An NMR study of the rates of single-molecule exchange in a cylindrical host capsule.
Self-assembled cylindrical capsule 1 is reversibly formed from dimerization of two tetraimide resorcinarenes. Studies of guest exchange involving host capsule 1 reveal a mechanistic continuum for exchange that depends on the structure of the guest. Kinetic and dynamic NMR measurements demonstrate the direct displacement of one guest by another. Surprisingly, in the case of benzene exchange in the pairwise encapsulation of benzene and p-xylene, the incoming benzene occupies the same half of the capsule as the outgoing benzene. As the size of the guests increases, solvent-bridged intermediates determine the rates; empty volumes on the molecular scale need not be invoked.
The Skaggs Institute for Chemical Biology and Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Stephen L
SL
Craig
Shirley
S
Lin
Jian
J
Chen
Julius
J
Rebek
D001554:Benzene / Q000737:chemistry*; D007700:Kinetics; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D011108:Polymers / Q000737:chemistry*; D014992:Xylenes / Q000737:chemistry*
D046911:Macromolecular Substances; D011108:Polymers; D014992:Xylenes; D001554:Benzene