Interplay between Halogen and Hydrogen Bonds in 2D Self-Assembly on the Gold Surface: A First-Principles Investigation

The interplay between halogen bonding and hydrogen bonding has caused recent interest in the formation of 2D self-assembled molecular arrays on solid surfaces. Herein we present a first-principles density functional theory study of the self-assemblies of two brominated anthraquione molecules on Au(111) and Au(110). The possible binding sites of these two compounds on the facets were first explored, and then various self-assembled patterns involving different halogen and hydrogen bonds were examined both in the gas phase and on the gold surface. To visually investigate the nature of lateral adsorbate–adsorbate and vertical adsorbate–substrate interactions, the atoms in molecules, noncovalent interaction index, and electron density difference analyses were undertaken. The molecules tend to be self-assembled by means of triangular binding motifs with simultaneous halogen and hydrogen bonds. Upon the formation of the dimers in the gas phase as well as on the gold surface, significant band shifts around the Fe...