Structural and Spectroscopic Characterization of a Mononuclear Hydroperoxo-Copper(II) Complex with Tripodal Pyridylamine Ligands

Abstract

A model for the key intermediate in copper oxygenase reactions, the Cu(II)-OOH complex, was prepared with the novel tripodal pyridylamine ligand, bis(6-pivalamide-2-pyridylmethyl)(2-pyridylmethyl)amine. The HOO moiety is stabilized by hydrogen bonding to two amine H atoms (see structure on the right).

Oxidative Cleavage of Cellobiose by Lytic Polysaccharide Monooxygenase (LPMO)-Inspired Copper Complexes

“…Scheme 2) may be responsible for the optical features described, with ample precedent for μ-η 2 :η 2 -peroxo dicopper(II) complexes with intense absorption bands around 360 nm. 10,28 The few examples reported of monomeric, tetragonal cupric hydroperoxo, and hydroxo complexes feature LMCT bands that are blue-shifted relative to the dimeric peroxo-bridged species, 25−27 which is consistent with our observations. The similarity with the UV–vis absorption spectrum of the reaction mixture with [( 2BB )Cu I ] + and dioxygen (see Figure S10) further suggests the formation of peroxo dicopper(II) species in the reaction of Cu(I) with O 2 described above.…”

Probing the properties of the second coordination sphere of biologically relevant metal complexes using amide function.

“…In addition, the peroxide species was unambiguously characterized by resonance Raman spectroscopy and also ESI mass spectrometry. consistent with other reported Cu-OOH species (Wada, A. et al, 1998). This band has been assigned to a peroxo π* σ → Cu charge-transfer transition (Chen, P. et al, 2000).…”

“…Since Kitajima's report, many studies have focused on 1:1 and 2:1 copper/dioxygen model compounds, as well as structural models of laccase, as reported by Cole et al (Cole, A. P. et al, 1996). To date, only five mononuclear Cu-OOH species have been characterized, and only two of them by X-ray crystallography (Chen, P. et al, 2000;Wada, A. et al, 1998). On the other hand, 2:1 Cu/O 2 species have been investigated more intensely.…”

“…To circumvent this, Masuda and coworkers have utilized the properties of an amido-pyridine ligand to isolate and crystallographically characterize a novel end-on hydroperoxide species (Wada, A. et al, 1998). With this in mind, we investigated the reaction of hydrogen peroxide with a Cu(II) complex, 36, of the biologically relevant ligand L2 having two amide-functionalized imidazole pendants (Chapter V).…”

“…To date, only five mononuclear Cu-OOH species have been characterized, and only two of them by X-ray crystallography (Chen, P. et al, 2000;Wada, A. et al, 1998 To some extents, EXAFS spectroscopy has proved to be valuable, especially for dinuclear species where the second shell (Cu-Cu interaction) can be effectively characterized.…”