In this study, we successfully synthesized the rod-like [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ] q (q = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ]-(SbF 6 ) and [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ](SbF 6 )(BPh 4 ), respectively. Compared to the previously reported Au 25 coprotected by phosphine and thiolate ligands (i.e., [Au 25 (PPh 3 ) 10 (SR) 5 Cl 2 ] 2+ ), the two new rod-like Au 25 nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au 13 units (sharing a vertex gold atom) and the bridging "Au−Se(S)−Au" motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the "non-superatom" Au 25 nanoclusters, and the changes are different from the previously reported "superatom" Au 25 nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au 25 + nanoclusters and, thus, significantly affects the electronic structure of the "non-superatom" Au 25 nanoclusters. This work offers new insights into the relationship between the properties and the valence of the "non-superatom" gold nanoclusters.

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Knowledge of the molecular formation mechanism of metal nanoclusters is essential for developing chemistry for accurate control over their synthesis. Herein, the "top-down" synthetic process of monodisperse Au13 nanoclusters via HCl etching of polydisperse Aun clusters (15 ≤ n ≤ 65) is traced by a combination of in situ X-ray/UV-vis absorption spectroscopy and time-dependent mass spectrometry. It is revealed experimentally that the HCl-induced synthesis of Au13 is achieved by accurately controlling the etching process with two distinctive steps, in sharp contrast to the traditional thiol-etching mechanism through release of the Au(i) complex. The first step involves the direct fragmentation of the initial larger Aun clusters into metastable intermediate Au8-Au13 smaller clusters. This is a critical step, which allows for the secondary size-growth step of the intermediates toward the atomically monodisperse Au13 clusters via incorporating the reactive Au(i)-Cl species in the solution. Such a secondary-growth pathway is further confirmed by the successful growth of Au13 through reaction of isolated Au11 clusters with AuClPPh3 in the HCl environment. This work addresses the importance of reaction intermediates in guiding the way towards controllable synthesis of metal nanoclusters.

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In this paper, we report a highly stable gold nanocluster co-protected by the selenophenol and 1,5bis(diphenylphosphino)pentane (L 5 for short) ligands, formulated as [Au 11 (L 5 ) 4 (SePh) 2 ] + . The structure of this nanocluster is determined by X-ray crystallography. The L 5 -ligands are in the form of "Au-PPh 2 (CH 2 ) 5 Ph 2 P-Au", similar to the "staple motif" in the Au n (SR) m nanoclusters. The purity of this nanocluster is confirmed by electrospray ionization mass spectrometry (ESI-MS) and the thermogravimetric analysis (TGA). Moreover, we have also systematically investigated the stability of the [Au 11 (L 5 ) 4 (SePh) 2 ] + (Au 11 -Se for short). The resultsshow that Au 11 -Se is significantly more stable than both Au 11 (PPh 3 ) 7 Cl 3 (Au 11 -7 for short) and [Au 11 (PPh 3 ) 8 Cl 2 ] Cl (Au 11 -8 for short), even in the presence of excess thiol (RSH). This work will provide a new opportunity for future wide research on gold nanoclusters.