Compared to a linear 1D coordination polymer of cucurbit [5] uril with Dy 3+ ion, a pair of homochiral 1D-helical coordination polymers of cucurbit[5] uril with Dy 3+ were obtained by spontaneous resolution upon crystallization in the presence of achiral hydroquinone, suggesting hydroquinone acts as an inducer of chiral helix.

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The host-guest interaction between symmetrical a,a9,d,d9-tetramethyl-cucurbit [6]uril (TMeQ[6]) and methylviologen (N,N9-dimethyl-4,49-bipyridinium, MV) dication was investigated both in aqueous solution and in the solid state using NMR spectroscopic methods and single-crystal X-ray diffraction analysis. In the aqueous solution, TMeQ[6] forms a 1 : 1 inclusion complex with methylviologen MV 2+ , and the chemical exchange of the MV 2+ guest in and out of the cavity of the TMeQ[6] host was fast on the NMR time scale. In the solid state, however, the MV 2+ guest was partially encapsulated into the TMeQ[6] host. We found that the chemical environment of the TMeQ[6] host underwent a severe change during the encapsulation process. Interestingly, electrochemical studies revealed that, unlike other cucurbiturils, TMeQ[6] has the same level of binding affinity to the charged forms (MV 2+ and MV + ? ) and the fully reduced form (MV 0 ). These studies contribute to the fundamental understanding of the interdependence of electron-transfer processes and molecular recognition.

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Eight coordination complexes, {LnCl 2 (H 2 O) 3 Q*[5]}?NO 3 ?18.5H 2 O [isomorphous for Ln = La (1), Ce (2) and Pr[isomorphous for Ln = Ho (7) and Er (8)], were obtained by reactions of the corresponding lanthanide species with the macrocyclic ligand pentacyclohexanocucurbit[5]uril (Q*[5]) in aqueous solution, and their structures were determined by single-crystal X-ray diffraction. Crystal structure analysis reveals that, in complexes 1-5, each Q*[5] coordinates to one lanthanide(III) ion to form an opened molecular capsule structure, and then adjacent molecular capsules bridge each other to form a 1-D coordination polymer structure, while in complexes 6-8, each Q*[5] coordinates to two lanthanide(III) ions to form a 0-D half-opened molecular capsule structure. These complexes show that their structural variations are ascribed to the effect of lanthanide contraction.