Metal-free redox active deep eutectic solvents.

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Deep eutectic solvents (DES) are tunable solvent systems with diverse applications.
• Viologen-based compounds are redox-active molecules with potential in electrochemical devices.
• Developing metal-free electrochemical systems is crucial for sustainability and specific applications.

Purpose of the Study:

• To investigate the electrochemical properties of metal-free deep eutectic solvents incorporating viologen-based ammonium salts.
• To determine the concentration limits and thermal properties of these novel DES.
• To understand the aggregation behavior of reduced viologen species in the solvent system.

Main Methods:

• Synthesis of deep eutectic solvents using hydrogen bond donors and viologen-based ammonium salts.
• Electrochemical characterization, including cyclic voltammetry.
• Spectroelectrochemistry to analyze redox species.
• Computational simulation of voltammetry to model electrochemical behavior.

Main Results:

• The developed DES exhibit reversible electrochemistry at high viologen concentrations (4.2 M).
• Freezing points of the solvents are near room temperature, facilitating handling.
• Spectroelectrochemistry and simulation data indicate minimal aggregation of the reduced viologen radical cation.

Conclusions:

• Metal-free DES with viologen salts offer a promising platform for electrochemical applications.
• The observed low aggregation of reduced viologen species is beneficial for electrochemical performance.
• These findings pave the way for the design of novel, sustainable electrochemical systems.