The fast metal exchange reaction between Au₃₈ and Ag_xAu_38−x nanoclusters in solution at −20 °C has been studied by in situ X-ray absorption spectroscopy (time resolved quick XAFS) in transmission mode. A cell was designed for this purpose consisting of a cooling system, remote injection and mixing devices. The capability of the set-up is demonstrated for second and minute time scale measurements of the metal exchange reaction upon mixing Au₃₈/toluene and Ag_xAu_38−x/toluene solutions at both Ag K-edge and Au L₃-edge. It has been proposed that the exchange of gold and silver atoms between the clusters occurs via the SR(-M-SR)_n (n = 1, 2; M = Au, Ag) staple units in the surface of the reacting clusters during their collision. However, at no point during the reaction (before, during, after) evidence is found for cationic silver atoms within the staples. This means that either the exchange occurs directly between the cores of the involved clusters or the residence time of the silver atoms in the staples is very short in a mechanism involving the metal exchange within the staples.

A CuAu₃₈ bimetallic nanocluster was synthesized by adding a single copper atom to the Au₃₈(2-PET)₂₄ nanocluster. The absence of Cu_xAu₃₈(2-PET)₂₄ doped species was demonstrated by MALDI-TOF mass spectrometry. A separation of bimetallic clusters was attained for the first time where isomers of the E2 enantiomer of the Au₃₈Cu₁(2-PET)₂₄ adduct were successfully isolated from their parent cluster using chiral HPLC. The CD of the isolated isomers revealed a change in their electronic structure upon copper addition. The luminescence of the Au₃₈Cu₁ adduct is significantly enhanced in comparison with the parent Au₃₈ nanocluster. The stability of the newly formed adduct is strongly dependent on the coexistence of the Au₃₈ nanoclusters.

Multiple Ag atoms were doped inside Au₃₈(SCH₂CH₂Ph)₂₄ nanoclusters using the metal exchange method for the first time for the synthesis of Ag_xAu_38–x(SCH₂CH₂Ph)₂₄. MALDI-TOF mass spectrometry revealed the time dependence of the synthesis. Cluster species with different numbers of Ag atoms (different x values) migrate differently on a chromatography (HPLC) column, which allows one to isolate cluster samples with a narrowed distribution of exchanged metal atoms. The enantiomers of selected Ag_xAu_38–x(SCH₂CH₂Ph)₂₄ samples (average x = 6.5 and 7.9) have been separated by HPLC. Doping changes the electronic structure, as is evidenced by the significantly different CD spectra. UV–vis spectra of the doped sample also show diminished features. The temperature required for complete racemization follows Au38 > Ag_xAu_38–x (x = 6.5) > Ag_xAu_38–x (x = 7.9). To our surprise, the racemization of Ag_xAu_38–x(SCH₂CH₂Ph)₂₄ (x = 7.9) occurred even at 20 °C. Racemization involves a rearrangement of the staple motifs at the cluster surface. The results therefore show an increased flexibility of the cluster with increasing silver content. The weaker Ag–S bonds compared to Au–S are proposed to be at the origin of this observation. The experimentally determined activation energy for the racemization is ca. 21.5 kcal/mol (x = 6.5) and 19.5 kcal/mol (x = 7.9), compared to 29.5 kcal/mol for Au₃₈(SCH₂CH₂Ph)₂₄, suggesting no complete metal–S bond breaking in the process.

A fast redistribution of metal atoms occurs upon mixing the Ag_xAu_38−x and Au₃₈ nanoclusters in solution, as observed by mass spectrometry. Physical separation of Ag_xAu_38−x and Au₃₈ species by a dialysis membrane prohibits the metal migration, which suggests that collisions between the reacting clusters are at the origin of the observation.

The location of the Pd atoms in Pd₂Au₃₆(SC₂H₄Ph)₂₄, is studied both experimentally and theoretically. X-ray photoelectron spectroscopy (XPS) indicates oxidized Pd atoms. Palladium K-edge extended X-ray absorption fine-structure (EXAFS) data clearly show Pd-S bonds, which is supported by far infrared spectroscopy. By comparing theoretical EXAFS spectra in R space and circular dichroism spectra of the staple, surface and core doped structures with experimental spectra.

We investigate the distinctly different interaction of thiolate-protected cluster Au₃₈(SC₂H₄Ph)₂₄with two diverse support materials Al₂O₃ and CeO₂. The catalytic surfaces have been heated in different atmospheres, and the removal of the thiolate ligands has been studied. Thermogravimetry (TG), temperature-programmed process coupled with mass spectrometer (TPRDO-MS), and X-ray absorption spectroscopy (XAFS) studies were performed to understand the desorption of thiol ligands depending on conditions and support material. Depending on the atmosphere and the support material the fate of the thiol ligands is different upon heating, leading to metallic Au in the case of Al₂O₃ and to cationic Au with CeO₂. The thiolate removal seems to be a two-step procedure. The catalytic activity of these Au₃₈-supported clusters was studied for the aerobic oxidation of cyclohexane. Conversion was higher for the gold clusters supported on CeO₂. Surprisingly, a significant amount of cyclohexanethiol was found, revealing the active participation of the thiolate ligand in catalytic reactions. The observation also indicates that breaking and formation of C–S bonds can be catalyzed by the gold clusters.

Pd₂Au₃₆(SC₂H₄Ph)₂₄ clusters have been prepared, isolated and separated in their enantiomers. Compared to the parent Au₃₈(SC₂H₄Ph)₂₄ cluster the doping leads to a significant change of the circular dichrosim spectrum, however, the anisotropy factors are of similar magnitude in both cases. Isolation of the enantiomers allowed us to study the racemi-zation of the chiral cluster, which reflects the flexibility of the ligand shell composed of staple motifs. The doping leads to a substantial lowering of the racemization temperature. The change in activation parameters due to the doping may be solely due to modification of the electronic structure.