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.