Mechanical Manipulation of Archimedean Spirals of an Achiral Pyrazinacene for Chiral Assemblies

The fabrication of chiral assemblies from achiral molecules has attracted considerable interest since it provides insight into the structures of biological systems. It is also of general importance from the point-of-view of the various factors affecting self-assembly processes especially supramolecular chirality. Here, the dynamic interfacial assembly strategy is used to obtain unusual chiral assemblies from achiral linear nitrogen-rich acene derivatives, the pyrazinacenes. 1D supramolecular J-aggregate tapes of homogeneous width are coiled to form Archimedean spirals. Moreover, the dynamic assembly process further permits the controlled transformation of the Archimedean spirals into tightly coiled toroids and chiral concentric vortices. Grazing incidence X-ray diffraction study using synchrotron radiation reveals that J-aggregate monolayer deposited using the layer-by-layer technique forms a lamellar columnar oblique mesophase-like structure. Molecular packing in J-aggregates provides a significant channel for the occurrence of charge transport exhibiting carrier mobility of 0.045 cm(2) V-1 s(-1) due to enhanced electronic coupling. This study illustrates an intriguing approach for achieving chiral supramolecular assemblies from achiral molecules and also reveals the potential of the pyrazinacenes as charge transport materials for molecular electronics.