Hydrogen Bonding-Driven Structural Modulation in Narrowband Green-Emitting Mn2+ Hybrids for Enhanced X-ray Imaging Performance

Abstract

Zero-dimensional (0D) Mn2+-based Hybrids have attracted increasing attention as promising candidates for luminescent and scintillation materials due to their unique chemical compositions, crystal structures, and photophysical properties. However, the specific influence of hydrogen bonding, which serves as a key interaction between organic cations and the inorganic framework, has received limited investigation. In this study, two 0D Mn2+-based single crystals, [MePi]MnBr4 and [EtPi]MnBr4, were synthesized using a simple solvent to antisolvent recrystallization approach. Under 450 nm excitation, both compounds exhibit sharp green emissions attributed to the spin-forbidden d–d transitions of Mn2+. Differences in hydrogen bonding lead to distinct photoluminescence quantum yields (PLQY) and radioluminescence light yields (LY) between the two materials. Notably, [EtPi]MnBr4 shows a higher PLQY of 96%. When benchmarked against the commercial Lu3Al5O12:Ce3+ scintillator, [EtPi]MnBr4 achieves an estimated light yield of approximately 24110 photons MeV-1 and an X-ray detection limit of 44.66 μGy s-1. In addition, a flexible scintillation screen composed of [EtPi]MnBr4 embedded in PDMS was prepared, achieving a spatial resolution of 10 lp mm-1. These results highlight the potential of 0D Mn2+-based Hybrids as low-cost, eco-friendly, and solution-processable scintillators for multifunctional applications.