Formally Copper(III)–Alkylperoxo Complexes as Models of Possible Intermediates in Monooxygenase Enzymes

Abstract

Reaction of [NBu4][LCuIIOH] with excess ROOH (R = cumyl or tBu) yielded [NBu4][LCuIIOOR], the reversible one-electron oxidation of which generated novel species with [CuOOR]2+ cores (formally CuIIIOOR), identified by spectroscopy and theory for the case R = cumyl. This species reacts with weak O−H bonds in TEMPO-H and 4-dimethylaminophenol (NMe2PhOH), the latter yielding LCu(OPhNMe2), which was also prepared independently. With the identification of [CuOOR]2+ complexes, the first precedent for this core in enzymes is provided, with implications for copper monooxygenase mechanisms.

Detection and Characterization of a Novel Copper‐Dependent Intermediate in a Lytic Polysaccharide Monooxygenase

“…From which it is estimated that a lower limit of the molar absorbance of the LPMO intermediate at 420 nm is between 1400 to 2200 m −1 cm −1 (using data from Figure A and 5A; assuming that two intermediates will result in one dimer). The above‐mentioned molar absorbance of the LPMO intermediate at 420 nm is within the range of other reported values on similar systems …”

“…‐HOTyr] + / [Cu III OH–HOTyr] species. This suggestion is supported by a long series of papers from Margerum, Meyerstein and Tolman . In the absence of substrate, this reactive [Cu II O . ]…”

“…Tolman and co‐workers has shown in a series of papers that LCu(III)‐OH complexes where L is various polydentate ligands can work as strong hydrogen‐atom abstraction reactions . Furthermore, Tolman and co‐workers has suggested that formally Cu III ‐alkylperoxo complexes could be models for possible intermediates in monooxygenase enzymes . The oxidation with H 2 O 2 of copper complexes with tri‐ and tetrapeptides has been reported by Margerum and co‐workers, showing that it was possible to form Cu III complexes with a lifetime of minutes.…”

Investigation of dioxygen activation by copper(ii)–iminate/aminate complexes

“…In this study, new bioinspired model copper(II) complexes have been employed in order to better understand the O2 activation mechanism by copper based metalloproteins. 62 More specifically, the synthesis, the structural and physicochemical characterization of a series of copper(II) compounds with the tetradentateamidate ligands, N-{2-[(2-pyridylmethylene)amino]phenyl}pyridine-2-carboxamide (Hcapca, Scheme 2) and its reduced analogue N-{2-[(pyridylmethyl)amino]phenyl}pyridine-2carboxamide (H2capcah, Scheme 2) are reported. These ligands were chosen because they have nitrogen donor atoms to mimic the environment of the copper in the oxidases, oxygenases and dioxygenases.…”

“…[26][27][28][29][30][31][32][33][34][35][36][37] The common oxidation states of copper found in biological systemsare considered to be I and II, but the last years there is a strong belief that oxidation state III might have potential importance in copper enzymes in biology. [38][39][40][41][42][43] Combined enzymatic and model studies have been used to unveil the mechanisms of dioxygen activation by copper proteins. 5,25,[44][45][46][47] It has been suggested for the most of the copper enzymes that the first step in dioxygen activation is the coordinationof dioxygen to copper ion and formation of the metal superoxo species.…”