Fenton-like Chemistry by a Copper(I) Complex and H2O2 Relevant to Enzyme Peroxygenase C-H Hydroxylation

Abstract

Lytic polysaccharide monooxygenases have received significant attention as catalytic convertors of biomass to biofuel. Recent studies suggest that its peroxygenase activity (i.e., using H2O2as an oxidant) is more important than its monooxygenase functionality. Here, we describe new insights into peroxygenase activity, with a copper(I) complex reacting with H2O2leading to site-specific ligand-substrate C-H hydroxylation. [CuI(TMG3tren)]+(1) (TMG3tren = 1,1,1-Tris{2-[N2-(1,1,3,3-tetramethylguanidino)]ethyl}amine) and a dry source of hydrogen peroxide, (o-Tol3P═O·H2O2)2react in the stoichiometry, [CuI(TMG3tren)]++ H2O2→ [CuI(TMG3tren-OH)]++ H2O, wherein a ligand N-methyl group undergoes hydroxylation giving TMG3tren-OH. Furthermore, Fenton-type chemistry (CuI+ H2O2→ CuII-OH + ·OH) is displayed, in which (i) a Cu(II)-OH complex could be detected during the reaction and it could be separately isolated and characterized crystallographically and (ii) hydroxyl radical (·OH) scavengers either quenched the ligand hydroxylation reaction and/or (iii) captured the ·OH produced. © 2023 American Chemical Society. All rights reserved.