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 R/S-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 R/S-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.