A [2]pseudorotaxane-based molecular machine: Reversible formation of a molecular loop driven by electrochemical and photochemical stimuli

Picking up the thread: A large, reversible change in size as well as shape is observed in a [2]pseudorotaxane-based molecular machine composed of cucurbit[8]uril (CB[8]; bead) and a hexamethylene-bridged bisviologen (thread, see schematic representation) on application of external stimuli. The key feature of the machinelike behavior is the reversible formation of a molecular loop by intramolecular pairing of the terminal viologen radical cation units inside CB[8] upon electrochemical or photochemical reduction.