Intramolecular Hydrogen Bonding Enhances Stability and Reactivity of Mononuclear Cupric Superoxide Complexes

[(L)­CuII(O2•–)]+ (i.e., cupric-superoxo) complexes, as the first and/or key reactive intermediates in (bio)­chemical Cu-oxidative processes, including in the monooxygenases PHM and DβM, have been systematically stabilized by intramolecular hydrogen bonding within a TMPA ligand-based framework. Also, gradual strengthening of ligand-derived H-bonding dramatically enhances the [(L)­CuII(O2•–)]+ reactivity toward hydrogen-atom abstraction (HAA) of phenolic O–H bonds. Spectroscopic properties of the superoxo complexes and their azido analogues, [(L)­CuII(N3–)]+, also systematically change as a function of ligand H-bonding capability.