Date of Award:

2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Advisor/Chair:

Lisa M. Berreau

Abstract

The research presented in this dissertation has focused on studies of metal complexes which undergo oxidative aliphatic carbon-carbon bond cleavage using dioxygen as the oxidant. The goal of this research was to assess the reactivity and elucidate mechanistic details of the carbon-carbon bond cleavage reactions. The first part of this dissertation explores the light-induced dioxygenase reactivity of ruthenium flavonolato compounds. These compounds are of particular interest as they are currently being explored for their anti-cancer activity. The RuII(n6-p-cymene) flavonolato compounds studied were found to undergo photoinduced carbon-carbon bond cleavage albeit with low quantum efficiency. The cleaved products were found to be significantly less toxic than the starting material. The reactivity and loss of toxicity offers the possibility of light-induced deactivation of such compounds to limit overall toxicity. The remainder of the research presented in this dissertation is directed at understanding mechanistic features that govern the aliphatic carbon-carbon bond cleavage reactivity of mononuclear copper(II) chlorodiketonate complexes. Synthetic organic chemists have utilized molecular oxygen and copper catalysts for many organic transformations. However, few reports have appeared demonstrating aliphatic carbon-carbon bond cleavage mediated by copper and O2 and mechanistic details of these processes are limited. The previously reported complex [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 was found to undergo aliphatic carbon-carbon bond cleavage under ambient conditions in the presence of O2. Notably, a catalytic amount of chloride anion increases the rate of this reaction. In order to understand this enhanced reactivity, we have performed mechanistic experiments to probe this system. These include: (1) spectroscopic studies to probe anion binding to the copper center; (2) variable temperature kinetic studies to benchmark computational studies; and (3) evaluation of the impact of electron density within the chlorodiketonate substrate on the rate of the reaction. The nature of the anion in the [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 system was found to play a significant role in terms of the energy barriers associated with O2 activation and O-O bond cleavage. The electronic nature of the chlorodiketonate was found to affect the kinetics for the C-C bond cleavage reaction suggesting a change in mechanism for O2 activation depending on the substituent present.

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Available for download on Monday, December 06, 2021

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