Staudinger Reactions on Azide Functionalized Au25 Nanoclusters as a Route to Linked Frameworks

Sung Kyun Lim, The University of Western Ontario

Abstract

Azide-functionalized [Au₂₅(SR)₁₈] gold nanoclusters [Au₂₅(SCH₂CH₂C₆H₄-N₃)₁₈]^- are able to undergo post-assembly surface modification via click reaction chemistry. In this study, we report the reaction of the azide cluster, (Oct₄N)[Au₂₅(SCH₂CH₂-p-C₆H₄N₃)₁₈] (AuNC-azide) with triarylphosphine bidentates. The -N3 groups on AuNC-azide undergo Staudinger reactions with PPh₃, yielding surface -C₆H₄N=PPh₃ at room temperature under inert atmosphere: this reaction is quite selective towards formation of -C₆H₄N=PPh₃ when using up to 14 equivalents of PPh₃. However, when a greater number of equivalents of triphenylphosphine is used, surface displacement of thiolate ligands also occurred in competition with the Staudinger reaction. Reactions of AuNC-azide with the bidentate phosphine ligand 4,4’-Ph₂PC₆H₄-C₆H₄PPh₂ leads to covalent linking of the gold clusters via intermolecular -C₆H₄-N=PPh₂C₆H₄-C₆H₄Ph₂P=N-C₆H₄- bridges to form networks of clusters.