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DOI: 10.1002/adma. 201501026 excellent ferrolectricity.[43, 45, 46] Such AMX 3 structures involve a large class of compounds (A= monovalent organic ammonium cation; M= Mn, Fe, Co, Ni, Cu, Cr, or V; X= Cl or Br).[47] Among them, Mn-containing compounds have been reported to emit brightly.[48] Thus, we tried to design AMnX 3-type compounds, and found a new ferroelectric:(pyrrolidinium) MnBr 3 (1)(Scheme 1), which exhibits intense red luminescence under a UV excitation. Here, we report its preparation, phase transition, ferroelectric and luminescent properties, as well as weak ferromagnetism (see Supporting Information). Compound 1 was found to undergo a structural phase transition at around Tc= 219 K first by thermal analysis and dielectric measurements (Figure 1 a, c). For precise analysis of the main structural differences to understand the origin of the ferroelectricity, we determined the crystal …