Synergistic Photochemistry of Alcohols Catalyzed by Plasmonic Nanoparticles and a Metal Complex

In photocatalytic schemes, it is common practice to employ a sacrificial agent for scavenging photogenerated holes and enhancing the yield and efficiency of electron harvesting. However, little attention is paid to the chemistry triggered by hole-mediated oxidation. Here, we trace the chemical fate of aliphatic alcohols used as hole scavengers in the photoinduced synthesis of Au nanoparticles. Under the action of visible light and the [AuCl4]- precursor, the alcohol undergoes a sequence of reactions, including oxidation, C-C bond scission, and chlorination, to form a chloroalkane and a carbonyl compound. Mechanistic and parametric studies show that this atypical chemistry is activated by the Lewis-acidic metal center of [AuCl4]- and enhanced by photoexcited carriers generated by interband excitation of Au nanoparticles. This work presents a unique example of interplay between a heterogeneous photocatalyst and a metal complex. Exploiting such synergy can be a route to new catalytic reactions.