Adsorption and Assembly of Photoelectronic TiOPc Molecules on Coinage Metal Surfaces

The adsorption and assembly of individual and submonolayered TiOPc on Ag(111), Cu(111), and Au(111) have been investigated by scanning tunneling microscopy (STM) and spectroscopy. High resolution STM imaging as well as dI/dV and I–z measurements reveal that TiOPc adsorbed on Ag(111) adopts either O-up or O-down configuration. An intermolecular dipole–dipole interaction leads to the fact that neighboring TiOPc molecules in alternating O-up and O-down configurations form a highly ordered checkerboard assembly structure on Ag(111). However, no large size TiOPc assemblies are observed on Cu(111) and Au(111) due to low surface mobility and diffusivity caused by strong TiOPc–Cu(111) interaction and the templating effect by the reconstructed herringbone structure of Au(111), respectively. Instead, molecular dimers on both Au(111) and Cu(111) as well as molecular aggregates on Au(111) are routinely observed in experiments, indicating that the intermolecular dipole–dipole attraction and weak hydrogen bonding copla...