Cooperation and competition between halogen bonding and van der Waals forces in supramolecular engineering at the aliphatic hydrocarbon/graphite interface: position and number of bromine group effects

Abstract

Herein, the photophysical properties of two π-conjugated thienophenanthrene derivatives (6,9- and 5,10-DBTD) are reported. Their self-assembled monolayers in aliphatic hydrocarbon solvents under different concentrations were investigated by scanning tunneling microscopy on a graphite surface. The STM results revealed that the self-assembled structures of the two geometrical isomers exhibited absolutely different behaviors. At the aliphatic solvent/graphite interface, 6,9-DBTD produced almost a single stable coassembled linear structure, except for that with n-tridecane as the solvent. However, the self-assembly of 5,10-DBTD showed structural diversity, and it presented a gradient variety through increasing the chain length of the aliphatic solvents as well as the solution concentration. All ordered self-assembled adlayers critically depend on not only the interchain van der Waals (vdW) interactions, but also on multiple intermolecular interactions, including BrO[double bond, length as m-dash]C and BrS hetero-halogen bonds, homo-BrBr interactions, and HBr and HO hydrogen bonds. We proposed that the cooperation and competition of the intermolecular interactions involving a Br atom and interchain vdW forces induce this structural variety. Density functional theory calculations support to unravel the different elementary structural units based on halogen bonds and hydrogen bonds and were useful tools to dissect and explain the formation mechanism.

Intermolecular H···O═C bonds induced 2D self‐assembly of thiophene based diketopyrrolopyrrole derivative

“…As revealed by STM results, TDPP‐C16 molecules form the same adlayers at the liquid/solid interface using different solvents (1‐octanoic acid and n ‐hexadecane) and at the gas/solid interface. Although it is common that solution concentration and solvent can be a key parameter in some cases, no solution concentration and solvent effects are observed. The formation of stable adlayer indicates the strong intermolecular interactions.…”

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.…”

Halogen Bonds Fabricate 2D Molecular Self-Assembled Nanostructures by Scanning Tunneling Microscopy

“…2.9. Self-Assembled Patterns of Thienophenanthrene Derivatives at the Liquid/HOPG Interface Self-assembly of thienophenanthrene (TP) derivatives of 6,9-DBTD and 5,10-DBTD (Scheme 1k and Figure 14a) with triangle π-conjugated cores were investigated at the n-tridecane/HOPG interface by varying the solution concentration (from 10 −3 to 10 −6 M) [86,87]. A well-ordered lamellar structure of 6,9-DBTD (Figure 14e (j-n) Proposed structural models of (e-i).…”

“…A well-ordered lamellar structure of 6,9-DBTD (Figure 14e (j-n) Proposed structural models of (e-i). Reproduced from [86,87] with permission from the Royal Society of Chemistry.…”