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

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. [Display omitted] •Environmentally benign approach for the selective reduction of nitroarenes.•Reduction is catalysed by white LED light irradiation in aqueous medium.•Mechanistically the hot electrons at the plasmonic Ni/Ag@resin surface activate the reduction.•Time dependent SERS monitoring elucidates the tandem photoreduction mechanism.•Cis-4,4′-dimercaptoazobenzene (DMAB) is the intermediate in the photoreduction of 4-NTP SAM.