Photoredox Catalysis: The Reaction Mechanism Can Adjust to Electronic Properties of a Catalyst
Katarzyna Goliszewska, Katarzyna Rybicka‐Jasińska, John A. Clark, Valentine I. Vullev, Dorota Gryko
Abstract
Photochemistry provides paths to reactive intermediates that are often inaccessible by any other means. Most organic molecules, however, are colorless and require photocatalysts absorbing in the visible spectral region for transferring the required energy and charges. The electrochemical potentials of a photocatalyst, along with its optical excitation energy, guide its selection for driving oxidative or reductive reactions. Such selection criteria, however, frequently undermine the complexity of the transformations and prove limiting. Herein, we demonstrate how electron-rich and electron-deficient photoredox catalysts, with distinctly different reduction potentials, successfully drive the same reaction with similarly good yields. The analysis reveals that the large differences between the optical and electrochemical frontier-orbital energy gaps cause switching between two parallel reaction pathways—oxidative versus reductive quenching. This finding demonstrates a paradigm where reaction mechanism adjusts to the electronic properties of catalysts and opens doors for diversifying and broadening of the applicability of photochemical transformations.