Probing
the halogen-bonded nanostructures of two-dimensional (2D)
supramolecular self-assembly is essential to understand and engineer
the nature of halogen bonding. However, exploring the formation mechanism
of the halogen bond still remains a challenge because it is a new
weak noncovalent interaction. Herein, we introduce nitrogen atoms
and Br groups in the conjugated core to synthesize 2,9-dibromo-6-(hexadecyloxy)phenanthridine
(2,9-DHP) in order to fabricate multiple action sites of halogen bonds.
We investigate the solvent effect on the 2D molecular self-assembly
at the liquid–solid interface by using scanning tunneling microscopy.
1-Octanoic acid, n-tridecane, n-tetradecane,
and n-hexadecane are chosen as the solvents. The
coadsorption of 1-octanoic acid molecules at low concentrations by
the molecule–solvent Br···O halogen bonds could
change the molecular arrangement. n-Tridecane, n-tetradecane, and n-hexadecane also coadsorb
in the adlayers; however, the molecular packing and intermolecular
interactions of 2,9-DHP remain the same at different solution concentrations.
The results demonstrate that the molecule–molecule N···Br···H
halogen bonds are strong enough to overcome the transformation of
intermolecular interactions.