Green-light photocatalytic reduction using dye-sensitized TiO2 and transition metal nanoparticles

Nitrobenzenes are cleanly reduced to anilines using Ru-sensitized TiO2 photocatalysts and green light irradiation, if very small amounts of transitions metal salts are added, which form metal nanoparticles of narrow size distribution under the experimental conditions. The catalyst system is prepared by simple mixing of the components and is therefore easy to apply in organic synthesis. As light sources, commercial high power LEDs or sunlight are used. We report the optimization of the reaction conditions, the effect of trace amounts of added metal salts and demonstrate the use of green light photoreduction in the conversion of several nitrobenzene derivatives.