The Wavelength Matters - Controlling the Selectivity of Photocatalytic Reactions Using Different Colors of Light

Visible-light photocatalysis is a relatively young branch of organic chemistry that quickly became an integral part of the synthetic chemists’ toolbox. This results from the synthetic potential of photochemistry that allows unlocking unique reaction pathways unavailable to conventional ground-state reactivity. Photons are used as traceless, sustainable reagents to excite photocatalysts that ultimately induce reactions through energy-, and single electron transfer events with substrates, reagents or co-catalysts under mild conditions. However, most photocatalytic reactions rely on a small set of photocatalysts that are typically activated with high-energy visible-light (<450 nm) to achieve efficient reactions.

The energy (and intensity) of photons are overlooked parameters that can be used to gain control over the selectivity and to improve the reproducibility of light-mediated reactions. This requires photocatalysts that broadly absorb over the visible-light spectrum. In this talk, I will discuss examples where tuning the irradiation wavelength is crucial to avoid follow-up reactions, substrate degradation^[1] and the deactivation of co-catalysts.^[2] Moreover, I will show that the irradiation wavelength can be used to control the reactivity of a photocatalyst by controlling its excited state oxidation potential.^[3] Finally, I will present our first efforts towards light-mediated nickel-catalyzed cross-couplings that do not require exogeneous photocatalyst.^[4]

[1]     C. Cavedon, E. Sletten, A. Madani, O. Niemeyer, P. H. Seeberger, B. Pieber, Org. Lett. 2021, 23, 514

[2]      S. Gisbertz, S. Reischauer, B. Pieber, Nat. Catal. 2020, 3, 611

[3]      L. Schmermund, S. Reischauer, S. Bierbaumer, C. K. Winkler, A. Diaz-Rodriguez, L. J. Edwards, S. Kara, T. Mielke, J. Cartwright, G. Grogan, B. Pieber, W. Kroutil, Angew. Chem. Int. Ed. 2021, 60, 6965

[4]      C. Cavedon, S. Gisbertz, S. Reischauer, S. Vogl, E. Sperlich, J. H. Burke, R. F. Wallick, S. Schrottke, W.-Hs. Hsu, L. Anghileri, Y. Pfeifer, N. Richter, C. Teutloff, H. Müller-Werkmeister, D. Cambié, P. H. Seeberger, J. Vura-Weis, R. M. van der Veen, A. Thomas, B. Pieber, Angew. Chem. Int. Ed. 2022, 61, e202211433