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Three Ps in a Pod: The Quantification of Lewis Acidity using Phosphine Oxides and the Synthesis and Immobilization of Molecular Uranyl Complexes bearing Polycyclic Aromatic Hydrocarbons onto Pyrolytic Graphite-based Electrodes
Cecilia Paranjothi
Cecilia Paranjothi
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Abstract
This thesis discusses two different research themes. Chapter 1 describes the quantification of Lewis acidity using different phosphine oxide probe molecules. Triethyl (E), trioctyl (O), and triphenyl (P) phosphine oxides were selected as probes to investigate trends in the Lewis acidity of a wide range of mono-, di-, and trivalent metal cations. 31P{1H} titration data collected in MeCN revealed that all three probes bind to Na+ and K+ with 1:1 stoichiometry, whereas they bind to Li+, Ba2+, Sr2+, and Ca2+ with greater than 1:1 stoichiometry, as shown by data fitting to the Hill-Langmuir equation. The titration data differ in dynamic range, with E and O displaying a significantly larger dynamic range than P. In all cases, Δδ′max values from full titrations with K+, Na+, Li+, Ba2+, Sr2+, and Ca2+ were linearly correlated with the pKa values of the corresponding [M(OH2)m]n+ which suggests that Lewis acidity in water has a corresponding relationship with effective Lewis acidity in MeCN measured by the three phosphine oxide probe molecules studied in the course of the work described here. Chapter 2 describes the synthesis, characterization and surface immobilization of molecular uranyl complexes bearing different polycyclic aromatic hydrocarbon (PAH) groups. The PAH groups chosen for this study were 1-naphthyl, 2-naphthyl, and 9-anthracenyl. The modular synthetic route used to incorporate the PAH groups afforded the desired uranyl complexes in pure form, as indicated by 1H NMR and elemental analysis. The structures of two of the complexes were confirmed by single-crystal X-ray diffraction analyses as well. Vibrational and electronic absorption spectroscopy were used to further interrogate the electronic and structural properties of the complexes. The surface immobilization of the uranyl complexes was demonstrated through both surface electrochemistry and X-ray photoelectron spectroscopy.
Description
This undergraduate thesis was submitted to the Department of Chemistry in Partial Fulfillment of the Requirements for the Degree of
Bachelor of Science with Honors.
Date
2025-05-22
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Department of Chemistry, University of Kansas
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Keywords
Inorganic Chemistry, Titrations, Uranium, Redox, Spectroscopy