Complementary interpretation of E_T(30) polarity parameters of ionic liquids

Area of Science:

• Physical Chemistry
• Materials Science
• Solvent Science

Background:

• Ionic liquids (ILs) are versatile solvents with tunable properties.
• Reichardt's ET(30) is a key polarity scale for ILs.
• Understanding IL polarity requires correlation with other solvent parameters.

Purpose of the Study:

• To investigate the relationship between Reichardt's ET(30) and Kamlet-Taft (α, β, π*) and Catalán (SA, SB, SP, SdP) parameters for ionic liquids.
• To determine the influence of anion structure on ET(30) values.
• To independently measure π* and α/SA parameters for protic ionic liquids.

Main Methods:

• Multiple square correlation analyses were employed.
• Reichardt's pyridinio phenolate betaine dyes were used to assess ET(30).
• Specific probes (Th, DENA, Fe complex) were utilized for Kamlet-Taft parameter determination.

Main Results:

• Correlations between ET(30) and Kamlet-Taft (α, π*) and Catalán (SA, SdP) parameters were established.
• The influence of halide anions on ET(30) was investigated.
• Linear correlations between Catalán's SdP and IL molar concentration were observed.

Conclusions:

• Reichardt's ET(30) parameter is effectively correlated with established solvent polarity scales for ionic liquids.
• Anion structure plays a role in the ET(30) polarity of ionic liquids.
• The findings provide a deeper understanding of ionic liquid solvation properties.