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 H 2 O 2 as an oxidant) is more important than its monooxygenase functionality. Here, we describe new insights into peroxygenase activity, with a copper(I) complex reacting with H 2 O 2 leading to site-specific ligand–substrate C–H hydroxylation. [Cu I (TMG 3 tren)] + ( 1 ) (TMG 3 tren = 1,1,1-Tris{2-[ N 2 -(1,1,3,3-tetramethylguanidino)]ethyl}amine) and a dry source of hydrogen peroxide, ( o -Tol 3 P═O·H 2 O 2 ) 2 react in the stoichiometry, [Cu I (TMG 3 tren)] + + H 2 O 2 → [Cu I (TMG 3 tren-OH)] + + H 2 O, wherein a ligand N -methyl group undergoes hydroxylation giving TMG 3 tren-OH. Furthermore, Fenton-type chemistry (Cu I + H 2 O 2 → Cu II -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.