Gold-doped silver nanocluster [Au₃Ag₃₈(SCH₂Ph)₂₄X₅]^2- (X = Cl or Br)

Here we report the single-crystal structure, experimental and theoretical characterization of a 41-metal atom Au-Ag alloy nanocluster [Au₃Ag₃₈(SCH₂Ph)₂₄X₅]^2- (1, X = Cl or Br). The nanocluster 1 is co-protected by thiolate and halogen atoms and features an all-metallic face-fused biicosahedral Au₂@AuAg₂₀ rod-like kernel enwrapped by the outermost Ag₁₈(SCH₂Ph)₂₄X₃ shell. Two sites on the surface of the biicosahedral kernel are partially occupied by Au and Ag atoms. The outer Ag₁₈(SCH₂Ph)₂₄X₃ shell is composed of two Ag₆S₆ cycles at the two poles and one Ag₆S₂X₃ arc at the equator with both 2- and 3-coordinated Ag atoms, which has not been observed in gold or silver nanoclusters ever before. Theoretical calculations elucidate its electronic structure as well as optical properties, thus producing informative correlations between its structure and properties. This nanocluster exhibits near-infrared (NIR) emission around 825 nm. This work (i) snapshots a rare crystal structure of an Au-doped silver alloyed nanocluster; (ii) gives a deep insight to understand how the capping ligand or anions affect the structure of the alloy nanocluster; and (iii) provides precise information about gold atom doping site that is very significant in the recognition of potential active catalytic sites of the alloy nanoparticles.