Exploration of Formation and Size‐Evolution Pathways of Thiolate‐Gold Nanoclusters in the CO‐Directed [Au<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup> Synthesis
Jiao Peng, Pu Wang, Bingxin Wang, Lin Xiong, Hengzhi Liu, Yong Pei, Xiao Cheng Zeng
Abstract
Abstract An intermolecular association and decarboxylation mechanism is proposed to understand the experimental evidence of the stepwise 2 e − hopping in the reductant‐assisted thiolate‐gold cluster synthesis. Based on the newly proposed intermolecular reaction mechanism, a total of 19 molecular‐like reaction equations are deduced to account for the bottom‐up formation of 2 e − –8 e − gold nanoclusters in the CO‐directed [Au 25 (SR) 18 ] − synthesis. With these established reaction equations, atomic pathways of three prototype cluster‐size evolution reactions are comprehensively explored in the course of [Au 25 (SR) 18 ] − synthesis, namely, the conversion of 0 e − homoleptic Au (I) ‐SR complexes to the 2 e − intermediate Au 15 (SR) 13 cluster, the size‐evolution of 2 e − Au 15 (SR) 13 cluster to the 4 e − –8 e − cluster (stepwise 2 e − ‐hopping), and the isoelectronic addition reaction of [Au 23 (SR) 16 ] − to the [Au 25 (SR) 18 ] − . The studies reveal that the CO can combine with the Au(I)‐complex to form [Au x (SR) x ‐COOH] − species in the alkaline condition, which acts as the active precursors in the 2 e − hopping cluster‐size evolution process. Lastly, as a conceptual extension of the mechanistic studies of the CO‐reduction system, a similar intermolecular reaction mechanism is proposed for the 2 e − reduction in the conventional “NaBH 4 reduction” system.