Introducing Photochemical Action Plots as a Tool for Unlocking On-Off Switchable Behavior in a Polymeric Eosin Y Photocatalyst.

Photochemical action plots are a powerful tool for investigating the wavelength-dependent efficiency of photochemical processes. Herein, we apply the photochemical action plot methodology developed by the Barner-Kowollik team to a photocatalytic reaction, resulting in the first examples of photocatalytic action plots, paving the way for future in-depth explorations of the wavelength dependence of similar reactions. Specifically, we investigate the wavelength dependence of the catalytic oxidation capabilities of an Eosin Y functionalized polymer photocatalyst (P1) as well as a small molecule representative of the polymer bound Eosin Y moieties (EY) for the oxidation of triphenylphosphine. Introduction of zinc(II) ions into the system proved to drastically influence the optical absorption properties of both catalysts, accompanied by a pronounced influence on their wavelength-dependent reactivity profiles which is not predictable based on the absorption spectra. For P1, these changes can be reversed by metal-mediated single-chain nanoparticle (SCNP) formation upon base addition, giving access to a stimuli-responsive polymeric photocatalyst. Detailed analysis of the photocatalytic action plots enabled the identification of a suitable wavelength for the realization of an on-off switchable polymeric photocatalytic system.