Identifying Different Halogen-/Hydrogen-Bonding Interaction Modes in Binary Systems that Contain an Acetate Ionic...

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Noncovalent interactions between ionic liquids (ILs) and halogenated molecules are crucial for fundamental science and drug discovery.
• Understanding these interactions aids in designing novel materials and pharmaceuticals.

Purpose of the Study:

• To investigate the noncovalent interactions between 1-butyl-3-methyl-imidazolium acetate and three halobenzenes (C6F5X, where X=I, Br, H).
• To differentiate various interaction modes using spectroscopic and computational methods.
• To identify the types of complexes formed in these systems.

Main Methods:

• Excess Infrared (IR) spectroscopy to analyze spectral changes.
• Density Functional Theory (DFT) calculations to model interactions and complexes.
• Comparative analysis of interactions with C6F5I, C6F5Br, and C6F5H.

Main Results:

• The interaction strength followed the order: C6F5I > C6F5Br > C6F5H.
• Excess IR spectra showed distinct positive/negative peaks and multi/two-state phenomena, indicating varied interaction modes.
• Three distinct complexes (anion-C6F5I, anion-2C6F5I, ion-pair-C6F5I) were identified in the IL-C6F5I system.
• Only ion-pair complexes and self-associates were observed for IL-C6F5Br and IL-C6F5H systems.

Conclusions:

• Iodine-based halogen bonding in the IL-C6F5I system is strong enough to disrupt IL cation-anion interactions.
• C6F5I exhibits unique complexation behavior compared to C6F5Br and C6F5H.
• C6F5I shows potential as a co-solvent for tuning the properties of acetate-based ionic liquids.