Two hybrids (C5H6N)CdCl3 (1) and (C5H6N)Cd2Cl5 (2) were synthesized by stoichiometric regulation of reactants. 1 with a one-dimensional chain-like structure shows a step-like dielectric anomaly at around 158 K. 2 with a layered structure undergoes a prominent phase transition in the vicinity of 182 K, accompanying obvious dielectric relaxation behavior in a broad temperature range. Systematic characterization, such as differential scanning calorimetry (DSC), single-crystal X-ray diffraction, and dielectric measurements, has demonstrated that the phase transitions of 1 and 2 are both attributable to the dynamic motion of the organic cation. Significantly, dimensionality modulation triggers the tunable dielectric responses in these two compounds. Thus, regulation of the phase transition temperature and dielectric responses in the various dimensions of the structure is a potentially effective method to construct tunable dielectric phase transition materials.

As a promising candidate for energy storage capacitors, antiferroelectric (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization versus electric field (P–E) hysteresis characteristics in contrast to ferroelectrics and linear dielectrics. However, antiferroelectricity has only been discovered in inorganic oxides and some hydrogen-bonded molecular systems. In view of the structural diversity and unique physical properties of organic–inorganic hybrid system, it remains a great opportunity to introduce antiferroelectricity into organic–inorganic hybrid perovskites. Here, we report that polarizable antiparallel dipole arrays can be realized in an organic–inorganic hybrid perovskite, (3-pyrrolinium)CdBr3, which not only exhibits an excellent ferroelectric property (with a high spontaneous polarization of 7.0 μC/cm2), but also presents a striking AFE characteristic revealed by clear double P–E hysteresis loops. To the best of our knowledge, it is the first time that such successive ferroelectric–antiferroelectric–paraelectric phase transitions have been discovered in organic–inorganic perovskites. Besides, a giant dielectric constant of 1600 even at high frequency of 1000 kHz and a bulk electrocaloric effect with entropy change of 1.18 J K–1 kg–1 under 7.41 kV/cm are also observed during the phase transition. Apparently, the combined striking AFE characteristic and giant dielectric constant make (3-pyrrolinium)CdBr3 a promising candidate for next generation high-energy-storage capacitors.

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.

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.

A layered perovskite-type organic–inorganic hybrid compound, NH3(CH2)5NH3MnCl4 (1), in which the 1,5-diaminopentane cation occupies the space enclosed by the MnCl6 octahedra, has been successfully synthesized. Systematic characterization methods including differential scanning calorimetry (DSC) measurements, dielectric measurements and variable-temperature structural analyses reveal that compound 1 undergoes a reversible phase transition at 298 K, accompanied by switchable dielectric responses between high and low states and remarkable anisotropy along the various crystallographic axes. Such distinctive dielectric performances mean that 1 could be regarded as a potential switchable dielectric material. Significantly, an intriguing orange emission band at 581 nm can be observed under ultraviolet excitation, which is ascribed to the octahedral Mn2+ ion. This finding may extend the application of organic–inorganic hybrids in the field of switchable dielectric materials.

A novel zigzag chain organic–inorganic hybrid compound of the general formula R2MI5, [n-C3H7NH3]2[SbI5] (1), was successfully synthesized, in which the n-propylammonium cations were located in the free cavities between the one-dimensional zigzag chains. Systematic characterization was performed to investigate the phase transition of 1. A pair of sharp peaks at 211.8 K (heating) and 203.7 K (cooling) with a hysteresis 8.1 K were observed in the differential scanning calorimetry (DSC) curve, indicating the first-order phase transition behavior of 1. The temperature dependence dielectric measurement demonstrated a step-like change at around 211.8 K, which makes 1 a potential switchable dielectric material. Frequency dependence measurement revealed that the frequency exerts a weak influence on the dielectric permittivity. Further structural analysis shows that both anionic and cationic moieties contribute to the phase transition, accompanied by weak hydrogen bond interactions between cations and the [SbI5]n2− chains.

A new organic–inorganic hexagonal perovskite-type compound with the formula ABX3, thiazolium tribromocadmate(II) (1), in which thiazolium cations are situated in the space between the one-dimensional chains of face-sharing CdBr6 octahedra, has been successfully synthesized. Systematic characterizations including differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements reveal that it undergoes two structural phase transitions, at 180 and 146 K. These phase transitions are accompanied by remarkable dielectric relaxation and anisotropy. The thiazolium cations remain orientationally disordered during the two phase transition processes. The origins of the phase transitions at 180 and 146 K are ascribed to the slowing down and reorientation of the molecular motions of the cations, respectively. Moreover, the dielectric relaxation process well described by the Cole–Cole equation and the prominent dielectric anisotropy are also connected with the dynamics of the dipolar thiazolium cations.

A novel organic–inorganic hybrid layered perovskite-type compound of the general formula A2BX4, bis(IBA)tetrabromolead(II) (1, IBA = isobutyl-ammonium cation), has been successfully synthesized and grown as flake-like crystals, and undergoes two reversible solid-state phase transitions at 315 K and 250 K, and has been systematically characterized using differential scanning calorimetry measurements, variable-temperature structural analyses, variable-temperature powder X-ray diffraction measurements and dielectric measurements. 1 exhibits a remarkable temperature-dependent dielectric behavior, which could be switched between high and low dielectric states above room temperature, and a broad peak exists below room temperature. The most striking dielectric property is the remarkable anisotropy along the various crystallographic axes. All of these demonstrate its potential application as a high temperature switchable molecular dielectric and low temperature phase transition material.

•One reversible phase transition supramolecular adduct is synthesized.•DSC measurement detected the phase transition point of 158 K.•Distinct dynamic behavior of the inorganic anion maybe the driving force for the phase transition.A new supramolecular adduct 4-trifluoromethoxyanilinium hexafluorophosphate-1,4,7,10,13,16-hexaoxacyclooctadecane ([C7H7NOF3–(18-crown-6)]+[PF6]−) was synthesized and separated as crystals. DSC measurement detected that this compound undergoes a reversible phase transition at about 158 K with a heat hysteresis of 4.8 K. The single crystal X-ray diffraction data obtained at 213 K and 113 K suggest that the phase transition undergoes from a high temperature phase with a space group of Pnma to a low temperature one with a space group of P21/n, the symmetry breaking occurs with an Aizu notation of mmmF2/m. The driving force of the transition may be ascribed to the order–disorder transformation of the inorganic PF6− anion. Broad peak dielectric anomaly observed at 157 K further confirms this phase transition.One reversible phase transition supramolecular adduct is synthesized. DSC measurement detected the phase transition point of 158 K. The single crystal X-ray diffraction data obtained at 213 K and 113 K suggest that the phase transition undergoes from a high temperature phase with a space group of Pnma to a low temperature one with a space group of P21/n. Distinct dynamic behavior of the inorganic anion maybe the driving force for the phase transition.

The one-dimensional organic–inorganic hybrid compound bis(cyclohexylammonium) tetrachlorocadmate(II) (1), in which the adjacent infinite [CdCl4]n– chains are connected to each other though Cd···Cl weak interactions to form perovskite-type layers of corner-sharing CdCl6 octahedra separated by cyclohexylammonium cation bilayers, was synthesized. It undergoes two successive structural phase transitions, at 215 and 367 K, which were confirmed by systematic characterizations including differential scanning calorimetry (DSC) measurements, variable-temperature structural analyses, and dielectric and second harmonic generation (SHG) measurements. A precise structural analysis discloses that the phase transition at 215 K is induced by the disorder–order transition of cyclohexylammonium cations, while the phase transition at 367 K derives from changes in the relative location of Cd atoms. Emphatically, both the dielectric constant and SHG intensity of 1 show a striking change between low and high states at around 367 K, which reveals that 1 might be considered as a potential dielectric and nonlinear optical (NLO) switch with high-temperature response characterization, excellent reversibility, and obvious change of states.

A layered organic–inorganic hybrid compound, tetra(cyclopentylammonium) decachlorotricadmate(II) (1), in which the two-dimensional [Cd3Cl10]4–n networks built up from three face-sharing CdCl6 octahedra are separated by cyclopentylammonium cation bilayers, has been discovered as a new phase transition material. It undergoes two successive structural phase transitions, at 197.3 and 321.6 K, which were confirmed by differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements. The crystal structures of 1 determined at 93, 298, and 343 K are solved in P212121, Pbca, and Cmca, respectively. A precise analysis of the structural differences between these three structures reveals that the origin of the phase transition at 197.3 K is ascribed to the order–disorder transition of the cyclopentylammonium cations, while the phase transition at 321.6 K originates from the distortion of the two-dimensional [Cd3Cl10]4–n network.

A new phase transition compound, 2-methoxyanilinium perchlorate-18-crown-6 (1) {(o-CH3OC6H4NH3)+(18-crown-6)·ClO4−}, has been synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show a pair of sharp peaks at 225 K (heating) and 210 K (cooling), indicating the phase transition is first-order. Dielectric anomalies observed at 225 K (heating) and 210 K (cooling) further confirm the phase transition. The crystal structures determined at 298 K and 123 K are both triclinic in P−1. The most distinct difference between room-temperature and low-temperature structures is the order–disorder transition of the host 18-crown-6 molecule, which is the driving force of the phase transition.The most distinct difference between room-temperature and low-temperature structures is the order–disorder transition of the host 18-crown-6 molecule, which is the driving force of the phase transition.

1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic acid forms a complex (1) with chloride ion and water molecule in the ratio 1:1:3. Differential scanning calorimetry (DSC) measurement shows a pair of reversible peaks at 210.7 K (heating) and 180.3 K (cooling) with a large heat hysteresis about 30.4 K, indicating this compound undergoes a reversible structural phase transition. Dielectric measurement further confirms the phase transition. The DSC and dielectric measurements results of its deuterated compound (2) exhibit obvious change compared to those of 1. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in P21/n, suggesting the phase transition is isosymmetric. Structural analysis reveals that the changes of the relative location of water molecules and chloride ions affect the formation of different modes of hydrogen-bonded anionic chains, leading to the reversible structural phase transition.

•Two five-coordinate complexes have been synthesized in HCl and HClO4 mediums.•The coordination geometries of complexes 1 and 2 are different.•Different structures lead to large discrepancy in dielectric properties.The reaction of 1-(chloromethyl)-4-aza-1-azonia-bicyclo[2.2.2]octane chloride and divalent metal copper chloride in dilute hydrochloric acid and perchloric acid mediums yields two five-coordinate copper (II) complexes, C7H16Cl4CuN2O (1) with trigonal–bipyramidal geometry and C14H28Cl6CuN4O8 (2) with novel square–pyramidal geometry respectively. Their crystal structures have been determined by X-ray crystallography at room temperature and low temperature. Dielectric constants of these two complexes increase with increasing temperature and decrease with increasing frequency when measured at different temperatures and frequencies. The complex 2 is more sensitive to diverse frequencies than complex 1 and also shows dielectric anomaly and corresponding dielectric loss behavior at 173 K as the result of the disorder–order transition of perchlorate anions.Two novel five-coordinate metal–organic–inorganic complexes Cu(LCH2Cl)Cl3H2O (1) and [Cu(LCH2Cl)2Cl2](ClO4)2 (2) (L+CH2Cl = N-chloromethyl-1,4-diazabicyclo[2.2.2]octonium ion) were prepared with two different geometries. Compound 1 displays 1D chain structure cross-linked by hydrogen bonds, compound 2 displays 0D layer structure with disorder–order transition of ClO4− anions at different temperatures. Different structures lead to large discrepancy in the frequency and temperature dependence of the dielectric constant measurements.

A novel zigzag chain organic–inorganic hybrid compound of the general formula R2MI5, [n-C3H7NH3]2[SbI5] (1), was successfully synthesized, in which the n-propylammonium cations were located in the free cavities between the one-dimensional zigzag chains. Systematic characterization was performed to investigate the phase transition of 1. A pair of sharp peaks at 211.8 K (heating) and 203.7 K (cooling) with a hysteresis 8.1 K were observed in the differential scanning calorimetry (DSC) curve, indicating the first-order phase transition behavior of 1. The temperature dependence dielectric measurement demonstrated a step-like change at around 211.8 K, which makes 1 a potential switchable dielectric material. Frequency dependence measurement revealed that the frequency exerts a weak influence on the dielectric permittivity. Further structural analysis shows that both anionic and cationic moieties contribute to the phase transition, accompanied by weak hydrogen bond interactions between cations and the [SbI5]n2− chains.

A novel organic–inorganic hybrid layered perovskite-type compound of the general formula A2BX4, bis(IBA)tetrabromolead(II) (1, IBA = isobutyl-ammonium cation), has been successfully synthesized and grown as flake-like crystals, and undergoes two reversible solid-state phase transitions at 315 K and 250 K, and has been systematically characterized using differential scanning calorimetry measurements, variable-temperature structural analyses, variable-temperature powder X-ray diffraction measurements and dielectric measurements. 1 exhibits a remarkable temperature-dependent dielectric behavior, which could be switched between high and low dielectric states above room temperature, and a broad peak exists below room temperature. The most striking dielectric property is the remarkable anisotropy along the various crystallographic axes. All of these demonstrate its potential application as a high temperature switchable molecular dielectric and low temperature phase transition material.

A layered perovskite-type organic–inorganic hybrid compound, NH3(CH2)5NH3MnCl4 (1), in which the 1,5-diaminopentane cation occupies the space enclosed by the MnCl6 octahedra, has been successfully synthesized. Systematic characterization methods including differential scanning calorimetry (DSC) measurements, dielectric measurements and variable-temperature structural analyses reveal that compound 1 undergoes a reversible phase transition at 298 K, accompanied by switchable dielectric responses between high and low states and remarkable anisotropy along the various crystallographic axes. Such distinctive dielectric performances mean that 1 could be regarded as a potential switchable dielectric material. Significantly, an intriguing orange emission band at 581 nm can be observed under ultraviolet excitation, which is ascribed to the octahedral Mn2+ ion. This finding may extend the application of organic–inorganic hybrids in the field of switchable dielectric materials.

A new organic–inorganic hexagonal perovskite-type compound with the formula ABX3, thiazolium tribromocadmate(II) (1), in which thiazolium cations are situated in the space between the one-dimensional chains of face-sharing CdBr6 octahedra, has been successfully synthesized. Systematic characterizations including differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements reveal that it undergoes two structural phase transitions, at 180 and 146 K. These phase transitions are accompanied by remarkable dielectric relaxation and anisotropy. The thiazolium cations remain orientationally disordered during the two phase transition processes. The origins of the phase transitions at 180 and 146 K are ascribed to the slowing down and reorientation of the molecular motions of the cations, respectively. Moreover, the dielectric relaxation process well described by the Cole–Cole equation and the prominent dielectric anisotropy are also connected with the dynamics of the dipolar thiazolium cations.