Substrate Tumbling in a Chemisorbed Diastereomeric α-Ketoester/1-(1-Naphthyl)ethylamine Complex

Scanning tunneling microscopy (STM) data for alpha-ketoester/1-(1-naphthyl)ethylamine complexes on Pt(111) reveal a tumbling motion that couples two neighboring binding states. The interconversion, resulting in prochiral inversion of the alpha-ketoester, occurs in single complexes without breaking them apart. This is a surprising observation because the overall motion requires rotation of the alpha-ketoester away from the surface without branching exclusively into diffusion away from the complex or desorption. The multi-step interconversion is rationalized in terms of sequences of bound states that combine transient H-bond interactions with the chiral molecule and weakened adsorption interactions with the metal. The observation of tumbling in single long-lived complexes is of relevance to self-assembly and directed molecular motion on surfaces, to ligand-controlled surface reactions, and most directly to stereocontrol in asymmetric heterogeneous catalysis.

Automated summary

Scanning tunneling microscopy (STM) data reveals a tumbling motion in alpha-ketoester/1-(1-naphthyl)ethylamine complexes on Pt(111), where the interconversion of prochiral inversion occurs without breaking apart the complexes. This unexpected observation suggests a rotation of the alpha-ketoester away from the surface, involving transient H-bond interactions and weakened adsorption interactions with the metal. The tumbling motion in long-lived complexes has implications in self-assembly, ligand-controlled surface reactions, and stereocontrol in asymmetric heterogeneous catalysis.