Dense or Porous Packing? Two-Dimensional Self-Assembly of Star-Shaped Mono-, Bi-, and Terpyridine Derivatives
Trawny, Daniel and Schlexer, Philomena and Steenbergen, Krista G. and Rabe, Jürgen P. and Paulus, Beate and Reißig, Hans-Ulrich – 2015
The self-assembly behavior of five star-shaped pyridyl-functionalized 1,3,5-triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono- and bipyridine derivatives self-assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers.