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

<p class="Abstract" style="margin: 0cm 0cm 30pt; text-align: justify; line-height: 11.25pt; font-size: 8pt; font-family: Arial, sans-serif; color: rgb(0, 0, 0);"><span lang="EN-GB">To fine-tune structure-property correlations of thiolate-protected gold nanoclusters through post-assembly surface modifications, we report the synthesis of the <italic>o</italic>, <italic>m</italic>, and <italic>p</italic> regioisomeric forms of the anionic azide-functionalized [Au25(SCH2CH2-C6H4-N3)18]1- platform. They can undergo cluster-surface strain-promoted alkyne-azide cycloaddition (<italic>CS</italic>-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 <italic>CS</italic>-SPAAC chemistry without altering the parent nanocluster structure is different as the isomeric form of the surface ligand is changed, with the [Au25(SCH2CH2-<italic>p</italic>-C6H4-N3)18]1- isomer having the highest reaction rates, while the [Au25(SCH2CH2-<italic>o</italic>-C6H4-N3)18]1- isomer is not stable following <italic>CS</italic>-SPAAC. Single-crystal X-ray diffraction provide the molecular structure of the neutral forms of the three regioisomeric clusters, [Au25(SCH2CH2-<italic>o</italic>/<italic>m</italic>/<italic>p</italic>-C6H4-N3]0, which illustrates correlated structural features of the central core as the position of the azido moiety is changed.<o:p></o:p></span></p>.