Air-Sensitive Photoredox Catalysis Performed under Aerobic Conditions in Gel Networks
journal contributionposted on 2018-05-29, 00:00 authored by Marleen Häring, Alex Abramov, Keisuke Okumura, Indrajit Ghosh, Burkhard König, Nobuhiro Yanai, Nobuo Kimizuka, David Díaz Díaz
In this work, we demonstrate that useful C–C bond-forming photoredox catalysis can be performed in air using easily prepared gel networks as reaction media to give similar results as are obtained under inert atmosphere conditions. These reactions are completely inhibited in homogeneous solution in air. However, the supramolecular fibrillar gel networks confine the reactants and block oxygen diffusion, allowing air-sensitive catalytic activity under ambient conditions. We investigate the mechanism of this remarkable protection, focusing on the boundary effect in the self-assembled supramolecular gels that enhances the rates of productive reactions over diffusion-controlled quenching of excited states. Our observations suggest the occurrence of triplet-sensitized chemical reactions in the gel networks within the compartmentalized solvent pools held between the nanofibers. The combination of enhanced viscosity and added interfaces in supramolecular gel media seems to be a key factor in facilitating the reactions under aerobic conditions.