Mechanism governing the formation of atomically precise dithiolate-protected gold nanoclusters

Atomically precise metal nanoclusters (NCs) stabilized by organic ligands are promising functional materials in various fields owing to their unique geometric and electronic structures. However, many such NCs exhibit insufficient stability, e.g., processes such as alloying can induce structural destabilization. Gold (Au) NCs can be protected by introducing multi-site thiolates (SR), which form exceptionally strong Au-S bonds, thus enhancing the stability of the NCs and expanding their practical applicability. However, multi-site SR protection using bidentate ligands often leads to undesirable polymerization due to inter-NC cross-linking. The present study addresses this issue by elucidating the mechanism governing the formation of Au NCs co-protected by both bidentate (SR'S) and monodentate (SR) ligands. The key impacts of ligand flexibility and site-specific exchange kinetics are identified, thereby providing crucial insights to support the strategic design and synthesis of stable, multi-site SR-protected Au NCs with rigid, well-defined architectures.