CSIR – National Institute for Interdisciplinary Science and Technology (NIIST)

Council of Scientific & Industrial Research (CSIR), Govt.Of India Thiruvananthapuram.

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

Mohamed Hifsudheen, Rakesh K. Mishra, Balaraman Vedhanarayanan, Vakayil K. Praveen,* and Ayyapanpillai Ajayaghosh*

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 -system self-assembly of chiral oligo(phenyleneethylene) derivatives (S)-1 and (R)-1 that explains the unequal formation of both left- and right- handed 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 self-assembly, coiling of the fibers occurs with opposite handedness, thereby superseding the command of the molecular chirality. This was confirmed by solvent-dependent decoiling of super-helical structures and concentration- dependent morphological analysis.

Angew. Chem., Int. Ed., 2017, 56, 12634–12638.

Full Text Link: http://dx.doi.org/10.1002/anie.201707392