Spectroscopic Techniques to Unravel Mechanistic Details in Light-Induced Transformations and Photoredox Catalysis

The rapid development of photo(redox) catalysis within the last decades is remarkable to the extent that the utilization of light-driven processes in organic chemistry has become a credible alternative to current thermal processes. Such advances offer tremendous opportunities of collaborations between scientific realms that can have a drastic impact on the development of the field. In this concept article, a special emphasis is placed on spectroscopic techniques that are used, or could be used, for light-induced transformations and photoredox catalysis applications. These include spectroelectrochemistry, UV-VIS, IR and X-Ray transient absorption spectroscopy, laser pulsed radiolysis (PR), photo-induced chemically induced dynamic nuclear polarization (Photo-CIDNP), photoacoustic spectroscopy, time-resolved Raman spectroscopy (TRRS), time-resolved Electron Paramagnetic Resonance (TREPR) and time-resolved dielectric loss spectroscopy (TRDL). The theoretical background behind each technique is briefly introduced followed by selected relevant examples from the literature. Several spectroscopic techniques available to determine key mechanistic processes in light-induced transformations and photoredox catalysis application are described. The reader is provided with a brief theoretical background as well as selected illustrative examples from the literature. The concept article ends with a personal perspective on the different avenues that will play a major impact in the future.image