Unveiling molecular interactions in glycerol-based deep eutectic solvents

Area of Science:

• Physical Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Deep eutectic solvents (DES) are tunable materials with unique properties.
• Understanding the liquid structure of DES is key to their application.
• The role of specific anions in DES structure and dynamics requires further investigation.

Purpose of the Study:

• To investigate the impact of anions (chloride vs. bromide) on the liquid structure and local interactions in DES.
• To explore the phase behavior and hydrogen bonding in tetrabutylammonium salt-glycerol mixtures.
• To elucidate the influence of anion-glycerol interactions on DES dynamics.

Main Methods:

• Differential scanning calorimetry (DSC) for phase behavior analysis.
• Infrared (IR) and Far-infrared (FIR) spectroscopy for probing hydrogen bonding and dynamics.
• Quantum chemical calculations and Molecular Dynamics (MD) simulations for structural and dynamic insights.

Main Results:

• Mixtures of tetrabutylammonium chloride/bromide with glycerol form stable liquids at room temperature and specific salt compositions (x_salt = 0.25).
• Stronger hydrogen bonding between glycerol and the anion was observed for chloride compared to bromide.
• MD simulations confirmed persistent glycerol-glycerol hydrogen bonds and revealed anion-induced changes in local dynamics due to confinement effects.

Conclusions:

• The anion plays a critical role in dictating the liquid structure and local interactions within DES.
• Anion-glycerol interactions significantly influence the solvent's properties and dynamics.
• This study provides fundamental insights into DES structure-property relationships, crucial for designing new materials.