SusChEM: Electronic Structure and Reactivity of Peroxo- and Hydroxomanganese Compounds

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Timothy Jackson of the Department of Chemistry at the University of Kansas is investigating new manganese peroxo and hydroxo complexes with interesting chemical reactivity. The goal of this research is to determine how the structures of these manganese complexes can be controlled to impart a desired reaction. This knowledge could be used to reduce the cost and environmental footprint of chemical transformations and will advance understanding of manganese enzymes in humans, plants, and bacteria. The project lies at the interface of inorganic, physical and biological chemistry, and provides a training experience for graduate and undergraduate students. Trips to national laboratories to perform X-ray absorption experiments afford training in synchrotron radiation, including radiation safety training. This research is disseminated to the general public via presentations at University Orientation Days, the University Mini-College, and Science on Tap. In these forums, a broad, general audience engages with on-going chemical research. Spectroscopic and theoretical methods used in this research is incorporated into graduate and undergraduate courses. This research has relevance to sustainable chemistry because it uses less toxic and more abundant manganese complexes. Manganese(III)-peroxo adducts are frequently proposed as intermediates in the formation of high-valent manganese-oxo species in synthetic oxidation catalysts. Manganese(III)-hydroxo motifs are known to participate in biologically important proton-coupled electron-transfer reactions. However, the influence of geometric and electronic structure on the reactivity of these compounds is not well defined. Specific aims of the project include: 1) investigation of the O-O bond activation pathways of a manganese(III)-peroxo adduct support by an oxidatively robust ligand; 2) exploration of ligand effects on the reductive activation of manganese(III)-peroxo adducts; and 3) a systematic variation of the ligand field of manganese(III)-hydroxo complexes to develop correlations between electronic structure perturbations and chemical reactivity. Through this work, molecular-level insight into the activation of peroxomanganese(III) species for oxygen (O)-O bond cleavage through chemical and electrochemical pathways are developed. In addition, the proton-coupled electron transfer reactions of mid-valent hydroxomanganese(III) species are explored. In an undergraduate bioinorganic course, students will develop video modules describing relevant physical methods. The methods used in this research are incorporated into graduate and undergraduate courses. The results of this work are disseminated broadly through University and community outreach activities.