Hydrogen-Bonded Complexes in Binary Mixture of Imidazolium-Based Ionic Liquids with Organic Solvents

• Published in: The journal of physical chemistry. B 2023-10, Vol.127 (41), p.8916-8925
• Main Authors: Rush, Kaiyah, Islam, Md Muhaiminul, Nawagamuwage, Sithara U., Marzette, Jorden, Browne, Olivia, Foy, Kayla, Reyes, Khale’, Hoang, Melissa, Nguyen, Catherine, Walker, Alexis, Ferrufino Amador, Susana, Riglioni, Emanuela, Rubtsov, Igor V., Riley, Kevin, Dutta, Samrat
• Format: Article
• Language: English
• Subjects: B: Liquids; Chemical and Dynamical Processes in Solution
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.3c05152

Though local structures in ionic liquids are dominated by strong Coulomb forces, directional hydrogen bonds can also influence the physicochemical properties of imidazolium-based ionic liquids. In particular, the C-2 position of the imidazolium cation is acidic and can bind with suitable hydrogen bond acceptor sites of molecular solvents dissolved in imidazolium-based ionic liquids. In this report, we identify hydrogen-bonded microenvironments of the model ionic liquid, 1-ethyl-3-methylimidazolium tris­(pentafluoroethyl) trifluorophosphate, and the changes that occur when molecular solvents are dissolved in it by using a C–D infrared reporter at the C-2 position of the cation. Our linear and nonlinear infrared experiments, along with computational studies, indicate that the molecular solvent dimethyl sulfoxide can form strong hydrogen-bonded dimers with the cation of the ionic liquid at the C-2 position. In contrast, acetone, which is also a hydrogen bond acceptor similar to dimethyl sulfoxide, does not show evidence of cation–solvent hydrogen-bonded conformers at the C-2 position. The outcome of our study on a broad scale strengthens the importance of cation–solute interactions in ionic liquids.