The synthesis of a series of dumbbell-shaped compounds, which can act as a host (e.g., toward alkali metal cations) and as a guest (e.g., toward cyclobis(paraquat-p-phenylene)) in a supramolecular context is described. The self-assembly of pseudorotaxanes and rotaxanes, in which cyclobis(paraquat-p-phenylene) encircles polyether chains intercepted in their middles by a hydroquinone ring and terminated at each end by 12-crown-4, 15-crown-5, monoaza-18-crown-6, 18-crown-6, or adamantyl groups, is achieved using either threading, clipping, or slipping procedures. All the pseudorotaxanes and rotaxanes are characterized in solution by spectroscopic means and, in the case of two of the rotaxanes, by X-ray crystal structures in the solid state. In the presence of metal ions, pseudorotaxanes carrying 12-crown-4 or 15-crown-5 stoppers can be disassembled in solution. The research shows how one kind of complexation can affect another kind of complexation - manifesting itself in a physical change in the system and so acting as a prototype of a potential molecular device.
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