Supramolecular Self-Assembly of Cucurbit[6]uil and Ionic Liquid in Non-aqueous System.

A novel [2]pseudorotaxane of cucurbit[6]uril(CB[6]) and 1-butyl-3-methyl-imidazolium bromide ([C₄mim]Br) was synthesized by directly mixing the host and the guest molecules in non-aqueous system. Structural characterizations of the [2]pseudorotaxane were carried out by 1D, 2D NMR and X-ray crystallography techniques both in solution and in crystal structure. The crystal structure demonstrated that CB[6] and [C₄mim]Br formed a complex with the ratio 1:1, in which one guest [C₄mim]Br was included inside the CB[6], while two other [C₄mim]Br molecules were free and surrounded the [2]pseudorotaxane as solvent molecules, which could stabilize the crystal structure through hydrogen bonds. Moreover, parallel solvent channels consisting by free [C₄mim]Br molecules occupied the pores among the frame of the pseudorotaxanes and formed zigzag lines in the crystal structure. [C₄mim]Br can serve as not only the guest reactant but also the solvent in the formation of [2]pseudorotaxane formation. [ABSTRACT FROM AUTHOR]