Probing solvent fluctuations in deep eutectic solvents: Influence of probe charge and nano-domain localization

Area of Science:

• Physical Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Deep eutectic solvents (DESs) are complex mixtures with distinct nano-domains.
• Understanding molecular heterogeneity in DESs is crucial for their application.
• Hydrogen bond donor (HBD) and acceptor rich domains influence DES properties.

Purpose of the Study:

• Investigate solvation structure and dynamics in choline chloride-based DESs.
• Determine the effect of probe charge on DES structure and dynamics.
• Elucidate the role of nano-domain heterogeneity in DES solvation.

Main Methods:

• Utilized two-dimensional nuclear magnetic resonance (2D NMR) and two-dimensional infrared (2D IR) spectroscopies.
• Employed molecular dynamics (MD) simulations for complementary analysis.
• Introduced neutral (methyl thiocyanate) and anionic (ammonium thiocyanate) vibrational probes.

Main Results:

• Small probes did not alter the overall DES structure, irrespective of their charge.
• Solvation dynamics were found to be dependent on long-range electrostatic ordering within the DES.
• Local shielding effects within specific nano-domains significantly influenced probe solvation dynamics.

Conclusions:

• DES nano-domain heterogeneity plays a critical role in solvation dynamics.
• Experimental and simulation methods provide a comprehensive understanding of DES behavior.
• DES solvation is governed by both bulk electrostatic properties and local nano-domain environments.