Chiral self-assembly of triphenylamine molecules induced by external stimuli

Abstract

Chirality, a basic property of nature, can be observed everywhere, from atomic to galactic scales. Especially in living systems, chirality plays an important role in biological activities, from medicinal functionality to protein folding. Therefore, research that reveals the origin of chirality have been drawing attention. Interestingly, some achiral molecules can form chiral self-assembled structures by symmetry breaking. This dissertation deals with formation of a chiral self-assembled structures from achiral molecules by symmetry breaking of achiral triphenylamine molecules through external stimuli. The structural and thermodynamic analysis of the formed self-assembled structures provides an understanding of the scale and dimensional effect of the chiral external stimuli and the influence of the intramolecular functional groups. In chapter 2 of this dissertation, three triphenylamine molecules according to the number of hydrogen bonds are synthesized and then a chiral self-assembled structure was induced with circularly polarized light to investigate how hydrogen bonds affect the structure of the chiral self-assembled structures. As hydrogen bonds increased, the stabilization energy and rotation angle increased. These results reveals that intramolecular interaction and structural formation by hydrogen bonds play an important role in forming a helical chiral self-assembled structure using circularly polarized light to the achiral monomers. In chapter 3 of this dissertation, the formation of a chiral self-assembled structures of achiral triphenylamine derivatives in aromatic solvents by shear force and circularly polarized light are studied. Self-assembly are performed under the same pathway, and it was found that the direction of the helical chiral self-assembled supramolecules was controlled by the direction of external stimuli. By examining the morphology and thermodynamic stability of the formed supramolecular fibers, qualitatively analysis was attempted based on the dimension and scale effect of the shear force and circularly polarized light. This study provides understanding of the origin of homochirality in nature by demonstrating that the same molecules prepared under the same conditions but with external stimuli having different scale adopt a different chirality dimension. In chapter 4 of this dissertation, the chiral amplification of achiral molecules through a trace amount of chiral molecules based on amino acids was investigated by synthesizing and assembling achiral and chiral triphenylamine molecules together.