Fritz-Haber-Institut der Max-Planck-Gesellschaft

Department of Molecular Physics

Spectroscopy and chemistry of metal clusters and cluster complexes

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4th Ringberg meeting
on Molecular Physics
2009


Different binding geometries of CO
bound to small cationic rhodium clusters

Metal Cluster Surface Chemistry

Metal clusters, or even strongly bound clusters in general, are often discussed as models for the surfaces of bulk materials. Obviously this comparison has its limitations, since in a small cluster all or a dominant fraction of the atoms are located on the surface and the number of volume atoms is low. For bulk material, the reverse is generally true. Additionally, the coordination of metal atoms in a cluster can be very different compared to atoms within an extended metal surface and will be usually lower and less symmetric. These effects and cluster-size dependent changes in the electronic properties can lead to unusual chemical properties.


Effect of cluster charge on ν(CO)

We are focusing on reactions of small molecules like CO, O2, NO, or H2 and have, for instance, intensively studied the interaction of carbon monoxide with different transition metal clusters. Here, the detection of a ν(CO) band and its position directly gives information on the adsorption state of the CO molecule (dissociative or molecular, atop or bridging configuration). The gas phase experiments provide reference data on particles with defined charge states to gauge the charging of deposited clusters and can thereby give new insights into mechanisms of catalytic reactions involving electron transfer.

Molecular vs. dissociative adsorption of CO on transition metal clusters

Sc Ti V Cr Mn Fe Co Ni Cu Zn
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
La Hf Ta W Re Os Ir Pt Au Hg
not (yet) investigated dissociative binding molecular, only atop binding molecular, atop and/or bridging
Literature:
Activation of molecular oxygen by anionic gold clusters A. P. Woodham, G. Meijer, and A. Fielicke, Angew. Chem. Int. Ed. 51 (2012) 4444.
Activated Methane on Small Cationic Platinum Clusters D. J. Harding, C. Kerpal, G. Meijer, and A. Fielicke, Angew. Chem. Int. Ed. 51 (2012) 817.
The adsorption of CO on transition metal clusters: A case study of cluster surface chemistry A. Fielicke, P. Gruene, G. Meijer, and D. M. Rayner, Surf. Sci. 603 (2009) 1427.
Controlling the Bonding of CO on Cobalt Clusters by Coadsorption of H2 I. Swart, A. Fielicke, D. M. Rayner, G. Meijer, B. M. Weckhuysen, and F. M. F. de Groot, Angew. Chem. Int. Ed. 46 (2007) 5317.
Gold cluster carbonyls: Saturated adsorption of CO on gold cluster cations, vibrational spectroscopy and implications for their structures A. Fielicke, G. von Helden, G. Meijer, D. B. Pedersen, B. Simard, and D. M. Rayner, J. Am. Chem. Soc. 127 (2005) 8416.
Vibrational Spectroscopy of CO in Gas-phase Rhodium Cluster-CO Complexes A. Fielicke, G. von Helden, G. Meijer, B. Simard, S. Dénommée, and D. M. Rayner, J. Am. Chem. Soc., 125 (2003) 11184.

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Address: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany