Local structure determination of a chiral adsorbate: Alanine on Cu(110)

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(110) in the (3 x 2) phase. The local site is found to be similar to that of glycinate on Cu(110), 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(I 10)(3 x 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 x 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 angstrom. The resulting average N-Cu and O-Cu values are 2.02 and 1.98 angstrom, respectively, with an estimated precision of +/- 0.03 angstrom. These bondlengths are shorter than those obtained from DIFT by 0.08 and 0.10 angstrom, respectively. (c) 2005 Elsevier B.V. All rights reserved.