Intermolecular hydrogen bonds in water@IL supramolecular complexes.

Area of Science:

• Supramolecular Chemistry
• Ionic Liquids
• Physical Chemistry

Background:

• Ionic liquids (ILs) are versatile solvents with tunable properties.
• The influence of trace water on IL structure and reactivity is not fully understood.
• Understanding water-IL interactions is crucial for designing advanced chemical processes.

Purpose of the Study:

• To investigate the role of small water amounts in specific ionic liquids.
• To elucidate the structural and dynamic effects of water incorporation.
• To determine the impact of water-IL complexes on H/D exchange reactions.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy, including Nuclear Overhauser Effect (NOE).
• Density Functional Theory (DFT) calculations.
• Analysis of hydrogen bonding and supramolecular complex formation.

Main Results:

• NMR and DFT confirm water molecules are trapped within the IL network, forming guest@host supramolecular structures.
• Strong hydrogen bonds between water and IL anions stabilize these complexes.
• The H2O@IL complex formation facilitates selective H/D exchange at specific positions (imidazolium C2-Me and ketone Cα).

Conclusions:

• Water plays a critical role in structuring ionic liquids at the molecular level.
• The observed guest@host complexes are key to understanding selective H/D exchange mechanisms.
• These findings offer insights into controlling reactivity in ionic liquid systems.