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

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

De Novo Discovery of [Hdabco]BF₄ Molecular Ferroelectric Thin Film for Nonvolatile Low-Voltage Memories

To date, the field of ferroelectric random access memories (FeRAMs) is mainly dominated by inorganic ferroelectric thin films like Pb­(Zr,Ti)­O₃, which suffer from the issues of environmental harmfulness, high processing temperatures, and high fabrication costs. In these respects, molecular ferroelectric thin films are particularly advantageous and thus become promising alternatives to the conventional inorganic ones. For the prospect of FeRAMs applications, they should fulfill the requirements of effective polarization switching and low-voltage, high-speed operation. Despite recent advancements, molecular ferroelectric thin films with such high performance still remain a huge blank. Herein we present the first example of a large-area continuous biaxial molecular ferroelectric thin film that gets very close to the goal of application in FeRAMs: [Hdabco]­BF₄ (dabco = diazabicyclo[2.2.2]­octane). In addition to excellent film performance, it is the coexistence of a low coercive voltage of ∼12 V and ultrafast polarization switching at a significantly high frequency of 20 kHz that affords [Hdabco]­BF₄ considerable potential for memory devices. Particularly, piezoresponse force microscopy (PFM) clearly demonstrates the four polarization directions and polarization switching at a low voltage down to ∼4.2 V (with an ∼150 nm thick film). This innovative work on high-performance molecular ferroelectric thin films, which can be compatible with wearable devices, will inject new vitality to the low-power information field

Switchable Nonlinear Optical and Tunable Luminescent Properties Triggered by Multiple Phase Transitions in a Perovskite-Like Compound

A new perovskite-like inorganic–organic hybrid compound [Et₃(<i>n</i>-Pr)­P]­[Cd­(dca)₃] (<b>1</b>) (where [Et₃(<i>n</i>-Pr)­P]⁺ is the propyltriethylphosphonium cation and dca is a dicyanamide ligand) was discovered to undergo three reversible phase transitions at 270 K (<i>T</i>₁), 386 K (<i>T</i>₂), and 415 K (<i>T</i>₃), respectively. The variable-temperature single-crystal X-ray structural analyses reveal that these sequential phase transitions originate from the deformations of the [Cd­(dca)₃]⁻ frameworks and the concomitant reorientations of the [Et₃(<i>n</i>-Pr)­P]⁺ guest cations. It is found that <b>1</b> possesses a sensitive nonlinear optical (NLO) switching at <i>T</i>₂ with a large contrast of ∼40 within a narrow temperature range of ∼7 K. Furthermore, <b>1</b> shows intriguing photoluminescence (PL) property, and the PL intensity suffers a plunge near <i>T</i>₃. The multiple phase transitions, switchable NLO and tunable luminescent properties simultaneously exist in this inorganic–organic perovskite-like hybrid compound, suggesting its great potential application in molecular switches and photoelectric field