Self-assembly of dendronized non-planar conjugated molecules on a HOPG surface

Two-dimensional self-assembly of a series of dendronized molecules with different functional groups were observed on the highly oriented pyrolitic graphite (HOPG) surface by scanning tunneling microscopy (STM). The solution evaporation of these molecules on HOPG surfaces under ambient conditions results in the formation of self-organized monolayers. STM images demonstrate that the dendronized conjugated moiety in these molecules all adopt an edge-on arrangement on the HOPG surface, revealing the importance of π-π stacking interactions. The molecules with a hydroxyl as the substituent group adsorb on the HOPG surface with an ordered lamellar nanopattern resulting from the intermolecular hydrogen bonding. The molecules without alkyl chain are perpendicular to the HOPG surface, in a face-to-face card-stack fashion by π-π stacking. Alkyl chain assisted molecules adsorb on the HOPG surface with one side chain arrangement by tail-to-tail fashion. Our results demonstrate that the balance between different molecule-molecule and molecule-substrate interactions can be easily influenced by a small structural change in one of the components of the supramolecular assemblies resulting in different organized patterns on the solid surface.

Highlights► The conjugated moiety in dendronized non-planer molecules tends to arrange edge-on on the surface, revealing the importance of π-π stacking. ► Different substitution of the molecules leads to structural changes in the arrangement due to the different intermolecular interactions. ► It could contribute to an understanding in issues related to the intermolecular interactions and the performance of photovoltaic devices.