Biomimetic chemistry

Galactose oxidase is a copper enzyme of fungal origin that catalyzes the two-electron oxidation of a wide range of primary alcohols to their corresponding aldehydes with concomitant reduction of dioxygen to hydrogen peroxide. Its active site contains a single copper ion coordinated to two equatorial histidines, one axial tyrosine as well as an equatorial post-translationally modified tyrosine (Tyr₂₇₂). This later modification implies a cross-link in ortho position with a neighboring cysteine residue. It is believed to facilitate the oxidation of Tyr₂₇₂into a tyrosyl radical, whose half-life reaches the remarkable value of seven days. This radical cofactor has been extensively studied and it has been estimated that ca. 20 % of the spin density delocalizes over Cys₂₂₇.

In order to reproduce the active site of Galactose oxidase and gain insight into the copper-radical interplay we have designed several metal complexes featuring pro-radical moieties (phenolate/phenoxyl, aniline/anilinyl, a-diiminebis(thiosemicarbazone)…). We explore different scaffolds, including tripodal, salen and dipyrrin platforms in order to finely tune the metal ion geometry. These versatile platforms also allow for the facile tuning of the ligand electronics. We develop synthetic procedures and investigate the coordination chemistry, the spectro-electrochemistry and the reactivity of these biomimetic complexes.