Interfacial-Environment-Regulated Radical Pathways in Plasma-Induced C-X Bond Transformation

Understanding how interfacial environments regulate radical-mediated activation and transformation of carbon-halogen (C-X) bonds is essential for advancing selective organic synthesis and sustainable halogenated compound conversion. Herein, we elucidate the interfacial-environment-regulated radical pathways governing C-X bond activation of 3-bromothiophenol (3-BrTP) on Au(111). Helium low-temperature plasma serves as a controllable source of reactive radicals, while tip-enhanced Raman spectroscopy (TERS) enables nanoscale visualization of reaction products. TERS imaging reveals distinct distributions of coupling and hydroxylation products, indicating environment-dependent radical pathways. Interfacial water is found to steer the transformation from aryl-aryl coupling toward hydroxylation, whereas the presence of CO₂ or bicarbonate redirects radicals toward selective carboxylation. These findings uncover the fundamental role of interfacial microenvironments in dictating radical reaction selectivity and provide a mechanistic foundation for environmentally benign and controllable C-X bond activation processes.