Mechanochemical Synthesis of Luminescent 0D Halides: Metal-Center Coordination Control and Photoluminescence Mechanism Studies.

Zero-dimensional (0D) organic-inorganic hybrid metal halides have attracted significant attention for their unique photophysical properties; however, the universal synthesis of homologous multimetal systems via a unified pathway remains challenging. Herein, we report a rapid, liquid-assisted grinding (LAG) mechanochemical strategy for the synthesis of a series of 0D hybrid halides with distinct coordination geometries: (IMP)MnCl4 (tetrahedral), (IMP)SnCl6 (octahedral), and (IMP)SbCl5 (pentacoordinate). Structural and Hirshfeld surface analyses reveal that bulky IMP cations encapsulate the discrete inorganic units via extensive C-H···Cl interactions, suppressing nonradiative relaxation. As a result, the Sn/Sb-based compounds exhibit enhanced photoluminescence with PLQYs of 40.3% and 28.6%, respectively. Time-resolved spectroscopy and DFT calculations demonstrate coordination-dependent emission mechanisms: the Sn and Sb systems show millisecond phosphorescence from charge-transfer states, while the localized electronic characteristics of the [MnCl4]2- unit may contribute to the distinct excited-state relaxation behaviors observed experimentally. Leveraging these distinct excited-state dynamics, a time-resolved, multilevel anticounterfeiting platform is constructed. This work provides a general synthetic strategy and highlights the role of coordination environment and supramolecular interactions in tuning luminescence.