Photoinduced chemical transformations have become a pivotal area for Small Molecule Process R&D, showing significant promise in small molecule development programs. Recent advancements in LED technology have provided stable and tunable light sources, improving the reliability of photochemical processes. However, substantial challenges persist in photon delivery and the scaling of these processes from laboratory settings to commercial plants. The measurement of absorbed photon equivalents can serve as a valuable scaling parameter, enhancing our understanding of the system's dynamics and informing optimal reactor configurations to maximize light efficiency. Traditionally, potassium iron oxalate has been considered the gold standard for actinometry, but its complexity and limitations hinder its implementation at scale. Consequently, there is a pressing need for safe, inexpensive and user-friendly alternatives that effectively measure photon absorption in diverse environments. This study introduces a rapid and reversible thermal actinometric technique based on a food-grade dye (Yellow 6), offering an innovative method for quantifying absorbed photons in photoreactors. By correlating enthalpy changes from photoinduced cis-trans isomerization with photon absorbance, we address the limitations of traditional methods. Our technique serves as a practical and effective alternative, particularly in high light-density conditions. This presentation will detail our scaling methodology for characterizing advanced reaction systems within this framework. Through this research, we aim to improve the accuracy and scalability of light-driven chemical processes in both laboratory and industrial applications.
