Photo/Radioluminescence Enhancement of Hybrid Aminoalkyl-Based Organophosphonium Manganese(II) Halide Single Crystals Induced by Halogen Replacement

Organic-inorganic hybrid manganese(II) halides (OIMnHs) have attracted significant interest in optoelectronic fields due to their nontoxicity, special luminescent properties, and structural diversity. However, the OIMnHs have exhibited only green or red emission based on tetrahedral and octahedral crystal field theory, which severely limits further tunability. Here, we synthesized two single crystals (3-DTP)₂Mn₂Cl₈·H₂O and 3-DTPMnBr₄ [3-DTP = 3-(dimethylamino)propyltriphenylphosphonium] by halogen replacement from Cl to Br. Moreover, crystal structures, UV-vis diffuse reflectance spectra, theoretical calculations, and photo/radioluminescence of (3-DTP)₂Mn₂Cl₈·H₂O and 3-DTPMnBr₄ were systematically studied. Especially, photo/radioluminescence results demonstrate that (3-DTP)₂Mn₂Cl₈·H₂O and 3-DTPMnBr₄ single crystals exhibit yellow/yellow-green emission under UV-365 nm and X-ray irradiations. More importantly, the photoluminescence quantum yield (PLQY) of (3-DTP)₂Mn₂Cl₈·H₂O and 3-DTPMnBr₄ increased from 4.38% to 18.93%, and their PL lifetime value decreased significantly from 940.7 μs to 99.9 μs with the replacement from Cl to Br. Notably, 3-DTPMnBr₄ showed a low X-ray detection limit of 36.8 nGyairs⁻¹ as a potential X-ray scintillator, while (3-DTP)₂Mn₂Cl₈·H₂O exhibited the chiral space group P2₁ (No. 4) with a relatively strong second-harmonic generation effect. This work will provide guidance for constructing novel hybrid metal halide systems compatible with luminescence and second-harmonic generation.