Divergent Transformation Pathways from a Common Au₂₅ Intermediate: The Effect of "Positional Isomerism"

Metal nanoclusters (NCs) are emerging at the forefront of nanoscience, offering structure-based tunability due to their precision at the atomic scale. However, the controlled synthesis of the material remains unresolved. Ligand exchange-induced structural transformation (LEIST) provides a powerful strategy for tracking NC transformations and identifying their driving factors, thereby contributing to the rational design of NCs. Herein, we analyze the influence of differences in the ligand substituent position on the transformation of [Au₂₃(CHT)₁₆]^- (CHT = cyclohexanethiol), which has not been systematically explored. Positional isomers of methylbenzenethiols (2-MBT, 3-MBT, and 4-MBT) are used as incoming ligands for LEIST, identifying a common intermediate that diverges into different products. The subtle difference in the ligand has determined the potential pathways for structural growth, as signified by time-dependent mass spectrometry, NMR, and structural analysis. This work provides fundamental insights into the effect of the positional isomerism of ligands, which serves as a traffic controller for the desired synthesis of Au nanoclusters.