Self assembly and chirality transfer in d-Alaninol on the Cu(100) surface

Chirality expression modifications occurring for a simple chiral amino-alcohol, D-Alaninol, adsorbed on Cu(100), when passing from low to high molecular coverage, are studied by means of scanning tunneling microscopy (STM) and theoretical modeling. At low coverage, D-Alaninol molecules organize in tetramers that are aligned to Cu(100) unit vectors whereas, increasing the molecular amount on the surface, the interplay of supramolecularity and chirality induces a rotation of the tetramers of 14 degrees with respect to the substrate lattice vectors. This behaviour is analyzed by means of a theoretical approach that combines classical molecular dynamics (MD) and density functional theory (DFT). The force field adopted in MD calculations is parametrized by fitting it to results obtained at DFT level on a single adsorbed alaninol molecule on the Cu(100) surface. The configurations of isolated and surrounded tetramers most sampled by MD are extracted by Principal Component Analysis. Further DFT relaxation with semiempirical dispersion correction (DFT-D) and considering also the possible dehydrogenation of both functional groups of alaninol, give rise to a few structures that are discussed in terms of their energetics and by comparing the resulting simulated STM images with the experimental ones.