Modulating Circularly Polarized Luminescence by Biasing Chiral Coordination Geometries in Zn(II) Complexes

Circularly polarized luminescence (CPL) was enhanced by biasing the coordination geometry of chiral Zn(II) complexes. In solution, an equilibrium between the Λ and Δ coordination geometries was observed, and the diastereomer excess ( de ) increased with decreasing temperature. Notably, bromine substitution significantly enhanced this bias, leading to a pronounced preference for a single‐coordination geometry and reaching 63% de at −60 °C. The Zn(II) complexes exhibited blue fluorescence under UV excitation with moderate emission efficiencies. Interestingly, a gradual enhancement of CPL intensity was observed upon lowering the temperature, and the luminescence dissymmetry factor ( g _lum ) reached a maximum value of 1.8 × 10 ⁻³ for bromine‐substituted complexes. Importantly, biasing the coordination geometry resulted in effective tuning of the CPL while preserving the blue‐emissive character of the Zn(II) complexes. These findings present coordination geometry biasing as a powerful design tool for controlling CPL in chiral metal‐based luminophores.