Probing Molecular Interactions in Functionalized Asymmetric Quaternary Ammonium-Based Dicationic Ionic Liquids

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Dicationic ionic liquids (DILs) are advanced materials with tunable properties.
• Understanding cation-anion interactions is crucial for designing DILs with specific thermal and spectral characteristics.

Purpose of the Study:

• To investigate the electronic structure, binding energies, and spectral properties of functionalized asymmetric DILs.
• To correlate cation-anion binding strength with glass transition temperatures and vibrational spectra.
• To analyze the influence of substituents on DIL stability and electrostatic interactions.

Main Methods:

• Dispersion-corrected density functional theory (DFT) calculations.
• Analysis of vibrational spectra (SO2 and CF3 stretching frequencies).
• Quantum theory of atoms in molecules (QTAIM) for charge distribution and electrostatic potential analysis.

Main Results:

• Methoxyethoxyethyl-substituted cations showed stronger binding with the bis(trifluoromethanesulfonyl)imide (Tf2N-) anion.
• Glass transition temperatures correlated with cation-anion binding strength, influenced by electrostatics and hydrogen bonding.
• Specific frequency shifts in SO2 (red-shift) and CF3 (blue-shift) stretching vibrations were observed and rationalized by substituent effects and binding strength.

Conclusions:

• Substituent choice significantly impacts DIL properties, including cation-anion binding, thermal stability, and spectral signatures.
• DFT and QTAIM provide valuable insights into the structure-property relationships of functionalized DILs.
• The findings offer a basis for designing novel DILs with tailored functionalities for various applications.