Polyethylene Glycol as String for the Simultaneous Complexation of α-Cyclodextrin and Cucurbit[6]uril

α-Cyclodextrin and cucurbit6]uril are macrocyclic ligands with nearly identical molecular properties. Both ligands possess nonpolar cavities with similar dimensions. They are able to include nonpolar molecules within their cavities. The main difference between both ligands is their solubility in water. An acceptable solubility for cucurbit6]uril is only given in the presence of acids or salts. Due to the similarity of both ligands, the formation of mixed polyrotaxanes seems to be possible. The synthesis of statistically threaded α-cyclodextrin and cucurbit6]uril on polyethylene glycol 2000 is verified using elemental analysis, ¹H-NMR spectroscopy and differential scanning calorimetry. Under the experimental conditions used the number of threaded α-cyclodextrin molecules is higher compared with cucurbit6]uril. However it is shown that the formation of mixed complexes is possible.