Combining NMR and Computational Chemistry to Study Complex Systems

In this video, Damodaran Krishnan Achary, research professor and director of the Nuclear Magnetic Resonance (NMR) Facility at the University of Pittsburgh, discusses how experimental NMR and computational chemistry complement each other in the study of complex chemical systems, including ionic liquids and reaction mechanisms. Achary emphasizes that combining these approaches allows researchers to interpret experimental data more fully and to explore molecular behavior that is difficult to observe directly.

He explains that his interest in computational chemistry began during his PhD and quickly proved invaluable for interpreting solid-state NMR data. For example, chemical shift and quadrupolar coupling data from materials could not always be assigned to specific crystal structures using experimental techniques alone. By calculating NMR parameters theoretically, his group was able to identify trends and match experimental data to structural features, enabling confident material assignments.

This integration is particularly powerful in studying ionic liquids used for carbon capture. Achary describes work on imidazolium acetate-based ionic liquids, where NMR revealed the formation of multiple chemisorbed and physisorbed CO₂ species. Computational chemistry allowed his team to model the reaction mechanisms, predict the most favorable pathways, and provide a mechanistic understanding that complements the NMR observations.

Achary also highlights a collaboration where molecular dynamics simulations predicted how adding water would affect ionic liquid dynamics. Simulations suggested that small amounts of water would slow ion motion by forming a hydrogen-bonded network, while higher water content would disrupt the network, increasing dynamics. Experimental NMR measurements of diffusion coefficients confirmed this trend, demonstrating how computation and spectroscopy together can provide a detailed, quantitative picture of molecular behavior.

Through these examples, Achary illustrates the synergistic relationship between experimental NMR and computational chemistry. By combining theoretical modeling with high-resolution spectroscopic measurements, researchers can not only characterize molecular structure and dynamics but also probe reaction mechanisms and complex interactions that would otherwise remain inaccessible, advancing both fundamental understanding and practical applications in materials and chemical sciences.