Abstract
A new type of gold cluster has been synthesized using the silsesquioxane derivative (cyclopentyl)7Si8O12(CH2)3SH (T8-OSS−SH) to exchange the PPh3 ligands in (PPh3)12Au55Cl6 by T8-OSS−SH quantitatively. This exchange causes several important changes in the physical and chemical behavior of the compound. Owing to the presence of cyclopentyl substituents, the cluster becomes soluble in non-polar solvents such as pentane. The stability of this compound compared with that of the PPh3-protected cluster is considerably higher meaning that decomposition in solution, and even under the high-energetic irradiation in the microscope, is not observed over longer periods of time. The increase in the total diameter from 2.1 to ca. 4.4 nm is probably responsible for these advantageous properties, supported by strong S−Au bonds. The increase in size is also expressed as an increase in the activation energy for electron-tunneling processes through the ligand shells of neighboring clusters in a densely packed pellet. This increase is from 0.16 eV for (PPh3)12Au55Cl6 to 0.26 eV for the T8-OSS−SH-protected cluster.
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