Self‐Reporting Activated Ester‐Amine Reaction for Enantioselective Multi‐Channel Visual Detection of Chiral Amines

Brightening up Full-Color and White Circularly Polarized Luminescence through Chiral Induction and Circularly Polarized Light Excitation

Preparation of chiral materials from achiral helical polymers has aroused great interest among researchers. In this work, chiral small molecules were utilized to accomplish chiral induction toward racemic helical polyacetylene via intermolecular π-π stacking by which chiral films with strong optical activity were fabricated. Furthermore, introducing fluorescent components generated full-color and white circularly polarized luminescence (CPL). A CPL generation mechanism is proposed accordingly, namely circularly polarized light excitation (CP-Ex). CPL emission and amplification of the luminescence dissymmetry factor were achieved under the synergetic effect of CP-Ex and chirality transfer. The CP-Ex mechanism was further verified by the double-layered film consisting of a chiral layer and a fluorescent layer. More noticeably, for double-layered films, the sense of CPL signals can be switched by changing the direction of excitation light. This work opens up new strategies for exploring tunable multiple- and white-color CPL materials.

Metal-Enhanced Helical Chirality of Coil Macromolecules: Bioinspired by Metal Coordination-Induced Protein Folding

Although the supramolecular helical structures of biomacromolecules have been studied, the examples of supramolecular systems that are assembled using coils to form helical polymer chains are still limited. Inspired by enhanced helical chirality at the supramolecular level in metal coordination-induced protein folding, a series of alanine-based coil copolymers (poly-(l-co-d)-ala-NH₂) carrying (l)- and (d)-alanine pendants were synthesized as a fresh research model to study the cooperative processes between homochirality property and metal coordination. The complexes of poly-(l-co-d)-ala-NH₂ and metal ions underwent a coil-to-helix transition and exhibited remarkable nonlinear effects based on the enantiomeric excess of the monomer unit in the copolymers, affording enhanced helical chirality compared to poly-(l-co-d)-ala-NH₂. More importantly, the synergistic effect of amplification of asymmetry and metal coordination triggered the formation of a helical molecular orbital on the polymer backbone via the coordination with the d orbital of copper ions. Thus, the helical chirality enhancement degree of poly-(l-co-d)-ala-NH₂/Cu²⁺ complexes (31.4) is approximately 3 times higher than that of poly-(l-co-d)-ala-NH₂/Ag⁺ complexes (9.8). This study not only provides important mechanistic insights into the enhancement of helical chirality for self-assembly but also establishes a new strategy for studying the homochiral amplification of asymmetry in biological supramolecular systems.