Techniques to control the chemical compositions and geometric structures of alloy clusters are indispensable to understand the correlation between the structures and physical/chemical properties of alloy clusters. In this study, we established a method to separate thiolate-protected 25-atom gold-silver alloy clusters (AuAg (SR)) according to their chemical composition and structural isomer. Furthermore, using this method, we revealed that an isomeric distribution of the products exists in AuAg (SR) ( x ≥ 2) and that the distribution of these isomers depends on the synthesis method and standing time in solution. In this study, it was also demonstrated that the continuous discretization of the electronic structure is induced by the Ag substitution. This method can also be used to separate mixtures of [AuM(SR)] (M = Au, Pt, or Pd) and other Au-Ag alloy clusters ([AuAg (SR)] and [AuAg (SR)]). This method is expected to be used to obtain comprehensive knowledge of the structural-property correlation of alloy clusters.

This review summarizes previous studies on high-resolution separation of Aun(SR)m clusters for better understanding the utility of each separation technique.

This study examined the dynamic behavior of butanethiolate ( S C 4 H 9 ) -p r o t e c t e d g o l d − s i l v e r 3 8 -a t o m a l l o y c l u s t e r s ([Au 38−x Ag x (SC 4 H 9 ) 24 ] 0 ) in solution using reversed-phase high-performance liquid chromatography and electrospray ionization mass spectrometry. The results revealed that [Au 38−x Ag x (SC 4 H 9 ) 24 ] 0 synthesized by reacting [Au 38 (SC 4 H 9 ) 24 ] 0 with an Ag(I)−SC 4 H 9 complex, which is the most frequently used method to synthesize gold−silver alloy clusters, continue to undergo intercluster metal exchange even after the distribution of the chemical composition of the clusters looks unchanged in the mass spectrum. The frequency of this intercluster metal exchange in solution varied depending on the standing time in solution and the synthesis method of [Au 38−x Ag x (SC 4 H 9 ) 24 ] 0 . These findings should be taken into consideration in future studies to realize deeper understanding of the physical and chemical properties of thiolate-protected gold−silver alloy clusters in solution.

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Kornberg 4-4-Mercaptobenzoic Acid, p-MBA 102 Au 102 (p-MBA) 44 X 21 HPLC Au n (SR) m Au n-x M x (SR) m 3 1