The efficient utilization of O2 for oxidative chemical transformations remains an unmet challenge of the scientific community. O2 activating enzymes, however, have developed multiple strategies for controlling the reduction of O2 and harnessing its oxidative capabilities for oxidation reactions. These enzymes can serve as blueprint in the development of O2 activating catalysts for C-H bond oxidation reactions. We have developed a velvut vivum catalyst that mimics the O2 activation pathway of the nonheme iron 2-oxo-glutarate (a-KG) dependent oxygenase enzymes. Presented herein are mechanistic and spectroscopic studies of the model complex [FeII(N2O1)(a-KG)(L)] (N2O1 is 2-((2-(dimethylamino)ethyl)(methyl)amino)-acetate). Low-temperature stopped-flow UV/Vis spectroscopy was utilized to study the kinetics of the reaction of [FeII(N2O1)(a-KG)(L)] with O2 in methanol at -85 C and determine the activation energies associated with each step in the O2 activation process for comparison to computational studies. Magnetic circular dichroism (MCD) spectroscopy was used to probe the changes in ground and excited state energy levels of [FeII(N2O1)(L)3] as a result of binding a-KG or other a-keto acids. This study will allow for a better understanding of the role of a-keto acid binding in the O2 activation process and how the HOMO-LUMO energy gap of the a-keto acid might modulate the kinetics of the reaction with O2. A combination of continuous wave-electron paramagnetic resonance spectroscopy (cw-EPR) and electron spin echo envelope modulation (ESEEM) spectroscopy were utilized to determine the number of geometric isomers of [FeII(N2O1)(a-KG)(L)] in solution and the geometric configuration of the isomers detectable by EPR. These studies will ultimately be utilized to determine the isomer of [FeII(N2O1)(a-KG)(L)] that has the lowest kinetic barrier to the reaction with O2.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/42642 |
| Date | 26 May 2021 |
| Creators | Cunningham, Laura Anne |
| Contributors | Caradonna, John P. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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