Development of Super-Reducing Redox Photocatalysts

Redox photocatalysis is more and more popular in synthetic and pharmaceutical chemistry for preparing organic compounds is mild conditions. It aims to convert visible light absorbed by a photocatalyst into charges (electron and/or holes) with redox potentials well adapted for performing reduction and/or oxidation reactions. These reactions can be very efficient and enable the formation of one or more bonds, typically between carbon atoms. Very few studies deal with the use of CO2 as carbon source in redox photocatalysis for the functionalization of complex organic molecules. This is due to the very reducing redox potential needed for generated radical species from CO2. We propose in this PhD project to study and develop a new class of “super-reducing” photocatalysts, which enable to accumulate the energy of two photons before transmitting one electron to the targeted molecule at a very reducing redox potential. Two types of photocatalysts will be investigated: 1/ organic photocatalysts from the perylenediimide and from the heptazine families. It that case the first photon enable to generate the anion radical of the photocatalyst, who is excited by the second photon to reach extremely reducing redox potentials. 2/ Quantum dots (CdS, ZnSe…) that will also be excited by successive photons. Such new “super-reducing” photocatalysts are expected to give access to redox potentials as low as -3.2 V/SCE. During this PhD thesis, this photocatalysts will be developed and used for exploring new pathway for reactions with CO2 and other redox reactions that were not possible up to now in organic synthesis.

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