Single-crystal X-ray Experiments Research Articles

High-pressure behaviour and atomic-scale deformation mechanisms in inyoite, CaB3O3(OH)5·4H2O

The compressional behaviour of inyoite, ideally CaB3O3(OH)5·4H2O, has been studied by an in-situ high-pressure single-crystal X-ray experiment, at the ESRF large-scale facility, up to 19.80(5) GPa. Inyoite undergoes a first-order phase transition to inyoite-II, bracketed between 8.25(5) and 8.86(5) GPa, with a large volume discontinuity (ΔV ⁓ 7.5%). The structure of the high-pressure polymorph has not been solved due to a significant decrease in the number of Bragg reflections. The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of inyoite was found to be KV0 = 26.9(8) GPa, whereas in inyoite-II, the KV0 value increases to 52(5) GPa. The increase of the bulk modulus is paired with a sharp decrease of the anisotropy of compressibility, as shown by the magnitude of the Eulerian finite unit-strain ellipsoid with: ε1:ε2:ε3 = 3.5:2.1:1 in inyoite and ε1:ε2:ε3 = 1.5:1.1:1 in inyoite-II. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of inyoite are here described on the basis of a series of structure refinements.

Structure of Pb(Fe2/3W1/3)O3 single crystals with partial cation order

Despite intensive studies on the complex perovskite Pb(Fe2/3W1/3)O3 (PFWO) relaxor, understanding the exact nature of its multifunctional properties has remained a challenge for decades. In this work we report a comprehensive structural study of the PFWO single crystals using a combination of synchrotron X-ray diffraction and high-resolution electron microscopy. The set of {h + ½, k + ½, l + ½} superlattice reflections was observed for the first time based on single-crystal synchrotron X-ray experiments (100–450 K) and transmission electron microscopy investigations, which indicates some kind of B-cation ordering in PFWO which had been thought to be totally disordered. It was found that (1) the crystal structure of PFWO should be described by a partly ordered cubic perovskite (i.e. Fm − 3m), (2) the weak ferromagnetic properties and excess magnetic moment of PFWO can be understood based on non-random distribution of Fe cations between the 4a and 4b sites, and (3) the Pb displacement disorder is present in this material and the cations are probably displaced along the <100> directions. The X-ray diffraction results of this investigation show that partial cation ordering indeed exists in PFWO, which makes it necessary to revisit the generally accepted interpretations of the results obtained up to date. In agreement with X-ray diffraction study the main results of TEM study include: (1) a long range order that can be described with the Fm − 3m symmetry is reliably detected, (2) the coherence length of that long range order is in the order of 1–2 nm and (3) no remarkable chemical inhomogeneity is found in the tested PFWO crystal, excluding the possibility of a compositional ordering arising from substitutional defects in the perovskite structure.

New Cu(II), Co(III) and Ni(II) metal complexes based on ONO donor tridentate hydrazone: Synthesis, structural characterization, and investigation of some biological properties

New Cu(II), Co(III) and Ni(II) metal complexes of N'-(3-ethoxy-2-hydroxybenzylidene)acetohydrazide (ehbahH2) ligand derived from 3-ethoxysalicylaldehyde and acethydrazide were obtained. The K[Cu(ehbah)(OAc)]·2H2O (1), K[Co(ehbah)2]·H2O (2) and [Ni(ehbahH)2] (3) complexes were characterized by elemental analysis, LC-MS and magnetic susceptibility measurements, electronic, IR spectra and thermal experiments (TGA and DTA). The molecular structures of 1 and 2 were also established by single-crystal X-ray diffraction. Both complexes had a complex ion unit and a potassium (I) cation leading to a neutral three-dimensional network. The single-crystal X-ray experiments revealed that the complex ions of 1 and 2 exhibited distortion in the square-planar and octahedral geometry, with ligand in enol form. The characterization studies of the complex 3 showed that the ligand was coordinated in the keto tautomeric form, and the ratio of metal ligand was 1:2. All of the compounds were screened for their in vitro antibacterial and antifungal activity. The cleavage activities of the ligand and its complexes were assayed on supercoiled pBR322 DNA by the agarose gel electrophoresis method in the presence and absence of H2O2. The results indicated that only 1 and 2 effectively cleaved pBR322 DNA. Lastly, all compounds obtained in the study were evaluated for their antioxidant (ABTS radical scavenging) properties.

Crystal structure, NMR and catalytic properties of a bis-peroxovanadium [NH4][VO(O2)2(mpa)]·H2O

By reacting NH4VO3 and mpa (mpa = 4-methoxypicolinamide) in the presence of H2O2, a bis-peroxovanadium [NH4][VO(O2)2(mpa)]·H2O (1) was obtained and characterized by X-ray single-crystal diffraction. Structural analyses demonstrate that 1 belongs to the monoclinic space group P21/c and consists of a bis-peroxovanadium [VO(O2)2(mpa)]−, one NH4+ counterion and one free lattice water. Adjacent [VO(O2)2(mpa)]− anions construct a 3D supramolecular framework through intra- and intermolecular hydrogen bonding interactions. The compositions of 1 in solution are investigated by using multinuclear (1H, 13C, and 51V) magnetic resonance, COSY, HSQC, HMBC, and variable temperature NMR in a 0.15 mol L−1 NaCl/D2O solution that mimics the physiological conditions. Comparing the results of single-crystal X-ray and NMR experiments, the VV ion in the undissociated [VO(O2)2(mpa)]− in solution displays a similar seven-coordinate distorted pentagonal bipyramidal geometry with the solid-state crystal. The catalytic activity of the 1 in the oxidative bromination for phenol/aniline-like compounds to mimic bromoperoxidases reactivity was also studied.

Structural evolution of gypsum under high pressure: single-crystal X-ray experiments revisited

The structures of gypsum at pressures up to approximately 4 GPa are studied with density functional theory (DFT) and thoroughly compared with single-crystal X-ray diffraction experiments reported in the literature [Comodi et al. in (Am Miner 93:1530–1537, 2008)]. It is found that the exchange–correlation density functional revPBE (revised Perdew–Burke–Ernzerhof) in conjunction with a nonlocal van der Waals (vdW) correction is capable of modeling the lattice constants, axial compressibility, and bulk modulus with good accuracy, suggesting that the inclusion of the vdW functional is crucially important for understanding the structure of hydrous minerals. To gain further physical insights, the geometric parameters associated with the constituting components of gypsum (water molecules, SO4 tetrahedra, and CaO8 polyhedra) are analyzed and compared with the experimental values. DFT simulations show that, under pressure, the polyhedral layers remain as nearly planar sheets of interconnecting SO4 tetrahedra and CaO8 polyhedra without further crinkling. DFT analysis on the layer compressibility along the major crystal axis reveals that, in contrast to experimental reports, the hydrous interlayer is less compressible than the polyhedral layer. Squeezed by the lateral pressure, the water molecules in the hydrous interlayer become better affixed along the major axis, making the interlayer harder to compress along this axis.

Synthesis and Characterization of Electron-Deficient Asymmetrically Substituted Diarylindenotetracenes.

Electron-deficient asymmetrically substituted diarylindenotetracenes were prepared via a series of Friedel-Crafts acylations, aryl-aryl cross-couplings, and an intramolecular oxidative cyclization to form the indene ring. Single-crystal X-ray experiments showed good π-π overlap with π-π distances ranging from 3.26 to 3.76 Å. Both thermogravimetric analysis and differential scanning calorimetry indicated that asymmetrically substituted indenotetracenes (ASIs) are stable at elevated temperatures. From cyclic voltammetry experiments, HOMO/LUMO energy levels of ASI derivatives were determined to be near -5.4/-4.0 eV. UV/visible absorption spectra showed strong absorption of light between 400 and 650 nm with molar attenuation coefficients from 104 to 105 M-1 cm-1. ASIs were also found to have very low fluorescence quantum yields, less than 4%. Using the solid-state packing determined from the single-crystal X-ray experiments, computational modeling indicated that ASI molecules should favor electron transport.

Penicilliumin B, a novel sesquiterpene methylcyclopentenedione from a deep sea-derived Penicillium strain with renoprotective activities

A novel sesquiterpene methylcyclopentenedione, penicilliumin B (1), was obtained from a deep sea-derived fungus Penicillium sp. F00120, together with three known sesquiterpene cyclohexenones (2–4). Penicilliumin B (1), presenting the first example with the sesquiterpene cyclopentenedione skeleton as natural products, was structurally determined by analysis of the NMR and MS spectroscopic data, while the absolute configurations were assigned by single-crystal X-ray experiments. The plausible biosynthetic pathway of the unusual cyclopentenone skeleton of 1 was proposed. Penicilliumin B (1), with low toxicity, was showed significant potential to inhibit the kidney fibrogenic action in vitro, by a mechanism dependent on disruption of oxidative stress, presenting a new type of promising renoprotective agent.

Impact of Molecular Flexibility on Double Polymorphism, Solid Solutions and Chiral Discrimination during Crystallization of Diprophylline Enantiomers

The polymorphic behavior of racemic and enantiopure diprophylline (DPL), a chiral derivative of theophylline marketed as a racemic solid, has been investigated by combining differential scanning calorimetry, powder X-ray diffraction, hot-stage microscopy and single-crystal X-ray experiments. The pure enantiomers were obtained by a chemical synthesis route, and additionally an enantioselective crystallization procedure was developed. The binary phase diagram between the DPL enantiomers was constructed and revealed a double polymorphism (i.e., polymorphism both of the racemic mixture and of the pure enantiomer). The study of the various equilibria in this highly unusual phase diagram revealed a complex situation since mixtures of DPL enantiomers can crystallize either as a stable racemic compound, a metastable conglomerate, or two distinct metastable solid solutions. Crystal structure analysis revealed that the DPL molecules adopt different conformations in the crystal forms suggesting that the conformational degrees of freedom of the substituent that carries the only two H-bond donor groups might be related to the versatile crystallization behavior of DPL. The control of these equilibria and the use of a suitable solvent allowed the design of an efficient protocol for the preparative resolution of racemic DPL via preferential crystallization. Therefore, the resolution of DPL enantiomers despite the existence of a racemic compound stable at any temperature demonstrates that the detection of a stable conglomerate is not mandatory for the implementation of preferential crystallization.

ChemInform Abstract: Synthesis of Prochiral Imines from Aromatic Ketones Using Magnesium Perchlorate as Catalytic Promotor.

Abstract We report the synthesis of new prochiral imines by the reaction of nonsymmetric benzophenone derivates, bencylamines, and anilines in good yields. All the products were characterized by 1H and 13C NMR as an isomeric E/Z mixture. Also, the molecular structures for five derivatives determined by single-crystal x-ray experiments are presented. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Synthesis of Prochiral Imines from Aromatic Ketones Using Magnesium Perchlorate as Catalytic Promotor

We report the synthesis of new prochiral imines by the reaction of nonsymmetric benzophenone derivates, bencylamines, and anilines in good yields. All the products were characterized by 1H and 13C NMR as an isomeric E/Z mixture. Also, the molecular structures for five derivatives determined by single-crystal x-ray experiments are presented. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Culcitiolides A-D, Four New Eremophilane-Type Sesquiterpene Derivatives from Senecio Culcitioides

Four new eremophilane-type sesquiterpenes, culcitiolides A-D, were isolated from the stem of Senecio culcitioides Sch. Bip (Asteraceae). Their structures were established by detailed 2D NMR spectroscopic and single-crystal X-ray experiments. These compounds were assessed for inhibitory activity against nuclear factor kappaB (NF-kappaB). Culcitiolides C and D at 20 microM showed 97 and 100% inhibition of NF-kappaB activity, respectively.

Diterpenoids from Euphorbia neriifolia

Nine diterpenoids were isolated from the stems of Euphorbia neriifolia Linn. with their structures established by 1D and 2D NMR techniques. Relative stereochemistries were determined by ROESY, and single-crystal X-ray experiments.

Temperature Dependence of Diffuse Scattering in PZN

Structural disorder seems to relate to the useful physical properties of ferroelectrics and relaxors. One such material is PZN, \(\hbox{PbZn}_{1/3}\hbox{Nb}_{2/3}\hbox{O}_{3}.\) To explore what aspects of the disorder are specific to the polarized state, the temperature dependence of diffuse scattering in PZN has been investigated. The data were collected using both neutron and X-ray single crystal experiments in a range of temperatures from 50 K to 500 K (−223 °C to 227 °C). It has been found that some features, like the diffuse scattering from the B-site ordering, remain unchanged with change of temperature in terms of both intensity and peak shape. However, other diffuse scattering features evolve with T, for example the size effect scattering around the Bragg peaks. The size-effect becomes less pronounced with increasing temperature, with the diffuse scattering becoming more symmetric around the Bragg peaks. The diffuse rods caused by the planar domains change only slightly with temperature. This finding indicates that the planar domains persist into the paraelectric state but that the correlation between lead displacement and the average separation of adjacent lead atoms becomes weaker, suggesting that this size effect may be crucial to the ferroelectric properties.

The ternary system cerium–rhodium–silicon

Phase relations have been established in the ternary system Ce–Rh–Si for the isothermal section at 800 °C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800 °C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: τ 7—Ce 3RhSi 3, (Ba 3Al 2Ge 2-type), τ 8—Ce 2Rh 3− x Si 3+ x (Ce 2Rh 1.35Ge 4.65-type), τ 10—Ce 3Rh 4− x Si 4+ x (U 3Ni 4Si 4-type), τ 11—CeRh 6Si 4 (LiCo 6P 4-type), τ 13—Ce 6Rh 30Si 19.3 (U 6Co 30Si 19-type), τ 18—Ce 4Rh 4Si 3 (Sm 4Pd 4Si 3-type), τ 21—CeRh 2Si (CeIr 2Si-type), τ 22—Ce 2Rh 3+ x Si 1− x (Y 2Rh 3Ge-type) and τ 24—Ce 8(Rh 1− x Si x ) 24Si (Ce 8Pd 24Sb-type). For τ 25—Ce 4(Rh 1− x Si x ) 12Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for τ 3—CeRhSi 2 (CeNiSi 2-type) and τ 6—Ce 2Rh 3Si 5 (U 2Co 3Si 5-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of τ 4—Ce 22Rh 22Si 56, τ 5—Ce 20Rh 27Si 53 and τ 23—Ce 33.3Rh 58.2−55.2Si 8.5−11.5 are unknown. High temperature compounds with compositions Ce 10Rh 51Si 33 (U 10Co 51Si 33-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800 °C.

Bioactive Nortriterpenoids from Schisandra grandiflora

Three new nortriterpenoids, schigrandilactones A-C (1-3), along with eight known compounds, were isolated from an organic solvent extract of Schisandra grandiflora. Compounds 1 and 2 feature a spirocyclic moiety in their structures, and compound 3 was characterized with a new oxygenated pattern. The relative configurations of 1 and 3 were determined through single-crystal X-ray experiments. In addition, compounds 1 and 2 displayed cytotoxic activity against two human cancer cell lines, and compound 3 showed anti-HIV-1 inhibition in infected C8166 cells.

A New Unusual Natural Pigment from Selaginella sinensis and Its Noticeable Physicochemical Properties

A new unusual pigment with a novel carbon framework named selaginellin (1) was isolated from the acetone extract of Selaginella sinensis, and its methoxy derivative (1a) was synthesized. Both selaginellin 1 and 1a are racemic compounds. The structure of selaginellin 1 was established as (R,S)-4-[(4'-hydroxy-4-(hydroxymethyl)-3-((4-hydroxyphenyl)ethynyl)biphenyl-2-yl)(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one and 1a as (R,S)-4-[(4'-methoxy-4-(methoxymethyl)-3-((4-methoxyphenyl)ethynyl)biphenyl-2-yl)(4-methoxyphenyl)methylene]-2,5-cyclohexadien-1-one by the analysis of one- and two-dimensional NMR data, HR-ESIMS, EI-MS, IR, UV, CD, and single-crystal X-ray experiments, and the mechanism of their color change according to different pH values and fluorescent properties was studied.

Eremophilane Sesquiterpenes fromLigularia myriocephala

Five new eremophilenolides, 1beta-angeloyloxy-6beta,10beta-dihydroxy-8beta-methoxyeremophil-7(11)-en-8alpha,12-olide ( 1), 1beta-angeloyloxy-6beta,10alpha-dihydroxy-8alpha-methoxyeremophil-7(11)-en-8beta,12-olide ( 2), 1beta,6beta-diangeloyloxy-8beta,10beta-dihydroxyeremophil-(11)-en-8alpha,12-olide ( 3), 1beta,6beta-diangeloyloxy-8alpha,10 alpha-dihydroxyeremophil-7(11)-en-8beta,12-olide ( 4), 1beta-angeloyloxy-8-oxoeremophil-6,9-dien-12-oic acid methyl ester ( 5) and one known compound, 8beta,10beta-dihydroxyeremophilenolide ( 6) were isolated from the extract of the whole plant of Ligularia myriocephala Ling. Their structures and stereochemistry were elucidated by various spectroscopic methods including intensive 2D-NMR techniques (COSY, gHMQC, gHMBC and (1)H- (1)H NOESY) and HR-ESI-MS. A single-crystal X-ray experiment was performed for compound 1.

Idesolide: A New Spiro Compound from Idesia polycarpa.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Lancifodilactone F: A Novel Nortriterpenoid Possessing a Unique Skeleton from Schisandra lancifolia and Its anti‐HIV Activity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Idesolide: A New Spiro Compound from Idesia polycarpa

[structure: see text]. Idesolide, a new spiro compound possessing tetrahydrobenzodioxole structure, was isolated from the fruits of Idesia polycarpa Maxim. Its structure was established by NMR and MS spectroscopic analysis with single-crystal X-ray experiments. Idesolide significantly reduced nitric oxide production induced by lipopolysaccharide in BV2 microglial cells.