Ligand Confinement for Fast‐Decay Cu─I Chain Scintillators Enabling High‐Resolution X‐ray Imaging and 3D Tomography

ABSTRACT Chain‐like one‐dimensional (1D) copper(I) iodide cluster complexes are promising scintillator candidates due to their enhanced x‐ray absorption, robust frameworks, and excellent photostability. However, their emission efficiencies remain significantly lower than those of zero‐dimensional analogues. Herein, we propose a ligand‐confinement strategy that employs sterically hindered, electronically tuned pyrimidine‐based bridging ligands to simultaneously boost x‐ray excited luminescence (XEL) and accelerate decay dynamics in 1D Cu–I cluster scintillators. Rigid, compact bidentate ligands increase structural rigidity while reducing the organic fraction for enhanced x‐ray absorption. Meanwhile, asymmetric substituents induce coupled spatial and electronic confinement, giving rise to quantum‐wire‐like electronic states that promote radiative transitions. As a result, CuI(4‐Mepym) exhibits a six‐fold enhancement in photoluminescence quantum yield compared to CuI(2‐Mepym) , together with a fast decay lifetime of 1.28 µs, surpassing most reported copper(I) iodide cluster complexes. Combined with high stability, good solution processability, and a light yield comparable to commercial LuAG:Ce (∼25 000 ph MeV −1 ), CuI(4‐Mepym) breaks the conventional brightness–speed trade‐off and enables high‐resolution static imaging (>20 lp mm −1 ), artifact‐free dynamic x‐ray imaging, and high‐fidelity 3D tomography. This work establishes ligand confinement as an effective design principle for developing high‐brightness, fast‐decay 1D Cu–I cluster scintillators for advanced x‐ray imaging applications.