Lead-Free Scintillator Based on a Luminescent Green-Emitting Material Derived from Manganese(II) Chloride for High-Resolution X-Ray Imaging

Manganese(II) halides have attracted significant research attention because of their unique zero-dimensional structures, low toxicity, structural diversity, and tunable photoluminescent properties. However, the development of neutral manganese(II) chlorides has lagged behind their manganese(II) bromide counterparts in X-ray imaging applications. Herein, we report a green-emitting neutral monodentate manganese(II) chloride complex (H-Cl) by introducing the cyclohexyldiphenylphosphine oxide as the ligand, which could be synthesized via a simple room-temperature solvent evaporation method. Complex H-Cl exhibits bright photoluminescence with an emission peak at 516 nm with a full-width at half-maximum (FWHM) of 61 nm, and achieves a photoluminescence quantum yield (PLQY) of 16.69%, surpassing most reported neutral monodentate manganese(II) chlorides. As an X-ray scintillator, complex H-Cl realizes a detection limit of 1.581 µGy/s, which is much lower than that of the standard for X-ray medical diagnostics. It also shows a high spatial resolution exceeding 9.6 lp/mm, highlighting its potential for advanced scintillator design and high-resolution X-ray imaging technology.