Interactions between Ultrastable Na4Ag44(SR)30 Nanoclusters and Coordinating Solvents: Uncovering the Atomic-scale Mechanism

We report the mechanism on the ultrahigh stability of Na₄Ag₄₄(SR)₃₀ by uncovering how coordinating solvents interact with the Na₄Ag₄₄(SR)₃₀ nanocluster at the atomic scale. Through synchrotron X-ray experiments and theoretical calculations, it was found that strongly coordinating aprotic solvents interact with surface Ag atoms, particularly between ligand bundles, which compresses the Ag core and relaxes surface metal-ligand interactions. Furthermore, water was used as a cosolvent to demonstrate that semi-aqueous conditions play an important role in protecting exposed surface regions and can further influence the local structure of the silver nanocluster itself. Notably, under semi-aqueous conditions, aprotic coordinating solvent molecules preferentially remain on the metal surface while water molecules interact with ligands, and ligand bundling persisted across the varied solvation conditions.