(a)'s for the interaction with chloride ranging from 10(2)-10(4) M(-1). In the case of TPA, TBA, and TBP, the ITC data could not be fit to a 1:1 binding profile.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712-0165, USA. sessler@mail.uexas.edu
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
authors.forename: Dustin E
authors.initials: DE
authors.lastname: Gross
authors.forename: Won-Seob
authors.initials: WS
authors.lastname: Cho
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Lynch
authors.forename: Franz P
authors.initials: FP
authors.lastname: Schmidtchen
authors.forename: Gareth W
authors.initials: GW
authors.lastname: Bates
authors.forename: Mark E
authors.initials: ME
authors.lastname: Light
authors.forename: Philip A
authors.initials: PA
authors.lastname: Gale
mesh_terms: D000838:Anions; D047250:Calixarenes / Q000737:chemistry* / Q000378:metabolism; D002151:Calorimetry; D002712:Chlorides / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D017186:Titrimetry
chemical_list: D000838:Anions; D002712:Chlorides; D011166:Porphyrins; D000644:Quaternary Ammonium Compounds; D012996:Solutions; C469811:calix(4)pyrrole; D047250:Calixarenes