Unlocking Organic Cation Diversity in Metal Halides via Concurrent Crystal Growth and Menshutkin Reaction With Demonstrated Scintillation.

Organic-inorganic hybrid metal halides (OIMHs) have garnered great attention for optoelectronics applications. However, the synthesis of OIMHs has been largely confined to the use of pre-synthesized, commercial organic cations, severely limiting structural diversity and functional exploration. Herein, we present a groundbreaking in situ synthetic paradigm that concurrently executes the Menshutkin reaction and crystal growth in a single step. This one-pot strategy seamlessly couples the on-site custom quaternization of organic precursors with the crystallization of metal halide frameworks (such as Mn/Zn/Sb halides). By decoupling the synthesis from commercial cation sources, this method provides unparalleled freedom to incorporate a vast array of tailored cations, including those with long-chain, multi-aryl, and sophisticated geometric motifs (e.g., boat, chair, wing, bowl, and cyclic architectures). The power of this approach is exemplified by a novel Mn-based OIMH, Py-2 ([B(3-Br-PyCH2)Ph]3[MnBr4]2·2Br), which acts as an exceptional X-ray scintillator with a high light yield of 60,000 photons/MeV-2.4 times that of commercial LuAG:Ce. A flexible scintillator screen fabricated from Py-2 further demonstrates a high spatial resolution of 12.77 lp mm- 1, enabling high-resolution X-ray imaging. This work establishes a transformative in situ crystallization platform that opens a new dimension for the bespoke design of functional hybrid materials.