This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Mahdi Abu-Omar at Purdue University to investigate metal mediated hydrogen atom transfer (HAT) and to study the reactions involved with chlorite dismutase. The objectives of the HAT chemistry are to: (1) study the kinetics and mechanism(s) of hydrogen atom transfer (HAT) in a series of tosylimido complexes of corrole (Mn, Cr, and V) and their oxo analogs, and (2) expand the utility of HAT with these novel imido complexes to achieve catalytic amination of C-H bonds. A second project is concerned with the reaction chemistry (dismutation/destruction) of the chlorite ion (ClO2 -), which is formed by perchlorate respiring bacteria. The mechanism of chlorite dismutation in the enzyme chlorite dismuatse (Cld) will be studied and compared with water soluble prophyrinoid models.
Understanding reaction rates and mechanisms of metal mediated HAT reactions relates to harnessing these reactions for benign functionalization of C-H bonds. The study of chlorite dismutation in enzyme and models has ramifications for the chemistry of chloride oxyanions in the environment. Postdoctoral, graduate, and undergraduate researchers will learn to make molecules, measure kinetics, perform state-of-the art spectroscopic experiments, and analyze data to gain molecular (mechanistic) insight, and present their research findings.
Perchlorate is a recognized contaminant that has been found in soil and ground water. Microbes isolated from contaminated sites utilize two enzymes to remediate perchlorate by transforming it to chloride (salt) and oxygen gas. The first enzyme, which contains molybdenum, reduces perchlorate to chlorite. The second key enzyme in this process is chlorite dismutase, which takes chlorite to innocuous chloride and oxygen gas. This enzymes contains iron in its active site and the iron is required for the formation of oxygen. We studied chlorite dismutase and defined the molecular chemical steps that enable its function. The chlorite molecule binds iron, which in turn breaks a chlorine oxygen bond to make a new oxidized iron species and a chlorine product that is held in close proximity to the oxidized iron. Further reaction between this chlorine species and the oxidized iron gives oxygen gas and chloride. Based on this understanding, we designed and made iron compounds that are capable of transforming chlorite to harmless chloride and oxygen gas. Our research has also lead to the discovery of manganese compounds that are capable of transforming chlorite to chlorine dioxide in water under mild conditions at room temperature. Chlorine dioxide is an important disinfectant used in water purification. However, it is not stable for prolonged times and it is very difficult to transport. Hence its preparation on-demand is very important. Our process for chlorine dioxide production employs an environmentally friendly metal, manganese, uses water as a solvent, and does not require corrosive acid.
