Copper(II) Complexes as Functional Models for Lytic Polysaccharide Monooxygenase: A Kinetic Report

Abstract

Mononuclear copper(II) complexes based on the symmetric tridentate N3-donor ligands bis(pyridin-2-yl)methyl)amine (HBPA, L1) and its methylated counterpart, di(2-pyridylmethyl)amine (MeDPA, L2) have been prepared, characterized, and demonstrated as the functional models for lytic polysaccharide monooxygenase. These complexes disrupt the synthetic substrate, such as p-nitrophenyl--D-glucopyranoside (-PNPG) into p-nitrophenol (PNP) and D-allose via oxidative cleavage as LPMOs do in nature. The observed spectroscopic and kinetic analysis have revealed that the reaction proceeds via copper(II) hydroperoxide as intermediate, whose electronic spectral signature has appeared at 350 nm in the electronic absorption spectra with the formation rate of 1.61 and 9.06 × 10-3 s1 respectively for complexes 1 and 2. Especially the obtained product was newly appeared at 400 nm, indicates the formation of p-nitrophenol with the rate of 7.52 and 5.45 × 10-3 s1.for complexes 1 and 2 respectively. These results affirm the ability of copper complexes as the functional models of LPMOs.