Functionalized [2]rotaxanes

Abstract

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 [2]pseudorotaxanes and [2]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 [2]pseudorotaxanes and [2]rotaxanes are characterized in solution by spectroscopic means and, in the case of two of the [2]rotaxanes, by X-ray crystal structures in the solid state. In the presence of metal ions, [2]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.