NMR Approaches to Understanding Ionic Liquid Behavior

In this video, Damodaran Krishnan Achary, research professor and director of the NMR Facility at the University of Pittsburgh, discusses how advanced NMR spectroscopy provides unique insights into the structure and dynamics of ionic liquids, highlighting capabilities that other analytical techniques cannot match. Since joining Pitt in 2005, Achary has developed a highly interdisciplinary NMR facility, supporting research across chemistry, biology, materials science, pharmacy, and engineering, while also building an independent research program focused on leveraging NMR to address complex molecular questions.

Ionic liquids, which remain liquid at room temperature, present challenges for traditional structural characterization. Techniques such as infrared spectroscopy can identify functional groups, and X-ray crystallography requires crystals, which these salts cannot form. According to Achary, NMR is uniquely suited for elucidating the full molecular structure of ionic liquids, providing detailed information about both cation and anion environments. Beyond static structure, NMR can probe dynamic processes that are inaccessible to most other methods. For example, through diffusion measurements and NOE experiments, researchers can study cation–anion interactions, measure ion mobility, and quantify “ionicity”—the degree to which ions exist freely versus forming ion pairs. By combining diffusion coefficients with the Nernst–Einstein equation, NMR-derived theoretical conductivities can be compared with experimental impedance measurements, revealing critical dynamic behaviors such as ion pairing.

Achary also notes the relevance of these insights to applied research, particularly in carbon capture, where understanding the interaction of CO₂ with ionic liquids requires a detailed picture of both structure and dynamics. NMR’s ability to simultaneously capture static and dynamic properties makes it an indispensable tool for studying these systems, offering a depth of understanding that complements and extends beyond other analytical methods.

Through his research and facility leadership, Achary continues to demonstrate the power of NMR spectroscopy not only as a tool for chemical structure elucidation but also as a window into molecular interactions and dynamics that are essential for the development of next-generation materials and technologies.