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Advances and Property Investigations of an Organic–Inorganic Ferroelectric: (diisopropylammonium)2[CdBr4]
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Advances and Property Investigations of an Organic–Inorganic Ferroelectric: (diisopropylammonium)2[CdBr4]
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Inorganic Chemistry

Cite this: Inorg. Chem. 2020, 59, 17, 11986–11994
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https://doi.org/10.1021/acs.inorgchem.0c00830
Published August 15, 2020

Copyright © 2020 American Chemical Society. This publication is licensed under CC-BY.

Abstract

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The preparation of materials featuring more than one ferroelectric phase represents a promising strategy for controlling electrical properties arising from spontaneous polarization, since it offers an added advantage of temperature-dependent toggling between two different ferroelectric states. Here, we report on the discovery of a unique ferroelectric–ferroelectric transition in diisopropylammonium tetrabromocadmate (DPAC, (C6H16N)2[CdBr4]) with a Tc value of 244 K, which is continuous in nature. Both phases crystallize in the same polar orthorhombic space group, Iab2. The temperature-resolved second-harmonic-generation (SHG) measurements using 800 nm femtosecond laser pulses attest to the polar structure of DPAC on either side of the phase transition (PT). The dc conductivity parameters were estimated in both solid phases. The anionic substructure is in the form of [CdBr4]2– discrete complexes (0D), while in the voids of the structure, the diisopropylammonium cations are embedded. The ferroelectric properties of phases I and II have been confirmed by the reversible pyroelectric effect as well as by P–E loop investigations. On the basis of the dielectric responses, the molecular mechanism of the PT at 244 K has been postulated to be of mixed type with an indication of its displacive nature.

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Synopsis

A novel ferroelectric crystal of (C6H16N)2[CdBr4] has been synthesized, and a description of its properties (thermal, structural, electric, second-harmonic generation) is presented. The ferroelectric properties in phases I and II have been successfully confirmed by the reversible pyroelectric effect as well as by P−E hysteresis loop investigations and SHG properties.

Introduction

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Organic–inorganic hybrid materials have received significant attention not only because of the rich diversity of crystal structures they adopt but also because these systems can be fine-tuned to obtain desirable properties such as light emission, (1−6) semiconductivity, (1,3,7) dielectric switching, (8−11) ferroelectricity, (12,13) and multiferroism. (4−6,14,15) These effects are associated with unique combinations of organic and inorganic components in which usually polar organic cations occupy the voids within the inorganic frameworks. Materials of this type can be therefore understood in terms of host–guest chemistry, in which the host inorganic framework constitutes the defining environment for the rotationally and/or translationally labile guest.
Halometalates stand out as a unique group of stimulus-responsive hybrids, since the organic component is usually more sensitive to the external stimuli, such as temperature and electric or magnetic field strength, resulting in solid to solid structural changes. (16) The behavior, as mentioned above, is typical for both p- and d-block halometalates. Indeed, among the former (and smaller) group one notes a growing body of research on halogenoantimonate(III) (17−20) and halogenobismuthate(III) (17,21−27) networks, while the latter group encompasses a much broader family of halometallates based on divalent or trivalent 3d transition metals. For 3d transition metals, two basic types of stoichiometries can be distinguished: i.e., the tetrahedral building blocks, with a general formula of A2BX4, and edge-sharing or face-sharing ABX3 coordination polymers. Such structures include a large class of hybrids (wherein A = monovalent or divalent organic cation; B = Mn, Fe, Co, Cd, Mn, Cu, Sn, Pb; X = Cl, Br, I), (28−30) with some of them displaying excellent electronic and photoluminescent properties. (31−34)
Technologically relevant properties such as ferroelectricity, semiconductivity, and switching between individual dielectric states are determined primarily by changes in the dynamics of the polar cation near the phase transition (PT) temperature. However, a properly formed anionic subnet favors the creation of the stimuli-responsive organic–inorganic hybrids. As shown in Scheme 1, depending on the synthetic route, one can obtain systems in which halometalates of Cd-X (X = Cl, Br, I) are tetrahedral zero-dimensional (0D) clusters, (2,10,31−34) one-dimensional linear (1DL) (7,16,35−42) or zigzag (1DZ) chains, (43−45) and two-dimensional (2D) grids. (46−51)

Scheme 1

Scheme 1. Schematic Projection of Inorganic Structures Adopted by Ferroelectric Halocadmates
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Recently, increased interest in the hybrids based on the halo-Cd complexes has been observed due to their photoluminescent properties. (1−3) Specifically, these materials exhibit white-light (WL) emission, rendering them as suitable potential light sources for solid-state-lighting (SSL) applications. Also, some representatives of halogenocadmate(II) hybrids display semiconducting properties, making them applicable in color lighting or displays. (3,7)
If one looks more closely at the currently available library of ferroelectric halocadmates (vide infra, Table 1), it is apparent that ferroelectricity was found for each type of structure dimensionality that these compounds can attain. Nevertheless, one structure–property motif is persistent across all of them: namely, 1DL linear halocadmate chains most frequently reveal ferroelectric behavior, while 0D discrete complexes and 2D grids are less often ferroelectric. Quite remarkably, irrespective of the structure dimensionality, all known ferroelectric halocadmates feature a phase transition between noncentrosymmetric and centrosymmetric space groups (i.e., a transition of ferro-paraelectric type), whereas none of them contains more than one ferroelectric phase.
As a part of our studies aimed at the design of room-temperature ferroelectrics, we have synthesized a novel organic–inorganic hybrid, (C6H16N)2[CdBr4] or DPAC, whose phase behavior is unique among halocadmates since the structural phase transition (PT) occurs between two polar phases, both of which possess excellent ferroelectric properties. Accordingly, this paper is devoted to the characterization of high (I)- and low-temperature (II) phases of DPAC with a particular focus being placed on the exploration of the noncentrosymmetric setting and the ferroelectric property itself. X-ray crystallography and temperature-resolved second-harmonic-generation (TR-SHG) techniques were employed to provide complementary evidence on the acentric structure of both phases. In turn, the ferroelectric nature of phases I and II was evidenced from the pyroelectric investigations and, above all, from the polarization vs electric field (P–E) hysteresis loop measurements. The complex dielectric permittivity measurement led to the determination of a correlation between the microscopic structures and the dielectric relaxation in the investigated phases, while DC measurements allowed us to reveal the semiconducting properties of DPAC in the high-temperature range.

Experimental Section

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Synthesis

Concentrated hydrobromic acid (48% Sigma-Aldrich) was added dropwise to a suspension of CdCO3 (98% Sigma-Aldrich, 3.45 g, 20 mmol) in 10 mL of water. Then diisopropylamine (≥99.5%, Sigma-Aldrich, 4.04 g, 40 mmol) was added dropwise to the solution. By slow evaporation at room temperature, colorless needle crystals of (C6H16N)2[CdBr4] (DPAC) were obtained. The composition of the compound was confirmed by elemental analysis. Anal. Found (calcd): C, 22.42 (22.65), N, 4.15 (4.40); H, 4.98 (5.07).

Thermal Analysis

DSC measurements were performed by heating and cooling of the polycrystalline sample in the temperature range of 200–298 K with a ramp rate of 10 K min–1 using a Mettler Toledo DSC3 instrument. The TGA/DTA measurements were performed on a Setaram SETSYS 16/18 instrument between 290 and 900 K with a ramp rate of 5 K min–1. The scan was performed under flowing nitrogen (flow rate 1 dm3 h–1). The melting point was measured with a scanning rate of 10 K min–1 using an Opti-Melt MPA-100 instrument in the temperature range from 300 to 480 K. Optical microscopy observations were carried out by using an Olympus BX53 apparatus combined with a LINKAM THM-600 heating/cooling stage, where the temperature was stabilized with an accuracy of 1 K.

Crystal Structure Determination

A suitable crystal was cut from a larger one harvested from the mother liquor. The data collection was performed at room temperature and then for the same crystal at 100 K. The structures were solved routinely with SHELXS and refined with SHELXL-2017. As the space group allows a free origin of the coordinate system along the c axis, the z coordinate of the Cd atom was kept fixed at 0.25 to facilitate an analysis of molecular shifts. All ordered non-H atoms were refined anisotropically and the disordered atoms isotropically, and the positions and U factors of H atoms were constrained. The C–C and C–N distances, as well as the valence angles in the disordered diisopropylammonium cations, were restrained. The data collection and refinement details are presented in Table S1 in the Supporting Information.

Electrical Measurement

All electrical measurements were performed on polycrystalline samples in the form of pressed pellets with various geometrical parameters (S = 20–25 mm2, d = 0.8–0.4 mm). The complex dielectric permittivity was measured between 200 and 360 K by an Agilent E4980A Precision LCR Meter in the frequency range of 135 Hz to 2 MHz. The electric measurements were carried out under a controlled atmosphere (N2). The overall errors for the real and imaginary parts of the complex dielectric permittivity were less than 5% and 10%, respectively. The DC conductivity and pyroelectric properties were tested with a Keithley 6517D electrometer/high-resistance meter between 200 and 360 K, with a temperature ramp of 2 K min–1. The ferroelectric hysteresis loops of a polycrystalline powder were obtained by using a modified Sawyer–Tower circuit at a frequency of 50 Hz. The surfaces of the pellet were coated with silver conductive paint (Electron Microscopy Sciences, 503).

Second-Harmonic Generation (SHG)

SHG studies were performed using a Quantronix Integra-C regenerative amplifier operating at 800 nm wavelength. This instrument delivers laser pulses of ∼130 fs length and operates at a repetition rate of 1 kHz with an average power of up to 1 W. Prior to measurements, single crystals of DPAC and potassium dihydrogen phosphate (KDP, used as a reference for the Kurtz–Perry test) were crushed with a spatula and sieved through a mini-sieve set (Aldrich), collecting a microcrystal size fraction of 88–125 μm. Next, size-graded samples of DPAC and KDP were fixed between microscope glass slides (forming tightly packed layers) that were sealed and mounted to the holder. The laser beam was directed onto samples at 45° and was unfocused in all cases. Signal-collecting optics, mounted to the glass optical fiber, was placed perpendicularly to the plane of the sample (backscattering geometry). Scattered pumping radiation was suppressed with the use of a 700 nm short-pass dielectric filter (FESH0700, Thorlabs). The attenuation of laser beam intensity was performed with the use of a Glan polarizer. All emission spectra were recorded with an Ocean Optics QE Pro-FL spectrograph. A temperature-resolved SHG (TR-SHG) study (from 287 to 235 K) was conducted using a 800 nm beam with a mean power of 120 mW. In this experiment, the sample was mounted to a custom-made staged Peltier cooling system equipped with an external thermocouple. Spectra were collected for 1000 ms at each temperature point and were averaged five times. The assessment of the SHG efficiency of DPAC at 295 K was performed with the use of the Kurtz–Perry technique using KDP as a reference. (52,53) A Kurtz–Perry test was performed using an 800 nm laser beam with a mean power of 320 mW. Spectra were collected for 200 and 2000 ms for KDP and DPAC, respectively (averaged five times).
Caution! Work with the high-power laser is dangerous to the eyes, especially in the spectral range in which the beam is invisible. Adequate eye protection should be used during measurements.

Results and Discussion

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Thermal Properties

DPAC crystals are stable on exposure to the air up to about 393 K (Figure S1 in the Supporting Information). Beyond this temperature point, a solid to semiliquid PT was observed. This transition also was proven by the melting point measurement (Figure S2a in the Supporting Information) and by the observation of a single crystal under a polarized light microscope (Figure S2b in the Supporting Information). The DSC thermal analysis reveals the presence of one reversible solid to solid PT at 244 K (Figure 1) with a continuous nature. A small value of ΔHPT and a calculated value of ΔSPT equal to ca. 0.5 J/(mol K) suggest a “displacive” mechanism of this structural transformation. Figure S2c in the Supporting Information presents the DSC diagram in the temperature range 150–450 K.

Figure 1

Figure 1. DSC runs obtained upon heating and cooling scans for DPAC (sample mass m = 5.812 mg). Black arrows show the directions of runs (cooling or heating at 10 K/min).

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Crystal Structures

An analysis of the variable-temperature single-crystal structure reveals an isostructural PT at 244 K. Therefore, the investigations were performed at 100 (phase II) and 293 K (phase I). In both phases, DPAC crystallizes in the orthorhombic space group Iba2. The basic unit of the crystal is composed of one CdBr4 anion and two disopropylammonium cations (DPA+) giving an overall A2BX4 stoichiometry (see Figure 2a). The Cd ion has a tetrahedral coordination geometry with four adjacent Br atoms. The DPA+ cations are linked by weak N–H···Br hydrogen bonds with N···Br distances of 3.41–3.64 and 3.38–3.56 Å in phases I and II, respectively (see Table S2 in the Supporting Information). In both phases, the [CdBr4]2– anions are ordered. As it goes over from phase I to II, the anion rotates approximately around the Cd–Br1 axis; the magnitude of the rotation is about 33° (Figure 2b). The diisopropylammonium cations (types N1 and N2) in phase I are ordered, whereas type N3 is characterized by an enhanced temperature displacement, which may indicate its dynamic disorder. The N1 and N3 atoms are located on 2-fold axes. When the crystal is cooled, the cations undergo the transformations displayed in Figure 2b–e.

Figure 2

Figure 2. (a) Crystal packing of phase II of DPAC viewed along the a axis. Movements of the component ions on going from phase I (red atoms and bonds) to phase II (blue or green atoms and bonds; for the sake of clarity only the nitrogen and cadmium atoms have been labeled). (b) Rotation of [CdBr4]2–. The anion from phase I has been shifted so that both Cd atoms overlap. (c) Rotation of the N1 cation along the [100] direction. (d) Transformation of the N2 cation. The (001) plane is perpendicular to the diagram and the N2–N2 direction. (e) Transformation of the N3 cation. The superscript i denotes a −x, −y, z symmetry operation; the [010] direction runs vertically.

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In phase II, all organic cations become ordered in terms of a dynamic point of view. Cations of types N1 and N2 change their position in the lattice; the cation N1 as a hole rotates by 180° around the [100] direction (Figure 2c), whereas N2 rotates approximately by 65° around the [120] direction; the rotation angle is defined here as the N–X–C angle at both temperatures (Figure 2d), where XC is the geometric center of the two C atoms bonded to N and, in that, with N3 the nitrogen atom slips off from the 2-fold axis. Cations of type N3 in phase II are now ordered. However, they are statistically distributed between two positions to 50% occupancies (Figure 2e). These positions are related to each other by a rotation of 87° around the [010] direction. This results in the bisector of the H–N–H angle, which probably shows the direction of the most significant contribution to the dipole moment of the diisopropylammonium cation, parallel to the [001] direction at room temperature, becoming approximately oriented along the [100] direction. Additionally, in the N2 and N3 cations, the isopropyl groups rotate around the N–C bonds (approximately by 120°).

Second-Harmonic-Generation (SHG) Effect

The noncentrosymmetric character of phases I and II of DPAC is strongly suggested by the X-ray diffraction data, but to gain a complete body of evidence on the polarity of both of these phases, we turned to the temperature-resolved second-harmonic-generation (TR-SHG) technique. To do this, we irradiated a size-graded powder of DPAC (88–125 μm) with 800 nm femtosecond laser pulses of 120 mW mean power from 287 to 235 K with 2–3 K steps. Figure 3 displays integral intensities of collected SHG signals plotted as a function of temperature; experimental spectra of the SHG response are presented in Figures S3 and S4 in the Supporting Information. It is apparent that upon cooling the SHG signal gradually decreases down to 244 K, at which point it increases in intensity due to the transition to the low-temperature phase I. The downward shift in the integral intensities of the SHG signal, as the cooling progressed, can be attributed to some contribution of laser-induced bleaching of the sample. We have also estimated the relative SHG efficiency for a powdered sample in phase I, with the use of the Kurtz–Perry powder test. (52,53) This test (see spectra of the produced second harmonic of radiation in Figure S5 in the Supporting Information) shows that phase I emits a SHG that is approximately 2 orders of magnitude weaker than that found for KDP of the same particle size (0.013 that of KDP at 295 K). When they are taken as a whole, the collected results confirmed our notion that phases I and II both feature a noncentrosymmetric setting, thus fulfilling the necessary structural prerequisite for ferroelectricity.

Figure 3

Figure 3. Plot of the integral intensity of the SHG signal of DPAC between 235 and 287 K measured on cooling.

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Electric Properties

In order to gain information concerning the dynamics of the diisopropylammonium cation, dielectric measurements have been undertaken (Figures 4a,b). In the vicinity of the transition point at 244 K, only a slight change in the slopes of the ε′ vs T has been found (see inset in Figure 4a). On the other hand, the significant differences in the dielectric responses regarding relaxation processes between phases I and II should be noted (Figure 4b). In the temperature range between 244 and 300 K, a pronounced, well-shaped dielectric relaxation process is observed, which can be ascribed to the displacement of the diisopropylammonium cation (N3) giving the dipole moment projections on the c as well as the a direction. The frequency dependences of the real part, ε′, and the imaginary part, ε′′, of dielectric permittivity measured for both phases I and II at several temperatures are presented in Figure S6 in the Supporting Information. Moreover, in phase I (T > 244 K) a significant contribution of the electric conductivity is apparent, while after the transition from phase I to the semiliquid phase this effect is dominant (see Figure S7 in the Supporting Information).

Figure 4

Figure 4. Temperature dependence of the real (a) and imaginary (b) parts of the complex electric permittivity, ε* = ε′ – iε′′, at selected frequencies in the vicinity of PT at 244 K for the polycrystalline sample of DPAC. A dotted line indicates the PT temperature. Inset: ε′ measured at 2 MHz. (c) Arrhenius plot for the macroscopic dielectric relaxation time, ln τ vs 1/T, for DPAC in phase I (red circles) and in phase II (blue circles).

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Below the PT temperature, another dielectric anomaly with significantly lower frequency dispersion has been found (see Figure S6 in the Supporting Information). The dielectric response of DPAC is well described by using the four-parameter Cole–Cole function (54)
(1)
where ε0 and ε∞ are the low- and high-frequency limits, respectively, ω is the angular frequency, τ is the macroscopic relaxation time, and α represents the relaxation time distribution parameter. Table S3 in the Supporting Information contains the fitting parameters of the Cole–Cole equation at selected temperatures. The macroscopic relaxation times (τ) are presented in Figure 4c, as a logarithmic plot of τ vs reciprocal temperature, 1/T (Arrhenius plot). It should be noted that the Arrhenius relationship is well obeyed, which indicates that the reorientations of molecules are thermally activated. The estimated activation energy (Ea) value for DPAC is equal to 63 (0.66 eV) and 30 (0.31 eV) kJ/mol for phases I and II, respectively. The dielectric response in both phases is strongly diffused—the α values are almost always larger than 0.2. It is surprising that the activation energy Ea for phase I is twice as large as that for phase II. This proves that the dynamics of organic components in phase II is quite different from that in phase I. Since the macroscopic relaxation time (τ) in phase I is longer than that in phase II, and the Ea value is much higher for phase I, some contribution of the long-range interactions between organic cations in phase I may be expected.
The preliminary measurements of the pyroelectric current, Ipyro, for a single crystal of DPAC show that, first, the pyroelectric current does appear at the PT temperature and, second, it is reversible with temperature (Figure S8a in the Supporting Information) on cooling/heating. The sample was not polarized before the experiment. Due to the rather sensitive nature of the crystals, an application of an external electric field, even at values as low as 50–100 V, resulted in a breakdown of the sample. Nevertheless, the characteristic temperature dependence of Ipyro clearly indicates the change of the spontaneous polarization, ΔPs at 244 K (the PT temperature). Consequently, more detailed studies on ΔPs have been undertaken. Namely, we decided to apply an external electric field to the polycrystalline sample (pellets) in order to check whether the polarization direction can be reversed. This experiment was performed in such a way that the sample was first polarized in the low-temperature phase II (220 K) and then heated above 244 K. After 1/2 h of shorting the sample, the pyroelectric current was measured on the cooling run. The results of the pyroelectric current measurements are presented in Figure S8b, whereas Figure 5a shows the temperature dependences of ΔPs calculated from the equation
(2)
where S is a contact area of the sample (in this case of the polycrystalline pellet).

Figure 5

Figure 5. (a) Temperature dependence of Ptotal and ΔPs after poling by an external electric field (+10 kV/cm, red line; −10 kV/cm, blue line). (b) P–E hysteresis loops obtained at 215 K in phase II.

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It should be emphasized that, in the pyroelectric experiment, we can measure only a change in the polarization value, ΔPs; this is why its value at 220 K in Figure 5a is equal to 0. From the hysteresis loop observation, it is obvious that at even lower temperature (215 K) the Ps value is still equal to at least 0.11 μC/cm2. In order to determine the origin of the Ipyro peak (extrinsic or intrinsic nature), the measurements were repeated at different temperature ramp rates (according to ref (55)). Since the sample was in a polycrystalline form, the extrinsic Ipyro may be due to the thermally stimulated free charge carriers, and consequently, the broadening of the peak and an increased background, as well as a look only at the Ipyro ramp-rate dependence, one may assume an extrinsic origin of the aforementioned effects. As we can see in Figure S9 in the Supporting Information, an integral exclusively of the Ipyro peak, observed at 244 K, does not change with the cooling rate, which confirms its intrinsic origin. This means that the value of ΔPs does not depend on the temperature ramp rate; it is always the same spontaneous polarization value.
In order to confirm the ferroelectric properties of phases I and II of DPAC, P–E hysteresis loop measurements were performed. The P–E hysteresis loop at 215 K in phase II is displayed in Figure 5b while that at 298 K (phase I) is given in Figure S10a in the Supporting Information. It is apparent that the polarization can be switched under an ac voltage, 10 kV at 50 Hz ac. DPAC also displays a considerable Ps value of 0.11 μC/cm2 in phase II (215 K). As was shown in Figure S10b in the Supporting Information, the polarization decreases with a decrease in temperature. As was also pointed out in the SHG and X-ray crystallography sections, DPAC is polar in both phases, I and II. It follows that a change in the spontaneous polarization value, ΔPs, also above Tc close to the PT, should be observed. However, we were not able to record well-shaped rectangular P–E hysteresis loops for phase I of DPAC (Figure S10a in the Supporting Information), perhaps due to the significantly higher dielectric losses in comparison to those in phase II and/or a significant contribution of the electric conductivity. It should be emphasized that the hysteresis loop measurements were performed for the polycrystalline samples. Unfortunately, as noted earlier, a further increase in the electric field in order to saturate P–E hysteresis led to a breakdown of the sample; hence, the results presented reflect only the resulting value of ΔPs and as such should be treated only qualitatively as a confirmation of the polarity of phases II and I of DPAC. Nevertheless, the presence and reversibility of ΔPs, despite its small value, undoubtedly indicate ferroelectricity in both phases of DPAC.
We now comment on the effect of the structures of the determined phases on their polar properties. On the basis of the crystal structure data, the unit cells were constructed with the assumption that the positive charge of [C6H16N]+ and the negative charge of [CdBr4]2– reside on the N atoms and Cd atoms, respectively. According to the point electric charge model (presented in Tables S4 and S5 in the Supporting Information) the center coordinate of negative charge is [0.5,0.5,0.5] in both phases. Meanwhile, the center coordinates of the positive charge are [0.5,0.5,0.43] and [0.5,0.5,0.512], giving the Ps values 2.01 and 0.39 μC/cm2 for phases I and II, respectively. In both phases, all dipole moments of the cations, denoted N1–N3, contribute to the resultant spontaneous polarization vector in the crystal lattice. During the transformation, the positions of all cations change significantly with respect to CdB42–, which consequently leads to a reduction in the resultant dipole moment and consequently the Ps value. However, a change in the N3 cation dynamics has the greatest effect on the polarity change in the DPAC crystal. As we can see in Scheme 2, in phase I the N3 cation is characterized by an increased temperature displacement in either the [100] or [001] direction, as evidenced by the increased C–N–C angle (145.7°) in comparison to the cation N1 (121.1°) or N2 (119.8°). As was motioned above, upon cooling, the N3 cation rotates around the b axis by 87° and becomes approximately oriented along the a axis. In addition, the cation assumes two positions with 50% occupancies, resulting in an almost antiparallel orientation of the dipole moment. However, the dipole moments of the N3 cation are oriented by an angle of 3° relative to the a axis, which means that its projection on the polar c axis is much smaller than in the case of phase I. This is also evidenced by the change in the center coordinate of the positive charge of N3 from [0.5,0.5,0.31] calculated for phase I to [0.5,0.5,0.495] in the case of phase II. Therefore, the spontaneous polarization values in phase II have been postulated to decrease.

Scheme 2

Scheme 2. Packing Diagram of Organic (C6H16N)+ Cations Viewed along the a Axis with Schematically Marked Dipole Moments
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So far, the data collected in Table 1 suggest that, in the case of the hybrids based on Cd-X metallohalides, ferroelectric properties are more often observed in the coordination polymers (predominantly 1D) than in the 0D structures. Also, depending on the type of anion network architecture, for the ABX3 crystals, larger values of Ps are observed in comparison to those for the A2BX4 crystals. During the PT, the DPAC crystal still reveals ferroelectric properties. However, the decrease in the Ps value in phase II is related to the mutual displacement in the 244 K PT of the cationic network with respect to the anionic network. The experimental polarization values at 100 and 300 K are significantly smaller than those estimated on the basis of a theoretical approach; the estimated Ps value at 300 K is 2.30 μC/cm2, and at 100 K it equals 0.39 μC/cm2. The differences between the measured and theoretical values are most likely due to the fact that the sample was examined in the form of a polycrystalline pellet, which always causes a smaller Ps value in comparison to that for a single crystal oriented along the polar axis. A similar relationship was observed in the isostructural crystal (diisopropylammonium)2[MnBr4]. (56) In the analogue with Mn(II), the registered loops were also unsaturated, and the measured values (3.3 μC/cm2) were much smaller than the theoretical values calculated on the basis of a simple point electric charge calculation (8.72 μC/cm2), despite the fact that the measurements were made on a single crystal.
Table 1. Compilation of the Most Important Parameters Characterizing Structural and Spontaneous Polarization Properties for Ferroelectric Halocadmates of CdX3 and CdX4 (X = Cl, Br, I) Stoichiometriesa
FormulaTPT (K) cool/heatPT ordertypesymmetry changePs (μC/cm2)ref
(PD)[CdCl3]198/218first1DL-1DL-1DLC2/c ↔ Cmc21 ↔ Cmcm3.6 (210 K) (36)
 240/241second    
(PL)[CdCl3]316second1DL-1DLCmc21 ↔ Cmcm5.1 (253 K) (37)
(PL)[CdBr3]235/238second1DL-1DL-1DLCmc21 ↔ C2/m11 ↔ Cmcm5.65 (223 K) (38)
 244/247second    
(CPA)[CdCl3]285/300first1DL-1DLCc ↔ Cmcm1.7 (280 K) (39)
(CPA)2[CdBr4]338/340second0D-0DPnam ↔ Pna210.57 (293 K) (31)
(CHA)2[CdCl4]212/215second2D-1DZ-1DLCm ↔ Cmc21 ↔ I22210.79b (173 K) (43)
 349/367first  15.95b (298 K)
(TMA)[CdBr3]162/182first1DL-1DLP61 ↔ P63/m0.12 (125 K) (40,57,58)
(TMC)[CdCl3]390/400first1DL-1DLCc ↔ P63/mmc6.2 (397 K) (41)
(TMC)[CdBr3]341/346second1DL-1DLP63mc ↔ P63/mmc3.5 (298 K) (42)
(TMP)[CdCl3]346/348second1DL-1DLP63 ↔ P63/m ↔ P63/m0.43 (323 K) (59)
 387second    
(PEA)2[CdI4]297/301second0D-0DP21 ↔ P21/m0.20 (270 K) (60)
(DPA)2[CdBr4]242/244second0D-0DIab2 ↔ Iab20.11? (2.01b) (215 K)c
a

Abbreviations: PD, pyrrolidinium; PL, 3-pyrrolinium; CPA, cyclopentylammonium; CHA, cyclohexylammonium; TMA, tetramethylammonium; TMC, trimethylchloromethylammonium; DPA, diisopropylammonium; PEA, 2-phenylethylammonium; TMP, tetramethylphosphonium, first, first-order PT, second, second-order PT; 0D, zero-dimensional clusters; 1DL, one-dimensional linear chains; 1DZ, one-dimensional zigzag chains; 2D, two-dimensional grids.

b

Theoretical calculation.

c

This work.

Figure 6 shows the results of the direct current conductivity, σdc, for the polycrystalline DPAC plotted vs reciprocal temperature, 1/T. A small change in σdc is observed at the 244 K PT. However, above 393 K, the conductivity increases significantly. This increase is associated with the transition from the solid to the semiliquid phase of DPAC. The estimation of the activation energy, Ea, in the temperature range 250–400 K, according to the Arrhenius relationship
(3)
where R is a gas constant and σo is the conductivity for T → ∞, shows that Ea differs for phases I and II and equals 97 (0.99 eV) and 84 (0.87 eV) kJ/mol for phases I and II, respectively. In phase I, particularly above room temperature, the DPAC crystal shows semiconducting properties and σdc approaches a value on the order of 10–5 S/m.

Figure 6

Figure 6. dc conductivity, σdc, for DPAC plotted versus reciprocal temperature, 1000/T.

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Conclusion

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In summary, we have successfully demonstrated a novel rare example of a ferroelectric with an A2BX4 stoichiometry, which exhibits an isostructural PT at 244 K. Phases I and II both possess polar properties. The acentricity of these phases was confirmed by SHG measurements, while their polarity was confirmed by the polarization reversal process, in both the pyroelectric effect and hysteresis loop measurements, triggered by an application of an external electric field. In the crystal structure of DPAC there are zero-dimensional (0D) clusters with [CdBr4]2– tetrahedral units. On the basis of both the crystallographic analysis and DSC results, i.e. a slight change in the PT entropy (0.58 J/(mol K)), the structural mechanism of PT is ascribed to be of a mixed type with an indication of a displacive nature. From a structural standpoint, the transition is dominated by the change in dynamics and orientation of diisopropylammonium cations. In the case of the low-temperature phase II the overall arrangement of organic cations generates the spontaneous polarization of 0.11 μC/cm2 as determined from P–E hysteresis loop measurements. The determination of ferroelectric properties for both phases of DPAC raises hopes that compounds featuring an analogous set of polar properties, but with higher values of spontaneous polarization, may be seen as candidate compounds for application in micro- and nanoelectronics, batteries, and energy storage as well as in photovoltaics. Accordingly, the primary thrust of future work is to explore other representatives of the 0D halocadmate family with A2BX4 stoichiometry.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c00830.

  • TGA-DTA results, crystallographic data, hydrogen bonding interaction data, SHG spectra, and calculation of spontaneous polarization Ps (PDF)

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CCDC 1991347–1991348 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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Author Information

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Acknowledgments

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The authors are grateful for financial support from the Plenipotentiary of the Government of the Republic of Poland at the JINR in Dubna under Project No. 75/23/2020. J.K.Z. and A.C. acknowledge financial support from the Wroclaw University of Science and Technology.

References

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This article references 60 other publications.

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    Wei, Z.; Liao, W. Q.; Tang, Y. Y.; Li, P. F.; Shi, P. P.; Cai, H.; Xiong, R. G. Discovery of an Antiperovskite Ferroelectric in [(CH3)3NH]3(MnBr3)(MnBr4). J. Am. Chem. Soc. 2018, 140 (26), 8110– 8113,  DOI: 10.1021/jacs.8b05037
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    12
    Discovery of an antiperovskite ferroelectric in [(CH3)3NH]3(MnBr3)(MnBr4)
    Wei, Zhenhong; Liao, Wei-Qiang; Tang, Yuan-Yuan; Li, Peng-Fei; Shi, Ping-Ping; Cai, Hu; Xiong, Ren-Gen
    Journal of the American Chemical Society (2018), 140 (26), 8110-8113CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    It is known that perovskites with the general chem. formula of ABX3 (A, B = cations, X = anion) have been intensively studied over the last half century because of their diverse functional properties, such as ferroelectricity in BaTiO3, piezoelectricity in PZT (lead zirconate titanate), and recently developed photovoltaic properties in CH3NH3PbI3. However, rather less attention has been paid to their "inverse" analogs, antiperovskites, which have a chem. formula X3BA, where A and B are anions and X is a cation. Although most of important ferroelecs. are perovskites, no antiperovskite ferroelecs. have been found since the discovery of antiperovskites in 1930. Here, for the first time, we report a X3BA antiperovskite ferroelec. [(CH3)3NH]3(MnBr3)(MnBr4) (where (CH3)3NH is X, MnBr3 is B, and MnBr4 is A), which shows outstanding ferroelectricity with a significantly high phase transition temp. of 458 K as well as fascinating photoluminescence properties with two intense emissions. This finding opens a new avenue to explore the golden area of antiperovskites for high-performance functional materials.
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  13. 13
    Li, P. F.; Liao, W. Q.; Tang, Y. Y.; Ye, H. Y.; Zhang, Y.; Xiong, R. G. Unprecedented Ferroelectric-Antiferroelectric-Paraelectric Phase Transitions Discovered in an Organic-Inorganic Hybrid Perovskite. J. Am. Chem. Soc. 2017, 139 (25), 8752– 8757,  DOI: 10.1021/jacs.7b04693
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    13
    Unprecedented ferroelectric-antiferroelectric-paraelectric phase transitions discovered in an organic-inorganic hybrid perovskite
    Li, Peng-Fei; Liao, Wei-Qiang; Tang, Yuan-Yuan; Ye, Heng-Yun; Zhang, Yi; Xiong, Ren-Gen
    Journal of the American Chemical Society (2017), 139 (25), 8752-8757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    As a promising candidate for energy storage capacitors, antiferroelec. (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization vs. elec. field (P-E) hysteresis characteristics in contrast to ferroelecs. and linear dielecs. However, antiferroelectricity has only been discovered in inorg. oxides and some hydrogen-bonded mol. systems. In view of the structural diversity and unique phys. properties of org.-inorg. hybrid system, it remains a great opportunity to introduce antiferroelectricity into org.-inorg. hybrid perovskites. Here, the authors report that polarizable antiparallel dipole arrays can be realized in an org.-inorg. hybrid perovskite, (3-pyrrolinium)CdBr3, which not only exhibits an excellent ferroelec. 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 their knowledge, it is the first time that such successive ferroelec.-antiferroelec.-paraelec. phase transitions have been discovered in org.-inorg. perovskites. Besides, a giant dielec. const. 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 obsd. during the phase transition. Apparently, the combined striking AFE characteristic and giant dielec. const. make (3-pyrrolinium)CdBr3 a promising candidate for next generation high-energy-storage capacitors.
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  14. 14
    Zhang, Y.; Liao, W. Q.; Fu, D. W.; Ye, H. Y.; Liu, C. M.; Chen, Z. N.; Xiong, R. G. The First Organic-Inorganic Hybrid Luminescent Multiferroic: (Pyrrolidinium)MnBr3. Adv. Mater. 2015, 27 (26), 3942– 3946,  DOI: 10.1002/adma.201501026
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    14
    The First Organic-Inorganic Hybrid Luminescent Multiferroic: (Pyrrolidinium)MnBr3
    Zhang, Yi; Liao, Wei-Qiang; Fu, Da-Wei; Ye, Heng-Yun; Liu, Cai-Ming; Chen, Zhong-Ning; Xiong, Ren-Gen
    Advanced Materials (Weinheim, Germany) (2015), 27 (26), 3942-3946CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    By rational design and chem. synthesis, a new hybrid ferroelec. luminescent material, pyrrolidinium tribromomanganate, with a perovskite structure was obtained. A strong PL emission is obsd. at 640 nm with QE of 28.5% and emission lifetime of ∼0.1 ms. Such 2-H stacking perovskite has the advantage of structural tunability by adjusting the templating cations or the bridging atoms, as reported recently. Combining the luminescent property, structural, flexibility, and muitiferroicity the studies provide a new approach to fabricate multifunctional magnetooptoelectronic devices, which could eventually benefit the applications of magnetooptoelectronics and photovoltaics.
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  15. 15
    Cai, H. L.; Zhang, Y.; Fu, D. W.; Zhang, W.; Liu, T.; Yoshikawa, H.; Awaga, K.; Xiong, R. G. Above-Room-Temperature Magnetodielectric Coupling in a Possible Molecule-Based Multiferroic: Triethylmethylammonium Tetrabromoferrate(III). J. Am. Chem. Soc. 2012, 134 (45), 18487– 18490,  DOI: 10.1021/ja3073319
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    15
    Above-Room-Temperature Magnetodielectric Coupling in a Possible Molecule-Based Multiferroic: Triethylmethylammonium Tetrabromoferrate(III)
    Cai, Hong-Ling; Zhang, Yi; Fu, Da-Wei; Zhang, Wen; Liu, Tao; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen
    Journal of the American Chemical Society (2012), 134 (45), 18487-18490CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A possible above-room-temp. mol. multiferroic, triethylmethylammonium tetrabromoferrate(III) (1), has been discovered. Its ferroelec. and magnetic phase transitions take place at almost the same temp. (∼360 K), resulting in strong magnetodielec. (MD) coupling, with a MD ratio of 18% at 0.6 MHz. Interestingly, 1 also undergoes a low-temp. ferroelec.-ferroelec. phase transition with an Aizu notation of 6mmF6 and small magnetic and dielec. anomalies at 171 K.
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  16. 16
    Mei, G. Q.; Liao, W. Q. Structural Phase Transitions Coupled with Prominent Dielectric Anomalies and Dielectric Relaxation in a One-Dimensional Organic-Inorganic Hybrid Compound [C3H4NS][CdCl3]. J. Mater. Chem. C 2015, 3 (33), 8535– 8541,  DOI: 10.1039/C5TC02023A
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    16
    Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in a one-dimensional organic-inorganic hybrid compound [C3H4NS][CdCl3]
    Mei, Guang-Quan; Liao, Wei-Qiang
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (33), 8535-8541CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    A new 1-dimensional chlorocadmate(II) compd. contg. linear chains of face-sharing CdCl6 octahedra, thiazolium trichlorocadmate(II), exhibits one isostructural phase transition at 288 K and another symmetry-breaking phase transition at 215 K, accompanied by noteworthy dielec. anomalies and relaxation. Its phase transitions and dielec. responses were studied by DSC measurements, variable-temp. structural analyses, and dielec. measurements. The crystal structures detd. at 328, 253, and 173 K were solved in Cmcm, Cmcm, and C2/m, resp. The most distinct differences between these structures are the changes in the dynamics of thiazolium cations, which remain disordered in each structure. The isostructural transition can be ascribed to the slowing down of the mol. motions of thiazolium cations, while the symmetry-breaking one can be attributed to the reorientation of the cation. Two types of dielec. anomalies and one polydispersive dielec. relaxation process are clearly obsd. during the phase transitions. Such exceptional dielec. performances are also assocd. with the dynamic behaviors of the dipolar thiazolium cations.
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  17. 17
    Jakubas, R.; Sobczyk, L. Phase Transitions in Alkylammonium Halogenoantimonates and Bismuthates. Phase Transitions 1990, 20, 163– 193,  DOI: 10.1080/01411599008206873
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    Phase transitions in alkylammonium halogenoantimonates and bismuthates
    Jakubas, Ryszard; Sobczyk, Lucjan
    Phase Transitions (1990), 20 (3-4), 163-93CODEN: PHTRDP; ISSN:0141-1594.
    A review with many refs. of the results of studies on the structure, phase transitions and phys. properties of alkylammonium halogenoantimonates(III) and bismuthates(III). The crystals of these compds. are characterized by a variety of anionic structures and show a no. of phase transitions including those to polar phases. Dielec. and pyroelec. properties, spontaneous polarization and DSC studies are discussed. The mechanism of the phase transitions is discussed based on the results of x-ray, dielec. relaxation, PMR, IR and R spectra studies gathered so far. A particular role is played by a reorientational motion of the alkylammonium cations.
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  18. 18
    Jakubas, R.; Sobczyk, L. Ferroelectric Phase Transitions in Alkylammonium Halogenoantimonates (III). Ferroelectrics 1988, 78 (1), 69– 78,  DOI: 10.1080/00150198808215890
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    Ferroelectric phase transitions in alkylammonium halogenoantimonates(III)
    Jakubas, R.; Sobczyk, L.
    Ferroelectrics (1988), 78 (), 69-78CODEN: FEROA8; ISSN:0015-0193.
    A no. of crystals which exhibit dielec. anomalies and are composed of nonahalogenodiantimonate anion and alkylammonium cations of general formula [NH4-n(CH3)n]Sb2X9 (X = Cl, Br) were grown. Ferroelec. phase transitions were found in [(Me)2NH2]3Sb2Cl9, [Me3NH]3Sb2Cl9 and [Me2NH2]3Sb2Br9. X-ray diffraction, dielec., NMR and IR studies show that the order-disorder phase transitions are related to a motion of alkylammonium cations.
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  19. 19
    Zaleski, J.; Jakubas, R.; Galewski, Z.; Sobczyk, L. Structural Phase Transitions in [(C2H5)4N]3Sb2Br9 and [(C2H5)4N]3Bi2Br9. Z. Naturforsch., A: Phys. Sci. 1989, 44a, 1102– 1106,  DOI: 10.1515/zna-1989-1110
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    Piecha, A.; Pietraszko, A.; Bator, G.; Jakubas, R. Structural Characterization and Ferroelectric Ordering in (C3N2H5)5Sb2Br11. J. Solid State Chem. 2008, 181, 1155– 1166,  DOI: 10.1016/j.jssc.2008.02.029
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    20
    Structural characterization and ferroelectric ordering in (C3N2H5)5Sb2Br11
    Piecha, A.; Pietraszko, A.; Bator, G.; Jakubas, R.
    Journal of Solid State Chemistry (2008), 181 (5), 1155-1166CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
    A ferroelec. crystal (C3N2H5)5Sb2Br11 has been synthesized. The single crystal X-ray diffraction studies (at 300, 155, 138 and 121 K) show that it is built up of discrete corner-sharing bioctahedral Sb2Br115- and highly disordered imidazolium cations. The room temp. crystal structure has been detd. as monoclinic, space group, P21/n with: a = 9.139 Å, b = 15.150 Å and c = 13.969 Å and β = 96.19°. The crystal undergoes three solid-solid phase transitions: (tetragonal) 354/352↔ P21/n (I ↔ II) discontinuous, P21/n 145↔ Pn (II ↔ III) continuous and Pn 120/135↔ Pn (III ↔ IV) discontinuous. The dielec. and pyroelec. measurements allow us to characterize the low temp. phases III and IV as ferroelec. with the Curie point at 145 K and the satd. spontaneous polarization value of the order of 1.8 × 10-3 Cm-2 along the a-axis (135 K). The ferroelec. phase transition mechanism at 145 K is due to the dynamics of imidazolium cations.
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    Scott, J. F. Applications of Modern Ferroelectrics. Science 2007, 315 (5814), 954– 959,  DOI: 10.1126/science.1129564
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    Applications of modern ferroelectrics
    Scott, J. F.
    Science (Washington, DC, United States) (2007), 315 (5814), 954-959CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    A review. Long viewed as a topic in classical physics, ferroelectricity can be described by a quantum mech. ab initio theory. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. Recent prototype applications include ultrafast switching, cheap room-temp. magnetic-field detectors, piezoelec. nanotubes for microfluidic systems, electrocaloric coolers for computers, phased-array radar, and 3D trenched capacitors for dynamic random access memories. Terabit-per-square-inch ferroelec. arrays of PZT were reported on Pt nanowire interconnects and nanorings with 5-nm diams. Finally, electron emission from ferroelecs. yields cheap, high-power microwave devices and miniature x-ray and neutron sources.
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  22. 22
    Wojtaś, M.; Reece, M. J. Dynamics of Ferroelectric Switching of [H3CNH3]5[Bi2Br11]. J. Appl. Phys. 2012, 111 (2), 024108-1-6
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    Piecha, A.; Białońska, A.; Jakubas, R. Structure and Ferroelectric Properties of [C3N2H5]5[Bi2Br11]. J. Phys.: Condens. Matter 2008, 20, 325224– 325233,  DOI: 10.1088/0953-8984/20/32/325224
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    23
    Structure and ferroelectric properties of [C3N2H5]5[Bi2Br11]
    Piecha, A.; Bialonska, A.; Jakubas, R.
    Journal of Physics: Condensed Matter (2008), 20 (32), 325224/1-325224/9CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
    A ferroelec. crystal [C3N2H5]5[Bi2Br11] has been synthesized and structurally characterized at 170 and 100 K. The crystal structure consists of discrete corner-sharing bioctahedra [Bi2Br11]5- and highly disordered imidazolium cations. The room temp. crystal structure has been detd. as monoclinic, space group, P21/n with: a = 9.257(2) Å, b = 15.157(3) Å, c = 13.865(3) Å and β = 97.73(3)°. The crystal undergoes two solid-solid phase transitions: at 355 K of first-order and at 155 K of second-order type. The later transition takes place between monoclinic phases: P21/n → Pn. The dielec. and pyroelec. measurements allow us to characterize the low temp. phase III as ferroelec. with the Curie temp. at 155 K. The satd. spontaneous polarization of the order of 2.6 × 10-3 C m-2 was measured along the a-axis (130 K). The ferroelec. phase transition mechanism at 155 K is due to the dynamics of three of five nonequivalent imidazolium cations.
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  24. 24
    Szklarz, P.; Gągor, A.; Jakubas, R.; Zieliński, P.; Piecha-Bisiorek, A.; Cichos, J.; Karbowiak, M.; Bator, G.; Cizman, A. Lead-Free Hybrid Ferroelectric Material Based on Formamidine: [NH2CHNH2]3Bi2I9. J. Mater. Chem. C 2019, 7 (10), 3003– 3014,  DOI: 10.1039/C8TC06458J
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    24
    Lead-free hybrid ferroelectric material based on formamidine: [NH2CHNH2]3Bi2I9
    Szklarz, Przemyslaw; Gagor, Anna; Jakubas, Ryszard; Zielinski, Piotr; Piecha-Bisiorek, Anna; Cichos, Jakub; Karbowiak, Miroslaw; Bator, Grazyna; Cizman, Agnieszka
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2019), 7 (10), 3003-3014CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    The extraordinary thermal stability of [NH2CHNH2]3Bi2I9 (FA3Bi2I9) crystals, up to around 600 K, has been enhanced by using the evapg. method. DSC measurements have revealed reversible structural phase transitions: at 203 K (Phase I → Phase II), 173 K (II → III), 134.7 K (III → IV), 131.4 K (IV → V), and 120 K (V → VI). The crystal structures of FA3Bi2I9 adopt the polar space groups P63mc at 220 K (Phase I) and Cmc21 at 190 K (Phase II). The pyroelec. current (Ipyr) measured in the temp. range covering all the phases of FA3Bi2I9 confirmed their polar nature. The reversibility of the spontaneous polarization in each phase has been confirmed by the obsd. hysteresis loops. All the phase transitions are dielec. active. The dielec. response (ε*(ω,T) close to 134.7 and 131.4 K) is characteristic of ferroelecs. with a crit. slowing-down process. Optical bandgaps estd. from the UV-vis measurements and calcd. using the DFT method are equal to 1.85 and 1.89 eV, resp. On the basis of the structural, dielec., and spectroscopic results, the mol. mechanisms of the phase transitions have been proposed.
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    Jóźków, J.; Jakubas, R.; Bator, G.; Pietraszko, A. Ferroelectric Properties of (C5H5NH)5Bi2Br11. J. Chem. Phys. 2001, 114 (16), 7239– 7246,  DOI: 10.1063/1.1349897
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    25
    Ferroelectric properties of (C5H5NH)5Bi2Br11
    Jozkow, J.; Jakubas, R.; Bator, G.; Pietraszko, A.
    Journal of Chemical Physics (2001), 114 (16), 7239-7246CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    A new pyridinium compd., (C5H5NH)5Bi2Br11, has been synthesized. The x-ray diffraction studies indicate that its structure is built up of four independent pyridinium cations and isolated Bi2Br115- groups. At room temp. it crystallizes in the monoclinic space group P21/n. Two phase transitions of second- and first-order type are detected by the differential scanning calorimetry measurements at 118 and 405/403 K (on heating-cooling), resp. The corresponding anomalies in the linear thermal expansion at 118 and 405 K are obsd. along three crystallog. directions. The dielec. investigations reveal dielec. absorption and dispersion in the radio-frequency region. The exptl. results were analyzed on the basis of dielec. formula which represents the sum of two independent relaxators. The pyroelec. measurements reveal that (C5H5NH)5Bi2Br11 becomes ferroelec. below 118 K and is characterized by the appearance of spontaneous polarization of the order of 3·10-3 C/m2 along the b axis.
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    Jakubas, R.; Piecha, A.; Pietraszko, A.; Bator, G. Structure and Ferroelectric Properties of (C3N2H5)5Bi2Cl11. Phys. Rev. B - Condens. Matter Mater. Phys. 2005, 72 (10), 1– 8,  DOI: 10.1103/PhysRevB.72.104107
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    Zhang, H. Y.; Wei, Z.; Li, P. F.; Tang, Y. Y.; Liao, W. Q.; Ye, H. Y.; Cai, H.; Xiong, R. G. The Narrowest Band Gap Ever Observed in Molecular Ferroelectrics: Hexane-1,6-Diammonium Pentaiodobismuth(III). Angew. Chem., Int. Ed. 2018, 57 (2), 526– 530,  DOI: 10.1002/anie.201709588
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    27
    The Narrowest Band Gap Ever Observed in Molecular Ferroelectrics: Hexane-1,6-diammonium Pentaiodobismuth(III)
    Zhang, Han-Yue; Wei, Zhenhong; Li, Peng-Fei; Tang, Yuan-Yuan; Liao, Wei-Qiang; Ye, Heng-Yun; Cai, Hu; Xiong, Ren-Gen
    Angewandte Chemie, International Edition (2018), 57 (2), 526-530CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Narrow band gaps and excellent ferroelectricity are intrinsically paradoxical in ferroelecs. as the leakage current caused by an increase in the no. of thermally excited carriers will lead to a deterioration of ferroelectricity. A new mol. ferroelec., hexane-1,6-diammonium pentaiodobismuth (HDA-BiI5), was now developed through band gap engineering of org.-inorg. hybrid materials. It features an intrinsic band gap of 1.89 eV, and thus represents the 1st mol. ferroelec. with a band gap of <2.0 eV. Simultaneously, low-temp. soln. processing was successfully applied to fabricate high-quality ferroelec. thin films based on HDA-BiI5, for which high-precision controllable domain flips were realized. Owing to its narrow band gap and excellent ferroelectricity, HDA-BiI5 can be considered as a milestone in the exploitation of mol. ferroelecs., with promising applications in high-d. data storage and photovoltaic conversion.
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    Shi, C.; Han, X.-B.; Zhang, W. Structural Phase Transition-Associated Dielectric Transition and Ferroelectricity in Coordination Compounds. Coord. Chem. Rev. 2019, 378, 561– 576,  DOI: 10.1016/j.ccr.2017.09.020
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    Structural phase transition-associated dielectric transition and ferroelectricity in coordination compounds
    Shi, Chao; Han, Xiang-Bin; Zhang, Wen
    Coordination Chemistry Reviews (2019), 378 (), 561-576CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. Structural phase transition in solid-state materials is an underlying factor for emergence and evolution of a no. of important phys./chem. properties. In this review, we summarize recent achievements on two types of structural phase transition-assocd. properties, i.e., dielec. transition and ferroelectricity, in coordination compds. The basic concepts and fundamentals of structural phase transition and the two properties are briefly introduced. This review aims to reveal the role of the structural phase transitions on bulk properties and afford a perspective on the connections among multiple topics of coordination chem. from the structural phase transition viewpoint. It would be appealing to researchers in multidisciplinary fields such as coordination chem., crystal engineering, supramol. chem., condensed matter physics, responsive materials and mol. machines.
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    Zhang, W.; Xiong, R. G. Ferroelectric Metal-Organic Frameworks. Chem. Rev. 2012, 112 (2), 1163– 1195,  DOI: 10.1021/cr200174w
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    Ferroelectric Metal-Organic Frameworks
    Zhang, Wen; Xiong, Ren-Gen
    Chemical Reviews (Washington, DC, United States) (2012), 112 (2), 1163-1195CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review.
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    Shi, P. P.; Tang, Y. Y.; Li, P. F.; Liao, W. Q.; Wang, Z. X.; Ye, Q.; Xiong, R. G. Symmetry Breaking in Molecular Ferroelectrics. Chem. Soc. Rev. 2016, 45 (14), 3811– 3827,  DOI: 10.1039/C5CS00308C
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    30
    Symmetry breaking in molecular ferroelectrics
    Shi, Ping-Ping; Tang, Yuan-Yuan; Li, Peng-Fei; Liao, Wei-Qiang; Wang, Zhong-Xia; Ye, Qiong; Xiong, Ren-Gen
    Chemical Society Reviews (2016), 45 (14), 3811-3827CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    Ferroelecs. are inseparable from symmetry breaking. Accompanying the paraelec.-to-ferroelec. phase transition, the paraelec. phase adopting one of the 32 crystallog. point groups is broken into subgroups belonging to one of the 10 ferroelec. point groups, i.e. C1, C2, C1h, C2v, C4, C4v, C3, C3v, C6 and C6v. The symmetry breaking is captured by the order parameter known as spontaneous polarization, whose switching under an external elec. field results in a typical ferroelec. hysteresis loop. In addn., the responses of spontaneous polarization to other external excitations are related to a no. of phys. effects such as second-harmonic generation, piezoelectricity, pyroelectricity and dielec. properties. Based on these, this review summarizes recent developments in mol. ferroelecs. since 2011 and focuses on the relationship between symmetry breaking and ferroelectricity, offering ideas for exploring high-performance mol. ferroelecs.
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  31. 31
    Huang, C.; Luo, X.; Liao, W.; Tang, Y.; Xiong, R. An Above-Room-Temperature Molecular Ferroelectric: [Cyclopentylammonium]2CdBr4. Inorg. Chem. 2020, 59, 829,  DOI: 10.1021/acs.inorgchem.9b03098
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    31
    An above-room-temperature molecular ferroelectric: [Cyclopentylammonium]2CdBr4
    Huang, Chao-Ran; Luo, Xuzhong; Liao, Wei-Qiang; Tang, Yuan-Yuan; Xiong, Ren-Gen
    Inorganic Chemistry (2020), 59 (1), 829-836CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Mol. ferroelecs. as alternatives to the conventional inorg. ferroelecs. have been greatly developed in past decades; many of these have been discovered and designed through various chem. means due to their structural adjustability. However, it is still a huge challenge to obtain high (above room temp.) Curie temp. (Tc) mol. ferroelecs. to meet the application requirements. Here, we present a new org.-inorg. hybrid mol. ferroelec., [cyclopentylammonium]2CdBr4 (I), showing a moderate above-room-temp. Tc of 340.3 K. The mechanism of the ferroelec. phase transition from Pnam to Pna21 in I is ascribed to the order-disorder transition of both the org. cations and inorg. anions, affording a spontaneous polarization of 0.57μC/cm2 for the ferroelec. phase. Using piezoresponse force microscopy (PFM), we clearly obsd. the antiparallel 180° stripe domains and realized the polarization switching, unambiguously establishing the existence of room-temp. ferroelectricity in the thin film. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications. A new mol. ferroelec., [cyclopentylammonium]2CdBr4, shows an above-room-temp. Curie temp. of 340.3 K with the symmetry breaking from Pnam to Pna21.
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  32. 32
    Lu, J.; Kochi, J. K. Charge-Modulated Associates of Anionic Donors with Cationic π-Acceptors: Crystal Structures of Ternary Synthons Leading to Molecular Wires. Cryst. Growth Des. 2009, 9, 291– 296,  DOI: 10.1021/cg800465e
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    32
    Charge-Modulated Associates of Anionic Donors with Cationic π-Acceptors: Crystal Structures of Ternary Synthons Leading to Molecular Wires
    Lu, Jianjiang; Kochi, Jay K.
    Crystal Growth & Design (2009), 9 (1), 291-296CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    Tetramethylpyrazine is effectively transformed via controlled N-protonation or N-methylation to afford a series of mono- and dicationic π-acceptors of particular use in the study of charge modulation during the self-assembly of various anionic donors and π-acid acceptors into ternary synthons and infinite linear chains (mol. wires). Thus, when the charges of the anionic donor (D) and the cationic acceptor (A) are unequal (either as 1:2 or as 2:1), the corresponding crystal structures of the donor/acceptor assocs. all contain structure motifs of discrete synthons consisting of (A···D···A) or (D···A···D) triads. On the other hand, when the anionic donor and cationic acceptor are of equal charge (either as 1:1 or as 2:2), the corresponding crystal structures all contain infinite chain arrangements: (···D···A···D···A···D···), which are the same as those we previously found in the cocrystn. of various anionic donors with neutral π-acids. Fully appreciated anion/π interactions are found in all of these solids owing to the absence of arom. protons in the π-acids, as well as the presence of strong electrostatic anion/cation interactions. It is noteworthy in such assocs. that halide anions (Cl-, Br-, and I-) show different patterns of donor/acceptor interactions. For example, in the case of the diprotonated tetramethylpyrazinium dication, the chloride donor is π-bonded over the edge of the arom. ring, whereas bromide and iodide donors are precisely located over the arom. ring centrosym. We hope these structural studies will provide addnl. stimulus for the design of new anion receptors based on the use of charged arom. acceptors.
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  33. 33
    Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W. Synthesis, Crystal Structure, Physico-Chemical Characterization and Dielectric Properties of a New Hybrid Material, 1-Ethylpiperazine-1,4-Diium Tetrachlorocadmate. J. Mol. Struct. 2015, 1102, 50– 56,  DOI: 10.1016/j.molstruc.2015.08.044
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    Synthesis, crystal structure, physico-chemical characterization and dielectric properties of a new hybrid material, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate
    Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W.
    Journal of Molecular Structure (2015), 1102 (), 50-56CODEN: JMOSB4; ISSN:0022-2860. (Elsevier B.V.)
    A new org.-inorg. hybrid metal complex, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate was synthesized and the structure is detd. by single crystal x-ray diffraction analyses. The title compd. crystallizes in the orthorhombic system with space group Pbca. The unit cell parameters are a 11.5129(2) Å, b 9.7801(2) Å, c 23.8599(4) Å with Z = 8 and V = 2686.56(8) Å3. The examn. of the structure shows that Cd(II) is coordinated by 4 Cl atoms and adopts a tetrahedral geometry. Three-dimensional frameworks of the title compd. are produced by N-H···Cl and C-H···Cl H bonding. IR, Raman and UV-Visible spectroscopies were also used to characterize this complex. Also, the fluorescent properties of the compd. were studied in the solid state at room temp. Solid state 13C MAS NMR spectroscopy results are in agreement with the x-ray structure. DSC revealed a structural phase transition of the order-disorder type around 373 K, and dielec. measurements were performed to discuss the mechanism of this phase transition. The evolution of dielec. const. as a function of temp. of the sample was studied to det. some related parameters.
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  34. 34
    Wang, X. L.; Zhou, L.; Ye, Q.; Geng, F. J.; Ye, H. Y.; Fu, D. W.; Zhang, Y. A Spiro-Type Ammonium Based Switchable Dielectric Material with Two Sequential Reversible Phase Transitions above Room Temperature. RSC Adv. 2016, 6 (78), 74117– 74123,  DOI: 10.1039/C6RA14157A
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    A spiro-type ammonium based switchable dielectric material with two sequential reversible phase transitions above room temperature
    Wang, Xiao-Li; Zhou, Lin; Ye, Qiong; Geng, Fu-Juan; Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi
    RSC Advances (2016), 6 (78), 74117-74123CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    An org.-inorg. hybrid compd. 5-azonia-spiro[4,4]nonane tetrabromocadmium (1, [ASN]2[CdBr4], ASN = (CH2)4N(CH2)4), has been discovered as a new phase transition material. Differential scanning calorimetry (DSC) and dielec. measurements reveal that 1 undergoes dielec. anomalies which could be tuned in three evident dielec. states and switched by two sequential reversible phase transitions around 336 and 357 K, resp. Detailed variable-temp. single-crystal structural analyses indicate that the distinct twisting motions of the flexible [ASN]+ ammonium cationic moieties and the relative reorientations of both the ions contribute to the structure phase transitions of 1 triggered by temp. Particularly, 1 displays a switchable SHG response in the vicinity of 357 K, where the temp.-dependent dielec. permittivity of 1 changes abruptly from 8 to 15, with a large thermal hysteresis of 19 K. Therefore, such a distinctive dielec. performance discloses that 1 might be an interesting high-temp. switchable dielec. and nonlinear optical material. All these results open a new venue to design novel phase transition materials through selecting the flexible spiro-type ammonium salts.
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  35. 35
    Puget, R.; Jannin, M.; De Brauer, C.; Perret, R. Structures of Trimethyloxosulfonium Salts. V. The Catena-Tri-μ-Chloro- Cadmate and the Catena-Tri-μ-Bromo-Cadmate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1991, 47 (9), 1803– 1805,  DOI: 10.1107/S0108270190013701
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    Xu, W. J.; He, C. T.; Ji, C. M.; Chen, S. L.; Huang, R. K.; Lin, R. B.; Xue, W.; Luo, J. H.; Zhang, W. X.; Chen, X. M. Molecular Dynamics of Flexible Polar Cations in a Variable Confined Space: Toward Exceptional Two-Step Nonlinear Optical Switches. Adv. Mater. 2016, 28, 5886– 5890,  DOI: 10.1002/adma.201600895
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    36
    Molecular Dynamics of Flexible Polar Cations in a Variable Confined Space: Toward Exceptional Two-Step Nonlinear Optical Switches
    Xu, Wei-Jian; He, Chun-Ting; Ji, Cheng-Min; Chen, Shao-Li; Huang, Rui-Kang; Lin, Rui-Biao; Xue, Wei; Luo, Jun-Hua; Zhang, Wei-Xiong; Chen, Xiao-Ming
    Advanced Materials (Weinheim, Germany) (2016), 28 (28), 5886-5890CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A hexagonal perovskite compd., pyrrolidinium cadmium trichloride [C4H10N][CdCl3], composed of rigid inorg. chains embedded with flexible org. cations, has been synthesized and studied by variable-temp. X-ray anal., dielec. and SHG measurements, as well as classical mol. dynamics simulations. The changeable mol. dynamics of the flexible polar cations in the variable confined space between inorg. chains brings about thermal-induced two-step phase transitions, including a typical ferroelec. transition that loses inversion centers by cooling from room temp. to 240 K and an exceptional one that regains inversion centers by further cooling to 198 K. Such reversible transitions between one noncentrosym. phase and two centrosym. phases affords a new type of two-step NLO switches, which exhibits genuine "off-one-off" SHG conversion between one NLO-active state and two NLO-inactive states with a remarkable SHG contrast of -8.0.
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    Ye, H. Y.; Zhang, Y.; Fu, D. W.; Xiong, R. G. An Above-Room-Temperature Ferroelectric Organo-Metal Halide Perovskite: (3-Pyrrolinium)(CdCl3). Angew. Chem., Int. Ed. 2014, 53, 11242– 11247,  DOI: 10.1002/anie.201406810
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    37
    An above-room-temperature ferroelectric organo-metal halide perovskite: (3-pyrrolinium)(CdCl3)
    Ye, Heng-Yun; Zhang, Yi; Fu, Da-Wei; Xiong, Ren-Gen
    Angewandte Chemie, International Edition (2014), 53 (42), 11242-11247CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Hybrid organo-metal halide perovskite materials, such as CH3NH3PbI3, have been shown to be some of the most competitive candidates for absorber materials in photovoltaic (PV) applications. However, their potential has not been completely developed, because a photovoltaic effect with an anomalously large voltage can be achieved only in a ferroelec. phase, while these materials are probably ferroelec. only at temps. below 180 K. A new hexagonal stacking perovskite-type complex (3-pyrrolinium)(CdCl3) exhibits above-room-temp. ferroelectricity with a Curie temp. Tc=316 K and a spontaneous polarization Ps=5.1 μC cm-2. The material also exhibits antiparallel 180° domains which are related to the anomalous photovoltaic effect. The open-circuit photovoltage for a 1 mm-thick bulky crystal reaches 32 V. This finding could provide a new approach to develop solar cells based on organo-metal halide perovskites in photovoltaic research.
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  38. 38
    Li, P. F.; Liao, W. Q.; Tang, Y. Y.; Ye, H. Y.; Zhang, Y.; Xiong, R. G. Unprecedented Ferroelectric-Antiferroelectric-Paraelectric Phase Transitions Discovered in an Organic-Inorganic Hybrid Perovskite. J. Am. Chem. Soc. 2017, 139, 8752– 8757,  DOI: 10.1021/jacs.7b04693
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    38
    Unprecedented ferroelectric-antiferroelectric-paraelectric phase transitions discovered in an organic-inorganic hybrid perovskite
    Li, Peng-Fei; Liao, Wei-Qiang; Tang, Yuan-Yuan; Ye, Heng-Yun; Zhang, Yi; Xiong, Ren-Gen
    Journal of the American Chemical Society (2017), 139 (25), 8752-8757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    As a promising candidate for energy storage capacitors, antiferroelec. (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization vs. elec. field (P-E) hysteresis characteristics in contrast to ferroelecs. and linear dielecs. However, antiferroelectricity has only been discovered in inorg. oxides and some hydrogen-bonded mol. systems. In view of the structural diversity and unique phys. properties of org.-inorg. hybrid system, it remains a great opportunity to introduce antiferroelectricity into org.-inorg. hybrid perovskites. Here, the authors report that polarizable antiparallel dipole arrays can be realized in an org.-inorg. hybrid perovskite, (3-pyrrolinium)CdBr3, which not only exhibits an excellent ferroelec. 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 their knowledge, it is the first time that such successive ferroelec.-antiferroelec.-paraelec. phase transitions have been discovered in org.-inorg. perovskites. Besides, a giant dielec. const. 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 obsd. during the phase transition. Apparently, the combined striking AFE characteristic and giant dielec. const. make (3-pyrrolinium)CdBr3 a promising candidate for next generation high-energy-storage capacitors.
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  39. 39
    Zhang, Y.; Ye, H. Y.; Zhang, W.; Xiong, R. G. Room-Temperature ABX3-Typed Molecular Ferroelectric: [C5H9-NH3][CdCl3]. Inorg. Chem. Front. 2014, 1, 118– 123,  DOI: 10.1039/c3qi00058c
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    39
    Room-temperature ABX3-typed molecular ferroelectric: [C5H9-NH3][CdCl3]
    Zhang, Yi; Ye, Heng-Yun; Zhang, Wen; Xiong, Ren-Gen
    Inorganic Chemistry Frontiers (2014), 1 (1), 118-123CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
    Reaction of CdCl2 with cyclopentylamine in the presence of aq. HCl affords an ABX3-typed perovskite structure compd. [C5H9-NH3][CdCl3] (1). Above 300 K, it is in a paraelec. phase with a centrosym. space group Cmcm, while below 300 K it has a noncentrosym. space group Cc, corresponding to a ferroelec. phase. The temp.-dependent dielec. const. shows a peak at about 300 K with a 12-fold enhancement which is confirmed by differential scanning calorimetry. The normalized pyroelec. and second-harmonic generation effect as functions of temp. are almost overlapped, probably indicating that the trends with temp. basically satisfy the Landau phenomenol. theory, revealing a symmetry-breaking occurrence. The ferroelectricity, a spontaneous satn. polarization approx. reaching 1.7 μC cm-2, is further confirmed by piezoresponse force microscopy.
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  40. 40
    Gesi, K. Ferroelectricity in (NCH3)4CdBr3. J. Phys. Soc. Jpn. 1990, 59, 432– 434,  DOI: 10.1143/JPSJ.59.432
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    Ferroelectricity in tetramethylammonium tribromocadmate
    Gesi, Kazuo
    Journal of the Physical Society of Japan (1990), 59 (2), 432-4CODEN: JUPSAU; ISSN:0031-9015.
    Dielec. properties of N(CH3)4CdBr3 single crystal have been studied. The dielec. const. along the c-direction shows a slight γ-type max. at 156 K while that along the a-direction shows a discontinuity. The compd. exhibits ferroelec. activity along the c-direction below the Curie temp. of 156 K. The spontaneous polarization obtained by 50 Hz hysteresis loop measurement is about 1.2 × 10-3 C/m2 at 125 K.
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    You, Y. M.; Liao, W. Q.; Zhao, D.; Ye, H. Y.; Zhang, Y.; Zhou, Q.; Niu, X.; Wang, J.; Li, P. F.; Fu, D. W. An Organic-Inorganic Perovskite Ferroelectric with Large Piezoelectric Response. Science 2017, 357, 306– 309,  DOI: 10.1126/science.aai8535
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    An organic-inorganic perovskite ferroelectric with large piezoelectric response
    You, Yu-Meng; Liao, Wei-Qiang; Zhao, Dewei; Ye, Heng-Yun; Zhang, Yi; Zhou, Qionghua; Niu, Xianghong; Wang, Jinlan; Li, Peng-Fei; Fu, Da-Wei; Wang, Zheming; Gao, Song; Yang, Kunlun; Liu, Jun-Ming; Li, Jiangyu; Yan, Yanfa; Xiong, Ren-Gen
    Science (Washington, DC, United States) (2017), 357 (6348), 306-309CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Mol. piezoelecs. are highly desirable for their easy and environment-friendly processing, light wt., low processing temp., and mech. flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelec. effect, mol. piezoelecs. with a piezoelec. coeff. d33 comparable with piezoceramics such as barium titanate (BTO; ∼190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an org.-inorg. perovskite ferroelec. crystal processed from aq. soln., has a large d33 of 185 picocoulombs per newton and a high phase-transition temp. of 406 K (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromech., and biomech. applications.
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    Liao, W. Q.; Tang, Y. Y.; Li, P. F.; You, Y. M.; Xiong, R. G. Competitive Halogen Bond in the Molecular Ferroelectric with Large Piezoelectric Response. J. Am. Chem. Soc. 2018, 140, 3975– 3980,  DOI: 10.1021/jacs.7b12524
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    Competitive halogen bond in the molecular ferroelectric with large piezoelectric response
    Liao, Wei-Qiang; Tang, Yuan-Yuan; Li, Peng-Fei; You, Yu-Meng; Xiong, Ren-Gen
    Journal of the American Chemical Society (2018), 140 (11), 3975-3980CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Mol. piezoelecs. are attracting tremendous interest because of their easy processing, light wt., low acoustical impedance and mech. flexibility. However, reports of mol. piezoelecs. with a piezoelec. coeff. d33 comparable to piezoceramics such as barium titanate (BTO, 90-190 pC/N) have been scarce. Here, we present a uniaxial mol. ferroelec., trimethylchloromethylammonium tribromocadmium(II) (TMCM-CdBr3), in which the halogen bonding might be a possible crit. point for the stabilization of 1-dimensional (1D) {CdBr3}- chain and further reservation of its ferroelectricity in such org.-inorg. hybrid cryst. systems. It has a large d33 of 139 pC/N, 1 order of magnitude higher than those of most classically uniaxial ferroelecs. such as LiNbO3 (6-16 pC/N) and Rochelle salt (∼7 pC/N), and comparable with those of multiaxial ferroelecs. 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 mol. piezoelecs. and contribute to further developments.
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    Liao, W. Q.; Ye, H. Y.; Fu, D. W.; Li, P. F.; Chen, L. Z.; Zhang, Y. Temperature-Triggered Reversible Dielectric and Nonlinear Optical Switch Based on the One-Dimensional Organic - Inorganic Hybrid Phase Transition Compound [C6H11NH3]2CdCl4. Inorg. Chem. 2014, 53, 11146– 11151,  DOI: 10.1021/ic501749c
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    43
    Temperature-Triggered Reversible Dielectric and Nonlinear Optical Switch Based on the One-Dimensional Organic-Inorganic Hybrid Phase Transition Compound [C6H11NH3]2CdCl4
    Liao, Wei-Qiang; Ye, Heng-Yun; Fu, Da-Wei; Li, Peng-Fei; Chen, Li-Zhuang; Zhang, Yi
    Inorganic Chemistry (2014), 53 (20), 11146-11151CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    The one-dimensional org.-inorg. hybrid compd. 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 sepd. 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 DSC measurements, variable-temp. structural analyses, and dielec. and second harmonic generation (SHG) measurements. A precise structural anal. 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 dielec. const. and SHG intensity of 1 show a striking change between low and high states at ∼367 K, which reveals that 1 might be considered as a potential dielec. and nonlinear optical (NLO) switch with high-temp. response characterization, excellent reversibility, and obvious change of states.
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    Jin, J.; Jin, L.; Su, E.-B. Temperature-Induced Isosymmetric Reversible Structural Phase Transition in Catena-[Pyridinium Tris(μ2-Bromo)-Cadmium(II)]. CrystEngComm 2014, 16 (39), 9284– 9290,  DOI: 10.1039/C4CE00799A
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    Temperature-induced isosymmetric reversible structural phase transition in catena-[pyridinium tris(μ2-bromo)-cadmium(II)]
    Jin, Jing; Jin, Lei; Su, En-Ben
    CrystEngComm (2014), 16 (39), 9284-9290CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    A new centrosym. one-dimensional ABX3-type org.-inorg. hybrid polymer compd. ([C5H6N+][CdBr3]-) was synthesized and sepd. into block colorless crystals. DSC and dielec. measurements indicate that this compd. undergoes a reversible phase transition at 230 K with a hysteresis width of 17.9 K. The crystal structures, detd. at 293(2) K and 140(2) K, show that the phase transition is a type of isosym. change from the space group of Pbca (no. 61) in the low-temp. phase (LTP) to the space group of Cmcm (no. 63) in the room-temp. phase (RTP). The main difference between the LTP and the RTP structures is the distribution of the nitrogen atoms in the pyridinium cations. In the LTP, pyridinium cations are well ordered with localized N and C atom positions. Meanwhile, for the RTP, the N atoms are indistinguishable from the C3 atoms with the occupancy of N/C3 atoms being 0.5, sep. Noncovalent static attracting forces (Coulombic and van der Waals forces) and nonclassical C-H···Br and N-H···Br hydrogen-bond interactions stabilize the crystal structure.
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    One-dimensional Cd metal string complex: Synthesis, structural and thermal properties of [(HPy)3(Cd3Cl9)]∞
    Jian, Fang Fang; Zhao, Pu Su; Wang, Qing Xiang; Li, Ying
    Inorganica Chimica Acta (2006), 359 (5), 1473-1477CODEN: ICHAA3; ISSN:0020-1693. (Elsevier B.V.)
    The cadmium metal string complex of [(HPy)3(Cd3Cl9)]∞ (Py = pyridine) was prepd. Its structural and thermal properties were also studied. Its existing form in the gas phase was elucidated by d. functional calcns. The crystal structure consists of protonation pyridine cations and infinite 1-dimensional chains of [Cd3Cl9]3- anions. Each Cd atom is octahedrally surround by bridged chlorine atoms, giving rise to polymeric chains along the a-axis. The pyridinium cations lie in the middle of the chains to balance the charge. The DFT study indicates that the HOMO orbital of optimized structure is mainly localized on the middle six chloride ions and the LUMO is delocalized. Differential TGA shows there is no presence of any structural phase transitions.
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    Wang, Z.; Lv, X. H.; Liu, Y. L.; Lu, Y.; Chen, H. P.; Ge, J. Z. Prominent Dielectric Transitions in Layered Organic-Inorganic Hybrids: (Isoamyl-Ammonium)2CdX4 (X = Cl and Br). Inorg. Chem. Front. 2017, 4 (8), 1330– 1336,  DOI: 10.1039/C7QI00270J
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    Prominent dielectric transitions in layered organic-inorganic hybrids: (isoamyl-ammonium)2CdX4 (X = Cl and Br)
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    Inorganic Chemistry Frontiers (2017), 4 (8), 1330-1336CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
    Layered org.-inorg. hybrids represent a class of technol. important materials due to their promising phys. properties. In this report, two new layered org.-inorg. hybrid compds. (IAA)2CdX4 (IAA = isoamyl-ammonium cation, X = Cl, 1 and Br, 2) have been successfully synthesized and characterized. 1 undergoes a reversible solid-state phase transition at 230 K and 2 demonstrates three successive phase transitions and both of them exhibit prominent temp.-dependent dielec. behaviors. Detailed characterization was performed to investigate their phase transitions, including differential scanning calorimetry (DSC) measurements, variable-temp. structural analyses, variable-temp. powder X-ray diffraction (VT-PXRD) and dielec. measurements. The obvious difference in the phase transitions between 1 and 2 is originated from a bridged halogen effect, which makes different spaces between the inorg. framework layers where the org. IAA cation resides, resulting in different dynamic motions of the org. cations. These findings might be helpful to search for new dielec. materials based on layered org.-inorg. hybrid perovskites through exchange of the halogen atom.
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    Han, S.; Liu, X.; Zhang, J.; Ji, C.; Wu, Z.; Tao, K.; Wang, Y.; Sun, Z.; Luo, J. Dielectric Phase Transition Triggered by the Order-Disorder Transformation of Cyclopropylamine in a Layered Organic-Inorganic Halide Perovskite. J. Mater. Chem. C 2018, 6, 10327– 10331,  DOI: 10.1039/C8TC03517B
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    Dielectric phase transition triggered by the order-disorder transformation of cyclopropylamine in a layered organic-inorganic halide perovskite
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    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (38), 10327-10331CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    Cyclic org. amines are emerging as excellent building blocks to assemble org.-inorg. hybrid phase transition materials due to their flexible cyclic structure. Herein, we used a three-membered ring org. amine, cyclopropylamine, assembling a layered org.-inorg. hybrid dielec. phase transition compd. ([C3H5NH3]2[CdCl4], CPA) that displays a remarkable switchable dielec. response induced by an order-disorder transformation of the org. moiety. More specifically, the dielec. const. of CPA can be tuned between high- and low-dielec. states at ∼273 K, which demonstrates its potential application in a switchable dielec. field. In addn., theor. anal. of electronic band structures suggests that CPA exhibits a direct-band-gap with the value of 5.20 eV. This solid-state structural phase transition triggered by ordering of a three-membered ring org. amine is reported for the first time, and it highlights a new potential strategy to design switchable dielec. materials.
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    Liao, W. Q.; Mei, G. Q.; Ye, H. Y.; Mei, Y. X.; Zhang, Y. Structural Phase Transitions of a Layered Organic-Inorganic Hybrid Compound: Tetra(Cyclopentylammonium) Decachlorotricadmate(II), [C5H9NH3]4Cd3Cl10. Inorg. Chem. 2014, 53, 8913– 8918,  DOI: 10.1021/ic500554z
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    Structural Phase Transitions of a Layered Organic-Inorganic Hybrid Compound: Tetra(cyclopentylammonium) Decachlorotricadmate(II), [C5H9NH3]4Cd3Cl10
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    Inorganic Chemistry (2014), 53 (17), 8913-8918CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    A layered org.-inorg. hybrid compd., tetra(cyclopentylammonium) decachlorotricadmate(II) (1), in which the two-dimensional [Cd3Cl10]n4- networks built up from three face-sharing CdCl6 octahedra are sepd. by cyclopentylammonium cation bilayers, was 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 DSC measurements, variable-temp. structural analyses, and dielec. measurements. The crystal structures of 1 detd. at 93, 298, and 343 K are solved in P212121, Pbca, and Cmca, resp. Crystallog. data are given. A precise anal. 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]n4- network.
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    Chen, H. P.; Shi, P. P.; Wang, Z. X.; Gao, J. X.; Zhang, W. Y.; Chen, C.; Tang, Y. Y.; Fu, D. W. Tunable Dielectric Transitions in Layered Organic-Inorganic Hybrid Perovskite-Type Compounds: [NH3(CH2)2Cl]2CdCl4–4xBr4x] (x = 0, 1/4, 1). Dalton Trans. 2018, 47 (20), 7005– 7012,  DOI: 10.1039/C8DT00353J
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    Tunable dielectric transitions in layered organic-inorganic hybrid perovskite-type compounds: [NH3(CH2)2Cl]2[CdCl4-4xBr4x] (x = 0, 1/4, 1)
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    Dalton Transactions (2018), 47 (20), 7005-7012CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    Mol. bistable dielec. switches represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light wts., and mech. flexibility. However, most of these switches can only work at a very low temp., extremely limiting their potential applications. Herein, three layered org.-inorg. hybrid perovskite-type compds. of the general formula A2BX4, [NH3(CH2)2Cl]2[CdCl3Br] (1), [NH3(CH2)2Cl]2[CdCl4] (2) and [NH3(CH2)2Cl]2[CdBr4] (3), which display sensitive dielec. switching reversibility and remarkable switching anti-fatigue, have been successfully designed. Differential scanning calorimetry and dielec. measurements for 1 confirm its reversible phase transition at around 166 K. Through anion modulation, the phase transition temps. of 2 and 3 can be greatly improved up to 237 K and 254 K, resp. Structural anal. discloses that the phase transition temp.'s shifts may result from the differences among the inorg. frameworks. Moreover, due to the significant order-disorder transitions of ammonium cations, the permittivities of 1, 2 and 3 change abruptly at around the phase transition points, making them excellent stimuli-responsive elec. switches. Such an anion-modulated method will open up new possibilities of highly efficiently tuning the phase transition temp. of mol. bistable dielec. switches.
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    In this report, two new hybrid org.-inorg. perovskite-type compds., (IBA)CdBr3 (1; IBA = isobutylammonium cation, i-C4H9-NH3) and (IBA)2CdBr4 (2), have been successfully synthesized by reasonable modulation of the ratio of the reactants. 1 With a one-dimensional (1D) chained structure presents sequential solid-state phase transitions, and 2 with a two-dimensional (2D) layered structure undergoes triple structural phase transitions. The phase transitions are attributable to the stepwise ordering process of the org. IBA cation of the title compds., which also exhibit temp.-dependent dielec. transitions and dielec. anisotropies. Among the different structural environments, the dynamic motions of org. cations show distinct differences, driving the variation of phys. properties.
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    An exptl. technique by using powders is described which permits the rapid classification of materials according to (a) magnitude of nonlinear optical coeffs., relative to a cryst. quartz standard and (b) existence or absence of phase matching direction(s) for 2nd-harmonic generation. Results are presented for a large no. of inorg. and org. substances including single-crystal data on phase-matched 2nd-harmonic generation in HIO3, KNbO3, PbTiO3, LiClO4.3H2O, and CO(NH2)2. HIO3 has a nonlinear coeff. d14 ∼ 1.5 × d31 LiNbO3. Since it is readily grown from water soln. and does not exhibit optical damage effects, this material should be useful for nonlinear device applications.
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    CaBaCo4O7 (CBCO) cobaltite shows a giant spin driven pyroelectric polarization below its ferrimagnetic transition temperature at 64 K. In the present study, we have investigated the structural, magnetic and electric polarization properties of light nonmagnetic Zn doped polycrystalline CaBaCo3.97Zn0.03O7 (CBCZO) cobaltite. Neutron powder diffraction studies on the CBCZO show that the Zn occupies the Co2 sites which lowers the strength of the magnetic interactions between the bitetrahedral cobalt c-axis chains. Further, we show that these chains act as magnetic clusters and causes the switching of the electric polarization. This study specifies that the ferrimagnetic-pyroelectric ground state of CBCO is very sensitive to the light non-magnetic doping and the results can be used to further understand the pyroelectric polarization switching properties of CBCO.
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    Combination of excellent optical properties and ferroelectricity of hybrid materials leads to high-performance optoelectronic devices. Here the authors present a new org.-inorg. hybrid compd. (diisopropylammonium)2MnBr4 (DIPA2MnBr4) which shows high temp. ferroelectricity accompanied by highly efficient green-light emission. DIPA2MnBr4 also exhibits sensitive and selective optical response to alc. vapors.
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    Gao, Long; Zhou, Yanling; Peng, Jinliang; Xu, Chen; Xu, Qing; Xing, Min; Chang, Jiang
    NPG Asia Materials (2019), 11 (1), 66CODEN: NAMPCE; ISSN:1884-4057. (Nature Research)
    Dual adhesiveness to tissue and implant biomaterials and bioactivity to stimulate tissue regeneration are interesting properties for developing new generations of tissue-repairing hydrogels with potential new clin. applications. In this study, we developed a unique bioglass (BG)/oxidized sodium alginate (OSA) composite hydrogel with adipic acid dihydrazide (ADH)-modified γ-polyglutamic acid (γ-PGA) as the crosslinking agent, in which the BG plays a multifunctional role to endow the hydrogel with both dual-adhesive and bioactive properties. On one hand, the BG could improve the tissue-bonding strength by providing an alk. microenvironment to stimulate the bond formation between OSA and the amino groups on the surrounding tissues. On the other hand, BG endows the hydrogel with adhesiveness to implantable materials by releasing Ca ions, which might chelate with the carboxyl groups of the hydrogel matrix. In addn., the composite hydrogel showed excellent bioactivity to promote vascularization and accelerate tissue regeneration. This study demonstrates that a multifunctional hydrogel can be designed by utilizing the multifunctional ions released from silicate BG, and the BG/OSA hydrogel shows good potential as an adhesive and bioactive material for wound-healing applications.
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    A near-room-temperature organic-inorganic hybrid ferroelectric: [C6H5CH2CH2NH3]2[CdI4]
    Huang, Bo; Sun, Lin-Ying; Wang, Sha-Sha; Zhang, Jian-Yu; Ji, Cheng-Min; Luo, Jun-Hua; Zhang, Wei-Xiong; Chen, Xiao-Ming
    Chemical Communications (Cambridge, United Kingdom) (2017), 53 (42), 5764-5766CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    An org.-inorg. hybrid compd., [C6H5CH2CH2NH3]2[CdI4], exhibits a reversible ferroelec. phase transition at 301/297 K. Switchable dielec. const., second harmonic generation, and pyroelectricity were synchronously obsd. accompanied by the order-disorder phase transition. This finding promotes research on mol. ferroelecs. to search for promising multifunctional switching materials at near room temp.
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  1. Bo-Wen Deng, Yang Zhu, Kun Ding, Jie Li, Meng-Meng Lun, Da-Wei Fu, Zhi-Xu Zhang. Homochiral Chemistry Strategy to Trigger Second-Harmonic Generation and Dual Dielectric Switches. Inorganic Chemistry 2023, 62 (29) , 11701-11707. https://doi.org/10.1021/acs.inorgchem.3c01640
  2. Magdalena Rok, Bartosz Zarychta, Grażyna Bator, Anna Piecha-Bisiorek. Screening Order–Disorder Phase Transition in 1-D Perovskite-like Crystals of [Azetidinium]CdBr3. The Journal of Physical Chemistry C 2022, 126 (44) , 18876-18884. https://doi.org/10.1021/acs.jpcc.2c05577
  3. Defu Sun, Duanliang Wang, Yangyang Dang, Shoubao Zhang, Hanzhang Chen, Ruoxian Hou, Kui Wu, Chuanying Shen. Organic–Inorganic Hybrid Noncentrosymmetric (Morpholinium)2Cd2Cl6 Single Crystals: Synthesis, Nonlinear Optical Properties, and Stability. Inorganic Chemistry 2022, 61 (20) , 8076-8082. https://doi.org/10.1021/acs.inorgchem.2c00922
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  8. Ying- Yu Zhang, Jia-Qi Luo, Yan Han, Wan-Ying Zhang, Yi Zhang, Hai-Feng Lu, Da-Wei Fu. Bistable switch molecule DPACdCl4 showing four physical channels and high phase transition temperature. Chinese Chemical Letters 2024, 25 , 109530. https://doi.org/10.1016/j.cclet.2024.109530
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  19. Teng‐Fei Cao, Hao Xiao, Zhi‐Huang Xu, Li‐Wang Ye, Yuan‐Jie Wang, Xin‐Xin Zhuang. Two Lead‐Free Organic‐Inorganic Hybrid Halides: Exploring Dielectric Switching and Photoluminescence Integrated in Crystals. European Journal of Inorganic Chemistry 2021, 2021 (38) , 3950-3955. https://doi.org/10.1002/ejic.202100567
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  23. Magdalena Rok, Bartosz Zarychta, Andrzej Bil, Joanna Trojan-Piegza, Wojciech Medycki, Andrzej Miniewicz, Anna Piecha-Bisiorek, Agnieszka Ciżman, Ryszard Jakubas. A multiaxial electrical switching in a one-dimensional organic–inorganic (pyrrolidinium) 2 Cd 2 I 6 ferroelectric and photoluminescent crystal. Journal of Materials Chemistry C 2021, 9 (24) , 7665-7676. https://doi.org/10.1039/D1TC01526E
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Inorganic Chemistry

Cite this: Inorg. Chem. 2020, 59, 17, 11986–11994
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https://doi.org/10.1021/acs.inorgchem.0c00830
Published August 15, 2020

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  • Abstract

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    Scheme 1

    Scheme 1. Schematic Projection of Inorganic Structures Adopted by Ferroelectric Halocadmates
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    Figure 1

    Figure 1. DSC runs obtained upon heating and cooling scans for DPAC (sample mass m = 5.812 mg). Black arrows show the directions of runs (cooling or heating at 10 K/min).

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    Figure 2

    Figure 2. (a) Crystal packing of phase II of DPAC viewed along the a axis. Movements of the component ions on going from phase I (red atoms and bonds) to phase II (blue or green atoms and bonds; for the sake of clarity only the nitrogen and cadmium atoms have been labeled). (b) Rotation of [CdBr4]2–. The anion from phase I has been shifted so that both Cd atoms overlap. (c) Rotation of the N1 cation along the [100] direction. (d) Transformation of the N2 cation. The (001) plane is perpendicular to the diagram and the N2–N2 direction. (e) Transformation of the N3 cation. The superscript i denotes a −x, −y, z symmetry operation; the [010] direction runs vertically.

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    Figure 3

    Figure 3. Plot of the integral intensity of the SHG signal of DPAC between 235 and 287 K measured on cooling.

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    Figure 4

    Figure 4. Temperature dependence of the real (a) and imaginary (b) parts of the complex electric permittivity, ε* = ε′ – iε′′, at selected frequencies in the vicinity of PT at 244 K for the polycrystalline sample of DPAC. A dotted line indicates the PT temperature. Inset: ε′ measured at 2 MHz. (c) Arrhenius plot for the macroscopic dielectric relaxation time, ln τ vs 1/T, for DPAC in phase I (red circles) and in phase II (blue circles).

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    Figure 5

    Figure 5. (a) Temperature dependence of Ptotal and ΔPs after poling by an external electric field (+10 kV/cm, red line; −10 kV/cm, blue line). (b) P–E hysteresis loops obtained at 215 K in phase II.

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    Scheme 2

    Scheme 2. Packing Diagram of Organic (C6H16N)+ Cations Viewed along the a Axis with Schematically Marked Dipole Moments
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    Figure 6

    Figure 6. dc conductivity, σdc, for DPAC plotted versus reciprocal temperature, 1000/T.

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  • References

    This article references 60 other publications.

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      Broadband Emission in a New Two-Dimensional Cd-Based Hybrid Perovskite
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      Org.-inorg. hybrid perovskites (OIHP) are developing rapidly as high-performance semiconductors for solid-state solar cells and light emitting devices. Recently, lead-halide two-dimensional (2D) OIHP were found to present bright broadband visible emission, thus, highlighting their potential as single component white-light (WL) emitters. This contribution deals with the prepn. of a new Cd-based 2D hybrid perovskite, of the chem. formula (C6H11NH3)2CdBr4 (abbreviated as compd. 1), of which structural and optical properties have been studied and analyzed. Room temp. optical absorption (OA) measurements, performed on spin-coated film of compd. 1, revealed a sharp excitonic absorption peak at 3.24 eV, and a large exciton binding energy of 377 meV, estd. from low temp. OA spectrum. Upon 325 nm irradn., compd. 1 showed a very broadband WL emission consisting of one peak at 2.94 eV, attributed to exciton confined in the [CdBr4]2- inorg. layers, and a second peak at 2.53 eV resulting from the cyclohexylammonium cations emission. Temp. dependence of PL spectra evidenced anomalous behavior accompanied by singularities around 50 and 150 K in the integrated intensity, the full width at half-max. and the PL peaks positions. These singularities have been traced back to structural phase transitions, from temp. dependence powder and single crystal X-ray diffraction investigations, from which strong correlations had emerged between the structural distortion of the CdBr6 pseudo-octahedron and the broadening characteristics of the WL emission band. These hitherto unrecognized properties turn this and similar OIHP into perspective candidates for potential applications as WL-emitting diodes.
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      Roccanova, R.; Ming, W.; Whiteside, V. R.; McGuire, M. A.; Sellers, I. R.; Du, M. H.; Saparov, B. Synthesis, Crystal and Electronic Structures, and Optical Properties of (CH3NH3)2CdX4 (X = Cl, Br, I). Inorg. Chem. 2017, 56 (22), 13878– 13888,  DOI: 10.1021/acs.inorgchem.7b01986
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      Synthesis, Crystal and Electronic Structures, and Optical Properties of (CH3NH3)2CdX4 (X = Cl, Br, I)
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      The synthesis, crystal and electronic structures, and optical properties of the hybrid org.-inorg. compds. MA2CdX4 (MA = MeNH3; X = Cl, Br, I) are reported. MA2CdI4 is a new compd., whereas, for MA2CdCl4 and MA2CdBr4, structural studies have already been conducted but electronic structures and optical properties are reported here for the 1st time. Single crystals were grown through slow evapn. of MA2CdX4 solns. with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals. Single crystal and variable temp. powder x-ray diffraction measurements suggest that MA2CdCl4 forms a 2D layered perovskite structure and has 2 structural transitions at 283 and 173 K. But MA2CdBr4 and MA2CdI4 adopt 0D K2SO4-derived crystal structures based on isolated CdX4 tetrahedra and show no phase transitions down to 20 K. The contrasting crystal structures and chem. compns. in the MA2CdX4 family impact their air stabilities, studied for the 1st time MA2CdCl4 is air-stable, whereas MA2CdBr4 and MA2CdI4 partially decomp. when left in air. Optical absorption measurements suggest that MA2CdX4 have large optical band gaps >3.9 eV. Room temp. luminescence of MA2CdX4 yield broad peaks in the 375-955 nm range with full width at half-max. values up to 208 nm. These PL peaks are tentatively assigned to self-trapped excitons in MA2CdX4 following the crystal and electronic structure considerations. The bands around the Fermi level have small dispersions, which is indicative of high charge localization with significant exciton binding energies in MA2CdX4. From the combined exptl. and computational results, MA2CdX4 and related compds. may be of interest for white-light-emitting phosphors and scintillator applications.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslClsr7P&md5=202816d75b7667a2aa30c01b6a092f85
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      Wang, S.; Li, L.; Sun, Z.; Ji, C.; Liu, S.; Wu, Z.; Zhao, S.; Zeb, A.; Hong, M.; Luo, J. A Semi-Conductive Organic-Inorganic Hybrid Emits Pure White Light with an Ultrahigh Color Rendering Index. J. Mater. Chem. C 2017, 5 (19), 4731– 4735,  DOI: 10.1039/C7TC00279C
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      A semi-conductive organic-inorganic hybrid emits pure white light with an ultrahigh color rendering index
      Wang, Sasa; Li, Lina; Sun, Zhihua; Ji, Chengmin; Liu, Sijie; Wu, Zhenyue; Zhao, Sangen; Zeb, Aurang; Hong, Maochun; Luo, Junhua
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2017), 5 (19), 4731-4735CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      White-light emission has evoked great attention as one of the most promising technologies in the applications of solid-state lighting devices, light emitting diodes, and flat-panel displays. However pure white-light emitting materials have rarely been reported. Here, the authors present a single-component white-light emitting semiconductor, [C5H9-NH3]4CdBr6, which exhibits CIE chromaticity coordinates of (0.33, 0.33). Notably, this value is the same as that of the std. pure white-light emission. Remarkably, it shows an ultrahigh color rendering index of 92.5, which exceeds that of mixed-phosphor light sources and is comparable to the recently reported highest one among single-component materials. Mechanistic studies indicate that the white-light emission originates from the synergetic effect of deep defects coupled with the org. component. Such an org.-inorg. hybrid with outstanding color characteristics will pave a new approach in the development of white-light emitting materials with practical applications.
      >> More from SciFinder ®
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      Wojciechowska, M.; Gagor, A.; Piecha-Bisiorek, A.; Jakubas, R.; Cizman, A.; Zaręba, J. K.; Nyk, M.; Zieliński, P.; Medycki, W.; Bil, A. Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium)3[Sb2Cl9]. Chem. Mater. 2018, 30, 4597– 4608,  DOI: 10.1021/acs.chemmater.8b00962
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      Ferroelectricity and ferroelasticity in organic inorganic hybrid (pyrrolidinium)3[Sb2Cl9]
      Wojciechowska, Martyna; Gagor, Anna; Piecha-Bisiorek, Anna; Jakubas, Ryszard; Cizman, Agnieszka; Zareba, Jan K.; Nyk, Marcin; Zielinski, Piotr; Medycki, Wojciech; Bil, Andrzej
      Chemistry of Materials (2018), 30 (14), 4597-4608CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Perovskite-like materials exhibit desirable photophys. and elec. properties that make them suitable for a remarkable breadth of applications in electronics and physics. In this contribution, the authors report on the multiphase ferroelec. and ferroelastic phenomena in a pyrrolidinium-based hybrid metal-org. material: (C4H8NH2)3[Sb2Cl9]. The title compd. is the first pyrrolidinium deriv. within the halobismuthates(III) and haloantimonates(III) families that is featured by the ferroelec. property. From a structural point of view, the crystal structure is built of [Sb2Cl9]3-∞ perovskite-like layers, interdigitated by layers of pyrrolidinium cations. The rich solid-state dynamics of pyrrolidinium cations endowed (C4H8NH2)3[Sb2Cl9] with a complex sequence of temp.-dependent phase transitions. Remarkably, polar properties have been found to occur in all six phases, including room-temp. Phase I. Insights from variable-temp. single-crystal x-ray diffraction, dielec. spectroscopy, and T1 spin-lattice relaxation measurements revealed the general mechanism of most phase transitions, as related to the progressive ordering of nonequivalent pyrrolidinium cations. Noncentrosymmetry is probed by room-temp. second harmonic generation (SHG), while the ferroelec. property was evidenced through P(E) and dielec. measurements. The exptl. values of spontaneous polarization were justified and analyzed in the context of theor. values derived from quantum-chem. calcns. Optical measurements show that the integrity of the sample survives all of the phase transitions, despite sometimes significant deformations of the unit cell. The changes of symmetry assocd. with structural phase transitions are accompanied by an intriguing evolution of the ferroelastic domain structure with temp.
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      Ye, H. Y.; Zhou, Q.; Niu, X.; Liao, W. Q.; Fu, D. W.; Zhang, Y.; You, Y. M.; Wang, J.; Chen, Z. N.; Xiong, R. G. High-Temperature Ferroelectricity and Photoluminescence in a Hybrid Organic-Inorganic Compound: (3-Pyrrolinium)MnCl3. J. Am. Chem. Soc. 2015, 137 (40), 13148– 13154,  DOI: 10.1021/jacs.5b08290
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      High-Temperature Ferroelectricity and Photoluminescence in a Hybrid Organic-Inorganic Compound: (3-Pyrrolinium)MnCl3
      Ye, Heng-Yun; Zhou, Qiong-Hua; Niu, Xiang-Hong; Liao, Wei-Qiang; Fu, Da-Wei; Zhang, Yi; You, Yu-Meng; Wang, Jinlan; Chen, Zhong-Ning; Xiong, Ren-Gen
      Journal of the American Chemical Society (2015), 137 (40), 13148-13154CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Coupling of ferroelectricity and optical properties has become an interesting aspect of material research. The switchable spontaneous polarization in ferroelecs. provides an alternative way to manipulate the light-matter interaction. The recent observation of strong photoluminescence emission in ferroelec. hybrid org.-inorg. compds., (pyrrolidinium)MnX3 (X = Cl or Br), is an attractive approach to high efficiency luminescence with the advantages of ferroelectricity. However, (pyrrolidinium)MnX3 only displays ferroelectricity near or below room temp., which limits its future applications in optoelectronics and multifunctional devices. Here, we rationally designed and synthesized high-temp. luminescent ferroelec. materials. The new hybrid compd. (3-pyrrolinium)MnCl3 has a very high Curie temp., Tc = 376 K, large spontaneous electronic polarization of 6.2 μC/cm2, and high fatigue resistance, as well as high emission efficiency of 28%. This finding is a further step to the practical use of ferroelec. luminescence based on org.-inorg. compds.
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      Zhang, Y.; Liao, W. Q.; Fu, D. W.; Ye, H. Y.; Chen, Z. N.; Xiong, R. G. Highly Efficient Red-Light Emission in an Organic-Inorganic Hybrid Ferroelectric: (Pyrrolidinium)MnCl3. J. Am. Chem. Soc. 2015, 137 (15), 4928– 4931,  DOI: 10.1021/jacs.5b01680
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      Highly Efficient Red-Light Emission in An Organic-Inorganic Hybrid Ferroelectric: (Pyrrolidinium)MnCl3
      Zhang, Yi; Liao, Wei-Qiang; Fu, Da-Wei; Ye, Heng-Yun; Chen, Zhong-Ning; Xiong, Ren-Gen
      Journal of the American Chemical Society (2015), 137 (15), 4928-4931CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Luminescence of ferroelec. materials is 1 important property for technol. applications, such as low-energy electron excitation. The vast majority of doped inorg. ferroelec. materials have low luminescent efficiency. The past decade has envisaged much progress in the design of both ferroelec. and luminescent org.-inorg. hybrid complexes for optoelectronic applications. The combination of ferroelectricity and luminescence within org.-inorg. hybrids would lead to a new type of luminescent ferroelec. multifunctional materials. A hybrid mol. ferroelec., (pyrrolidinium)MnCl3, exhibits excellent ferroelectricity with a satn. polarization of 5.5 μC/cm2 and intense red luminescence with high quantum yield of 56% under a UV excitation. This finding may extend the application of org.-inorg. hybrid compds. to the field of ferroelec. luminescence and/or multifunctional devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1Wmurg%253D&md5=6f56e7d955822afaec0e65c6b7a58eed
    7. 7
      Zeb, A.; Sun, Z.; Khan, T.; Asghar, M. A.; Wu, Z.; Li, L.; Ji, C.; Luo, J. CdCl3: An ABX3 Perovskite-Type Semiconducting Switchable Dielectric Phase Transition Material. Inorg. Chem. Front. 2017, 4, 1485– 1492,  DOI: 10.1039/C7QI00301C
      7
      [C5H12N]CdCl3: an ABX3 perovskite-type semiconducting switchable dielectric phase transition material
      Zeb, Aurang; Sun, Zhihua; Khan, Tariq; Asghar, Muhammad Adnan; Wu, Zhenyue; Li, Lina; Ji, Chengmin; Luo, Junhua
      Inorganic Chemistry Frontiers (2017), 4 (9), 1485-1492CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      A new org.-inorg. ABX3 perovskite-type semiconducting hybrid, N-methylpyrrolidinium trichlorocadmate (MPCC), has been synthesized. It is found that MPCC exhibits the semiconducting behavior with the optical bandgap of ∼4.65 eV, as well as remarkable dielec. switching properties. It displays a structural phase transition (SPT) at Tc = 254 K, being confirmed by DSC and sp. heat measurements. Dielec. measurements display distinct step-like anomalies around the Tc, suggesting MPCC as a switchable dielec. material. Variable temps. single-crystal X-ray diffraction reveal that symmetry-breaking occurs from Pnma (at 280 K, > Tc) to P21/c (at 230 K, < Tc), which is attributed to the ordering of the disordered N-methylpyrrolidinium (MP) cation. The most distinct difference between its low- and high-temp. structures is the order-disorder dynamics of MP cation, which mainly contribute to the SPT and switchable dielec. activities of MPCC. This finding paves a new way for designing multi-featured ABX3 type SPT hybrids by choosing disordered cationic moieties.
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    8. 8
      Rok, M.; Bator, G.; Zarychta, B.; Dziuk, B.; Repeć, J.; Medycki, W.; Zamponi, M.; Usevičius, G.; Simenas, M.; Banys, J. Isostructural Phase Transition, Quasielastic Neutron Scattering and Magnetic Resonance Studies of Bistable Dielectric Ion-Pair Crystal [(CH3)2NH2]2KCr(CN)6. Dalton Trans. 2019, 48, 4190– 4202,  DOI: 10.1039/C8DT05082A
      8
      Isostructural phase transition, quasielastic neutron scattering and magnetic resonance studies of a bistable dielectric ion-pair crystal [(CH3)2NH2]2KCr(CN)6
      Rok, M.; Bator, G.; Zarychta, B.; Dziuk, B.; Repec, J.; Medycki, W.; Zamponi, M.; Usevicius, G.; Simenas, M.; Banys, J.
      Dalton Transactions (2019), 48 (13), 4190-4202CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      We have synthesized and characterized a novel org.-inorg. hybrid crystal, [(CH3)2NH2]2KCr(CN)6. The thermal DSC, TMA, DTG and DTA analyses indicate two solid-to-solid structural phase transitions (PTs). According to the X-ray diffraction expts., the first PT at 220 K is isostructural, since it does not involve a change of the space group. This transition occurs between the states, where the (CH3)2NH2+ cations are orientationally disordered and ordered (frozen). The other reversible PT at 481 K leads to a melt-like phase similar to the one obsd. in plastic crystals or polar liqs. Dielec. spectroscopy has been used to characterize the switching properties of the dipole moments in the vicinity of the PTs. Continuous-wave ESR spectroscopy was employed to investigate the effect of ordering on the local environment of the Cr3+ ions. We have also applied the quasielastic neutron scattering (QENS) technique as well as 1H NMR spectroscopy to measure the dynamics of the (CH3)2NH2+ cations residing in the inorg. framework.
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    9. 9
      Rok, M.; Moskwa, M.; Działowa, M.; Bieńko, A.; Rajnák, C.; Boča, R.; Bator, G. Multifunctional Materials Based on the Double-Perovskite Organic-Inorganic Hybrid (CH3NH3)2[KCr(CN)6] Showing Switchable Dielectric, Magnetic, and Semi-conducting Behaviour. Dalton Trans. 2019, 48 (44), 16650– 16660,  DOI: 10.1039/C9DT03553B
      9
      Multifunctional materials based on the double-perovskite organic-inorganic hybrid (CH3NH3)2[KCr(CN)6] showing switchable dielectric, magnetic, and semiconducting behavior
      Rok, M.; Moskwa, M.; Dzialowa, M.; Bienko, A.; Rajnak, C.; Boca, R.; Bator, G.
      Dalton Transactions (2019), 48 (44), 16650-16660CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      The authors synthesize and characterize a novel org.-inorg. hybrid crystal, [CH3NH3]2KCr(CN)6 (MACr). Thermal anal. (DSC, TGA-DTA) indicates one structural phase transition (PT) at 450 K. The modified equation of the tolerance factor, t, was used to est. the theor. PT temp. for a crystal with Mn(III). According to the x-ray diffraction expt., in the low-temp. (LT) phase, the solid-to-solid PT is described by the monoclinic space group C2/c. The creation of the ferroelastic domain structure in phase II was proved on the basis of the observation under a polarizing microscope. The crystals of MACr and its isomorphous analogs with Fe(III) and Co(III) appeared to be semiconducting materials in the LT phase. The type of PT is order-disorder and occurs between "low" (ordered-frozen) and "high" (orientationally disordered) dielec. states. Dielec. spectroscopy was used to characterize the switching properties of the dipole moments in the vicinity of the PTs. The magnetic properties of the MACr hybrid were investigated in DC and AC modes. The DC data show a sizeable weak exchange interaction between the nearest Cr(III) centers in the crystal lattice. The AC susceptibility data confirm a slow magnetic relaxation in the applied DC field with two relaxation channels. The low-frequency relaxation time is very long as τLF = 1.4(1) s at T = 2.0 K. The org.-inorg. hybrid, described above, can be considered a rare example of multifunctional materials which exhibit dielec., magnetic and conductive activities.
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    10. 10
      Xu, C.; Zhang, W. Y.; Chen, C.; Ye, Q.; Fu, D. W. Fast and Slow Integrated Single-Molecule Dual Dielectric Switch Based on a Crystal/Flexible Thin Film. J. Mater. Chem. C 2017, 5, 6945– 6953,  DOI: 10.1039/C7TC02087B
      10
      Fast and slow integrated single-molecule dual dielectric switch based on a crystal/flexible thin film
      Xu, Chang; Zhang, Wan-Ying; Chen, Cheng; Ye, Qiong; Fu, Da-Wei
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2017), 5 (28), 6945-6953CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Smart plastic crystals/films based on org.-inorg. hybrid materials are rarely reported in the form of highly-integrated intelligent controllable dielec. switches (switching between ON/OFF or "1"/"0"), esp. tunable switches with dual ON/OFF effects that are integrated in a single mol. Herein, two superior plastic crystals, [C6H15ClNO]2[MCl4] (M = Cd for 1, Mn for 2), which are able to exhibit tunable and dual dielec. switching characteristics between three stages triggered by temp. (LTP, RTP and HTP) in a single mol., were successfully synthesized and prepd. as ultraflexible and monodirectional thin films. Such excellent features lay the foundation for their applications in temp.-adjustable multifunctional single-mol. sensors and memory devices. Specifically, through control of the operating temp., the fast dielec. switch (high temp. phase transition stage) and the slow/delayed dielec. switch (low temp. phase transition stage) can be integrated in a single mol. device cell. As well as the superior stability/fatigue resistance of the crystals, the facile/environmentally-friendly fabrication of the thin films makes 1 and 2 excellent candidates for single-mol. intelligent devices and highly-integrated dual-switching devices in the modern electronic information industry.
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    11. 11
      Lv, X. H.; Liao, W. Q.; Li, P. F.; Wang, Z. X.; Mao, C. Y.; Zhang, Y. Dielectric and Photoluminescence Properties of a Layered Perovskite-Type Organic-Inorganic Hybrid Phase Transition Compound: NH3(CH2)5NH3MnCl4. J. Mater. Chem. C 2016, 4 (9), 1881– 1885,  DOI: 10.1039/C5TC04114G
      11
      Dielectric and photoluminescence properties of layered perovskite-type organic-inorganic hybrid phase transition compound: NH3(CH2)5NH3MnCl4
      Lv, Xing-Hui; Liao, Wei-Qiang; Li, Peng-Fei; Wang, Zhong-Xia; Mao, Chen-Yu; Zhang, Yi
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2016), 4 (9), 1881-1885CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      A layered perovskite-type org.-inorg. hybrid compd., 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, dielec. measurements and variable-temp. structural analyses reveal that compd. 1 undergoes a reversible phase transition at 298 K, accompanied by switchable dielec. responses between high and low states and remarkable anisotropy along the various crystallog. axes. Such distinctive dielec. performances mean that 1 could be regarded as a potential switchable dielec. material. Significantly, an intriguing orange emission band at 581 nm can be obsd. under UV excitation, which is ascribed to the octahedral Mn2+ ion. This finding may extend the application of org.-inorg. hybrids in the field of switchable dielec. materials.
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    12. 12
      Wei, Z.; Liao, W. Q.; Tang, Y. Y.; Li, P. F.; Shi, P. P.; Cai, H.; Xiong, R. G. Discovery of an Antiperovskite Ferroelectric in [(CH3)3NH]3(MnBr3)(MnBr4). J. Am. Chem. Soc. 2018, 140 (26), 8110– 8113,  DOI: 10.1021/jacs.8b05037
      12
      Discovery of an antiperovskite ferroelectric in [(CH3)3NH]3(MnBr3)(MnBr4)
      Wei, Zhenhong; Liao, Wei-Qiang; Tang, Yuan-Yuan; Li, Peng-Fei; Shi, Ping-Ping; Cai, Hu; Xiong, Ren-Gen
      Journal of the American Chemical Society (2018), 140 (26), 8110-8113CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      It is known that perovskites with the general chem. formula of ABX3 (A, B = cations, X = anion) have been intensively studied over the last half century because of their diverse functional properties, such as ferroelectricity in BaTiO3, piezoelectricity in PZT (lead zirconate titanate), and recently developed photovoltaic properties in CH3NH3PbI3. However, rather less attention has been paid to their "inverse" analogs, antiperovskites, which have a chem. formula X3BA, where A and B are anions and X is a cation. Although most of important ferroelecs. are perovskites, no antiperovskite ferroelecs. have been found since the discovery of antiperovskites in 1930. Here, for the first time, we report a X3BA antiperovskite ferroelec. [(CH3)3NH]3(MnBr3)(MnBr4) (where (CH3)3NH is X, MnBr3 is B, and MnBr4 is A), which shows outstanding ferroelectricity with a significantly high phase transition temp. of 458 K as well as fascinating photoluminescence properties with two intense emissions. This finding opens a new avenue to explore the golden area of antiperovskites for high-performance functional materials.
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    13. 13
      Li, P. F.; Liao, W. Q.; Tang, Y. Y.; Ye, H. Y.; Zhang, Y.; Xiong, R. G. Unprecedented Ferroelectric-Antiferroelectric-Paraelectric Phase Transitions Discovered in an Organic-Inorganic Hybrid Perovskite. J. Am. Chem. Soc. 2017, 139 (25), 8752– 8757,  DOI: 10.1021/jacs.7b04693
      13
      Unprecedented ferroelectric-antiferroelectric-paraelectric phase transitions discovered in an organic-inorganic hybrid perovskite
      Li, Peng-Fei; Liao, Wei-Qiang; Tang, Yuan-Yuan; Ye, Heng-Yun; Zhang, Yi; Xiong, Ren-Gen
      Journal of the American Chemical Society (2017), 139 (25), 8752-8757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      As a promising candidate for energy storage capacitors, antiferroelec. (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization vs. elec. field (P-E) hysteresis characteristics in contrast to ferroelecs. and linear dielecs. However, antiferroelectricity has only been discovered in inorg. oxides and some hydrogen-bonded mol. systems. In view of the structural diversity and unique phys. properties of org.-inorg. hybrid system, it remains a great opportunity to introduce antiferroelectricity into org.-inorg. hybrid perovskites. Here, the authors report that polarizable antiparallel dipole arrays can be realized in an org.-inorg. hybrid perovskite, (3-pyrrolinium)CdBr3, which not only exhibits an excellent ferroelec. 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 their knowledge, it is the first time that such successive ferroelec.-antiferroelec.-paraelec. phase transitions have been discovered in org.-inorg. perovskites. Besides, a giant dielec. const. 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 obsd. during the phase transition. Apparently, the combined striking AFE characteristic and giant dielec. const. make (3-pyrrolinium)CdBr3 a promising candidate for next generation high-energy-storage capacitors.
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    14. 14
      Zhang, Y.; Liao, W. Q.; Fu, D. W.; Ye, H. Y.; Liu, C. M.; Chen, Z. N.; Xiong, R. G. The First Organic-Inorganic Hybrid Luminescent Multiferroic: (Pyrrolidinium)MnBr3. Adv. Mater. 2015, 27 (26), 3942– 3946,  DOI: 10.1002/adma.201501026
      14
      The First Organic-Inorganic Hybrid Luminescent Multiferroic: (Pyrrolidinium)MnBr3
      Zhang, Yi; Liao, Wei-Qiang; Fu, Da-Wei; Ye, Heng-Yun; Liu, Cai-Ming; Chen, Zhong-Ning; Xiong, Ren-Gen
      Advanced Materials (Weinheim, Germany) (2015), 27 (26), 3942-3946CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      By rational design and chem. synthesis, a new hybrid ferroelec. luminescent material, pyrrolidinium tribromomanganate, with a perovskite structure was obtained. A strong PL emission is obsd. at 640 nm with QE of 28.5% and emission lifetime of ∼0.1 ms. Such 2-H stacking perovskite has the advantage of structural tunability by adjusting the templating cations or the bridging atoms, as reported recently. Combining the luminescent property, structural, flexibility, and muitiferroicity the studies provide a new approach to fabricate multifunctional magnetooptoelectronic devices, which could eventually benefit the applications of magnetooptoelectronics and photovoltaics.
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    15. 15
      Cai, H. L.; Zhang, Y.; Fu, D. W.; Zhang, W.; Liu, T.; Yoshikawa, H.; Awaga, K.; Xiong, R. G. Above-Room-Temperature Magnetodielectric Coupling in a Possible Molecule-Based Multiferroic: Triethylmethylammonium Tetrabromoferrate(III). J. Am. Chem. Soc. 2012, 134 (45), 18487– 18490,  DOI: 10.1021/ja3073319
      15
      Above-Room-Temperature Magnetodielectric Coupling in a Possible Molecule-Based Multiferroic: Triethylmethylammonium Tetrabromoferrate(III)
      Cai, Hong-Ling; Zhang, Yi; Fu, Da-Wei; Zhang, Wen; Liu, Tao; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen
      Journal of the American Chemical Society (2012), 134 (45), 18487-18490CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A possible above-room-temp. mol. multiferroic, triethylmethylammonium tetrabromoferrate(III) (1), has been discovered. Its ferroelec. and magnetic phase transitions take place at almost the same temp. (∼360 K), resulting in strong magnetodielec. (MD) coupling, with a MD ratio of 18% at 0.6 MHz. Interestingly, 1 also undergoes a low-temp. ferroelec.-ferroelec. phase transition with an Aizu notation of 6mmF6 and small magnetic and dielec. anomalies at 171 K.
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    16. 16
      Mei, G. Q.; Liao, W. Q. Structural Phase Transitions Coupled with Prominent Dielectric Anomalies and Dielectric Relaxation in a One-Dimensional Organic-Inorganic Hybrid Compound [C3H4NS][CdCl3]. J. Mater. Chem. C 2015, 3 (33), 8535– 8541,  DOI: 10.1039/C5TC02023A
      16
      Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in a one-dimensional organic-inorganic hybrid compound [C3H4NS][CdCl3]
      Mei, Guang-Quan; Liao, Wei-Qiang
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (33), 8535-8541CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      A new 1-dimensional chlorocadmate(II) compd. contg. linear chains of face-sharing CdCl6 octahedra, thiazolium trichlorocadmate(II), exhibits one isostructural phase transition at 288 K and another symmetry-breaking phase transition at 215 K, accompanied by noteworthy dielec. anomalies and relaxation. Its phase transitions and dielec. responses were studied by DSC measurements, variable-temp. structural analyses, and dielec. measurements. The crystal structures detd. at 328, 253, and 173 K were solved in Cmcm, Cmcm, and C2/m, resp. The most distinct differences between these structures are the changes in the dynamics of thiazolium cations, which remain disordered in each structure. The isostructural transition can be ascribed to the slowing down of the mol. motions of thiazolium cations, while the symmetry-breaking one can be attributed to the reorientation of the cation. Two types of dielec. anomalies and one polydispersive dielec. relaxation process are clearly obsd. during the phase transitions. Such exceptional dielec. performances are also assocd. with the dynamic behaviors of the dipolar thiazolium cations.
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    17. 17
      Jakubas, R.; Sobczyk, L. Phase Transitions in Alkylammonium Halogenoantimonates and Bismuthates. Phase Transitions 1990, 20, 163– 193,  DOI: 10.1080/01411599008206873
      17
      Phase transitions in alkylammonium halogenoantimonates and bismuthates
      Jakubas, Ryszard; Sobczyk, Lucjan
      Phase Transitions (1990), 20 (3-4), 163-93CODEN: PHTRDP; ISSN:0141-1594.
      A review with many refs. of the results of studies on the structure, phase transitions and phys. properties of alkylammonium halogenoantimonates(III) and bismuthates(III). The crystals of these compds. are characterized by a variety of anionic structures and show a no. of phase transitions including those to polar phases. Dielec. and pyroelec. properties, spontaneous polarization and DSC studies are discussed. The mechanism of the phase transitions is discussed based on the results of x-ray, dielec. relaxation, PMR, IR and R spectra studies gathered so far. A particular role is played by a reorientational motion of the alkylammonium cations.
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    18. 18
      Jakubas, R.; Sobczyk, L. Ferroelectric Phase Transitions in Alkylammonium Halogenoantimonates (III). Ferroelectrics 1988, 78 (1), 69– 78,  DOI: 10.1080/00150198808215890
      18
      Ferroelectric phase transitions in alkylammonium halogenoantimonates(III)
      Jakubas, R.; Sobczyk, L.
      Ferroelectrics (1988), 78 (), 69-78CODEN: FEROA8; ISSN:0015-0193.
      A no. of crystals which exhibit dielec. anomalies and are composed of nonahalogenodiantimonate anion and alkylammonium cations of general formula [NH4-n(CH3)n]Sb2X9 (X = Cl, Br) were grown. Ferroelec. phase transitions were found in [(Me)2NH2]3Sb2Cl9, [Me3NH]3Sb2Cl9 and [Me2NH2]3Sb2Br9. X-ray diffraction, dielec., NMR and IR studies show that the order-disorder phase transitions are related to a motion of alkylammonium cations.
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    19. 19
      Zaleski, J.; Jakubas, R.; Galewski, Z.; Sobczyk, L. Structural Phase Transitions in [(C2H5)4N]3Sb2Br9 and [(C2H5)4N]3Bi2Br9. Z. Naturforsch., A: Phys. Sci. 1989, 44a, 1102– 1106,  DOI: 10.1515/zna-1989-1110
      There is no corresponding record for this reference.
    20. 20
      Piecha, A.; Pietraszko, A.; Bator, G.; Jakubas, R. Structural Characterization and Ferroelectric Ordering in (C3N2H5)5Sb2Br11. J. Solid State Chem. 2008, 181, 1155– 1166,  DOI: 10.1016/j.jssc.2008.02.029
      20
      Structural characterization and ferroelectric ordering in (C3N2H5)5Sb2Br11
      Piecha, A.; Pietraszko, A.; Bator, G.; Jakubas, R.
      Journal of Solid State Chemistry (2008), 181 (5), 1155-1166CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
      A ferroelec. crystal (C3N2H5)5Sb2Br11 has been synthesized. The single crystal X-ray diffraction studies (at 300, 155, 138 and 121 K) show that it is built up of discrete corner-sharing bioctahedral Sb2Br115- and highly disordered imidazolium cations. The room temp. crystal structure has been detd. as monoclinic, space group, P21/n with: a = 9.139 Å, b = 15.150 Å and c = 13.969 Å and β = 96.19°. The crystal undergoes three solid-solid phase transitions: (tetragonal) 354/352↔ P21/n (I ↔ II) discontinuous, P21/n 145↔ Pn (II ↔ III) continuous and Pn 120/135↔ Pn (III ↔ IV) discontinuous. The dielec. and pyroelec. measurements allow us to characterize the low temp. phases III and IV as ferroelec. with the Curie point at 145 K and the satd. spontaneous polarization value of the order of 1.8 × 10-3 Cm-2 along the a-axis (135 K). The ferroelec. phase transition mechanism at 145 K is due to the dynamics of imidazolium cations.
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    21. 21
      Scott, J. F. Applications of Modern Ferroelectrics. Science 2007, 315 (5814), 954– 959,  DOI: 10.1126/science.1129564
      21
      Applications of modern ferroelectrics
      Scott, J. F.
      Science (Washington, DC, United States) (2007), 315 (5814), 954-959CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      A review. Long viewed as a topic in classical physics, ferroelectricity can be described by a quantum mech. ab initio theory. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. Recent prototype applications include ultrafast switching, cheap room-temp. magnetic-field detectors, piezoelec. nanotubes for microfluidic systems, electrocaloric coolers for computers, phased-array radar, and 3D trenched capacitors for dynamic random access memories. Terabit-per-square-inch ferroelec. arrays of PZT were reported on Pt nanowire interconnects and nanorings with 5-nm diams. Finally, electron emission from ferroelecs. yields cheap, high-power microwave devices and miniature x-ray and neutron sources.
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    22. 22
      Wojtaś, M.; Reece, M. J. Dynamics of Ferroelectric Switching of [H3CNH3]5[Bi2Br11]. J. Appl. Phys. 2012, 111 (2), 024108-1-6
      There is no corresponding record for this reference.
    23. 23
      Piecha, A.; Białońska, A.; Jakubas, R. Structure and Ferroelectric Properties of [C3N2H5]5[Bi2Br11]. J. Phys.: Condens. Matter 2008, 20, 325224– 325233,  DOI: 10.1088/0953-8984/20/32/325224
      23
      Structure and ferroelectric properties of [C3N2H5]5[Bi2Br11]
      Piecha, A.; Bialonska, A.; Jakubas, R.
      Journal of Physics: Condensed Matter (2008), 20 (32), 325224/1-325224/9CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
      A ferroelec. crystal [C3N2H5]5[Bi2Br11] has been synthesized and structurally characterized at 170 and 100 K. The crystal structure consists of discrete corner-sharing bioctahedra [Bi2Br11]5- and highly disordered imidazolium cations. The room temp. crystal structure has been detd. as monoclinic, space group, P21/n with: a = 9.257(2) Å, b = 15.157(3) Å, c = 13.865(3) Å and β = 97.73(3)°. The crystal undergoes two solid-solid phase transitions: at 355 K of first-order and at 155 K of second-order type. The later transition takes place between monoclinic phases: P21/n → Pn. The dielec. and pyroelec. measurements allow us to characterize the low temp. phase III as ferroelec. with the Curie temp. at 155 K. The satd. spontaneous polarization of the order of 2.6 × 10-3 C m-2 was measured along the a-axis (130 K). The ferroelec. phase transition mechanism at 155 K is due to the dynamics of three of five nonequivalent imidazolium cations.
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    24. 24
      Szklarz, P.; Gągor, A.; Jakubas, R.; Zieliński, P.; Piecha-Bisiorek, A.; Cichos, J.; Karbowiak, M.; Bator, G.; Cizman, A. Lead-Free Hybrid Ferroelectric Material Based on Formamidine: [NH2CHNH2]3Bi2I9. J. Mater. Chem. C 2019, 7 (10), 3003– 3014,  DOI: 10.1039/C8TC06458J
      24
      Lead-free hybrid ferroelectric material based on formamidine: [NH2CHNH2]3Bi2I9
      Szklarz, Przemyslaw; Gagor, Anna; Jakubas, Ryszard; Zielinski, Piotr; Piecha-Bisiorek, Anna; Cichos, Jakub; Karbowiak, Miroslaw; Bator, Grazyna; Cizman, Agnieszka
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2019), 7 (10), 3003-3014CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      The extraordinary thermal stability of [NH2CHNH2]3Bi2I9 (FA3Bi2I9) crystals, up to around 600 K, has been enhanced by using the evapg. method. DSC measurements have revealed reversible structural phase transitions: at 203 K (Phase I → Phase II), 173 K (II → III), 134.7 K (III → IV), 131.4 K (IV → V), and 120 K (V → VI). The crystal structures of FA3Bi2I9 adopt the polar space groups P63mc at 220 K (Phase I) and Cmc21 at 190 K (Phase II). The pyroelec. current (Ipyr) measured in the temp. range covering all the phases of FA3Bi2I9 confirmed their polar nature. The reversibility of the spontaneous polarization in each phase has been confirmed by the obsd. hysteresis loops. All the phase transitions are dielec. active. The dielec. response (ε*(ω,T) close to 134.7 and 131.4 K) is characteristic of ferroelecs. with a crit. slowing-down process. Optical bandgaps estd. from the UV-vis measurements and calcd. using the DFT method are equal to 1.85 and 1.89 eV, resp. On the basis of the structural, dielec., and spectroscopic results, the mol. mechanisms of the phase transitions have been proposed.
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    25. 25
      Jóźków, J.; Jakubas, R.; Bator, G.; Pietraszko, A. Ferroelectric Properties of (C5H5NH)5Bi2Br11. J. Chem. Phys. 2001, 114 (16), 7239– 7246,  DOI: 10.1063/1.1349897
      25
      Ferroelectric properties of (C5H5NH)5Bi2Br11
      Jozkow, J.; Jakubas, R.; Bator, G.; Pietraszko, A.
      Journal of Chemical Physics (2001), 114 (16), 7239-7246CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      A new pyridinium compd., (C5H5NH)5Bi2Br11, has been synthesized. The x-ray diffraction studies indicate that its structure is built up of four independent pyridinium cations and isolated Bi2Br115- groups. At room temp. it crystallizes in the monoclinic space group P21/n. Two phase transitions of second- and first-order type are detected by the differential scanning calorimetry measurements at 118 and 405/403 K (on heating-cooling), resp. The corresponding anomalies in the linear thermal expansion at 118 and 405 K are obsd. along three crystallog. directions. The dielec. investigations reveal dielec. absorption and dispersion in the radio-frequency region. The exptl. results were analyzed on the basis of dielec. formula which represents the sum of two independent relaxators. The pyroelec. measurements reveal that (C5H5NH)5Bi2Br11 becomes ferroelec. below 118 K and is characterized by the appearance of spontaneous polarization of the order of 3·10-3 C/m2 along the b axis.
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    26. 26
      Jakubas, R.; Piecha, A.; Pietraszko, A.; Bator, G. Structure and Ferroelectric Properties of (C3N2H5)5Bi2Cl11. Phys. Rev. B - Condens. Matter Mater. Phys. 2005, 72 (10), 1– 8,  DOI: 10.1103/PhysRevB.72.104107
      There is no corresponding record for this reference.
    27. 27
      Zhang, H. Y.; Wei, Z.; Li, P. F.; Tang, Y. Y.; Liao, W. Q.; Ye, H. Y.; Cai, H.; Xiong, R. G. The Narrowest Band Gap Ever Observed in Molecular Ferroelectrics: Hexane-1,6-Diammonium Pentaiodobismuth(III). Angew. Chem., Int. Ed. 2018, 57 (2), 526– 530,  DOI: 10.1002/anie.201709588
      27
      The Narrowest Band Gap Ever Observed in Molecular Ferroelectrics: Hexane-1,6-diammonium Pentaiodobismuth(III)
      Zhang, Han-Yue; Wei, Zhenhong; Li, Peng-Fei; Tang, Yuan-Yuan; Liao, Wei-Qiang; Ye, Heng-Yun; Cai, Hu; Xiong, Ren-Gen
      Angewandte Chemie, International Edition (2018), 57 (2), 526-530CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Narrow band gaps and excellent ferroelectricity are intrinsically paradoxical in ferroelecs. as the leakage current caused by an increase in the no. of thermally excited carriers will lead to a deterioration of ferroelectricity. A new mol. ferroelec., hexane-1,6-diammonium pentaiodobismuth (HDA-BiI5), was now developed through band gap engineering of org.-inorg. hybrid materials. It features an intrinsic band gap of 1.89 eV, and thus represents the 1st mol. ferroelec. with a band gap of <2.0 eV. Simultaneously, low-temp. soln. processing was successfully applied to fabricate high-quality ferroelec. thin films based on HDA-BiI5, for which high-precision controllable domain flips were realized. Owing to its narrow band gap and excellent ferroelectricity, HDA-BiI5 can be considered as a milestone in the exploitation of mol. ferroelecs., with promising applications in high-d. data storage and photovoltaic conversion.
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    28. 28
      Shi, C.; Han, X.-B.; Zhang, W. Structural Phase Transition-Associated Dielectric Transition and Ferroelectricity in Coordination Compounds. Coord. Chem. Rev. 2019, 378, 561– 576,  DOI: 10.1016/j.ccr.2017.09.020
      28
      Structural phase transition-associated dielectric transition and ferroelectricity in coordination compounds
      Shi, Chao; Han, Xiang-Bin; Zhang, Wen
      Coordination Chemistry Reviews (2019), 378 (), 561-576CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. Structural phase transition in solid-state materials is an underlying factor for emergence and evolution of a no. of important phys./chem. properties. In this review, we summarize recent achievements on two types of structural phase transition-assocd. properties, i.e., dielec. transition and ferroelectricity, in coordination compds. The basic concepts and fundamentals of structural phase transition and the two properties are briefly introduced. This review aims to reveal the role of the structural phase transitions on bulk properties and afford a perspective on the connections among multiple topics of coordination chem. from the structural phase transition viewpoint. It would be appealing to researchers in multidisciplinary fields such as coordination chem., crystal engineering, supramol. chem., condensed matter physics, responsive materials and mol. machines.
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    29. 29
      Zhang, W.; Xiong, R. G. Ferroelectric Metal-Organic Frameworks. Chem. Rev. 2012, 112 (2), 1163– 1195,  DOI: 10.1021/cr200174w
      29
      Ferroelectric Metal-Organic Frameworks
      Zhang, Wen; Xiong, Ren-Gen
      Chemical Reviews (Washington, DC, United States) (2012), 112 (2), 1163-1195CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1Wks7bL&md5=4b6508e05976c27d409579160aa4b14e
    30. 30
      Shi, P. P.; Tang, Y. Y.; Li, P. F.; Liao, W. Q.; Wang, Z. X.; Ye, Q.; Xiong, R. G. Symmetry Breaking in Molecular Ferroelectrics. Chem. Soc. Rev. 2016, 45 (14), 3811– 3827,  DOI: 10.1039/C5CS00308C
      30
      Symmetry breaking in molecular ferroelectrics
      Shi, Ping-Ping; Tang, Yuan-Yuan; Li, Peng-Fei; Liao, Wei-Qiang; Wang, Zhong-Xia; Ye, Qiong; Xiong, Ren-Gen
      Chemical Society Reviews (2016), 45 (14), 3811-3827CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Ferroelecs. are inseparable from symmetry breaking. Accompanying the paraelec.-to-ferroelec. phase transition, the paraelec. phase adopting one of the 32 crystallog. point groups is broken into subgroups belonging to one of the 10 ferroelec. point groups, i.e. C1, C2, C1h, C2v, C4, C4v, C3, C3v, C6 and C6v. The symmetry breaking is captured by the order parameter known as spontaneous polarization, whose switching under an external elec. field results in a typical ferroelec. hysteresis loop. In addn., the responses of spontaneous polarization to other external excitations are related to a no. of phys. effects such as second-harmonic generation, piezoelectricity, pyroelectricity and dielec. properties. Based on these, this review summarizes recent developments in mol. ferroelecs. since 2011 and focuses on the relationship between symmetry breaking and ferroelectricity, offering ideas for exploring high-performance mol. ferroelecs.
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    31. 31
      Huang, C.; Luo, X.; Liao, W.; Tang, Y.; Xiong, R. An Above-Room-Temperature Molecular Ferroelectric: [Cyclopentylammonium]2CdBr4. Inorg. Chem. 2020, 59, 829,  DOI: 10.1021/acs.inorgchem.9b03098
      31
      An above-room-temperature molecular ferroelectric: [Cyclopentylammonium]2CdBr4
      Huang, Chao-Ran; Luo, Xuzhong; Liao, Wei-Qiang; Tang, Yuan-Yuan; Xiong, Ren-Gen
      Inorganic Chemistry (2020), 59 (1), 829-836CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Mol. ferroelecs. as alternatives to the conventional inorg. ferroelecs. have been greatly developed in past decades; many of these have been discovered and designed through various chem. means due to their structural adjustability. However, it is still a huge challenge to obtain high (above room temp.) Curie temp. (Tc) mol. ferroelecs. to meet the application requirements. Here, we present a new org.-inorg. hybrid mol. ferroelec., [cyclopentylammonium]2CdBr4 (I), showing a moderate above-room-temp. Tc of 340.3 K. The mechanism of the ferroelec. phase transition from Pnam to Pna21 in I is ascribed to the order-disorder transition of both the org. cations and inorg. anions, affording a spontaneous polarization of 0.57μC/cm2 for the ferroelec. phase. Using piezoresponse force microscopy (PFM), we clearly obsd. the antiparallel 180° stripe domains and realized the polarization switching, unambiguously establishing the existence of room-temp. ferroelectricity in the thin film. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications. A new mol. ferroelec., [cyclopentylammonium]2CdBr4, shows an above-room-temp. Curie temp. of 340.3 K with the symmetry breaking from Pnam to Pna21.
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    32. 32
      Lu, J.; Kochi, J. K. Charge-Modulated Associates of Anionic Donors with Cationic π-Acceptors: Crystal Structures of Ternary Synthons Leading to Molecular Wires. Cryst. Growth Des. 2009, 9, 291– 296,  DOI: 10.1021/cg800465e
      32
      Charge-Modulated Associates of Anionic Donors with Cationic π-Acceptors: Crystal Structures of Ternary Synthons Leading to Molecular Wires
      Lu, Jianjiang; Kochi, Jay K.
      Crystal Growth & Design (2009), 9 (1), 291-296CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Tetramethylpyrazine is effectively transformed via controlled N-protonation or N-methylation to afford a series of mono- and dicationic π-acceptors of particular use in the study of charge modulation during the self-assembly of various anionic donors and π-acid acceptors into ternary synthons and infinite linear chains (mol. wires). Thus, when the charges of the anionic donor (D) and the cationic acceptor (A) are unequal (either as 1:2 or as 2:1), the corresponding crystal structures of the donor/acceptor assocs. all contain structure motifs of discrete synthons consisting of (A···D···A) or (D···A···D) triads. On the other hand, when the anionic donor and cationic acceptor are of equal charge (either as 1:1 or as 2:2), the corresponding crystal structures all contain infinite chain arrangements: (···D···A···D···A···D···), which are the same as those we previously found in the cocrystn. of various anionic donors with neutral π-acids. Fully appreciated anion/π interactions are found in all of these solids owing to the absence of arom. protons in the π-acids, as well as the presence of strong electrostatic anion/cation interactions. It is noteworthy in such assocs. that halide anions (Cl-, Br-, and I-) show different patterns of donor/acceptor interactions. For example, in the case of the diprotonated tetramethylpyrazinium dication, the chloride donor is π-bonded over the edge of the arom. ring, whereas bromide and iodide donors are precisely located over the arom. ring centrosym. We hope these structural studies will provide addnl. stimulus for the design of new anion receptors based on the use of charged arom. acceptors.
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    33. 33
      Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W. Synthesis, Crystal Structure, Physico-Chemical Characterization and Dielectric Properties of a New Hybrid Material, 1-Ethylpiperazine-1,4-Diium Tetrachlorocadmate. J. Mol. Struct. 2015, 1102, 50– 56,  DOI: 10.1016/j.molstruc.2015.08.044
      33
      Synthesis, crystal structure, physico-chemical characterization and dielectric properties of a new hybrid material, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate
      Dhieb, A. C.; Valkonen, A.; Rzaigui, M.; Smirani, W.
      Journal of Molecular Structure (2015), 1102 (), 50-56CODEN: JMOSB4; ISSN:0022-2860. (Elsevier B.V.)
      A new org.-inorg. hybrid metal complex, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate was synthesized and the structure is detd. by single crystal x-ray diffraction analyses. The title compd. crystallizes in the orthorhombic system with space group Pbca. The unit cell parameters are a 11.5129(2) Å, b 9.7801(2) Å, c 23.8599(4) Å with Z = 8 and V = 2686.56(8) Å3. The examn. of the structure shows that Cd(II) is coordinated by 4 Cl atoms and adopts a tetrahedral geometry. Three-dimensional frameworks of the title compd. are produced by N-H···Cl and C-H···Cl H bonding. IR, Raman and UV-Visible spectroscopies were also used to characterize this complex. Also, the fluorescent properties of the compd. were studied in the solid state at room temp. Solid state 13C MAS NMR spectroscopy results are in agreement with the x-ray structure. DSC revealed a structural phase transition of the order-disorder type around 373 K, and dielec. measurements were performed to discuss the mechanism of this phase transition. The evolution of dielec. const. as a function of temp. of the sample was studied to det. some related parameters.
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    34. 34
      Wang, X. L.; Zhou, L.; Ye, Q.; Geng, F. J.; Ye, H. Y.; Fu, D. W.; Zhang, Y. A Spiro-Type Ammonium Based Switchable Dielectric Material with Two Sequential Reversible Phase Transitions above Room Temperature. RSC Adv. 2016, 6 (78), 74117– 74123,  DOI: 10.1039/C6RA14157A
      34
      A spiro-type ammonium based switchable dielectric material with two sequential reversible phase transitions above room temperature
      Wang, Xiao-Li; Zhou, Lin; Ye, Qiong; Geng, Fu-Juan; Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi
      RSC Advances (2016), 6 (78), 74117-74123CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      An org.-inorg. hybrid compd. 5-azonia-spiro[4,4]nonane tetrabromocadmium (1, [ASN]2[CdBr4], ASN = (CH2)4N(CH2)4), has been discovered as a new phase transition material. Differential scanning calorimetry (DSC) and dielec. measurements reveal that 1 undergoes dielec. anomalies which could be tuned in three evident dielec. states and switched by two sequential reversible phase transitions around 336 and 357 K, resp. Detailed variable-temp. single-crystal structural analyses indicate that the distinct twisting motions of the flexible [ASN]+ ammonium cationic moieties and the relative reorientations of both the ions contribute to the structure phase transitions of 1 triggered by temp. Particularly, 1 displays a switchable SHG response in the vicinity of 357 K, where the temp.-dependent dielec. permittivity of 1 changes abruptly from 8 to 15, with a large thermal hysteresis of 19 K. Therefore, such a distinctive dielec. performance discloses that 1 might be an interesting high-temp. switchable dielec. and nonlinear optical material. All these results open a new venue to design novel phase transition materials through selecting the flexible spiro-type ammonium salts.
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    35. 35
      Puget, R.; Jannin, M.; De Brauer, C.; Perret, R. Structures of Trimethyloxosulfonium Salts. V. The Catena-Tri-μ-Chloro- Cadmate and the Catena-Tri-μ-Bromo-Cadmate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1991, 47 (9), 1803– 1805,  DOI: 10.1107/S0108270190013701
      There is no corresponding record for this reference.
    36. 36
      Xu, W. J.; He, C. T.; Ji, C. M.; Chen, S. L.; Huang, R. K.; Lin, R. B.; Xue, W.; Luo, J. H.; Zhang, W. X.; Chen, X. M. Molecular Dynamics of Flexible Polar Cations in a Variable Confined Space: Toward Exceptional Two-Step Nonlinear Optical Switches. Adv. Mater. 2016, 28, 5886– 5890,  DOI: 10.1002/adma.201600895
      36
      Molecular Dynamics of Flexible Polar Cations in a Variable Confined Space: Toward Exceptional Two-Step Nonlinear Optical Switches
      Xu, Wei-Jian; He, Chun-Ting; Ji, Cheng-Min; Chen, Shao-Li; Huang, Rui-Kang; Lin, Rui-Biao; Xue, Wei; Luo, Jun-Hua; Zhang, Wei-Xiong; Chen, Xiao-Ming
      Advanced Materials (Weinheim, Germany) (2016), 28 (28), 5886-5890CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A hexagonal perovskite compd., pyrrolidinium cadmium trichloride [C4H10N][CdCl3], composed of rigid inorg. chains embedded with flexible org. cations, has been synthesized and studied by variable-temp. X-ray anal., dielec. and SHG measurements, as well as classical mol. dynamics simulations. The changeable mol. dynamics of the flexible polar cations in the variable confined space between inorg. chains brings about thermal-induced two-step phase transitions, including a typical ferroelec. transition that loses inversion centers by cooling from room temp. to 240 K and an exceptional one that regains inversion centers by further cooling to 198 K. Such reversible transitions between one noncentrosym. phase and two centrosym. phases affords a new type of two-step NLO switches, which exhibits genuine "off-one-off" SHG conversion between one NLO-active state and two NLO-inactive states with a remarkable SHG contrast of -8.0.
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    37. 37
      Ye, H. Y.; Zhang, Y.; Fu, D. W.; Xiong, R. G. An Above-Room-Temperature Ferroelectric Organo-Metal Halide Perovskite: (3-Pyrrolinium)(CdCl3). Angew. Chem., Int. Ed. 2014, 53, 11242– 11247,  DOI: 10.1002/anie.201406810
      37
      An above-room-temperature ferroelectric organo-metal halide perovskite: (3-pyrrolinium)(CdCl3)
      Ye, Heng-Yun; Zhang, Yi; Fu, Da-Wei; Xiong, Ren-Gen
      Angewandte Chemie, International Edition (2014), 53 (42), 11242-11247CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Hybrid organo-metal halide perovskite materials, such as CH3NH3PbI3, have been shown to be some of the most competitive candidates for absorber materials in photovoltaic (PV) applications. However, their potential has not been completely developed, because a photovoltaic effect with an anomalously large voltage can be achieved only in a ferroelec. phase, while these materials are probably ferroelec. only at temps. below 180 K. A new hexagonal stacking perovskite-type complex (3-pyrrolinium)(CdCl3) exhibits above-room-temp. ferroelectricity with a Curie temp. Tc=316 K and a spontaneous polarization Ps=5.1 μC cm-2. The material also exhibits antiparallel 180° domains which are related to the anomalous photovoltaic effect. The open-circuit photovoltage for a 1 mm-thick bulky crystal reaches 32 V. This finding could provide a new approach to develop solar cells based on organo-metal halide perovskites in photovoltaic research.
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    38. 38
      Li, P. F.; Liao, W. Q.; Tang, Y. Y.; Ye, H. Y.; Zhang, Y.; Xiong, R. G. Unprecedented Ferroelectric-Antiferroelectric-Paraelectric Phase Transitions Discovered in an Organic-Inorganic Hybrid Perovskite. J. Am. Chem. Soc. 2017, 139, 8752– 8757,  DOI: 10.1021/jacs.7b04693
      38
      Unprecedented ferroelectric-antiferroelectric-paraelectric phase transitions discovered in an organic-inorganic hybrid perovskite
      Li, Peng-Fei; Liao, Wei-Qiang; Tang, Yuan-Yuan; Ye, Heng-Yun; Zhang, Yi; Xiong, Ren-Gen
      Journal of the American Chemical Society (2017), 139 (25), 8752-8757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      As a promising candidate for energy storage capacitors, antiferroelec. (AFE) materials have attracted great concern due to their congenital advantages of large energy storage ability from double polarization vs. elec. field (P-E) hysteresis characteristics in contrast to ferroelecs. and linear dielecs. However, antiferroelectricity has only been discovered in inorg. oxides and some hydrogen-bonded mol. systems. In view of the structural diversity and unique phys. properties of org.-inorg. hybrid system, it remains a great opportunity to introduce antiferroelectricity into org.-inorg. hybrid perovskites. Here, the authors report that polarizable antiparallel dipole arrays can be realized in an org.-inorg. hybrid perovskite, (3-pyrrolinium)CdBr3, which not only exhibits an excellent ferroelec. 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 their knowledge, it is the first time that such successive ferroelec.-antiferroelec.-paraelec. phase transitions have been discovered in org.-inorg. perovskites. Besides, a giant dielec. const. 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 obsd. during the phase transition. Apparently, the combined striking AFE characteristic and giant dielec. const. make (3-pyrrolinium)CdBr3 a promising candidate for next generation high-energy-storage capacitors.
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    39. 39
      Zhang, Y.; Ye, H. Y.; Zhang, W.; Xiong, R. G. Room-Temperature ABX3-Typed Molecular Ferroelectric: [C5H9-NH3][CdCl3]. Inorg. Chem. Front. 2014, 1, 118– 123,  DOI: 10.1039/c3qi00058c
      39
      Room-temperature ABX3-typed molecular ferroelectric: [C5H9-NH3][CdCl3]
      Zhang, Yi; Ye, Heng-Yun; Zhang, Wen; Xiong, Ren-Gen
      Inorganic Chemistry Frontiers (2014), 1 (1), 118-123CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      Reaction of CdCl2 with cyclopentylamine in the presence of aq. HCl affords an ABX3-typed perovskite structure compd. [C5H9-NH3][CdCl3] (1). Above 300 K, it is in a paraelec. phase with a centrosym. space group Cmcm, while below 300 K it has a noncentrosym. space group Cc, corresponding to a ferroelec. phase. The temp.-dependent dielec. const. shows a peak at about 300 K with a 12-fold enhancement which is confirmed by differential scanning calorimetry. The normalized pyroelec. and second-harmonic generation effect as functions of temp. are almost overlapped, probably indicating that the trends with temp. basically satisfy the Landau phenomenol. theory, revealing a symmetry-breaking occurrence. The ferroelectricity, a spontaneous satn. polarization approx. reaching 1.7 μC cm-2, is further confirmed by piezoresponse force microscopy.
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    40. 40
      Gesi, K. Ferroelectricity in (NCH3)4CdBr3. J. Phys. Soc. Jpn. 1990, 59, 432– 434,  DOI: 10.1143/JPSJ.59.432
      40
      Ferroelectricity in tetramethylammonium tribromocadmate
      Gesi, Kazuo
      Journal of the Physical Society of Japan (1990), 59 (2), 432-4CODEN: JUPSAU; ISSN:0031-9015.
      Dielec. properties of N(CH3)4CdBr3 single crystal have been studied. The dielec. const. along the c-direction shows a slight γ-type max. at 156 K while that along the a-direction shows a discontinuity. The compd. exhibits ferroelec. activity along the c-direction below the Curie temp. of 156 K. The spontaneous polarization obtained by 50 Hz hysteresis loop measurement is about 1.2 × 10-3 C/m2 at 125 K.
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    41. 41
      You, Y. M.; Liao, W. Q.; Zhao, D.; Ye, H. Y.; Zhang, Y.; Zhou, Q.; Niu, X.; Wang, J.; Li, P. F.; Fu, D. W. An Organic-Inorganic Perovskite Ferroelectric with Large Piezoelectric Response. Science 2017, 357, 306– 309,  DOI: 10.1126/science.aai8535
      41
      An organic-inorganic perovskite ferroelectric with large piezoelectric response
      You, Yu-Meng; Liao, Wei-Qiang; Zhao, Dewei; Ye, Heng-Yun; Zhang, Yi; Zhou, Qionghua; Niu, Xianghong; Wang, Jinlan; Li, Peng-Fei; Fu, Da-Wei; Wang, Zheming; Gao, Song; Yang, Kunlun; Liu, Jun-Ming; Li, Jiangyu; Yan, Yanfa; Xiong, Ren-Gen
      Science (Washington, DC, United States) (2017), 357 (6348), 306-309CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Mol. piezoelecs. are highly desirable for their easy and environment-friendly processing, light wt., low processing temp., and mech. flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelec. effect, mol. piezoelecs. with a piezoelec. coeff. d33 comparable with piezoceramics such as barium titanate (BTO; ∼190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an org.-inorg. perovskite ferroelec. crystal processed from aq. soln., has a large d33 of 185 picocoulombs per newton and a high phase-transition temp. of 406 K (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromech., and biomech. applications.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFygs73L&md5=43b8104067df218ad8d7354fc465383a
    42. 42
      Liao, W. Q.; Tang, Y. Y.; Li, P. F.; You, Y. M.; Xiong, R. G. Competitive Halogen Bond in the Molecular Ferroelectric with Large Piezoelectric Response. J. Am. Chem. Soc. 2018, 140, 3975– 3980,  DOI: 10.1021/jacs.7b12524
      42
      Competitive halogen bond in the molecular ferroelectric with large piezoelectric response
      Liao, Wei-Qiang; Tang, Yuan-Yuan; Li, Peng-Fei; You, Yu-Meng; Xiong, Ren-Gen
      Journal of the American Chemical Society (2018), 140 (11), 3975-3980CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Mol. piezoelecs. are attracting tremendous interest because of their easy processing, light wt., low acoustical impedance and mech. flexibility. However, reports of mol. piezoelecs. with a piezoelec. coeff. d33 comparable to piezoceramics such as barium titanate (BTO, 90-190 pC/N) have been scarce. Here, we present a uniaxial mol. ferroelec., trimethylchloromethylammonium tribromocadmium(II) (TMCM-CdBr3), in which the halogen bonding might be a possible crit. point for the stabilization of 1-dimensional (1D) {CdBr3}- chain and further reservation of its ferroelectricity in such org.-inorg. hybrid cryst. systems. It has a large d33 of 139 pC/N, 1 order of magnitude higher than those of most classically uniaxial ferroelecs. such as LiNbO3 (6-16 pC/N) and Rochelle salt (∼7 pC/N), and comparable with those of multiaxial ferroelecs. 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 mol. piezoelecs. and contribute to further developments.
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    43. 43
      Liao, W. Q.; Ye, H. Y.; Fu, D. W.; Li, P. F.; Chen, L. Z.; Zhang, Y. Temperature-Triggered Reversible Dielectric and Nonlinear Optical Switch Based on the One-Dimensional Organic - Inorganic Hybrid Phase Transition Compound [C6H11NH3]2CdCl4. Inorg. Chem. 2014, 53, 11146– 11151,  DOI: 10.1021/ic501749c
      43
      Temperature-Triggered Reversible Dielectric and Nonlinear Optical Switch Based on the One-Dimensional Organic-Inorganic Hybrid Phase Transition Compound [C6H11NH3]2CdCl4
      Liao, Wei-Qiang; Ye, Heng-Yun; Fu, Da-Wei; Li, Peng-Fei; Chen, Li-Zhuang; Zhang, Yi
      Inorganic Chemistry (2014), 53 (20), 11146-11151CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      The one-dimensional org.-inorg. hybrid compd. 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 sepd. 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 DSC measurements, variable-temp. structural analyses, and dielec. and second harmonic generation (SHG) measurements. A precise structural anal. 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 dielec. const. and SHG intensity of 1 show a striking change between low and high states at ∼367 K, which reveals that 1 might be considered as a potential dielec. and nonlinear optical (NLO) switch with high-temp. response characterization, excellent reversibility, and obvious change of states.
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    44. 44
      Jin, J.; Jin, L.; Su, E.-B. Temperature-Induced Isosymmetric Reversible Structural Phase Transition in Catena-[Pyridinium Tris(μ2-Bromo)-Cadmium(II)]. CrystEngComm 2014, 16 (39), 9284– 9290,  DOI: 10.1039/C4CE00799A
      44
      Temperature-induced isosymmetric reversible structural phase transition in catena-[pyridinium tris(μ2-bromo)-cadmium(II)]
      Jin, Jing; Jin, Lei; Su, En-Ben
      CrystEngComm (2014), 16 (39), 9284-9290CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      A new centrosym. one-dimensional ABX3-type org.-inorg. hybrid polymer compd. ([C5H6N+][CdBr3]-) was synthesized and sepd. into block colorless crystals. DSC and dielec. measurements indicate that this compd. undergoes a reversible phase transition at 230 K with a hysteresis width of 17.9 K. The crystal structures, detd. at 293(2) K and 140(2) K, show that the phase transition is a type of isosym. change from the space group of Pbca (no. 61) in the low-temp. phase (LTP) to the space group of Cmcm (no. 63) in the room-temp. phase (RTP). The main difference between the LTP and the RTP structures is the distribution of the nitrogen atoms in the pyridinium cations. In the LTP, pyridinium cations are well ordered with localized N and C atom positions. Meanwhile, for the RTP, the N atoms are indistinguishable from the C3 atoms with the occupancy of N/C3 atoms being 0.5, sep. Noncovalent static attracting forces (Coulombic and van der Waals forces) and nonclassical C-H···Br and N-H···Br hydrogen-bond interactions stabilize the crystal structure.
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    45. 45
      Jian, F. F.; Zhao, P. S.; Wang, Q. X.; Li, Y. One-Dimensional Cd Metal String Complex: Synthesis, Structural and Thermal Properties of [(HPy)3(Cd3Cl9)]∞. Inorg. Chim. Acta 2006, 359 (5), 1473– 1477,  DOI: 10.1016/j.ica.2005.10.054
      45
      One-dimensional Cd metal string complex: Synthesis, structural and thermal properties of [(HPy)3(Cd3Cl9)]∞
      Jian, Fang Fang; Zhao, Pu Su; Wang, Qing Xiang; Li, Ying
      Inorganica Chimica Acta (2006), 359 (5), 1473-1477CODEN: ICHAA3; ISSN:0020-1693. (Elsevier B.V.)
      The cadmium metal string complex of [(HPy)3(Cd3Cl9)]∞ (Py = pyridine) was prepd. Its structural and thermal properties were also studied. Its existing form in the gas phase was elucidated by d. functional calcns. The crystal structure consists of protonation pyridine cations and infinite 1-dimensional chains of [Cd3Cl9]3- anions. Each Cd atom is octahedrally surround by bridged chlorine atoms, giving rise to polymeric chains along the a-axis. The pyridinium cations lie in the middle of the chains to balance the charge. The DFT study indicates that the HOMO orbital of optimized structure is mainly localized on the middle six chloride ions and the LUMO is delocalized. Differential TGA shows there is no presence of any structural phase transitions.
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    46. 46
      Wang, Z.; Lv, X. H.; Liu, Y. L.; Lu, Y.; Chen, H. P.; Ge, J. Z. Prominent Dielectric Transitions in Layered Organic-Inorganic Hybrids: (Isoamyl-Ammonium)2CdX4 (X = Cl and Br). Inorg. Chem. Front. 2017, 4 (8), 1330– 1336,  DOI: 10.1039/C7QI00270J
      46
      Prominent dielectric transitions in layered organic-inorganic hybrids: (isoamyl-ammonium)2CdX4 (X = Cl and Br)
      Wang, Zhongxia; Lv, Xing-Hui; Liu, Yu-Ling; Lu, Yang; Chen, Hai-Peng; Ge, Jia-Zhen
      Inorganic Chemistry Frontiers (2017), 4 (8), 1330-1336CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      Layered org.-inorg. hybrids represent a class of technol. important materials due to their promising phys. properties. In this report, two new layered org.-inorg. hybrid compds. (IAA)2CdX4 (IAA = isoamyl-ammonium cation, X = Cl, 1 and Br, 2) have been successfully synthesized and characterized. 1 undergoes a reversible solid-state phase transition at 230 K and 2 demonstrates three successive phase transitions and both of them exhibit prominent temp.-dependent dielec. behaviors. Detailed characterization was performed to investigate their phase transitions, including differential scanning calorimetry (DSC) measurements, variable-temp. structural analyses, variable-temp. powder X-ray diffraction (VT-PXRD) and dielec. measurements. The obvious difference in the phase transitions between 1 and 2 is originated from a bridged halogen effect, which makes different spaces between the inorg. framework layers where the org. IAA cation resides, resulting in different dynamic motions of the org. cations. These findings might be helpful to search for new dielec. materials based on layered org.-inorg. hybrid perovskites through exchange of the halogen atom.
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    47. 47
      Han, S.; Liu, X.; Zhang, J.; Ji, C.; Wu, Z.; Tao, K.; Wang, Y.; Sun, Z.; Luo, J. Dielectric Phase Transition Triggered by the Order-Disorder Transformation of Cyclopropylamine in a Layered Organic-Inorganic Halide Perovskite. J. Mater. Chem. C 2018, 6, 10327– 10331,  DOI: 10.1039/C8TC03517B
      47
      Dielectric phase transition triggered by the order-disorder transformation of cyclopropylamine in a layered organic-inorganic halide perovskite
      Han, Shiguo; Liu, Xitao; Zhang, Jing; Ji, Chengmin; Wu, Zhenyue; Tao, Kewen; Wang, Yuyin; Sun, Zhihua; Luo, Junhua
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (38), 10327-10331CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Cyclic org. amines are emerging as excellent building blocks to assemble org.-inorg. hybrid phase transition materials due to their flexible cyclic structure. Herein, we used a three-membered ring org. amine, cyclopropylamine, assembling a layered org.-inorg. hybrid dielec. phase transition compd. ([C3H5NH3]2[CdCl4], CPA) that displays a remarkable switchable dielec. response induced by an order-disorder transformation of the org. moiety. More specifically, the dielec. const. of CPA can be tuned between high- and low-dielec. states at ∼273 K, which demonstrates its potential application in a switchable dielec. field. In addn., theor. anal. of electronic band structures suggests that CPA exhibits a direct-band-gap with the value of 5.20 eV. This solid-state structural phase transition triggered by ordering of a three-membered ring org. amine is reported for the first time, and it highlights a new potential strategy to design switchable dielec. materials.
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    48. 48
      Liao, W. Q.; Mei, G. Q.; Ye, H. Y.; Mei, Y. X.; Zhang, Y. Structural Phase Transitions of a Layered Organic-Inorganic Hybrid Compound: Tetra(Cyclopentylammonium) Decachlorotricadmate(II), [C5H9NH3]4Cd3Cl10. Inorg. Chem. 2014, 53, 8913– 8918,  DOI: 10.1021/ic500554z
      48
      Structural Phase Transitions of a Layered Organic-Inorganic Hybrid Compound: Tetra(cyclopentylammonium) Decachlorotricadmate(II), [C5H9NH3]4Cd3Cl10
      Liao, Wei-Qiang; Mei, Guang-Quan; Ye, Heng-Yun; Mei, Ying-Xuan; Zhang, Yi
      Inorganic Chemistry (2014), 53 (17), 8913-8918CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      A layered org.-inorg. hybrid compd., tetra(cyclopentylammonium) decachlorotricadmate(II) (1), in which the two-dimensional [Cd3Cl10]n4- networks built up from three face-sharing CdCl6 octahedra are sepd. by cyclopentylammonium cation bilayers, was 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 DSC measurements, variable-temp. structural analyses, and dielec. measurements. The crystal structures of 1 detd. at 93, 298, and 343 K are solved in P212121, Pbca, and Cmca, resp. Crystallog. data are given. A precise anal. 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]n4- network.
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    49. 49
      Chen, H. P.; Shi, P. P.; Wang, Z. X.; Gao, J. X.; Zhang, W. Y.; Chen, C.; Tang, Y. Y.; Fu, D. W. Tunable Dielectric Transitions in Layered Organic-Inorganic Hybrid Perovskite-Type Compounds: [NH3(CH2)2Cl]2CdCl4–4xBr4x] (x = 0, 1/4, 1). Dalton Trans. 2018, 47 (20), 7005– 7012,  DOI: 10.1039/C8DT00353J
      49
      Tunable dielectric transitions in layered organic-inorganic hybrid perovskite-type compounds: [NH3(CH2)2Cl]2[CdCl4-4xBr4x] (x = 0, 1/4, 1)
      Chen, Hai-Peng; Shi, Ping-Ping; Wang, Zhong-Xia; Gao, Ji-Xing; Zhang, Wan-Ying; Chen, Cheng; Tang, Yuan-Yuan; Fu, Da-Wei
      Dalton Transactions (2018), 47 (20), 7005-7012CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      Mol. bistable dielec. switches represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light wts., and mech. flexibility. However, most of these switches can only work at a very low temp., extremely limiting their potential applications. Herein, three layered org.-inorg. hybrid perovskite-type compds. of the general formula A2BX4, [NH3(CH2)2Cl]2[CdCl3Br] (1), [NH3(CH2)2Cl]2[CdCl4] (2) and [NH3(CH2)2Cl]2[CdBr4] (3), which display sensitive dielec. switching reversibility and remarkable switching anti-fatigue, have been successfully designed. Differential scanning calorimetry and dielec. measurements for 1 confirm its reversible phase transition at around 166 K. Through anion modulation, the phase transition temps. of 2 and 3 can be greatly improved up to 237 K and 254 K, resp. Structural anal. discloses that the phase transition temp.'s shifts may result from the differences among the inorg. frameworks. Moreover, due to the significant order-disorder transitions of ammonium cations, the permittivities of 1, 2 and 3 change abruptly at around the phase transition points, making them excellent stimuli-responsive elec. switches. Such an anion-modulated method will open up new possibilities of highly efficiently tuning the phase transition temp. of mol. bistable dielec. switches.
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    50. 50
      Wang, Z.; Lu, Y.; Chen, H. P.; Ge, J. Z. Controllable Structures Designed with Multiple-Dielectric Responses in Hybrid Perovskite-Type Molecular Crystals. Inorg. Chem. 2017, 56 (12), 7058– 7064,  DOI: 10.1021/acs.inorgchem.7b00662
      50
      Controllable Structures Designed with Multiple-Dielectric Responses in Hybrid Perovskite-Type Molecular Crystals
      Wang, Zhongxia; Lu, Yang; Chen, Hai-Peng; Ge, Jia-Zhen
      Inorganic Chemistry (2017), 56 (12), 7058-7064CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      In this report, two new hybrid org.-inorg. perovskite-type compds., (IBA)CdBr3 (1; IBA = isobutylammonium cation, i-C4H9-NH3) and (IBA)2CdBr4 (2), have been successfully synthesized by reasonable modulation of the ratio of the reactants. 1 With a one-dimensional (1D) chained structure presents sequential solid-state phase transitions, and 2 with a two-dimensional (2D) layered structure undergoes triple structural phase transitions. The phase transitions are attributable to the stepwise ordering process of the org. IBA cation of the title compds., which also exhibit temp.-dependent dielec. transitions and dielec. anisotropies. Among the different structural environments, the dynamic motions of org. cations show distinct differences, driving the variation of phys. properties.
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    51. 51
      Wang, Y.; Ji, C.; Liu, X.; Han, S.; Zhang, J.; Sun, Z.; Khan, A.; Luo, J. (1,4-Butyldiammonium)CdBr4: A Layered Organic-Inorganic Hybrid Perovskite with a Visible-Blind Ultraviolet Photoelectric Response. Inorg. Chem. Front. 2018, 5 (10), 2450– 2455,  DOI: 10.1039/C8QI00551F
      51
      ButyldiammoniumCdBr4: a layered organic-inorganic hybrid perovskite with a visible-blind ultraviolet photoelectric response
      Wang, Yuyin; Ji, Chengmin; Liu, Xitao; Han, Shiguo; Zhang, Jing; Sun, Zhihua; Khan, Asma; Luo, Junhua
      Inorganic Chemistry Frontiers (2018), 5 (10), 2450-2455CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      Inspired by the breakthrough of three-dimensional hybrid perovskite CH3NH3PbI3, two-dimensional (2D) layered org.-inorg. halide perovskites are emerging as another promising class of hybrid materials for optoelectronic devices, such as photodetectors fabricated on lead halide perovskites. However, the majority of such 2D materials exhibit photosensitivity to visible light, while few candidates have been reported to exhibit visible-blind UV photoelec. response. Here, we present a new hybrid material, (1,4-butyldiammonium)CdBr4 (1), in which the corner-sharing CdBr6 octahedra construct the 2D perovskite-type inorg. frameworks. The optical bandgap (Eg) of 1 is estd. to be ∼3.45 eV. Particularly, 1 shows spectral-selective photocond., i.e., it is sensitive to UV-light illumination below 360 nm but almost blind to the std. visible light (above 400 nm), disclosing the potential of 1 for visible-blind UV photodetection. Further theor. analyses of its electronic structure and energy gap disclose that the inorg. perovskite architecture dominates the optical bandgap. It is believed that this work provides a potential route for the design and fabrication of new 2D hybrid perovskite materials with a UV photoelec. response.
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    52. 52
      Graja, A. Production of the Second Harmonic of Light in Ammonium Pentaborate and Other Powdered Piezoelectric Crystals. Phys. Status Solidi B 1968, 27, K93– K97,  DOI: 10.1002/pssb.19680270237
      There is no corresponding record for this reference.
    53. 53
      Kurtz, S. K.; Perry, T. T. A Powder Technique for the Evaluation of Nonlinear Optical Materials. J. Appl. Phys. 1968, 39, 3798– 3813,  DOI: 10.1063/1.1656857
      53
      Powder technique for the evaluation of nonlinear optical materials
      Kurtz, S. K.; Perry, T. T.
      Journal of Applied Physics (1968), 39 (8), 3798-813CODEN: JAPIAU; ISSN:0021-8979.
      An exptl. technique by using powders is described which permits the rapid classification of materials according to (a) magnitude of nonlinear optical coeffs., relative to a cryst. quartz standard and (b) existence or absence of phase matching direction(s) for 2nd-harmonic generation. Results are presented for a large no. of inorg. and org. substances including single-crystal data on phase-matched 2nd-harmonic generation in HIO3, KNbO3, PbTiO3, LiClO4.3H2O, and CO(NH2)2. HIO3 has a nonlinear coeff. d14 ∼ 1.5 × d31 LiNbO3. Since it is readily grown from water soln. and does not exhibit optical damage effects, this material should be useful for nonlinear device applications.
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    54. 54
      Cole, K. S.; Cole, R. H. Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics. J. Chem. Phys. 1941, 9, 341– 351,  DOI: 10.1063/1.1750906
      54
      Dispersion and absorption in dielectrics. I. Alternating-current characteristics
      Cole, Kenneth S.; Cole, Robert H.
      Journal of Chemical Physics (1941), 9 (), 341-51CODEN: JCPSA6; ISSN:0021-9606.
      The dispersion and absorption of many liq. dielecs. are connected by an equation. Dispersion and absorption data are assembled for H2O, MeOH, EtOH, PrOH, BuOH, iso-AmOH, glycerol, 2 rosin oils, 3 chlorobiphenyls, ice, 1,2,4- Me3C6H3, 3,5,6-Cl3C6H3, MeC6Cl5, 1,2,3,4-Me4C6Cl2, Me5C6Cl, H2C(CH2)3CHOH, H2C(CH2)4C:O, abietic acid, plasticized polyvinyl chloride, glycol phthalate resin, phenol-formaldehyde resin, Vinsol, halowax, paraffin, ceresin, rubber with 20% and 32% S, Pyrex, mica and slate. 42 refs.
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    55. 55
      Dhanasekhar, C.; Das, A. K.; Das, A.; Venimadhav, A. Ferroelectricity in CaBaCo4O7 by Light Non Magnetic Zn Doping. J. Phys.: Condens. Matter 2020, 32 (38), 385802,  DOI: 10.1088/1361-648X/ab9567
      55
      Ferroelectricity in CaBaCo4O7 by light non magnetic Zn doping
      Dhanasekhar C; Das A K; Das A; Venimadhav A
      Journal of physics. Condensed matter : an Institute of Physics journal (2020), 32 (38), 385802 ISSN:.
      CaBaCo4O7 (CBCO) cobaltite shows a giant spin driven pyroelectric polarization below its ferrimagnetic transition temperature at 64 K. In the present study, we have investigated the structural, magnetic and electric polarization properties of light nonmagnetic Zn doped polycrystalline CaBaCo3.97Zn0.03O7 (CBCZO) cobaltite. Neutron powder diffraction studies on the CBCZO show that the Zn occupies the Co2 sites which lowers the strength of the magnetic interactions between the bitetrahedral cobalt c-axis chains. Further, we show that these chains act as magnetic clusters and causes the switching of the electric polarization. This study specifies that the ferrimagnetic-pyroelectric ground state of CBCO is very sensitive to the light non-magnetic doping and the results can be used to further understand the pyroelectric polarization switching properties of CBCO.
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    56. 56
      Jiang, C.; Zhong, N.; Luo, C.; Lin, H.; Zhang, Y.; Peng, H.; Duan, C. G. (Diisopropylammonium)2MnBr4: A Multifunctional Ferroelectric with Efficient Green-Emission and Excellent Gas Sensing Properties. Chem. Commun. 2017, 53 (44), 5954– 5957,  DOI: 10.1039/C7CC01107E
      56
      (Diisopropylammonium)2MnBr4: a multifunctional ferroelectric with efficient green-emission and excellent gas sensing properties
      Jiang, Chunli; Zhong, Ni; Luo, Chunhua; Lin, Hechun; Zhang, Yuanyuan; Peng, Hui; Duan, Chun-Gang
      Chemical Communications (Cambridge, United Kingdom) (2017), 53 (44), 5954-5957CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Combination of excellent optical properties and ferroelectricity of hybrid materials leads to high-performance optoelectronic devices. Here the authors present a new org.-inorg. hybrid compd. (diisopropylammonium)2MnBr4 (DIPA2MnBr4) which shows high temp. ferroelectricity accompanied by highly efficient green-light emission. DIPA2MnBr4 also exhibits sensitive and selective optical response to alc. vapors.
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    57. 57
      Aguirre-Zamalloa, G.; Madariaga, G.; Couzi, M.; Breczewski, T. X-ray Diffraction Study of the Ferroelectric Phase Transition of (CH3)4NCdBr3 (TMCB). Acta Crystallogr., Sect. B: Struct. Sci. 1993, 49 (4), 691– 698,  DOI: 10.1107/S010876819300182X
      There is no corresponding record for this reference.
    58. 58
      Asahi, T.; Hasebe, K.; Gesi, K. Structure of Tetramethylammonium Tribromocadmate in the Ferroelectric Phase. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1991, 47 (6), 1208– 1210,  DOI: 10.1107/S0108270190014135
      There is no corresponding record for this reference.
    59. 59
      Zhou, L.; Shi, P. P.; Liu, X. M.; Feng, J. C.; Ye, Q.; Yao, Y. F.; Fu, D. W.; Li, P. F.; You, Y. M.; Zhang, Y. An Above-Room-Temperature Phosphonium-Based Molecular Ferroelectric Perovskite, [(CH3)4P]CdCl3, with Sb3+-Doped Luminescence. NPG Asia Mater. 2019, 11 (1), 1– 15,  DOI: 10.1038/s41427-019-0115-0
      59
      A novel dual-adhesive and bioactive hydrogel activated by bioglass for wound healing
      Gao, Long; Zhou, Yanling; Peng, Jinliang; Xu, Chen; Xu, Qing; Xing, Min; Chang, Jiang
      NPG Asia Materials (2019), 11 (1), 66CODEN: NAMPCE; ISSN:1884-4057. (Nature Research)
      Dual adhesiveness to tissue and implant biomaterials and bioactivity to stimulate tissue regeneration are interesting properties for developing new generations of tissue-repairing hydrogels with potential new clin. applications. In this study, we developed a unique bioglass (BG)/oxidized sodium alginate (OSA) composite hydrogel with adipic acid dihydrazide (ADH)-modified γ-polyglutamic acid (γ-PGA) as the crosslinking agent, in which the BG plays a multifunctional role to endow the hydrogel with both dual-adhesive and bioactive properties. On one hand, the BG could improve the tissue-bonding strength by providing an alk. microenvironment to stimulate the bond formation between OSA and the amino groups on the surrounding tissues. On the other hand, BG endows the hydrogel with adhesiveness to implantable materials by releasing Ca ions, which might chelate with the carboxyl groups of the hydrogel matrix. In addn., the composite hydrogel showed excellent bioactivity to promote vascularization and accelerate tissue regeneration. This study demonstrates that a multifunctional hydrogel can be designed by utilizing the multifunctional ions released from silicate BG, and the BG/OSA hydrogel shows good potential as an adhesive and bioactive material for wound-healing applications.
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    60. 60
      Huang, B.; Sun, L. Y.; Wang, S. S.; Zhang, J. Y.; Ji, C. M.; Luo, J. H.; Zhang, W. X.; Chen, X. M. A Near-Room-Temperature Organic-Inorganic Hybrid Ferroelectric: [C6H5CH2CH2NH3]2[CdI4]. Chem. Commun. 2017, 53 (42), 5764– 5766,  DOI: 10.1039/C7CC02408H
      60
      A near-room-temperature organic-inorganic hybrid ferroelectric: [C6H5CH2CH2NH3]2[CdI4]
      Huang, Bo; Sun, Lin-Ying; Wang, Sha-Sha; Zhang, Jian-Yu; Ji, Cheng-Min; Luo, Jun-Hua; Zhang, Wei-Xiong; Chen, Xiao-Ming
      Chemical Communications (Cambridge, United Kingdom) (2017), 53 (42), 5764-5766CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      An org.-inorg. hybrid compd., [C6H5CH2CH2NH3]2[CdI4], exhibits a reversible ferroelec. phase transition at 301/297 K. Switchable dielec. const., second harmonic generation, and pyroelectricity were synchronously obsd. accompanied by the order-disorder phase transition. This finding promotes research on mol. ferroelecs. to search for promising multifunctional switching materials at near room temp.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c00830.

    • TGA-DTA results, crystallographic data, hydrogen bonding interaction data, SHG spectra, and calculation of spontaneous polarization Ps (PDF)

    Accession Codes

    CCDC 1991347–1991348 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.


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