NEAR-EDGE X-RAY-ABSORPTION FINE-STRUCTURE STUDY OF BENZENE ADSORBED ON METAL-SURFACES - COMPARISON TO BENZENE CLUSTER COMPLEXES

Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has be en used to study benzene adsorbed on several close-packed metal surfac es [Au(111), Rh(111), Pt(111), and Ru(0001)] under the same experiment al conditions. The NEXAFS spectra reveal significant differences with regard to the shapes and positions of resonances and the dichroism obs erved for the resonance intensities. These differences correlate direc tly with the binding energy and can be attributed to differences in th e electronic coupling of the benzene molecule to the substrate and to adsorption induced changes in the molecular structure of the benzene m olecule. A comparison to the NEXAFS spectra recorded for the benzene m etal cluster complexes [Ru(eta(6)-C6H6)(CH3CN)(3)](2+) and Ru3(CO)(9)( mu(3):eta(2) eta(2) eta(2)-C6H6) indicates that the mu(3)-arene comple x, where the benzene ring is bonded to three metal atoms, can be regar ded as a reasonable cluster analog for the adsorption of benzene on th e Ru(0001) transition metal surface. (C) 1998 American Vacuum Society.