Regioisomeric Effect on the Photocatalytic Properties of Photoluminescent Aromatic Cyano‐Methoxybenzenethioethers

Organic donor−acceptor photocatalysts are very appealing for the discovery and effective application in photocatalytic transformations, for which the understanding of the structural implications in their photoactivity is key for success. In this work, the structure‐photocatalytic activity relationship of a regioisomeric series of cyanoarene‐based systems bearing methoxythiophenol units as donor groups is presented. To this aim, their activity in two distinct photoredox and triplet‐triplet energy transfer (EnT)‐catalyzed reactions is evaluated. On the one hand, while all catalysts show good oxidizing properties in the excited state, photochemical partial degradation leading to a mixture of photoactive species hampers the correlation between the redox potentials of the initial species and the observed reactivity on a test photoredox reaction. On the other hand, two structure–property relationships could be identified in the case of the test EnT reaction. Thus, a para ‐dicyanobenzene backbone leads to higher triplet energies, followed by the meta and ortho isomers, while meta ‐methoxythiophenol donor groups prove more efficient for applications in EnT catalysis. Hence, this study allows for the identification of key structural features, as well as good candidates for each targeted reaction, showing the potential of aromatic thioethers as photocatalysts for a variety of light‐mediated processes.