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Date of Award
Spring 2025
Document Type
Masters Thesis
Department or Program Affiliation
Department of Chemistry
Degree Name
Master of Science (MS)
Department
Chemistry
First Advisor
Gilbertson, John D.
Second Advisor
Vyvyan, James R.
Third Advisor
Kowalczyk, Tim
Abstract
Inorganic fertilizers have been able to support the growing global population, but in turn have also disrupted the global nitrogen cycle by introducing an excess of nitrogen species. About 50% of the world population depends on nitrogen-based fertilizers for nourishment. However, fertilizer pollution has been reported to have detrimental effects on terrestrial and aquatic life. The excess nitrogen species entering ecosystems via runoffs or leaching lead to soil acidification, eutrophication, and a decrease in biodiversity. About 80% of anthropogenic emissions of N2O are caused by agricultural production. N2O is a potent greenhouse gas (GHG) that has 265 times the 100-year global warming potential than CO2. Through the nitrogen cycle, nature reduces nitrogen species to less toxic forms, allowing them to be consumed by plant-based lifeforms. Biological denitrification is supported by metalloenzymes like the reductases of nitrate, nitrite, and nitric oxide reductases. Research into the reduction of NO to form N2O is essential to address the disruption of the global nitrogen cycle. This thesis describes ligands designed to mimic the secondary coordination sphere of metalloenzymes like flavodiiron nitric oxide reductases (FNOR) to tune reactivity while maintaining redox capabilities of the metal center, iron (II). The active site of FNOR is of particular interest as it has hydrogen bonding capabilities within its secondary coordination sphere that has been shown to reduce the activation barrier in N2O formation from NO. To further investigate the role of hydrogen bonding on N-N bond formation, a series of hydrogen bond donating pyridinediimine (PDI) ligands were developed. [Fe(PhNHPDI)(NO)2]+ (3+) was reported to form N2O from the reduction of the dinitrosyl iron complex (DNIC). The control complex which is the exact replica of (3+) but with the exception of the NH group replaced with a methyl group was compared. A series of ligands was investigated to further understand the role hydrogen bonding has in the formation of N2O. These ligands vary in bulkiness, and a ditopic hydrogen bond donating ligand was also examined. Finally, to probe the mechanism in N2O formation, mechanistic studies were completed and analyzed.
Type
Text
Publisher
Western Washington University
OCLC Number
1523074394
Subject – LCSH
Ligands--Design; Metalloenzymes; Nitrogen cycle; Denitrification; Hydrogen bonding; Nitrogen fertilizers
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Recommended Citation
Fugami, Kayla M., "Bioinspired Ligand Design with Hydrogen Bonding Capabilities Facilitate Denitrification and N-N Bond Formation" (2025). WWU Graduate School Collection. 1386.
https://cedar.wwu.edu/wwuet/1386