2D self-assembly of oligo(p-phenylene vinylene) derivatives: from dimers to chiral rosettes

Enantiomerically pure oligo(p-phenylene vinylene) diaminotriazine derivatives and a short structurally related achiral diaminotriazine derivative, all having a rigid backbone in common, are studied to self-assemble at the solution-graphite interface by scanning tunneling microscopy. As a function of the length of the backbone, different two-dimensional motifs are formed (dimers and rosettes) that are rationalized in terms of the balance between different intermolecular interactions, in this case, intermolecular hydrogen bonding and the packing requirements of the alkyl chains on a graphite surface. In addition, the effect of molecular chirality on monolayer chirality is investigated, revealing molecular size-dependent expressions of the monolayer chirality.