Chiral nanostructures self-assembled from nitrocinnamic amide amphiphiles: substituent and solvent effects

Chiral nanostructures, such as α-helical proteins and double helix DNA, are widely found in biological systems and play a significant role in the biofunction of life. These structures are essentially fabricated through the covalent or noncovalent bonds between small chiral molecules. It is thus an important issue to understand how small chiral molecules can form chiral nanostructures. Here, using a series of isomeric nitrocinnamic amide derivatives, we have investigated the self-assembly behavior and the effect of the substituent position as well as the solvent on the formation of chiral nanostructures. It was found that totally different chiral nanostructures were formed due to the different positions of the nitro group on the cinnamic amide. Moreover, it was found that the chiral sense of the self-assembled nanostructures can be regulated by the solvent whereby helicity inversion was observed. This work provides a simple way to regulate the self-assembly pathway via molecular design and choice of solvent for the controlled creation of chiral nanostructures.