Centrosymmetric Space Group Research Articles

Synthesis, crystal growth, spectroscopic characterization, Hirshfeld surface analysis and DFT investigations of novel nonlinear optically active 4-benzoylpyridine-derived hydrazone

• FHPE hydrazone crystals grown by the slow evaporation solution growth. • FHPE crystals showed higher transparent characteristics. • Inter and intramolecular interactions were determined employing the DFT. • FHPE possessed higher hyperpolarizability (3264.29×10 -30 esu). • The higher chemical stability and reactivity of hydrazone were proved. Hydrazones are the vital compounds which possess remarkable properties and are widely used in organic synthesis, analytical chemistry and medicine. In this research, single crystals of a novel hydrazone, 4-(2-(furan-2-carbonyl)hydrazono(phenyl)methyl)-pyridin-1-ium ethylsulphate hydrate (FHPE), were grown via the slow evaporation from solution growth technique. The FHPE crystal was characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance ( 1 H and 13 C NMR) spectroscopy, single crystal X-ray diffraction, powder X-ray diffraction (PXRD), UV-Vis absorption and scanning electron microscopy (SEM) techniques. Single crystal X-ray diffraction analysis revealed that FHPE hydrazone belonged to the triclinic system with centrosymmetric space group P 1 ¯ . PXRD and SEM studies substantiated the good crystallinity of the as-grown specimen. Result of the UV-Vis absorption study proved higher transparent characteristics of FHPE crystals. The dipole moment, polarizability, HOMO-LUMO energies, oscillator strength and Mulliken charge populations were determined by density functional theory (DFT) method with B3LYP/6‒31G(d,p). The optimized molecular structure of FHPE was in concurrence with the ORTEP results. The FHPE hydrazone possessed great hyperpolarizability (3264.29×10 −30 esu) compared to that of the reference material, urea, as determined by theoretical calculations. Hirshfeld surface analysis results demonstrated proton transfer induced charge transfer and inter or intramolecular interactions, contributing superior nonlinearity of crystals. Investigations of electronic properties confirmed the greater chemical stability and reactivity of hydrazone.

2-Methyl-4-Nitroaniline Derived Novel Organic NLO crystal: Experimental and Theoretical Analysis

• A Novel organic nonlinear optical material was synthesized and reported for the first time. • The material possess better laser damage threshold compared to other well known organic materials • Experimental results were correlated with the theoretical calculations. • Maximum transmission of 87 % was observed from the material when UV rays allowed to fall on the material The present research is aimed to synthesis novel organic material 2-methyl-4-nitroaniline (MNA) derivative, dibenzyl-(2-methyl-4-nitro-phenyl)-amine (DMNPA) and grown by slow evaporation solution growth technique as a good quality single crystal. The single crystal X-ray diffraction analysis shows that DMNPA crystallizes in monoclinic crystal system which belongs to centrosymmetric space group C2/c . The grown DMNPA crystal has lower optical cut off at 443 nm. Thermal property of DMNPA shows that the material melts at 82°C and decomposes at 305°C. The material was with stand up to 1.8683 Gw/cm 2 when a laser beam of 1064 nm is allowed to fall on the material. The Z-scan study indicates that DMNPA possess positive nonlinear refractive index and there by existence of third-order nonlinearity χ (3) . Quantum chemical calculations were carried out for the isolated DMNPA molecule by density functional theory for gaining more insights.

Thermal anomalies and phase transitions in Pb2Sc2Si2O9 and Pb2In2Si2O9

Abstract Pb2Sc2Si2O9 and Pb2In2Si2O9, respectively, the scandium and indium containing structural analogues of the mineral kentrolite are grown by spontaneous crystallization from a PbO flux. The corresponding polycrystalline powder samples are synthesized by conventional solid-state approach. The compounds are thoroughly characterized using temperature-dependent single crystal and powder X-ray diffraction, heat capacity measurements, second harmonic generation experiments and Raman spectroscopy. At ambient conditions, both compounds crystallize in the non-centrosymmetric Pna21 space group and undergo phase transitions to the centrosymmetric Pbcn space group at elevated temperatures. The Pbcn into Pna21 phase transitions are complemented by the signals of the temperature-dependent second harmonic generation. The specific heat capacity exhibits distinct cusp, supporting the λ-type second-order phase transition. The temperature dependency of some selective Raman modes further complements the findings, showing softening and hardening of the phonons across the phase transitions.

DFT-Guided Crystal Structure Redetermination and Lattice Dynamics of the Intermetallic Actinoid Compound UIr.

UIr has been discussed as a rare example of a noncentrosymmetric, ferromagnetic superconductor crystallizing in the acentric PdBi structure type (P21, mP16). Here we present a new structure model for UIr. By means of single-crystal and powder X-ray diffraction we find UIr to crystallize in the centrosymmetric space group P21/c, in line with previous ab initio calculations. The discrepancy with the previous noncentrosymmetric model in space group P21 is explained by the occurrence of twinning. The observed twinning hints toward a high-temperature displacive phase transition of UIr to the CrB structure type (Cmcm, oS8): we discuss the lattice dynamics corresponding to this transition by crystallographic symmetry mode analysis and by density functional theory (DFT). We find that spin-orbit coupling is essential to understand this phase transition. We apply our theoretical considerations for a critical judgment of the structure models of UPt and NpIr that have been reported to crystallize isotypically with UIr. We confirm that UPt is isotypic to UIr (P21/c), whereas we predict NpIr to crystallize in the CrB structure type. Our report on the centrosymmetric crystal structure of UIr has an effect on all those theoretical models that investigated potentially novel superconducting coupling mechanisms of this compound on the basis of the noncentrosymmetric structure model.

Supramolecular Assembly of Morpholin-4-ium hydroxy(diphenyl)acetate—Structural, Spectral and Nonlinear Optical Analyses

A supramolecular assembly of Morpholin-4-ium hydroxy(diphenyl)acetate (MHA) was synthesized by acquiring morpholine and benzilic acid in equimolar ratio via solvent vaporization technique using methanol as a solvent. The structure of MHA was analyzed by single-crystal X-ray diffraction analysis, which confirms that the crystal is crystallized in a monoclinic crystal system with C2/c centrosymmetric space group. The molecule was stabilized via NH….O and OH..O supramolecular assembly networks. Close contacts are observed over dnorm surface with red spots, from Hirshfeld analysis which are owing to OH…O and NH…O intermolecular interactions. 1H NMR analysis confirmed the migration of proton from benzilic acid to morpholine and in 13C NMR analysis, the signal at δ 176.36 ppm confirmed the presence of highly deshielded carboxylate carbon in the molecule. The vibrational frequencies associated with the functional groups in the MHA crystal are estimated using Fourier transform infrared spectroscopy. Refractive index (n) and extinction coefficient (K), bandgap, optical conductivity (σop), electrical conductivity (σel), optical susceptibility (χop) and polarization (P) were estimated using UV–vis spectroscopy. Fluorescence peaks were observed at 334 and 380 nm via photoluminescence spectroscopy. The third order nonlinear optical properties were obtained using Z-scan studies. The Z-scan curve in the closed aperture configuration indicates the change in refractive index of the MHA crystal with a strong self-defocusing effect.

CsCdGa3O6: A I-II-III-O (I = alkali metal, II = divalent metal, III = Al, Ga, In) type oxide featuring [Ga4O14]16− helical belts linked [Ga6O6]6+ and [Ga8O8]8+ cages

Inorganic gallates are attractive owing to their abundant structures and wide applications for nonlinear optics, magnetism, molecular sieve and catalysis. Herein, a new cesium cadmium gallate, CsCdGa3O6, has been synthesized by a solid-state reaction, which is the first I-II-III-O (I ​= ​alkali metals, II ​= ​divalent metals, III = Al, Ga, In) type oxide. It crystallizes in the centrosymmetric space group P21/c, and the three-dimensional Ga–O polyanionic framework is constructed by [Ga4O14]16− helical belts linked [Ga6O6]6+ and [Ga8O8]8+ cages. Thermal analysis indicates that it possesses high thermal stability. Various characterizations and results analysis including XRD, TG-DSC, IR, Raman spectrum, as well as electronic structure calculations were performed.

A Piezoelectric Ionic Cocrystal of Glycine and Sulfamic Acid.

Cocrystallization of two or more molecular compounds can dramatically change the physicochemical properties of a functional molecule without the need for chemical modification. For example, coformers can enhance the mechanical stability, processability, and solubility of pharmaceutical compounds to enable better medicines. Here, we demonstrate that amino acid cocrystals can enhance functional electromechanical properties in simple, sustainable materials as exemplified by glycine and sulfamic acid. These coformers crystallize independently in centrosymmetric space groups when they are grown as single-component crystals but form a noncentrosymmetric, electromechanically active ionic cocrystal when they are crystallized together. The piezoelectricity of the cocrystal is characterized using techniques tailored to overcome the challenges associated with measuring the electromechanical properties of soft (organic) crystals. The piezoelectric tensor of the cocrystal is mapped using density functional theory (DFT) computer models, and the predicted single-crystal longitudinal response of 2 pC/N is verified using second-harmonic generation (SHG) and piezoresponse force microscopy (PFM). The experimental measurements are facilitated by polycrystalline film growth that allows for macroscopic and nanoscale quantification of the longitudinal out-of-plane response, which is in the range exploited in piezoelectric technologies made from quartz, aluminum nitride, and zinc oxide. The large-area polycrystalline film retains a damped response of ≥0.2 pC/N, indicating the potential for application of such inexpensive and eco-friendly amino acid–based cocrystal coatings in, for example, autonomous ambient-powered devices in edge computing.

The structure of the aluminium-abundant γ-brass-type Al8.6Mn4.4.

An aluminium-abundant Al8Mn5/γ-brass-type inter-metallic with formula Al8.6Mn4.4, which is isotypic with γ-Al8Cr5 and γ-Al8V5, was discovered by high-temperature sinter-ing of an Al/Mn mixture with initial composition Al2Mn. Structure analysis revealed that one special position (Wyckoff site 18h in space group R m) is shared by Al and Mn, with refined site occupancy factors of 0.7 and 0.3, respectively. The present low-temperature Al8Mn5-type phase crystallizes in the centrosymmetric space group R m (No. 166), rather than R3m (No. 160) as previously reported for the same inter-metallic characterized by TEM measurements [Zeng et al. (2018 ▸). Acta Mater. 153, 364-376].

Experimental and theoretical studies on bis (6-nitroquinoline) fumaric acid co-crystal

6-Nitroquinoline fumaric acid (C11H8N2O4), an organic co-crystal is grown using slow evaporation solution growth technique. The grown crystal is characterized by single crystal X-ray diffraction (SCXRD) and the title compound is crystallized in monoclinic crystal system with P21/n centrosymmetric space group. The OH···N and CH···O hydrogen bonds influence heterodimer formation in the crystal structure. The optical absorption spectrum of the title compound shows an absorption peak at 333 nm which contributes to π→π* transition. The transmission spectrum shows about 82% transparency in the visible region with lower cutoff wavelength 370 nm. The vibrational modes and assignments of functional groups are done using FTIR and Raman spectroscopic analyses. The CO stretching is the most characteristic vibration of the carboxylic acid group and it typically appears at 1393 cm−1. The thermal behavior of the present compound is evaluated by TG/DSC techniques and the melting point of the title crystal is 191 °C. The finger print plots show that H···O (41.9%) interactions are dominated interactions. These interactions are responsible for CH···O hydrogen bonds which play vital role in the structure stabilization. The first order hyperpolarizability value is calculated using B3LYP method with the extended 6–311++G(d,p) basis set and it is found as 4.5 times larger than that of urea.

Synthesis and characterization of a novel alkali mixed magnesium-aluminum phosphate with a layered structure–KMgAl(PO4)2

A novel phosphate compound - potassium magnesium-aluminum double phosphate with chemical formula KMgAl(PO4)2 - has been synthesized. Platelet-shaped single crystals have been grown from the flux using K2Mo2O7 as a solvent. The powder form has been obtained through a sol-gel reaction. It has been characterized by X-ray diffraction, differential thermal analysis, vibrational spectroscopy and electronic structure calculations. KMgAl(PO4)2 crystallizes in the trigonal centrosymmetric space group P3¯m1 (No. 164) with unit cell parameters a = b = 5.347(1) Å, c = 7.903(10) Å, γ = 120° (Z = 1). The main characteristic of the crystal is the two-dimensional (2D) lamellar framework formed by Mg|AlO4 and PO4 tetrahedrons sharing their vertices of oxygen atoms, with the K+ cations located within the interlayer space. The sample morphology and chemical composition were revealed by the scanning electron microscopy – energy-dispersive X-ray spectroscopy analysis. The IR spectroscopy of KMgAl(PO4)2 confirmed the existence of a single PO4 group in agreement with the structural study. A relatively large indirect band gap of 3.86 eV was determined.

Noncovalent Bonding Caught in Action: From Amorphous to Cocrystalline Molecular Thin Films.

We demonstrate the solvent-free amorphous-to-cocrystalline transformations of nanoscale molecular films. Exposing amorphous films to vapors of a haloarene results in the formation of a cocrystalline coating. This transformation proceeds by gradual strengthening of halogen-bonding interactions as a result of the crystallization process. The gas-solid diffusion mechanism involves formation of an amorphous metastable phase prior to crystallization of the films. In situ optical microscopy shows mass transport during this process, which is confirmed by cross-section analysis of the final structures using focused ion beam milling combined with scanning electron microscopy. Nanomechanical measurements show that the rigidity of the amorphous films influences the crystallization process. This surface transformation results in molecular arrangements that are not readily obtained through other means. Cocrystals grown in solution crystallize in a monoclinic centrosymmetric space group, whereas the on-surface halogen-bonded assembly crystallizes into a noncentrosymmetric material with a bulk second-order nonlinear optical response.

Ferrocene/non-ferrocene conjugated linear eight-membered borasiloxanes: Structural, theoretical, optical and non-linear optical studies

A linear donor-π-acceptor-π-donor (D-π-A-π-D) type 4-methoxyphenyl 1 and 4-ferrocenylphenyl 2 conjugated borasiloxanes were synthesized and characterized by various spectroscopic techniques (FT-IR, NMR and HRMS). Further, the molecular structure of 4-methoxyphenyl borasiloxane 1 was confirmed by the single-crystal X-ray diffraction method, shows a monoclinic crystal system in the centrosymmetric space group (P21/c) with various non-covalent interactions in the crystal packing. The intramolecular charge transfer (ICT) process of both the borasiloxanes were studied using the solvatochromic technique, which shows negative solvatochromism for 1 and 2, due to the high ground state dipole moment than the excited states. The second-order nonlinear optical (NLO) properties of the borasiloxanes were studied using Kurtz and Perry powder method. Compound 1 was crystallized in a centrosymmetric crystal system, and it exhibits second-order NLO response, because of the distorted silicon environment in an eight-membered borasiloxane ring with various C–H...π interactions in the crystal packing. The 4-ferrocenylphenyl borasiloxane 2 shows 1.5 times higher SHG efficiency than 1, due to the ferrocene moiety is conjugated in the para position of the borasiloxane ring, which involves an effective one-electron transfer process (FeII ↔ FeIII). Furthermore, the experimental results of optical and nonlinear optical properties of the borasiloxanes 1 and 2 were supported by the DFT and TD-DFT calculations using the B3LYP/6-31+G** level of theory.

Solid Solution Yb2-xCaxCdSb2: Structure, Thermoelectric Properties, and Quality Factor.

Solid solutions of Yb2-xAxCdSb2 (A = Ca, Sr, Eu; x ≤ 1) are of interest for their promising thermoelectric (TE) properties. Of these solid solutions, Yb2-xCaxCdSb2 has end members with different crystal structures. Yb2CdSb2 crystallizes in the polar space group Cmc21, whereas Ca2CdSb2 crystallizes in the centrosymmetric space group Pnma. Other solid solutions, Yb2-xAxCdSb2 (A = Sr, Eu), crystallize in the polar space group for x ≤ 1, and compositions with x ≥ 1 have not been reported. Both structure types are composed of corner-sharing CdSb4 tetrahedra condensed into sheets that differ by the stacking of the layers. Single crystals of the solid solution Yb2-xCaxCdSb2 (x = 0-1) were studied to elucidate the structural transition between the Yb2CdSb2 and Ca2CdSb2 structure types. For x ≤ 1, the structures remain in the polar space group Cmc21. As the Ca content is increased, a positional disorder arises in the intralayer cation sites (Yb2/Ca2) and the Cd site, resulting in inversion of the CdSb4 tetrahedral chain. This phenomenon could be indicative of an intergrowth of the opposing space group. The TE properties of polycrystalline samples of Yb2-xCaxCdSb2 (x ≤ 1) were measured from 300 to 525 K. The lattice thermal conductivity is extremely low (0.3-0.4 W/m·K) and the Seebeck coefficients are high (100-180 μV/K) across the temperature range. First-principles calculations show a minimum in the thermal conductivity for the x = 0.3 composition, in good agreement with experimental data. The low thermal conductivity stems from the acoustic branches being confined to low frequencies and a large number of phonon scattering channels provided by the localized optical branches. The TE quality factor of the Yb1.7A0.3CdSb2 (A = Ca, Sr, Eu) series has been calculated and predicts that the A = Ca and Sr solid solutions may not improve with carrier concentration optimization but that the Eu series is worthy of additional modifications. Overall, the x = 0.3 compositions provide the highest zT because they provide the best electronic properties with the lowest thermal conductivity.

Application of result of atoms and centrosymmetric cubic space groups for sharpening of Patterson function

Application of result of atoms and centrosymmetric cubic space groups for sharpening of Patterson function

An attempt to find the use of atomic scattering factors and centrosymmetric cubic space groups: two choices of random phases in direct methods

An attempt to find the use of atomic scattering factors and centrosymmetric cubic space groups: two choices of random phases in direct methods

Symmetry Breaking of Atomically Precise Fullerene-like Metal Nanoclusters.

Here we report a neutral fullerene-like core-shell homosilver Ag13@Ag20 nanocluster that is fully protected by an achiral bidentate thiolate ligand (9,12-dimercapto-1,2-closo-carborane, C2B10H10S2H2), which crystallizes in centrosymmetric space group R3̅. Continuous Cu doping in the dodecahedral shell first induced symmetry breaking to generate chiral Ag13@Ag20-nCun (6 ≥ n ≥ 2) containing two acetonitrile ligands in space group P212121, and then produced symmetric all-thiolated Ag13@Ag20-nCun (20 ≥ n ≥ 13) in the higher space group Im3̅. The selectively copper-doped Ag13@Ag20-nCun (6 ≥ n ≥ 2) cluster has its structure reorganized to a lower symmetry that shows chiroptical activity. Moreover, structural distortion of Ag13@Ag20-nCun (6 ≥ n ≥ 2) further expanded in chiral R-/S-propylene oxide, which induced a more prominent core-based CD response. This work revealed a novel mechanism of chirality generation at the atomic level through asymmetric shell-doping of metal nanoclusters, which provides new insight into the origin of chirality in inorganic nanostructures.

Quantitative phase analysis of Bi2Sr2CaCu2O8+x and competing intergrowth and co-crystallizing phases via a Rietveld refinement study

The Rietveld refinement technique has been used to determine the extent of intergrowth of the Bi2Sr2CuO6+x phase and co-crystallization of competing phases in the high-temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212). The refinement was done on powder diffractograms obtained on powders made by grinding single crystals of Bi2Sr2CaCu2O8+x grown using two different self-flux techniques, namely the pressure technique and the regrowth technique, and ground for either 2 min or 2 h. The Rietveld programs JANA and FULLPROF were used for the refinement and both gave consistent results. The Bi and Sr atom positions were refined in the average structure of centrosymmetric space group Bbmb. To incorporate Bi-atom modulation and extract information about the modulation vector, refinement was done in the centrosymmetric space group N^{Bbmb}_{1\overline 11}(Bbmb(0γ1)). The b* component of the modulation vector decreases with a decrease in the superconducting transition temperature in the pressure-technique sample compared with the regrowth sample, suggesting a better alignment of the CuO2 planes with respect to the Bi–O planes in the pressure-technique sample. All the samples exhibit a strong preferred orientation effect. Values of the March–Dollase parameters corresponding to the preferred orientation function were obtained. Brindley absorption contrast factors t ϕ were also calculated, together with the effect of microabsorption on the number of phases present in each sample. Rietveld refinements incorporating all the factors resulted in excellent values for the goodness-of-fit parameters for all the samples, with the lowest value of 2.08 for the pressure-technique sample ground for 2 min. Additionally, the powders corresponding to the pressure-technique crystals have no co-crystallizing phase and ∼94% of the Bi-2212 phase, suggesting that crystals grown by the pressure technique are of extremely good quality, much better than those grown by the regrowth flux technique.

Growth, characterisation and DFT investigations on 3-hydroxy-6- methyl -2- nitropyridine (3H6M2NP)-A novel third order nonlinear optical material

Single crystals of nitropyridine derivative 3-hydroxy-6-methyl-2-nitropyridine was grown by slow evaporation solution growth technique using ethanol. 3H6M2NP was crystallized in orthorhombic crystal system with centrosymmetric space group Pbca. The crystalline nature, presence of functional groups and its vibrational modes were assigned using FT-IR and FT-Raman spectroscopic techniques. The UV–Vis spectrum reveals 3H6M2NP crystal is transparent in the visible region with lower cut-off wavelength. The luminescence properties were confirmed by PL spectrum and 3H6M2NP crystal exhibited thermal stability up to 182 °C. The molecular structure of 3H6M2NP was optimised and all ab initio calculations were done theoretically. From Z-scan technique, the third order nonlinear optical susceptibility of the grown crystal was found to be χ3 = 2.616 × 10−8 esu. The hyper polarizability value was found to be 2.9 times larger than that of the urea which settles the NLO activity.

Transport properties and thermal behavior of YbMnSb2 semimetal above room temperature

Single crystals of ytterbium manganese diantimonide, YbMnSb2 have been grown from a high-temperature reaction of the elements, employing molten Sb as self-flux. This phase crystallizes in the tetragonal centrosymmetric space group P4/nmm (No. 129) and adopts the ZrCuSiAs structure type. The structure consists of Sb-based square nets and PbO-type layers formed by fused [MnSb4/4] tetrahedra. YbMnSb2 is stable under ambient atmosphere and incongruently melts at a temperature of ca. 1120 K. In the temperature range from 300 ​K to 450 ​K, the electrical resistivity of the as-grown single-crystalline material is as low as 3.2 ​mΩ ​cm, while its thermopower is as high as 180 ​μV/K. As such, YbMnSb2 shows promise for thermoelectric applications in the mid-temperature region, with an estimated power factor of 0.85–0.95 mW/(m K2).

Tunable phase transition, band gap and SHG properties by halogen replacement of hybrid perovskites [(thiomorpholinium)PbX3, X = Cl, Br, I

By the replacement of halogen anion, three new multifunctional organic-inorganic hybrid perovskites (thiomorpholinium)PbX3 (X = Cl, Br, I) were successfully synthesized and underwent reversible structural transformation above room temperature, accompanied by the anomalous change of dielectric constant. With the adjustment of the halogen anion from Cl to I in the inorganic skeleton, the space group is transformed from centrosymmetric space group P21/c ((thiomorpholinium)PbCl3) to chiral one P212121 ((thiomorpholinium)PbBr3, (thiomorpholinium)PbI3) at room temperature. The ordered-disordered transition of organic cations and the change of hydrogen bonds with the increase of temperature lead to above-room-temperature phase transitions. Ultraviolet absorption and second-harmonic generation (SHG) measurements confirmed that both the band gap and SHG activity of (thiomorpholinium)PbX3 (X = Cl, Br, I) crystals were tunable. The band gaps reveal a broadening trend with 3.532 eV, 3.410 eV and 3.175 eV along the Cl → Br → I series. This work provides an effective molecular design for multifunctional organic-inorganic perovskites.