CAREER: Quantifying Nitrogen-Oxide (NO) Activation and Coordination Modes through Synthesis, Spectroscopy and Computations

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In this CAREER project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Sabine Chantal E. Stieber of the Department of Chemistry at the California State Polytechnic University, Pomona (Cal Poly Pomona) is studying small molecule reactions at metal centers. Reactions utilizing small, nitrogen containing molecules found in the atmosphere are of considerable interest as mimics for existing biological processes involved in agricultural nitrogen fixation (such as in legumes) or for reducing the health effects of automobile pollutants. Advancing the knowledge of metal-nitrogen oxide interactions may also offer insights towards the development of catalytic systems for converting nitrogen oxide pollutants into useful chemicals. This research is especially challenging as the nitrogen oxide species are often unstable and short-lived, and thus require the development of new characterizational tools at a national synchrotron facility. These new tools are coupled with computational efforts and the synthesis of air-and moisture-sensitive inorganic complexes. The project is designed to enable undergraduate researchers to conduct impactful research and gain experience with a range of techniques. The research is integrated with education through student-led research modules in computational chemistry and crystallography. The efforts broaden research opportunities for all students and enable the recruitment of a diverse STEM workforce.Current methods to characterize metal interactions with nitrogen oxide-containing species are insufficient to provide complete chemical characterization of bonding, oxidation states, and functionalization, all of which are necessary for developing synthetic systems for nitrogen functionalization. A key challenge of studying nitrogen oxide-containing species is isolating the unstable species and characterizing them. To overcome these stability issues, Professor Stieber uses spectroscopic techniques that stablish spectral fingerprints for metals bound to different coordination numbers, modes, and oxidation states of nitrogen oxide species. This project examines X-ray emission spectroscopy (XES) as an analytical technique for characterizing coordination modes and redox activities in coordination complexes. The current project utilizes synthetic, synchrotron and computational methods to study more complex and challenging systems.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.