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Our work addresses the long-standing question of the preferred mechanism of CH activation in dioxodicopper
complexes, with implications for [Cu2O2]2+
-containing enzymes as well as homogeneous and
heterogeneous catalysts, which are capable of performing selective oxidation. Using density functional theory
(DFT), we show that the two proposed mechanisms, one-step oxo-insertion and two-step radical
recombination, have very distinct and measurable responses to changes in the electrophilicity of N-donors in
the catalyst. Using energy decomposition analysis, we calculate the electronic
interactions that contribute to transition state stabilization, and the effect of N-donors on these interactions.
The analysis shows that oxo-insertion, by virtue of possessing a late and charged transition state, is highly
sensitive to N-donor electrophilicity and barriers decrease with more electron-withdrawing N-donors. On the
other hand, the radical pathway possesses an early transition state and is therefore relatively insensitive to N-donor
variations. One possible strategy, going forward, is the design and execution of complementary
experiments to deduce the mechanism based on the presence or absence of N-donor dependence. We adopt
an alternative approach where DFT results are contrasted with prior experiments via Hammett relationships.
The remarkable agreement between experimental and calculated trends for oxo-insertion with
imidazole N-donor catalysts presents compelling evidence in favor of the one-step pathway for CH activation.