Ba Distances Research Articles

Clustered atom-replaced structure in single-crystal-like metal oxide

By means of metal organic deposition using trifluoroacetates (TFA-MOD), we replaced and localized two or more atoms in a single-crystalline structure having almost perfect orientation. Thus, we created a new functional structure, namely, clustered atom-replaced structure (CARS), having single-crystal-like metal oxide. We replaced metals in the oxide with Sm and Lu and localized them. Energy dispersive x-ray spectroscopy results, where the Sm signal increases with the Lu signal in the single-crystalline structure, confirm evidence of CARS. We also form other CARS with three additional metals, including Pr. The valence number of Pr might change from 3+ to approximately 4+, thereby reducing the Pr–Ba distance. We directly observed the structure by a high-angle annular dark-field image, which provided further evidence of CARS. The key to establishing CARS is an equilibrium chemical reaction and a combination of additional larger and smaller unit cells to matrix cells. We made a new functional metal oxide with CARS and expect to realize CARS in other metal oxide structures in the future by using the above-mentioned process.

Mechanisms of hexabromocyclododecanes induced developmental toxicity in marine medaka (Oryzias melastigma) embryos

Hexabromocyclododecanes (HBCDs) are widely used as additive brominated flame retardants, and are now ubiquitous contaminants in the environmental media and biota, including the marine environment and marine organisms. However, the impacts of HBCDs on marine fish are not well known. In this study the embryos of marine medaka (Oryzias melastigma) were used to assess the developmental toxicity of HBCDs. Freshly fertilized marine medaka embryos were exposed to various concentrations of technical HBCD (tHBCD, 0, 5, 20 and 50μg/L) until the first fry stage, and hatch success, morphology and cardiac function were examined. In all the exposure groups (5, 20 and 50μg/L) tHBCD significantly increased the embryo heart beats. The measurement of sinus venosus–bulbus arteriosus (SV–BA) distance indicated that tHBCD significantly enlarged the SV–BA distance at exposure concentrations of 20 and 50μg/L. The malformation rate at the first fry stage was also induced by tHBCD in a dose dependent manner, with the formation of pericardial edema and yolk sac edema as the most frequently observed malformation. In addition, the concentrations of total HBCD isomers (ΣHBCDs) in embryos in the current study were comparative with environmental levels and increased with increasing exposure duration. Furthermore, exposure to tHBCD also induced the level of 8-oxodG, a representative oxidative DNA damage. The mechanisms of HBCD-induced developmental toxicity were further explored by TUNEL assay, gel-based quantitative proteomic approach and measurement of the expression of several stress responsive genes, such as p53, TNF-α, IL-1β, CYP1A, COX-1 and COX-2, together with the activities of caspases. The results suggested that HBCDs exposure at environmentally realistic concentrations induced oxidative stress and apoptosis, and suppressed nucleotide and protein synthesis, which all together resulted in developmental toxicity, particularly in the cardiovascular system, in the embryos of O. melastigma.

Difference in the Nature of Eu3+ Environment in Eu3+‐Doped BaTiO3 and BaSnO3

BaTiO3 and BaSnO3 samples doped with Eu3+ ions were prepared using glycine‐nitrate gel combustion method. Relative intensities and line shapes of magnetic dipole allowed 5D0 → 7F1 and electric dipole allowed 5D0 → 7F2 transitions of Eu3+ from the hosts, BaTiO3 and BaSnO3, are significantly different. Based on detailed structural investigations, it is confirmed that synthesizedBaTiO3 sample is tetragonal with no center of symmetry around Ba2+ ions. Unlike this BaSnO3 is cubic with centrosymmetric Ba2+ site. From X‐ray diffraction and experimentally obtained Judd–Ofelt parameters (Ω2 and Ω4 values), it is confirmed that in BaTiO3 there is a decrease in the average Ba–O and Ba–Ba distances compared with that in BaSnO3. This leads to higher Eu–O bond polarizability and adds to the distortion in its environment around Eu3+ in BaTiO3:Eu compared with BaSnO3:Eu. This is responsible for the observed difference in the luminescence properties.

Polyhydrides of the Alkaline Earth Metals: A Look at the Extremes under Pressure

Evolutionary structure searches are coupled with density functional theory calculations to predict the most stable stoichiometries and structures of beryllium and barium polyhydrides, MHn with n > 2 and M = Be/Ba, under pressure. Even though the BeHn stoichiometries we explored do not become thermodynamically stable with respect to decomposition into the classic hydride BeH2 and H2 up to 200 GPa, we find a new phase of BeH2 with R3̅m symmetry above 150 GPa. The barium polyhydrides become thermodynamically preferred by 20 GPa. They sport complex hydrogenic sublattices composed of H–, H3–, and H2 units. BaH6 is the first stoichiometry to emerge as stable and metallic (∼60 GPa using the Perdew–Burke–Ernzerhof functional), and the P4/mmm symmetry structure is estimated to become superconducting below 30–38 K at 100 GPa. Phases with an even greater hydrogen content lie on the convex hull at higher pressures, and an intriguing BaH10 stoichiometery becomes the global thermodynamic minimum around 150 GPa. BaH10 remains metallic over its predicted domain of existence, and its Ba–Ba distances resemble those found in the complex Ba–IVc structure at 19 GPa.

Effects of propranolol on heart rate and development in Japanese medaka (Oryzias latipes) and zebrafish (Danio rerio)

Propranolol is a β-adrenergic receptor antagonist (β-blocker) that is frequently used to treat hypertension and other cardiovascular conditions in humans. Detected in surface waters due to discharge of domestic wastewater, propranolol has demonstrated significant species differences in toxicity between fish. The aim of this study was to investigate the effects of propranolol on heart rate and development in embryos of two species of fish; Japanese medaka (JM) Oryzias latipes and zebrafish (ZF) Danio rerio. Parents and fertilized embryos of each species were exposed to nominal (measured) concentrations of 0.1 (0.09), 1 (1.1) and 10 (8.3) μg/L of propranolol. Heart rate was monitored during subsequent exposure in embryos at incremental developmental periods (44, 54, 64h post-fertilization (hpf) for ZF and 68, 116, 164 hpf for JM). Heart development and morphology was examined using whole mount immunostaining with distance measurements between the sinus venosus (SV) and bulbus arteriosis (BV). Morphological measurements were made at 44 hpf for ZF and 164 hpf for JM. In ZF, a significant reduction in heart rate was observed at 0.08μg/L propranolol, along with an increase in the SV–BA distance at 44 hpf. Significant reductions in heart rate were also observed in ZF at 54 and 64 hpf at all concentrations of propranolol. For JM, heart rates generally decreased at all developmental timepoints (68, 116 and 164 hpf) after propranolol treatment, with concentration dependent decreases observed at 164 hpf and a lowest observed effect concentration (LOEC) of 0.09μg/L propranolol at each timepoint. However, significant alterations in cardiac morphology were not observed in JM at 164 hpf. In contrast, heart rates and morphology in ZF were affected with a non-monotonic concentration response in morphology and a LOEC of 0.09μg/L propranolol for morphological alterations at 44 hpf and for heart rate at each timepoint. These data indicated unique developmental stages of susceptibility between species and that combined parental and embryo exposures may lead to greater impairment of cardiac development and function in offspring than separate exposures of adults and embryos.

A one-dimensional barium(II) coordination polymer with a coordinated nitro group of 2-nitrobenzoate

The aqueous reaction of barium carbonate with 2-nitrobenzoic acid (2-nbaH) results in the formation of a one-dimensional coordination polymer, catena-poly[[hexa(aqua)dibarium(II)]bis[(μ 2-2-nitrobenzoate-O,O,O-NO2)(μ 2-2-nitrobenzoate-O,O,O′)]] 1. On heating at 100°C compound 1 is dehydrated to anhydrous barium bis(2-nitrobenzoate) 2. The anhydrous compound can be re-hydrated to 1 on exposure to water vapour. Compounds 1 and 2 were characterized by elemental analysis, IR and UV-Vis spectra, DSC thermograms, weight loss studies and the structure of 1 was determined. 1 and 2 can be thermally decomposed to BaCO3 by heating at 800°C. The polymer [[Ba(H2O)3]2(μ 2-2-nba-O,O,O-NO2)2 (μ 2-2-nba-O,O,O′)2] n 1 crystallizes in the centrosymmetric triclinic space group Pī and all atoms are located in general positions. The polymeric structure is based on a dimeric unit and consists of three water molecules coordinated to a central Ba(II) and two unique 2-nitrobenzoate (2-nba) anions, one of which (μ 2-2-nba-O,O,O-NO2) functions as a tridentate ligand and is linked to a Ba(II) through the oxygen atom of the-NO2 group and forms a monoatomic μ 2-carboxylate bridge between two symmetry related Ba(II) ions with a Ba···Ba distance of 4·5726(14) Å. The second unique 2-nba anion (μ 2-2-nba-O,O,O′) also functions as a tridentate ligand with the carboxylate oxygen atoms linked to a Ba(II) ion in a bidentate fashion and one of the carboxylate oxygen atoms forming a monoatomic bridge between two symmetry related Ba(II) ions resulting in a Ba···Ba separation of 4·5406(15) Å. These differing tridentate 2-nba ligands link {Ba(H2O)3} units into a one-dimensional polymeric chain extending along b axis. In the infinite chain each nine coordinated Ba(II) is bonded to three water molecules and further linked to six oxygen atoms of four different 2-nitrobenzoate anions with alternating pairs of Ba(II) ions in the chain bridged by a pair of (μ 2-2-nba-O,O,O-NO2) and (μ 2-2-nba-O,O,O′) ligands resulting in alternating Ba···Ba distances of 4·5406(15) and 4·5726(14) Å across the chain.

Catena-Poly[[(pentaaqua)(4-nitrobenzoato-O,O’)barium(II)] (μ-4-nitrobenzoato-O,O’)]: A barium(II) coordination polymer showing O-H⋯O and C-H⋯O interactions

The reaction of barium carbonate with 4-nitrobenzoic acid (4-nbaH) results in the formation of a Ba(II) coordination polymer, catena-poly[[(pentaaqua)(4-nitrobenzoato-O,O’)barium(II)](μ-4-nitrobenzoato-O,O’)] 1. The polymeric compound [[Ba(H2O)5(4-nba-O,O’)](μ-4-nba-O,O’)] n 1 was characterized by elemental analysis, IR and UV-Vis spectra, weight loss studies, X-ray powder diffraction and its structure determined. In 1 five water molecules are coordinated to the central metal and one of the 4-nba ligands is bonded to Ba(II) in a bidentate manner (4-nba-O,O’) through the carboxylate O atoms. The [(pentaaqua)(4-nitrobenzoato-O,O’)barium(II)] units are linked into an infinite one-dimensional chain along b-axis with the aid of the second 4-nba anion, which functions as a bridging bidentate (μ-4-nba-O,O’) ligand. This results in nine coordination around each Ba(II) ion in the coordination polymer. A long Ba⋯Ba distance of 6.750(1) Å is observed between adjacent Ba(II) ions in the chain and the oxygen atoms of the carboxylate group and the nitro functionalities of the 4-nba ligand are involved in several O-H⋯O and C-H⋯O interactions.

Catena-Poly[[aquabarium(II)]-μ-aqua-bis(μ-2′-carboxybiphenyl-2-carboxylato)

In the title compound, [Ba{HOOC(C(6)H(4))(2)CO(2)}(2)(H(2)O)(2)] or [Ba(C(14)H(9)O(4))(2)(H(2)O)(2)], the Ba atoms are coordinated by nine O atoms, six from two 2'-carboxybiphenyl-2-carboxylate (Hbpdc(-)) ligands and three from three coordinated water molecules, resulting in the formation of face-sharing distorted monocapped square antiprisms. The Hbpdc(-) ligands bridge the Ba atoms to form a one-dimensional helical polymer, with a Ba...Ba distance across the chain of 4.1386 (17) A. Adjacent chains are parallel to each other. The two independent ligands are tetradentate and have the same coordination mode, exhibiting mu-oxo bridges and eta(8)-chelation. The crystal structure is further stabilized by hydrogen bonds within each chain.

Strukturen von polaren Bariumorganylen: Synthese und Struktur von Ether‐, Pyridin‐ und Kronenether‐Addukten des Bis(fluorenyl)bariums

AbstractThe synthesis and structure of six bis(fluorenyl)barium complexes is reported. Bis(fluorenyl)barium (1) was synthesized from barium bis(hexamethyldisilazide) and fluorene. Tetrahydrofuran, dimethoxyethane, and pyridine containing complexes (1a, 1b, 2, and 3a) could be synthesized by crystallizing 1 from THF, DME, or pyridine. The X‐ray structures of all crystalline compounds reveal a bent‐sandwich structure with Ba–C distances between 303.3 and 322.2 pm to the five‐membered rings of the fluorenyl ligands and a ring centroid–Ba distance of 288.2 to 289.0 pm. The ring centroid–Ba–ring centroid angles are 134.8 to 137.0°. Three THF (1a, 1b), two DME (2), or three pyridine molecules (3a) complete the coordination sphere of the barium atom. Two crown ether complexes (4a and 5a) of bis(fluorenyl)barium were synthesized by reacting 1 with the crown ethers 18‐crown‐6 and dibenzo‐18‐crown‐6. From pyridine as solvent the following two compounds could be obtained in single crystals: [Ba(C13H9)(18‐crown‐6)(pyridine)]+[C13H9]−·pyridine (4a) and [Ba(C13H9)(dibenzo‐18‐crown‐6)(pyridine)]+[C13H9]−·2 pyridine (5a). The structures of 4a and 5a could be determined by X‐ray diffraction, too. The complexes 4a and 5a have a salt‐like structure with a complex [Ba(C13H9)(18‐crown‐6)(pyridine)]+‐cation and a free fluorenide anion.

Strukturen von polaren Bariumorganylen: Synthese und Struktur von Pyridinund Kronenether-Addukten des Bis(indenyl)bariums

The synthesis and structure of six bis(fluorenyl)barium complexes is reported. Bis(fluorenyl)barium (1) was synthesized from barium bis(hexamethyldisilazide) and fluorene. Tetrahydrofuran, dimethoxyethane, and pyridine containing complexes (1a, 1b, 2, and 3a) could be synthesized by crystallizing 1 from THF, DME, or pyridine. The X-ray structures of all crystalline compounds reveal a bent-sandwich structure with Ba–C distances between 303.3 and 322.2 pm to the five-membered rings of the fluorenyl ligands and a ring centroid–Ba distance of 288.2 to 289.0 pm. The ring centroid–Ba–ring centroid angles are 134.8 to 137.0°. Three THF (1a, 1b), two DME (2), or three pyridine molecules (3a) complete the coordination sphere of the barium atom. Two crown ether complexes (4a and 5a) of bis(fluorenyl)barium were synthesized by reacting 1 with the crown ethers 18-crown-6 and dibenzo-18-crown-6. From pyridine as solvent the following two compounds could be obtained in single crystals: [Ba(C13H9)(18-crown-6)(pyridine)]+[C13H9]−·pyridine (4a) and [Ba(C13H9)(dibenzo-18-crown-6)(pyridine)]+[C13H9]−·2 pyridine (5a). The structures of 4a and 5a could be determined by X-ray diffraction, too. The complexes 4a and 5a have a salt-like structure with a complex [Ba(C13H9)(18-crown-6)(pyridine)]+-cation and a free fluorenide anion.

Unique Barium Selenostannate−Selenide: Ba7Sn3Se13 (and Its Variants Ba7Sn3Se13-δTeδ) with SnSe4 Tetrahedra and Isolated Se Anions

The new selenostannate−selenide Ba7Sn3Se13 and its quaternary substitution variants Ba7Sn3Se13-δTeδ were prepared from the elements at 900 °C followed by slow cooling to 200 °C. Ba7Sn3Se13 crystallizes in the orthorhombic space group Pnma, with lattice parameters of a = 12.748(1) Å, b = 24.891(3) Å, c = 9.212(1) Å, and V = 2923.0(5) Å3 (Z = 4). The structure motifs include Ba2+ cations, isolated SnSe4 tetrahedra, and isolated Se2- anions that are not bonded to any Sn atom. Partial Se/Te replacements are possible up to 2.24(2) of the 13 Se atoms, and the Te atoms prefer the naked site, surrounded by six Ba2+ cations, as well as the site with the longest Se−Ba distances. The Se/Te substitution leads to a smaller band gap as computed with the LMTO approximation, which becomes visible by the gradual darkening of the red color with increasing Te content.

Spectroscopic characterization of alkaline earth uranyl carbonates

A series of alkaline uranyl carbonates, M[UO 2(CO 3) 3]· nH 2O ( M=Mg 2, Ca 2, Sr 2, Ba 2, Na 2Ca, and CaMg) was synthesized and characterized by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after nitric acid digestion, X-ray powder diffraction (XRD), and thermal analysis (TGA/DTA). The molecular structure of these compounds was characterized by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). Crystalline Ba 2[UO 2(CO 3) 3]·6H 2O was obtained for the first time. The EXAFS analysis showed that this compound consists of (UO 2)(CO 3) 3 clusters similar to the other alkaline earth uranyl carbonates. The average U–Ba distance is 3.90±0.02 Å.Fluorescence wavelengths and life times were measured using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The U–O bond distances determined by EXAFS, TRLFS, XPS, and Raman spectroscopy agree within the experimental uncertainties. The spectroscopic signatures observed could be useful for identifying uranyl carbonate species adsorbed on mineral surfaces.

On the mechanism of superconductivity in BaBi(Pb)O 3Ba(K)BiO 3 systems: analysis of XAFS-spectroscopy data

Based on the XAFS-studies of BaPb 1− x Bi x O 3 (BPB) and Ba 1− x K x BiO 3 (BKB) systems carried out by the author from 1983 to 1996, the peculiarties of the local and the electronic structures of both compounds have been explained. It was shown that bismuth in BaBiO 3 is situated in two different positions with valence states Bi 3+ and Bi 3+ L 2 (here L 2 denotes the presence of two holes in the nearest oxygen environment), that causes subsequent difference in BiO bond strengths. Temperature dependent X-ray absorption investigations on the Bi L 3 edge point out significant local structure anomalies around Bi atoms in BaBiO 3 and BaPb 0.25Bi 0.75O 3 at low temperatures. It was found that BiO, BiBa distances abnormally increase with temperature decreasing from ∼90 K. These anomalies are accompanied by abnormal behaviour of the Debye-Waller factor σ 2 of the BiO bonds at low temperatures in contrast to the Einstein model. The nature of the above anomalies was explained in the frame of the model, taking into account the asymmetry of oxygen octahedra rotation modes which promotes understanding of the mechanism of superconductivity in BPB-BKB systems.

Local structure anomalies of the BaBi(Pb)O 3 system at low temperatures: an X-ray absorption study

Temperature dependent X-ray absorption investigations were made on the Bi L 3 edge in BaPb 1− x Bi x O 3 with x = 0.0, 0.75 and 1.0. Essential local structure anomalies around Bi atoms were observed in BaBiO 3 and BaPb 0.25Bi 0.75O 3 at low temperatures. It is found that BiO, BiBa distances abnormally increase with the temperature decreasing from 90 K. These anomalies are accompanied by an abnormal behaviour of the Debye-Waller factor σ 2 of the BiO bonds at low temperatures in contrary to the Einstein model. The lengths and σ 2 of the PbO and PbBa bonds of BaPbO 3 show an ordinary increase with temperature. The anomalies are shown to be due to the rotation distortion asymmetry of the oxygen octahedra owing to the difference in the strength of BiO bonds. The experimental results are discussed in the frame of the dynamic fluctuation rotation mode.

Distorted chain sites for Co- and Fe-substituted YBa2Cu3O7- delta.

We present x-ray-absorption fine-structure (XAFS) measurements for a series of Co- and Fe-substituted samples of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Y-Ba-Cu-O). Our analysis of the first- and second-neighbor environments indicates that the Co atoms primarily replace the Cu in the chain sites, the Cu(1) atoms, in Y-Ba-Cu-O, but many of these Co(1) sites and their neighboring oxygen sites are highly distorted. The first-neighbor Co-O peak consists of \ensuremath{\sim}3.5 oxygen at 1.8 \AA{} and \ensuremath{\sim}1.3 oxygen at 2.4 \AA{}, while the second-neighbor multipeak in the XAFS data is unexpectedly low in amplitude. Structure in this peak is inconsistent with a simple Gaussian broadening and indicates that several Co(1)-Ba distances exist. We propose an aggregation of the Co atoms into distorted, zigzag chains along the $〈110〉$ directions, with some of the Co displaced off center by \ensuremath{\sim}0.4 \AA{} along a perpendicular $〈110〉$ direction. This model is consistent with the second-neighbor XAFS data, provides an explanation for the tetragonal structure via twinning on a microscopic scale, and accommodates excess oxygen within the Co chains. The Fe data suggest that similar chains also exist in the Fe-substituted samples. There are, however, some differences between the local environments of the Fe and Co. The primary difference is that a small but significant number of Fe atoms occupy the Cu(2) plane sites while no appreciable number of Co atoms are found on the Cu(2) sites in the more dilute samples. Finally, near-edge measurements on the Co and Fe $K$-absorption edges indicate that the valence is primarily +3, but a mixture of valences exists. For Co, the edge position corresponds to a mixture of +2 and +3 valences, while Fe exists in a mixture of +2, +3, and +4 states.

Temperature dependence of the local structure of YBa2Cu3O7- delta with varying oxygen content: An x-ray-absorption study.

The local structure of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathrm{y}}$ determined using x-ray-absorption fine structure (XAFS) agrees well with the long-range order given by diffraction results for both oxygen-rich, orthorhombic (y=6.98 and 6.87) and oxygen-deficient, tetragonal (y=6.15) compounds. The x-ray-absorption near-edge structure supports the conclusion that, as y=7 goes to y=6, the O is removed from the chains and the chain Cu atoms, Cu(1), becomes monovalent with a linear O-Cu-O structural configuration and a 3${d}^{10}$ electronic configuration, as in ${\mathrm{Cu}}_{2}$O. For the XAFS analysis, structural standards were determined, and these standards worked well not only for the Cu first-neighbor O environment but also for the Cu second-neighbor metal-atom environment out to 4 A\r{}. A detailed multipeak analysis reproduced the XAFS spectra well and yielded structural parameters that agree with diffraction. The temperature dependence of the structural parameters shows only a smooth variation, with no significant anomalies. The Cu-X distances have a negligible to a small positive change with temperature, consistent with the lattice expansion. The exception is the Cu-Ba distances which change substantially; the Cu(1)-Ba distance increases and the Cu(2)-Ba distance decreases. This indicates that the Ba moves away from the Cu(1)-O chains and toward the Cu(2)-O planes with increasing temperature and that anharmonicity plays a role. This motion is larger for the oxygen-depleted compound than for the fully oxygenated material. The in-plane Cu-O first-neighbor vibrations exhibit no significant softening with temperature. They agree well with a harmonic, Einstein oscillator model which shows that the Cu-O bonds are tightly bound (characteristic Einstein temperatures ${\mathrm{FTHETA}}_{E}$=596\ifmmode\pm\else\textpm\fi{}20 K) and are slightly softer by 6% in the oxygen-deficient, tetragonal material.

Structure of ErBa2Cu3Ox in the Composition Range 6.1 < x < 7.0

ABSTRACTThe structure of a series of homogeneous ErBa2Cu3Ox powder samples (6.1 &lt; x &lt; 7.0) has been determined by elastic neutron scattering using the Rietveld method of profile refinement. All samples were prepared in the same way using a defined absorption-desorption method.By removing oxygen the c axis expands, whilst the Cu2–Cu2 and the Ba–Ba distances contract. Accordingly, the most significant changes in atomic distances occur between the Cu2–O2,3 planes and the Cul–O4–Cul chains. With decreasing oxygen content the distance between the Cu–O planes and the Cu–O–Cu chains increases and the oxygen (0, 0, z) apex atom O1 moves closer to the Cu–O–Cu chains withdrawing from the Cu–O planes. The O1–plane and O1–chain distances are monotonic functions of the oxygen content, but the x dependence of these bonding lengths seems to be much stronger below x &lt; 6.5. The change of the interatomic distances can be correlated to the suppression of superconductivity which clearly occurs within the orthorhombic phase.