Publication Date

Spring 2021

Advisor(s) - Committee Chair

Dr. Rui Zhang (Director), Dr. Kevin Williams, and Dr. Lawrence Hill

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

note: Some notation in this abstract may not appear exactly as formatted in the thesis.

In this work, ruthenium, iron, and manganese light-harvesting metalloporphyrins have been successfully synthesized to serve as biomimetic models of the active site of Cytochrome P450 for the development of a green and efficient oxidation catalyst. The covalent introduction of light-harvesting boron-dipyrrin (BODIPY) fluorophores on the porphyrin macrocycle allows for the absorption of a broader range of visible light in addition to that captured by the porphyrin aromatic system alone. It is expected that this core-antenna system will increase the absorbed light energy and transfer it to the reaction center, and thereby increase the efficiency of the catalyst. Fluorescence spectrometry was used to identify the presence of energy transfer from the BODIPY units to the porphyrin core, in which the fluorescence spectrum of the BODIPY overlaps with the absorbance spectra of the porphyrin chromophore at the Q band region.

The manganese(IV)-oxo light-harvesting porphyrin was also formed by both photochemical and chemical oxidation of the manganese(III) precursors. A kinetic plot of the observed rate constants for the reaction of manganese(IV)-oxo light-harvesting porphyrin with varying concentrations of thioanisole shows a linear relationship where the slope gives the second-order rate constant kox (M-1 s -1) = 0.4158, which was contrary to what was expected given the greater range of light energy able to be utilized. Ruthenium, iron, and manganese light-harvesting porphyrins served as oxidation catalysts that underwent preliminary oxidation trials with both sulfide and alkene substrates. In the presence of visible light, the ruthenium BODIPY porphyrin displayed an enhanced catalytic activity for both the sulfoxidation and epoxidation with PhI(OAc)2 and 2,6-dichloropyridine Noxide as oxygen sources, respectively. The epoxidation and sulfoxidation reactions catalyzed by both iron and manganese, however, fell below expectations. Possible explanations for the lack of reactivity include stable μ-oxo dimer formation or photodegradation of the catalysts.

Disciplines

Chemistry | Inorganic Chemistry | Organic Chemistry

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