The Helix to Super-Helix Transition in the Self-Assembly of p-Systems: Superseding of Molecular Chirality at Hierarchical Level

Abstract

Higher-order super-helical structures derived from biological molecules are known to evolve through opposite coiling of the initial helical fibers, as seen in collagen protein. A similar phenomenon is observed in a p-system self-assembly of chiral oligo(phenyleneethylene) derivatives (S)-1 and (R)- 1 that explains the unequal formation of both left- and righthanded helices from molecule having a specific chiral center. Concentration- and temperature-dependent circular dichroism (CD) and UV/Vis spectroscopic studies revealed that the initial formation of helical aggregates is in accordance with the molecular chirality. At the next level of hierarchical selfassembly, coiling of the fibers occurs with opposite handedness, thereby superseding the command of the molecular chirality. This was confirmed by solvent-dependent decoiling of superhelical structures and concentration-dependent morphological analysis.