Molecular Actuators in Action: Electron-Transfer-Induced Conformation Transformation in Cofacially Arrayed...

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Organic Electronics

Background:

• Molecular actuators are crucial for controlled motion in response to external stimuli.
• Cofacial polyfluorenes offer a model system for studying charge and energy transfer in stacked assemblies.

Purpose of the Study:

• To design and synthesize cofacially arrayed polyfluorenes with varied end-capping groups.
• To investigate the redox-controlled electromechanical actuation of these polyfluorene systems.
• To understand the conformational changes and driving forces behind the actuation.

Main Methods:

• Synthesis of cofacial polyfluorenes (MeFnHm) with diverse end-capping groups.
• Characterization using NMR and optical spectroscopies, X-ray crystallography, and DFT calculations.
• Electrochemical oxidation to induce and study actuation.

Main Results:

• Neutral polyfluorenes adopt an open conformation, influenced by their local environment.
• Electrochemical oxidation triggers a reversible transition to a closed, fully π-stacked conformation.
• This conformational change is driven by charge-resonance stabilization of the cationic charge.

Conclusions:

• Redox stimuli can reversibly control the conformation of cofacial polyfluorenes.
• These findings provide insights into designing wire-like cofacial systems for molecular actuation.
• The study advances the development of novel electromechanical actuators based on π-stacked organic materials.