An intermolecular association and decarboxylation mechanism is proposed to understand the experimental evidence of the stepwise 2e− 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 2e−–8e− gold nanoclusters in the CO-directed [Au25(SR)18]− synthesis. With these established reaction equations, atomic pathways of three prototype cluster-size evolution reactions are comprehensively explored in the course of [Au25(SR)18]− synthesis, namely, the conversion of 0e− homoleptic Au(I)-SR complexes to the 2e− intermediate Au15(SR)13 cluster, the size-evolution of 2e− Au15(SR)13 cluster to the 4e−–8e−cluster (stepwise 2e−-hopping), and the isoelectronic addition reaction of [Au23(SR)16]− to the [Au25(SR)18]−. The studies reveal that the CO can combine with the Au(I)-complex to form [Aux(SR)x-COOH]− species in the alkaline condition, which acts as the active precursors in the 2e− 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 2e− reduction in the conventional “NaBH4 reduction” system.
- 2e− hopping, cluster-size evolution reactions
- nucleation mechanisms
- thiolate-gold nanoclusters
ASJC Scopus subject areas
- Materials Science(all)