Structure and distribution of S-α-(1-naphthyl)-ethylamine on Pd(111)

The adsorption geometry of S-α-(1-naphthyl)-ethylamine (NEA) on Pd(111) was studied by scanning tunneling microscopy (STM), STM image simulations, and Monte Carlo (MC) simulations. The comparison of the experimental images with STM image simulations based on DFT calculations indicated a good correspondence with a dibridge[7] adsorption geometry. Furthermore, two different exo- and endo-conformers of the molecule were found on the surface that were related to different orientations of the ethylamine group with respect to the naphthyl group, due to the steric constraint imposed by the surface. It was found that the exo-NEA conformer occurs slightly more often than the endo-conformer, accounting for ∼57 ± 3% of the adsorbed NEA. The distribution and coverage of NEA molecules on the surface was compared to MC simulations of random deposition, where it was found that the ratio of exo- to endo-conformer was related to the different packing densities.