Adsorption, Single-Molecule Manipulation, and Self-Assembly of Borazine on Ag(111)

The interaction of borazine with metal supports and the concomitant surface chemistry play important roles in the synthesis of hexagonal boron nitride and the assembly of BN-doped carbon nanostructures, thus making adsorbed borazine an intriguing model system. Herein, the first real space characterization of individual borazine molecules and highly ordered borazine self-assemblies on solid supports, combining scanning tunneling microscopy (STM), scanning tunneling spectroscopy, X-ray photoelectron spectroscopy, and complementary density functional theory modeling is reported. Specifically, a weak, nondissociative adsorption of borazine with the ring aligned in parallel to the surface plane is observed on Ag(111) upon low temperature deposition. Borazine is found to favor hollow adsorption sites, which guide the assembly of intricate borazine assemblies including a porous, chiral honeycomb-like network, and dense-packed monolayer films. Additionally, a modification of the borazine adsorption configuration by STM-based manipulation is demonstrated. Dehydrogenation of individual molecules by voltages pulses yields an upright standing borazine fragment bound via B to Ag. This study thus provides a comprehensive, single-molecule level characterization of borazine adsorption and surface chemistry on a characteristic coinage metal support and may serve as a reference for advanced low-dimensional materials based on functionalized borazines or including BN units as dopants. Borazine molecules are imaged on a solid support for the first time in real space via low-temperature scanning tunneling microscopy. The intact molecules form a porous and a dense-packed phase. Individual borazine molecules are manipulated with voltage pulses. The manipulation product is identified, in combination with density functional theory calculations, as dehydrogenated and tilted borazine fragment.image