Pillar[5]arene-Based Visual Planar Chirality Switches with Variable Color Expression

The development of molecular-level chirality control systems that exhibit macroscopic property changes remains a significant challenge, primarily due to the lack of dynamic chirality platforms and efficient molecular designs. Herein, we report two chirality-controlled switches (<b>P5N-</b><i><b>R</b></i> and <b>P5N-</b><i><b>S</b></i>) in which planar chirality can be reversibly modulated by solvents, temperature, and guest molecules, with the corresponding color changes. This correlation means that the inclusion of guests into the macrocycle cavity promotes the adoption of a pillar conformation in which the <i>pR</i>-form, <b>P5N-</b><i><b>R</b></i>, is dominant, while the exclusion of guests favors the <i>pS</i>-form with a folded conformation. These different conformations lead to distinct intramolecular hydrogen bonds in <b>P5N-</b><i><b>R</b></i>, altering the electron-donating ability of the amino groups to the benzoquinone unit and causing color changes. Furthermore, <b>P5N-</b><i><b>S</b></i> exhibits similar chirality-controlled and color change behavior. This work demonstrates a new strategy for constructing dynamic chiral switches with macroscopic property changes, which has significant implications for the development of advanced, responsive chiral materials.