Reactivity of a stable copper–dioxygen complex

Abstract

We report the isolation of a room temperature stable dipyrromethene Cu(O2) complex featuring a side-on O2 coordination. Reactivity studies highlight the unique ability of the dioxygen adduct for both hydrogen-atom abstraction and acid/base chemistry towards phenols, demonstrating that side-on superoxide species can be reactive entities.

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

“…A concerted O−O bond cleavage/O−H bond activation pathway is also plausible; further mechanistic studies will be required to differentiate between stepwise and concerted substrate oxidation. Additional experiments using 5,5‐dimethyl‐1‐pyrroline N ‐oxide (DMPO, 500 equiv), a known radical trapping agent used to probe O−O bond scission reactions, resulted in detection of LCu II (O−DMPO) by ESI‐MS (Figure S20) following warming of the reaction mixture. These results are consistent with the generation of two equivalents of oxidant per equivalent of copper peroxynitrite, with the two species deriving from O−O homolytic cleavage.…”

Copper(I)–Dioxygen Reactivity in the Isolated Cavity of a Nanoscale Molecular Architecture

“…So far, a variety of supporting ligands have been developed in synthetic modeling studies to stabilize mononuclear copper(II) superoxide complexes [Cu II (O 2 · – )] in both end‐on and side‐on binding modes with N 4 , N 3 , N 3 S, and N 2 donor sets. These studies provided important insights into the structure, physicochemical properties, and reactivity of the mononuclear copper(II) superoxide species .…”

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

“…This result rules against higher-order copper adducts participating in the rate-limiting step of peroxynitrite decay as suggested in the aqueous H + and CO 2 mediated decay pathways. Additional experiments using 5,5-dimethyl-1-pyrroline N-oxide (DMPO,500 equiv), aknown radical trapping agent used to probe O À Ob ond scission reactions, [59,60] resulted in detection of LCu II (O À DMPO) by ESI-MS (Figure S20) following warming of the reaction mixture.T hese results are consistent with the generation of two equivalents of oxidant per equivalent of copper peroxynitrite,w ith the two species deriving from OÀOh omolytic cleavage. We postulate that in the absence of substrate,t he putative cupryl intermediate goes on to hydroxylate the solvent through aradical rebound pathway to give LCu I and R À OH (R = solvent) before LCu I reacts with NO 2 C to yield LCu II À(NO 2 À )a st he final product (Scheme S1).…”

“…A concerted O À Obond cleavage/O À Hbond activation pathway is also plausible;f urther mechanistic studies will be required to differentiate between stepwise and concerted substrate oxidation. Additional experiments using 5,5-dimethyl-1-pyrroline N-oxide (DMPO,500 equiv), aknown radical trapping agent used to probe O À Ob ond scission reactions, [59,60] resulted in detection of LCu II (O À DMPO) by ESI-MS (Figure S20) following warming of the reaction mixture.T hese results are consistent with the generation of two equivalents of oxidant per equivalent of copper peroxynitrite,w ith the two species deriving from OÀOh omolytic cleavage.…”