Crystal structure and thermodynamics of reversible molecular capsules

The reversible encapsulation of small molecules by two rigid hemispherical molecules is described. The "bowls" are linked by four charged hydrogen bonds. The complex is highly guest-selective. A crystal structure of one complex and a thermodynamic analysis of several complexes provide an unusually vivid description of the structure and dynamics of these complexes. The relevance of these complexes as transition state models for the formation of carceplexes is also presented.