PET-Cat

The primary objective of this project is to develop an innovative process to photoactivate copper-based catalysts through photoinduced electron transfer (PET). Considering transition metal catalysts, generation of a highly active catalytic species on demand by light irradiation of an inactive precatalyst presents several key benefits, particularly for large batch synthesis : 1) handling metal species that are stable under ambient conditions; 2) switching on catalysis at a given time and place; 3) tuning the onset of the generated active catalyst by controlling the photoactivation process, which would be valuable for highly exothermic reactions conducted on a large scale. To date, most examples of photocontrolled transition metal catalysts are the so–called photocaged catalysts, which rely on the photodissociation or photodecomposition of ligands in coordinatively saturated metal complexes to generate vacant active sites. We recently reported the first example of catalyst activation driven by photoinduced electron transfer to a metal cation (Angew. Chem. Int. Ed. 2012, 51, 7137-7141; Selected as “Very Important Paper”). We applied this concept to the copper(I)–catalyzed alkyne–azide cycloaddition (CuAAC), and have shown that it represents a powerful strategy to switch on the activity of a metal catalyst that is inactive in its high–valent oxidized form but active in its low–valent reduced form. During this three year project we wish to build on our promising preliminary findings to develop photoactivable copper catalysts of practical value for important copper(I)-catalyzed reactions. To reach this objective, we will focus on: 1) Ligand and photosensitizer optimization; 2) Photoreduction mechanism study; 3) Application of the photoactivable catalysts to major coupling reactions, i.e. the Huisgen cycloaddition and Ullmann-type couplings. The project will be conducted through collaborations between experts of organic/coordination chemists and physical-chemists specialized in transition metal complex photophysics and spectroscopies.