Bonding Structure, Dehydrogenation, and Dimerization of 1,3-C(6)H(4) from Decomposition of 1,3-C(6)H(4)I(2) on Cu(100)

Temperature-programmed reaction/desorption, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure in combination of calculations based on density functional theory have been employed to investigate adsorption and reaction of 1,3-C6H4I2 on Cu(100). At 100 K, the surface species after 1,3-C6H4I2 adsorption are found to be 1,3-C6H4I2, C6H4I, and 1,3-C6H4. The formation of these adsorbates is dependent on the adsorption sites of 1,3-C6H4I2. 1,3-C6H4I2 adsorbed with the ring at a hollow site and parallel to the surface is predicted to be unstable and preferentially leads to C-I bond dissociation. 1,3-C6H4, the intermediate from 1,3-C6H4I2 decomposition, has a tilted adsorption geometry with a distorted ring. H-2 is the only reaction product observed after 550 K in the 1,3-C6H4I2 decomposition on Cu(100), with all of the carbon atoms left on the surface. Dimerization of 1,3-C6H4 molecules on Cu(100) has been described computationally, showing an activated and exothermic process. With the theoretically obtained activation energy of 28.2 kcal/mol and estimated surface coverages, coupling of 1,3-C6H4 can occur by second-order kinetics before H2 evolution. Dimerization of 1,3-C6H4 on Cu(100) shows a different intermolecular interaction behavior from those of 1,2-C6H4 and 1,4-C6H4 on copper single crystal surfaces.