Linear Regulation of Red Emission in an Organic-Inorganic Manganese Bromide via Pressure

Organic-inorganic metal halides (OIMHs) can show diverse optical properties under pressure since their emission pathways can be facilely manipulated through hydrostatic compression. However, pressure-induced phase transitions and their irreversibility disrupt the linear tuning of the pressure-dependent optical properties, thereby hampering their applications in pressure sensing. To improve structural stability, we introduced O-HBr interactions and synthesized a zero-dimensional (0D) manganese-based (Mn-based) OIMH, (TDMA)MnBr3(H2O)(2) [TDMA = (tetrahydrofuran-3-yl)methylammonium], with a 625 nm phosphorescence emission. For pressure-induced discoloration, high pressure enhances the crystal field splitting energy of Mn2+ through octahedral compression and distortion, which leads to the decrease of the band gap and the red shift of the emission wavelength. Above all, the strong O-HBr interactions formed between adjacent octahedra have effectively improved the structural stability and suppressed phase transitions under high pressure, which promotes the generation of a highly linear pressure-emission wavelength correlation. This encouraging result opens up the potential applications of pressure sensing within the red emission of 0D Mn-based OIMHs.