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-phenyl-octane/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 X$_3$ 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 X$_2$ 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.