Golden Opportunity: A Clickable Azide-Functionalized [Au25(SR)18]-Nanocluster Platform for Interfacial Surface Modifications

Ultrasmall atomically precise monolayer-protected gold thiolate nanoclusters are an intensely researched nanomaterial framework, but there is a lack of a system that can be directly synthesized and undergo interfacial surface chemistry. We report an [Au₂₅(SCH₂CH₂-p-C₆H₄-N₃)₁₈]^- nanocluster platform with azide moieties appended onto each surface ligand. The structure of this surface reactive cluster has been confirmed by single-crystal X-ray crystallography, mass spectrometry and UV-Vis, IR and NMR spectroscopies. We show that all surface azide moieties are amenable to cluster-surface strain-promoted alkyne-azide cycloaddition (CS-SPAAC) chemistry with a strained cyclooctyne, opening this as a new platform to allow functional, post-assembly surface modifications to this very prominent nanocluster.