CAS: CAREER: Synthetic Designs Toward Wavelength-Tunable Production of Reactive Intermediates for Selective Photooxidation

With support from the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Shabnam Hematian of the Department of Chemistry and Biochemistry at the University of North Carolina at Greensboro aims to develop a new class of photocatalysts to transform cheap and unreactive raw materials into value-added chemicals. These potential catalysts exploit the oxidizing power of oxygen in the air, as a green terminal oxidant, and the energy of light as a sustainable reagent for forming new and difficult-to-access chemical bonds. The goal of this research is to control the photochemical outcome and reaction selectivity through modulating the energy of the light source. Results from this project have the potential to enable faster and tunable reactions which are relevant in the synthesis of pharmaceuticals and other fine chemicals. This work provides a solid interdisciplinary training platform in the fields of photochemistry, synthesis, spectroscopy, redox, and kinetics for scientists at all levels. This group is also well-positioned to provide the highest level of education and training to engage students in science early in their careers (i.e., local high school and community college students as well as first-year undergraduate and graduate students), promoting recruitment and retention in the chemistry field. The discovery of effective homogeneous photocatalysts for the selective oxidation of substrates under mild conditions using dioxygen as the terminal oxidant remains an important objective in synthetic chemistry. The proposed work seeks to design and develop a new class of photocatalysts in which metal-dioxygen chemistry leads to the cooperative activation of dioxygen and formation of oxo-bridged heterobinuclear systems. In the developed systems, two different reactive high-valent metal-oxo intermediates are accessible through the photoactivation of two unique metal-oxo bonds which are driven from charge transfer excited states. In this project, the structure-function relationships of the developed oxo-bridged constructs will be investigated to understand how and to what extent electronic exchange coupling between the individual catalytic sites through an oxo bridging ligand in the ground state impacts the charge transfer transitions and how this coupling manifests itself in overall photoactivity. 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.