Mechanistic studies of NOx reduction reactions involving copper complexes: encouragement of DFT calculations

The reduction of nitrogen oxides (NO_x), which is mainly mediated by metalloenzymes and metal complexes, is a critical process in the nitrogen cycle and environmental remediation. This Frontier article highlights the importance of density functional theory (DFT) calculations to gain mechanistic insights into nitrite (NO₂⁻) and nitric oxide (NO) reduction reactions facilitated by copper complexes by focusing on two key processes: the reduction of NO₂⁻ to NO by a monocopper complex, with special emphasis on the concerted proton–electron transfer, and the reduction of NO to N₂O by a dicopper complex, which involves N–N bond formation, N₂O₂ isomerization, and N–O bond cleavage. These findings underscore the utility of DFT calculations in unraveling complicated reaction mechanisms and offer a foundation for future research aimed at improving the reactivity of transition metal complexes in NO_x reduction reactions.