Halogen bonds in 2D supramolecular self-assembly of organic semiconductors

Weak interactions between bromine, sulphur, and hydrogen are shown to stabilize 2D supramolecular monolayers at the liquid-solid interface. Three different thiophene-based semiconducting organic molecules assemble into close-packed ultrathin ordered layers. A combination of scanning tunneling microscopy (STM) and density functional theory (DFT) elucidates the interactions within the monolayer. Electrostatic interactions are identified as the driving force for intermolecular Br center dot center dot center dot Br and Br center dot center dot center dot H bonding. We find that the S center dot center dot center dot S interactions of the 2D supramolecular layers correlate with the hole mobilities of thin film transistors of the same materials.