Concentration-Dependent Two-Dimensional Halogen-Bonded Self-Assembly of 1,3,5-Tris(4-iodophenyl)benzene Molecules at the Solid–Liquid Interface

Abstract

The concentration-dependent self-assembly of star-shaped 1,3,5-tris­(4-iodophenyl)­benzene at the 1-phenyloctane/graphite interface is investigated using scanning tunneling microscopy. The molecules self-assemble into a hexagonal porous halogen-bonded nanoarchitecture at low concentration. This structure is stabilized by X3 synthons. The molecules are oriented along the same direction in this arrangement. At higher concentration two molecular orientations are observed. The molecules then form a porous parallelogram halogen-bonded structure stabilized by X2 synthons. The density of molecular packing is thus higher at high solution concentration. High solution concentration also leads to the appearance of domain boundary in the parallelogram structure. Iodine bonds appear to be a promising alternative to hydrogen bonds to engineer tunable organic porous structures on flat surfaces.

Halogen Bonding in Two‐Dimensional Crystal Engineering

“…The fact that halogenated building blocks also show concentration-dependent assembly behaviour was demonstrated in the case of 1,3,5-tris(4-iodophenyl)benzene (4, Figure 4a) at the 1-phenyloctane/HOPG interface. [27] This building block forms a relatively densely packed network at relatively higher concentrations (10 À 7 M, Figure 4b).…”

“…The open spaces within the network are occupied by mobile 1‐phenyloctane molecules. The low‐density network formed by 4 is one of the few examples where halogen bonding interactions appear to be structure directing in nature ( vide infra ) …”

“…The low-density network formed by 4 is one of the few examples where halogen bonding interactions appear to be structure directing in nature (vide infra). [27] Variation in the position and the number of the halogen substituents on the aromatic framework also influences the outcome of the self-assembly process. This aspect was illustrated using alkoxy substituted phenanthrene derivatives.…”

“…(d) and (e) show the STM image of the network obtained at lower concentrations (< 10 À 9 M) and the corresponding molecular model for the network, respectively. Reproduced from ref [27]. with permission from the American Chemical Society.…”

Surface‐Confined Self‐Assembly of Asymmetric Tetratopic Molecular Building Blocks

“…For example, adsorbed structures, such as small molecular aggregates (also cyclic oligomers), straight and bent chains, strings, wires, ladders and molecular networks with precisely controllable size and shape have been successfully designed and realized using linear and star‐shaped molecular tectons adsorbed on metallic substrates and on graphite . In those instances weak intermolecular interactions, including hydrogen and halogen bonding, metal‐organic ligand coordination or even van der Waals forces have been used to sustain the resulting supramolecular constructs. Moreover, the directed on‐surface self‐assembly of reactive building blocks, especially of the halogenated (poly)aromatic molecules, has been used as an effective route to low‐dimensional covalent polymers (e. g. polyphenyl wires, graphene nanoribbons and cyclic oligomers) having presumed internal architectures …”