Cerium Photocatalysis And Progress Toward The Isolation Of Tetravalent Lanthanide Complexes

Photoredox catalysis is an important methodology where light is used to accelerate chemical reactions by inducing single-electron redox events. This approach is useful for not only improved and greener synthetic procedures for known transformations, but also creating new methodologies that are not attainable using non-photochemical techniques. The use of earth-abundant and readily available lanthanide photocatalysts offers an opportunity to complement low abundance transition-metal photosensitizers in catalysis. In this dissertation, rational designs and strategic applications of cerium photoredox catalysis are described. The photophysical and photochemical properties of cerium photocatalysts are directly related to the ligand types and variations in steric encumbrance at cerium cations. Moreover, organic syntheses, such as photoinduced borylation and phenylation of aryl halides, are achieved by cerium photocatalysis at room temperature with broad substrate scope. Such simple and potent lanthanide photoredox catalysis is anticipated to find applications in organic synthesis, pharmaceutical development, and small molecule activation. The redox chemistry of rare earth elements has broad applications in synthetic chemistry, material chemistry, and separations. However, in terms of the +3/+4 redox chemistry of molecular lanthanide compounds, only the CeIII/IV redox properties have been extensively studied because the other molecular lanthanide(IV) complexes have not yet been isolated and characterized. In this dissertation, progress toward the isolation of lanthanide(IV) guanidinate complexes is demonstrated. The stabilization of cerium(IV) oxidation state by guanidinate ligand framework is investigated. Investigations of oxidation reactions of other lanthanide(III) guanidinate complexes are reported