Determination of the local structure of glycine adsorbed on Cu(110)

Scanned-energy mode N ls and O ls photoelectron diffraction has been used to determine the local geometry of glycine adsorbed on Cu(110) in an ordered (3x2) phase. The results are consistent with a molecular geometry in which the C-C axis lies approximately parallel to the surface and the molecule bonds across a pair of [<1(1)over bar>0] Cu surface rows through the two oxygen atoms of the carboxyl group and the N atom of the amino group. The N atom is displaced by 0.24+/-0.10 Angstrom off an atop site along the [<1(1)over bar>0] rows with a Cu-N nearest-neighbour distance of 2.04+/-0.02 Angstrom. The carboxyl bonds to two Cu atoms in a [<1(1)over bar>0] row, with the O atoms displaced 0.80+/-0.07 Angstrom from atop in [001] towards the amino group with a Cu-O nearest-neighbour bond length of 2.03+/-0.03 Angstrom and a resulting tilt of the O-Cu bond relative to the surface normal of 23+/-2. A specific structural model comprising two molecular moieties per unit mesh which has the space group plgl, consistent with the qualitative LEED observations, is proposed on the basis of these data. (C) 1998 Elsevier Science B.V.