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

Abstract

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 self-assemblies at the heptanoic acid/HOPG surface could be observed. The molecular models and self-assembled 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.