Insights into the synthesis of NHC-stabilized Au nanoclusters through real-time reaction monitoring

Atomically precise gold nanoclusters (AuNCs) are interesting nanomaterials with potential applications in catalysis, bioimaging and optoelectronics. Their compositions and properties are commonly evaluated by various analytical techniques, including UV-vis spectroscopy, NMR spectroscopy, ESI mass spectrometry, and single-crystal X-ray diffraction. While these techniques have provided detailed insights into the structure and properties of nanoclusters, synthetic methods still suffer from a lack of in situ and real-time reaction monitoring methodologies. This limits insight into the mechanism of formation of AuNCs and hinders attempts at optimization. We have demonstrated the utility of HPLC-MS as a monitoring methodology in the synthesis of two NHC-protected gold nanoclusters: [Au13(NHC)9Cl3]2+ and [Au24(NHC)14Cl2H3]3+. Herein we show that HPLC coupled with mass spectrometry and 13C NMR spectroscopy of labelled derivatives enables new insight into critical reaction dynamics of AuNCs synthesis and rapid reaction optimization. HPLC-MS monitoring provides insights into the synthesis of uniquely stable NHC-protected gold nanoclusters with applications in catalysis, bioimaging and optoelectronics.

Automated summary

Atomically precise gold nanoclusters (AuNCs) are interesting nanomaterials with potential applications in catalysis, bioimaging, and optoelectronics. However, the synthetic methods for AuNCs lack in situ and real-time reaction monitoring, limiting the understanding of their formation mechanisms and hindering optimization. In this study, the utility of HPLC-MS as a monitoring methodology in the synthesis of two NHC-protected gold nanoclusters was demonstrated, providing new insights into the reaction dynamics and rapid optimization.