Structure determination of a metastable Au-22(SAdm)(16) nanocluster and its spontaneous transformation into Au-21(SAdm)(15)

摘要

It is of great interest to investigate the evolution pattern of gold nanoclusters (Au NCs) due to its significance in understanding the growth mechanism and origin of Au NCs. Capture of metastable cluster intermediates is an effective way to meet this demand since they provide valuable information for understanding the conversion pathway of Au NCs. However, it is still challenging to obtain metastable Au NCs, especially thiol-protected Au NCs, and solve their structures. In this work, a metastable thiol-protected gold nanocluster, Au-22(SAdm)(16) (Au-22), was synthesized and its structure was determined by single crystal X-ray diffraction. Au-22 shows a close structure-evolution correlation with Au-21(SAdm)(15) (Au-21). The symmetric Au-10 kernel of Au-21 is twisted by the insertion of an additional Au-SR unit on the motif during its structure evolution into Au-22. The distortion in structures results in significantly distinguishing absorption and emission spectra between Au-22 and Au-21. Noteworthily, the structure correlation between Au-22 and Au-21 was also found experimentally that Au-22 can spontaneously transform into Au-21 due to the metastability of Au-22 in solution. This size conversion process was monitored by time-dependent UV-vis spectroscopy and ESI-MS. Furthermore, the solvent effect on the size conversion process was also investigated. This transformation from Au-22 to Au-21 provides a unique platform for studies on the evolution pattern of gold nanoclusters at the single atom level.