In the last few decades, two new designer solvents have appeared: ionic liquids and deep eutectic solvents. While ionic liquids (IL) are molten salts at room temperatures, deep eutectic solvents (DES) are based on the well-known eutectic phenomenon. ILs and DESs have been presented as the next generation of solvents since they have many potential applications in chemistry and other areas of science and engineering. ILs and DESs share many interesting properties such as low vapour pressure and high conductivity. However, the solvation properties of these two solvents appear to be significantly different. So far, the characterization of the molecular interactions observed by solutes in either solvent has been done independently. Thus, the result are hard to compare because the molecular components of the two solvents did not share the same chemical structure. Here, we present a study of the solvation dynamics of two probes (one ionic and one molecular) in an IL and a DES sharing the same molecular structure, albeit the logical difference of ionic charge and anions needed to maintain charge neutrality. For this purpose, we used steady-state as well as non-linear ultrafast infrared spectroscopies to study solute-solvent interactions in the two solvents. Our experimental results revealed the presence of two distinct dynamics on the picosecond time scale irrespective of the solvent for the solvation shell motions around either solute. However, the time evolution of 2DIR spectra exposed a significant time evolution of the transition central frequency for the ionic solute which was only observed in DES. The results were interpreted in terms of the presence of two different local molecular environment in the DES which are not observed in the IL. Finally, the modelling of the IR lineshapes showed that the DES have a more disorganized molecular structure than the IL.

Solvation dynamics of an ionic and a molecular probe in an ionic liquid and an deep eutectic solvent with similar structure

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.