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.