Networks of non-planar molecules with halogen bonds studied using scanning tunneling microscopy on Au (111)

Molecular networks connected by halogen bonds have been actively studied due to their ubiquity in biological systems and complementary role to hydrogen bonds. Although networks of planar molecules with halogen ligands have been studied using scanning tunneling microscopy (STM), those of non-planar molecules have not. Here, we report on the network structures of non-planar molecules containing Br-ligands, tetrabromo-spirobifluorene on Au (111), studied using STM. One and two-dimensional networks were observed and their intermolecular interactions were investigated. In two-dimensional networks, a molecule forms 3.5 Br⋯Br halogen bonds and 2 Br⋯H hydrogen bonds, as supported by our density functional theory calculation results. Our study demonstrates that intermolecular structures of non-planar molecules with halogen bonds can be probed on surfaces using STM.