Inclusion complexes of coumarin in cucurbiturils.

Coumarin was found to form stable inclusion complexes with cucurbiturils. In the presence of cucurbit[7]uril (CB[7]), 1 : 1 inclusion complexes were observed in aqueous solution, as monitored by (1)H NMR and UV-visible absorption spectroscopies, and further supported by ab initio calculations, whereas with cucurbit[8]uril (CB[8]) a solid phase 1 : 2 host : guest complex was found in a single crystal X-ray diffraction structure determination.

Probing cucurbituril assemblies in water with TEMPO-like nitroxides: a trinitroxide supraradical with spin-spin interactions.

Nitroxide free radicals are demonstrated to be useful guests for probing cucurbit[n]uril (CB[n]) assemblies in water by EPR spectroscopy. CB[7] and CB[8] significantly aggregate either in solution or in the solid state (as evidenced by a single-crystal X-ray structure in which CB[8] forms supramolecular triangles with 4-methoxy-TEMPO). The included nitroxides show a striking resistance to biologically relevant reduction, benefiting from the carcerand effect of CB[7] and CB[8] solutions.