Publication Date

Summer 2018

Advisor(s) - Committee Chair

Dr. Rui Zhang, Dr. Stuart Burris (Director), Dr. Eric Conte, Dr. Darwin Dahl, and Dr. Lawrence Hill

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

In enzymatic and synthetic catalytic oxidations, high-valent iron-oxo intermediates play a vital role as the active oxidant. In this regard, many synthetic metal catalysts are designed as biomimetic models to resemble the active site of Cytochrome P450 enzymes (P450) which are the predominant oxidation catalysts in nature. Vitamin B12 cofactors, with a corrole-like structure corrin, are also utilized in some of the more difficult reactions in nature such as rearrangement and reductase reactions.

In this work, application of the promising photochemical method to corrolecontaining ligands systems showed much success in the generation of manganese(V)-oxo corrole intermediates using two electron-deficient corrole ligands 5,10,15-tris-(4- trifluoromethylphenyl) corrole (4-CF3)TPC and 5,10,15-tris-(4-nitrophenyl) corrole (4- NO2)TPC. Homolytic cleavage of the O-N or O-ClO2 bond led to generation of the detectable manganese(V)-oxo corroles which were found to act as a competent oxotransfer agent in the presence of various organic reductants. The reaction was marked by the return to a low-valent manganese(III) corrole through a direct oxygen atom transfer (OAT) pathway or formation of manganese(VI)-oxo corrole and manganese(IV) product through a disproportionation pathway. The photo-generated manganese(V)-oxo corrole intermediates were tested as the oxidizing agent for substrate oxidation reactions.

More importantly, accomplished within this work is the synthesis for a novel porphyrin complex with light-harvesting functionalities. The light harvesting porphyrin complex (L-Por) exhibits remarkable spectral absorption properties within the range of 400-550 nm allowing for the efficient harvesting of a broad spectrum of light. It is expected that the attached antennae chromophores and metalloporphyrin core will absorb visible light and, at the same time, the antennae could transfer energy to the metalloporphyrin core. Ruthenium(II)(L-Por)(CO) was found to efficiently photo-eject the carbonyl ligand when subjected to visible light. Generation of ruthenium(VI)(LPor)( O)2 was achieved through application of sacrificial oxidant iodobenzene diacetate (PhI(OAc)2). Stoichiometric oxidation of ruthenium(VI)(L-Por)(O)2 formed ruthenium(IV)(L-Por)(O) and cis-cyclooctene oxide with observed rate constants that were 10-fold greater under visible light irradiation. Future investigations will employ a bis-porphyrin-diruthenium(IV)-μ-oxo dimeric complex as a potential catalyst in photocatalytic aerobic oxidation reactions.

Disciplines

Inorganic Chemistry | Medicinal-Pharmaceutical Chemistry | Organic Chemicals | Organic Chemistry

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