Letter | Published:

Photoredox catalysis using infrared light via triplet fusion upconversion


Recent advances in photoredox catalysis have made it possible to achieve various challenging synthetic transformations, polymerizations and surface modifications1,2,3. All of these reactions require ultraviolet- or visible-light stimuli; however, the use of visible-light irradiation has intrinsic challenges. For example, the penetration of visible light through most reaction media is very low, leading to problems in large-scale reactions. Moreover, reactants can compete with photocatalysts for the absorption of incident light, limiting the scope of the reactions. These problems can be overcome by the use of near-infrared light, which has a much higher penetration depth through various media, notably biological tissue4. Here we demonstrate various photoredox transformations under infrared radiation by utilizing the photophysical process of triplet fusion upconversion, a mechanism by which two low-energy photons are converted into a higher-energy photon. We show 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 light, by pairwise manipulation of the sensitizer and annihilator. We further demonstrate that the annihilator itself can be used as a photocatalyst, thus simplifying the reaction. This approach enables catalysis of high-energy transformations through several opaque barriers using low-energy infrared light.

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The data that support the findings of this study are available from the corresponding authors on reasonable request.

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Change history

  • 15 May 2019

    In Fig. 1c of this Letter, the orange axis label of the graph should have read ‘FDPP upconversion photoluminescence (AU)’ instead of ‘TTBP upconversion photoluminescence (AU)’. This has been corrected online.


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L.M.C. thanks the National Science Foundation (NSF CAREER DMR-1351293) for funding. A.B.P. thanks the NSF Graduate Research Fellowship Program (DGE-16-44869). D.N.C. is supported by the Rowland Fellowship at the Rowland Institute at Harvard. T.R. thanks the National Institute of General Medical Sciences (GM125206).

Author information

A.B.P. and D.N.C. carried out the upconversion experiments. B.D.R., A.B.P. and E.M.C. performed and analysed the photoredox and materials penetration experiments. D.N.C., T.R. and L.M.C. initiated and directed the study, and wrote the manuscript with contributions from all authors.

Competing interests

A provisional patent has been filed on this technology by the institutions on behalf of the authors of this work (US Provisional Application 62/641,739).

Correspondence to Daniel N. Congreve or Tomislav Rovis or Luis M. Campos.

Supplementary information

  1. Supplementary Information

    This file contains supplementary text, which includes supplementary figures S1-S10 and supplementary table S1.

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Further reading

Fig. 1: The NIR-to-orange and NIR-to-blue upconversion strategy.
Fig. 2: Selected examples of reactions driven by NIR light.
Fig. 3: Material penetration experiments.
Fig. 4: Application of the Beer–Lambert law to blue and NIR light.


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