The influence of hydrogen bonding and π-π Stacking interactions on the self-assembly properties of C₃-symmetrical oligo(p- phenylenevinylene) discs

Three C₃-symmetrical discotics containing a 1,3,5- benzenetricarboxamide unit functionalized with π-conjugated oligo(p-phenylenevinylene)s (OPV)s have been synthesized and fully characterized. For the two amide OPV discs a two-step transition from helical stacks to molecularly dissolved species was observed and surprisingly, the topology of the amide determines the stability and helicity of the fibers in solution and the length of the fibrils at a surface. In case of the bipyridine disc, aggregates were formed that show little chiral ordering while the stacks remain present over a large temperature range. At a surface, completely disordered structures exist probably as a result of competing types of π-π stacking interactions that differ in strength and orientation. The results show that the design of functional self-assembled architectures based on hydrogen bonding and π-π stacking interactions is an extremely delicate matter and reveal that special demands have to be taken into account to balance the topology, directionality and strength of multiple secondary interactions.