Overall structure of Au 12 Ag 60 (S- c -C 6 H 11 ) 31 Br 9 (Dppp) 6 : achieving a stronger assembly of icosahedral M 13 units.

Precise atomically assembled nanoclusters provide a great platform to elucidate the evolution of the assembly of building blocks. Herein, a large icosahedral (M ₁₃ )-based silver-gold alloy nanocluster [Au ₁₂ Ag ₆₀ (S- c -C ₆ H ₁₁ ) ₃₁ Br ₉ (Dppp) ₆ ]Br ₂ (dppp = 1,3-bis(diphenylphosphino)propane) is reported. Structurally, Au ₁₂ Ag ₆₀ consists of an Au ₁₂ Ag ₄₀ kernel, which is viewed as the interpenetration of ten twisted complete icosahedrons (M ₁₃ ) and two missing icosahedrons (M ₁₂ ), and this is surrounded by a complex metal-organic shell. Benefiting from the extra doping of eight to twelve Au atoms, the octameric assembly was increased to a twelve-mer assembly. The time-dependent density functional theory (TDDFT) method with a Tamm-Dancoff approximation (TDA) was performed to investigate the difference in the optical properties of Au ₁₂ Ag ₆₀ and Au ₈ Ag ₅₇ . The results indicate that the difference in the amount of Au atoms results in different optical properties. Furthermore, transient absorption spectroscopy (TA) was also performed, revealing that a twelve-mer assembly greatly enhances the excited-state lifetime. The [Au ₁₂ Ag ₆₀ (S- c -C ₆ H ₁₁ ) ₃₁ Br ₉ (Dppp) ₆ ]Br ₂ alloy nanocluster has provided a breakthrough in the number of icosahedral M ₁₃ assemblies, i.e. , achieving a twelve-mer assembly, helping to elucidate the fusion growth of M ₁₃ -based assembled nanoclusters as well as their geometric/electronic structure correlations, which will promote further research on the assembly of M ₁₃ nano-building blocks, especially on their optical properties.