Single-crystal Powder Research Articles

Electronic Structure and Chemical Bonding in Methylammonium Lead Triiodide and Its Precursor Methylammonium Iodide.

A detailed examination of the electronic structures of methylammonium lead triiodide (MAPI) and methylammonium iodide (MAI) is performed with ab initio molecular dynamics (AIMD) simulations based on density functional theory, and the theoretical results are compared to experimental probes. The occupied valence bands of a MAPI single crystal and MAI powder are probed with X-ray photoelectron spectroscopy, and the conduction bands are probed from the perspective of nitrogen K-edge X-ray absorption spectroscopy. Combined, the theoretical simulations and the two experimental techniques allow for a dissection of the electronic structure unveiling the nature of chemical bonding in MAPI and MAI. Here, we show that the difference in band gap between MAPI and MAI is caused chiefly by interactions between iodine and lead but also weaker interactions with the MA+ counterions. Spatial decomposition of the iodine p levels allows for analysis of Pb-I σ bonds and π interactions, which contribute to this effect with the involvement of the Pb 6p levels. Differences in hydrogen bonding between the two materials, seen in the AIMD simulations, are reflected in nitrogen valence orbital composition and in nitrogen K-edge X-ray absorption spectra.

A singular paramagnetic susceptibility peak in a WSe2/MoSe2 chemical bonding structure

The magnetic characteristics of 1:1 WSe2 and MoSe2 mixed single crystal powder with and without thermal annealing process were studied. Scanning electron microscopy images and Raman spectroscopy support that the WSe2 and MoSe2 are chemically bound at the WSe2 and MoSe2 boundary after the thermal annealing process. Our sample also exhibits the hysteresis loop and splitting of magnetic moment at zero field cooling and field cooling precesses in the chemically bound system. In contrast, all these characteristics are not detected in the unannealed mixed WSe2 and MoSe2 crystal powder. Temperature independent singular paramagnetic peaks are only detected in the WSe2 and MoSe2 mixed single crystal powder with thermal annealing. These results support that the temperature independent singular paramagnetic susceptibility peaks should originate from the intrinsic lattice mismatch induced ferromagnetism.

Two substituted tetrazole-based isomers of [M2(PPT)(OH)(SO4)(H2O)]n (M = Zn, Cd): The in-situ syntheses and characterization

Two new isotypic substituted tetrazolates of d10 metals, [M2(PPT)(OH)(SO4)(H2O)]n, (M = Zn, 1 and Cd, 2) (PPT = 5-(4-pyridylphenyl)tetrazole) have been in-situ synthesized using the metal sulfates, 4-(4-pyridyl)benzonitrile (PBN) and sodium azide under mild solvothermal conditions. The prepared materials have been characterized by single crystal X-ray diffraction, powder XRD, elemental analyses, IR & Raman spectroscopy, SEM-EDS, solid state fluorescence, and TG analyses. The PPT ligand in both compounds is generated via the in situ [2 + 3] cycloaddition in the reaction of the cyano groups of the organonitrile and sodium azide. Single crystal X-ray diffraction reveals both materials possess 3D framework of six-coordinated metal polyhedrons that are further connected by the PPT linkers. The BV calculation confirms the existence of extremely long ZnO bond distance of 2.663 Å in compound 1. In addition, the solid-state photoluminescence indicates the cadmium-based material has a more intensive photoluminescent emission than the zinc one upon excitation at room temperature.

Transition of vortex pinning behaviour induced by an artificial microstructure design in Ba(Fe0.94Co0.06)2As2 pnictide superconductor

Among various systems of iron-based superconductors, the doped Ba122 polycrystals have shown the largest application value because of their brilliant properties and chemical stability. Since there have been few reports on the vortex dynamics in Ba122 polycrystal, we firstly conduct a comparative investigation on the differences of vortex dynamics in Ba(Fe0.94Co0.06)2As2 single crystal, grain oriented polycrystal and random oriented powder in this paper. Herein, the polycrystal, which has c-axis grain texture, is prepared by the compaction of designed single crystal powder. The second magnetization peak (SMP) effects are observed in the hysteresis loops of single crystal and totally disappear in those of polycrystal and powder. Conventional magnetization relaxation and Maley's method are applied to analyse the vortex dynamics. In single crystal, the SMP effect is primarily related to the crossover of elastic-plastic vortex creep. The weak pinning in single vortex regime results in large magnetization relaxation rates (S) in low magnetic field regime. In polycrystal for H//AD (axial direction), the introduction of strong pins is effective to single vortex pinning, which brings about much lower S values in low magnetic field regime. Furthermore, the results of single crystal for H//ab, polycrystal for H//RD (radial direction) and random oriented powder are analyzed. Synergistic effects of strong pins and microscopic anisotropy on the vortex dynamics are discussed. These results will provide new knowledge for the design of high-performance Ba122 superconductors.

A Mn-based LMOF with an AIEgens ligand for selective detection of Fe3+, CrO42− and Cr2O72− ions in aqueous solution

A novel multifunctional chemical sensor Mn-based LMOF, namely, [Mn(tipe)4(ndc)Cl]n(LMOF-1) was solvothermally synthesized by introducing an aggregation-induced emission luminogens (AIEgens) ligand, 1,1,2,2-tetrakis(4-(1H -imidazole-1-yl)-phenyl)ethane, and analyzed by single crystal X-ray diffraction, thermogravimetric and powder X-ray diffraction and other methods. The analysis of the structure showed that LMOF-1 crystallized in a monoclinic system, P21/n space group. LMOF-1 has high stability and strong luminescence properties in solutions. The sensing experiments testify that it can be used as a selectively multifunctional sensor for Fe3+, CrO42− and Cr2O72−, with high quenching coefficient (Ksv) values at 11924 ​M−1, 16078 ​M−1 and 18744 ​M−1, respectively. Noticeably, there found that the Ksv value of Cr2O72− was the highest among published literature.

Effect of Charge Transfer and Non-Covalent Interactions of the Synthesized NLO Compound p-Nitrophenol Sodium-Bisulfate Using DFT Method

In the present work a new semiorganic single crystal p-nitrophenol sodium-bisulfate (PNSB) was synthesized and fully characterized by means of single crystal XRD, powder XRD, FT-IR, FT-Raman and UV-visible spectroscopic techniques. The optimized geometrical parameters were obtained at the DFT/B3LYP level of theory and correlate them with similar structures. Normal coordinate analysis, force constants, and potential energy distributions have been used to support the complete vibrational assignments for all vibrational modes. The computed IR and Raman frequencies correlate well with the experiments, as indicated by the correlation factor. The optimized molecular structure reveals the presence of C-H…O hydrogen bonding interaction. The stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bonding orbital analysis. NBO analysis proved the presence of intermolecular O-H…Na22 hydrogen bonds caused by the interaction of the lone pair of oxygen with the anti-bonding orbital. HOMO, LUMO and ESP analyses were done using DFT, whereas, the absorption band in the UV–vis spectrum was predicted and compared with the experimental data. ESP is used to identify the nucleophilic region, which is located around the sodium atom, and the electrophilic region, which is primarily located at the oxygen atoms of the PNSB molecule. The frontier orbital gap denotes the charge transfer interaction within the compound required for optical activity. Electron Localization Function, Localized Orbital Locator and Reduced Density Gradient analysis were discussed. In order to study the nonlinear optical activity of PNSB, the dipole moment, polarizability and fihyperpolarizabilities were computed. It is found that the calculated first order hyperpolarizability of PNSB is 51.75 times greater than that of urea.

Effects of manganese substitution on magnetic and magnetostrictive properties of Tb0.5Dy0.5(Fe1–xMnx)1.92/epoxy composites with spherical single-crystal particles

Spherical Tb0.5Dy0.5(Fe1–xMnx)1.92 (x = 0, 0.05, 0.10 and 0.15) single-crystal particles were prepared. The magnetic anisotropy of the alloy decreases as x increases from 0 to 0.15. Subsequently, we prepared giant magnetostrictive composites with these spherical Tb0.5Dy0.5(Fe1–xMnx)1.92 single-crystal particles. As a consequence, well <111>-oriented Tb0.5Dy0.5(Fe1–xMnx)1.92 composites with 55 vol% Tb0.5Dy0.5(Fe1–xMnx)1.92 particles were obtained. The Tb0.5Dy0.5(Fe0.9Mn0.1)2 composite manifests a good low-field magnetostrictive property and saturation magnetostriction at an axial pressure of 10 MPa, λ||, saturation ≈ 2100 ppm, which is larger than that of the commercially available Terfenol-D (1400–1800 ppm). The preparation of composites with single crystal spherical powders may be an effective solution of developing high-performance magnetostrictive composites.

Large steric hindrance amide modified benzothiadiazole: High contrast mechanochromic luminescence and volatile acid vapor response

Three mechanochromic luminescent (MCL) materials were obtained by modifying the 5, 6 and 4, 7 positions of benzothiadiazole (BTD) with two sterically hindered amides and two aromatic groups, respectively. The Stokes shifts of the compounds were larger in different solvents (>6000 cm−1), especially 3c in dimethyl sulfoxide up to 8900 cm−1. Upon response to mechanical force, the fluorescence of 3c had high contrast (75 nm) before and after milling, and the emission changed from bright yellow light (533 nm) to orange-red light (608 nm). Meanwhile, strong fluorescence emission intensities were observed before and after grinding (quantum yield: 56%, 46% respectively). The MCL reasons of the compounds were explained in detail by theoretical calculation, single crystal X-ray diffraction (XRD), powder XRD and differential scanning calorimetry (DSC) analysis. In addition, the MCL materials also showed fluorescence responsiveness to the vapor of volatile acids.

Phenothiazine metal-organic framework materials with excellent third-order nonlinear properties

The third-order nonlinear optical material with excellent performance is a molecule with a large π-conjugated structure for absorption structure and a high degree of delocalization. Nitrogen-sulfur derivatives have lone pairs of electrons in their N and S atoms, which makes them have a strong intramolecular charge transfer ability, which is conducive to the formation of donor-acceptor molecules. In this paper, phenothiazine is used as the matrix structure of the third-order nonlinear optical material, modified, and then metal coordination is performed to obtain [Zn(Py)2Cl2]n and [Cd(Py)2Cl2]n. Its structure is characterized by infrared spectroscopy, single crystal X-ray diffraction and powder X-ray diffraction. The morphology of the material was characterized by scanning electron microscopy. The photophysical properties, thermal properties and third-order nonlinear properties were tested, and the theoretical verification was carried out with the DFT calculation method, and the relationship between the structure and the third-order nonlinear properties was summarized. The experimental results show that phenothiazine has good electron donating ability, the two-photon absorption coefficient β is between 1.334–38.400 × 10−10 m/W, and the third-order nonlinear polarizability χ(3) is between 2.752–79.247 × 10−11 esu, The second-order hyperpolarizability γ of the ligand molecule is 5.213 × 10−34 esu. The χ(3) values of [Zn(Py)2Cl2]n and [Cd(Py)2Cl2]n are 4 orders of magnitude higher than ordinary α-quartz (χ(3) = 2.6 × 10−14 esu).

Molten Chlorides as the Precursors to Modify the Ionic Composition and Properties of LiNbO3 Single Crystal and Fine Powders.

Modifying lithium niobate cation composition improves not only the functional properties of the acousto- and optoelectronic materials as well as ferroelectrics but elevates the protonic transfer in LiNbO3-based electrolytes of the solid oxide electrochemical devices. Molten chlorides and other thermally stable salts are not considered practically as the precursors to synthesize and modify oxide compounds. This article presents and discusses the results of an experimental study of the full or partial heterovalent substitution of lithium ion in nanosized LiNbO3 powders and in the surface layer of LiNbO3 single crystal using molten salt mixtures containing calcium, lead, and rare-earth metals (REM) chlorides as the precursors. The special features of heterovalent ion exchange in chloride melts are revealed such as hetero-epitaxial cation exchange at the interface PbCl2-containing melt/lithium niobate single crystal; the formation of solid solutions with cation vacancies as an intermediate product of the reaction of heterovalent substitution of lithium ion by calcium in LiNbO3 powders; the formation of lanthanide orthoniobates with a tetragonal crystal structure such as scheelite as the result of lithium niobate interaction with trichlorides of rare-earth elements. It is shown that the fundamental properties of ion-modifiers (ion radius, nominal charge), temperature, and duration of isothermal treatment determine the products’ chemical composition and the rate of heterovalent substitution of Li+-ion in lithium niobate.

Growth, spectral, NLO, hardness, Hirshfeld and antibacterial activity studies of melaminium cyanoacetate monohydrate crystals

Using double distilled water as the solvent, a crystal of melaminium cyanoacetate monohydrate (MCAM) was grown through the solution technique. The sample's structure, density, and space group have been determined using single crystal XRD and powder XRD analysis. Vickers microhardness testing was used to determine the hardness, work hardening coefficient, yield strength, and stiffness constant of MCAM crystal. TG/DTA study is was carried out to find the thermal stability and water of crystallization. The transmittance and absorbance behaviour of the sample has been tested by UV-visible spectral studies, and Tauc's plot has been analyzed. FTIR analysis has been used to determine the chemical groups present in the grown crystal. Second-order and third-order NLO effects of the sample have been studied, and it reveals that MCAM crystal has only odd-order NLO effects like third-harmonic generation. The elemental composition and photoluminescence behaviour of the sample has been analyzed. The LDT value of MCAM crystal was found by using Nd: YAG laser. Also Hirshfeld surface and antibacterial activity analyses for the sample have been carried out.

All-visible-light triggered photochromic fluorescent dithienylethene-phenanthroimidazole dyads: Synthesis, crystal structure, multiple switching behavior and information storage

A novel all-visible-light controlled photochromic dithienylethene (DTE) derivatives bearing phenanthroimidazole (PI) unit were synthesized (DTE-PI). Upon alternating irradiation with 420/540 nm light, effective photochromic and fluorescent switches were demonstrated in solution, PMMA film, single crystal and solid powder. Remarkably, multi-stimuli responsive chromism and fluorescence switches were demonstrated by modulation of protonation. The effect of adding trifluoroacetic acid (TFA) on the performance of DTE-PI were carefully investigated. Interestingly, multi-stimuli responsive chromism and fluorescent switches were achieved with good reversibility when treated with excessive TFA. Neutralization by triethylamine (TEA) could restore it to the initial state. Notably, the photoswitchable dual-mode patterning application was developed successfully.

Syntheses of tetrahedral imidazolate frameworks with auxiliary ligand in DMSO

In our former work, we developed one kind of new tetrahedral imidazolate frameworks (TIF-Ax) by adding auxiliary uninegative linker into the zinc-imidazolate assembly in amide. Herein, a series of new compounds (TIF-A4 to TIF-A8) were obtained from imidazolate derivatives and Zinc acetate (acetate as auxiliary ligands) in dimethyl sulfoxide (DMSO). Among them, Zn centers were coordinated by imidazolate derivatives to form 1D chain, differently, TIF-A4 exhibited 3D framework with dia topology and TIF-A5 to TIF-A8 were 4-connected layer with sql topology. These results suggested that DMSO was a good solvent for the syntheses of new TIF-Ax. These compounds were characterized by single crystal XRD, powder XRD, FTIR and TG. In addition, the fluorescence of them were also tested.

Metal and bis(pyridyl)-bis(amide) ligands – tuned three new nickel(II)/copper(II) coordination polymers: Syntheses, structures and properties

Three new Ni(II)/Cu(II) coordination polymers (CPs), [Ni(L1)1.5(HBTC)(H2O)] (1), [Ni(L2)2(HBTC)]·2H2O (2) and [Cu2(L2)0.5(BTC)(μ3-OH)]·2H2O (3) {H3BTC = benzene-1,3,5-tricarboxylic acid, L1 = (E)-4,4′-(ethene-1,2-diyl)bis[N-(pyridin-3-yl)benzamide] and L2 = (E)-4,4′-(diazene-1,2-diyl)bis[N-(pyridin-3-yl)benzamide]}, were prepared under hydrothermal and solvothermal conditions by regulating different metals and ligands. The structures of CPs 1–3 were characterized by single crystal X-ray diffraction analyses, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). CP1 displays a 4-connected 3D topological structure based on [Ni(HBTC)]n chains and [Ni(L1)1.5]n chains. When L2 was used, CP2 demonstrates a 1D chain structure. CP3 is a 3D metal–organic network with the binodal (3,8)-connected {4·62}2{42·622·7·83} topology constructed from {Cu4} clusters and L2 ligands. The photocatalytic properties and electrochemical behaviors of CPs 1–3 were explored. The effect of solvent on the formation of the title CPs as well as the influence of the central metals and ligands on the structures and properties are discussed.

Charge transfer and hydrogen bonding motifs in organic cocrystals derived from aromatic diamines and TCNB

Herein, we have successfully fabricated two Charge transfer (CT) cocrystals 1 and 2 using 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor with aromatic diamine (o-phenylenediamine and benzidine) as hydrogen bond (H-bonds) donor compounds. These binary compounds were characterized comprehensively by Single Crystal X-ray diffraction (SCXRD), powder diffraction, thermal, and spectroscopic analysis (Infrared and UV–vis spectroscopy) in the solid state. CT π···π interactions help to achieve the binary (1:1) mixed staking (DADA) supramolecular self-assembly while the dominant N−H··N and C−H··N H-bonds are exclusively involved in accomplishing the 2D structure as evidenced by the single-crystal analysis in these two cocrystals. Owing to the strong absorption in the near-infrared region (NIR) these materials appear black by virtue of charge transfer which is a fascinating phenomenon in TCNB based complexes. Not to mention, Hirshfeld surface analyses and density functional theory (DFT) were performed to assess the contribution of different intermolecular interactions and HOMO-LUMO energy levels. The present study will help to expand the understanding of non-covalent interactions in these hybrid materials which may further expand the library of functional materials that can find fascinating applications in the future.

A helix-based cobalt(II) coordination polymer with mixed ligands of homophthalic acid and 2,5-Bis(4′-pyridyl)-1,3,4-oxadiazole: synthesis, structure and magnetic property

A novel Cobalt(II) coordination polymer formulated as [Co(hmph)(4-bpo)(H2O)]n (1) was obtained through hydrothermal method, and then characterized by single-crystal X-ray diffraction, elemental analysis and powder X-ray diffraction (H2hmph = homophthalic acid, 4-bpo = 2,5-bis(4′-pyridyl)-1,3,4-oxadiazole). Complex 1 displays a three-dimensional architecture based on interweaving helix chains, which can be defined as a 4-connected uoc network with the Schläfli symbol of (42.84). TGA experiment reveals that complex 1 can maintain its integrity until 214 °C. Furthermore, the magnetic data indicate there is weak antiferromagnetic interaction between the neighbor Co(II) atoms in the metal-carboxylate chain.

Linear coefficient of thermal expansion and Debye temperature of PbTe at high temperatures

The linear coefficient of thermal expansion and the Debye temperature of PbTe in the high-temperature range have been investigated using X-ray diffractometry. The studies were carried out on samples of two types: single crystal and PbTe powder, synthesized separately. Both types of samples showed fairly similar results in all measurements. It has been established that in the temperature range 293-773 K the linear thermal expansion coefficient is constant and for powder: α=20.1· 10-6± 0.9· 10-6 K-1 and for single crystal: α=19.7· 10-6± 0.8· 10-6 K-1. The Debye temperature measured in the temperature range 293-573 K equal to 105±3 K Keywords: lead telluride, linear thermal expansion coefficient, Debye temperature.

Линейный коэффициент теплового расширения и температура Дебая PbTe при высоких температурах

The linear coefficient of thermal expansion and the Debye temperature of PbTe in the high-temperature range have been investigated using X-ray diffractometry. The studies were carried out on samples of two types: single crystal and PbTe powder, synthesized separately. Both types of samples showed fairly similar results in all measurements. It has been established that in the temperature range 293-773 K the linear thermal expansion coefficient is constant and for powder: 20.1*10-6 +/- 0.9* 10-6 K-1 and for single crystal: 19.7*10-6 +/- 0.8*10-6 K-1. The Debye temperature measured in the temperature range 293-573 K equal to 105 +/- 3 K.

Mechanochemical synthesis of mechanical bonds in M12L8 poly-[n]-catenanes.

Using mechanochemistry by grinding TPB and ZnBr2, an amorphous poly-[n]-catenane of interlocked M12L8 nanocages is obtained in good yields (∼80%) and within 15 minutes. The mechanical bond among the icosahedral M12L8 cages in the amorphous phase has been demonstrated by single crystal XRD, powder XRD and FT-IR spectroscopy following an amorphous-to-crystalline transformation by guest uptake of the amorphous phase. High-resolution solid-state 13C NMR spectroscopy gives insights into the local structure of the amorphous catenane focusing on TPB aromatic-aromatic interactions.

One pot synthesis of lanthanide-iron-sodium trimetallic metal-organic frameworks as anode materials for lithium-ion batteries

Three novel highly symmetrical metal-organic frameworks (MOFs), C30H40Fe6LnN6Na2O44P6 (Ln ​= ​La, Ce and Pr, namely FLaN-MOF, FCeN-MOF, FPrN-MOF, respectively), that contain d- and f- orbital elements were designed and successfully synthesized via a facile ionothermal method. The three-dimensional structures of MOFs that were fabricated by pmida ligands directly connecting with iron, sodium and lanthanide metals were revealed by X-ray single crystal diffractometer (SXRD) and powder X-ray diffractometer (PXRD). The MOFs were used as the electrode material for lithium-ion batteries (LIBs) and FLaN-MOF exhibits a reversible capacity of 337 mAh/g after 100 cycles at 100 ​mA/g. The electrochemical measurements demonstrate a synergetic mechanism that combines a redox-dominated process at low rates and a capacitance behavior under high current densities.