Influence of the Hammett Base Concentration on Acidity Levels in Ionic Liquids Using Raman Spectroscopy and Hammett Acidity Functions

Rensonnet, Aurélie; Eppe, Gauthier; Malherbe, Cédric

doi:10.1002/jrs.6807

Article (Scientific journals)

Influence of the Hammett Base Concentration on Acidity Levels in Ionic Liquids Using Raman Spectroscopy and Hammett Acidity Functions

Rensonnet, Aurélie; Eppe, Gauthier; Malherbe, Cédric

2025 • In Journal of Raman Spectroscopy

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https://hdl.handle.net/2268/331137

DOI
10.1002/jrs.6807

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Keywords :

Brønsted acidity; Hammett acidity functions; Hammett indicators; ionic liquids; Raman spectroscopy; Bistriflimide; Hammett acidity function; Hammett indicator; Nitroanilines; Property; Room temperature ionic liquids; Solvation properties; Specific solvation; UV-visible spectroscopy; Materials Science (all); Spectroscopy

Abstract :

[en] Room-temperature ionic liquids (RTILs) are a class of solvents with remarkable properties, including specific solvation properties and tuneable acidity levels. The Hammett acidity functions, commonly used to assess the acidity levels of ILs, rely on monitoring the protonation of colour indicators (especially nitroanilines) via UV-visible spectroscopy. However, this method possesses certain limitations, prompting our group to adapt it in Raman spectroscopy in a previous study. Yet the influence of the indicator concentration on the acidity functions has never been thoroughly examined. In this article, we investigated the effect of the 2,4-dichloro-6-nitroaniline concentration (from 7 to 50 mM) on the Hammett acidity functions estimated by Raman spectroscopy in 1-butyl-3-methylimidazolium bistriflimide, [BMIm]NTf2. The acidity measured with this method was higher than the acidity evaluated via UV-visible spectroscopy but lower than the acidity evaluated via Strehlow acidity functions, suggesting specific solvation effects of the nitroaniline in [BMIm]NTf2 and the formation of ion pairs in this solvent, which are discussed in this paper.

Disciplines :

Chemistry

Author, co-author :

Rensonnet, Aurélie ; Université de Liège - ULiège > Molecular Systems (MolSys)

Eppe, Gauthier ; Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de spectrométrie de masse (L.S.M.)

Malherbe, Cédric ; Université de Liège - ULiège > Département de chimie (sciences) > Chimie analytique inorganique

Language :

English

Title :

Influence of the Hammett Base Concentration on Acidity Levels in Ionic Liquids Using Raman Spectroscopy and Hammett Acidity Functions

Publication date :

31 March 2025

Journal title :

Journal of Raman Spectroscopy

ISSN :

0377-0486

eISSN :

1097-4555

Publisher :

John Wiley and Sons Ltd

Peer reviewed :

Peer Reviewed verified by ORBi

Funders :

F.R.S.-FNRS - Fonds de la Recherche Scientifique

Funding number :

FNRS-ASP55135

Funding text :

AR acknowledges the Fonds de la Recherche Scientifique (FNRS) for the financial support (Grant FNRS\u2010ASP55135).

Available on ORBi :

since 24 April 2025

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