Assessment of Intermolecular Hydrogen Bonds in the Compact Self-Assemblies of 1,3,5-Tris(4-carboxyphenyl)benzene Molecules on Au(111).

The self-assembly of star-shaped 1,3,5-tris(4-carboxyphenyl)benzene molecules on Au(111) is investigated by using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. STM shows that for one monolayer deposition, the molecules self-assemble into two compact nanoarchitectures: one with a rectangular unit cell and a second one with a parallelogram unit cell. DFT calculations reveal that these two compact structures are stabilized by hydrogen bonds and that the rectangular nanoarchitecture has the lowest energy. The rectangular unit cell is stabilized by two hydrogen bonds per molecule with an energy of 0.3 eV, whereas the parallelogram unit cell is stabilized by 1.2 hydrogen bonds per molecule with an energy of 0.25 eV each.