Sensitization-Initiated Electron Transfer for Photoredox Catalysis

Photosynthetic organisms exploit antenna chromophores to absorb light and transfer excitation energy to the reaction center where redox reactions occur. In contrast, in visible-light chemical photoredox catalysis, a single species (i.e., the photoredox catalyst) absorbs light and performs the redox chemistry. Mimicking the energy flow of the biological model, we report a two-center photoredox catalytic approach in which the tasks of light energy collection and electron transfer (i.e., redox reactions) are assigned to two different molecules. Ru(bpy)3 Cl2 absorbs the visible light and transfers the energy to polycyclic aromatic hydrocarbons that enable the redox reactions. This operationally simple sensitization-initiated electron transfer enables the use of arenes that do not absorb visible light, such as anthracene or pyrene, for photoredox applications. We demonstrate the merits of this approach by the reductive activation of chemical bonds with high reduction potentials for carbon-carbon and carbon-heteroatom bond formations.