Geometry Symmetry of Conjugated Cores along C–Br Bond Effect on the 2D Self-Assembly by Intermolecular H···Br and Br···Br Bonds
Résumé
Supramolecular self-assemblies of bromine substituted benzene and naphthalene derivatives (Br-BC16 and Br-NC16) are investigated using scanning tunneling microscopy at the liquid-solid interface. These two molecules arrange in different linear patterns stabilized by intermolecular H···Br and Br···Br bonds. Due to the different geometry symmetry of conjugated cores along the C–Br bond, the side chains and conjugated cores of Br-BC16 pack with the same direction; however, the side chains of Br-NC16 stretch into different directions along the graphite lattices and the conjugated cores of Br-NC16 in each dimer adopt the reverse orientation. Electrostatic potential (ESP) maps and density functional theory (DFT) calculations show that a pair of intermolecular H···Br bonds between the hydrogen atoms with the positive charge and the bromine atoms with the negative charge in each dimer dominate the structural formation. In addition, a Br···Br bond in each dimer for Br-BC16 and a Br···Br bond between the neighboring dimers for Br-NC16 are formed to stabilize the nanostructures. The results provide insights into the understanding of molecular self-assembly at the liquid-solid interface through the hydrogen bond or the halogen bond for bromine substituted molecules.