ESI‐MS‐Visualization of Cyanoarene Photocatalysts by Specific Supramolecular Interaction with Br‐Anion

Abstract Isophthalonitrile derivatives (IPNs) have emerged as promising organic photocatalysts due to their efficiency and accessibility; however, their inherent lability under light‐induced conditions poses significant challenges in monitoring their transformation pathways. Understanding these pathways is crucial for optimizing photocatalytic processes and enhancing reaction efficiency. In this study, we present a novel approach utilizing electrospray ionization mass spectrometry (ESI‐MS) to visualize cyanoarene photocatalysts by taking advantage of their specific supramolecular interaction with bromide anions. Our findings reveal that bromide ions facilitate the detection of IPNs and their transformation products with high sensitivity and selectivity, even in complex reaction environments. The interaction predominantly occurs in the gas phase, minimizing interference in solution‐based transformations. The developed anion‐enhanced detection (AED‐ESI‐MS) not only provides real‐time insights into photocatalyst behavior but also opens new possibilities for the detailed mechanistic investigation of light‐driven reactions. The proposed AED‐ESI‐MS approach using other anions may offer broad applicability and may be worth studying further across various photocatalytic systems.