29 research outputs found
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>2<sub>1</sub>/<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>2<sub>1</sub>/<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>2<sub>1</sub>/<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>2<sub>1</sub>/<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), [C<sub>5</sub>H<sub>9</sub>NH<sub>3</sub>]<sub>4</sub>Cd<sub>3</sub>Cl<sub>10</sub>
A layered organic–inorganic
hybrid compound, tetra(cyclopentylammonium) decachlorotricadmate(II)
(<b>1</b>), in which the two-dimensional [Cd<sub>3</sub>Cl<sub>10</sub>]<sup>4–</sup><sub><i>n</i></sub> networks
built up from three face-sharing CdCl<sub>6</sub> 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>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub>, <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 [Cd<sub>3</sub>Cl<sub>10</sub>]<sup>4–</sup><sub><i>n</i></sub> 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>2<sub>1</sub>/<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>2<sub>1</sub>/<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>2<sub>1</sub>/<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]BF<sub>4</sub> 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)O<sub>3</sub>, 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]BF<sub>4</sub> (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]BF<sub>4</sub> 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 [Et<sub>3</sub>(<i>n</i>-Pr)P][Cd(dca)<sub>3</sub>] (<b>1</b>) (where
[Et<sub>3</sub>(<i>n</i>-Pr)P]<sup>+</sup> is the propyltriethylphosphonium
cation and dca is a dicyanamide ligand) was discovered to undergo
three reversible phase transitions at 270 K (<i>T</i><sub>1</sub>), 386 K (<i>T</i><sub>2</sub>), and 415 K (<i>T</i><sub>3</sub>), respectively. The variable-temperature single-crystal
X-ray structural analyses reveal that these sequential phase transitions
originate from the deformations of the [Cd(dca)<sub>3</sub>]<sup>−</sup> frameworks and the concomitant reorientations of the [Et<sub>3</sub>(<i>n</i>-Pr)P]<sup>+</sup> guest cations. It is found
that <b>1</b> possesses a sensitive nonlinear optical (NLO)
switching at <i>T</i><sub>2</sub> 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><sub>3</sub>.
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