An Atomically Precise Pyrazolate-Protected Copper Nanocluster Exhibiting Exceptional Stability and Catalytic Activity

The synthesis of atomically precise copper nanoclusters (Cu-NCs) with high chemical stability is a prerequisite for practical applications, yet still remains a long-standing challenge. Herein, we have prepared a pyrazolate-protected Cu-NC (Cu8), which exhibited exceptional chemical stability either in solid-state or in solution. The crystals of Cu8 are still suitable for single crystal X-ray diffraction analysis even after being treated with boiling water, 8 wt % H2O2, high concentrated acid (1 M HCl) or saturated base (approximate to 20 M KOH), respectively. More importantly, the structure of Cu8 in solution also remained intact toward oxygen, organic acid (100 eq. HOAc) or base (400 eq. dibutylamine) confirmed by H-1 NMR and UV/Vis analysis. Taking advantage of high alkali-resistant, Cu8 illustrates excellent catalytic activity for the synthesis of indolizines, and it can be reused for at least 10 cycles without losing catalytic performance.

Automated summary

In this study, a pyrazolate-protected copper nanocluster (Cu8) with exceptional chemical stability in both solid-state and solution was successfully synthesized. The crystals of Cu8 remained suitable for single crystal X-ray diffraction analysis after being treated with boiling water, concentrated acid, or base. Furthermore, the structure of Cu8 in solution also remained intact towards oxygen, organic acid, and base as confirmed by H-1 NMR and UV/Vis analysis. Cu8 exhibited excellent catalytic activity for the synthesis of indolizines, and it could be reused for at least 10 cycles without losing catalytic performance.