Two-dimensional molecular chirality transfer on metal surfaces

The chirality transfer control from a single molecule to the surface molecular superstructures and to the substrate is a challenging and important aspect of two-dimensional chiral nanostructures for tailoring the functionality of molecular––metal interfaces. However, how the chiral transfer takes place still remains an open question. In this paper, we combine data from scanning tunneling microscopy, low-energy electron diffraction and circular dichroism in the angular distribution of valence photoelectrons measurements to interpret the formation of extended chiral self-assembled domains obtained by adsorption of the chiral amino-alcohol alaninol on Cu(100). We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage, whereas a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. This suggests that the reorientation originates from forces acting when tetramers pack together in the self-assembling process. Direct information on the chirality transfer from molecules to the substrate has been obtained by the dichroic behavior of a mixed molecule-copper valence state showing that the presence of molecular chiral domains induces asymmetric interaction with the substrate and locally transfers chiral character to the underlying metal atoms participating in the adsorption process.