Ravetz, BenjaminPun, AndrewChurchill, EmilyCongreve, DanielRovis, TomislavCampos, Luis2020-12-162019-01Ravetz, B.D., Pun, A.B., Churchill, E.M. et al. Photoredox catalysis using infrared light via triplet fusion upconversion. Nature 565, 343–346 (2019). https://doi.org/10.1038/s41586-018-0835-20028-08361476-4687https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37366586Recent advances in photoredox catalysis have made it possible to execute a multitude of challenging synthetic transformations, polymerizations, and surface modifications. In all cases, these transformations require ultraviolet or visible light stimuli. Herein, we demonstrate a variety of photoredox transformations under infrared radiation by utilizing the photophysical process of triplet fusion upconversion. We illustrate that this is a general strategy applicable to a wide range of photoredox reactions. We tune the upconversion components to adjust the output light, accessing both orange light and blue light from low-energy infrared (IR) light, by pair-wise manipulation of the sensitizer and annihilator. We further demonstrate that the annihilator itself can be used as a photocatalyst, simplifying the reaction. This approach allows us to execute catalysis through several barriers that are impenetrable by visible light. The results demonstrated here allow high-energy transformations from low-energy IR light with all the benefits that the latter affords.en-USMultidisciplinaryJournal Article2020-12-1610.1038/s41586-018-0835-2