Unraveling the Nucleation Process from a Au(I)-SR Complex to Transition-Size Nanoclusters

Atomically precise noble metal nanoclusters provide a critical benchmark for the fundamental research of the origin of condensed matter because they retain the original state of the metal bonds. Also, knowledge about the transition from organometallic complexes to a nanoclusters is important for understanding the structural evolution of the nanoclusters, particularly their nucleation mechanism. Herein, three transition-size gold nanoclusters are prepared via a controlled diphosphine-mediated top-down routine. Starting from small-size nanoclusters, three new nanoclusters including Au₁₃(SAdm)₈(L⁴)₂(BPh₄) (Au), Au₁₄(S-c-C₆H₁₁)₁₀L⁴ (Au), and Au₁₆(S-c-C₆H₁₁)₁₁L^Ph* (Au) are obtained by controlled clipping on the surface and kernel of initial nanoclusters. Combining their atomically precise structures with DFT theoretical calculations, the overall atom-by-atom structural evolution process from Au₁₂(SR)₁₂ (0 e^-) to Au₁₈(SR)₁₄ (4 e^-) is mapped out. In addition, studies on their electronic structures show that the evolution from an organometallic complex to nanoclusters is accompanied by a dramatic decrease in the HOMO-LUMO gaps. Most importantly, the formation of the first Au-Au bond is captured in the "Au₄S₄ to Au₅" nucleation process from Au₁₂(SR)₁₂ complex to the Au nanocluster. This work provides a deep insight into the origin of inner core in Au NCs and their structural transition relationship with metal complexes.