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

Abstract

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 1 H NMR and 13 C 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 1 H 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.

A Focus on Triazolium as a Multipurpose Molecular Station for pH‐Sensitive Interlocked Crown‐Ether‐Based Molecular Machines

“…in 2015. The symmetrical bi‐stable bis‐branched [3]rotaxane molecular machine contains a perylene bisimide (PBI) chromophore at the middle of the threaded axle and ferrocenyl units on the DB24C8 . The molecular machinery is once again based on DB24C8 derivative and ammonium/triazolium molecular stations, so that two distinct co‐conformational states can be easily reached upon variation of pH (Scheme ).…”

Switched “On” Transient Fluorescence Output from a Pulsed-Fuel Molecular Ratchet

“…A key concept underpinning the new system (Figure B) is that the fluorescence of a pyrene residue on the tape should only be “switched on” when a threaded directionally transported crown ether binds to the N -methyltriazolium group adjacent to the fluorophore. Otherwise the pyrene fluorescence is quenched − by photoinduced electron transfer (PET). To explore the feasibility of such a signaling process, we designed a model with a single digit (“1”) encoded in the molecular tape, as shown in Figures B and .…”

“…The final feature of the design is fluorescence readout of the crown ether position provided by incorporating a pyrene residue within the thread (Figure ). The pyrene fluorescence is quenched by PET to the adjacent N -methyltriazolium group. − However, when the crown ether binds to the N -methyltriazolium site, the PET is disrupted, and under UV-irradiation centered around 343 nm, the pyrene fluoresces. In this way, the intensity of any fluorescence output can be linked to the position of the macrocycle on the molecular thread.…”

Aqueous assembly of a (pseudo)rotaxane with a donor–π–acceptor axis formed by a Knoevenagel condensation

“…Depending on the particular implementation, fluorescence enhancement, electron and/or energy transfer mechanisms can be incorporated in optical triggered molecular switches, typically as a function of the proximity of the components involved. [1][2][3][4] Commonly employed dyes include rylene diimides, [5][6][7] naphthalene imides, 8 azo dyes, [9][10][11] squaraines, 12,13 and poly-aromatic hydrocarbons like anthracene 14,15 or pyrene. 16 Despite the growing library of rotaxanes, only very few examples comprising linear donor-πacceptor "push-pull" chromophores are reported.…”