Portal Effects on the Stability of Cucurbituril Complexes

This work is concerned with the properties of cucurbitn]uril (CBn) host portals. The carbonyl oxygens lining each of the cavity openings on these hosts give rise to a rim of negative charge density, which often has strong effects on guest binding processes. The negative effect that carboxylates exert on guest binding to cucurbit7]uril (CB7) is described in detail, as well as the fact that the protonation state of terminal ?COO^?/COOH groups can be utilized to control CB7 shuttling on suitably designed pseudorotaxanes. Carboxylates can also slow down the kinetics of CB7 complex formation and dissociation. Finally, the electrostatic properties of the portals are useful -with suitable molecular design- to develop strong cooperativity effects, resulting from attractive side-by-side interactions, on the assembly of multi-component supramolecular complexes.