An Ion-Pair Template for Rotaxane Formation and its Exploitation in an Orthogonal Interaction Anion-Switchable Molecular Shuttle

摘要

Despite significant advances in anion-template methods for the construction of mechanically interlocked molecules, the use of anions to induce changes in the relative positions of the components of catenanes and rotaxanes has proved particularly challenging, especially in comparison to the widespread success achieved with other stimuli. The few examples of anion-switchable molecular shuttles developed to date employ competition between the same types of weak interaction in both states of the molecule to achieve switching (solvation effects or the anion outcompeting hydrogen-bonding acceptor groups of the macrocycle for donor groups on the thread). Other features of anions, such as the propensity of halides to form strong coordination bonds to various transition metals, have yet to be exploited. Herein we report the serendipitous discovery of a new efficient template for rotaxane formation and its use in the assembly of a chloride-switchable molecular shuttle which exhibits excellent positional integrity (> 98 %) of the ring in both states that arises from orthogonal binding modes: direct intercomponent metal-ligand coordination in one state and a combination of tight ion pairing, aromatic stacking interactions, and CH—O and CH···Cl hydrogen bonding in the other.