Many heme and nonheme enzymes contain iron ligated in their respective active sites, which is key to the facilitation of vital biological transformations. Both enzymes are known to enact common pathways in the incorporation of dioxygen into various substrates. Common intermediates such as iron-oxo and iron-hydroxo species have been investigated using model complexes, as to allow the study of bond-forming and bond-breaking reactivity which occurs at the metal centers. This dissertation contains reactivity studies on a novel iron(III)-methoxo complex to better understand the mechanism of oxygen radical rebound in nonheme iron enzymes. An overview of key high-valent iron intermediates and complexes is featured in Chapter 1, as well as the introduction to the rebound mechanism.
In Chapter 2, the synthesis of the novel iron(III)-methoxo complex is discussed. The material culminated from the synthesis of a new organic ligand with structural modification to encourage mononuclearity. The ferric material forms from its ferrous precursor when open to atmospheric oxygen, and provides a platform from which an analog of rebound could be directly investigated.
Chapter 3 discusses the measure of reactivity of the iron(III)-methoxo complex with a stable carbon-based radical. The organic product was identified and quantified, while the one-electron reduced iron material was also observed and quantified. This observation of rebound in the iron(III)-methoxo system provided valuable information regarding oxygen rebound in a mononuclear nonheme iron complex.
Chapter 4 utilizes the iron(III)-methoxo material in reaction with several additional organic radicals, to investigate whether the observed rebound reactivity occurs in a concerted or stepwise fashion. Hammett and Marcus analysis was employed, indicating that the transformation was concerted, as would be expected of a rebound reaction.
Chapter 5 gives the synthesis of several other iron complexes, with the potential for further investigation of rebound reactivity with regards to chlorine and fluorine. Preliminary reactivity indicates some success, providing a possible avenue toward the study of halogen rebound
