Reactivity of Copper-Dioxygen Intermediates in Biomimetic Model Chemistry

Abstract

Copper-activated dioxygen species have been well known as key intermediates in the metalloenzymes and industrial catalysts. In synthetic chemistry, reactivity study of copper-reactive oxygen adducts was investigated to understand the enzymatic processes. However, the examination of reactivity is still limited to certain intermediates such as copper-superoxo species. The diverse type of reactivity of copper-reactive oxygen species needs to be studied extensively. Especially, the copper(II)-hydroperoxo and -alkylperoxo complexes have conducted only electrophilic reactivity through the O-O bond cleavage, so far. In this dissertation, the nucleophilic reactivity of copper(II)-activated dioxygen intermediates has been focused. In chapter 1, the nucleophilic reactivity of a copper(II)-hydroperoxo complex has been observed. The copper(II)-hydroperoxo species shows highly oxidative reactivity in aldehyde deformylation. In chapter 2, the temperature dependence of the reactivity of copper(II)-alkylperoxo complexes in aldehyde deformylation and catalytic C-H bond activation has been investigated. In chapter 3, the ligand-based alkylperoxide binding copper complex was studied. Interestingly, depending on the Lewis acidity of redox-inactive metal ions, the nucleophilic reactivity of a copper(II)-ligand-based alkylperoxo complex was enhanced and modulated. All of the copper(II)-reactive dioxygen species have been characterized with various physicochemical methods such as ultraviolet-visible (UV-vis) spectroscopy, cold-spray ionization mass spectrometry (CSI-MS), resonance Raman (rRaman) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The nucleophilic character of copper(II)-hydroperoxo and -alkylperoxo complexes was determined by the positive Hammett ρ values.