Fluoride binding-modulated supramolecular chirality of urea-containing triarylamine and its photo-manifestation

In recent years, the regulation of anion-mediated chiral assemblies has gained significant interest. This study investigated the modulation of supramolecular chiroptical signals and chiral assembled structures in a triarylamine system containing a urea moiety through fluoride ion-urea bond interactions, aiming to understand the chiral sense amplification in supramolecular assemblies. Chiral triarylamine derivatives containing urea or amide units were synthesized and the self-assemblies were examined in the absence and presence of fluoride ions. The results revealed that the addition of F^- led to an increase in the circular dichroism (CD) intensity for the triarylamine compounds containing urea, accompanied by a transformation of the nanofiber structure into chiral twists. Comparative studies with other anions confirmed the selective specificity for F^-. Additionally, the combination of photo-induced triarylamine anion radicals allowed the F^- in the system to be visualized through photoirradiation, resulting in distinct colour changes that were detectable by the naked eye. The research demonstrates that F^- can selectively amplify supramolecular chirality through urea-F^- interactions, which may have promising applications in the fields of sensing and chiroptical devices.