Surface-controlled reversal of the selectivity of halogen bonds

Abstract

Intermolecular halogen bonds are ideally suited for designing new molecular assemblies because of their strong directionality and the possibility of tuning the interactions by using different types of halogens or molecular moieties. Due to these unique properties of the halogen bonds, numerous areas of application have recently been identified and are still emerging. Here, we present an approach for controlling the 2D self-assembly process of organic molecules by adsorption to reactive vs. inert metal surfaces. Therewith, the order of halogen bond strengths that is known from gas phase or liquids can be reversed. Our approach relies on adjusting the molecular charge distribution, i.e., the σ-hole, by molecule-substrate interactions. The polarizability of the halogen and the reactiveness of the metal substrate are serving as control parameters. Our results establish the surface as a control knob for tuning molecular assemblies by reversing the selectivity of bonding sites, which is interesting for future applications.

Real-space Imaging of the Multiple Halogen Bonds by Ultrahigh-resolution Scanning Probe Microscopy

“…Similar bending halogen bond was reported by Ebeling et al 36 We infer that the steric hindrance of two adjacent H-atoms hinders the alignment of Br-atom with two N-atoms of a pyrazine ring.…”

“…In recent years, several reports have shown that STM with CO-tip is also able to unravel the internal atomic structure of a single molecule. [33][34][35] The intermolecular force of triangular halogen bonds has also recently been studied by nc-AFM and STM, 36 and the bright lines appear at positions where the triangular halogen bond form at STM images. 13 The bright lines (or image contrast) are thought to originate from the interacting electrons of intermolecular bonds, while others propose that bright lines are caused by the bending of the CO molecule.…”

Manifold dynamic non-covalent interactions for steering molecular assembly and cyclization

“…However, the majority of these studies have been focused on planar or nearly-planar molecular structures. In addition, on-surface molecular assemblies investigated to date mainly involve a limited category of non-covalent interactions, such as halogen bond [5,15,16] or hydrogen bond interactions. [17] Molecularlevel insights into complex three-dimensional (3D)-like assemblies with manifold noncovalent interactions remain largely unexplored [18].…”

From starphenes to non-benzenoid linear conjugated polymers by substrate templating

“…S7c) and at a distance of about 3.2 Å from one another. The driving force for such self-assembly may thus be either the formation of halogen bonds, [25,26] or the coordination through a gold atom. For the former to be attractive, C-Br bonds require a certain angular offset, whereas the latter requires a surface atom or adatom to be coordinated to the halogens.…”