Local structure determination of a chiral adsorbate: Alanine on Cu(1 1 0) |
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Authors: | DI Sayago G Nisbet DP Woodruff |
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Institution: | a Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin, Germany b Centre for Applied Catalysis, Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, United Kingdom c Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom |
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Abstract: | N 1s and O 1s scanned-energy mode photoelectron diffraction (PhD) has been used to investigate the local structure of a single enantiomer of deprotonated alanine, alaninate, NH2CH3CHCOO-, on Cu(1 1 0) in the (3 × 2) phase. The local site is found to be similar to that of glycinate on Cu(1 1 0), with the N atoms in near-atop sites and the O atoms sites consistent with bonding to single surface Cu atoms but substantially off-atop. Unlike the Cu(1 1 0)(3 × 2)pg-glycinate phase, however, in which the two molecular species per unit mesh are mirror images of one another in identical local sites, the intrinsic chirality of l-alaninate means that the two molecules per unit mesh of the (3 × 2) surface phase occupy slightly different local sites. However, an excellent fit to the PhD data can be achieved by a minor modification of the structure found in DFT calculations by R.B. Rankin and D.S. Sholl Surf. Sci. 574 (2005) L1] in which the heights of the N and O atoms above the surface are reduced by approximately 0.1 Å. The resulting average N-Cu and O-Cu values are 2.02 and 1.98 Å, respectively, with an estimated precision of ±0.03 Å. These bondlengths are shorter than those obtained from DFT by 0.08 and 0.10 Å, respectively. |
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Keywords: | Photoelectron diffraction Surface structure Chemisorption Copper Alanine Amino acids |
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