Conjugated Molecules as Multifunctional Architects: Boosting Water Stability and Radiance of Mn-Based Metal Halides for Flexible X-ray Scintillation Imaging.

Zero-dimensional organic-inorganic metal halides (OIMHs) have attracted considerable attention for optoelectronic applications due to their exceptional luminescent properties. However, their practical utilization is severely hindered by poor moisture and thermal stability, especially in the case of manganese-based compounds, which tend to degrade rapidly under humid conditions. To address this challenge, we propose a polyaromatic molecular engineering strategy. By incorporating bulky hydrophobic triazine-derived cations (TNZ-2 and TNZ-3), we successfully synthesized two zero-dimensional Mn2+-based halides, (TNZ-2)2MnBr4 and (TNZ-3)2MnBr4, featuring isolated [MnBr4]2- tetrahedra. Notably, (TNZ-3)2MnBr4 exhibits significantly enhanced stability under high-humidity conditions (70% relative humidity for 30 days) or even upon immersion in water, and achieves efficient green emission with a photoluminescence quantum yield of 33.11%, benefiting from the strong quantum confinement effect of its zero-dimensional structure. Furthermore, flexible (TNZ-3)2MnBr4@PMMA composite films were fabricated and demonstrated to function effectively in X-ray imaging, highlighting their potential in flexible optoelectronic devices. This work provides a viable molecular design route toward stable and highly luminescent OIMH materials.