CAS: Interrogating the Intersection of Structure, Bonding, and Reactivity of Hypervalent Halogens

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With the support of the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) Program in the Division of Chemistry, Professors David Stuart and Theresa McCormick of Portland State University are studying the intersection of chemical structure, bonding models and chemical reactivity of hypervalent organohalogens. Synthetic molecules enhance daily life through new medicine, agricultural advances, and cutting-edge technologies. Organohalogens are a class of compound that may facilitate the synthesis of these molecules by acting as catalysts or reagents that introduce key structural components. In some cases, it is probable that organohalogens may replace expensive and rare metals that are commonly used in synthesis. To fully realize the potential of hypervalent organohalogens in synthesis, a deeper understanding of fundamental bonding events is needed. This will be achieved through a combined experimental and theoretical approach applied in this work. Training of the next generation of scientists will occur with this award by including graduate and undergraduate students in research. Portland State University is recognized as a “First-gen Forward” Institution, which enables inclusion of first-generation college students in research experiences. Finally, during this award period the principal investigators will increase access to laboratory research for blind high school students through a day camp at PSU.Non-covalent bonding interactions are a cornerstone of the reactivity of hypervalent organohalogens, yet the underlying atomic-level properties that dictate their strength are not well understood. With this award, the principal investigators tackle non-covalent interactions of hypervalent halogens from multiple perspectives. Both theoretical and empirical approaches are employed to gain new insight into halogen bonding and the bifunctional character of diaryliodonium salts. They will use a combination of physical organic chemistry techniques (conductance, NMR titration, kinetics) and theory (DFT and NBO) to correlate bonding models with structure and thermodynamic/kinetic reactivity. They will specifically focus on three key areas: 1) the orbital interaction of halogen atoms in halogen-bond donors, 2) bifunctional character of diarylhalonium salts when participating in non-covalent interactions, and 3) reactions of diarylhaloniums with pronucleophiles based on bifunctional activation. These activities, when completed, would contribute to advances in new synthetic methods and catalysis for organic synthesis.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.