Hot Electron-Induced Carbon–Halogen Bond Cleavage Monitored by in Situ Surface-Enhanced Raman Spectroscopy

The activation of the carbon–halogen (C–X) bond is of great significance in chemical synthesis. Herein, we report on in situ surface-enhanced Raman spectroscopic monitoring of hot electron-induced C–X bond cleavage on noble metal nanoparticle (NP) monolayers. We find that the cleavage is closely related to the localized surface plasmon resonance on metal surfaces, which is simulated using the three-dimensional finite-difference time-domain method. Because of higher plasmonic activity, the dissociation of the C–X bond on 80 nm Ag NP monolayers is much faster than that on 40 nm Ag and 80 nm Au NP monolayers. By adding hole compensators for continuous generation of hot electrons, the reaction can be greatly improved, indicating that the plasmonic hot electrons are responsible for dehalogenation. Finally, the mechanism of hot electron-induced C–X bond cleavage with an intermediate of carbon radicals is proposed. This work provides new opportunities for C–X activation by using plasmonic metals which will benefit the highly efficient conversion of aryl halide compounds.