Temperature-Triggered Sequential On-Surface Synthesis of One and Two Covalently Bonded Porous Organic Nanoarchitectures on Au(111)

Abstract

Subtle variations of surface temperature can drastically influence the on-surface synthesis of two-dimensional covalent graphene nanoarchitectures. The structure of the engineered nanoarchitectures not only results from the temperature-activation of the catalytic process, but it is also governed by the temperature-dependent geometry of intermolecular assembly. The sequential engineering of porous organic nanoarchitectures based on the covalent Ullmann coupling of star-shaped 1,3,5-tris(3,5-dibromophenyl)benzene molecules on Au(111) in vacuum is investigated using scanning tunneling microscopy and X-ray photoemission spectroscopy. This molecule can form one-covalent-bond or two-covalent-bonds with neighboring molecules. At room temperature, the molecules self-assemble into a porous halogen-bonded network stabilized by two types of X3 synthons. One-covalent-bond dimers appear on the surface after annealing at 145 °C. One-covalent-bond chains are created after annealing at 170 °C. Most of the molecules are b...