Phase Separation of Binary Triptycenes by an Iodine Interlayer Film on a Ag(111) Surface.

We report the self-assembly behaviors of two triptycenes (Trip- and Trip-) on metal surfaces without and with an iodine passivation interlayer by combining scanning tunneling microscopy (STM) and density functional theory (DFT) studies. On the Ag(111) surface, Trip- molecules form islands through intermolecular aldehyde-aldehyde hydrogen bonding and π-π stacking of benzene rings. In contrast, Trip- molecules lie flat and dispersed on the surface. The introduction of Trip- molecules can break the ordered assembly of Trip-. Trip- and Trip- molecules will be mixed in a disorderly manner. On the iodine-passivated Ag(111) surface, Trip- molecules form islands of long chains by intermolecular aldehyde-aldehyde hydrogen bonding. Trip- and Trip- molecules will automatically be separated, forming a self-assembled binary monolayer. These results show that the interface can adjust the mixture and separation of two structurally analogous triptycenes.