Photoinduced Structural Relaxation in Chiral Copper(l) Iodide Cluster Scintillators for Circularly Polarized Radioluminescence Imaging.

Circularly polarized luminescence offers untapped potential for enhancing x-ray imaging resolution by suppressing optical crosstalk, yet its integration into high-performance scintillators remains unexplored. Here we report a new class of chiral copper(I) halide scintillators, including enantiopure R‑/S‑3‑MLCuI (3-ML represents 3-methylmorpholine) circularly polarized scintillators and racemic Rac‑3‑MLCuI scintillators. Strategic enantiomer selection enables precise control over crystal symmetry-chiral P42212 vs. centrosymmetric C2/c-dictating chiroptical activity. Combining TD-DFT, in situ XAS, and ultrafast spectroscopy, we elucidate that emission originates from cluster-centered self-trapped excitons confined within discrete [Cu4I4] cores, where pronounced excited-state Cu─Cu contraction and Cu─I elongation induce strong exciton-phonon coupling. Homochiral ligand environments impart persistent chiral imprinting, yielding |glum| values up to 1.0 × 10-2. The materials exhibit record light yields (58 000 photons•MeV-1), exceptional x-ray stability (>99% retention after 115 Gy), and ultra-low detection limits (78.9 n Gyair•s-1). A flexible S-3-MLCuI@TPU film incorporating polarization-gated imaging achieves 21.2 lp/mm resolution-significantly surpassing conventional scintillators by suppressing optical crosstalk. High‑fidelity x‑ray imaging of complex biological and electronic structures is demonstrated. This work provides a structure-property relationship that enables circularly polarized scintillation in chiral copper-iodide clusters, offering insights for further development of related systems.