Molecular gold clusters

Attention has been given to the synthesis of bimetallic silver-gold clusters [71] due to their effective catalytic properties, resistance to poisoning, and selectivity [72]. Recently molecular materials with gold and silver nanoclusters and nanowires have been synthesized. These materials are considered to be good candidates for electronic nanodevices and biosensors [73]. 

Bravo-Perez, G., Garzon, I.L. and Novaro, O. (1999) Ab initio study of small gold clusters. Journal of Molecular Structure THEOCHEM, 493, 225-231. 

Rousseau, R. and Marx, D. (2000) The interaction of gold clusters with methanol molecules Ab initio molecular dynamics ofAUn CH3OH and AunCH30H./owmn of Chemical Physics, 112, 761-769. 

Soule de Bas, B., Ford, M.J. and Cortie, M.B. (2006) Melting in small gold clusters a Density Functional molecular dynamics study. Journal of Physics -Condensed Matter, 18, 55-74. 

Molecular-dynamics simulations also showed that spherical gold clusters is stable in the form of FCC crystal structure in a size range of = 13-555 [191]. This is more likely a key factor in developing extremely high catalytic activity on reducible Ti02 as a support material. Thus, it controls the electronic structure of Au nanoparticles (e.g. band gap and BE shift of Au 4f7/2 band) and thereby the catalytic activity. 

D. Touboul, F. Halgand, A. Brunelle, R. Kersting, E. Tallarek, B. Hagenhooo and O. Laprevote, Tissue molecular ion imaging by gold cluster ion bombardment, Analytical Chemistry, 76, 1550 1559(2004). 

We have recently synthesized monodisperse hexanethiolate-protected gold clusters, AU144-C6S, and determined an average core diameter of 1.7 0.3 nm, in support of the estimated molecular formula Au144-(C6H11S)52 (Fig. 30b) [334],... 

B. Yoon, H. Hakkinen, and U. Landman, Interaction of O2 with gold clusters molecular and dissociative adsorption, J. Phys. Chem. A 107,4066-4071 (2003). 

Francium, binary carbide not reported, 11 210 Franck-Condon effect, 16 69 energy, 21 180, 188, 189 envelopes, 16 80, 89, 90 hot bands, 16 90 factors, 32 47 principle, 21 179, 181 vibronic replica, 35 370 frd redon, 38 412, 414 Freeze quench EPR spectroscopy (FQ-EPR), CODH/ACS, 47 318 Fremy s salt, 33 106 Friedel-Crafts reaction, 17 194 cyclophosphazene, 21 65, 66 Frontier molecular orbitals, heteronuclear gold cluster compounds, 39 378-381 Frozen solutions, MOssbauer spectra in studies of, 15 101-103... 

NMR spectra heteronuclear gold cluster compounds, 39 345-348 Phalaris canariensis esophageal cancer, 36 144-145 scanning proton microprobe, 36 149 structural motifs of silicas, 36 146 Pharmaceuticals, 18 177 Phase transitions, in chalcogenide halide compounds, 23 332, 408, 412 [PhCHjMejNAlHjlj, 41 225-226 [(PhCH2)jNLi]3 molecular structure, 37 94, 96 in solution, 37 107-108... 

A short summary and a discussion of the question of where the boundary between molecular and metallic behavior lies for gold clusters and cluster compounds are given in Sect. 6. 

For each cluster size, the few lowest energy equilibrium isomers with molecular adsorption (MA) and two atoms adsorption (TAA) complexes are represented in Fig 8. Most of these structures are planar or near planar. For 4c, 5b, and 5d, only an O atom is not in the plane. Two atom adsorption leads to major structural changes in the gold cluster, particularly for n>5. For example, in the structures 5a, 6a, and 7a, a gold atom breaks the bonds to other Au atoms to form a highly stable linear O-Au-0 unit which bind each 0 atom to one of the remaining Au atoms. On the other hand, molecular adsorption induces only a modest relaxation in the host cluster, and the O2 molecule is attached on top of a Au atom preferably to the bridge position between two Au atoms. 

Gold is one of the least reactive metals in bulk form. However, in recent years a considerable amount of theoretical and experimental works have studied the reactivity of small neutral and charged Au clusters towards different molecules, like H2, O2, CO, and organic radicals " . The reactivity depends on the size and charge state of the cluster. In the previous section we have studied the reactivity towards oxygen adsorption of anionic silver and gold clusters. In this section we study the reactivity of neutral gold clusters towards molecular O2 (subsection 6.1) and CO (subsection 6.2). 

Several reviews of the chemistry ofheteronuclear gold clusters are available and the reader is referred to these works for earlier studies in the field [23-27]. Since the number of well structurally characterized compounds is quite large, this section will be focused only on the structures of basic compounds as well as the most recent results on molecular compounds containing Au-transition metal bonds or interactions. In many cases analogous compounds are available for the metals belonging to the same group and therefore, when appropriate, the common structural patterns will be presented for... 

Touboul D, Halgand F, Brunelle A, Kersting R, Tallarek E, Hagenhoff B, Laprevote O (2004) Tissue molecular ion imaging by gold cluster ion bombardment. Anal Chem 76 1550-1559. doi 10.1021/ac... 

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