Session 6

Revisiting the State of Water in [BMIM][BF4] Aqueous Solutions

Marco Paolantoni
on  Wed, 10:25 for  20min
Marco Paolantoni, Brenda Bracco, Barbara Rossi, Paola Sassi, Andrea Mele
1. Department of Chemistry, Biology and Biotechnology, University of Perugia,
Via Elce di Sotto 8, 06123 Perugia, Italy
2. Elettra Sincrotrone Trieste, S.S. 114 km 163.5, Basovizza, 34149 Trieste, Italy
3. Department of Chemistry, Materials and Chemical Engineering “G. Natta”,
Politecnico di Milano, 20133 Milano, Italy
marco.paolantoni@unipg.it

Abstract

Mixtures of water with ionic liquids (ILs) represent promising, tunable systems with potential applications in various areas, ranging from green chemistry to biocatalysis, biopreservation, and energy-related applications [1].

Achieving a molecular-level description of water is crucial for explaining chemical, physicochemical and solvation properties of IL/water systems. However, despite numerous investigations on this subject, a deep understanding of the state of water and its modification in the whole concentration range is still partial controversial and incomplete, even for the prototypical [BMIM][BF4]/water system. Moreover, similarly to other ILs, upon the addition of water, several macroscopic properties of these mixtures exhibit nonlinear trends, with maxima or minima in different hydration domains. As such, the system can be exploited to increase our knowledge on the link between macroscopic properties and microscopic (molecular-level) features.

Here, the hydration features of [BMIM][BF4]/water solutions were investigated across the entire concentration range, by analysing UV-Raman and ATR-FTIR spectra. In particular, inspired by the multivariate curve resolution (MCR) approach [2], a differential method was employed to isolate the so-called solute-correlated (SC) spectrum, which highlights the vibrational contributions of water molecules perturbed by the solute (hydration or interfacial water). We will present this method as a useful way to obtain reliable quantitative information about the hydration features of ILs aqueous mixtures, including hydration numbers and aggregation properties [3,4]. The results will be discussed in connection with molecular dynamics (MD) simulation findings [5] and related approaches.

The primary goal is to gain a consistent picture on the state of water within the [BMIM][BF4]/water system in the different concentration regimes. This information is crucial for achieving a full understanding of this prototypical mixture in relation to its mesoscopic and macroscopic properties.

References

[1] V.A. Azov, K.S. Egorova, M.M. Seitkalieva, A.S. Kashin, and V.P. Ananikov, Chem. Soc. Rev., 47, 1250 (2018).

[2] D. Ben-Amotz, J.Am. Chem. Soc., 141, 10565 (2019).

[3] F. Matroodi, C. Bottari, B. Rossi, A. Mannu, M. Paolantoni, A. Mele, J. Mol. Liq., 395 123881 (2024).

[4] C. Bottari, L. Almásy, B. Rossi, B. Bracco, M. Paolantoni, A. Mele, J. Phys. Chem. B, 126 4299 (2022).

[5] T.-M. Chang, S.E. Billeck, J. Phys. Chem. B, 125 1227 (2021).