title: Substituent effects on xenon binding affinity and solution behavior of water-soluble cryptophanes.
abstract: A water-soluble triacetic acid cryptophane-A derivative (TAAC) was synthesized and determined by isothermal titration calorimetry and fluorescence quenching assay to have a xenon association constant of 33,000 M(-1) at 293 K, which is the largest value measured for any host molecule to date. Fluorescence lifetime measurements of TAAC in the presence of varying amounts of xenon indicated static quenching by the encapsulated xenon and the presence of a second non-xenon-binding conformer in solution. Acid-base titrations and aqueous NMR spectroscopy of TAAC and a previously synthesized tris(triazole propionic acid) cryptophane-A derivative (TTPC) showed how solvation of the carboxylate anions can affect the aqueous behavior of the large, nonpolar cryptophane. Specifically, whereas only the crown-crown conformer of TTPC was observed, a crown-saddle conformer of TAAC was also assigned in aqueous solution.
authors.affiliation: Department of Chemistry, Biotechnology Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: P Aru
authors.initials: PA
authors.lastname: Hill
authors.forename: Qian
authors.initials: Q
authors.lastname: Wei
authors.forename: Thomas
authors.initials: T
authors.lastname: Troxler
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Dmochowski
mesh_terms: D000085:Acetates / Q000138:chemical synthesis / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods; D002151:Calorimetry / Q000379:methods; D007700:Kinetics; D011083:Polycyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012996:Solutions; D014230:Triazoles / Q000138:chemical synthesis / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014978:Xenon / Q000737:chemistry*; D014979:Xenon Isotopes
chemical_list: D000085:Acetates; D011083:Polycyclic Compounds; D012996:Solutions; D014230:Triazoles; D014979:Xenon Isotopes; C545484:cryptophane A; D014867:Water; D014978:Xenon