The bonding and orientation of the amino acid L-alanine on Cu{110} determined by RAIRS

Reflection absorption infrared spectra have been obtained for the amino-acid L-alanine on Cu{110} as a function of exposure at 300 K. The RAIR spectra reveal a complicated set of vibrational bands which can be interpreted with reference to Cu-(ala)(2) complexes. A detailed analysis in terms of the individual functional groups present in the molecule yields a detailed geometry of the adsorbed species. Two chemisorbed phases are identified: a thermodynamically stable phase which forms at low exposures, in which both the carboxylate oxygen atoms are equidistant from the surface, and a second phase, created by diffusion-limited adsorption processes, in which a differently oriented alanine species is accommodated at the surface, possessing tilted carboxylate groups where the two oxygen atoms are no longer equidistant from the surface.