Controlling the Structure, Properties and Surface Reactivity of Clickable Azide-Functionalized Au25(SR)18 Nanocluster Platforms Through Regioisomeric Ligand Modifications

To fine-tune structure-property correlations of thiolate-protected gold nanoclusters through post-assembly surface modifications, we report the synthesis of the o, m, and p regioisomeric forms of the anionic azide-functionalized [Au-25(SCH2CH2-C6H4-N-3)(18)](1-) platform. They can undergo cluster-surface strain-promoted alkyne-azide cycloaddition (CS-SPAAC) chemistry with complementary strained-alkynes. Although their optical properties are similar, the electrochemical properties appear to correlate with the position of the azido group. The ability to conduct CS-SPAAC chemistry without altering the parent nanocluster structure is different as the isomeric form of the surface ligand is changed, with the [Au-25(SCH2CH2-p-C6H4-N-3)(18)](1-) isomer having the highest reaction rates, while the [Au-25(SCH2CH2-o-C6H4-N-3)(18)](1-) isomer is not stable following CS-SPAAC. Single-crystal X-ray diffraction provide the molecular structure of the neutral forms of the three regioisomeric clusters, [Au-25(SCH2CH2-o/m/p-C6H4-N-3](0), which illustrates correlated structural features of the central core as the position of the azido moiety is changed.

Automated summary

In this study, we synthesized the o, m, and p regioisomeric forms of the anionic azide-functionalized [Au-25(SCH2CH2-C6H4-N-3)(18)](1-) platform to fine-tune the structure-property correlations of thiolate-protected gold nanoclusters through post-assembly surface modifications. These regioisomers can undergo cluster-surface strain-promoted alkyne-azide cycloaddition (CS-SPAAC) chemistry with complementary strained-alkynes. It was found that the electrochemical properties of the clusters appear to be correlated with the position of the azido group.