Light-Induced Reactivity Switch at O₂-Activating Bioinspired Copper(I) Complexes

Using light to unveil unexplored reactivities of earth-abundant metal-oxygen intermediates is a formidable challenge, given the already remarkable oxidation ability of these species in the ground state. However, the light-induced reactivity of Cu-O₂ intermediates still remains unexplored, due to the photoejection of O₂ under irradiation. Herein, we describe a photoinduced reactivity switch of bioinspired O₂-activating Cu^I complexes, based on the archetypal tris(2-pyridyl-methyl)amine (TPA) ligand. This report represents a key precedent for light-induced reactivity switch in Cu-O₂ chemistry, obtained by positioning C-H substrates in close proximity of the active site. Open and caged Cu^I complexes displaying an internal aryl ether substrate were evaluated. Under light, a Cu-O₂ mediated reaction takes place that induces a selective conversion of the internal aryl ether unit to a phenolate-CH₂- moiety with excellent yields. This light-induced transformation displays high selectivity and allows easy postfunctionalization of TPA-based ligands for straightforward preparation of challenging heteroleptic structures. In the absence of light, O₂ activation results in the standard oxidative cleavage of the covalently attached substrate. A reaction mechanism that supports a monomeric cupric-superoxide-dependent reactivity promoted by light is proposed on the basis of reactivity studies combined with (TD-) DFT calculations.