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There’s a New Crown in Town: Synthesis and Characterization of a Uranyl Complex Supported by a Nitrated Crown Ligand
Khalife, Celine
Khalife, Celine
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Abstract
By studying the manner in which the uranyl ion interacts with various types of ligand systems, fundamental chemical insights can be obtained which could lead to innovation in the fields of radiochemical separations and nuclear fuel reprocessing. Such innovations could be developed into technologies for supporting a cleaner world and greener energy system. In this thesis, the synthesis and characterization of a novel aza-crown ligand and its uranyl-containing counterpart are outlined, along with electrochemical analysis and crystallography. The ligand is a member of a new class of aza-crown ligands for uranyl coordination that are being synthesized by the Blakemore Group at KU, and the derivative described in this thesis is unique as it is appended with nitro groups. The uranyl complex was prepared with straightforward synthesis procedures, and nuclear magnetic resonance (NMR) data provide evidence of the presence of multiple conformational isomers in solution. Among these isomers, there is a minor 3% component which could correspond to non-crown-encapsulated species. The metal-free ligand undergoes a quasi-reversible, two-electron reduction with a half-wave reduction potential of –1.56 V vs. the ferrocenium/ferrocene couple, corresponding to reduction of each nitro group. Scanning anodically reveals an amine-centered oxidation near +0.7 V and a paired follow-up reduction feature at –1.1 V. Both the nitro-centered reduction(s) and amine oxidation appear during electrochemical analysis of the uranyl complex, the data for which feature an additional chemically reversible U(VI/V) reduction at a rather positive half-wave potential of –390 mV. Considering all this, the uranyl complex described here appears to afford ready access to unique redox chemistry, including formation of U(V) species featuring ligand radicals derived from the nitro groups found on the ligand substituents. Built on the current foundation of results, future work is planned to chemically and electrochemically interrogate the properties of the radical species that can be generated on this new platform.
Description
This work was submitted in partial fulfillment of the requirements for the degree of Bachelor of Arts with Honors in Chemistry.
Date
2025-05
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University of Kansas, Department of Chemistry
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Available after June 30, 2027
Adobe PDF, 3.78 MB
- Embargoed until 2027-06-30
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Keywords
Inorganic Chemistry, Uranium, Nuclear Magnetic Resonance (NMR), Electrochemistry