Zhucheng Yang, Yuhan Yi, Yue Wang, Yongying Ye, Ruixuan Zhang, Guanyu Ma, Tiankai Chen, Wen Wu Xu, Jianping Xie
Materials achieve complexity from simple building blocks, yet directly capturing the atomic pathways of their dynamic assembly has remained a long-standing challenge. Here, we employ atomically precise gold nanoclusters as a model system to resolve a tetrahedral assembly toward [Au 25 (SR) 18 ] − (SR = thiolate). In this pathway, tetrabutylammonium acts as a supramolecular director, selectively stabilizing metastable intermediates and steering Au(I)–SR reduction along a dominant trajectory. High-throughput robotic synthesis combined with tandem in situ spectroscopy uncovers a growth sequence: Au(I)–SR → [Au 15 (SR) 13 ] 0 → [Au 20 (SR) 16 ] 0 → [Au 22 (SR) 16 ] 0 → [Au 23 (SR) 16 ] − → [Au 25 (SR) 18 ] − . The cluster core grows through the stepwise incorporation of Au 4 tetrahedral units from one to four corner-sharing tetrahedrons, culminating in a spontaneous rearrangement into a symmetric Au 13 . These results reveal atomic-level evidence that discrete Au 4 units direct cluster growth and fuse into higher-order building blocks, resolving a long-sought question in nanomaterial formation and establishing smart, data-driven synthesis as a powerful paradigm for decoding complex reaction networks.