CH2CHCH: A Key Isomer of Propyne. Adsorption Structures and IR Spectra on Cu(111)

We have studied the adsorption properties of a propyne isomer, CH2CHCH, on the Cu(111) surface by means of the generalized gradient approach of the density functional theory using periodic slab models. This isomer was proposed as the key isomer in the catalytic coupling of propyne to yield benzene on this surface, but no experimental information is available for this system. We have determined the most favorable adsorption sites for cis and trans CH2CHCH isomers. The chemisorption is via both terminal carbon atoms for the cis structure while it is monocoordinate for the trans structure. All adsorbed CH2CHCH structures are more stable than gas phase propyne and less stable than adsorbed propyne. We have studied different unit cells to analyze the effect of coverage, which is determinant for the most stable species on the surface. The simulation of the vibrational spectra has permitted us to find the fingerprints of these structures in order to characterize them on this surface.