Proton Transfer Equilibrium in Pseudoprotic Ionic Liquids: Inferences on Ionic Populations.

Area of Science:

• Chemistry
• Materials Science

Background:

• Nonstoichiometric pseudoprotic ionic liquids (NPPILs) are a novel class of ionic liquids with unique properties.
• Fundamental understanding of proton transfer equilibria in NPPILs is limited, hindering their technological application.

Purpose of the Study:

• To quantitatively characterize proton transfer equilibria and ion concentrations in NPPILs.
• To investigate the influence of mixture composition on proton transfer.

Main Methods:

• Utilized a combination of nuclear magnetic resonance (NMR) spectroscopy (¹H and ¹³C), infrared (IR) spectroscopy, and small-angle X-ray scattering (SAXS).
• Developed a model based on NMR data to calculate concentrations of all ionic species.
• Validated model predictions using complementary physical measurements.

Main Results:

• Proton transfer equilibria were characterized across varying compositions of trihexylamine/butyric acid and water/butyric acid mixtures.
• The developed model provided the first quantitative calculation of ionic concentrations in a NPPIL.
• Spectroscopic and modeling results demonstrated strong agreement, supporting the model's accuracy.

Conclusions:

• This work provides crucial quantitative data on ionic concentrations in NPPILs.
• The findings advance the fundamental understanding of proton transfer mechanisms in these emerging materials.
• This study lays the groundwork for the rational design and application of NPPILs.