By Nuwanthik Dilrukshi Kumarage
The coupling of light-induced chemistry with NMR paves a new way for obtaining information about photoinduced reactions, including detailed structural determination, intermediates, mechanistic studies, and reaction mechanisms. The use of LED NMR to understand the overall photochemical processes requires quantitative tools like chemical actinometers to measure light intensity. However, the selection of in situ LED NMR actinometers are limited by NMR active nuclei. For this reason, we explore the applicability of widely accepted actinometers in LED NMR using both 1H and 13C NMR at different wave lengths (390 nm, 450 nm, and 520 nm) and apply the results to characterize photochemical reactions. Given that understanding of the irradiation conditions of LED sources are very important for quantitative results and that chemical actinometry results remain prone to user error, we seek to compliment the LED-optical fiber flux determination using an integration sphere. Finally, we obtained the quantum yields of the actinometers and the known photochemical reactions, by measuring the initial rates for the reaction at different concentrations to confirm the reproducibility and applicability of NMR actinometry.