Geometric and Electronic Structure Contributions to Bond-breaking and Bond-making Reactions of Mid-valent Manganese-Oxygen Complexes

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In many organisms, important chemical reactions, such as defense against toxic free radicals and the biosynthesis of DNA, are performed by enzymes that require the metal manganese. A thorough understanding of the functions of these enzymes requires knowledge of intermediates formed during the chemical reactions. At present, scientists have a limited understanding of how the enzyme creates an environment around the manganese center to control the reactivity of particular intermediates. In this project, Professor Timothy Jackson of the University of Kansas is using synthetic chemistry to make models of these enzyme intermediates, with the goal of understanding how particular variations to the manganese environment control chemical reactivity. The identification of principles of reactivity for these systems are required to allow scientists to both better understand the function of the manganese enzymes and to use these enzymes as inspiration to develop synthetic counterparts. Professor Jackson is also actively engaged in developing public poster projects for a General Chemistry course that serve a dual purpose of displaying student learning and increasing public scientific literacy. This project also offers unique, professional training activities by having graduate and undergraduate students participate in joint academic-industrial meetings and workshops.With funding from the Chemical Structure, Dynamics, and Mechanisms B program, Professor Timothy Jackson of the University of Kansas is elucidating foundational principles governing the bond-breaking and bond-making reactions of MnIII-hydroxo and MnIII-alkylperoxo complexes. These complexes mimic intermediates proposed in the mechanisms of various manganese-dependent enzymes, including manganese superoxide dismutase and manganese lipoxygenase. X-ray diffraction, X-ray absorption, electronic absorption, and magnetic circular dichroism methods are combined with electronic structure computations to define structural and electronic properties of MnIII-hydroxo and MnIII-alkylperoxo adducts and determine how the physical properties of these complexes are modulated by Lewis acids, hydrogen-bonds, and/ or variations in supporting ligands. The combined experimental and computational approach is employed to develop new structure-reactivity relationships for these manganese-oxygen intermediates of biological relevance. Professor Jackson is actively engaged in combining STEM education and outreach by increasing public scientific literacy through the incorporation of STEM outreach projects in a General Chemistry course, in support of the broader impacts of this project.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.