RUI: Condensed-Phase Effects on the Structural and Energetic Properties of Nitrogen Donor - SOx Complexes

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In this project funded by the Chemical Structure, Dynamics and Mechanisms-A program of the Chemistry Division, Professor James Phillips and his undergraduate researchers at the University of Wisconsin-Eau Claire will study how the structures of certain stable molecules change as a result of their associations with each other. Molecular structure is typically unaffected by chemical environment; distances between atoms typically do not change when a substance condenses or goes into solution. However, certain “molecular complexes” - associations of two or more otherwise stable molecules - can undergo major changes of this ilk, but the overall generality of such effects is not well-established. This project will characterize a series of complexes apt to change structure in inert, non-interacting “solvent” environments known as “cryogenic matrices” (solid samples of argon, neon, or nitrogen, frozen at temperatures near absolute zero). The complexes will be studied by probing their resonant frequencies (how fast or easily their chemical bonds vibrate), which shift systematically when structural changes occur. In addition, the systems will be explored by computer simulations of the bonding to address the underlying factors that drive the unusual structural changes. The knowledge gained from these studies will contribute to a fundamental understanding of the nature of chemical bonding, which in turn can help other researchers to better understand and predict chemical reactivity in the research lab, industrial settings, and the environment. The project will take place at an accessible, public comprehensive university (UW-Eau Claire), and will provide transformative research, mentoring, and career development experiences for undergraduate students. This combined quantum-chemical and experimental (matrix-IR and UV spectroscopic) investigation will target three types of systems: i) H3N–SO2 and its methylated analogs, ii) Pyridine - SO2, and its fluoropyridine analogs, and, iii) the analogous SO3 complexes. The central hypothesis is that bonds about the central S-atom in SOx will manifest repulsive forces that impede further coordination, and lead to extreme structural changes in inert media. Confirmation of this will manifest a refined understanding of factors affecting coordinate bond strength, which may impact many areas of chemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.