Formation of 1D “Perovskitoid” (API)₂Pb₃Br₁₀ Instead of Layered <110> Oriented 2D-Perovskite (API)PbBr₄ Under Different Dissolution Temperatures

The corrugated <110> oriented layered metal halide perovskites (MHP) are gaining increased attention for a variety of properties including intrinsic white light emission. One prototypical candidate is 1-(3-aminopropyl)imidazole lead bromide, which was reported to crystallize as the <110> oriented perovskite (API)PbBr₄ [API = 1-(3-aminopropyl)imidazole]. This work shows that under similar reaction conditions, the same components can instead form (API)₂Pb₃Br₁₀, which has a "perovskitoid" structure. (API)₂Pb₃Br₁₀ exhibits a reversible phase transition between 60 and -20 °C from a polar space group <i>I</i>2 to a centrosymmetric space group <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>P</mml:mi><mml:mover><mml:mn>1</mml:mn><mml:mo>¯</mml:mo></mml:mover></mml:math>. The structures and properties of both phases have been characterized by single-crystal and powder X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (ssNMR) accompanied by variable-temperature optical absorption and photoluminescence. In addition, a thermal decomposition of (API)PbBr₄ into (API)₂Pb₃Br₁₀ has been observed between 250 and 300 °C.