A Perylene-Bridged Switchable [3]Rotaxane Molecular Shuttle with a Fluorescence Output.

A bistable bis-branched [3]rotaxane with a perylene bisimide (PBI) chromophore that separates two mechanically interlocked [2]rotaxane arms including a diferrocene- functionalized dibenzo-24-crown-8 ring, was designed, prepared, and characterized by ¹H NMR and ¹³C NMR spectroscopy and HR-ESI mass spectrometry. The uniform relative shuttling movement of target [3]rotaxane in response to external acid-base stimuli was confirmed by ¹H NMR spectroscopy. Furthermore, the shuttling motion of the macrocycles in the system was accompanied by a remarkably visual fluorescence change due to the distance-dependent photoinduced electron transfer process from the ferrocene units to the PBI fluorophore. This kind of rotaxane has important potential for designing more sophisticated mechanically interlocked molecules with controllable functions. [ABSTRACT FROM AUTHOR]