Kinetics and thermodynamics of hexameric capsule formation.
Resorcinarene 1b forms a hexameric assembly in water-saturated CDCl(3) that encapsulates one tetraalkylammonium salt (2(+)Br(-)). The remaining space is occupied by coencapsulated solvent molecules. A maximum of three and minimum of one CHCl(3) molecule were found inside of capsules with tetrapropyl- and tetraheptylammonium bromide, respectively. The encapsulation of the salt is endothermic and entropically favored by the liberation of the solvent molecules. The stabilities of the encapsulation complexes and the rates of guest exchange decrease for larger cations. The higher activation barriers for in/out exchange of the larger guests suggest tight conformational restraints in the transition state. It is likely that complete dissociation of one resorcinarene molecule is necessary for the exchange of the alkylammonium salts.
The Skaggs Institute for Chemical Biology and Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Masamichi
M
Yamanaka
Alexander
A
Shivanyuk
Julius
J
Rebek
D047250:Calixarenes; D002725:Chloroform / Q000737:chemistry; D018360:Crystallography, X-Ray; D007700:Kinetics; D015394:Molecular Structure; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013816:Thermodynamics
D000644:Quaternary Ammonium Compounds; C466160:resorcinarene; D047250:Calixarenes; C055292:tetrahexylammonium; D010649:Phenylalanine; D002725:Chloroform