Symmetry Breaking Phase Transition, Second-Order Nonlinear Optical and Dielectric Properties of a One-Dimensional Organic–Inorganic Hybrid Zigzag Chain Compound [NH₃(CH₂)₅NH₃]SbBr₅

A new one-dimensional organic–inorganic material, 1,5-pentanediammonium pentabromoantimonate (III) (<b>1</b>), exhibits a centrosymmetric-to-non-centrosymmetric symmetry breaking phase transition at 366.5 K, showing a prominent second harmonic generation (SHG) response and dielectric anomalies. The differential scanning calorimetry results indicate the phase transition is a second-order one. The variable-temperature structural analyses reveal that the space group changes from <i>Pnma</i> at 393 K in the high-temperature phase to <i>P</i>2₁2₁2₁ at 293 K in the low-temperature phase, accompanied by the loss of a symmetry plane and inversion center. The crystal structure is composed of one-dimensional zigzag chains of corner-sharing SbBr₆ octahedra and 1,5-pentanediammonium cations. The origin of the phase transition can be attributed to both the deformation of the zigzag chains and the order–disorder transition of the 1,5-pentanediammonium cations. The compound is SHG-active below the transition temperature, demonstrating its second-order nonlinear optical properties. It is also SHG-inactive above the transition temperature, which further confirms the symmetry breaking phenomenon. These findings will pave a new way to explore organic–inorganic multifunctional phase transition material

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Reversible Phase Transition of 1,4-Diazoniabicyclo[2.2.2]octane-1-acetate-4-acetic Acid Chloride Trihydrate

1,4-Diazoniabicyclo­[2.2.2]­octane-1-acetate-4-acetic acid forms a complex (<b>1</b>) 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 (<b>2</b>) exhibit obvious change compared to those of <b>1</b>. The crystal structures of these two compounds, determined at 153 and 298 K, are all monoclinic in <i>P</i>2₁/<i>n</i>, 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

Structural Phase Transitions of a Layered Organic–Inorganic Hybrid Compound: Tetra(cyclopentylammonium) Decachlorotricadmate(II), [C₅H₉NH₃]₄Cd₃Cl₁₀

A layered organic–inorganic hybrid compound, tetra­(cyclopentylammonium) decachlorotricadmate­(II) (<b>1</b>), in which the two-dimensional [Cd₃Cl₁₀]^4–_<i>n</i> 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 <b>1</b> determined at 93, 298, and 343 K are solved in <i>P</i>2₁2₁2₁, <i>Pbca</i>, and <i>Cmca</i>, 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–_<i>n</i> network

Competitive Halogen Bond in the Molecular Ferroelectric with Large Piezoelectric Response

Molecular piezoelectrics are attracting tremendous interest because of their easy processing, light weight, low acoustical impedance, and mechanical flexibility. However, reports of molecular piezoelectrics with a piezoelectric coefficient <i>d</i>₃₃ comparable to piezoceramics such as barium titanate (BTO, 90–190 pC/N) have been scarce. Here, we present a uniaxial molecular ferroelectric, trimethylchloromethylammonium tribromocadmium­(II) (TMCM-CdBr₃), in which the halogen bonding might be a possible critical point for the stabilization of one-dimensional (1D) {CdBr₃}⁻ chain and further reservation of its ferroelectricity in such organic–inorganic hybrid crystalline systems. It has a large <i>d</i>₃₃ of 139 pC/N, 1 order of magnitude higher than those of most classically uniaxial ferroelectrics such as LiNbO₃ (6–16 pC/N) and Rochelle salt (∼7 pC/N), and comparable with those of multiaxial ferroelectrics such as BTO and trimethylbromomethylammonium tribromomanganese­(II) (112 pC/N). Moreover, the simple single-crystal growth and easy-to-find polar axis enable it to hold a great potential for applying in the single-crystal form. In light of the strong, specific, and directional halogen-bonding interactions, this work provides possibilities to explore new classes of molecular piezoelectrics and contribute to further developments