Aggregation and assembly of crescent foldamers

Recent studies have started to provide initial insights into the aggregation and assembly of two classes of back-rigidified foldamers with flat, curved backbones consisting of aromatic residues. With their persistent shape that presents large, well-defined aromatic surface areas, these crescent foldamers were found to undergo size-dependent aggregation in solution and pack into 1D assemblies in the solid state. Crescent aromatic oligoamides undergo stacking interactions not only in polar solvents but also in nonpolar ones, a unique property that is not associated with many other molecules that associate via π-π stacking interaction. The stacking of oligo(m-phenylene ethynylenes) is similar to aromatic hydrocarbons, being promoted in polar solvents such as methanol while being discouraged in nonpolar solvents such as halohydrocarbons. The ready synthetic availability of crescent foldamers makes it possible to directly control the intermolecular interaction by tuning surface areas. Besides, the columnar assembly of these cavity-containing molecules provides a new strategy for constructing supramolecular nanotubular structures.