Real Space Observation of a Chiral Phase Transition in a Two-Dimensional Organic Layer

1-Nitronaphthalene adsorbs onto Au(111) in a planar manner leading to two-dimensional chirality. The “handedness” of individual molecules is determined by high resolution scanning tunneling microscopy (see picture). At low coverages enantiopure molecular chains are observed. With increasing coverage, molecules with opposite chirality are admixed until at monolayer coverage racemic structures prevail. The chiral phase transition observed is due to an interplay between electrostatic interactions among the molecules and their interaction with the Au(111) surface.