Redox-Switchable Calix[6]arene-Based Isomeric Rotaxanes

Area of Science:

• Supramolecular Chemistry
• Molecular Machines
• Nanotechnology

Background:

• Operating molecular machines require switchable systems with nonsymmetrical components for unidirectional motion.
• Calixarene macrocycles are effective hosts for designing oriented rotaxanes and pseudorotaxanes with controlled complexation direction.

Purpose of the Study:

• To synthesize and characterize novel two-station rotaxanes based on bipyridinium-ammonium axles.
• To investigate the influence of molecular architecture on the controlled shuttling motion within these rotaxanes.

Main Methods:

• Utilized a supramolecularly assisted strategy for synthesizing orientational isomers.
• Employed electrochemical reduction of the bipyridinium station to trigger macrocycle displacement.
• Characterized the synthesized rotaxane structures.

Main Results:

• Successfully synthesized and characterized a series of two-station rotaxanes.
• Identified the ammonium unit as a suitable secondary binding site for the calixarene host.
• Demonstrated that macrocycle shuttling is controllable via electrochemical stimuli.
• Showcased the influence of axle chain length and secondary station position on motion.

Conclusions:

• The synthesized bipyridinium-ammonium rotaxanes function as controllable molecular machines.
• The design strategy allows for precise control over the directionality and extent of molecular motion.
• This work advances the development of sophisticated molecular devices with tunable properties.