THE SEARCH FOR A BIO-INSPIRED PHOTOCATALYST…
The oxygen molecule is undoubtedly the most environment-friendly oxidizing agent, but because of its triplet ground state, it does not easily oxidize organic compounds (hydrocarbons) widely used in the industrial world, which requires very polluting processes. In order to achieve these transformations in a catalytic and clean way, bio-inspired reactions by Oxygen Atoms Transfer (OAT) are the subject of numerous studies. If the formation of the active species with a high oxidation state is relatively well known in the case of OAT, the challenge lies in the design of photocatalysts using abundant elements such as water and dioxygen from the air as oxygen sources. Natural enzymes capable of performing such reactions have been used as models for the design of robust catalysts, such as the bio-inspired Fe(II) complex used in this study. The use of a light energy source, instead of a chemical one, is also sought in order to reduce the waste produced during these reactions.
FOR A GREENER OXIDATION OF ALKENES
In this work, the researchers coupled a photo-redox module with a bio-inspired non-heme Fe(II) catalyst to activate O2 in the OAT reaction. In order to highlight the multiple competing electron transfer steps, the charge accumulation and annihilation processes and the activation of O2 to superoxide (O2·-) at the catalytic unit, they combined several spectroscopic techniques. They succeeded in identifying the Fe(III)-hydroperoxo intermediate species capable of transferring oxygen atoms to alkenes to form epoxides and aldehydes, the building blocks of alkene chemistry.
The knowledge gained in this study will be useful to optimize the overall efficiency of the system and give confidence to the proposed catalytic cycle that requires only water as solvent. A step towards a cleaner chemistry of oxidation reactions in aqueous media.
Contacts : Ally Aukauloo (ally.aukauloo@universite-paris-saclay.fr) ; Winfried Leibl (winfried.leibl@cea.fr)