Selective Adsorption of a Supramolecular Structure on Flat and Stepped Gold Surfaces

TL;DR

This study uses density functional theory to analyze how 2,6-dibromoanthraquinone molecules adsorb on flat and stepped gold surfaces, revealing preferred binding sites and the role of intermolecular interactions in stabilizing molecular layers.

Contribution

It provides detailed insights into adsorption geometries and energies on high-index gold surfaces, advancing understanding of supramolecular assembly on complex metal surfaces.

Findings

Bridge sites are preferred on flat surfaces.

Step edges are preferred on stepped surfaces.

Van der Waals and intermolecular interactions stabilize 2D networks.

Abstract

Halogenated aromatic molecules assemble on surfaces forming both hydrogen and halogen bonds. Even though these systems have been intensively studied on flat metal surfaces, high-index vicinal surfaces remain challenging, as they may induce complex adsorbate structures. The adsorption of 2,6-dibromoanthraquinone (2,6-DBAQ) on flat and stepped gold surfaces is studied by means of van der Waals corrected density functional theory. Equilibrium geometries and corresponding adsorption energies are systematically investigated for various different adsorption configurations.~It is shown that bridge sites and step edges are the preferred adsorption sites for single molecules on flat and stepped surfaces, respectively. The role of van der Waals interactions, halogen bonds and hydrogen bonds are explored for a monolayer coverage of 2,6-DBAQ molecules, revealing that molecular flexibility and intermolecular interactions stabilize two-dimensional networks on both flat and stepped surfaces. Our results provide a rationale for experimental observation of molecular carpeting on high-index vicinal surfaces of transition metals.