In this paper, three new hybrid phase transition compounds, [Hmpy]CdBr3 (1, Hmpy = N-methylpyrrolidinuium cation), [Hmpy]2CdBr4 (2) and [Hmpy]3CdBr3·CdBr4 (3), were synthetized by means of regulating the ratio of reactants. Systematic characterizations consisting of variable temperature X-ray single crystal diffraction, differential scanning calorimetry (DSC) and dielectric measurements reveal that 1 with infinite one-dimensional (1D) [CdBr3]n− chains undergoes a phase transition around 278 K; 2 with isolated [CdBr4]2− tetrahedrons exhibits a high-temperature phase transition close to 367 K, accompanied by prominent switchable dielectric behavior. Interestingly, 1D [CdBr3]n− chains and isolated [CdBr4]2− tetrahedrons both exist in 3, associated with a phase transition at 320 K. The phase transitions in the three compounds are originated from the order-disorder transitions of the Hmpy cation. It is expected that our finding would promote the development of hybrid dielectric transition materials with adjustable properties.
Single crystals of three new organic–inorganic hybrid compounds, tri[1-(diaminomethylene)uronium] hexachlorobismuthate ((C 2 H 7 N 4 S) 3 BiCl 6 ·H 2 O, HATU-BCH), bis[1-(diaminomethylene)uronium] pentabromobismuthate, ((C 2 H 7 N 4 S) 2 BiBr 5 , HATU-BB), and bis [3,5-diamino-1,2,4-thiadiazol-2-ium] pentaiodobismuthate ((C 2 H 5 N 4 S) 2 BiI 5 , OHATU-BI), have been successfully grown by slow evaporation method. Their structures were determined by single - crystal X-ray diffraction, in which all anion sublattice structures consist of hexahalobismuthates octahedra with different connection modes involving isolated, shared-corner, and shared-edge. The spectra characters were studied by Infrared and Raman spectra, which interpreted by calculation of the density functional theory (DFT) method and diffuse reflectance spectra. Thermal properties were characterized by thermal gravimetric analysis and differential scanning calorimetry.
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