Ag₂₀ Nanoclusters with Surface Azides as an Easily Functionalized Platform for Diverse Chemical Applications

Modifying atomically precise nanocluster surfaces while maintaining the cluster core remains a key challenge. Herein, the synthesis, structure, and properties of two targeted Ag₂₀ nanoclusters (NCs) with eight surface azide moieties, [CO₃@Ag₂₀(S^tBu)₁₀(m-N₃-C₆H₄COO)₈(DMF)₄] (1-m) and [CO₃@Ag₂₀(S^tBu)₁₀(p-N₃-C₆H₄COO)₈(DMF)₄] (1-p) are reported, where DMF is N,N-dimethylformamide. These AgNCs are designed to undergo cluster surface strain-promoted azide-alkyne cycloaddition (CS-SPAAC) reactions, introducing new functionality to the cluster surface. Reactivity is screened using model strained cyclooctynes. Reaction products and parent clusters are characterized by UV-vis, FT-IR, and NMR spectroscopies. The structure of the parent clusters and presence of surface azides is confirmed by single crystal X-ray diffraction (SCXRD) analysis. Clusters 1-m and 1-p are found to be amenable to CS-SPAAC reactions with retention of the NC frameworks, opening new routes for efficient modification of AgNC for applications.