Exploring Selective Photochemistry on Metal Surfaces through Wavelength-Dependent Light Excitation

Photochemical reactions offer several advantages such as external control through manipulation of the light source and independence from temperature. These features enable precise control over reaction pathways on demand through photochemistry. In this work, we explore photoinduced on-surface debrominated coupling. The reaction is triggered by photoirradiation using wavelengths ranging from 254 to 850 nm at room temperature. The multiple photoreaction processes were further elucidated by comparing the responses of the reaction outcomes to the electronic structure of the adsorbates. Notably, the charge transfer process facilitates chemical reactions in the near-infrared region. We also identify the direct intramolecular excitation under UV radiation, which exhibits the highest photoactivity. The proposed reaction mechanisms are further validated by our theoretical calculations. Finally, we demonstrate selective debrominated coupling on Au(111) using photochemistry. This study establishes a foundation for understanding photochemistry on metal surfaces and its applications in surface chemistry.