Nature of Binding in Planar Halogen-Benzene Assemblies and Their Possible Visualization in Scanning Probe Microscopy
Abstrakt
High-resolution scanning probe imaging of molecular structures on surfaces with functionalized tips provided the unprecedented spatial resolution. However, the origin of sharp intermolecular features often presented in high-resolution images of molecular assemblies is still under intensive debate.
Originally, such features were considered as a direct observation of weak noncovalent bonds between molecules. Nevertheless, this interpretation was challenged and ascribed to an experimental artifact.
To address this long-standing controversy, we provided theoretical analysis of intermolecular interaction and high-resolution imaging of halogen-substituted benzene assemblies deposited on metallic substrates, which were extensively studied experimentally. First, we show that formation of molecular assemblies made of C6Br6 and C6F6 on surfaces is driven by interplay between halogen and dispersive interaction.
Next, for the C6Br6 and C6F6 assemblies on surface we analyze simulated high-resolution inelastic electron tunneling spectroscopy (JETS) and atomic force microscopy (AFM) images acquired with a CO-tip. Very good agreement with the experimental evidence allows us to unambiguously determine that the lateral bending of CO-tip due to Pauli repulsion is responsible for the intermolecular sharp edges.
In addition, we discuss, why such sharp features should not be interpreted as the direct evidence of the signature of weak noncovalent bonds.