Chirality transfer by epitaxial mismatch in multi-layered homochiral molecular films

We report the transfer of chirality from enantiomorphous monolayer into thin films. The pure enantiomers of heptahelicene, a helically shaped aromatic molecule, form ordered first layer structures that exhibit enantiomorphism by having opposite tilt angles of the adsorbate lattice with respect to the Cu(1 1 1) lattice of the metal template. The next layers grow on top quasi-epitaxially, but with a small lattice mismatch. This leads to Moiré structures observed via scanning tunneling microscopy. The mismatch differs along the two adsorbate lattice vectors, thus causing a transfer of the oblique tilt angle in the first layer into an apparent tilt angle of the Moiré pattern. The mechanism of this chirality transfer in terms of a detailed structure model is discussed.