Abstract: High-valent Cu(III) complexes have long been proposed as important intermediates in biological redox processes and organic transformations involving the activation of C-H bonds. However, the proposed high-valent Cu(III) intermediates often elude detection due to their fleeting lifetimes. In the first part of my talk, I will present a series of dicopper (II,III) coordination complexes as models to understand the reactivity of NO and NO2- at dicopper enzymes. We discovered that dicopper complex canactivate NO or NO2- to generate a unique dicopper (II,III) oxo nitrosyl species [Cu2(μ-O)(μ-NO)]2+. Inspired by the oxidative reactivity of dicopper (II,III) oxo nitrosyl species, we developed a catalytic C-H hydroxylation strategy using NO as terminal oxidant. In the second part of my talk, I will discuss how synthetic models of monocopper oxygenases can be applied in the synthesis of pharmaceutically relevant organic molecules. Inspired by lytic polysaccharide monooxygenases, we develop a general CuII/CuIII platform to activate simple nucleophiles (Nu) toward C-H functionalization. Oxidation of CuII-Nu to CuIII-Nu endows the Nu moiety with hydrogen atom transfer and radical capture reactivity. Building on this platform, we have established a catalytic C-H fluorination method that selectively produces monofluorinated products in an undivided electrochemical cell at room temperature.