[摘要]：reviewed, and their application to the study of salt bridges is introduced. Carboxylate/ammonium ion pairs are generated within an environment that more or less surrounds the functional groups within a synthetic fixed introverted solvent sphere. This is provided by cavitands that fold around amines and present them with a carboxylic acid function. Both org. and water-sol. versions were prepd., and their equil. affinities with quinuclidine bases were detd. by NMR methods. The assocn. consts. range from approx. 103 M-1 in water to more than 105 M-1 in org. solvents. Studies of nitrogen inversion and tumbling of [2.2.2]-diazabicyclooctane within the introverted acids also illustrate the strength of the acid-base interactions. The barriers to in-out exchange of several amine guests were detd. to be in the range from 15 to 24 kcal mol-1. Some parallels with enzymes are drawn: the receptor folds around the guest species, presents them with inwardly directed functionality, and provides a generally hydrophobic environment and a periphery of secondary amide bonds.
