Activation of small oxygen containing molecules by bioinspired first row transition metal complexes
Gullett, Kelly Lorraine
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https://hdl.handle.net/2142/124482
Description
Title
Activation of small oxygen containing molecules by bioinspired first row transition metal complexes
Author(s)
Gullett, Kelly Lorraine
Issue Date
2024-02-02
Director of Research (if dissertation) or Advisor (if thesis)
Fout, Alison
Doctoral Committee Chair(s)
Fout, Alison
Committee Member(s)
Girolami , Gregory
Olshansky, Lisa
Mirica, Liviu
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Iron
bioinspired
oxyanion
Abstract
The deoxygenation of toxic and pervasive water contaminants, oxyanions, by environmentally benign first row transition metal catalysts is one of the overarching goals of the bioinorganic subgroup within the Fout research program. Our group has demonstrated that our pyrrole based tripodal ligand, when metalated with iron, is capable of the reduction of a plethora of oxyanions. This work builds on that foundation by further exploring the reduction of selenium and chromium containing oxyanions. Chapter 2 focuses on reliable quantification of the reduction of selenate, selenite, selenous acid and selenium dioxide. Previous work reported these reductions, however the presence of a side product in the quantification process hindered accurate calculation of reaction yield. Additionally, Chapter 2 focuses on the continued effort to achieve higher turnover numbers in the catalytic one pot reductions of selenate and selenite.
The exploration of seleniferous oxyanion reduction is continued in Chapter 3 through the use of modifications to the tripodal ligand framework and changes in the solvent system. Our research group has established a library of ligands that alter the electronic and steric profile of the framework, which in turn affects the redox potential of the Fe species when ligated. This work summarizes the effects of the ligand modifications on the yield of selenium oxyanion reduction. Additionally, this chapter describes the effect of including methanol in the reaction mixture. The formation of an FeII methoxide and its subsequent reactivity is reported.
The quantification of oxyanion deoxygenation in our group has relied on the use of external reductants to generate diamagnetic products which can then be analyzed by NMR spectroscopy. While very useful, these secondary reactions can introduce error and increase the atom economy of the system. Chapter 4 of this work develops a paramagnetic 1H NMR calibration curve to directly quantify the amount of FeIII oxo generated in the reduction of oxyanions without the use of external reductants. The calibration curve was then used to calculate reaction yields for the reduction of dichromate and selenate.
Lastly, Chapter 5 pivots away from Fe and oxyanion reductions to focus on the formation of a carbonic anhydrase model system. Carbonic anhydrase is an enzyme which utilizes Zn ligated with three histidine moieties and an aqua/hydroxide ligand to achieve the hydration of CO2 for the regulation of an organism’s internal pH. The tripodal pyrrole-based system models the histidine residues found in the active site, as well as the hydrogen bonding network afforded by water molecules in the native enzyme. This chapter reports the synthesis of a ZnII aqua and a transient ZnII hydroxide and their reactivity towards CO2.
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