Total structural determination of alloyed Au15.37Cu16.63(S-Adm)20 nanoclusters with double superatomic chains

Abstract

Thiolated-alloy nanocluster Au_15.37Cu_16.63(S-Adm)₂₀ ((AuCu)₃₂ for short) has been synthesized. Single crystal X-ray crystallography (SC-XRD) proved that this cluster contains a Au₁₄Cu₆ core, which is composed of double superatom chains, two M₄(SR)₅ (M = Au/Cu) motifs, four Cu(SR)₂ monomer staples and two SR molecules at the waist. The composition of this nanocluster is confirmed by SC-XRD and further verified by XPS, EDX and ²H-NMR. Surprisingly, double superatom chains connect to each other only via two Au–Au bonds, which makes the kernel resemble a tunnel. Combined with DFT calculation and electronic structure analysis, it is further proved that the (AuCu)₃₂ nanocluster contains six 2e alloy superatomic Au₃Cu²⁺ units. This work is the first report showing that superatom units (CuAu₃²⁺) self-assembling to a hollow kernel maintain the superatom characteristic of metal nanoclusters, which enriches the fundamental knowledge of metal superatom clusters. The stable electronic structure of the nanocluster provides an experimental basis for theoretical analysis in the future. In addition, the hollow structure may be promising in catalytic applications.