Supramolecular chirality by shear force driven self-assembly of nonchiral triphenylamine molecules

Abstract

Chirality which can be found in a wide range of scale from molecules to galaxy is one of interesting characteristics of nature. Because chirality has been used in life forms, much research effort has been focused on understanding and application of chirality. Especially, chiral supramolecules formed from achiral molecules has attracted much attention. Previously, we reported that achiral triphenylamine (TPA) based molecules form chiral supramolecules with circularly polarized light in a chlorinated solvent. Herein, we use vortex, one of the macroscopic chirality, to induce chiral self-assembly of TPA derivatives. We carried out self-assembly of achiral TPA molecules into chiral supramolecules by using the shear force in aromatic solvents and characterized the self-assembled structures. Achiral TPA formed macroscopic helical nanostructures in some aromatic solvents. In benzene, we could selectively control the handedness of the aggregates by controlling the direction of the stirring. In addition, we found that the chirality of the supramolecules could be switched reversibly by further stirring after heating and subsequent cooling. We expect that chiral supramolecules could be used in many applications such as chiral sensors and asymmetric catalysts.