A musclelike [2](2)rotaxane: synthesis, performance, and molecular dynamics simulations

Area of Science:

• Supramolecular Chemistry
• Molecular Machines
• Organic Synthesis

Background:

• Rotaxanes are mechanically interlocked molecules with potential applications in molecular devices.
• Designing bistable rotaxanes allows for controlled movement and mechanical changes.
• Ferrocene-based recognition sites offer tunable properties for molecular shuttles.

Purpose of the Study:

• To synthesize and characterize a novel bistable symmetric [2](2)rotaxane.
• To investigate the acid-base driven shuttling motion of the rotaxane.
• To compare the molecular length changes with biological systems.

Main Methods:

• Threading-followed-by-stoppering synthesis strategy.
• Characterization using NMR spectroscopy ((1)H, (13)C, 2D ROESY) and HR-ESI spectrometry.
• Molecular dynamics simulations in different protonation states.

Main Results:

• Successful synthesis and characterization of the symmetric [2](2)rotaxane.
• Demonstrated acid-base controllable shuttling motion of the central ferrocene unit.
• Observed a significant molecular length change of approximately 48%, exceeding that of human muscle.
• Correlated translational and rotational motions through dihedral angle analysis.

Conclusions:

• The novel rotaxane functions as a bistable molecular machine with stimuli-responsive behavior.
• The significant length change highlights its potential for nanoscale actuation.
• The study provides insights into the interplay of translational and rotational dynamics in rotaxanes.