Effects of surface defects and coadsorbed iodine on the chemistry of alkyl groups on copper surfaces: evidence for a cage effect

Mimicking Aspects of Heterogeneous Catalysis: Generating, Isolating, and Reacting Proposed Surface Intermediates on Single Crystals in Vacuum

“…The tilted orientation for ethyl is consistent with HREELS results for a number of surfaces, and the upright methyl orientation for propyl is based on HREELS results for Cu(111) 66,69,214,245b and IR results for Cu(110). Illustration of the type of thermodynamic cycle used to establish the metal-carbon bond strength (E M-C ) for ethyl groups on metal surfaces (from ref75). The enthalpy change for the surface -hydride elimination reaction (∆H surf ) is established from the difference in the activation energies for the reaction run in both directions.…”

“…Two approaches for using molecular precursors to generate alkyl groups on metal surfaces. I/TPD 140 CH3Cl TPD, 398 UPS, 398 HREELS 398 CH2I2 TPD, 140,236 H/TPD, 140 CD3/TPD 140,236,251 CH3CH2I TPD 75,251 CH3CH2CH2I, CH3CD2CH2I TPD, 75,236,245a IR 245a CH3CHICH3 IR 245a CH3(CH2)3I TPD, 75 is kinetically favored over C-H bond scission (see Table 4). In almost every case, carbon-iodine bond scission occurs at or below 200 K, while C-H bond scission in alkyl groups occurs above 200 K. The net result is selective cleavage of the C-X bond to generate the desired fragment.…”

Bromine atom diffusion on stepped and kinked copper surfaces

“…Some examples exist suggesting that the presence of adsorbed halides can have an important influence on the surface chemistry available to coadsorbed species. In one example, Jenks et al observed that clustering of iodine atoms on Cu(1 1 0) and Cu(1 0 0) surfaces inhibited b-hydride elimination [3]. Recently, bromine clustering has been found to be responsible for inhibiting b-hydride elimination on kinked, high Miller index Cu surfaces [4,5].…”

Long-Range Electronic Interactions at a High Temperature: Bromine Adatom Islands on Cu(111)

“…1(a)] became mobile and aggregated to form islands [ Fig. 1(b)], at 600 K [22,25,26]. We used scanning tunneling spectroscopy to verify the identity of Br adatoms before and after annealing [ Fig.…”