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Molecular optical‐dielectric duple bistable switches are photoelectric (dielectric and fluorescent) multifunctional materials that can simultaneously convert optical and electrical signals in one device for seamless integration. However, exploring optical‐dielectric duple channels of dielectric and photoluminescence is still a bigger challenge than single dielectric or photoluminescence bistable ones, which are hardly reported but probably will be heavily researched owing to the new generation artificial intelligence development needs in the future. Herein, a new optical‐dielectric duple bistable switches material, [(CH3)3NCH2CH3]2MnCl4 (I), was obtained by a simple method for volatilization of solvents. Variable temperature single crystal X‐ray analysis indicates that material I has a reversible bistable structure (order‐disorder structure phase transition) corresponding to switching "ON′′ and "OFF′′. Unlike the single dielectric bistable structures that were previously reported, material I also own bistable features in terms of fluorescence property. This material enriches the specific examples of photoelectric duple function switch materials and facilitates the development of required devices. [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]

Organic–inorganic hybrid materials with a high-temperature phase transition have been widely applied as a kind of smart material. In this work, a new organic–inorganic 2H-perovskite compound, namely [Me3NCH2CH3]CdCl3 (1), is reported with a high temperature dielectric transition showing excellent reversibility and sustainability. 1 has an ABX3 hybrid perovskite structure, where A is a [Me3NCH2CH3]+ cation, B is a divalent metal atom, and X is a halogen atom. Differential scanning calorimetry (DSC) and dielectric measurements were applied for further characterization. Variable temperature single-crystal X-ray diffraction revealed that 1 crystallizes in the orthorhombic Pbca space group (No. 61) at 293 K and hexagonal P63/mmc space group (No. 194) at 363 K. The structural phase transition is primarily attributed to an ordered–disordered type resulting from the [Me3NCH2CH3]+ cations. Organic–inorganic perovskite compounds, as a result of a long exploration history and forward-looking prospects, can deepen research into molecular materials and their physical properties can be effectively optimized in the next-generation of temperature-responsive electrical switches. [ABSTRACT FROM AUTHOR]

Piezoelectric materials are a class of important functional materials applied in high‐voltage sources, sensors, vibration reducers, actuators, motors, and so on. Herein, [(CH3)3S]3[Bi2Br9](1) is a brilliant semiconducting organic–inorganic hybrid perovskite‐type non‐ferroelectric piezoelectric with excellent piezoelectricity. Strikingly, the value of the piezoelectric coefficient d33 is estimated as ≈18 pC N−1. Such a large piezoelectric coefficient in non‐ferroelectric piezoelectric has been scarcely reported and is comparable with those of typically one‐composition non‐ferroelectric piezoelectrics such as ZnO (3pC N−1) and much greater than those of most known typical materials. In addition, 1 exhibits semiconducting behavior with an optical band gap of ≈2.58 eV that is lower than the reported value of 3.37 eV for ZnO. This discovery opens a new avenue to exploit molecular non‐ferroelectric piezoelectric and should stimulate further exploration of non‐ferroelectric piezoelectric due to their high stability and low loss characteristics. As easy as pie: A semiconducting organic–inorganic hybrid perovskite‐type non‐ferroelectric piezoelectric with excellent piezoelectricity is reported. The value of the piezoelectric coefficient d33 is estimated as ≈18 pC N−1. Such a large piezoelectric coefficient in non‐ferroelectric piezoelectric has been scarcely reported. Furthermore, [(CH3)3S]3[Bi2Br9] exhibits semiconducting behavior with an optical band gap of ≈2.58 eV. [ABSTRACT FROM AUTHOR]

Switchable materials have developed greatly, because of their potential applications in many fields, such as data storage and dielectric devices, while the "ON"/"OFF" of the dielectric effect in polycrystalline materials to achieve high contrast is still a great challenge, which gradually become one of the research hotspots in the materials science and electronics. Herein, we report a prominent dielectric switch of (TMCM)2Hg2Cl6 (1, TMCM = trimethylchloromethyl ammonium), with a high phase transition temperature (Tc) of 405.8 K and an extremely high contrast of ca. 14. Such a breakthrough is elucidated from the highly disordered TMCM and the severely deformed of Hg2Cl6 in high temperature phase. By understanding the properties of superior dielectric, a feasible switch mechanism can be constructed to inject new vitality into the field of molecular medium switch. An organic‐inorganic polycrystalline dielectric switch, [(trimethylchloromethyl ammonium)2Hg2Cl6], shows an extremely high contrast of ca. 14. [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]

By introducing halogens to 16 symmetric tetramethylammonium, one new molecular ferroelastic compound [TMBMA] [PF6] (1) (TMBMA = trimethylbromomethylammonium) was successfully synthesized. Differential scanning calorimetry (DSC) measurements demonstrated that 1 underwent a typical first-order phase transition at ca. 380 K with a large thermal hysteresis of 30 K. Single crystal X-ray diffraction data, the variable-temperature powder X-ray diffraction (PXRD) patterns and the complex domain-wall orientations suggested that the phase transition from monoclinic (P21/c) to cubic (Pm3̅m) belongs to a ferroelastic phase transition with an Aizu notation of m3̅mF2/m. Dielectric studies show that 1 exhibits distinct switchable dielectric behavior and satisfactory thermal stability, revealing its potential application in dielectric switches. As expected, the TMBMA cations bearing an ordered–disordered motion turn out to be crucial in the generation of the ferroelastic phase transition. Therefore, this molecular design strategy of introducing halogens to tetraalkylammoniums can not only reduce the symmetry of the tetraalkylammonium molecules at room temperature, but can also maintain the highly disordered characteristics at high temperatures. This provides an efficient route for us to find new molecular ferroelastics and dielectric switches. [ABSTRACT FROM AUTHOR]

The rational selection of ligands is vitally important in the construction of new organic–inorganic hybrid three‐dimensional perovskite complexes. As part of an exploration of perovskite‐type materials, two new Na–I compounds based on the piperazine ligand, namely poly[piperazinediium [tri‐μ‐iodido‐sodium]], {(C4H12N2)[NaI3]}n, 1, and catena‐poly[tris(piperazinediium) [[triiodidosodium]‐μ‐iodido] triiodide monohydrate], {(C4H12N2)3[NaI4]I3·H2O}n, 2, have been synthesized by adjusting the stoichiometric ratio of sodium iodide and piperazine, and were characterized by single‐crystal X‐ray diffraction. In the crystal structures of 1 and 2, each NaI cation is linked to six I atoms, but the compounds show completely different configurations. In 1, the structure includes a perovskite‐like array of vertex‐sharing NaI6 octahedra stretching along the direction of the three axes, and each piperazinediium dication is enclosed in the NaI3 perovskite cage. However, in 2, each NaI atom bridges a single I atom to form a one‐dimensional linear chain, and complex intermolecular hydrogen bonds connect these one‐dimensional chains into a three‐dimensional supramolecular network. [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]

Two new organic ionic plastic crystals (OIPCs), [TMBM] [ClO4] (1) and [TMBM] [BF4] (2) (TMBM = trimethylbromomethyl ammonium), were successfully synthesized. Systematic characterization via differential scanning calorimetry (DSC), variable-temperature single-crystal X-ray diffraction, variable-temperature powder X-ray diffraction (PXRD) and dielectric measurements demonstrated that 1 and 2 undergo reversible high-temperature sequential phase transitions accompanied by distinct stepwise switchable dielectric anomalies (1 at 358 K and 388 K and 2 at 346 K and 379 K). The structural relatively ordered-disordered transitions of ClO4−, BF4− and [TMBM]+ contributed to the switching of the dielectric constant from the low-dielectric state to the high-dielectric state. Thus, OIPCs consisting of spherical ammonia cations and inorganic acid anions are proven to be promising in the search for high-temperature multi-step switchable dielectric materials. [ABSTRACT FROM AUTHOR]

A novel material with coexisting switchable nonlinear optical (NLO) and dielectric properties, [trimethylchloromethyl ammonium]2[ZnCl4] [(TMCM)2-ZnCl4], which undergoes two reversible solid state phase transitions at 337 K (Tc1) and 258 K (Tc2), respectively, has been successfully synthesized and grown as block crystals. Exceptionally, variable-temperature X-ray single crystal structural analyses of (TMCM)2-ZnCl4 reveal that the unusual space group changes from P212121 at 223 K to P21/c between Tc2 and Tc1 to Pmcn above Tc1. As expected, the dielectric value of (TMCM)2-ZnCl4 exhibits two remarkable step-like enlargements around Tc1 and Tc2, indicating that it exhibits a low dielectric state, an intermediate dielectric state and a high dielectric state. In particular, the second harmonic generation (SHG) efficiency shows a sharp step-like increase from almost zero to 0.47, and its SHG activities in a high-NLO state can be recovered after several cycles without any attenuation. The transitions of (TMCM)2-ZnCl4 could be intrinsically ascribed to the sequential order–disorder transformations of both the cations and anions. All these results demonstrate its potential application as a switchable and tunable molecular dielectric and NLO material. [ABSTRACT FROM AUTHOR]

By introducing halogens to 16 symmetric tetramethylammonium, one new molecular ferroelastic compound [TMBMA] [PF6] (1) (TMBMA = trimethylbromomethylammonium) was successfully synthesized. Differential scanning calorimetry (DSC) measurements demonstrated that 1 underwent a typical first-order phase transition at ca. 380 K with a large thermal hysteresis of 30 K. Single crystal X-ray diffraction data, the variable-temperature powder X-ray diffraction (PXRD) patterns and the complex domain-wall orientations suggested that the phase transition from monoclinic (P21/c) to cubic (Pm3̅m) belongs to a ferroelastic phase transition with an Aizu notation of m3̅mF2/m. Dielectric studies show that 1 exhibits distinct switchable dielectric behavior and satisfactory thermal stability, revealing its potential application in dielectric switches. As expected, the TMBMA cations bearing an ordered–disordered motion turn out to be crucial in the generation of the ferroelastic phase transition. Therefore, this molecular design strategy of introducing halogens to tetraalkylammoniums can not only reduce the symmetry of the tetraalkylammonium molecules at room temperature, but can also maintain the highly disordered characteristics at high temperatures. This provides an efficient route for us to find new molecular ferroelastics and dielectric switches. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid materials with a high-temperature phase transition have been widely applied as a kind of smart material. In this work, a new organic–inorganic 2H-perovskite compound, namely [Me3NCH2CH3]CdCl3 (1), is reported with a high temperature dielectric transition showing excellent reversibility and sustainability. 1 has an ABX3 hybrid perovskite structure, where A is a [Me3NCH2CH3]+ cation, B is a divalent metal atom, and X is a halogen atom. Differential scanning calorimetry (DSC) and dielectric measurements were applied for further characterization. Variable temperature single-crystal X-ray diffraction revealed that 1 crystallizes in the orthorhombic Pbca space group (No. 61) at 293 K and hexagonal P63/mmc space group (No. 194) at 363 K. The structural phase transition is primarily attributed to an ordered–disordered type resulting from the [Me3NCH2CH3]+ cations. Organic–inorganic perovskite compounds, as a result of a long exploration history and forward-looking prospects, can deepen research into molecular materials and their physical properties can be effectively optimized in the next-generation of temperature-responsive electrical switches. [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 new organic ionic plastic crystals (OIPCs), [TMBM] [ClO4] (1) and [TMBM] [BF4] (2) (TMBM = trimethylbromomethyl ammonium), were successfully synthesized. Systematic characterization via differential scanning calorimetry (DSC), variable-temperature single-crystal X-ray diffraction, variable-temperature powder X-ray diffraction (PXRD) and dielectric measurements demonstrated that 1 and 2 undergo reversible high-temperature sequential phase transitions accompanied by distinct stepwise switchable dielectric anomalies (1 at 358 K and 388 K and 2 at 346 K and 379 K). The structural relatively ordered-disordered transitions of ClO4−, BF4− and [TMBM]+ contributed to the switching of the dielectric constant from the low-dielectric state to the high-dielectric state. Thus, OIPCs consisting of spherical ammonia cations and inorganic acid anions are proven to be promising in the search for high-temperature multi-step switchable dielectric materials. [ABSTRACT FROM AUTHOR]

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 (Et 3 NC 2 H 4 Br)FeCl 4 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 ( T C ) 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 10 6 at 500 Hz and a dielectric switching ratio surpassing 10 3 . 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 P 2 1 / 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.

The impact of molecular point groups on phase transition materials has been seldom discussed. Two organic cations with different symmetries were incorporated into a [SnCl 6 ] 2- framework. By breaking the symmetry of cations, a novel hybrid material with two successive phase transitions featuring a rare "on-off-on" nonlinear optical switch was obtained.

Antiferroelectric (AFE) materials, characterized by double electric hysteresis loops, can be transformed to the ferroelectric (FE) phase under an external electric field, making them promising candidates for electronic energy storage and solid-state refrigeration. Additionally, the field-induced strain in AFE materials is contingent upon the direction of the electric field, rendering it with a switching characteristic. Although AFE materials have made progress in the field of energy storage and negative electrocaloric effect, the coexistence of AFE and ferroelasticity is still rarely reported. Here, two isomorphic organic-inorganic hybrid perovskites, HDAEPbCl 4 and HDAEPbBr 4 (HDAE is [2-(hydroxydimethylammonio)ethan-1-aminium]), exhibiting FE-AFE-PE (PE is paraelectric) phase transitions, are presented. Remarkably, the temperature range where AFE and ferroelasticity coexist is significantly broadened from 59.9 K to 115.1 K by strengthening short-range forces via halogen substitution. This discovery extends the family of FE, AFE, and ferroelastic materials, contributing to the development of multifunctional materials and advancing multifunctional material development., (© 2024 Wiley‐VCH GmbH.)

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 ( T c ). In this study, a one-dimensional hybrid perovskite of (TEACCl)PbBr 3 (1, TEACCl = Et 3 NCH 2 Cl) was successfully designed and synthesized with a T c = 390 K. Disordering of TEACCl + on the heating process is the origin of the structural phase transition of 1 from the P 2 1 / c to P 6 3 / 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 T c switching materials.

Molecular optical-dielectric duple bistable switches are photoelectric (dielectric and fluorescent) multifunctional materials that can simultaneously convert optical and electrical signals in one device for seamless integration. However, exploring optical-dielectric duple channels of dielectric and photoluminescence is still a bigger challenge than single dielectric or photoluminescence bistable ones, which are hardly reported but probably will be heavily researched owing to the new generation artificial intelligence development needs in the future. Herein, a new optical-dielectric duple bistable switches material, [(CH 3 ) 3 NCH 2 CH 3 ] 2 MnCl 4 (I), was obtained by a simple method for volatilization of solvents. Variable temperature single crystal X-ray analysis indicates that material I has a reversible bistable structure (order-disorder structure phase transition) corresponding to switching "ON'' and "OFF''. Unlike the single dielectric bistable structures that were previously reported, material I also own bistable features in terms of fluorescence property. This material enriches the specific examples of photoelectric duple function switch materials and facilitates the development of required devices., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this paper, three zero-dimensional organic-inorganic hybrid compounds [(CH 3 ) 3 S] 2 [CdBr 4 ] (1), [(CH 3 ) 3 S] 2 [MnBr 4 ] (2) and [(CH 3 ) 3 S] 2 [ZnBr 4 ] (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 [(Me 3 ) 3 S] + and [MBr 4 ] 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 P2 1 2 1 2 1 . 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.

[C 6 N 2 H 18 ][SbI 5 ] (1), a novel metal halide semiconductor with dielectric relaxation behavior, has been successfully synthesized, in which the cavities between the one-dimensional [SbI 5 ] n 2- polyanions are occupied by 2-methyl-1,5-pentanediammonium (2-MPDA) cations. 1 undergoes a reversible solid-state phase transition at T C = 192.7 K and shows a step-like dielectric anomaly. Interestingly, above T C , distinct dielectric dispersion in a wide temperature range is also witnessed. Remarkably, the solid state UV-vis diffuse reflectance spectrum of 1 exhibits a slightly gentler absorption edge at about 650 nm; that is, 1 adopts an indirect band gap with 1.92 electron volts. The combined narrow band gap, strong photoconductivity effect, and excellent dielectric relaxation might shed light on the exploitation of lead-free hybrid metal halide molecular materials with promising application prospects in thermoresponsive relaxation-type dielectric materials and photovoltaic conversion devices.

Piezoelectric materials are a class of important functional materials applied in high-voltage sources, sensors, vibration reducers, actuators, motors, and so on. Herein, [(CH 3 ) 3 S] 3 [Bi 2 Br 9 ](1) is a brilliant semiconducting organic-inorganic hybrid perovskite-type non-ferroelectric piezoelectric with excellent piezoelectricity. Strikingly, the value of the piezoelectric coefficient d 33 is estimated as ≈18 pC N -1 . Such a large piezoelectric coefficient in non-ferroelectric piezoelectric has been scarcely reported and is comparable with those of typically one-composition non-ferroelectric piezoelectrics such as ZnO (3pC N -1 ) and much greater than those of most known typical materials. In addition, 1 exhibits semiconducting behavior with an optical band gap of ≈2.58 eV that is lower than the reported value of 3.37 eV for ZnO. This discovery opens a new avenue to exploit molecular non-ferroelectric piezoelectric and should stimulate further exploration of non-ferroelectric piezoelectric due to their high stability and low loss characteristics., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The perovskite structure is rich in ferroelectricity. In contrast, ferroelectric antiperovskites have been scarcely confirmed experimentally since the discovery of M 3 AB-type antiperovskites in the 1930s. Ferroelectricity is now revealed in an organic-inorganic hybrid X 3 AB antiperovskite structure, which exhibits a clear ferroelectric phase transition 6/mmmF6mm with a high Curie point of 480 K. The physical properties across the phase transition are obviously changed along with the symmetry requirements, providing solid experimental evidence for the ferroelectric phase transition. More interestingly, the discovered antiperovskite shows intense photoluminescence and triboluminescence properties. The confirmation of the triboluminescent ferroelectric antiperovskite will open new avenues to explore excellent optoelectronic properties in the antiperovskite family., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The rational selection of ligands is vitally important in the construction of new organic-inorganic hybrid three-dimensional perovskite complexes. As part of an exploration of perovskite-type materials, two new Na-I compounds based on the piperazine ligand, namely poly[piperazinediium [tri-μ-iodido-sodium]], {(C 4 H 12 N 2 )[NaI 3 ]} n , 1, and catena-poly[tris(piperazinediium) [[triiodidosodium]-μ-iodido] triiodide monohydrate], {(C 4 H 12 N 2 ) 3 [NaI 4 ]I 3 ·H 2 O} n , 2, have been synthesized by adjusting the stoichiometric ratio of sodium iodide and piperazine, and were characterized by single-crystal X-ray diffraction. In the crystal structures of 1 and 2, each Na I cation is linked to six I atoms, but the compounds show completely different configurations. In 1, the structure includes a perovskite-like array of vertex-sharing NaI 6 octahedra stretching along the direction of the three axes, and each piperazinediium dication is enclosed in the NaI 3 perovskite cage. However, in 2, each Na I atom bridges a single I atom to form a one-dimensional linear chain, and complex intermolecular hydrogen bonds connect these one-dimensional chains into a three-dimensional supramolecular network., (open access.)

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.

The title compound, [Cu(C7H3NO4)(C5H6N2)(C3H7NO] n , is an amino-function-alized chiral metal-organic framework with (10,3)-a topology. It has been constructed via the assembly of the achiral triconnected pyridine-3,5-di-carboxyl-ate (3,5-PDC) building block and a triconnected Cu(II) atom. Each Cu(II) ion is coordinated by two O atoms and one N atom, respectively, of three crystallographically independent 3,5-PDC ligands. The square-pyramidal (CuN2O3) coordination geometry of the Cu(II) ion is completed by an N atom of a terminal 4-amino-pyridine (4-APY) ligand and the O atom of a terminal N,N-di-methyl-formamide (DMF) ligand to give a triconnected 'T'-shaped secondary building unit, which becomes trigonal in the resulting (10,3)-a topology. In the three-dimensional structure, weak N-H⋯O hydrogen bonds are observed in which the donor N-H groups are provided by the 4-APY ligands and the acceptor O atoms are provided by the non-coordinating carboxylate O atoms of the 3,5-PDC ligands.