High-performance liquid chromatography mass spectrometry of gold and alloy clusters protected by hydrophilic thiolates

Abstract

In this work, we found two hydrophilic interaction liquid chromatography (HILIC) columns for high-performance liquid chromatography (HPLC) suitable for the high-resolution separation of hydrophilic metal clusters. The mass distributions of the product mixtures of hydrophilic metal clusters were evaluated via HPLC mass spectrometry (LC/MS) using these HILIC columns. Consequently, we observed multiple clusters that had not been previously reported for glutathionate (SG)-protected gold clusters (Au(SG)). Additionally, we demonstrated that AuM(SG) alloy clusters (M = Ag, Cu, or Pd) in which part of the Au in the Au(SG) cluster is replaced by a heteroelement can be synthesized, similar to the case of hydrophobic alloy clusters. It is easy to evaluate the mass distributions of hydrophilic metal clusters using this method. Thus, remarkable progress in the synthesis techniques of hydrophilic metal clusters through the use of this method is anticipated, as is the situation for hydrophobic metal 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.…”

“…In particular, there are currently few examples of alloy cluster synthesis. 131,134,172,232,330,348,356,551,667,682,690,694,780 The reason for the limited number of examples of syntheses of hydrophilic metal clusters may be explained by the complexity involved in evaluating the mass distributions of product mixtures. For example, MALDI mass spectrometry and ESI mass spectrometry have been used to evaluate the products of hydrophobic metal cluster synthesis; however, in both cases, the resulting mass spectrum is comparatively simple.…”

“…Therefore, ESI mass spectrometry has been mainly used to evaluate the mass distribution of these mixtures. 22,25,48,64,151,156,168,169,181,201,215,224,270,277,288,289,308,309,330332,339,348,356364,439,465,499,500,502,508,514,516,517,623,667,669,682,686689,749,770,776778 Unfortunately, the ESI mass spectra of hydrophilic metal clusters show a series of polyvalent ions. Thus, the mass spectrum of the product mixture of a hydrophilic metal cluster is complex.…”

Elucidation of the Fundamental Properties of Thiolate-protected Metal Clusters by HPLC

“…Comparison of experimental methods (a) PAGE and ESI mass spectrometry, (b) ion-pair reversed-phase HPLC and ESI mass spectrometry, and (c) HILIC and ESI mass spectrometry (Section 3 3). Adapted from ref 44…”