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  • 1
    Electronic Resource
    Electronic Resource
    Clusters on Clusters: closo-Dodecaborate as a Ligand for Au55 Clusters (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2051-2055 
    Details
    ISSN: 1434-1948
    Keywords: Gold clusters ; closo-Dodecaborate ; Conductivity ; Charging energy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exchange of PPh3 in Au55(PPh3)12Cl6 by Na2[B12H11SH] using a phase-transfer reaction from CH2Cl2 to water needs 6 weeks for reaction, but finally results in the quantitative formation of Au55[(B12H11SH)Na2]12Cl6 (2). Cluster 2, which is of considerable stability in aqueous solution, has been characterized by 1H-NMR, 11B-NMR, and IR spectroscopy as well as by transmission electron microscopy (TEM). The Na+ cations can be exchanged by (octyl)4N+ making the resulting cluster 4 soluble in polar organic solvents. The electrical properties of 2 and 4 are compared with those of Au55[Ph2PC6H4SO3N(octyl)4]12Cl6 (3), the ammonium derivative of the sodium salt. Cluster 3 shows the expected increase of activation energy in the temperature range of 130-250 K owing to the increase of cluster spacing compared with the sodium derivative. However, clusters 2 and 4, show electromigration in the electric field, caused by the huge amount of ionic charges in the ligand shell.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Silsesquioxanes as Ligands for Gold Clusters (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 813-817 
    Details
    ISSN: 1434-1948
    Keywords: Silsesquioxanes ; Gold clusters ; Self assembly ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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