Solvatocromic behavior of polarity indicators in PILs and their mixtures with molecular solvents. Autoprotolysis and its relation to acidity

ADAM CLAUDIA G; GAMBA LUCIA; BRAVO, M. VIRGINIA

Chem. Proc.

BASEL SWITSERLAND

Año: 2022 vol. 8 p. 92 - 97

2504-3900

It is interesting to know the behavior of Protic Ionic Liquids (PILs) within the binary mixture of molecular solvents, since it is usual to carry out processes such as organic and inorganicsynthesis, or liquid–liquid extractions in the presence of another solvent. Moreover, on certainoccasions, the absence of water is strictly required. In this sense, it is important to note that theaddition of small amounts of IL to the molecular solvent allows a fine adjustment in its microscopicproperties, obtaining “new solvent systems” with particular properties. The solvatochromic dyesare traditionally used as microscopic descriptors to determine the molecular microscopic propertiesof solvents, so we aim to re-evaluate the behavior of these probes and reconsider the validity oftraditional polarity scales such as ET(30) in alkylammonium-based PILs, as well as in their mixtureswith molecular solvents, knowing that the real composition of these PILs depends on the equilibriumof autoprotolysis. The characterization of systems was completed in terms of a change in the ∆pKa ofthe precursor species of a PIL. A thermal analysis was also employed to determine the acid strength’srole in an ion’s complete formation in pure PILs.