| This thesis is concerned with the synthesis of novel corrole macrocycles and the applications of their metal complexes in mediating epoxidation reactions and hydrogen dismutation. Corrole is a porphyrin analogue capable of stabilizing high-valent metal ions. A series of cofacial biscorroles bearing various spacer groups have been synthesized. The dimanganese biscorroles were found to have a surprisingly high activity in catalyzing the dismutation of H2O 2 to give O2 and H2O, similar to the enzymatic reaction of catalase. An asymmetric Mn(III) Mn(V)-oxo transient intermediate was proposed to account for the elevated reactivity. A series of hetero binuclear biscorroles such as [Mn Al] and monomeric Mn(III) corroles equipped with an intramolecular proton donor were synthesized to show that the catalase-like reactivity may be associated with the presence of a Lewis acid and is consistent with a proton-assisted mechanism during the peroxide bond fission. Also synthesized was a series of sterically encumbered Mn-corroles in which both faces of the corrole ring are shielded to enhance the stability of the high-valent Mn(V)-oxo intermediate. Such Mn-corroles were capable of catalyzing epoxidation of olefins by an oxene-transfer reaction analogous to cytochrome P-450 chemistry. The shielding structure also provided a higher level of chemoselectivity in favor of the more exposed or less substituted double bond on the substrate. Furthermore, it was possible to isolate a relatively stable Mn(V)-oxo intermediate with a terphenyl-shielded corrole to permit resonance Raman study for the first time in solution at room temperature. The observed Mn(V)-O16 stretching frequency at 952cm-1 and that of Mn(V)-O 18 at 913 cm-1 could be interpreted in terms of a Mn(V)≡O triple bond. In another study, iron complexes of the sterically shielded corroles were prepared and the binding of such Fe-corroles to various ligands (such as chloride, nitrosyl and N-methylimidazole) were examined. Unfortunately, even with the sterically shielded structure in place, the iron corrole decomposed rapidly in the presence of PhIO or mCPBA oxidant, preventing further investigation of the high-valent intermediate. Finally, the reactivity of Mn-corrole imbedded in supermolecular hydrogel or organogel have been explored. The t-butyl hydroperoxide oxidation of various sulfides in the presence of the Mn-corrole in gel matrix was found to increase selectively the twice-oxidized sulfone at the expense of the less-oxidized sulfoxide, presumably due to diffusion phenomenon within the gel to alter the local concentration of reactants. Thus, the gel matrixes show promises to become a new platform for exploring biomimetic materials. |
