Extreme potential photocatalysis enabled by spin-exchange Auger processes in magnetic-doped quantum dots.

Visible-light-absorbing semiconductor nanocrystals have shown great promise as photocatalysts for promoting photoredox chemistry. However, their utilization in organic synthesis remains considerably limited compared to small molecule photosensitizers. Recently, the generation of hot electrons from quantum-confined systems has emerged as a powerful means of photoreduction, yet the efficiencies remain limited under mild conditions. In this study, we present an efficient hot-electron generation system facilitated by the spin-exchange Auger process in Mn-doped CdS/ZnS quantum dots. These hot electrons can be effectively utilized in a wide range of organic reactions, such as the Birch reduction and reductive cleavage of C-Cl, C-Br, C-I, C-O, C-C, and N-S bonds. Notably, these reactions accommodate substrate reduction potentials as low as -3.4 V versus the saturated calomel electrode. Through two-photon excitation, we achieve the generation of a "super" photoreductant using visible-light irradiation power that is only 1% of that previously reported for molecular and quantum dot systems. By modulating the intensity of light output, the spin-exchange Auger process enables the on/off generation of hot electrons, allowing for programmable assembly-point cross-coupling cascades. Our findings demonstrate the potential of quantum-confined semiconductors in facilitating challenging organic transformations that were unattainable with molecular photocatalysts.