Hydrogen-Bonding Interactions in Pyridinium-Based Ionic Liquids and Dimethyl Sulfoxide Binary Systems: A Combined...

Area of Science:

• Physical Chemistry
• Materials Science
• Spectroscopy

Background:

• Ionic liquids (ILs) are tunable solvents with applications in catalysis and electrochemistry.
• Addition of cosolvents like dimethyl sulfoxide (DMSO) can reduce IL viscosity and enhance mass transfer.
• Understanding IL-cosolvent interactions is crucial for optimizing their performance.

Purpose of the Study:

• To investigate the molecular interactions between N-butylpyridinium dicyanamide ([Bpy][DCA]) ionic liquid and DMSO.
• To elucidate the structural changes and hydrogen bonding dynamics in [Bpy][DCA]-DMSO mixtures.
• To correlate spectroscopic and computational findings with solution properties.

Main Methods:

• Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR).
• Hydrogen nuclear magnetic resonance (1H NMR) spectroscopy.
• Density functional theory (DFT) calculations.

Main Results:

• Dilution of [Bpy][DCA] with DMSO leads to the formation of ion pairs from ion clusters.
• DMSO forms hydrogen bonds with both [Bpy]+ cations and [DCA]- anions, with stronger interactions with cations.
• Hydrogen bonding interactions are maximized at a DMSO molar fraction of 0.4-0.5.
• Spectroscopic shifts indicate significant interactions, with anisotropy explaining DMSO upfield shifts.

Conclusions:

• The study reveals detailed molecular interactions between [Bpy][DCA] and DMSO.
• Hydrogen bonding plays a key role in modifying the structure and properties of the ionic liquid mixtures.
• DFT calculations provide insights into structural evolution and NMR spectral interpretations.