Accordion‐Like Motion in Electrochemically Switchable Crown Ether/Ammonium Oligorotaxanes

Play that squeezebox! Reversible switching of electrochemically controllable oligorotaxanes generates an accordion‐like molecular movement. Electrochemistry, EPR, and UV/Vis‐NIR studies reveal that this type of motion is induced by through‐space mixed‐valence, radical‐cation, and Coulombic interactions between tetrathiafulvalene‐decorated crown ether macrocycles.

Abstract

Reversible oxidation reactions in electrochemically switchable oligorotaxanes with tetrathiafulvalene (TTF) decorated 24‐crown‐8 ether wheels generate intramolecular mixed‐valence and radical‐cation interactions between the wheels. This induces shuttling of the wheels and a contraction of inter‐wheel distances. Further oxidation generates repulsive forces between the TTFs and maximizes the inter‐wheel distances instead. These interactions and co‐conformational changes were not observed for structurally similar controls in which acetyl groups along the axle prevent translational motion of the wheels. This operation mode of oligorotaxanes, which is reminiscent of an accordion‐like motion, is promising for functional materials and nanodevices such as piston‐type rotaxane motors.

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