White LED light mediated green photoreduction of nitroarenes to anilines on bimetallic Ni/Ag@resin: In situ SERS monitoring and evaluation of plasmonic effect

Abstract

Reduction of nitroarenes to anilines, a potentially important organic transformation, is classically performed in harsh conditions, which have long lasting safety issues and wastage of energy. Herein, we report an efficient hot-electron induced reduction of nitroarenes to the corresponding anilines over bimetallic Ni/Ag@resin in presence of NaBH4 under white LED light irradiation. Mechanistically, the hot electrons assisted the dimerization of 4-NTP to cis-4,4′-dimercaptoazobenzene as the active intermediate evidenced by appearance of SERS peaks at 1389 cm−1. Hot electrons having energy content above a threshold can transfer the energy effectively to the LUMOs of the reactant nitroarenes. Overall the present catalyst system constitutes one straightforward and environmentally safe approach to a class of much sought organic transformation.