Unveiling molecular interactions in glycerol-based deep eutectic solvents

Author(s)

Souza, Leticia A. ; de Moraes, Beatriz R. ; de Souza, Rafael M. ; Porto, Gabriel A. L. ; van den Bruinhorst, Adriaan ; Costa Gomes, Margarida ; Ribeiro, Mauro C. C. ; Ando, Romulo A.

• Document type: Journal article
• Source: Physical Chemistry Chemical Physics; v. N/A, p. 9-pg., 2025-04-09.

Abstract

Elucidating the liquid structure of deep eutectic solvents (DES) is crucial to understand how local interactions determine their properties. In this work, the impact of the anion on the liquid structure and local interactions was investigated for mixtures of tetrabutylammonium chloride and bromide ([N4444]Cl and [N4444]Br) with glycerol (Gly). The phase behavior was explored across various compositions using differential scanning calorimetry (DSC) showing that these mixtures form a (meta)stable liquid at room temperature and xsalt = 0.25. At this composition, infrared spectroscopy (IR) revealed strong hydrogen bonding between glycerol and the anion that is more pronounced for chloride than bromide. This finding is supported by the enthalpy of mixing measurements and by quantum chemical calculations. Molecular dynamics (MD) simulations demonstrated that intermolecular hydrogen bonds between glycerol molecules persist, maintaining a long-range liquid structure even in the presence of salt. Far-infrared spectroscopy (FIR) combined with MD simulations revealed changes in local intermolecular dynamics due to a confinement effect caused by the strong anion-glycerol interactions. These results highlight the critical influence of local interactions driven by the anion on DES properties. (AU)

• FAPESP's process: 20/12054-1 - Vibrational spectroscopy and properties of deep eutectic solvents
• Grantee: Letícia Almeida Souza
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 22/11983-4 - Spectroscopy signal enhancement: nanomaterials, theory, and computer simulation
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 22/01493-0 - Physical and thermodynamic properties of deep eutectic solvents
• Grantee: Letícia Almeida Souza
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• FAPESP's process: 20/06766-9 - Molecular dynamics of deep eutectic solvents
• Grantee: Rafael Maglia de Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 20/09250-3 - Hydrogen Bonding in Ionic Liquids - Vibrational Spectroscopy and Physical Properties
• Grantee: Beatriz Rocha de Moraes
• Support Opportunities: Scholarships in Brazil - Doctorate