Imidazolium-based ionic liquids are spatially heterogeneous green solvents that are entirely made of ions. Probing their complex microenvironment in the liquid phase is a challenge. To explore the solvent microenvironment, we developed techniques specifically to label the C-2 position of the imidazolium cation ring with a C-D infrared label. Our studies, using the C-D infrared label as a probe, show that hydrogen bonding is a dominant factor in influencing the C-D infrared lineshape in these complex solvents. More importantly, our two-dimensional infrared spectroscopy studies show direct experimental evidence of gas-cation interaction. Our recent temperature-dependent studies reveal the existence of a possible ordered state at a higher temperature for these liquids. In short, our research show several hidden aspects of ionic liquids which can enhance our understanding of these liquids and thus their application.

Revealing ionic liquid solvent microenvironment with C-D infrared labels

ACS Fall 2021

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