Redox switchable daisy chain rotaxanes driven by radical-radical interactions.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Electrochemistry

Background:

• Development of mechanically interlocked molecules (MIMs) for molecular machinery.
• Need for molecular switches with distinct mechanical responses.
• Limitations of existing bistable catenanes and rotaxanes.

Purpose of the Study:

• To synthesize and characterize electrochemically bistable 'daisy chain' rotaxane switches.
• To elucidate the electrochemical switching mechanism.
• To investigate the relationship between mechanical movement and changes in molecular dimensions.

Main Methods:

• One-pot synthesis utilizing click chemistry to assemble rotaxane precursors.
• Characterization by high-field (1)H NMR spectroscopy.
• Electrochemical analysis using cyclic voltammetry and spectroelectrochemistry.

Main Results:

• Isolation of six distinct daisy chain species (monomers, dimers, trimers) with cyclic and acyclic isomers.
• Detailed structural and dynamic characterization of the synthesized rotaxanes.
• Elucidation of an electrochemical switching mechanism involving radical cation interactions.

Conclusions:

• Novel daisy chain rotaxanes demonstrate electrochemically controlled bistability.
• Switching induces significant and distinct changes in molecular dimensions (constriction/dilation or contraction/expansion).
• These molecules represent promising electrochemically addressable molecular switches with unique mechanical actuation.