The self-assemblies of a newly designed star-shaped molecule end-capped with bromine atoms studied by scanning tunneling microscopy

A new star-shaped molecule StOF-Br₃ containing oligofluorenes and halogen atoms (Bromine) has been synthesized and studied by Scanning Tunneling Microscopy (STM) at the highly oriented pyrolytic graphite (HOPG) surface. We have obtained the high-resolution self-assembled STM images, from which the highly ordered and closely packed non-porous arrangements of the StOF-Br₃ molecular selfassemblies at the heptanoic acid/HOPG surface could be observed. The molecular models and selfassembled StOF-Br₃ architectures have been given in the following text. Besides, we have also figured out the surface free energy by the density functional theory (DFT) calculation, which proved that the halogen…halogen interaction was strong enough to stabilize the ordered molecular self-assemblies. This work verifies the existence of bromine…bromine interactions, and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.