Strong electron-accepting methylviologen dication confined in magnetic hosts: synthesis, structural characterization, charge-transfer and magnetic properties of {(MV)2[Ni(SCN)5].Cl.2H2O}n and {(MV)[m(N3)2(SCN)2]}n (M=Mn, Co)

Three hybrid host-guest compounds {(MV)2[Ni(SCN)5].Cl.2H2O}n (1), {(MV)[Mn(N3)2(SCN)2]}n (2) and {(MV)[Co(N3)2(SCN)2}n (3) (where MV2+ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(II) chains connected through S...S interactions. Compounds 2 and 3 are isostructural, containing single micro(1,3)-azide bridged Mn(II)/Co(II) square layers. MV2+, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV2+ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = -34.52(7) cm(-1) for 1, J = -3.90(2) cm(-1) for 2 and J = -10.96(6) cm(-1) for 3).     

Strong electron-acceptor methylviologen dications confined in a 2D inorganic host: synthesis, structural characterization, charge transport and electrochemical properties of (MV)(0.25)V(2)O(5).

The reaction of methylviologen iodide with crystalline V2O5 in the molar ratio of 1 to 3.8 at 100 degrees C in water led to the formation of (MV)0.25V2O5 in quantitative yield. The structure of this organic-inorganic multilayered hybrid compound was determined by single-crystal X-ray crystallography. Strong van der Waals interactions were found between the electron-deficient aromatic organic molecules and the inorganic layers. In the solid state, the compound is a semiconductor due to small polaron hopping and shows novel reversible alkali-ion intercalation/deintercalation via electrochemistry.     

Ferroelectric behavior and structural change of poly(trimethylene terephthalate) induced by external electric field

The ferroelectric behavior and structural change induced by the external electric field were observed for poly(trimethylene terephthalate) (PTT), which has nonpolar crystalline structure with carbonyl groups aligned antiparallel to each other. The displacement‐electric field hysteresis curves of PTT films showed hysteresis above 140 °C, which indicated the polarization reversal of PTT. The pyroelectric constant and thermally stimulated depolarization current suggest the depolarization of the polar structure of PTT induced by the external electric field above 150 °C. An endothermic peak caused by the depolarization was also observed in the differential scanning calorimetry for the PTT film poled at 30 MV/m. The change of the crystalline structure and the orientation of carbonyl groups induced by the electric filed were investigated by X‐ray diffraction patterns and infrared spectra. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1991–1996, 2009     

Two acentric mononuclear molecular complexes with unusual magnetic and ferroelectric properties

Two acentric, i.e., noncentrosymmetric, mononuclear complexes, Co(5-ATZ)(4)Cl(2), 1, and Cu(5-ATZ)(4)Cl(2), 2, where 5-ATZ is the monodentate 5-amino-1-H-tetrazole ligand, have been prepared and characterized. Both complexes crystallize in the tetragonal system with the P4nc space group, a member of the polar noncentrosymmetric 4mm class, and thus both 1 and 2 can exhibit ferroelectric and nonlinear optical properties. Magnetic studies indicate that 1 is a paramagnetic high-spin cobalt(II) complex with a rather extensive spin-orbit coupling, modeled as a zero-field splitting parameter, D, of ±91(3) cm(-1) and with very weak long-range antiferromagnetic exchange interactions. Direct current (dc) and ac magnetic studies indicate that 2 is a paramagnetic copper(II) complex that exhibits weak ferromagnetic exchange interactions below 15 K. Both 1 and 2 exhibit ferroelectric hysteresis loops at room temperature with remanent polarizations of 0.015 μC/cm(2) and coercive electric fields of 5.5 and 5.7 kV/cm, respectively.     

Improved multiferroic in EuTiO3 films by interphase strain engineering

Interphase strain engineering provides a unique methodology to significantly modify the lattice structure across a single film, enabling the emergence and manipulation of novel functionalities that are inaccessible in the context of traditional strain engineering methods. In this work, by using the interphase strain, we achieve a ferromagnetic state with enhanced Curie temperature and a room-temperature polar state in EuO secondary phase-tunned EuTiO₃ thin films. A combination of atomic-scale electron microscopy and synchrotron X-ray spectroscopy unravels the underlying mechanisms of the ferroelectric and ferromagnetic properties enhancement. Wherein, the EuO secondary phase is found to be able to dramatically distort the TiO₆ octahedra, which favors the non-centrosymmetric polar state, weakens antiferromagnetic Eu-Ti-Eu interactions, and enhances ferromagnetic Eu-O-Eu interactions. Our work demonstrates the feasibility and effectiveness of interphase strain engineering in simultaneously promoting ferroelectric and ferromagnetic performance, which would provide new thinking on the property regulation of numerous strongly correlated functional materials.     

Photosensitized production of doubly reduced methylviologen followed by highly efficient methylviologen radical formation using self-assembling ruthenium(II) complexes

Supramolecular fibers of Ru(II) complexes act as efficient photosensitizers, photochemically generating methylviologen radical (MV.+) and then converting it quantitatively to doubly reduced methylviologen, (MV0), in the presence of triethanolamine.     

Li0.025Na0.975NbO3低温铁电相变及晶体结构

Li_(0.025)Na_(0.975)NbO_3 undergoes a ferroelectric-ferroelectric phase transition at 180K (on cooling) or 260 K (on heating). The structure determinations of both phases have been carried out by single crystal diffraction analysis. The ferroelectric room-temperature phase is orthorhombic, with space group Pc2_1b; the cell parameters are a=0.5508(3), b=1.5521(6), c=0.5568(2) nm. The structure is same with Li_(0.02)Na_(0.98)NbO_3. The ferroelectric low-temperature phase is also orthorhomhie, a=0.5497(7), b=0.7913(18), c=0.5565(10) nm, V=0.2421 nm, Z=4. There is disordernal position distribution of O(2) atomes in the low-temperature phase. Its “apparent space group” is P2/n2/n2/n. The relation of the ferroelectric properties to the low-temperature phase structure is discussed.     

Near unity quantum yield of light-driven redox mediator reduction and efficient H2 generation using colloidal nanorod heterostructures

The advancement of direct solar-to-fuel conversion technologies requires the development of efficient catalysts as well as efficient materials and novel approaches for light harvesting and charge separation. We report a novel system for unprecedentedly efficient (with near-unity quantum yield) light-driven reduction of methylviologen (MV(2+)), a common redox mediator, using colloidal quasi-type II CdSe/CdS dot-in-rod nanorods as a light absorber and charge separator and mercaptopropionic acid as a sacrificial electron donor. In the presence of Pt nanoparticles, this system can efficiently convert sunlight into H(2), providing a versatile redox mediator-based approach for solar-to-fuel conversion. Compared to related CdSe seed and CdSe/CdS core/shell quantum dots and CdS nanorods, the quantum yields are significantly higher in the CdSe/CdS dot-in-rod structures. Comparison of charge separation, recombination and hole filling rates in these complexes showed that the dot-in-rod structure enables ultrafast electron transfer to methylviologen, fast hole removal by sacrificial electron donor and slow charge recombination, leading to the high quantum yield for MV(2+) photoreduction. Our finding demonstrates that by controlling the composition, size and shape of quantum-confined nanoheterostructures, the electron and hole wave functions can be tailored to produce efficient light harvesting and charge separation materials.     

Electrocatalytic Oxidation of Coenzyme NADH at Carbon Paste Electrodes, Modified with Zirconium Phosphate and Some Redox Mediators

Carbon paste electrodes (CPE), modified with zirconium phosphate (ZrP) along with some redox mediators, were prepared and shown to be active in electrocatalytic oxidation of coenzyme NADH. Nile blue (NB), methylviologen (MV), and benzylviologen (BV) were added to ZrP-containing CPE, showing a shift of their redox potentials toward the positive direction, ranging from ca. 0.20 to 0.35 V. This shift was interpreted in terms of different complexation abilities of oxidized and reduced forms of mediators with the host matrix. The modified electrodes prepared showed electrocatalytic activity for electrooxidation of NADH. The i,c-dependencies for the modified electrodes were shown to follow Michaelis-Menten kinetics. For C:ZrP:NB and C:ZrP:MV electrodes, Michaelis constants of 0.870 +/- 0.012 and 0.153 +/- 0.015 mM, respectively, were obtained. The sensitivity of C:ZrP:NB and C:ZrP:MV electrodes to NADH varied from 19.2 to 60.8 and from 18.4 to 50.9 μA/mM c cm(2), respectively, by changing the working potential from -0.2 to 0.2 V vs. SCE. Copyright 2000 Academic Press.     

High breakdown strength and low loss binary polymer blends of poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) and poly(methyl methacrylate)

Dielectric materials with high breakdown strength and low loss are of crucial importance in capacitive energy storage electronics. Herein, a kind of polymer blend composed of poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) ferroelectric terpolymer and linear dielectric poly(methyl methacrylate) (PMMA) is presented. The polymer blend shows a breakdown strength of 733 MV/m and a charge‐discharge efficiency over 90% at 200 MV/m with optimized PMMA content, which are 101% and 28% higher than that of neat terpolymer. Moreover, microsecond discharge time of 2.26 μs, along with a power density that is 3.6 times that of the current commercially available biaxially oriented polypropylene, as well as great cyclic performance, has been achieved under an electric field of 200 MV/m. The findings of this research demonstrate that the incorporation of linear dielectric PMMA into poly(vinylidene fluoride)‐based ferroelectric polymer provides a new strategy in designing high breakdown strength low loss dielectric materials for reliable compact flexible film capacitors.     

Improving ferro- and piezo- electric properties of hydrogenized poly(vinylidene fluoride-trifluoroethylene) films by annealing at elevated temperatures

After annealing the solution cast P(VDF-TrFE) films at elevated temperatures, which were synthesized via a full hydrogenation process from P(VDF-CTFE) with a composition of VDF/TrFE = 80/20(mol%), a series of P(VDF-TrFE) films were fabricated in present work. The crystalline and ferroelectric phases of the films were carefully characterized and their dielectric, ferroelectric and piezoelectric properties were systematically investigated. The improved crystalline and ferroelectric phases in the films induced by annealing at elevated temperatures are responsible for the significant improved electric properties of the films. The optimized annealing temperature is found to be 130 °C and the best performance including the highest dielectric constant of 12.5 at 1 kHz, the largest maximum polarization of 11.21 μC/cm~2 and remnant polarization of 7.22 μC/cm~2, the lowest coercive electric field of 56 MV/m, and the highest piezoelectric coefficient of -25 pC/N is observed.     

A mixed-valence coordination polymer featuring two-dimensional ferroelectric order: {[Cu(I)4Cu(II)(Et2dtc)2Cl3][Cu(II)(Et2dtc)2]2(FeCl4)}n (Et2dtc- = diethyldithiocarbamate)

The first mixed-valence coordination polymer indicating ferroelectric properties, {[CuI4CuII(Et2dtc)2Cl3][CuII(Et2dtc)2]2(FeCl4)}n (Et2dtc- = diethyldithiocarbamate), has been synthesized and crystallographically characterized. This complex has a two-dimensional infinite square lattice structure, including both Cu(I) and Cu(II) ions, which is confirmed by XPS and SQUID measurements. In addition, the ferroelectric behaviors are revealed by the dielectric measurements with a LCR meter and a ferroelectric tester.     

From Packed “Sandwich” to “Russian Doll”: Assembly by Charge‐Transfer Interactions in Cucurbit[10]uril

As the host possessing the largest cavity in the cucurbit[n]uril (CB[n]) family, CB[10] has previously displayed unusual recognition and assembly properties with guests but much remains to be explored. Herein, we present the recognition properties of CB[10] toward a series of bipyridinium guests including the tetracationic cyclophane known as blue box along with electron‐rich guests and detail the influence of encapsulation on the charge‐transfer interactions between guests. For the mono‐bipyridinium guest (methylviologen, MV ²⁺), CB[10] not only forms 1:1 and 1:2 inclusion complexes, but also enhances the charge‐transfer interactions between methylviologen and dihydroxynaphthalene ( HN ) by mainly forming the 1:2:1 packed “sandwich” complex (CB[10] ? 2 MV ²⁺ ?HN ). For guest 1 with two bipyridinium units, an interesting conformational switching from linear to “U” shape is observed by adding catechol to the solution of CB[10] and the guest. For the tetracationic cyclophane‐blue box, CB[10] forms a stable 1:1 inclusion complex; the two bipyridinium units tilt inside the cavity of CB[10] according to the X‐ray crystal structure. Finally, a supramolecular “Russian doll” was built up by threading a guest through the cavities of both blue box and CB[10].     

Crystal structures and spectroscopic properties of polycyano-polycadmate host clathrates including a CT complex guest of methylviologen dication and aromatic donor

A series of polycyano-polycadmate (PCPC) host clathrates including a CT complex of methylviologen dication (MV2+) and an aromatic donor as a guest were synthesized, and their crystal structures and spectroscopic properties were investigated. The PCPC host has a framework structure built with Cd2+ ions as coordination centres and cyanides as bridging ligands. This framework host has negative charge and includes a cationic guest together with an ordinary neutral guest. MV2+, which is a strong acceptor, was included as a cationic guest and an aromatic compound, which works as a donor, was included as a neutral guest. Crystal structures of seven clathrates, whose neutral guests were o-cresol, m-cresol, p-cresol, 1-methylnaphthalene, 1,2,4-trimethoxybenzene, pyrrole and aniline, were determined by single crystal X-ray diffraction methods. In all cases MV2+ and the neutral guest formed a CT complex with a face to face stacking structure and were included as a CT complex guest. However, depending on each clathrate the ratio of aromatic donor to MV2+ was different and several variations were found in their PCPC host structures. The clathrates had their own colour depending on their neutral guest. The plot of the CT transition energies estimated from optical CT bands against the ionization potentials of the neutral guests satisfied a linear relationship predicted by Mulliken theory. However, the CT transition energies observed in the clathrates showed a shift to lower energy by ca. 0.6 eV compared with those observed in corresponding acetonitrile solutions.     

一种基于碘化铅的有机/无机杂化钙钛矿材料传输性能的研究

合成了一种新型的有机/无机杂化钙钛矿(NH3C6H4OC6H4NH3)PbI4, 采用元素分析、紫外-可见光吸收光谱、X射线衍射和透射电镜对其结构进行了表征, 结果表明这种材料具有规则的层状结构, 有序性高. 对这种材料的薄膜进行了伏安测试, 结果表明该材料属于n型半导体, 其电子迁移率达到0.065 cm2•V－1•s－1, 在光电器件领域有着潜在的应用前景.     

Effects of steric constraint on chromium(III) complexes of tetraazamacrocycles. Chemistry and excited-state behavior of 1,4-C2-cyclam complexes

The synthesis and characterization of several Cr(III) complexes of the constrained macrocyclic ligand 1,4-C(2)-cyclam = 1,4,8,11-tetraazabicyclo[10.2.2]hexadecane is reported. The ligand appears to form only trans complexes, and the structure of trans-[Cr(1,4-C(2)-cyclam)Cl(2)]PF(6) is presented. The constraint imposed by the additional C(2) linkage distorts the bond angles significantly away from the ideal values of 90 and 180 degrees. The effect of the distortion is to enhance the aquation rate of trans-[Cr(1,4-C(2)-cyclam)Cl(2)](+) (k(obs) for trans-[Cr(1,4-C(2)-cyclam)(H(2)O)(2)](3+) formation = 6.5 x 10(-)(2) s(-)(1), 0.01M HNO(3), 25 degrees C) by over 5 orders of magnitude relative to trans-[Cr(cyclam)Cl(2)](+). The complexes trans-[Cr(1,4-C(2)-cyclam)Cl(2)](+) and trans-[Cr(1,4-C(2)-cyclam)(CN)(2)](+) are found to have extinction coefficients four to five times higher than their cyclam analogues, owed to the lack of centrosymmetry caused by the steric constraint. The trans-[Cr(1,4-C(2)-cyclam)(CN)(2)](+) complex is a very weak emitter in aqueous solution with a broad room-temperature emission centered at 735 nm (tau = 0.24 micros). Extended photolysis (350 nm, 15 h) of trans-[Cr(1,4-C(2)-cyclam)(CN)(2)](+) in aqueous solution results in CN(-) ligand loss. This is in stark contrast to its unconstrained cyclam analogue, which is photoinert and has a room-temperature emission lifetime of 335 micros.     

Exploring a Lead‐free Semiconducting Hybrid Ferroelectric with a Zero‐Dimensional Perovskite‐like Structure

Perovskite lead halides (CH₃NH₃PbI₃) have recently taken a promising position in photovoltaics and optoelectronics because of remarkable semiconducting properties and possible ferroelectricity. However, the potential toxicity of lead arouses great environmental concern for widespread application. A new chemically tailored lead‐free semiconducting hybrid ferroelectric is reported, N‐methylpyrrolidinium)₃Sb₂Br₉ ( 1 ), which consists of a zero‐dimensional (0‐D) perovskite‐like anionic framework connected by corner‐ sharing SbBr₆ coordinated octahedra. It presents a large ferroelectric spontaneous polarization of approximately 7.6 μC cm^?2, as well as notable semiconducting properties, including positive temperature‐dependent conductivity and ultraviolet‐sensitive photoconductivity. Theoretical analysis of electronic structure and energy gap discloses a dominant contribution of the 0‐D perovskite‐like structure to the semiconducting properties of the material. This finding throws light on the rational design of new perovskite‐like hybrids, especially lead‐free semiconducting ferroelectrics.     

Salt-inclusion synthesis of two new polar solids, Ba6Mn4Si12O34Cl3 and Ba6Fe5Si11O34Cl3

A new family of salt-containing, mixed-metal silicates (CU-14), Ba6Mn4Si12O34Cl3 (1) and Ba6Fe5Si11O34Cl3 (2), was synthesized via the BaCl2 salt-inclusion reaction. These compounds crystallize in the noncentrosymmetric (NCS) space group Pmc2(1) (No. 26), adopting 1 of the 10 NCS polar, nonchiral crystal classes, mm2 (C2v). The cell dimensions are a = 6.821(1) A, b = 9.620(2) A, c = 13.172(3) A, and V = 864.4(3) A3 for 1 and a = 6.878(1) A, b = 9.664(2) A, c = 13.098(3) A, and V = 870.6(3) A3 for 2. The structures form a composite framework made of the (M(4+x)Si(12-x)O34)9- (M = Mn, x = 0; M = Fe, x = 1) covalent oxide and (Ba6Cl3)9+ ionic chloride sublattices. The covalent framework exhibits a pseudo-one-dimensional channel where the extended barium chloride lattice (Ba3Cl1.5)(infinity) resides, and it consists of fused eight-membered meta-silicate rings propagating along [100] via sharing two opposite [Si2O7]6- units to form an acentric lattice. Single-crystal structure studies also reveal the ClBa4 unit adopting an interesting seesaw configuration, in which the lone pair electrons of chlorine preferentially face the oxide anions of the transition metal silicate channel, thus forming the observed polar frameworks. Similar to the synthesis of organic-inorganic hybrid materials, the salt-inclusion method facilitates a promising approach for the directed synthesis of special framework solids, including NCS compounds, via composite lattices.     

Structure and physical properties of the polar oxysulfide CaZnOS

The synthesis, structure, and electrical properties of the oxysulfide CaZnOS are reported. The white compound has a band gap of 3.7(1) eV and crystallizes in hexagonal space group P6(3)mc (No. 186) with a = 3.75726(3) A, c = 11.4013(1) A, and Z = 2. The noncentrosymmetric structure, which has few analogues, is composed of isotypic puckered hexagonal ZnS and CaO layers arranged so that ZnS3O tetrahedra are all aligned parallel, resulting in a polar structure. The compound shows type 1 non-phase-matchable second harmonic generation, determined using 1064 nm radiation, with an efficiency approximately 100 times that of alpha-SiO2 and a piezoelectric coefficient of 38 pm V-1. Although polar, CaZnOS is not ferroelectric and the pyroelectric coefficient is very small, approximately 0.0 microC m-2 K-1 between room temperature and 100 degrees C.     

Room-Temperature Ferroelectric Material Composed of a Two-Dimensional Metal Halide Double Perovskite for X-ray Detection

Although two-dimensional (2D) metal–halide double perovskites display versatile physical properties due to their huge structural compatibility, room-temperature ferroelectric behavior has not yet been reported for this fascinating family. Here, we designed a room-temperature ferroelectric material composed of 2D halide double perovskites, (chloropropylammonium)₄AgBiBr₈, using an organic asymmetric dipolar ligand. It exhibits concrete ferroelectricity, including a Curie temperature of 305 K and a notable spontaneous polarization of ≈3.2 μC cm⁻², triggered by dynamic ordering of the organic cation and the tilting motion of heterometallic AgBr₆/BiBr₆ octahedra. Besides, the alternating array of inorganic perovskite sheets and organic cations endows large mobility-lifetime product (μτ=1.0×10⁻³ cm² V⁻¹) for detecting X-ray photons, which is almost tenfold higher than that of CH₃NH₃PbI₃ wafers. As far as we know, this is the first study on an X-ray-sensitive ferroelectric material composed of 2D halide double perovskites. Our findings afford a promising platform for exploring new ferroelectric materials toward further device applications.