Self-Organized Overlayers Formed by Alanine on Cu{311} Surfaces

Chirality can manifest itself in diverse ways when a molecule adsorbs on a metal surface. A clear understanding of the interplay between molecular chirality, “footprint chirality”, and chirality in the long-range self-organization is crucial if metal surfaces are to be exploited for enantioselective heterogeneous catalysis or enantio-discriminating sensors. We have investigated the self-organization of l-alanine adsorbed as alaninate on Cu{311}, using reflection–absorption infrared spectroscopy in conjunction with first-principles calculations to determine bonding configurations, and low-energy electron diffraction and scanning tunnelling microscopy to elucidate structural features. Three ordered structures are seen. One has a symmetric lattice and 3-point adsorbate bonding (the “symmetric lattice” or SL phase); the others, occurring at higher coverage, have chiral lattices and also involve 2-point bonding (the “chiral lattice” or CL phase). Possible models for these structures are discussed, together wit...