Tuning phase transition and fluorescence quenching in 0D organic-inorganic hybrid materials by precise organic cation...

Organic-inorganic hybrid materials exhibiting stimuli-responsive photoluminescence have garnered significant attention as promising candidates for advanced anti-counterfeiting and information encryption applications. However, achieving controllable fluorescence quenching through rational molecular design remains a considerable challenge. Herein, we report the synthesis and characterization of three novel organic-inorganic hybrid compounds, (ETMP)₂MnBr₄ (1), (PTMP)₂MnBr₄ (2) and (ATMP)₂MnBr₄ (3) (ETMP = ethyl-trimethyl-phosphonium, PTMP = propyl-trimethyl-phosphonium, and ATMP = allyl-trimethyl-phosphonium). By progressively substituting the organic groups from ethyl to allyl, we observed a significant increase in the phase transition temperature, rising from 312.3 K to 359.3 K, an increase of 47 K. Furthermore, by changing the cations, the photoluminescence quantum yield was significantly improved, increasing from 35.90% to 75.26%. Interestingly, these compounds exhibited distinct fluorescence quenching behaviors with increasing temperature. After the phase transition, the photoluminescence intensities of (ETMP)₂MnBr₄ and (PTMP)₂MnBr₄ significantly decreased and eventually stabilized at a certain level. In contrast, (ATMP)₂MnBr₄ exhibited complete fluorescence quenching. By combining different photoluminescent properties, the potential applications of these materials in anti-counterfeiting technologies were explored. This study offers new strategies for tuning phase-transition temperatures and luminescence performance in manganese-based materials, providing valuable insights for the development of low-toxicity and high-efficiency multifunctional materials.