Atomic and Isomeric Separation of Thiolate-Protected Alloy Clusters

Abstract

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.

Atomic-level separation of thiolate-protected metal clusters

“…15A). 212 The optical absorption spectrum of the separated Au 25−x Ag x (SC 4 H 9 ) 18 revealed the correlation between the chemical composition and electronic structure in Au 25−x Ag x (SC 4 H 9 ) 18 (x = 1-4) with atomic accuracy (Fig. 15B).…”

“…15A). 212 The researchers recorded time-dependent mass spectra using LC/MS for Au 25−x Ag x (SC 4 H 9 ) 18 (x = 1-4). They revealed that Au 25−x Ag x (SC 4 H 9 ) 18 (x = 2,3) has different structural isomer distributions depending on the synthesis method and that the isomer distributions vary in solution.…”

“…20 However, there are still many unclear points about the mechanism of the metal exchange reaction. A deep understanding of this mechanism could be obtained if the reaction proceeded using Au n−x Ag x (SR) m clusters isolated with atomic precision 211,212 and the reaction process was tracked using LC/MS. In future studies, the effective use of established separation techniques is expected to provide a deep understanding of the functions and properties of Au n (SR) m and related clusters.…”

Deepening the Understanding of Thiolate-Protected Metal Clusters Using High-Performance Liquid Chromatography

“…A schematic of the equipment used in our research is presented in Figure 4. 3,174,219,231,291294,305,648,682,702,705,706,708,709,727,916,917,947 The equipment is roughly divided into two parts: an HPLC component and a mass analysis component. When the ESI method is used for ionization in mass spectrometry, the chemical composition of clusters at a particular retention time is determined by either of these methods: (i) mass spectrometry of the sample after fractionation (Figure 4(a)) or (ii) mass spectrometry by direct introduction of the sample from the HPLC to the mass spectrometer (LC/MS; Figure 4(b)).…”

“…For clusters separated by these methods, the chemical composition has been determined by mass spectrometry methods, such as electrospray ionization (ESI) 22,24,25,29,32,33,39,43,46,48,5356,5863,65, Simultaneously, we have been actively working on applying HPLC to analysis of these clusters. 3,174,219,231,291294,305,648,682,702,705,706,708,709,727,916,917,947 Using HPLC, we have succeeded in systematically isolating a series of SR-protected gold clusters (Au n (SR) m ) and their heteroatom-substituted clusters (Au n¹x M x (SR) m or Au n¹x M x (SR 1 ) m¹y (SR 2 ) y ; M = Ag, Cu, 682 Pt, or Pd; hereinafter referred to as alloy clusters). Furthermore, we have gained many new insights into these clusters using HPLC as an analytical tool in addition to studying isolated (separated by HPLC) clusters.…”