Radical-Induced Selective C─C Bond Activation at the Air-Solid Interface

Radicals are of great interest to trigger reactions in synthetic chemistry due to their high efficiency and unique reactivity, but their uncontrollable nature poses challenges in achieving selectivity. This study explores the influence of a surface/interface on radical reactions, leveraging a low-temperature plasma ionization source for radical generation. Combining insights from tip-enhanced Raman spectroscopy, mass spectrometry, and X-ray photoelectron spectroscopy, the selectivity of radical reactions of a model organic compound, biphenylthiol is investigated, under both homogeneous and heterogeneous conditions. The metal surface, acting as a template with interfacial water, is found to significantly modify the radical reaction pathway. The surface-immobilized BPT exhibited selective radical reaction products, forming 4-mercaptophenol molecules on Au(111) via the cleavage of C─C bonds. Such a high selectivity of radical reactions is unique and only achieved at the air/solid interface as compared to reactions in the gas, liquid, and solid phases. The present work highlights the potential of surfaces and interfaces in tailoring radical reaction pathways with high selectivity.