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Molecular rotational motion is crucial in artificial molecular machines and is expected to be very significant for the development of an electronic information molecular machine as mentioned in the 2016 Nobel Prize. However, controlling multiple motor modes is a huge challenge. Here, we report a case in which the structural phase transition effectively triggers multiple motor modes by regulating the rotational speed of the cation and/or anion. A novel switchable crystalline supramolecular rotor, [(cyclohexylammonium)(18-crown-6)] FSO

An organic-inorganic perovskite compound [(CH

Although the first ferroelectric discovered in 1920 is Rochelle salt, a typical molecular ferroelectric, the front-runners that have been extensively studied and widely used in diverse applications, such as memory elements, capacitors, sensors, and actuators, are inorganic ferroelectrics with excellent electrical, mechanical, and optical properties. With the increased concerns about the environment, energy, and cost, molecular ferroelectrics are becoming promising supplements for inorganic ferroelectrics. The unique advantages of high structural tunability and homochirality, which are unavailable in their inorganic counterparts, make molecular systems a good platform for manipulating ferroelectricity. Remarkably, based on the Neumann's principle and the Curie symmetry principle defining the group-to-subgroup relationship, we have found some outstanding high-temperature molecular ferroelectrics, like diisopropylammonium bromide (DIPAB) with a large spontaneous polarization up to 23 μC/cm

Molecular ferroelectrics are attracting tremendous interest because of their low cost, mechanical flexibility, easy processing, low weight, and low acoustical impedance. Moreover, their combination of ferroelectric and optical properties has led to investigations of their many potential applications, such as low-energy electron excitation and field emission displays. However, luminescent molecular ferroelectrics have rarely been reported, except for several AMnX3-type or lanthanide ion-based luminescent ferroelectrics. Here, we report the first above-room-temperature phosphonium-based molecular ferroelectric perovskite, [(CH3)4P]CdCl3 (1), with a high Curie temperature (Tc = 348 K) and moderate remanent polarization (Pr = 0.43 μC/cm2). Using piezoresponse force microscopy (PFM), the typical stripe-like domains of ferroelectrics can be observed. Moreover, 1 exhibits orange luminescence under UV excitation after doping with Sb3+, which represents a first step toward realizing luminescence-enhanced molecular ferroelectrics with various wavelengths. These results will inspire the further exploration of phosphonium-based ferroelectrics and pave the way toward practical applications in ferroelectric luminescence and/or multifunctional devices. A molecule that can be manipulated with electric fields while simultaneously acting as a light-emitting phosphor could find use in next-generation photovoltaics. Ferroelectric materials are positively charged on one end and negatively on the other. Recent work suggests that the spontaneous dipoles formed by these charges can help engineer high outputs in solar cells. Lin Zhou from Southeast University in Nanjing, China, and colleagues have developed a ferroelectric with improved characteristics for device manufacturing. The team combined organo-phosphorus cations with trichlorocadmate anions to produce an organic–inorganic composite that can be synthesized at room temperature, instead of the energetically intense conditions needed for conventional all-inorganic ferroelectrics. Adding small portions of antimony ions to the molecule generated strong luminescent emissions that may be used to concentrate and direct solar radiation. A phosphonium-based perovskite, [(CH3)4P]CdCl3, is designed and synthesized, which shows ferroelectric characteristics below 348 K as revealed by the observation of typical stripe-like domains and hysteresis loops. By doping with Sb3+, this material exhibits orange luminescence under UV excitation. This work will open new avenues in designing multifunctional luminescent molecular ferroelectrics.

The past decade has witnessed much progress in designing molecular ferroelectrics, whose intrinsic mechanical flexibility, structural tunability, and easy processability are desirable for next-generation flexible and wearable electronic devices. However, an obstacle in expanding their promising applications in nonvolatile memory elements, capacitors, and sensors is effectively modulating the Curie temperature ( T

Organic-inorganic hybrid perovskite-type multiferroics have attracted considerable research interest owing to their fundamental scientific significance and promising technological applications in sensors and multiple-state memories. The recent achievements with divalent metal dicyanamide compounds revealed such malleable frameworks as a unique platform for developing novel functional materials. Herein, two 3D organic-inorganic hybrid perovskites [Et

To date, the field of ferroelectric random access memories (FeRAMs) is mainly dominated by inorganic ferroelectric thin films like Pb(Zr,Ti)O3, which suffer from the issues of environmental harmfulness, high processing temperatures, and high fabrication costs. In these respects, molecular ferroelectric thin films are particularly advantageous and thus become promising alternatives to the conventional inorganic ones. For the prospect of FeRAMs applications, they should fulfill the requirements of effective polarization switching and low-voltage, high-speed operation. Despite recent advancements, molecular ferroelectric thin films with such high performance still remain a huge blank. Herein we present the first example of a large-area continuous biaxial molecular ferroelectric thin film that gets very close to the goal of application in FeRAMs: [Hdabco]BF4 (dabco = diazabicyclo[2.2.2]octane). In addition to excellent film performance, it is the coexistence of a low coercive voltage of ∼12 V and ultrafast po...

Three organic–inorganic hybrid analogues, ([Et3(n-Pr)P][Mn(dca)3]) 1, ([Et3(CH2CHCH2)P][Mn(dca)3]) 2, ([Et3(CH2OCH3)P][Mn(dca)3]) 3, [dca = dicyanamide, N(CN)2−], show similar three-dimensional perovskite frameworks, in which the guest phosphonium cations occupy the cavities. Compounds 1 and 3 belong to the orthorhombic noncentrosymmetric space group P212121 at room temperature, while compound 2 crystallizes in the monoclinic centrosymmetric space group P21/c. Differential scanning calorimetry (DSC) and dielectric measurements confirmed the phase transitions in compounds 1, 2 and 3, where subtle structural distinctions of guest cations affect the crystal lattices, phase transition temperatures and physical properties. Interestingly, compounds 1 and 3 are SHG active at room temperature and can be used as NLO switches tuned by guest cations and triggered by temperature.

A bistable optical–electrical duple switch belongs to a class of highly satisfying intelligent materials that can transform optical and electrical responses simultaneously in one device. A perovskite-type high-temperature phase transition compound with one-dimensional chain-like crystal structure, ([(CH3)3PCH2OCH3][PbBr3], 1), displays remarkable bistable photoluminescent-dielectric duple switching behaviors. The noteworthy order–disorder transition of the phosphonium cation and the motions of anions contribute to the phase transition, leading to the space group P21/c at a low temperature phase to C2/c at a high temperature phase. 1 exhibits a prominent step-like dielectric anomaly at 401.0 K and demonstrates novel optical properties with a band gap of 3.54 eV. The photoluminescence intensity suddenly declines from 398 K to 408 K, which may be attributed to the occurrence of phase transition. The electron cloud distributions of the frontier orbital in compound 1 have been calculated using a DFT program.

A new organic–inorganic hybrid compound [(CH3)3PCH2OH][Cd(SCN)3] (1) has been synthesized, which exhibits a reversible phase transition at 248.5 K confirmed by differential scanning calorimetry. The phase transition in 1 is from a centrosymmetric space group Pmcn to a non-centrosymmetric space group P21, so that 1 exhibits a switchable second harmonic generation (SHG) effect between SHG-on and SHG-off states. This phase transition also displays switchable dielectric behaviors between high and low dielectric states accompanied by the remarkable dielectric relaxation described by the Cole–Cole equation. Variable-temperature single-crystal X-ray diffraction analyses reveal that the origin of the phase transition can be attributed to the motion or reorientation of the [(CH3)3PCH2OH]+ cations and the movement of (SCN)− ions in solid-state crystals. These superior physical properties suggest that 1 could be a potential switchable dielectric and NLO relaxor-type material, which provides a new approach to design novel multiple switch materials.

A new organic–inorganic perovskite-type compound [(CH3)3PCH2OH][CdBr3] exhibits a ferroelastic phase transition at 339 K. Domain structures were observed and analyzed. The origin of the phase transition can be attributed to the motion or reorientation of the [(CH3)3PCH2OH]+ cations and the displacement of Cd2+ and Br− ions in solid-state crystals.

A design strategy of reducing the molecular symmetry was used to obtain a series of picrate-based high-temperature phase transition compounds. Their dielectric switching behaviours accompanied by phase transitions can be attributed to the order-disorder transitions of the cations and the displacements of both cations and anions.

Organic–inorganic hybrid perovskite, [CH3NH3]PbI3, holds a great potential for next-generation solar devices. However, whether the ferroelectricity exists in [CH3NH3]PbI3 and results in the ultrahigh performance is not at present clear. Beyond that, no hybrid lead iodide perovskite ferroelectric has yet been found. Here, using precise molecular modifications, we successfully designed a room-temperature hybrid perovskite ferroelectric, [(CH3)3NCH2I]PbI3. Because of the high-symmetry and nearly spherical shape of [(CH3)4N]+ cation, [(CH3)4N]PbI3 crystallizes in a centrosymmetric space group P63/m at room temperature and undergoes a structural phase transition at 184 K. Accompanied by the introduction of halogen atoms on the cation from F to I, the phase transition temperature gradually increases to 312 K and the space group transforms into a polar C2 at room temperature. The strongest halogen bond energy of [(CH3)3NCH2I]–I and the largest volume of [(CH3)3NCH2I]+ among these compounds might be possible reas...

It is known that perovskites with the general chemical formula of ABX

Molecular bistable dielectric switches represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light weights, and mechanical flexibility. However, most of these switches can only work at a very low temperature, extremely limiting their potential applications. Herein, three layered organic-inorganic hybrid perovskite-type compounds 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 dielectric switching reversibility and remarkable switching anti-fatigue, have been successfully designed. Differential scanning calorimetry and dielectric measurements for 1 confirm its reversible phase transition at around 166 K. Through anion modulation, the phase transition temperatures of 2 and 3 can be greatly improved up to 237 K and 254 K, respectively. Structural analysis discloses that the phase transition temperature's shifts may result from the differences among the inorganic 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 electrical switches. Such an anion-modulated method will open up new possibilities of highly efficiently tuning the phase transition temperature of molecular bistable dielectric switches.

The reactions of 4-(dimethylamino)pyridine (DMAP) and metal chloride in dilute hydrochloric acid yield two four-coordinate complexes, 1 (DMAP+)(FeCl4−) and 2 (DMAP+)2(CoCl42 −). The differential scanning calorimetry (DSC) measurements, temperature-dependent dielectric properties and variable-temperature single-crystal X-ray diffraction analyses of compound 1 confirmed the reversible isostructural phase transition with the same space group P21/n (No. 14) at 298 K and 373 K. The temperature-dependent single crystal structural analyses of compound 1 reveal the distinct and synchronous molecular motions of both the cationic and anionic moieties, where the orientational changes of organic cations and the order–disorder transformations of FeCl4− anions are mainly responsible for dielectric properties of compound 1. The variable-temperature structure analyses and the variable-temperature PXRD measurements reveal that compound 2 undergoes a reversible structural phase transition at around 381 K. The space groups of compound 2 change from triclinic P-1 in room temperature phase (RTP) to monoclinic C2/c in high temperature phase (HTP), accompanied by thermal and dielectric anomalies.

Tetramethylphosphonium dichromate ([(CH3)4P]2[Cr2O7], 1) undergoes a reversible phase transition at around 221 K. The results of the variable-temperature single-crystal X-ray structural analyses and the rotational potential energy calculations suggest that the phase transition is probably related to the order–disorder transition of the [Cr2O7]2– anion. The change of the space group from Pa-3 at room temperature to Pbca at low temperature is reflected in the peak-like dielectric response. Tetraethylphosphonium trichromate ([Et4P]2[Cr3O10], 2) crystallizes in the monoclinic space group P21/c at room temperature. Upon cooling and heating, the step-like dielectric anomalies observed at around 270 K indicate a reversible phase transition. Moreover, the rotational potential energy calculations certify the potential motion of the [Cr3O10]2– anion, being related to the phase transition. These findings open a new approach to the design of complexes that show phase transitions coupled with unusual dielectric properties.

The 3-morpholin-4-yl-propyl-ammine tetrafluoroborate (MPA + ) (BF 4 − ) ( 1 ) and the 3-morpholin-4-yl-propyl-ammine perchlorate (MPA + ) (ClO 4 − ) ( 2 ) were synthesized and separated as colorless block crystal. The (MPA + ) (BF 4 − ) undergoes a reversible phase transition at ca . 347.3 K with a hysteresis of 16.1 K. Dielectric measurement also can confirm the transition. The crystal structure determined at 300 K (monoclinic, P 2 1 /c, a = 9.978(2) A, b = 7.5206(15) Ǻ, c = 15.058(3) A, β = 96.99(3)°, v = 1121.6(4) A 3 , z = 4) and 373 K (triclinic, P -1, a = 10.021(7) A, b = 7.662(3) A, c = 7.920(4) A, α = 95.012(14)°, β = 101.67(4)°, γ = 91.48(3)°, v = 592.7(6) A 3 , z = 2) reveal that this compound has two phase. The most distinct is the BF 4 − anion is disorder at 373 K, which is probably the driving force of the phase transition. DSC measurement, dielectric measurement and the crystal structure of the compound 2 did not change at 300 K and 100 K.

Inorganic perovskite ferroelectrics are widely used in nonvolatile memory elements, capacitors, and sensors because of their excellent ferroelectric and other properties. Organic ferroelectrics are desirable for their mechanical flexibility, low weight, environmentally friendly processing, and low processing temperatures. Although almost a century has passed since the first ferroelectric, Rochelle salt, was discovered, examples of highly desirable organic perovskite ferroelectrics are lacking. We found a family of metal-free organic perovskite ferroelectrics with the characteristic three-dimensional structure, among which MDABCO ( N -methyl- N9 -diazabicyclo[2.2.2]octonium)–ammonium triiodide has a spontaneous polarization of 22 microcoulombs per square centimeter [close to that of barium titanate (BTO)], a high phase transition temperature of 448 kelvins (above that of BTO), and eight possible polarization directions. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.

Three analogue N-heterocyclic complexes, 1-propyl-1-methylpiperidinium perchlorate (1, [PMpip][ClO4]), 1-cyanomethyl-1-methylpiperidinium perchlorate (2, [CMpip][ClO4]), and 1-cyanomethyl-1-methylmorpholinium perchlorate (3, [CMmor][ClO4]) are identified as phase transition materials displaying switchable dielectric behaviors. Despite the common [ClO4]− anion and the closely related cations, compound 1 crystallizes in the orthorhombic space group P212121, but compounds 2 and 3 belong to the monoclinic space group P21/n with distinct cell dimensions. Compounds 1, 2 and 3 undergo reversible phase transitions around 199, 387 and 416 K, respectively, accompanied by notable step-like dielectric anomalies which could be switched by the phase transition and be tuned in distinct dielectric states. The respective dielectric constants in the high dielectric states are 1.2, 2.2 and 3.2 times that in the low dielectric states for compounds 1, 2 and 3. Generally, these differences in the phase transitions and dielectric properties are caused by the distinct molecular structures and hydrogen-bonding conformations resulting from the structural variations in the side-chain and the ring structure.

Recently, a plastic crystal of quinuclidinium perrhenate (${\mathrm{HQReO}}_{4}$) was reported to have the feasibility of controlling the crystallographic orientation in the grown crystal, but the corresponding temperature window is only about 22 K (345--367 K). Such a narrow window and uncertain ferroelectricity at room temperature would extremely limit its application potential. In this report, we prepared a large area high-quality polycrystalline thin film of ${\mathrm{HQReO}}_{4}$ and for the first time observed ferroelectricity in the temperature range from 298 to 367 K. Density functional theory calculations revealed the origin of room-temperature ferroelectricity is ascribed to the collaborative flipping of HQ (protonated quinuclidine) and ${\mathrm{ReO}}_{4}^{\ensuremath{-}}$, which is dynamically preferred in the presence of a $\mathrm{N}─\mathrm{H}\ensuremath{\cdots}\mathrm{O}$ hydrogen bond. A local piezoresponse force microscopy measurement was also employed to study the mechanisms of multiaxial polarization rotation and domain dynamics. By extending the ferroelectric temperature window to room temperature and the extraordinary thin-film processability, ${\mathrm{HQReO}}_{4}$ would certainly become a suitable candidate for next generation ferroelectric materials.

A bistable optical-electrical duple switch belongs to a class of highly satisfying intelligent materials that can transform optical and electrical responses simultaneously in one device. A perovskite-type high-temperature phase transition compound with one-dimensional chain-like crystal structure, ([(CH

A new organic-inorganic perovskite-type compound [(CH

A new perovskite-like inorganic-organic hybrid compound [Et3(n-Pr)P][Cd(dca)3] (1) (where [Et3(n-Pr)P]+ is the propyltriethylphosphonium cation and dca is a dicyanamide ligand) was discovered to undergo three reversible phase transitions at 270 K (T1), 386 K (T2), and 415 K (T3), respectively. The variable-temperature single-crystal X-ray structural analyses reveal that these sequential phase transitions originate from the deformations of the [Cd(dca)3]- frameworks and the concomitant reorientations of the [Et3(n-Pr)P]+ guest cations. It is found that 1 possesses a sensitive nonlinear optical (NLO) switching at T2 with a large contrast of ∼40 within a narrow temperature range of ∼7 K. Furthermore, 1 shows intriguing photoluminescence (PL) property, and the PL intensity suffers a plunge near T3. The multiple phase transitions, switchable NLO and tunable luminescent properties simultaneously exist in this inorganic-organic perovskite-like hybrid compound, suggesting its great potential application in molecular switches and photoelectric field.

An outstanding advantage of inorganic ceramic ferroelectrics is their usability in the polycrystalline ceramic or thin film forms, which has dominated applications in the ferroelectric, dielectric, and piezoelectric fields. Although the history of ferroelectrics began with the molecular ferroelectric Rochelle salt in 1921, so far there have been very few molecular ferroelectrics, with lightweight, flexible, low-cost, and biocompatible superior properties compared to inorganic ceramic ferroelectrics, that can be applied in the polycrystalline form. Here, a multiaxial molecular ferroelectric, guanidinium perchlorate ([C(NH2 )3 ]ClO4 ), with a record-high phase transition temperature of 454 K is presented. It is the rectangular polarization-electric field (P-E) hysteresis loops recorded on the powder and thin film samples (with respective large Pr of 5.1 and 8.1 µC cm-2 ) that confirm the ferroelectricity of [C(NH2 )3 ]ClO4 in the polycrystalline states. Intriguingly, after poling, the piezoelectric coefficient (d33 ) of the powder sample shows a significant increase from 0 to 10 pC N-1 , comparable to that of LiNbO3 single crystal (8 pC N-1 ). This is the first time that such a phenomenon has been observed in molecular ferroelectrics, indicating the great potential of molecular ferroelectrics being used in the polycrystalline form like inorganic ferroelectrics, as well as being viable alternatives or supplements to conventional ceramic ferroelectrics.

Two inorganic–organic hybrid compounds with zero-dimensional crystal structures, tetramethylphosphonium tetrachloroferrate(III) (compound 1, [(CH3)4P][FeCl4]) and tetramethylphosphonium tetrabromoferrate(III) (compound 2, [(CH3)4P][FeBr4]), are discovered as multifunctional materials exhibiting simultaneously switchable dielectric, magnetic, and optical properties. Despite the analogue chemical formulas, compounds 1 and 2 crystallize in the different noncentrosymmetric space groups, that is, P63mc and F43m, and exhibit distinct responses in the three above-mentioned physical channels, especially for the magnetic property. Compound 1 undergoes dielectric anomalies which could be tuned in three distinct dielectric states and switched by the sequential phase transitions around 362 and 436 K, respectively. The symmetry breaking occurring during the first phase transition is confirmed by the switchable temperature-dependent second harmonic generation (SHG) effect. Weak antiferromagnetic interactions are also ...

The title compound bis(dimethylammonium) bis(dicyanoethene-1,2-dithiolato)-nickel (II) undergoes a reversible dielectric transition occurring at about 260 K. The variable-temperature X-ray structural determinations reveal that both phases are monoclinic, space group C2/c with a = 16.383(3), b = 9.521(5), c = 13.631(3) A, β = 118.28(3)°, V = 1872.5(8) A3 at the room temperature (293 K), and with a = 15.885(5), b = 9.418(0), c = 13.771(3) A, β = 116.89(3)°, V = 1837.4(8) A3 at the low temperature (93 K). The [Ni(mnt)2]2 − anions form a non-uniform stacking pattern and interact with the [Me2NH2]+ cations by N–H∙∙∙S, N–H∙∙∙N hydrogen bonds, for the two phases. With temperature increasing, the cations and anions are shifting and thus result in the significant changes of the hydrogen bonds. The effect of these shifts is reflected in the dielectric behavior of the [Me2NH2]2[Ni(mnt)2] salt (mnt2 − = maleonitriledithiolate).

The direct reaction of ZnBr2 with H-1-mbtz [1-mbtz = 1-(1H-tetrazol-5-ylmethyl)-1H-benzotriazole] gives the two-dimensional complex [Zn(Br)(1-mbtz)] (1), whereas the reaction of benzotriazol-1-yl-acetonitrile with NaN3 in the presence of water and a Lewis acid (ZnBr2) affords the 2D coordination polymer [Zn2(OH)(1-mbtz)3H2O] (2). The central zinc atom in 1 is bonded to one terminal bromine atom and three different nitrogen atoms from two tetrazole ligands and one BTA group (BTA = benzotriazole), and each 1-mbtz ligand is coordinated to three zinc atoms forming a 2D framework. The coordination polyhedron around the metal atom in 2 is a slightly distorted trigonal bipyramid made up by one zinc atom, four nitrogen atoms as well as one oxygen atom, two of the 1-mbtz ligands coordinated to three zinc atoms and the third 1-mbtz ligand acts in a bidentate fashion, which leads to the formation of a complicated 2D network. The syntheses and solid-state structures of the two coordination polymers are reported.

To date, the field of ferroelectric random access memories (FeRAMs) is mainly dominated by inorganic ferroelectric thin films like Pb(Zr,Ti)O

Ferroelectrics are inseparable from symmetry breaking. Accompanying the paraelectric-to-ferroelectric phase transition, the paraelectric phase adopting one of the 32 crystallographic point groups is broken into subgroups belonging to one of the 10 ferroelectric 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 electric field results in a typical ferroelectric hysteresis loop. In addition, the responses of spontaneous polarization to other external excitations are related to a number of physical effects such as second-harmonic generation, piezoelectricity, pyroelectricity and dielectric properties. Based on these, this review summarizes recent developments in molecular ferroelectrics since 2011 and focuses on the relationship between symmetry breaking and ferroelectricity, offering ideas for exploring high-performance molecular ferroelectrics.

Reactions exchanging the cation in (nBu4N)[Ni(dmit)2] to cis-cyclohexane-1,4-diammonium (cis-CHDA) in the presence of [18]crown-6, benzo[18]crown-6 (B[18]crown-6) and dibenzo[18]crown-6 (DB[18]crown-6) yielded crystals of the monovalent [Ni(dmit)2] complex, namely (cis-CHDA)([18]crown-6)2[Ni(dmit)2]2 (1), (cis-CHDA)(B[18]crown-6)2[Ni(dmit)2]2 (2) and (cis-CHDA)(DB[18]crown-6)2[Ni(dmit)2]2 (3). The two ammonium groups (–NH3+) of the cis-CHDA dication at axial and equatorial positions interact with oxygen atoms of the corresponding upper and lower crown ethers to form sandwich-type supramolecular cationic structures. The lateral [Ni(dmit)2]− anion arrangements through S–S contacts along the short and long axis of [Ni(dmit)2] anions were realised in crystals of 1, 2, and 3 by the asymmetrical cis-CHDA dication. The temperature- and frequency-dependent anisotropic dielectric constants of a crystal of 1 were evaluated along the a, b and c axes, where the thermally activated motion of the structurally flexible cis-CHDA dication was consistent with the dielectric responses.

[Ni(dmit)2]− salt (dmit2− 2-thioxo-1,3-dithiole-4,5-dithiolate) with flexible supramolecular cation (4-cyanomethylanilinium)(dibenzo[18]crown-6) has been synthesized and investigated its structure, magnetism and rotation. The comparable large steric hindrances limit the rotation of cyanomethyl group to result in no phase transition occurred. Magnetic and potential energy calculations by DFT method were consistent with the magnetic and structure measurements.

A new organic-inorganic hybrid switchable and tunable dielectric compound, [(CH3)4P]4[Mn(SCN)6] (1), exhibits three distinct dielectric states above room temperature and undergoes two reversible solid-state phase transitions, including a structural phase transition at 330 K and a ferroelastic phase transition with the Aizu notation of mmmF2/m at 352 K. The variable-temperature structural analyses disclose that the origin of the phase transitions and dielectric anomalies can be ascribed to the reorientation or motion of both the [(CH3)4P](+) cations and [Mn(SCN)6](4-) anions in solid-state crystals.

Peroxisome proliferator-activated receptor γ (PPAR-γ) has a protective role in several neurological diseases. The present study investigated the effect of the PPAR-γ agonist, pioglitazone, on the mammalian target of rapamycin (mTOR) signaling pathway in a rat model of pentylenetetrazol (PTZ)-induced status epilepticus (SE). The investigation proceeded in two stages. First, the course of activation of the mTOR signaling pathway in PTZ-induced SE was examined to determine the time-point of peak activity, as reflected by phopshorylated (p)-mTOR/mTOR and p-S6/S6 ratios. Subsequently, pioglitazone was administrated intragastrically to investigate its effect on the mTOR signaling pathway, through western blot and immunochemical analyses. The levels of the interleukin (IL)-1β and IL-6 inflammatory cytokines were detected using ELISA, and neuronal loss was observed via Nissl staining. In the first stage of experimentation, the mTOR signaling pathway was activated, and the p-mTOR/mTOR and p-S6/S6 ratios peaked on the third day. Compared with the vehicle treated-SE group, pretreatment with pioglitazone was associated with the loss of fewer neurons, lower levels of IL-1β and IL-6, and inhibition of the activation of the mTOR signaling pathway. Therefore, the mTOR signaling pathway was activated in the PTZ-induced SE rat model, and the PPAR-γ agonist, pioglitazone, had a neuroprotective effect, by inhibiting activation of the mTOR pathway and preventing the increase in the levels of IL-1β and IL-6.

Accounting supervision is both one of the basic functions of accountancy and a major part of economic supervision. Nowadays, Chinese weak accounting supervision basically results from the faulty designed supervision system. This paper is to analyze the situation and problems of the current accounting supervision to propose suggestions on the improvement of accounting supervision system.

Mixtures of 4-carboxypyridinium perchlorate or 4-carboxypyridinium tetrafluoroborate and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) in ethanol and water solution yielded the title supramolecular salts, C6H6NO2+·ClO4−·C12H24O6·2H2O and C6H6NO2+·BF4−·C12H24O6·2H2O. Based on their similar crystal symmetries, unit cells and supramolecular assemblies, the salts are essentially isostructural. The asymmetric unit in each structure includes one protonated isonicotinic acid cation and one crown ether molecule, which together give a [(C6H6NO2)(18-crown-6)]+supramolecular cation. N—H...O hydrogen bonds between the protonated N atoms and a single O atom of each crown ether result in the 4-carboxypyridinium cations `perching' on the 18-crown-6 molecules. Further hydrogen-bonding interactions involving the supramolecular cation and both water molecules form a one-dimensional zigzag chain that propagates along the crystallographiccdirection. O—H...O or O—H...F hydrogen bonds between one of the water molecules and the anions fix the anion positions as pendant upon this chain, without further increasing the dimensionality of the supramolecular network.

The reaction of dimethylamine, 18-crown-6, and perchloric acid in methanol yields the title compound, C2H8N+·ClO4−·C12H24O6·H2O. The dimethylammonium cation and the water molecule interact with the 18-crown-6 unit: N—H...O hydrogen bonds are formed between the ammonium NH2+ group and four O atoms of the crown ether, while the water molecule on the other side of 18-crown-6 ring forms O—H...O hydrogen bonds with two other O atoms of the crown ether. All conventional donors and acceptors in the cations are thus engaged in hydrogen bonding. The ClO4− anion is disordered over two sites, and occupancies for the disordered O atoms were fixed at 0.5. In the crystal, the cations and anions are arranged in alternating layers.

The crystal structure of the title compound, (C6H7FN)2[CuCl4], consists of parallel two-dimensional perovskite-type layers of corner-sharing CuCl6 octahedra. These are bonded together via N—H...Cl hydrogen bonds from the 4-fluoroanilinium chains, which are almost perpendicular to the layers. The CuCl4 dianions have two short Cu—Cl bonds [2.2657 (15) and 2.2884 (13) Å] and two longer bonds [2.8868 (15) Å], giving highly Jahn–Teller-distorted CuCl6 octahedra. The Cu atoms are situated on crystallographic centers of inversion.

The hydrogen-bonding supramolecule with 4-ethoxyanilinium and [18]crown-6 is introduced to [Ni(dmit)2]− salt. The arrangement of supramolecular cations formed a three-dimensional structure with the one-dimensional channel filled with [Ni(dmit)2]− anions. The temperature-dependent structural analyses and DSC measurement disclose the first-order phase transition occurred around 285 K, where the lattice parameters show an abrupt change without a space group change. The title compound crystallizes in No. 1 space group P-1 and is piezoelectrically active with d33 value of 4.8 pC N−1. The frequency- and temperature-dependent dielectric constants and potential energy calculation are consistent with the forward–backward motion of the ethoxyl group in the cation.

The reaction of 1-bromo-methyl-1,4-diazo-niabicyclo-[2.2.2]octane bromide, zinc chloride and hydro-chloric acid in water yields the title compound, (C(7)H(15)BrN(2))[ZnCl(4)]. In the crystal, the components are linked by N-H⋯Cl hydrogen bonds. The Zn(II) atom has an approximately tetra-hedral coordination geometry.

The reaction of dimethylamine hydrochloride, 18-crown-6 and ferric chloride in ethanol yields the title compound, (C2H8N)[FeCl4]·C12H24O6, which exhibits an unusual supramolecular structure. The protonated dimethylamine contains one NH2+ group, resulting in a 1:1 supramolecular rotator–stator structure (CH3—NH2+—CH3)(18-crown-6), through N—H...O hydrogen-bonding interactions between the ammonium group of the cation and the O atoms of the crown ether. In the crystal, all three components lie on a common crystallographic mirror plane normal to [010].

In the title hydrated salt, 2,4,6-triamino-1,3,5-triazin-1-ium perchlorate monohydrate, C3H7N6+·ClO4−·H2O, the constituents are linked via hydrogen bonds of the O—H...O, N—H...O, N—H...N and N—H...Cl types. All the H atoms of the melaminium cation are involved in the hydrogen bonds. The melaminium residues are interconnected by four N—H...N hydrogen bonds, forming chains parallel to (111). The ribbons are interconnected by other hydrogen bonds as well as by π–π interactions [centroid–centroid distance = 3.8097 (7) Å].

In the title melaminium salt, 2,4,6-triamino-1,3,5-triazin-1-ium iodide monohydrate, C3H7N6+·I−·H2O, the components are linked via N—H...O, N—H...N, O—H...I and N—H...I hydrogen bonds. All of the H atoms of the melaminium cation are involved in hydrogen bonds. The melaminium cations are interconnected by four N—H...N hydrogen bonds, forming ribbons along [111]. The water molecules connected by N—H...O hydrogen bonds also form part of these ribbons. The ribbons are interconnected by other hydrogen bonds (O—H...I and N—H...I), as well as by π–π interactions [centroid–centroid distance = 3.6597 (17) Å].

There are two independent molecules in the asymmetric unit of the title compound, C21H21NO2, which was synthesized by the one-pot reaction of 2-naphthol, morpholine and benzaldehyde. The dihedral angles between the naphthalene ring systems and the benzene rings are 84.03 (7) and 75.76 (8)° in the two molecules and an intramolecular O—H...N hydrogen bond occurs in each independent molecule.