Reversible transformation between rings and coils in a dynamic hydrogen-bonded self-assembly.

Several proteins, such as tobacco mosaic virus coat protein and the β protein of the bacteriophage λ, are known to exhibit unique dynamic self-organization processes involving ring-shaped and extended helical nanostructures triggered by chemical stimuli. However, transformation of rings into coils as observed in biological assemblies has never been realized with synthetic molecular building blocks. Oligo(p-phenylenevinylene) functionalized on one end with barbituric acid and on the other end with aliphatic tails self-organizes in aliphatic solvents to form nanorings through hydrogen-bonding and π-stacking interactions. Upon an increase in concentration, the nanorings transform into rodlike nanostructures, which are considered to be formed through helically coiled objects consisting of quasi-one-dimensional fibers.