Chiral Reconstruction of a Metal Surface by Adsorption of Racemic Malic Acid

The adsorption of racemic malic acid on Cu(110) has been studied in ultrahigh vacuum (UHV) by means of scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and reflection–absorption infrared spectroscopy (RAIRS). In contrast to enantiopure malic acid, which forms eleven different ordered phases on Cu(110), only four structures are observed for the racemate. Three of them are superpositions of enantiomorphous phases that have not been observed for the pure enantiomers. Only the non-enantiomorphous c(2×4) saturation structure was found for pure enantiomers and for the racemate, but also shows differences at short-range order. This suggests that heterochiral two-dimensional (2D) phases are present in all cases. A restructuring of the copper surface is clearly identified in STM for some phases after careful annealing, causing chirality transfer via the metal substrate.