Search

With the increasing research on giant dielectric materials, there is growing interest in the development of switching materials with giant dielectric properties. In this study, a novel organic–inorganic hybrid material (Et3NC2H4Br)FeCl4 was synthesized. It was characterized through differential scanning calorimetry (DSC) and in situ temperature-dependent powder X-ray diffraction (PXRD), which determined its phase transition temperature (TC) to be 362 K. Temperature-dependent dielectric measurements revealed that the material exhibited switchable dielectric properties, with the real part of the dielectric constant exceeding 106 at 500 Hz and a dielectric switching ratio surpassing 103. The ratio refers to the ratio between the high dielectric state and the low dielectric state of a step-like dielectric anomaly. Single-crystal X-ray diffraction (SCXRD) analysis confirmed that the material crystallized in the P21/c space group with a zero-dimensional structure. The optical bandgap, determined through UV-visible spectroscopy, was calculated to be 2.62 eV. Additionally, analysis using Hirshfeld surfaces and 2D fingerprint plots revealed that the predominant intermolecular interactions are H⋯Cl and H⋯H interactions. This study is anticipated to provide insights and hope for the design and application of high-temperature giant dielectric switching materials. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) have drawn increasing attention for their promising applications in thermal switches, data communication, and energy storage. Because of the complexity of the interactions between molecules, it is still a challenge to design PCMs with a desired high phase transition temperature (Tc). In this study, a one-dimensional hybrid perovskite of (TEACCl)PbBr3 (1, TEACCl = Et3NCH2Cl) was successfully designed and synthesized with a Tc = 390 K. Disordering of TEACCl+ on the heating process is the origin of the structural phase transition of 1 from the P21/c to P63/mmc structure. It is noted that the phase transition is associated with an excellent switchable dielectric property, which indicates that 1 has the potential to be applied to sensor equipment. After calculation, 1 is an infrequent indirect bandgap semiconductor with an energy gap of 3.57 eV. Moreover, 1 exhibits strong red fluorescence under irradiation of UV light. This work will provide guidance for designing high Tc switching materials. [ABSTRACT FROM AUTHOR]

In this paper, three zero-dimensional organic–inorganic hybrid compounds [(CH3)3S]2[CdBr4] (1), [(CH3)3S]2[MnBr4] (2) and [(CH3)3S]2[ZnBr4] (3) were synthesized. The phase transition behavior of 1, 2 and 3 was well characterized by differential scanning calorimetry (DSC) and variable temperature single crystal diffraction measurements. The phase transition temperature of 1, 2 and 3 was at ca. 315 K in the heating process. The vigorous ordered–disordered reorientation and displacement motion of [(Me3)3S]+ and [MBr4]2− of 1, 2 and 3 induce the structural phase transition from the centrosymmetric (CS) space group Pnma to the non-centrosymmetric (NCS) space group P212121. The apparent second-harmonic generation (SHG) switching responses further confirm this CS to NCS symmetry breaking. Moreover, dielectric studies illustrate that 1, 2 and 3 display distinctly switchable dielectric behavior, revealing their potential application in dielectric switches. This finding suggests that sulfonium-based organic–inorganic hybrids can be used to build phase transition materials, broadening the way for exploring dielectric and nonlinear optical (NLO) switching materials. [ABSTRACT FROM AUTHOR]

A novel organic–inorganic ABX3 perovskite-type material with specific hydrogen bonding interactions, N,N-dimethylethanolammonium trichlorocadmate ([DMEA]CdCl3), has been synthesized as a phase transition material. It is notable that the DMEA cations are arranged to form one-dimensional chains connected by hydrogen bonds at room temperature, which are very sparse in other perovskite-type compounds. The strong intermolecular interactions have made the phase transition temperature of the material reach up to 429 K, as confirmed by differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements. The origin of the symmetry-breaking phase transition is associated with the motion or reorientation of the DMEA cations, accompanied by the crystal structures from orthorhombic Pnma to monoclinic P21/c with the temperature decreases. The finding of [DMEA]CdCl3 with unprecedented hydrogen bonding interactions has opened a new avenue to design novel phase transition materials with higher transition temperatures. [ABSTRACT FROM AUTHOR]

Bistable optical-electrical duplex switches represent a class of highly desirable intelligent materials because of their potential applications in the fields of next-generation flexible devices. However, controllable photoelectric switchable materials with high-performance dielectric-switching and optical-switching properties are still scarce, with triplex bistable switches being rarely reported. Herein, a novel optoelectronic triple-functional organic–inorganic material, 5-azonia-spiro[4,4]nonane tetrabromomanganese (1, [ASN]2[MnBr4], ASN = (CH2)4N(CH2)4), which undergoes a reversible solid-state phase transition around 327 K and exhibits a recognizable second harmonic generation (SHG) effect between SHG-on and SHG-off states, has been successfully synthesized and grown as block crystals. Intriguingly, the bromine-doped crystal can exhibit intense green luminescence with a high quantum yield of 13.07% under UV excitation, extending its application in the field of photoelectric seamless integration and/or flexible multifunctional devices. [ABSTRACT FROM AUTHOR]

Two isostructural ionic cobalt(ii) halides, trimethylchloromethyl ammonium tetrachlorocobalt(ii) (1, [Me3NCH2Cl]2[CoCl4]) and trimethylbromomethyl ammonium tetrabromocobalt(ii) (2, [Me3NCH2Br]2[CoBr4]), have been discovered as new high-temperature phase transition materials. 1 exhibits two successive structural phase transitions from P212121 to P21/c at 252 K and then to Pnma at 335 K, accompanied by step-like dielectric anomalies. The two-step sequential reversible phase transitions of 1 derive from the order–disorder transformation of CoCl4 anions and organic Me3NCH2Cl cations, respectively. Its analogue 2 also crystallizes in P21/c at 293 K by changing the halogen atoms of both cations and anions of 1. Unlike 1, 2 displays only one structural phase transition with a much higher transition temperature at 387 K, which is mainly influenced by intermolecular interactions and more energy is required to provide the freedom of the motion. All the findings in the present work indicate that the phase transition temperature and properties of materials can be tuned by using halogens in this series of compounds, which could open a new way to design and assemble novel high-temperature phase transition materials. [ABSTRACT FROM AUTHOR]

Following our recent findings on dielectric materials, we synthesized a new host–guest supramolecular metal–halide compound, [(2-AMPD)(18-crown-6)]CuCl4 (1, 2-AMPD = 2-aminomethylpiperidinium). Systematic characterization techniques such as variable-temperature crystal structure analyses, differential scanning calorimetry (DSC) measurements, temperature-dependent dielectric measurements and powder X-ray diffraction (PXRD) measurements demonstrate that 1 undergoes a reversible phase transition at room temperature, accompanied by switchable dielectric responses and remarkable anisotropy along three different crystallographic axes. The structural phase transition mechanism is triggered by the order–disorder transition of the 18-crown-6 molecules. We believe that these findings might further promote the application of a host–guest inclusion compound in the field of switchable dielectric materials. [ABSTRACT FROM AUTHOR]

Bistable optical-electrical duplex switches represent a class of highly desirable intelligent materials because of their potential applications in the fields of next-generation flexible devices. However, controllable photoelectric switchable materials with high-performance dielectric-switching and optical-switching properties are still scarce, with triplex bistable switches being rarely reported. Herein, a novel optoelectronic triple-functional organic–inorganic material, 5-azonia-spiro[4,4]nonane tetrabromomanganese (1, [ASN]2[MnBr4], ASN = (CH2)4N(CH2)4), which undergoes a reversible solid-state phase transition around 327 K and exhibits a recognizable second harmonic generation (SHG) effect between SHG-on and SHG-off states, has been successfully synthesized and grown as block crystals. Intriguingly, the bromine-doped crystal can exhibit intense green luminescence with a high quantum yield of 13.07% under UV excitation, extending its application in the field of photoelectric seamless integration and/or flexible multifunctional devices. [ABSTRACT FROM AUTHOR]