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–H···Br 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–H···Br 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.