Methyl on Cu(111) - structural determination including influence of co-adsorbed iodine

The adsorption geometry of the methyl species on Cu(1 1 1) with and without coadsorbed iodine has been determined using scanned energy mode photoelectron diffraction. Under all circumstances the three-fold-coordinated hollow sites are occupied. At saturation coverage of pure methyl species only the ‘fcc' site, directly above a third layer Cu atom is occupied, whereas at half saturation coverage 70% of the methyl species occupy these fcc hollows and 30% occupy the ‘hcp' sites above second layer Cu atoms. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C3v symmetry, but the possibility that the species was tilted on the surface could not be excluded. The height of the C above the surface in a pure methyl layer was 1.66±0.02 A, but was reduced to 1.62±0.02 A in the presence of co-adsorbed iodine, suggesting that iodine may increase the strength of adsorption. Iodine was also found to occupy the fcc hollow sites with a Cu–I bondlength of 2.61±0.02 A.

[1]  R. C. Hewitt,et al.  Adsorption Sites and Bond Lengths of Iodine on Cu{111} and Cu{100} from Surface Extended X-Ray-Absorption Fine Structure , 1980 .

[2]  B. Bent,et al.  CH vibrational mode-softening in alkyl groups bound to Cu(111) , 1992 .

[3]  Angelos Michaelides,et al.  Softened C–H modes of adsorbed methyl and their implications for dehydrogenation: An ab initio study , 2001 .

[4]  T. Chuang,et al.  Vibrational study of CH2 and CH3 radicals on the Cu(111) surface by high resolution electron energy loss spectroscopy , 1998 .

[5]  T. Chuang,et al.  THE SURFACE CHEMISTRY OF METHYL AND METHYLENE RADICALS ADSORBED ON CU(111) , 1999 .

[6]  F. Solymosi,et al.  Spectroscopic study on the adsorption and dissociation of CH3I on Pd(100): thermal and photo effects , 1993 .

[7]  V. Dhanak,et al.  The structure of (√3×√3)R30° iodine on Pd (111) surface studied by normal incidence X-ray standing wavefield absorption , 1999 .

[8]  P. Bailey,et al.  Synthesis and characterisation of magnesium methyl complexes with monoanionic chelating nitrogen donor ligands and their reaction with dioxygen , 2000 .

[9]  J. Yates,et al.  Vibrational studies of CH3I on Si(100)-(2×1): adsorption and decomposition of the methyl species , 1992 .

[10]  D. Truhlar,et al.  Embedded Diatomics-in-Molecules Potential Energy Function for Methyl Radical and Methane on Nickel Surfaces , 1998 .

[11]  D. P. Woodruff,et al.  Investigation of the Cu(111) (√3 × √3)R30°-Cl structure using sexafs and photoelectron diffraction , 1987 .

[12]  A. Jansen,et al.  Electronic structure calculations and dynamics of CC coupling on nickel and cobalt , 1995 .

[13]  X. Zhou,et al.  Surface photochemistry: Monolayer versus multilayer for alkyl halides on Ag{111} , 1990 .

[14]  V. Fritzsche.  Approximations for photoelectron scattering , 1989 .

[15]  D. P. Woodruff,et al.  A photoelectron diffraction study of the structure of PF3 adsorbed on Ni{111} , 1992 .

[16]  X. Zhou,et al.  Alkyl halide photochemistry on Ag(111): II. Methyl bromide , 1991 .

[17]  B. Bent,et al.  Methyl radical adsorption on Cu(111): Bonding, reactivity, and the effect of coadsorbed iodine , 1992 .

[18]  Alexander M. Bradshaw,et al.  The wavelength dependence of the photodissociation cross-section of CH3Br chemisorbed on Cu{111} , 1993 .

[19]  X. Zhou,et al.  Interactions of methyl halides (Cl, Br and I) with Ag(111) , 1989 .

[20]  A. Michaelides,et al.  Methyl chemisorption on Ni(111) and C-H-M multicentre bonding : a density functional theory study , 1999 .

[21]  D. P. Woodruff,et al.  Structural determination of the Cu(111) -(√3 × √3) R30°-ClBr surface using the normal incidence X-ray standing wave method , 1995 .

[22]  F. Solymosi,et al.  Thermal stability of the methyl group adsorbed on the palladium(100) surface , 1991 .

[23]  J. Demuth,et al.  Elastic leed intensity-energy studies of clean (001), (110) and (111) nickel surfaces , 1974 .

[24]  R. C. Hewitt,et al.  Sexafs studies of iodine adsorbed on single crystal substrates , 1979 .

[25]  Schindler,et al.  Direct adsorbate-structure determination by scanned-energy-mode photoelectron diffraction. , 1993, Physical review. B, Condensed matter.

[26]  V. Kokozay,et al.  Direct synthesis and crystal structure of tetrameric copper(I) iodide with trimethylamine [CuI(NMe3)]4 , 1997 .

[27]  Hong Yang,et al.  Ab initio chemisorption studies of methyl on nickel(111) , 1991 .

[28]  H. Hoffmann,et al.  Detection of chemisorbed methyl and methylene groups : surface chemistry of methyl iodide on Pt(111) , 1991 .

[29]  D. King,et al.  A tensor LEED structural study of the coverage-dependent bonding of iodine adsorbed on Rh{111} , 1993 .

[30]  I. Harrison,et al.  Photofragmentation dynamics of submonolayers of CH3Br adsorbed on Pt(111) , 1992 .

[31]  F. Solymosi,et al.  Surface photochemistry: Adsorption and dissociation of CH3Cl on clean and K‐promoted Pd(100) surfaces , 1991 .

[32]  D. P. Woodruff,et al.  Direct identification of atomic and molecular adsorption sites using photoelectron diffraction , 1994, Nature.

[33]  Schindler,et al.  Structure determination for coadsorbed molecular fragments using chemical shift photoelectron diffraction. , 1993, Physical review letters.

[34]  A. Bradshaw,et al.  Photoreactions of adsorbed CH3Br on Pt(111) , 1990 .

[35]  J. White,et al.  Surface photochemistry. IX. Photochemistry of small molecules on metal surfaces , 1989 .

[36]  George H. Smudde,et al.  A methyl free radical source for use in surface studies , 1992 .

[37]  J. Hafner,et al.  A theoretical study of CHx chemisorption on the Ru(0001) surface , 1999 .

[38]  V. Dhanak,et al.  Structural studies of the ( 3× 3) R 30° surfaces of chlorine and iodine on Rh (111) , 1999 .

[39]  J. Yates,et al.  The direct observation of hindered rotation of a chemisorbed molecule: PF3 on Ni(111) , 1987 .

[40]  Jones,et al.  Simple x-ray standing-wave technique and its application to the investigation of the Cu(111) ( sqrt 3 sqrt 3 )R30 degrees -Cl structure. , 1987, Physical review letters.

[41]  D. P. Woodruff,et al.  The local adsorption geometry of CH3 and NH3 on Cu(111): a density functional theory study , 2002 .

[42]  R. Renaud,et al.  SYNTHESIS OF 1,2-DIALKYLHYDRAZINES AND THE CORRESPONDING AZOALKANES , 1954 .

[43]  Jens R. Rostrup-Nielsen,et al.  Theoretical Studies of Stability and Reactivity of CHx Species on Ni(111) , 2000 .

[44]  van Ra Rutger Santen,et al.  The adsorption of methyl on Rh10 clusters: selective C–H bond weakening , 1999 .

[45]  M. B. Lee,et al.  Activated dissociative chemisorption of CH4 on Ni(111): Observation of a methyl radical and implication for the pressure gap in catalysis , 1986 .

[46]  D. P. Woodruff,et al.  Adsorbate structure determination on surfaces using photoelectron diffraction , 1994 .

[47]  V. Fritzsche.  A new spherical-wave approximation for photoelectron diffraction, EXAFS and MEED , 1990 .

[48]  D. P. Woodruff,et al.  Structure determination of ammonia on Cu(110) — a low-symmetry adsorption site , 1997 .