title: Solvent-stabilized molecular capsules.
abstract: Pyrrogallolarenes 2 were prepared by acid-catalyzed condensation of pyrrogallol with aldehydes. Compound 2a crystallizes from a methanol solution of quinuclidine hydrochloride to give a dimeric molecular capsule surrounding one disordered quinuclidinium cation. The molecules of 2a are connected by direct hydrogen bonds and by bridging methanol and water molecules. The chloride anion is positioned outside the capsule and is hydrogen bonded to the hydroxy groups of 2a. The shortest distance between the cation and anion was found to be 6.7 A. Crystallization of 2b from aqueous acetonitrile resulted in a dimeric capsule linked by a polar belt of 16 hydrogen bonding water molecules. Four acetonitrile molecules occupy the cavity of this dimeric capsule and assume two binding sites that differ in hydrogen bonding and electronic environment. Compounds 2 also form hydrogen-bonded dimeric molecular capsules in alcohols and aqueous acetonitrile solutions. These assemblies readily encapsulate tetramethylammonium, tetramethylphosphonium, quinuclidinium, and tropylium cations to give complexes stable on the NMR time scale at 233 K.
authors.affiliation: The Skaggs Institute for Chemical Biology and The Department of Chemistry, The Scripps Research Institute, MB-26, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Shivanyuk
authors.forename: Jan C
authors.initials: JC
authors.lastname: Friese
authors.forename: Steve
authors.initials: S
authors.lastname: Döring
authors.forename: Julius
authors.initials: J
authors.lastname: Rebek
mesh_terms: D002214:Capsules; D004355:Drug Stability; D000431:Ethanol / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D012996:Solutions; D012997:Solvents; D014961:X-Ray Diffraction
chemical_list: D002214:Capsules; D012996:Solutions; D012997:Solvents; D000431:Ethanol