Bonding Structure, Dehydrogenation, and Dimerization of 1,3-C₆H₄ from Decomposition of 1,3-C₆H₄I₂ on Cu(100)

Abstract

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-C 6 H 4 I 2 on Cu(100). At 100 K, the surface species after 1,3-C 6 H 4 I 2 adsorption are found to be 1,3-C 6 H 4 I 2 , C 6 H 4 I, and 1,3-C 6 H 4 . The formation of these adsorbates is dependent on the adsorption sites of 1,3-C 6 H 4 I 2 . 1,3-C 6 H 4 I 2 adsorbed with the ring at a hollow site and parallel to the surface is predicted to be unstable and preferentially leads to CÀI bond dissociation. 1,3-C 6 H 4 , the intermediate from 1,3-C 6 H 4 I 2 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-C 6 H 4 I 2 decomposition on Cu(100), with all of the carbon atoms left on the surface. Dimerization of 1,3-C 6 H 4 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-C 6 H 4 can occur by second-order kinetics before H 2 evolution. Dimerization of 1,3-C 6 H 4 on Cu(100) shows a different intermolecular interaction behavior from those of 1,2-C 6 H 4 and 1,4-C 6 H 4 on copper single crystal surfaces.

Imaging the Bonds of Dehalogenated Benzene Radicals on Cu(111) and Au(111)

“…Benzyne (C 6 H 4 )i somers are important reactive intermediates in organic synthesis, and have been investigated extensively in matrices, [1] but rarely on surfaces. [2] In the gas phase, benzyne isomersa re well understoodb ecause the calculation of their electronic structure was, and still is, important in testing the accuracy of quantum chemical methods. It is well established that the ground state of all three isomersi st he triplet state.…”

“…In other words, the radicalretains its radicalcharacter upon adsorptiono nc opper and other less reactive surfaces with completelyf illed d-bands.L iao et al investigated the bonding structure and thermal chemistry of meta-benzyne on Cu(100) theoretically. [2] For studies of individual molecules by scanning tunneling microscopy (STM), benzynes were produced through dehydrogenation of individual benzene molecules [7,8] and through thermal decomposition of dihalobenzenes. [6,[9][10][11][12][13] Copper cleaves such carbon-halide bonds at temperatures above 175 K. [14] The image of all three benzyne isomers is asingle protrusion in regular STM images at regular scanning voltages.…”

“…One of the unknown parameters is the geometry of the adsorbed reaction intermediates, because they exist only transiently and thus their direct visualization remains a challenge. Benzyne (C 6 H 4 ) isomers are important reactive intermediates in organic synthesis, and have been investigated extensively in matrices, but rarely on surfaces …”

“…Liao et al. investigated the bonding structure and thermal chemistry of meta ‐benzyne on Cu(100) theoretically . For studies of individual molecules by scanning tunneling microscopy (STM), benzynes were produced through dehydrogenation of individual benzene molecules and through thermal decomposition of dihalobenzenes .…”

Thin Organic Layers Grown on the Surface of Iron Particles under High-Energy Ball Milling in the Presence of Polystyrene and Various Surfactants: X-ray Absorption and Photoelectron Spectroscopy Studies

“…Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has become a powerful tool to probe electronic and structural properties of new materials, − adsorbates, thin films, and liquids. ,− The necessary requirement for measuring the NEXAFS spectra as a function of photon energy is the use of synchrotron radiation which provides a monochromatic light source with tunable photon energy and high brilliance. Since its development in the 1980s, NEXAFS spectroscopy has been applied mostly to the materials consisting of low- Z molecules and atoms such as carbon, nitrogen, oxygen, and fluorine .…”