Identifying the superatomic AuCu₅₆ nanocluster through a ligand-exchange coupled metal-exchange induced transformation

Quantum-sized metal nanoclusters can be viewed as superatoms that mimic the electron-shell closing behaviours of atoms, where these electronic shell configurations often govern their properties. Various superatomic nanoclusters with diverse structures and valence states have been identified over the past few years, but the 1S valence state of atomically precise Au nanoclusters has rarely been seen. Herein, we have achieved the synthesis of a 1S¹ superatomic [AuCu₅₆S₁₂(SAdm)₂₀(O₃SAdm)₁₂] nanocluster from the eight-electron [Au₂₃(S-<i>c</i>-C₆H₁₁)₁₆]^- nanocluster <i>via</i> a ligand-exchange coupled metal-exchange induced transformation. Detailed studies through mass spectrometry provided insights into the nanocluster formation, and theoretical studies revealed the superatomic nature of the nanocluster. Moreover, the as-synthesized nanocluster exhibited a broad optical absorption, leading to good photocurrent response under UV illumination. This work introduces a novel doping strategy that enables us to realize a rare superatomic valence state in an alloy cluster and to explore its unique light-induced properties.