Visualizing Halogen Bonds in Planar Supramolecular Systems

Abstract

Supramolecular interactions were studied in two planar model systems, 1,5- and 2,6-dibromoanthraquinones, prepared on Au(111) using scanning tunneling microscopy. In both systems, we found rigid triangular structures that consisted of simultaneous halogen bonds and hydrogen bonds, as reported in protein−ligand complexes. We proposed molecular models that were well reproduced by first-principle studies and could be explained by halogen and hydrogen bonds. The distances, angles, and, strengths of the intermolecular bonds were measured in the observed structures, and showed good agreement with existing bulk data.

Halogen Bonding in Two‐Dimensional Crystal Engineering

“…However, they are quite similar to the distances of the same type of bonds measured in bulk under similar molecular environments ( i. e . atoms covalently bonded to C atoms) . Similar quadruple nodes based on X 4 synthons have been reported for self‐assembly of brominated pyrenes on Au(111) under UHV conditions …”

“…The degree of complexity of such assemblies can be increased by incorporating other (hetero)atoms in the molecules. The study of two different isomers of dibromoanthraquinones ( 17 , 18 Figure a) at the UHV/Au(111) interface showed how the molecular design can influence the nature of the interactions and the arrangement of molecules within the network . 17 forms an open network with square‐shaped pores stabilized by a combination of hydrogen and halogen bonds between neighbouring molecules.…”

Probing halogen–halogen interactions in solution

“…A particularly interesting class of XB interaction is the halogen-halogen (XX) interaction, which occurs in particular between two halogen atoms that are bonded to (different) carbon atoms. Although weak, these XX interactions have been shown to be essential to the formation of numerous selfassembled monolayers [8][9][10][11][12][13][14] and crystalline structures. [15][16][17][18][19][20] For instance, the introduction of halogen atoms at key positions allows to organize molecules in the solid state to favour topochemical polymerization, 21 or inclusion complex formation.…”

Self-assembled two-dimensional nanoporous molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111)

“…48 The Br··· Br distance is ∼3.94 nm, in accordance with previous reports. 44,49 In order to initialize the surface polymerization and to study the formation and structures of the intermediate stage, we further conducted an UV laser (wavelength 266 nm) irradiation experiment on the self-assembled molecular superstructures on Ag(111) at 80 K. After 10 min of laser irradiation, the selfassembled structures transformed from square-like architectures to large scale hexagonal nanopores, as shown in Figures 3(a) and 3(b). The unit cell parameters for the nanoporous structures are a 2 = 2.6 ± 0.1 nm, b 2 = 2.6 ± 0.1 nm, and α 2 = 61 • ± 2 • .…”