Achiral Guest-Modulated Circularly Polarized Luminescence of Chiral Macrocycles by Host–Guest Encapsulation

Developing concise strategies to modulate circularly polarized luminescence (CPL) remains a significant challenge. In this study, we present a host-guest complexation approach to fine-tune the CPL properties of chiral macrocycles. The luminescence of the chiral macrocyclic hosts <i>R</i>/<i>S</i>-BINOL[2] can be modulated from blue to cyan, green, red, and purple via complexation with achiral guests, enabling guest-based regulation of their luminescence features. Single crystal X-ray diffraction analyses of the host-guest complexes coupled with theoretical calculations provide support for the inference that encapsulation of electron-deficient guests by the electron-rich <i>R</i>/<i>S</i>-BINOL[2] hosts induces through-space charge transfer that is mediated by multiple noncovalent interactions, particularly lone-pair-π interactions. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps of the host-guest complexes can be tuned by varying the electronic nature of the guests, which translates to differences in the observed emission. This work provides a novel approach to the construction and modulation of CPL-active materials.