Irreversible Inversion of Circularly Polarized Luminescence via Magneto‐Thermal‐Induced Structural Reorganization in a Chiral Lead Bromide Crystal

Abstract The dynamic inversion of circularly polarized luminescence (CPL) in solid‐state materials is a pivotal goal for both fundamental science and advanced chiroptoelectronic technologies. While achievable in flexible molecular systems, CPL inversion remains profoundly challenging in crystalline lattices due to their inherent structural rigidity. Herein, we demonstrate irreversible CPL inversion in a single crystal of a lead‐based hybrid metal halide, P / M ‐(C 4 H 14 S 2 N 2 )PbBr 5 ·H 3 O ( P / M ‐PbBr), engineered with stereochemically dynamic cysteamine cations. The inversion is achieved by applying a magnetic field at a specific phase transition temperature (486 K), which triggers a magneto‐thermal‐induced structural transformation that flips the crystal's absolute chirality between its P and M enantiomeric forms. This configurational reversal of the organic moieties drives a cooperative structural inversion of the entire inorganic lattice, thereby switching the CPL handedness. Our work provides a fundamental strategy for achieving chirality control in rigid crystalline systems, paving the way for developing programmable chiroptical materials and devices.