Portal Effects on the Stability of Cucurbituril Complexes

This work is concerned with the properties of cucurbit[n]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 cucurbit[7]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

Dendrimers as Guests in Molecular Recognition Phenomena

Dendrimers are highly branched macromolecules which may engage in host-guest interactions, acting as either hosts or guests; this review is specifically concerned with the binding behavior of dendrimers containing single or multiple guest residues interacting with individual, freely diffusing hosts

Cucurbit[7]uril: A Very Effective Host for Viologens and Their Cation Radicals

The host cucurbit[7]uril (CB7) forms very stable inclusion complexes with simple 4,4‘-bipyridinium (viologen) dication guests in aqueous solution. The binding constants were measured by electronic absorption spectroscopy and found to be as high as 1 × 105 L/mol. One-electron reduction of the viologen guest results in a modest 2-fold decrease of the binding constant. The rate of the heterogeneous electron-transfer reaction between the complexed viologen dication and cation radical remained fast in the voltammetric time scale