Synthetic copper-dioxygen adducts reactivity studies

The study of appropriately designed synthetic model complexes has been proved being a useful tool helping understand fundamental aspects of enzyme chemistry. As is relevant to the research described in this dissertation, copper proteins together with their active site chemistry were reviewed. Synthetic copper complexes with differing ligand environments were also discussed, focusing on copper-oxygen binding structure and their evolution during further O 2 activation and reactivity toward substrates.;In Chapter 2, we describe the systematic investigation of a protonation promoted (hydro)peroxo O--O bond cleavage mediated by dinuclear copper(II) complexes. One equivalent of the corresponding acid as the leaving group was detected after addition of proton to the acylperoxo dicopper(II) comounds, which suggests a proton-induced heterolytic O--O bond cleavage with the yielding of high-valent oxo-dicopper(III) species. Although lack of direct observation, this high-valent species show a significant high reactivity toward several external substrates, and can undergo a disproportionation reaction with the release of dioxygen in the absence of substrates, which further prove the existence of such high-valent species after a proton-induced peroxo O--O bond cleavage. Different aspects involving the heterolytic O--O bond cleavage chemistry are discussed, showing that strong acidity, polar solvents and better leaving group ability favor the O--O bond cleavage. Possible mechanisms of proton-promoted substrate oxidation reactions were also proposed based on kinetic studies together with other experiment data.;In Chapter 3, different kinetic behaviors of side-on peroxo and bis-mu-oxo species toward a series of substrates were observed. A disproportionation mechanism was used to regulate the second-order kinetic behavior, including the generation of a high-valent [Cu2O2]3+ species served as real active site. This [Cu2O2] 3+ species was also generated by one-electron oxidation reaction of bis-mu-oxo dicopper(III) or side-on peroxo dicopper(II) complexes, respectively. And it might possess either a [CuIIICuIVO 2]3+ or a [CuIIICuIII(O)(O·)] 3+ structure based on further characterizations. The reactivity of the new [Cu2O2]3+ species toward different substrates was investigated, which shows a much higher reactivity toward substrates comparing to the side-on peroxide or bis-mu-oxo complexes.;In Chapter 4, an intermediate generated by copper complex [Cu(II) 2(Nn)]2+ (n = 4∼5) with H2O 2, which may site-specifically cleave a DNA strand, was investigated. This intermediate shows a characteristic absorption at 376 nm. Further inetic studies of the evolution of this intermediate as well as characterizations indicate that the intermediate might contains a hydroperoxobridged copper(II) core. An intramolecular electron transfer from ligand to a metal-peroxo center was proposed based on the detection of hydroxyl radial and the decomposed ligand analysis.