Hierarchical amplification of chirality in anion-coordinated tetrahedral cages†

Abstract

Chirality is vital in asymmetric catalysis, biological systems, and materials science. However, the control of chiral transfer and amplification remains challenging, but fascinating. Herein, we report the chirality transferred from chiral carbon centers to ‘aniono’ tetrahedral cages, which were constructed through the self-assembly of chiral C₃-symmetric tris–bis(urea) ligands and oxoanions (PO₄³⁻ or CO₃²⁻). The host–guest interaction can further alter the chirality, resulting in enhanced CD intensity accompanied by a redshift. Furthermore, anions have a great influence on the chiral behavior of the mixed-ligand (chiral and achiral ligands mixed in different proportions) cages due to the occurrence of structural transformation. From the self-assembly and subsequent host–guest chemistry, we establish a hierarchical chiral system at the supramolecular level, featuring controllable chiral transfer and amplification.