Identifying intermolecular multiple-quantum coherences in ionic liquids

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Ionic liquids, such as 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), are isotropic systems often exhibiting high spin concentrations.
• High spin concentrations can facilitate the emergence of intermolecular multiple quantum coherences (iMQCs).

Purpose of the Study:

• To investigate the presence and characteristics of intermolecular multiple quantum coherences (iMQCs) in the ¹H, ¹⁹F, and ¹¹B nuclei of [bmim][BF4].
• To explore the potential excitation of intramolecular triple quantum coherences (TQCs) in the ¹¹B quadrupolar nuclei due to slow tumbling in ionic liquids.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study the ¹H, ¹⁹F, and ¹¹B nuclei within the ionic liquid [bmim][BF4].
• Experiments were designed to detect both homonuclear iMQCs and intramolecular TQCs.

Main Results:

• Homonuclear intermolecular multiple quantum coherences (iMQCs) were successfully identified for ¹H, ¹⁹F, and ¹¹B nuclei.
• While iMQCs were observable for ¹¹B, intramolecular triple quantum coherences (TQCs) were not detected, even considering the slow tumbling dynamics characteristic of ionic liquids.

Conclusions:

• The study confirms the occurrence of iMQCs in ionic liquids across different nuclei.
• The absence of detectable intramolecular TQCs provides insights into the specific dynamic processes and interactions within ionic liquids.