Molecular Gold Nanocluster Au156 Showing Metallic Electron Dynamics

The boundary between molecular and metallic gold nanoclusters is of special interest. The difficulty in obtaining atomically precise nanoclusters larger than 2 nm limits the determination of such a boundary. The synthesis and total structural determination of the largest all-alkynyl-protected gold nanocluster (Ph4P)(6)[Au-156(C CR)(60)] (R = 4-CF3C6H4-) (Au-156) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au-156 has a rod shape with the length and width of the kernel being 2.38 and 2.04 nm, respectively. The cluster contains a concentric Au-126 core structure (Au-46@Au-50@Au-30) protected by 30 linear RC C-Au-C CR staple motifs. It is interesting that Au-156 displays multiple excitonic peaks in the steady-state absorption spectrum (molecular) and pump-power-dependent excited-state dynamics as revealed in the transient absorption spectrum (metallic), which indicates that Au-156 is a critical crossover cluster for the transition from molecular to metallic state. Au-156 is the smallest-sized gold nanocluster showing metal-like electron dynamics, and it is recognized that the cluster shape is one of the important factors determining the molecular or metallic nature of a gold nanocluster.

Automated summary

The study focuses on the boundary between molecular and metallic gold nanoclusters, presenting the synthesis and structural determination of the largest all-alkynyl-protected gold nanocluster, Au-156. The cluster's rod shape with concentric core structure displays metal-like electron dynamics, suggesting Au-156 as a key crossover cluster for the transition from molecular to metallic state. The shape of the cluster is identified as one of the crucial factors in determining the molecular or metallic nature of a gold nanocluster.