Helical supramolecular architectures of self-assembled linear pi-systems

Abstract

The present account describes the summary of the recent developments to the design of helical self-assemblies of linear pi-conjugated molecules, particularly of oligo(p-phenylenevinylenes) (OPVs) and oligo(p-phenyleneethyiiylenes) (OPEs). The design strategy involves functionalization of pi-conjugated backbones with achiral and chiral alkoxy side chains and hydroxymethyl end groups. Self-organization of these molecules in nonpolar hydrocarbon solvents resulted in a variety of supramolecular architectures such as tapes, helices, vesicles, and tubules. These supramolecular structures eventually lead to the formation of entangled networks resulting in gelation of solvents. It has been observed that OPVs in nonpolar solvents prefer to form supramolecular tapes whereas the corresponding OPEs form nano- to microsized vesicles and bundled fibers. Attachment of chiral motifs to OPVs and OPEs resulted in the formation of helical structures with a preferred handedness. The "sergeants and soldiers" co-assembly approach to chirality induction and amplification is efficient in these systems in the gel state. These results highlight the importance of the subtle difference in the strength of pi-pi interaction in gel forming linear pi-systems to the creation of hierarchical architectures with different size and shape, particularly helical structures.