Reactivity of high-valent metal-oxo corroles and corrolazines as solvated molecules and nanoparticles

This thesis will describe the synthesis and reactivity of high-valent metal-oxo corroles and corrolazines. Corrolazines and corroles are trianionic porphyrinoid ligands that allow for the stabilization of high-valent metal ions and, thus, provide platforms to study the reactivity of species with metals in higher oxidation states. The study of high-valent metal species is significant because understanding the reactivity of these high-valent metal species is critical to understanding the factors that influence the mechanism of metalloenzymes and synthetic catalysts, which utilize high-valent metal species as the reactive intermediate. The relevance of such species will be described in the first chapter of this thesis.;One high-valent metal-oxo complex that is commonly invoked as the reactive intermediate in heme enzymes is the FeIV(O) π-cation radical porphyrin complex known as compound I (Cpd-I). However, this iron-oxo complex is difficult to generate and study due to its inherent stability. Chapter 2 will describe the generation, characterization, and reactivity of a high-valent iron-oxo corrolazine Cpd-I analog, (TBP8Cz+·)Fe IV(O) (TBP8Cz = octakis-tert-butylphenyl corrolazine). The structural characterization of this high-valent iron-oxo complex represents the first structural information available for a mononuclear well-defined high-valent iron-oxo corrole or corrolazine. This Cpd-I analog was competent towards C-H bond activation and reacted with a variety of organic substrates. The mechanism proposed for this reactivity involves an initial hydrogen atom abstraction from the organic substrate, similar to the mechanism proposed for Cpd-I. The reactivity of (TBP8Cz+·)Fe IV(O) was found to be lower compared to porphyrin Cpd-I analogues but may provide insight to the factors that influence this difference in reactivity.;Modified porphyrins, known as porphyrinoids, containing metal ions have also shown great potential for applications as catalysts, photo-active devices, and medicinal agents. For many of these applications, there is a strict requirement that these metalloporphyrinoids are water-soluble, which often poses a synthetic challenge. Chapter 3 will describe the development of a protocol that can "solubilize" hydrophobic corrolazines as nanoparticles in an aqueous environment with good control of particle size. This process circumvents the need for synthetic modification of the ligand. The catalytic reactivity of iron corrolazine nanoparticles is also described including the use of hydrogen peroxide as an external oxidant with the aid of an axial donor, which could not be used for molecular iron corrolazine. The use of hydrogen peroxide as an oxidant for catalysis is desirable because it is a clean and inexpensive reagent. Therefore, this new catalytic activity with hydrogen peroxide is significant result.;Chapter 4 examines the mechanism for O-O bond formation facilitated by a (CPDCPC)MnV(O) (CPDCPC = 10-(4-cyanopheny1)-5,15-(2,6-dichlorophenyl)corrole). This high-valent manganese-oxo corrole was characterized by UV-vis, EPR, and LDI MS. Evidence was obtained for the nucleophillic attack of hydroxide on (CPDCPC)MnV(O) to form a MnIV(O2) corrole complex. In addition, an alkyl peroxide is proposed to be synthesized by O-O bond formation between an alkoxide and (CPDCPC)MnV(O). The O-O bond formation mechanism is important because it is a vital step for the splitting of water in photosynthesis as well as in solar fuel devices.;The final chapter, chapter 5, discusses some preliminary work that investigates the effect of axial ligands and one-electron oxidation of the ligand on the reactivity of high-valent manganese-oxo corroles. The identity of the axial ligands has been found to influence the reactivity of heme active sites in metalloenzymes. In one theory, the axial ligand can affect the basicity of the metal-oxo complex, which is directly related to the reactivity of the metal-oxo complex. This chapter presents the enhanced reactivity of (CPDCPC)Mn V(O) and (CPDCPC)MnIV(OH) by the addition of cyanide as an axial donor. This result supports the theory that an increase in basicity of the MnV(O) or MnIV(OH) species results in an increase in the reactivity. A small part of this chapter also provides evidence for the rare generation of a MnV(O) π-cation radical corrole. The difference in reactivity between this species and a Mn V(O) species towards oxygen atom transfer to a substrate may support the theory that oxygen atom transfer reactions are influenced by the electrophilicity of the manganese-oxo complex.