Overlap corrections for emissivity calculations of H2O-CO2-CO-N2 mixtures

NASA Astrophysics Data System (ADS)

Alberti, Michael; Weber, Roman; Mancini, Marco

2018-01-01

Calculations of total gas emissivities of gas mixtures containing several radiatively active species require corrections for band overlapping. In this paper, we generate such overlap correction charts for H2O-CO2-N2, H2O-CO-N2, and CO2-CO-N2 mixtures. These charts are applicable in the 0.1-40 bar total pressure range and in the 500 K-2500 K temperature range. For H2O-CO2-N2 mixtures, differences between our charts and Hottel's graphs as well as models of Leckner and Modak are highlighted and analyzed.

Decreased N2O reduction by low soil pH causes high N2O emissions in a riparian ecosystem.

PubMed

Van den Heuvel, R N; Bakker, S E; Jetten, M S M; Hefting, M M

2011-05-01

Quantification of harmful nitrous oxide (N(2)O) emissions from soils is essential for mitigation measures. An important N(2)O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N(2)O emissions and soil pH has yet been established because also the relative contribution of N(2)O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N(2)O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO(3)(-) reduction, N(2)O production and reduction and N(2) production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N(2)O emissions were carried out. In incubations, NO(3)(-) reduction and N(2) production rates increased with pH and net N(2)O production rate was highest at pH 5. N(2)O reduction to N(2) was halted until NO(3)(-) was depleted at low pH values, resulting in a built up of N(2)O. As a consequence, N(2)O:N(2) production ratio decreased exponentially with pH. N(2)O reduction appeared therefore more important than N(2)O production in explaining net N(2)O production rates. In the field, a negative exponential relationship for soil pH against N(2)O emissions was observed. Soil pH could therefore be used as a predictive tool for average N(2)O emissions in the studied ecosystem. The occurrence of low pH spots may explain N(2)O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils. © 2011 Blackwell Publishing Ltd.

Hydrazinium lanthanide oxalates: synthesis, structure and thermal reactivity of N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce, Nd.

PubMed

De Almeida, Lucie; Grandjean, Stéphane; Rivenet, Murielle; Patisson, Fabrice; Abraham, Francis

2014-03-28

New hydrazinium lanthanide oxalates N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce (Ce-HyOx) and Nd (Nd-HyOx), were synthesized by hydrothermal reaction at 150 °C between lanthanide nitrate, oxalic acid and hydrazine solutions. The structure of the Nd compound was determined from single-crystal X-ray diffraction data, space group P2₁/c with a = 16.315(4), b = 12.127(3), c = 11.430(2) Å, β = 116.638(4)°, V = 2021.4(7) Å(3), Z = 4, and R1 = 0.0313 for 4231 independent reflections. Two distinct neodymium polyhedra are formed, NdO9 and NdO8N, an oxygen of one monodentate oxalate in the former being replaced by a nitrogen atom of a coordinated hydrazinium ion in the latter. The infrared absorption band at 1005 cm(-1) confirms the coordination of N2H5(+) to the metal. These polyhedra are connected through μ2 and μ3 oxalate ions to form an anionic three-dimensional neodymium-oxalate arrangement. A non-coordinated charge-compensating hydrazinium ion occupies, with water molecules, the resulting tunnels. The N-N stretching frequencies of the infrared spectra demonstrate the existence of the two types of hydrazine ions. Thermal reactivity of these hydrazinium oxalates and of the mixed isotypic Ce/Nd (CeNd-HyOx) oxalate were studied by using thermogravimetric and differential thermal analyses coupled with gas analyzers, and high temperature X-ray diffraction. Under air, fine particles of CeO2 and Ce(0.5)Nd(0.5)O(1.75) are formed at low temperature from Ce-HyOx and CeNd-HyOx, respectively, thanks to a decomposition/oxidation process. Under argon flow, dioxymonocyanamides Ln2O2CN2 are formed.

Theoretical study of the interaction of N/sub 2/ with water molecules. (H/sub 2/O)/sub n/:N/sub 2/, n = 1--8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtiss, L.A.; Eisgruber, C.L.

1984-03-01

Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H/sub 2/O molecule with N/sub 2/. The potential energy surface for H/sub 2/O:N/sub 2/ is found to have a minimum corresponding to a HOH xxx N/sub 2/ structure with a weak (<2 kcal mol/sup -1/) hydrogen bond. A second, less stable, configuration corresponding to a H/sub 2/O xxx N/sub 2/ structure with N/sub 2/ bonded side on to the oxygen of H/sub 2/O was found to be either a minimum or a saddle point in the potential energy surface depending on themore » level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H/sub 2/O molecules with N/sub 2/. Two types of clusters, one containing only HOH xxx N/sub 2/ interactions and the other containing both HOH xxxN/sub 2/ and H/sub 2/O xxx N/sub 2/ interactions, were investigated for (N/sub 2/:(H/sub 2/O)/sub n/, n = 2--8).« less

Adsorption of H2O, H2, O2, CO, NO, and CO2 on graphene/g-C3N4 nanocomposite investigated by density functional theory

NASA Astrophysics Data System (ADS)

Wu, Hong-Zhang; Bandaru, Sateesh; Liu, Jin; Li, Li-Li; Wang, Zhenling

2018-02-01

Motivated by the photocatalytic reactions of small molecules on g-C3N4 by these insights, we sought to explore the adsorption of H2O and CO2 molecules on the graphene side and H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side of hybrid g-C3N4/graphene nanocomposite using first-principles calculations. The atomic structure and electronic properties of hybrid g-C3N4/graphene nanocomposite is explored. The adsorption of small molecules on graphene/g-C3N4 nanocomposite is thoroughly investigated. The computational studies revels that all small molecules on graphene/g-C3N4 nanocomposite are the physisorption. The adsorption characteristics of H2O and CO2 molecules on the graphene side are similar to that on graphene. The adsorption of H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side always leads to a buckle structure of graphene/g-C3N4 nanocomposite. Graphene as a substrate can significantly relax the buckle degree of g-C3N4 in g-C3N4/graphene nanocomposite.

Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

PubMed Central

Yang, Jingbin; Li, Dongxu; Fang, Yuan

2017-01-01

C-A-S-H (CaO-Al2O3-SiO2-H2O) and N-A-S-H (Na2O-Al2O3-SiO2-H2O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O)/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH)2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH)2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials. PMID

Crystal and molecular structure of Sr{sub 2}(Edta) . 5H{sub 2}O, Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O, and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O strontium ethylenediaminetetraacetates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polyakova, I. N., E-mail: polyakova@igic.ras.ru; Poznyak, A. L.; Sergienko, V. S.

2009-03-15

Three Sr{sup 2+} compounds with the Edta{sup 4-} and H{sub 2}Edta{sup 2-} ligands-Sr{sub 2}(Edta) . 5H{sub 2}O (I), Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O (II), and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O (III)-are synthesized, and their crystal structures are studied. In I, the Sr(1) atom is coordinated by the hexadentate Edta{sup 4-} ligand following the 2N + 4O pattern and by two O atoms of the neighboring ligands, which affords the formation of zigzag chains. The Sr(2) atom forms bonds with O atoms of five water molecules and attaches itself to a chain via bonds with threemore » O atoms of the Edta{sup 4-} ligands. The Sr(1)-O and Sr(2)-O bond lengths fall in the ranges 2.520(2)-2.656(3) and 2.527(3)-2.683(2) A, respectively. The Sr(1)-N bonds are 2.702(3) and 2.743(3) A long. In II and III, the H{sub 2}Edta{sup 2-} anions have a centrosymmetric structure with the trans configuration of the planar ethylenediamine fragment. The N atoms are blocked by acid protons. In II, the environment of the Sr atom is formed by six O atoms of three H{sub 2}Edta ligands, two O atoms of water molecules, and an O atom of the bicarbonate ion, which is disordered over two positions. In III, the environment of the Sr atom includes six O atoms of four H{sub 2}Edta{sup 2-} ligands and three O atoms of water molecules. The coordination number of the Sr atoms is equal to 8 + 1. In II and III, the main bonds fall in the ranges 2.534(3)-2.732(2) and 2.482(2)-2.746(3) A, whereas the ninth bond is elongated to 2.937(3) and 3.055(3) A, respectively. In II, all the structural elements are linked into wavy layers. The O-H-O interactions contribute to the stabilization of the layer and link neighboring layers. In III, hydrated Sr{sup 2+} cations and H{sub 2}Edta{sup -} anions form a three-dimensional [Sr{sub 2}(H{sub 2}Edta)(H{sub 2}O){sub 3}]{sub n}{sup 2n+} framework. The Cl{sup -} anions are fixed in channels of the framework by hydrogen bonds with four water

Reactions of hydrated electrons (H2O)n- with carbon dioxide and molecular oxygen: hydration of the CO2- and O2- ions.

PubMed

Balaj, O Petru; Siu, Chi-Kit; Balteanu, Iulia; Beyer, Martin K; Bondybey, Vladimir E

2004-10-04

The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.

(C6N2H16)[Co(H2O)6](SO4)2.2H2O: A new hybrid material based on sulfate templated by diprotonated trans-1,4-diaminocyclohexane

NASA Astrophysics Data System (ADS)

Hamdi, N.; Ngopoh, F. A. I.; da Silva, I.; El Bali, B.; Lachkar, M.

2018-03-01

Employing trans-1,4-diaminocyclohexane (DACH) as template, the new hybrid sulphate (C6N2H16)[Co(H2O)6](SO4)2.2H2O was prepared in solution. Single-crystal X-ray diffraction analysis shows that it crystallizes in the monoclinic system (S.G.: P 21/n), with the following unit-cell parameters (Å,°): a = 6.2897(2), b = 12.3716(6), c = 13.1996(4), β = 98.091(3) V = 1016.89(7) Å3, Z = 4. Its 3D crystal structure is made upon isolated [Co(H2O)6] octahedra, regular [SO4] tetrahedra, protonated DACH and free H2O molecules, which interact through N-H···O and O-H···O hydrogen bonds. The Fourier transform infrared result exhibits bands corresponding to the vibrations of DACH, sulfate group and water molecules. The thermal decomposition of the phase consists mainly in the loss of the organic moiety and one sulfate group, leading thus to the formation of anhydrous cobalt sulfate.

Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

NASA Technical Reports Server (NTRS)

Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

2013-01-01

We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

O2(b1Σg+) Quenching by O2, CO2, H2O, and N2 at Temperatures of 300-800 K.

PubMed

Zagidullin, M V; Khvatov, N A; Medvedkov, I A; Tolstov, G I; Mebel, A M; Heaven, M C; Azyazov, V N

2017-10-05

Rate constants for the removal of O 2 (b 1 Σ g + ) by collisions with O 2 , N 2 , CO 2 , and H 2 O have been determined over the temperature range from 297 to 800 K. O 2 (b 1 Σ g + ) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed by observing the temporal behavior of the b 1 Σ g + -X 3 Σ g - fluorescence. The removal rate constants for CO 2 , N 2 , and H 2 O were not strongly dependent on temperature and could be represented by the expressions k CO2 = (1.18 ± 0.05) × 10 -17 × T 1.5 × exp[Formula: see text], k N2 = (8 ± 0.3) × 10 -20 × T 1.5 × exp[Formula: see text], and k H2O = (1.27 ± 0.08) × 10 -16 × T 1.5 × exp[Formula: see text] cm 3 molecule -1 s -1 . Rate constants for O 2 (b 1 Σ g + ) removal by O 2 (X), being orders of magnitude lower, demonstrated a sharp increase with temperature, represented by the fitted expression k O2 = (7.4 ± 0.8) × 10 -17 × T 0.5 × exp[Formula: see text] cm 3 molecule -1 s -1 . All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.

Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

NASA Astrophysics Data System (ADS)

Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

2016-09-01

An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

Infrared photodissociation spectroscopy of H(+)(H2O)6·M(m) (M = Ne, Ar, Kr, Xe, H2, N2, and CH4): messenger-dependent balance between H3O(+) and H5O2(+) core isomers.

PubMed

Mizuse, Kenta; Fujii, Asuka

2011-04-21

Although messenger mediated spectroscopy is a widely-used technique to study gas phase ionic species, effects of messengers themselves are not necessarily clear. In this study, we report infrared photodissociation spectroscopy of H(+)(H(2)O)(6)·M(m) (M = Ne, Ar, Kr, Xe, H(2), N(2), and CH(4)) in the OH stretch region to investigate messenger(M)-dependent cluster structures of the H(+)(H(2)O)(6) moiety. The H(+)(H(2)O)(6), the protonated water hexamer, is the smallest system in which both the H(3)O(+) (Eigen) and H(5)O(2)(+) (Zundel) hydrated proton motifs coexist. All the spectra show narrower band widths reflecting reduced internal energy (lower vibrational temperature) in comparison with bare H(+)(H(2)O)(6). The Xe-, CH(4)-, and N(2)-mediated spectra show additional band features due to the relatively strong perturbation of the messenger. The observed band patterns in the Ar-, Kr-, Xe-, N(2)-, and CH(4)-mediated spectra are attributed mainly to the "Zundel" type isomer, which is more stable. On the other hand, the Ne- and H(2)-mediated spectra are accounted for by a mixture of the "Eigen" and "Zundel" types, like that of bare H(+)(H(2)O)(6). These results suggest that a messenger sometimes imposes unexpected isomer-selectivity even though it has been thought to be inert. Plausible origins of the isomer-selectivity are also discussed.

Synthesis, crystal structure and thermal study of the hybrid nickel sulfate: C6N2H16[Ni(H2O)6(SO4)2].2H2O

NASA Astrophysics Data System (ADS)

Ngopoh, F. A. I.; Hamdi, N.; Chaouch, S.; Lachkar, M.; da Silva, I.; El Bali, B.

2018-03-01

A new inorganic-organic hybrid open framework nickel sulfate C6N2H16[Ni(H2O)6(SO4)2].2H2O has been synthesized by slow evaporation in aqueous solution using trans-1,4-diaminocyclohexane as structure-directing agent. It was characterized by single-crystal X-ray diffraction, infrared spectroscopy and analyzed by TGA-DSC. The compound crystallizes in the monoclinic space group P21/n, with the unit cell parameters of a = 6.2586 Å, b = 12.3009 Å, c = 13.2451 Å, β = 98,047°, Z = 4. Its crystal structure consists of isolated polyhedrons [Ni(H2O)6]2+ and [SO4]2- and free water which connects through hydrogen bonds. This association results in the porous framework where the protonated organic molecule trans-1,4-diaminocyclohexane is located as a counter ion. The IR spectra Shows the bands corresponding to the sulfate anion, water molecule and diprotonated trans-1-4-diaminocyclohexane. Thermal study indicates the loss of water molecules and the degradation of trans-1-4-diaminocyclohexane.

Hierarchical Honeycomb Br-, N-Codoped TiO2 with Enhanced Visible-Light Photocatalytic H2 Production.

PubMed

Zhang, Chao; Zhou, Yuming; Bao, Jiehua; Sheng, Xiaoli; Fang, Jiasheng; Zhao, Shuo; Zhang, Yiwei; Chen, Wenxia

2018-06-06

The halogen elements modification strategy of TiO 2 encounters a bottleneck in visible-light H 2 production. Herein, we have for the first time reported a hierarchical honeycomb Br-, N-codoped anatase TiO 2 catalyst (HM-Br,N/TiO 2 ) with enhanced visible-light photocatalytic H 2 production. During the synthesizing process, large amounts of meso-macroporous channels and TiO 2 nanosheets were fabricated in massive TiO 2 automatically, constructing the hierarchical honeycomb structure with large specific surface area (464 m 2 g -1 ). cetyl trimethylammonium bromide and melamine played a key role in constructing the meso-macroporous channels. Additionally, HM-Br,N/TiO 2 showed a high visible-light H 2 production rate of 2247 μmol h -1 g -1 , which is far more higher than single Br- or N-doped TiO 2 (0 or 63 μmol h -1 g -1 , respectively), thereby demonstrating the excellent synergistic effects of Br and N elements in H 2 evolution. In HM-Br,N/TiO 2 catalytic system, the codoped Br-N atoms could reduce the band gap of TiO 2 to 2.88 eV and the holes on acceptor levels (N acceptor) can passivate the electrons on donor levels (Br donor), thereby preventing charge carriers recombination significantly. Furthermore, the proposed HM-Br,N/TiO 2 fabrication strategy had a wide range of choices for N source (e.g., melamine, urea, and dicyandiamide) and it can be applied to other TiO 2 materials (e.g., P25) as well, thereby implying its great potential application in visible-light H 2 production. Finally, on the basis of experimental results, a possible photocatalytic H 2 production mechanism for HM-Br,N/TiO 2 was proposed.

2,4-Dinitrophenylhydrazine, redetermined at 120 K: a three-dimensional framework built from N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

PubMed

Wardell, James L; Low, John N; Glidewell, Christopher

2006-06-01

In the title compound, C6H6N4O4, the bond distances indicate significant bond fixation, consistent with charge-separated polar forms. The molecules are almost planar and there is an intramolecular N-H...O hydrogen bond. The molecules are linked into a complex three-dimensional framework structure by a combination of N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

Isotope exchange in reactions between D2O and size-selected ionic water clusters containing pyridine, H+ (pyridine)m(H2O)n.

PubMed

Ryding, Mauritz Johan; Zatula, Alexey S; Andersson, Patrik Urban; Uggerud, Einar

2011-01-28

Pyridine containing water clusters, H(+)(pyridine)(m)(H(2)O)(n), have been studied both experimentally by a quadrupole time-of-flight mass spectrometer and by quantum chemical calculations. In the experiments, H(+)(pyridine)(m)(H(2)O)(n) with m = 1-4 and n = 0-80 are observed. For the cluster distributions observed, there are no magic numbers, neither in the abundance spectra, nor in the evaporation spectra from size selected clusters. Experiments with size-selected clusters H(+)(pyridine)(m)(H(2)O)(n), with m = 0-3, reacting with D(2)O at a center-of-mass energy of 0.1 eV were also performed. The cross-sections for H/D isotope exchange depend mainly on the number of water molecules in the cluster and not on the number of pyridine molecules. Clusters having only one pyridine molecule undergo D(2)O/H(2)O ligand exchange, while H(+)(pyridine)(m)(H(2)O)(n), with m = 2, 3, exhibit significant H/D scrambling. These results are rationalized by quantum chemical calculations (B3LYP and MP2) for H(+)(pyridine)(1)(H(2)O)(n) and H(+)(pyridine)(2)(H(2)O)(n), with n = 1-6. In clusters containing one pyridine, the water molecules form an interconnected network of hydrogen bonds associated with the pyridinium ion via a single hydrogen bond. For clusters containing two pyridines, the two pyridine molecules are completely separated by the water molecules, with each pyridine being positioned diametrically opposite within the cluster. In agreement with experimental observations, these calculations suggest a "see-saw mechanism" for pendular proton transfer between the two pyridines in H(+)(pyridine)(2)(H(2)O)(n) clusters.

Theoretical studies of UO(2)(OH)(H(2)O)(n) (+), UO(2)(OH)(2)(H(2)O)(n), NpO(2)(OH)(H(2)O)(n), and PuO(2)(OH)(H(2)O)(n) (+) (n

PubMed

Cao, Zhiji; Balasubramanian, K

2009-10-28

Extensive ab initio calculations have been carried out to study equilibrium structures, vibrational frequencies, and the nature of chemical bonds of hydrated UO(2)(OH)(+), UO(2)(OH)(2), NpO(2)(OH), and PuO(2)(OH)(+) complexes that contain up to 21 water molecules both in first and second hydration spheres in both aqueous solution and the gas phase. The structures have been further optimized by considering long-range solvent effects through a polarizable continuum dielectric model. The hydrolysis reaction Gibbs free energy of UO(2)(H(2)O)(5) (2+) is computed to be 8.11 kcal/mol at the MP2 level in good agreement with experiments. Our results reveal that it is necessary to include water molecules bound to the complex in the first hydration sphere for proper treatment of the hydrated complex and the dielectric cavity although water molecules in the second hydration sphere do not change the coordination complex. Structural reoptimization of the complex in a dielectric cavity seems inevitable to seek subtle structural variations in the solvent and to correlate with the observed spectra and thermodynamic properties in the aqueous environment. Our computations reveal dramatically different equilibrium structures in the gas phase and solution and also confirm the observed facile exchanges between the complex and bulk solvent. Complete active space multiconfiguration self-consistent field followed by multireference singles+doubles CI (MRSDCI) computations on smaller complexes confirm predominantly single-configurational nature of these species and the validity of B3LYP and MP2 techniques for these complexes in their ground states.

Diode laser measurements of linestrength and temperature-dependent lineshape parameters of H2O-, CO2-, and N2-perturbed H2O transitions near 2474 and 2482 nm

NASA Astrophysics Data System (ADS)

Goldenstein, Christopher S.; Jeffries, Jay B.; Hanson, Ronald K.

2013-11-01

Absorption lineshapes for two unresolved H2O doublets near 4029.52 and 4041.92 cm-1 were measured at high-resolution in a heated static cell using two distributed-feedback diode lasers. Measurements were acquired for H2O, CO2, and N2 perturbers over a temperature and pressure range of 650-1325 K and 2-760 Torr, respectively. Strong collisional narrowing effects were observed in CO2 and N2, but not in pure H2O. The Galatry profile was used to infer collisional-broadening and -narrowing coefficients and their respective temperature dependence for CO2 and N2 perturbers. The collisional-broadening and -narrowing coefficients for CO2 perturbers were found to decrease with increasing temperature in a similar manner. For N2 perturbers, the collisional-broadening coefficients increased with temperature while the collisional-narrowing coefficients decreased with increasing temperature. Self-broadening coefficients were inferred from Voigt profile fits and are compared with HITEMP 2010. The linestrengths of 17 H2O transitions are also reported.

Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

PubMed

Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

2006-10-21

Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5< or =n< or =16. Mixed CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers

NASA Technical Reports Server (NTRS)

Okongo, Nora; Bellan, Josette

2004-01-01

This report describes a study of databases produced by direct numerical simulation of mixing layers developing between opposing flows of two fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence, with emphasis on helicity. The simulations were performed for two different fluid pairs -- O2/H2 and C7H16/N2 -- at similar values of reduced pressure.

A Novel Coordination Polymer Constructed by Hetero-Metal Ions and 2,3-Pyridine Dicarboxylic Acid: Synthesis and Structure of [NiNa2(PDC)2(μ-H2O)(H2O)2] n

NASA Astrophysics Data System (ADS)

Dou, Ming-Yu; Lu, Jing

2017-12-01

A novel coordination polymer containing hetero-metal ions, [NiNa2(PDC)2(μ-H2O)(H2O)2] n , where PDC is 2,3-pyridine dicarboxylate ion, has been synthesized. In the structure, the PDC ligand chelates and bridges two Ni(II) and two Na(I) centers. Two kinds of metal centers are connected by μ4-PDC and μ2-H2O to form 2D coordination layers. Hydrogen bonds between coordination water molecules and carboxylate oxygen atoms further link these 2D coordination layers to form 3D supramolecular network.

Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy-ethyl)methylamino]ethanolato-2:1κ(4) O (1),N,O (2):O (1)}[μ-2,2'-(methylimino)diethanolato-1:2κ(4) O,N,O':O]dithiocyanato-1κN,2κN-chromium(III)copper(II).

PubMed

Rusanova, Julia A; Semenaka, Valentina V; Dyakonenko, Viktoriya V; Shishkin, Oleg V

2015-09-01

The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal Cu(II)/Cr(III) complex. The mol-ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio-cyanato ligands. The Cu(II) ion adopts a distorted square-pyramidal coordination while the Cr(III) ion has a distorted octa-hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O-H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two -CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1).

Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

PubMed

Soulard, P; Tremblay, B

2015-12-14

The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

Synthesis of zinc sulfide nanoparticles during zinc oxidization by H2S and H2S/H2O supercritical fluids

NASA Astrophysics Data System (ADS)

Vostrikov, A. A.; Fedyaeva, O. N.; Sokol, M. Ya.; Shatrova, A. V.

2014-12-01

Formation of zinc sulfide nanoparticles was detected during interaction of bulk samples with hydrogen sulfide at supercritical parameters. Synthesis proceeds with liberation of H2 by the reaction nZn + nH2S = (ZnS) n + nH2. It has been found by the X-ray diffraction method, scanning electron microscopy, and mass spectrometry that the addition of water stimulates coupled reactions of nanoparticle synthesis nZn + nH2O = (ZnO) n + nH2 and (ZnO) n + nH2S = (ZnS) n + nH2O and brings about an increase in the synthesis rate and morphological changes of (ZnS) n nanoparticles.

Molecular dynamic simulations of selective self-diffusion of CH4/CO2/H2O/N2 in coal

NASA Astrophysics Data System (ADS)

Song, Y.; Jiang, B.; Li, F. L.

2017-06-01

The self-diffusion coefficients (D) of CH4/CO2/H2O/N2 at a relatively broad range of temperatures(298.15∼ 458.15K)and pressures (1∼6MPa) under the NPT, NPH, NVE, and NVT ensembles were obtained after the calculations of molecular mechanics(MM), annealing kinetics(AK), giant canonical Monte Carlo(GCMC), and molecular dynamics (MD) based on Wiser bituminous coal model (WM). The Ds of the adsorbates at the saturated adsorption configurations are D CH42H2ON2(NPT, 298.15K, 0.1MPa). The diffusion activation energy (E) is E H2O (1.07kJ/mol)N2(1.82kJ/mol)2 (2.94kJ/mol)N2 and H2O to the lowest. The order of different ensembles is D N2 (NVE)< D N2 (NVT)≈D N2 (NPH)≈D N2 (NPT) (T<418K) and D N2 (NVE) is remarkable higher than other ensembles when T>418K. The average swelling ratios manifest as H2O (14.7∼35.18%)>CO2 (13.38∼32.25%)>CH4 (15.35∼23.71%)> N2 (11.47∼22.14%) (NPH, 1∼6MPa). There exits differences in D, swelling ratios and E among various ensembles, indicating that the selection of ensembles has an important influence on the MD calculations for self-diffusion coefficients.

Effects of variation in background mixing ratios of N2, O2, and Ar on the measurement of δ18O-H2O and δ2H-H2O values by cavity ring-down spectroscopy

NASA Astrophysics Data System (ADS)

Johnson, Jennifer E.; Rella, Chris W.

2017-08-01

Cavity ring-down spectrometers have generally been designed to operate under conditions in which the background gas has a constant composition. However, there are a number of observational and experimental situations of interest in which the background gas has a variable composition. In this study, we examine the effect of background gas composition on a cavity ring-down spectrometer that measures δ18O-H2O and δ2H-H2O values based on the amplitude of water isotopologue absorption features around 7184 cm-1 (L2120-i, Picarro, Inc.). For background mixtures balanced with N2, the apparent δ18O values deviate from true values by -0.50 ± 0.001 ‰ O2 %-1 and -0.57 ± 0.001 ‰ Ar %-1, and apparent δ2H values deviate from true values by 0.26 ± 0.004 ‰ O2 %-1 and 0.42 ± 0.004 ‰ Ar %-1. The artifacts are the result of broadening, narrowing, and shifting of both the target absorption lines and strong neighboring lines. While the background-induced isotopic artifacts can largely be corrected with simple empirical or semi-mechanistic models, neither type of model is capable of completely correcting the isotopic artifacts to within the inherent instrument precision. The development of strategies for dynamically detecting and accommodating background variation in N2, O2, and/or Ar would facilitate the application of cavity ring-down spectrometers to a new class of observations and experiments.

Syntheses and structures of [UO2( L)5](ClO4)2 and [U( L')4(H2O)4](ClO4)4 ( L is dimethylformamide, L' is N,N-dimethylcarbamide)

NASA Astrophysics Data System (ADS)

Serezhkin, V. N.; Vologzhanina, A. V.; Pushkin, D. V.; Astashkina, D. A.; Savchenkov, A. V.; Serezhkina, L. B.

2017-09-01

The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [UVIO2(C3H7NO)5](ClO4)2 ( I) and [UIV(C3H8N2O)4(H2O)4](ClO4)4 ( II), where C3H7NO is N,N-dimethylformamide ( Dmfa) and C3H8N2O is N,N-dimethylcarbamide ( a-Dmur), were studied by X-ray diffraction. Complex II and the complex UIV( s-Dmur)4(H2O)4(ClO4)4 ( III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO2( Dmfa)5]2+ and [U( Dmur)4(H2O)4]4+ groups as uranium-containing structural units belonging to the crystal-chemical groups AM 7 1 ( A = UVI, M 1 = O2- and Dmfa) and AM 8 1 ( A = UIV, M 1 = Dmur and H2O) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.

X-ray investigation of molten crystal hydrates H2SO4(nH2O) and HNO3(nH2O)

NASA Technical Reports Server (NTRS)

Romanova, A. V.; Skryshevskiy, A. F.

1979-01-01

Integral analysis of the intensity of the electron density distribution curve in molten crystal hydrates provided by X-ray analysis, permits the following conclusions on the structure of the complex SO and NO ions, and the short-range order in the structure of the solution. The SO4 ion in the solution has a tetrahedral structure with an S to O distance equal to 1.5 A. For the NO3 in the solution, a planar triangular shape is probable, with an N to O distance equal to 1.2 A. Preferential distances between each of the oxygens of the SO ion and the nearest molecules of water proved near to the corresponding distances in solid crystal hydrates. For an (H2SO4)(H2O) solution, the average number of water molecules surrounding each oxygen atom of the SO4 (--) ion was on the order of 1.3 molecules. Hence the preferential distances between the water molecules and the oxygen atoms of the SO ion, and the preference of their mutual position, correspond to the fixed position of these same elements of the structure in the solid crystal hydrate.

Implications of the (H2O)n + CO ↔ trans-HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions for primordial atmospheres of Venus and Earth

NASA Astrophysics Data System (ADS)

Vichietti, R. M.; Spada, R. F. K.; da Silva, A. B. F.; Machado, F. B. C.; Haiduke, R. L. A.

2018-04-01

The forward and backward (H2O)n + CO ↔ HCOOH + (H2O)n-1 (n = 1, 2, and 3) reactions were studied in order to furnish trustworthy thermochemical and kinetic data. Stationary point structures involved in these chemical processes were achieved at the B2PLYP/cc-pVTZ level so that the corresponding vibrational frequencies, zero-point energies, and thermal corrections were scaled to consider anharmonicity effects. A complete basis set extrapolation was also employed with the CCSD(T) method in order to improve electronic energy descriptions and providing therefore more accurate results for enthalpies, Gibbs energies, and rate constants. Forward and backward rate constants were encountered at the high-pressure limit between 200 and 4000 K. In turn, modified Arrhenius' equations were fitted from these rate constants (between 700 and 4000 K). Next, considering physical and chemical conditions that have supposedly prevailed on primitive atmospheres of Venus and Earth, our main results indicate that 85-88 per cent of all water forms on these atmospheres were monomers, whereas (H2O)2 and (H2O)3 complexes would represent 12-15 and ˜0 per cent, respectively. Besides, we estimate that Earth's and Venus' primitive atmospheres could have been composed by ˜0.001-0.003 per cent of HCOOH when their temperatures were around 1000-2000 K. Finally, the water loss process on Venus may have occurred by a mechanism that includes the formic acid as intermediate species.

Chanabayaite, Cu2(N3C2H2)Cl(NH3,Cl,H2O,□)4, a new mineral containing triazolate anion

NASA Astrophysics Data System (ADS)

Chukanov, N. V.; Zubkova, N. V.; Möhn, G.; Pekov, I. V.; Pushcharovsky, D. Yu.; Zadov, A. E.

2015-12-01

A new mineral, chanabayaite, has been discovered at a guano deposit located at Mt. Pabellón de Pica near the village of Chanabaya, Iquique Province, Tarapacá region, Chile. It is associated with salammoniac, halite, joanneumite, nitratine and earlier chalcopyrite. Chanabayaite occurs as blue translucent imperfect prismatic crystals, up to 0.05 × 0.1 × 0.5 mm in size, and their radial aggregates. Chanabayaite is brittle, with a Mohs' hardness of 2. The cleavage is perfect on (001) and imperfect on (100) and (010). D meas = 1.48(2) g/cm3, D calc = 1.464 g/cm3. The mineral is optically biaxial (-), α = 1.561(2), β = 1.615(3), γ = 1.620(2), 2 V meas = 25(10)°, 2 V calc = 33°. Pleochroism is strong, Z ≈ Y (deep blue) ≫ X (pale blue with gray tint). IR spectrum is given. The chemical composition (electron microprobe data for Cu, Fe and Cl; gas chromatography data for H, N, C and O) is as follows (wt %): 32.23 Cu, 1.14 Fe, 16.13 Cl, 3.1 H, 29.9 N, 12.2 C, 3.4 O, total is 98.1. The empirical formula is ( Z = 4): Cu1.92Fe0.08Cl1.72N8.09C3.85H11.66O0.81. The structural model was based on the single-crystal X-ray diffraction data ( R = 0.1627). Chanabayaite is orthorhombic, space group Imma, a = 19.484(3), b = 7.2136(10), c = 11.999(4) Å, V = 1686.5(7) Å3, Z = 2. In chanabayaite, chains of the corner-sharing Cu(l)-centered octahedra and single Cu(2)-centered octahedra are linked via 1,2,4-triazolate anions C2N3H2 -. NH3 and Cl- are additional ligands coordinating Cu2+. Chanabayaite is a transformational mineral species formed by leaching of Na and one third of Cl and partial dehydration of the protophase Na2Cu2Cl3(N3C2H2)2(NH3)2 • 4H2O. The strongest reflections in the powder X-ray diffraction pattern [ d, Å ( I, %) ( hkl)] are detected: 10.19 (100) (101), 6.189 (40) (011), 5.729 (23) (301), 5.216 (75) (211, 202), 4.964 (20) (400), 2.830 (20) (602, 413, 503), 2.611 (24) (123, 422, 404).

Empirical electronic polarizabilities: deviations from the additivity rule. I. M2+SO4·nH2O, blödite Na2M2+(SO4)2·4H2O, and kieserite-related minerals with sterically strained structures

NASA Astrophysics Data System (ADS)

Gagné, Olivier; Hawthorne, Frank; Shannon, Robert D.; Fischer, Reinhard X.

2017-09-01

Empirical electronic polarizabilities allow the prediction of total mineral polarizabilities and mean refractive indices of the vast majority of minerals and synthetic oxides. However, deviations from the valence-sum rule at cations in some minerals are associated with large deviations of observed from calculated total polarizabilities. We have identified several groups of minerals and compounds where deviations from the valence-sum rule at cations lead to polarizability deviations of 2-5%: M(SO4)·nH2O, n = 1-6, blödite-group minerals [Na2M2+(SO4)2·4H2O], and the kieserite-related minerals: isokite, panasqueiraite and tilasite. In these minerals, the environment of the M ions contains both O and H2O: Mg[O4(H2O)2] in kieserite, szmikite, and szomolnokite; Mg[O2(H2O)4] in starkeyite, ilesite, and rozenite, and Mg[(H2O)6] in hexahydrite. In compounds where the ligands are only H2O, deviations from the valence-sum rule at the M(H2O)6 groups are not accompanied by significant polarizability deviations. This is the case for epsomite, MgSO4·7H2O; bieberite, CoSO4·7H2O; goslarite, ZnSO4·7H2O, six silicofluorides, MSiF6·6H2O; eighteen Tutton's salts, M2M'(SO4)2·6H2O, where M = K, Rb, Cs and M' = Mg, Mn, Fe, Co, Ni, Cu, and Zn; and eleven MM'(SO4)2·12H2O alums, where M = Na, K, Rb and Cs, and M' = Al, Cr, Ga and In. This is also the case for the sulfates alunogen, Al2(SO4)3·17H2O and halotrichite, FeAl2(SO4)4·22H2O; three hydrated nitrates; one phosphate; three antimonates and two hydrated perchlorates. A possible explanation for this different behavior is that the bond-valence model treats O and H separately, whereas polarizability calculations treat the polarizability of the entire H2O molecule.

Synthesis and characterization of polymer eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O as well as the interaction of [Y III(pdta)(H 2O)] 22- with BSA

NASA Astrophysics Data System (ADS)

Liu, Bin; Wang, Jun; Wang, Xin; Liu, Bing-Mi; He, Ling-Ling; Xu, Shu-Kun

2010-12-01

The eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O (en = ethylenediamine and H 4pdta = 1,3-propylenediamine- N, N, N', N'-tetraacetic acid) was synthesized, meanwhile its molecular and crystal structures were determined by single-crystal X-ray diffraction technology. The interaction between [Y III(pdta)(H 2O)] 22- and bovine serum albumin (BSA) was investigated by UV-vis and fluorescence spectra. The results indicate that [Y III(pdta)(H 2O)] 22- quenched effectively the intrinsic fluorescence of BSA via a static quenching process with the binding constant ( Ka) of the order of 10 4. Meanwhile, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. Results indicate that the hydrophobic environments around Trp and Tyr residues were all slightly changed. The thermodynamic parameters (Δ G = -25.20 kJ mol -1, Δ H = -26.57 kJ mol -1 and Δ S = -4.58 J mol -1 K -1) showed that the reaction was spontaneous and exothermic. What is more, both Δ H and Δ S were negative values indicated that hydrogen bond and Van der Waals forces were the predominant intermolecular forces between [Y III(pdta)(H 2O)] 22- and BSA.

One-dimensional ferromagnetic array compound [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate)

NASA Astrophysics Data System (ADS)

Honda, Zentaro; Nomoto, Naoyuki; Fujihara, Takashi; Hagiwara, Masayuki; Kida, Takanori; Sawada, Yuya; Fukuda, Takeshi; Kamata, Norihiko

2018-06-01

We report on the syntheses, crystal structure, and magnetic properties of the transition metal coordination polymer [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate) in which CoO6 octahedra are linked through their edges, forming one-dimensional (1D) Co(II) arrays running along the crystal a-axis. These arrays are further perpendicularly bridged by SBA ligand to construct a three-dimensional framework. Its magnetic properties have been investigated, and ferromagnetic interactions within the arrays have been found. From heat capacity measurements, we have found that this compound exhibits a three-dimensional ferromagnetic phase transition at TC = 1.54 K, and the specific heat just above TC shows a Schottky anomaly which originates from an energy gap caused by uniaxial magnetic anisotropy. These results suggest that [Co3(SBA)2(OH)2(H2O)2]n consists of weakly coupled 1D ferromagnetic Ising arrays.

Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy­ethyl)methylamino]ethanolato-2:1κ4 O 1,N,O 2:O 1}[μ-2,2′-(methylimino)diethanolato-1:2κ4 O,N,O′:O]dithiocyanato-1κN,2κN-chromium(III)copper(II)

PubMed Central

Rusanova, Julia A.; Semenaka, Valentina V.; Dyakonenko, Viktoriya V.; Shishkin, Oleg V.

2015-01-01

The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal CuII/CrIII complex. The mol­ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio­cyanato ligands. The CuII ion adopts a distorted square-pyramidal coordination while the CrIII ion has a distorted octa­hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O—H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two –CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1). PMID:26396853

Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetra­hydrate {di-μ-aqua-bis­(tri­aqua­diperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nona­hydrate {hepta­aqua­diperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetra­hydrate consist of Sr2+ cations coordinated by five water mol­ecules and four O atoms of four perchlorate tetra­hedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water mol­ecules and thus forming chains parallel to [100]. In the tetra­hydrate, dimers of two [SrO9] polyhedra connected by two sharing water mol­ecules are formed. The structure of the nona­hydrate contains one Sr2+ cation coordinated by seven water mol­ecules and by two O atoms of two perchlorate tetra­hedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water mol­ecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ClO4 tetra­hedra and water mol­ecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures. PMID:25552979

{μ-2-[(3-Amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1:2κ(5)O(1),O(6):N,N',O(1)}{2-[(3-amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1κ(3)N,N',O(1)}-μ-azido-1:2κ(2)N:N-azido-2κN-methanol-2κO-dinickel(II).

PubMed

Ghaemi, Akbar; Rayati, Saeed; Fayyazi, Kazem; Ng, Seik Weng; Tiekink, Edward R T

2012-08-01

Two distinct coordination geometries are found in the binuclear title complex, [Ni(2)(C(13)H(19)N(2)O(2))(2)(N(3))(2)(CH(3)OH)], as one Schiff base ligand is penta-dentate, coordinating via the anti-cipated oxide O, imine N and amine N atoms (as for the second, tridentate, ligand) but the oxide O is bridging and coordination also occurs through the meth-oxy O atom. The Ni(II) atoms are linked by a μ(2)-oxide atom and one end of a μ(2)-azide ligand, forming an Ni(2)ON core. The coordination geometry for the Ni(II) atom coordinated by the tridentate ligand is completed by the meth-oxy O atom derived from the penta-dentate ligand, with the resulting N(3)O(3) donor set defining a fac octa-hedron. The second Ni(II) atom has its cis-octa-hedral N(4)O(2) coordination geometry completed by the imine N and amine N atoms of the penta-dentate Schiff base ligand, a terminally coordinated azide N and a methanol O atom. The arrangement is stabilized by an intra-molecular hydrogen bond between the methanol H and the oxide O atom. Linear supra-molecular chains along the a axis are formed in the crystal packing whereby two amine H atoms from different amine atoms hydrogen bond to the terminal N atom of the monodentate azide ligand.

Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na).

PubMed

Solbrå, S; Allison, N; Waite, S; Mikhalovsky, S V; Bortun, A I; Bortun, L N; Clearfield, A

2001-02-01

The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.

Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

PubMed Central

Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

2012-01-01

Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

Infrared spectra of N2O-(ortho-D2)N and N2O-(HD)N clusters trapped in bulk solid parahydrogen.

PubMed

Lorenz, Britney D; Anderson, David T

2007-05-14

High-resolution infrared spectra of the clusters N2O-(ortho-D2)N and N2O-(HD)N, N=1-4, isolated in bulk solid parahydrogen at liquid helium temperatures are studied in the 2225 cm-1 region of the nu3 antisymmetric stretch of N2O. The clusters form during vapor deposition of separate gas streams of a precooled hydrogen mixture (ortho-D2para-H2 or HDpara-H2) and N2O onto a BaF2 optical substrate held at approximately 2.5 K in a sample-in-vacuum liquid helium cryostat. The cluster spectra reveal the N2O nu3 vibrational frequency shifts to higher energy as a function of N, and the shifts are larger for ortho-D2 compared to HD. These vibrational shifts result from the reduced translational zero-point energy for N2O solvated by the heavier hydrogen isotopomers. These spectra allow the N=0 peak at 2221.634 cm-1, corresponding to the nu3 vibrational frequency of N2O isolated in pure solid parahydrogen, to be assigned. The intensity of the N=0 absorption feature displays a strong temperature dependence, suggesting that significant structural changes occur in the parahydrogen solvation environment of N2O in the 1.8-4.9 K temperature range studied.

The roles of two O-donor ligands in the Fe2+-binding and H2O2-sensing by the Fe2+-dependent H2O2 sensor PerR.

PubMed

Ji, Chang-Jun; Yang, Yoon-Mo; Kim, Jung-Hoon; Ryu, Su-Hyun; Youn, Hwan; Lee, Jin-Won

2018-05-10

PerR is a metal-dependent peroxide sensing transcription factor which controls the expression of genes involved in peroxide resistance. The function of Bacillus subtilis PerR is mainly dictated by the regulatory metal ion (Fe 2+ or Mn 2+ ) coordinated by three N-donor ligands (His37, His91, and His93) and two O-donor ligands (Asp85 and Asp104). While H 2 O 2 sensing by PerR is mediated by Fe 2+ -dependent oxidation of N-donor ligand (either His37 or His91), one of the O-donor ligands (Asp104), but not Asp85, has been proposed as the key residue that regulates the sensitivity of PerR to H 2 O 2 . Here we systematically investigated the relative roles of two O-donor ligands of PerR in metal-binding affinity and H 2 O 2 sensitivity in vivo and in vitro. Consistent with the previous report, in vitro the D104E-PerR could not sense low levels of H 2 O 2 in the presence of excess Fe 2+ sufficient for the formation of the Fe 2+ -bound D104E-PerR. However, the expression of PerR-regulated reporter fusion was not repressed by D104E-PerR in the presence of Fe 2+ , suggesting that Fe 2+ is not an effective corepressor for this mutant protein in vivo. Furthermore, in vitro metal titration assays indicate that D104E-PerR has a significantly reduced affinity for Fe 2+ , but not for Mn 2+ , when compared to wild type PerR. These data indicate that the type of O-donor ligand (Asp vs. Glu) at position 104 is an important determinant in providing high Fe 2+ -binding affinity required for the sensing of the physiologically relevant Fe 2+ -levels, in addition to its role in rendering PerR highly sensitive to physiological levels of H 2 O 2 . In comparison, the D85E-PerR did not show a perturbed change in Fe 2+ -binding affinity, however, it displayed a slightly decreased sensitivity to H 2 O 2 both in vivo and in vitro, suggesting that the type of O-donor ligand (Asp vs. Glu) at position 85 may be important for the fine-tuning of H 2 O 2 sensitivity. Copyright © 2018 Elsevier

Synthesis, structure, and properties of nickel complexes with nitrilotris(methylenephosphonic acid) [Ni(H{sub 2}O)3N(CH2PO{sub 3}H){sub 3}] and Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@yandex.ru; Zakirova, R. M.

2016-03-15

Nitrilotris(methylenephosphonato)triaquanickel and tetrasodium nitrilotris(methylenephosphonato) aquanickelate undecahydrate were synthesized and characterized. The crystal of [Ni(H{sub 2}O){sub 3}N(CH{sub 2}PO{sub 3}H){sub 3}] is composed of linear coordination polymers and belongs to sp. gr. P2{sub 1}/c, Z = 4, a = 9.17120(10) Å, b = 16.05700(10) Å, c = 9.70890(10) Å, β = 115.830(2)°. The Ni atom is in an octahedral coordination formed by two oxygen atoms of one phosphonate ligand, one oxygen atom of another ligand molecule, and three water molecules in a meridional configuration. The crystal of Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O has an island dimeric chelate structuremore » and belongs to sp. gr. C2/c, Z = 8, a = 18.7152(2) Å, b = 12.05510(10) Å, c = 21.1266(2) Å, β = 104.4960(10)°. The Ni atom has a slightly distorted octahedral coordination involving one nitrogen atom and closes three five-membered N–C–P–O–Ni rings sharing the Ni–N bond.« less

Aspects of Supercritical Turbulence: Direct Numerical Simulation of O2/H2 and C7H16/N2 Temporal Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, J.; Okongo, N. A.; Harstad, K. G.; Hutt, John (Technical Monitor)

2002-01-01

Results from Direct Numerical Simulations of temporal, supercritical mixing layers for two species systems are analyzed to elucidate species-specific turbulence aspects. The two species systems, O2/H2 and C7HG16/N2, have different thermodynamic characteristics; thus, although the simulations are performed at similar reduced pressure (ratio of the pressure to the critical pressure), the former system is dose to mixture ideality and has a relatively high solubility with respect to the latter, which exhibits strong departures from mixture ideality Due to the specified, smaller initial density stratification, the C7H16/N2 layers display higher growth and increased global molecular mixing as well as larger turbulence levels. However, smaller density gradients at the transitional state for the O2/H2 system indicate that on a local basis, the layer exhibits an enhanced mixing, this being attributed to the increased solubility and to mixture ideality. These thermodynamic features are shown to affect the irreversible entropy production (i.e. the dissipation), which is larger for the O2/H2 layer and is primarily concentrated in high density-gradient magnitude regions that are distortions of the initial density stratification boundary. In contrast, the regions of largest dissipation in the C7H16/N2 layer are located in high density-gradient magnitude regions resulting from the mixing of the two fluids.

Ab initio electron correlated studies on the intracluster reaction of NO+ (H2O)(n) → H3O+ (H2O)(n-2) (HONO) (n = 4 and 5).

PubMed

Asada, Toshio; Nagaoka, Masataka; Koseki, Shiro

2011-01-28

Hydrated nitrosonium ion clusters NO(+)(H(2)O)(n) (n = 4 and 5) were investigated by using MP2/aug-cc-pVTZ level of theory to clarify isomeric reaction pathways for formation of HONO and fully hydrated hydride ions. We found some new isomers and transition state structures in each hydration number, whose lowest activation energies of the intracluster reactions were found to be 4.1 and 3.4 kcal mol(-1) for n = 4 and n = 5, respectively. These thermodynamic properties and full quantum mechanical molecular dynamics simulation suggest that product isomers with HONO and fully hydrated hydride ions can be obtained at n = 4 and n = 5 in terms of excess hydration binding energies which can overcome these activation barriers.

The denitrification paradox: The role of O2 in sediment N2O production

NASA Astrophysics Data System (ADS)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

(Carbonato-κ(2)O,O')bis-(5,5'-dimethyl-2,2'-bipyridyl-κ(2)N,N')cobalt(III) bromide trihydrate.

PubMed

Arun Kumar, Kannan; Meera, Parthsarathi; Amutha Selvi, Madhavan; Dayalan, Arunachalam

2012-04-01

In the title complex, [Co(CO(3))(C(12)H(12)N(2))(2)]Br·3H(2)O, the Co(III) cation has a distorted octa-hedral coordination environment. It is chelated by four N atoms of two different 5,5'-dimethyl-2,2'-bipyridyl (dmbpy) ligands in axial and equatorial positions, and by two O atoms of a carbonate anion completing the equatorial positions. Although the water mol-ecules are disordered and their H atoms were not located, there are typical O⋯O distances between 2.8 and 3.0 Å, indicating O-H⋯O hydrogen bonding. The crystal packing is consolidated by C-H⋯O and C-H⋯Br hydrogen bonds, as well as π-π stacking inter-actions between adjacent pyridine rings of the dmbpy ligands, with centroid-centroid distances of 3.694 (3) and 3.7053 (3) Å.

Spectroscopic and electrochemical properties of group 12 acetates of di-2-pyridylketone thiophene-2-carboxylic acid hydrazone (dpktch-H) complexes. The structure of [Cd(η³-N,N,O-dpktch-H)₂].

PubMed

Bakir, Mohammed; Lawrence, Mark A W; McBean, Shameal

2015-07-05

The reaction between [dpktch] and [M(OAc)2] (M=group 12 metal atom) in refluxing CH3CN gave [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O (n=0 or 1). The infrared and (1)H NMR spectra are consistent with the coordination of [η(2)-O,O-OAc] and [η(3)-N,N,O-dpktch-H](-) and the proposed formulations. The electronic absorption spectra of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O measured in non-aqueous solvents revealed a highly intense intra-ligand-charge transfer (ILCT) transition due to π-π∗ of dpk followed by dpk→thiophene charge transfer. The electronic transitions of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O are solvent and concentration dependent. Spectrophotometric titrations of dmso solutions of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O with benzoic acid revealed irreversible inter-conversion between [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O and it conjugate acid [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch)]·nH2O pointing to ligand exchange between the acetate and benzoate anions. When CH2Cl2 solutions of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O were titrated with dmso, changes appeared pointing to solvolysis or ligand exchange reactions. Electrochemical measurements on dmso solutions of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O divulged irreversible redox transformations consistent with electrochemical decomposition of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O. The solid state structure of a single crystal of [Cd(η(3)-N,N,O-dpktch-H)2] obtained from a dmso solution of [Cd(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O confirmed the ligand scrambling of [M(η(2)-O,O-OAc)(η(3)-N,N,O-dpktch-H)]·nH2O. The extended structure of [Cd(η(3)-N,N,O-dpktch-H)2] revealed stacks of [Cd(η(3)-N,N,O-dpktch-H)2] locked via a network of hydrogen bonds. A significant amount of empty space (35.5%) was observed in the solid state structure of [Cd(η(3)-N,N,O-dpktch-H)2]. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparison of the frequencies of NH3, CO2, H2O, N2O, CO, and CH4 as infrared calibration standards

NASA Technical Reports Server (NTRS)

Brown, L. R.; Toth, R. A.

1985-01-01

The absolute accuracies of infrared calibration standards for the line positions have been investigated using a 0.0056-kayser-resolution (unapodized) Fourier-transform spectrum recorded from 550 to 5000 kayser. The spectrum has been obtained using a multicell arrangement containing the various molecular species. Detailed comoparisons reveal that standards for CO2, CH4, and N2O obtained from laser research and NH3 from Fourier-transform spectrometer research are consistent within the accuracies of the present data (+ or 0.0001 kayser). However, certain N2O, H2O, and CO values in the 1100-to 2300 kayser region are systematically high by 0.0001 to 0.0004 kayser. Correction factors for the H2O and CO standards are obtained to bring these into agreement with the laser values. In addition, corrected values for the 2nu-2 and nu-1 bands of N2O at 9 microns are reported.

Synthesis, structure, optical, photoluminescence and magnetic properties of K2[Co(C2O4)2(H2O)2]·4H2O

NASA Astrophysics Data System (ADS)

Narsimhulu, M.; Hussain, K. A.

2018-06-01

The synthesis, crystal structure, optical, photoluminescence and magnetic behaviour of potassium bis(oxalato)cobaltate(II)tertrahydrate{K2[Co(C2O4)2(H2O)2]·4H2O} are described. The compound was grown at room temperature from mixture of aqueous solutions by slow evaporation method. The X-ray crystallographic data showed that the compound belongs to the monoclinic crystal system with P21/n space group and Z = 4. The UV-visible diffuse absorbance spectra exhibited bands at 253, 285 and 541 nm in the visible and ultraviolet regions. The optical band gap of the compound was estimated as 3.4 eV. At room temperature, an intense photoluminescence was observed from this material around 392 nm when it excited at 254 nm. The variable temperature dc magnetic susceptibility measurements exposed paramagnetic behaviour at high temperatures and antiferromagnetic ordering at low temperatures.

Electronic and vibrational spectroscopic studies of jet-cooled 5-cyanoindole and its water clusters, 5CI-(H2O)n, (n = 0-2)

NASA Astrophysics Data System (ADS)

Min, Ahreum; Moon, Cheol Joo; Ahn, Ahreum; Lee, Ji Hoon; Kim, Seong Keun; Choi, Myong Yong

2016-08-01

Mass-selected resonant two-photon ionization (R2PI) and UV-UV hole-burning, and infrared-dip spectra of 5-cyanoindole (5CI) and its water clusters, 5CI-(H2O)n (n = 1 and 2) were measured. Although, the structures of 5CI-(H2O)1-2 are similar to those of 3CI-(H2O)1-2, the photofragmentation behaviors of the two systems are quite different due to the La-Lb state energy lowering and higher binding energies of 5CI-(H2O)1-2 compared to those of 3CI-(H2O)1-2. Especially for the case of 5CI-(H2O)2 cluster, shortening excited-state lifetime of 5CI-(H2O)2 causes the broad background in the R2PI spectrum of 5CI-(H2O)2.

Selective photocatalytic reduction of CO2 by H2O/H2 to CH4 and CH3OH over Cu-promoted In2O3/TiO2 nanocatalyst

NASA Astrophysics Data System (ADS)

Tahir, Muhammad; Tahir, Beenish; Saidina Amin, Nor Aishah; Alias, Hajar

2016-12-01

Photocatalytic CO2 reduction by H2O and/or H2 reductant to selective fuels over Cu-promoted In2O3/TiO2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N2 adsorption-desorption, UV-vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO2, oxidized as Cu2+ and In3+, promoted efficient separation of photo-generated electron/hole pairs (e-/h+). The results indicate that the reduction rate of CO2 by H2O to CH4 approached to 181 μmol g-1 h-1 using 0.5% Cu-3% In2O3/TiO2 catalyst, a 1.53 fold higher than the production rate over the 3% In2O3/TiO2 and 5 times the amount produced over the pure TiO2. In addition, Cu was found to promote efficient production of CH3OH and yield rate reached to 68 μmol g-1 h-1 over 1% Cu-3% In2O3/TiO2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H2 reductant was less favorable for CH4 production, yet a significant amount of CH4 and CH3OH were obtained using a mixture of H2O/H2 reductant. Therefore, Cu-loaded In2O3/TiO2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In2O3/TiO2 catalyst.

A Tale of Two Gases: Isotope Effects Associated with the Enzymatic Production of H2 and N2O

NASA Astrophysics Data System (ADS)

Yang, H.; Gandhi, H.; Kreuzer, H. W.; Moran, J.; Hill, E. A.; McQuarters, A.; Lehnert, N.; Ostrom, N. E.; Hegg, E. L.

2014-12-01

Stable isotopes can provide considerable insight into enzymatic mechanisms and fluxes in various biological processes. In our studies, we used stable isotopes to characterize both enzyme-catalyzed H2 and N2O production. H2 is a potential alternative clean energy source and also a key metabolite in many microbial communities. Biological H2 production is generally catalyzed by hydrogenases, enzymes that combine protons and electrons to produce H2 under anaerobic conditions. In our study, H isotopes and fractionation factors (α) were used to characterize two types of hydrogenases: [FeFe]- and [NiFe]-hydrogenases. Due to differences in the active site, the α associated with H2 production for [FeFe]- and [NiFe]-hydrogenases separated into two distinct clusters (αFeFe > αNiFe). The calculated kinetic isotope effects indicate that hydrogenase-catalyzed H2 production has a preference for light isotopes, consistent with the relative bond strengths of O-H and H-H bonds. Interestingly, the isotope effects associated with H2 consumption and H2-H2O exchange reactions were also characterized, but in this case no specific difference was observed between the different enzymes. N2O is a potent greenhouse gas with a global warming potential 300 times that of CO2, and the concentration of N2O is currently increasing at a rate of ~0.25% per year. Thus far, bacterial and fungal denitrification processes have been identified as two of the major sources of biologically generated N2O. In this study, we measured the δ15N, δ18O, δ15Nα (central N atom in N2O), and δ15Nβ (terminal N atom in N2O) of N2O generated by purified fungal P450 nitric oxide reductase (P450nor) from Histoplasma capsulatum. We observed normal isotope effects for δ18O and δ15Nα, and inverse isotope effects for bulk δ15N (the average of Nα and Nβ) and δ15Nβ. The observed isotope effects have been used in conjunction with DFT calculations to provide important insight into the mechanism of P450nor. Similar

Organic Contaminant Abatement in Reclaimed Water by UV/H2O2 and a Combined Process Consisting of O3/H2O2 Followed by UV/H2O2: Prediction of Abatement Efficiency, Energy Consumption, and Byproduct Formation.

PubMed

Lee, Yunho; Gerrity, Daniel; Lee, Minju; Gamage, Sujanie; Pisarenko, Aleksey; Trenholm, Rebecca A; Canonica, Silvio; Snyder, Shane A; von Gunten, Urs

2016-04-05

UV/H2O2 processes can be applied to improve the quality of effluents from municipal wastewater treatment plants by attenuating trace organic contaminants (micropollutants). This study presents a kinetic model based on UV photolysis parameters, including UV absorption rate and quantum yield, and hydroxyl radical (·OH) oxidation parameters, including second-order rate constants for ·OH reactions and steady-state ·OH concentrations, that can be used to predict micropollutant abatement in wastewater. The UV/H2O2 kinetic model successfully predicted the abatement efficiencies of 16 target micropollutants in bench-scale UV and UV/H2O2 experiments in 10 secondary wastewater effluents. The model was then used to calculate the electric energies required to achieve specific levels of micropollutant abatement in several advanced wastewater treatment scenarios using various combinations of ozone, UV, and H2O2. UV/H2O2 is more energy-intensive than ozonation for abatement of most micropollutants. Nevertheless, UV/H2O2 is not limited by the formation of N-nitrosodimethylamine (NDMA) and bromate whereas ozonation may produce significant concentrations of these oxidation byproducts, as observed in some of the tested wastewater effluents. The combined process of O3/H2O2 followed by UV/H2O2, which may be warranted in some potable reuse applications, can achieve superior micropollutant abatement with reduced energy consumption compared to UV/H2O2 and reduced oxidation byproduct formation (i.e., NDMA and/or bromate) compared to conventional ozonation.

Triaqua-1κO,2κ2 O-bis­(2,2′-bipyridine)-1κ2 N,N′;2κ2 N,N′-chlorido-1κCl-μ-terephthalato-1:2κ2 O 1:O 4-dicopper(II) nitrate monohydrate

PubMed Central

Liu, Yang; Feng, Yong-Lan; Kuang, Dai-Zhi

2012-01-01

In the binuclear title compound, [Cu2(C8H4O4)Cl(C10H8N2)2(H2O)3]NO3·H2O, the two crystallographically independent CuII ions have similar coordination environments. One of the CuII ions has a square-pyramidal arrangement, which is defined by a water mol­ecule occupying the apical position, with the equatorial ligators consisting of two N atoms from a 2,2′-bipyridine mol­ecule, one carboxyl­ate O atom from a terephthalate ligand and one O atom from a water mol­ecule. The other CuII ion has a similar coordination environment, except that the apical position is occupied by a chloride ligand instead of a water mol­ecule. An O—H⋯O and O—H⋯Cl hydrogen-bonded three-dimensional network is formed between the components. PMID:22719307

Axial zero-field splitting in mononuclear Co(ii) 2-N substituted N-confused porphyrin: Co(2-NC3H5-21-Y-CH2C6H4CH3-NCTPP)Cl (Y = o, m, p) and Co(2-NC3H5-21-CH2C6H5-NCTPP)Cl.

PubMed

Lai, Ya-Yuan; Chang, Yu-Chang; Chen, Jyh-Horung; Wang, Shin-Shin; Tung, Jo-Yu

2016-03-21

The inner C-benzyl- and C-o-xylyl (or m-xylyl, p-xylyl)-substituted cobalt(ii) complexes of a 2-N-substituted N-confused porphyrin were synthesized from the reaction of 2-NC3H5NCTPPH (1) and CoCl2·6H2O in toluene (or o-xylene, m-xylene, p-xylene). The crystal structures of diamagnetic chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-hydrogen-21-carbaporphyrinato-N,N',N'')zinc(ii) [Zn(2-NC3H5-21-H-NCTPP)Cl; 3 ] and paramagnetic chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-benzyl-21-carbaporphyrinato-N,N',N'')cobalt(ii) [Co(2-NC3H5-21-CH2C6H5NCTPP)Cl; 7], and chloro(2-aza-2-allyl-5,10,15,20-tetraphenyl-21-Y-xylyl-21-carbaporphyrinato-N,N',N'')cobalt(ii) [Co(2-NC3H5-21-Y-CH2C6H4CH3NCTPP)Cl] [Y = o (8), m (9), p (10)] were determined. The coordination sphere around the Zn(2+) (or Co(2+)) ion in 3 (or 7-10) is a distorted tetrahedron (DT). The free energy of activation at the coalescence temperature Tc for the exchange of phenyl ortho protons o-H (26) with o-H (22) in 3 in a CDCl3 solvent is found to be ΔG = 61.4 kJ mol(-1) through (1)H NMR temperature-dependent measurements. The axial zero-field splitting parameter |D| was found to vary from 35.6 cm(-1) in 7 (or 30.7 cm(-1) in 8) to 42.0 cm(-1) in 9 and 46.9 cm(-1) in 10 through paramagnetic susceptibility measurements. The magnitude of |D| can be related to the coordination sphere at the cobalt sites.

Structural Evolution of Reversible Mg Insertion into a Bilayer Structure of V 2 O 5 · n H 2 O Xerogel Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sa, Niya; Kinnibrugh, Tiffany L.; Wang, Hao

Functional multivalent intercalation cathodes represent one of the largest hurdles in the development of Mg batteries. While there are many reports of Mg cathodes, many times the evidence of intercalation chemistry is only circumstantial. In this work, direct evidence of Mg intercalation into a bilayer structure of V2O5·nH2O xerogel is confirmed, and the nature of the Mg intercalated species is reported. The interlayer spacing of V2O5·nH2O contracts upon Mg intercalation and expands for Mg deintercalation due to the strong electrostatic interaction between the divalent cation and the cathode. A combination of NMR, pair distribution function (PDF) analysis, and X-ray absorptionmore » near edge spectroscopy (XANES) confirmed reversible Mg insertion into the V2O5·nH2O material, and structural evolution of Mg intercalation leads to the formation of multiple new phases. Structures of V2O5·nH2O with Mg intercalation were further supported by the first principle simulations. A solvent cointercalated Mg in V2O5·nH2O is observed for the first time, and the 25Mg magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was used to elucidate the structure obtained upon electrochemical cycling. Specifically, existence of a well-defined Mg–O environment is revealed for the Mg intercalated structures. Information reported here reveals the fundamental Mg ion intercalation mechanism in a bilayer structure of V2O5·nH2O material and provides insightful design metrics for future Mg cathodes.« less

Microhydration effects on the electronic spectra of protonated polycyclic aromatic hydrocarbons: [naphthalene-(H2O)n = 1,2]H+

NASA Astrophysics Data System (ADS)

Alata, Ivan; Broquier, Michel; Dedonder-Lardeux, Claude; Jouvet, Christophe; Kim, Minho; Sohn, Woon Yong; Kim, Sang-su; Kang, Hyuk; Schütz, Markus; Patzer, Alexander; Dopfer, Otto

2011-02-01

Vibrational and electronic spectra of protonated naphthalene (NaphH+) microsolvated by one and two water molecules were obtained by photofragmentation spectroscopy. The IR spectrum of the monohydrated species is consistent with a structure with the proton located on the aromatic molecule, NaphH+-H2O. Similar to isolated NaphH+, the first electronic transition of NaphH+-H2O (S1) occurs in the visible range near 500 nm. The doubly hydrated species lacks any absorption in the visible range (420-600 nm) but absorbs in the UV range, similar to neutral Naph. This observation is consistent with a structure, in which the proton is located on the water moiety, Naph-(H2O)2H+. Ab initio calculations for [Naph-(H2O)n]H+ confirm that the excess proton transfers from Naph to the solvent cluster upon attachment of the second water molecule.

On the role of the termolecular reactions 2O2 + H2 → 2HO2 and 2O2 + H2 → H + HO2 + O2 in formation of the first radicals in hydrogen combustion: ab initio predictions of energy barriers.

PubMed

Monge-Palacios, M; Rafatijo, Homayoon

2017-01-18

We have investigated the role of termolecular reactions in the early chemistry of hydrogen combustion. We performed molecular chemical dynamics simulations using ReaxFF in LAMMPS to identify potential initial reactions for a 1 : 4 mixture of H 2  : O 2 in the NVT ensemble at density 276.3 kg m -3 and ∼3000 K (∼4000 atm) and ∼4000 K (∼5000 atm), and then characterized the saddle points for those reactions using ab initio methods: CCSD(T) = FC/cc-pVTZ//MP2/6-31G, CCSD(T) = FULL/aug-cc-pVTZ//CCSD = FC/cc-pVTZ and CASSCF MP2/6-31G//MP2/6-31G. The main initial reaction is H 2 + O 2 → H + HO 2 , frequently occurring in the presence of a second O 2 as a third body; that is, 2O 2 + H 2 → H + HO 2 + O 2 . The second most frequent reaction is 2O 2 + H 2 → 2HO 2 . We found three saddle points on the triplet PES of these termolecular reactions: one for 2O 2 + H 2 → H + HO 2 + O 2 and two for 2O 2 + H 2 → 2HO 2 . In the latter case, one has a symmetric structure consistent with simultaneous formation of two HO 2 and the other corresponds to a bimolecular reaction between O 2 and H 2 that is "interrupted" by a second O 2 before going to completion. The classical barrier height of the symmetric saddle point for 2O 2 + H 2 → 2HO 2 is 49.8 kcal mol -1 . The barrier to H 2 + O 2 → H + HO 2 is 58.9 kcal mol -1 . The termolecular reaction will be competitive with H 2 + O 2 → H + HO 2 only at sufficiently high pressures.

Exploration of H2O-CO2 Solubility in Alkali Basalt at low-H2O

NASA Astrophysics Data System (ADS)

Roggensack, K.; Allison, C. M.; Clarke, A. B.

2017-12-01

A number of recent experimental studies have found conflicting evidence for and against the influence of H2O on CO2 solubility in basalt and alkali-rich mafic magma (e.g. Behrens et al., 2009; Shishkina et al., 2010;2014; Iacono-Marziano et al., 2012). Some of the uncertainty is due to the error with spectroscopic determination (FTIR) of carbon and the challenge of controlling H2O abundance in experiments. It's been widely observed that even experimental capsules without added H2O may produce hydrous glasses containing several wt.% H2O. We conducted fluid-saturated, mixed-fluid (H2O-CO2) experiments to determine the solubility in alkali basalt with particular emphasis on conditions at low-H2O. To limit possible H2O contamination, materials were dried prior to loading and experimental capsules were sealed under vacuum. Experiments were run using a piston-cylinder, in Pt (pre-soaked in Fe) or AuPd capsules and operating at pressures from 400 to 600 MPa. Post-run the capsules were punctured under vacuum and fluids were condensed, separated, and measured by mercury manometry. A comparison between two experiments run at the same temperature and pressure conditions but with different fluid compositions illustrates the correlation between carbonate and H2O solubility. Uncertainties associated with using concentrations calculated from FTIR data can be reduced by directly comparing analyses on wafers of similar thickness. We observe that the experiment with greater H2O absorbance also has a higher carbonate absorbance than the experiment with lower H2O absorbance. Since the experiments were run at the same pressure, the experiment with more water-rich fluid, and higher dissolved H2O, has lower CO2 fugacity, but surprisingly has higher dissolved CO2 content. Overall, the results show two distinct trends. Experiments conducted at low-H2O (0.5 to 0.8 wt.%) show lower dissolved CO2 than those conducted at moderate-H2O (2 to 3 wt.%) at similar CO2 fugacity. These data show that

LED and low level laser therapy association in tooth bleaching using a novel low concentration H2O2/N-doped TiO2 bleaching agent

NASA Astrophysics Data System (ADS)

Bezerra Dias, Hércules; Teixeira Carrera, Emanuelle; Freitas Bortolatto, Janaína; Ferrarezi de Andrade, Marcelo; Nara de Souza Rastelli, Alessandra

2016-01-01

Since low concentration bleaching agents containing N-doped TiO2 nanoparticles have been introduced as an alternative to conventional agents, it is important to verify their efficacy and the hypersensitivity effect in clinical practice. Six volunteer patients were evaluated for color change and hypersensitivity after bleaching using 35% H2O2 (one session of two 12 min applications) and 6% H2O2/N-doped TiO2 (one session of three 12 min applications) and after low level laser therapy application (LLLT) (780 nm, 40 mW, 10 J.cm-2, 10 s). Based on this case study, the nanobleaching agent provided better or similar aesthetic results than the conventional agent under high concentration, and its association with LLLT satisfactorily decreased the hypersensitivity. The 6% H2O2/N-doped TiO2 agent could be used instead of conventional in-office bleaching agents under high concentrations to fulfill the rising patient demand for aesthetics.

Experimental and theoretical investigation of homogeneous gaseous reaction of CO2(g) + nH2O(g) + nNH3(g) → products (n = 1, 2).

PubMed

Li, Zhuangjie; Zhang, Baoquan

2012-09-13

Decreasing CO2 emissions into the atmosphere is key for reducing global warming. To facilitate the CO2 emission reduction efforts, our laboratory conducted experimental and theoretical investigations of the homogeneous gaseous reaction of CO2(g) + nH2O(g) + nNH3(g) → (NH4)HCO3(s)/(NH4)2CO3(s) (n = 1 and 2) using Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy and ab initio molecular orbital theory. Our FTIR-ATR experimental results indicate that (NH4)2CO3(s) and (NH4)HCO3(s) are formed as aerosol particulate matter when carbon dioxide reacts with ammonia and water in the gaseous phase at room temperature. Ab initio study of this chemical system suggested that the reaction may proceed through formation of NH3·H2O(g), NH3·CO2(g), and CO2·H2O(g) complexes. Subsequent complexes, NH3·H2O·CO2 and (NH3)2·H2O·CO2, can be formed by adding gaseous reactants to the NH3·H2O(g), NH3·CO2(g), and CO2·H2O(g) complexes, respectively. The NH3·H2O·CO2 and (NH3)2·H2O·CO2 complexes can then be rearranged to produce (NH4)HCO3 and (NH4)2CO3 as final products via a transition state, and the NH3 molecule acts as a medium accepting and donating hydrogen atoms in the rearrangement process. Our computational results also reveal that the presence of an additional water molecule can reduce the activation energy of the rearrangement process. The high activation energy predicted in the present work suggests that the reaction is kinetically not favored, and our experimental observation of (NH4)HCO3(s) and (NH4)2CO3(s) may be attributed to the high concentrations of reactants increasing the reaction rate of the title reactions in the reactor.

Nanostructured N-doped TiO2 marigold flowers for an efficient solar hydrogen production from H2S

NASA Astrophysics Data System (ADS)

Chaudhari, Nilima S.; Warule, Sambhaji S.; Dhanmane, Sushil A.; Kulkarni, Milind V.; Valant, Matjaz; Kale, Bharat B.

2013-09-01

Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO2 systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO2 from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and

Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl− and H2O around Zn2+. According to the solid–liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn2+ both in a tetra­hedral coordination with Cl− and in an octa­hedral environment defined by five water mol­ecules and one Cl− shared with the [ZnCl4]2− unit. Thus, these two different types of Zn2+ cations form isolated units with composition [Zn2Cl4(H2O)5] (penta­aqua-μ-chlorido-tri­chlorido­di­zinc). The trihydrate {hexa­aqua­zinc tetra­chlorido­zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn2+ cations, one of which is tetra­hedrally coordinated by four Cl− anions. The two other Zn2+ cations are each located on an inversion centre and are octa­hedrally surrounded by water mol­ecules. The [ZnCl4] tetra­hedra and [Zn(H2O)6] octa­hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa­aqua­zinc tetra­chlorido­zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa­hedral [Zn(H2O)6] and tetra­hedral [ZnCl4] units, as well as additional lattice water mol­ecules. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ZnCl4 tetra­hedra and water mol­ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures. PMID:25552980

Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

PubMed

Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

2017-02-08

We demonstrate that the complex adsorption behavior of H 2 O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H 2 O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H 2 O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H 2 O adsorbates forming surface recombination centers and multiple H 2 O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H 3 O + and OH - ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

Magnetic properties of TM3[Cr(CN)6]2.n H2O

NASA Astrophysics Data System (ADS)

Zentková, M.; Mihalik, M.; Ková, J.; Zentko, A.; Mitróová, Z.; Lukáová, M.; Kaveanský, V.; Kiss, L. F.

2006-01-01

Magnetization measurements performed on Prussian blue analogs TM2+3[CrIII(CN)6]2.n H2O (TM = Cr, Mn, Fe, Co, Ni, Cu) confirmed the dual character of the exchange interaction (antiferromagnetic AFM and ferromagnetic FM) in this system. AFM interaction dominates for the Cr2+ sample and with rising atomic number Z the FM interaction becomes more important reaching pure FM character for the Cu2+ sample.

Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures.

PubMed

Liu, Shurong; Berns, Anne E; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

2017-02-01

Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH 2 OH) to nitrous oxide (N 2 O) is a possible mechanism of N 2 O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO 2 ) and organic matter (OM) content of soil as well as soil pH are important control variables of N 2 O formation in the soil. But until now, their combined effect on abiotic N 2 O formation from NH 2 OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO 2 and OM, respectively, and quantified the interactive effects of the three variables on the NH 2 OH-to-N 2 O conversion ratio (R NH2OH-to-N2O ). Furthermore, the effect of OM quality on R NH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO 2 and OM on R NH2OH-to-N2O . In general, increasing MnO 2 and decreasing pH increased R NH2OH-to-N2O , while increasing OM content was associated with a decrease in R NH2OH-to-N2O . Organic matter quality also affected R NH2OH-to-N2O . However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

NASA Astrophysics Data System (ADS)

Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

2017-02-01

Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

A pure inorganic 1D chain based on {Mo8O28} clusters and Mn(II) ions: [Mn(H2O)2Mo8O28 ] n 6 n -

NASA Astrophysics Data System (ADS)

Zhang, Xiaofen; Yan, Yonghong; Wu, Lizhou; Yu, Chengxin; Dong, Xinbo; Hu, Huaiming; Xue, Ganglin

2016-01-01

A new pure inorganic polymer, (NH4)6n[Mn(H2O)2Mo8O28)]n(H2O)2n(1), has been synthesized and characterized by elemental analyses, IR spectrum, UV-vis absorption spectra, TG-DSC and electrochemical studies. In 1, [Mo8O28]8- anions act as tetradentate ligands and are alternately linked by Mn(H2O)2 2 + ions into a one-dimensional chain structure. It is interesting that 1 represents the first example of pure inorganic-inorganic hybrid based on octamolybdate and transition metal ions. Moreover, it was indicated that 1 had definite catalytic activities on the probe reaction of benzyl alcohol oxidation to benzaldehyde with H2O2.

Synthesis, structure and physicochemical characterization of the hybrid material [C6H16N2O]2 SnCl6·2Cl·2H2O

NASA Astrophysics Data System (ADS)

Belhaj Salah, S.; Pereira da Silva, P. S.; Lefebvre, F.; Ben Nasr, C.; Ammar, S.; Mrad, M. L.

2017-04-01

The current study reports the chemical preparation, crystal structure, Hirshfeld surface analysis and spectroscopic characterization of the novel compound [C6H16N2O]2SnCl6·2Cl·2H2O. This compound crystallizes in the triclinic system (space group P - 1, Z = 1) with the following unit cell dimensions: a = 7.9764(9), b = 8.2703(9), c = 12.1103(14)Å, α = 84.469(6), β = 75.679(6), and γ = 64.066(5)°. The structure was solved using 3093 independent reflections down to R = 0.020. The atomic arrangement shows alternation of organic and inorganic entities. The cohesion between these entities is ensured by Nsbnd H…Cl and Osbnd H…Cl hydrogen bonds that build a three-dimensional network. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots were investigated for intermolecular interactions. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the IR and NMR bands. X-ray powder, XPS and UV spectrum have been carried out. The DSC profile shows that the title material exhibits dehydration at 339 K.

Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters.

PubMed

Pathak, A K; Mukherjee, T; Maity, D K

2007-07-28

We report vertical detachment energy (VDE) and IR spectra of Br2.-.(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2.-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150 K. A linear relationship is obtained for VDE versus (n+3)(-1/3) and bulk VDE of Br2.- aqueous solution is calculated as 10.01 eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by approximately 0.5 eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by approximately 6.4 eV. Calculated IR spectra show that the formation of Br2.--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2.-.(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters

NASA Astrophysics Data System (ADS)

Pathak, A. K.; Mukherjee, T.; Maity, D. K.

2007-07-01

We report vertical detachment energy (VDE) and IR spectra of Br2•-•(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2•-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150K. A linear relationship is obtained for VDE versus (n+3)-1/3 and bulk VDE of Br2•- aqueous solution is calculated as 10.01eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by ˜0.5eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by ˜6.4eV. Calculated IR spectra show that the formation of Br2•--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2•-•(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

Vibrational spectroscopy of (SO4(2-)).(H2O)n clusters, n=1-5: harmonic and anharmonic calculations and experiment.

PubMed

Miller, Yifat; Chaban, Galina M; Zhou, Jia; Asmis, Knut R; Neumark, Daniel M; Gerber, R Benny

2007-09-07

The vibrational spectroscopy of (SO4(2-)).(H2O)n is studied by theoretical calculations for n=1-5, and the results are compared with experiments for n=3-5. The calculations use both ab initio MP2 and DFT/B3LYP potential energy surfaces. Both harmonic and anharmonic calculations are reported, the latter with the CC-VSCF method. The main findings are the following: (1) With one exception (H2O bending mode), the anharmonicity of the observed transitions, all in the experimental window of 540-1850 cm(-1), is negligible. The computed anharmonic coupling suggests that intramolecular vibrational redistribution does not play any role for the observed linewidths. (2) Comparison with experiment at the harmonic level of computed fundamental frequencies indicates that MP2 is significantly more accurate than DFT/B3LYP for these systems. (3) Strong anharmonic effects are, however, calculated for numerous transitions of these systems, which are outside the present observation window. These include fundamentals as well as combination modes. (4) Combination modes for the n=1 and n=2 clusters are computed. Several relatively strong combination transitions are predicted. These show strong anharmonic effects. (5) An interesting effect of the zero point energy (ZPE) on structure is found for (SO4(2-)).(H2O)(5): The global minimum of the potential energy corresponds to a C(s) structure, but with incorporation of ZPE the lowest energy structure is C2v, in accordance with experiment. (6) No stable structures were found for (OH-).(HSO4-).(H2O)n, for n

Bis(2,2'-bipyridyl-κN,N')(carbonato-κO,O')cobalt(III) bromide trihydrate.

PubMed

Ma, Peng-Tao; Wang, Yu-Xia; Zhang, Guo-Qian; Li, Ming-Xue

2007-12-06

The title complex, [Co(CO(3))(C(10)H(8)N(2))(2)]Br·3H(2)O, is isostructural with the chloride analogue. The six-coordinated octahedral [Co(2,2'-bipy)(2)CO(3)](+) cation (2,2'-bipy is 2,2'-bipyrid-yl), bromide ion and water mol-ecules are linked together via O-H⋯Br and O-H⋯O hydrogen bonds, generating a one-dimensional chain.

Potassium (2,2'-bipyridine-κN,N')bis-(carbonato-κO,O')cobaltate(III) dihydrate.

PubMed

Wang, Jian-Fei; Lin, Jian-Li

2010-09-30

In the title compound, K[Co(CO(3))(2)(C(10)H(8)N(2))]·2H(2)O, the Co(III) atom is coordinated by two bipyridine N atoms and four O atoms from two bidentate chelating carbonate anions, and thus adopts a distorted octa-hedral N(2)O(4) environment. The [Co(bipy)(CO(3))(2)](-) (bipy is 2,2'-bipyridine) -units are stacked along [100] via π-π stacking inter-actions, with inter-planar distances between the bipyridine rings of 3.36 (4) and 3.44 (6) Å, forming chains. Classical O-H⋯O hydrogen-bonding inter-actions link the chains, forming channels along (100) in which the K(+) ions reside and leading to a three-dimensional supra-molecular architecture.

New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

NASA Astrophysics Data System (ADS)

Weng, Sheng-Feng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-04-01

Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La(1a), Ce(1b)) and [Ce2(C2O4)(C6H6O7)2] . 4H2O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1¯ (No. 2); compound 2 crystallized in monoclinic space group P21/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of CuII ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d1 excited state and two levels of the 4f1 ground state (2F5/2 and 2F7/2). Compounds 1b and 2 containing CeIII ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers.

Characterization of Water Coordination to Ferrous Nitrosyl Complexes with fac-N2O, cis-N2O2, and N2O3 Donor Ligands.

PubMed

McCracken, John; Cappillino, Patrick J; McNally, Joshua S; Krzyaniak, Matthew D; Howart, Michael; Tarves, Paul C; Caradonna, John P

2015-07-06

Electron paramagnetic resonance (EPR) experiments were done on a series of S = (3)/2 ferrous nitrosyl model complexes prepared with chelating ligands that mimic the 2-His-1-carboxylate facial triad iron binding motif of the mononuclear nonheme iron oxidases. These complexes formed a comparative family, {FeNO}(7)(N2Ox)(H2O)3-x with x = 1-3, where the labile coordination sites for the binding of NO and solvent water were fac for x = 1 and cis for x = 2. The continuous-wave EPR spectra of these three complexes were typical of high-spin S = (3)/2 transition-metal ions with resonances near g = 4 and 2. Orientation-selective hyperfine sublevel correlation (HYSCORE) spectra revealed cross peaks arising from the protons of coordinated water in a clean spectral window from g = 3.0 to 2.3. These cross peaks were absent for the {FeNO}(7)(N2O3) complex. HYSCORE spectra were analyzed using a straightforward model for defining the spin Hamiltonian parameters of bound water and showed that, for the {FeNO}(7)(N2O2)(H2O) complex, a single water conformer with an isotropic hyperfine coupling, Aiso = 0.0 ± 0.3 MHz, and a dipolar coupling of T = 4.8 ± 0.2 MHz could account for the data. For the {FeNO}(7)(N2O)(H2O)2 complex, the HYSCORE cross peaks assigned to coordinated water showed more frequency dispersion and were analyzed with discrete orientations and hyperfine couplings for the two water molecules that accounted for the observed orientation-selective contour shapes. The use of three-pulse electron spin echo envelope modulation (ESEEM) data to quantify the number of water ligands coordinated to the {FeNO}(7) centers was explored. For this aspect of the study, HYSCORE spectra were important for defining a spectral window where empirical integration of ESEEM spectra would be the most accurate.

Synthesis and X-ray Crystallography of [Mg(H2O)6][AnO2(C2H5COO)3]2 (An = U, Np, or Pu).

PubMed

Serezhkin, Viktor N; Grigoriev, Mikhail S; Abdulmyanov, Aleksey R; Fedoseev, Aleksandr M; Savchenkov, Anton V; Serezhkina, Larisa B

2016-08-01

Synthesis and X-ray crystallography of single crystals of [Mg(H2O)6][AnO2(C2H5COO)3]2, where An = U (I), Np (II), or Pu (III), are reported. Compounds I-III are isostructural and crystallize in the trigonal crystal system. The structures of I-III are built of hydrated magnesium cations [Mg(H2O)6](2+) and mononuclear [AnO2(C2H5COO)3](-) complexes, which belong to the AB(01)3 crystallochemical group of uranyl complexes (A = AnO2(2+), B(01) = C2H5COO(-)). Peculiarities of intermolecular interactions in the structures of [Mg(H2O)6][UO2(L)3]2 complexes depending on the carboxylate ion L (acetate, propionate, or n-butyrate) are investigated using the method of molecular Voronoi-Dirichlet polyhedra. Actinide contraction in the series of U(VI)-Np(VI)-Pu(VI) in compounds I-III is reflected in a decrease in the mean An═O bond lengths and in the volume and sphericity degree of Voronoi-Dirichlet polyhedra of An atoms.

X-ray diffraction analysis of 4- and 4'-substituted C n H2 n + 1O-C6H3(OH)-CH=N-C6H4-C m H2 m + 1 ( n/ m = 2/1 and 3/4) salicylideneanilines

NASA Astrophysics Data System (ADS)

Kuz'mina, L. G.; Navasardyan, M. A.; Mikhailov, A. A.

2017-11-01

X-ray diffraction study of two crystalline modifications of C2H5O-C6H3(OH)-CH=N-C6H4-CH3 ( 1a, sp. gr. P21/ n, and 1b, sp. gr. C2/c) and C3H7O-C6H3(OH)-CH=N-C6H4-C4H9 ( 2, sp. gr. P212121) has been performed. The 1a crystal structure contains two independent molecules. The molecules are conformationally nonrigid with respect to the mutual rotation of benzene rings; the dihedral angles between their planes are 29.19° and 26.00° in the independent molecules of 1a, 18.72° in the molecule of 1b, and 50.35° in the molecule of 2. The crystal packing of the compounds is discussed.

H2O2/TiO2 photocatalytic oxidation of metol. Identification of intermediates and reaction pathways.

PubMed

Aceituno, Mónica; Stalikas, Constantine D; Lunar, Loreto; Rubio, Soledad; Pérez-Bendito, Dolores

2002-08-01

The applicability of H2O2 to increase the efficiency of TiO2 photocatalytic degradations was investigated. The photographic developer metol [N-methyl-p-aminophenol] that does not adsorb on the surface of TiO2 particulates was used as a model for this purpose. It was proved that metol was mineralised under oxidation with H2O2/TiO2/UV through different thermal and photochemical reactions. Identification of intermediates by both HPLC-electron impact-MS and HPLC-electrospray ionisation-MS helped to elucidate the role of H2O2 and TiO2 in the degradation process and to establish degradation pathways. Intermediates yielded were partially oxygenated aromatic species and dimers, which were amenable to oxidation. The optimal degradation conditions found for mineralisation were 0.4 M H2O2, 5 mg/ml TiO2, pH 9 and irradiation centred at 360 nm (4.9 mW/cm2). The use of oxidants opens an interesting medium to the treatment of effluents containing a diversity of organics since they increase substantially the efficiency of TiO2 photocatalytic degradations.

3-Methyl-7-(2-thienyl)pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione: pi-stacked bilayers built from N-H...O, C-H...O and C-H...pi hydrogen bonds.

PubMed

Trilleras, Jorge; Quiroga, Jairo; Cobo, Justo; Glidewell, Christopher

2009-06-01

In the title compound, C(12)H(9)N(3)O(2)S, the thienyl substituent is disordered over two sets of sites with occupancies of 0.749 (3) and 0.251 (3). A combination of N-H...O, C-H...O and C-H...pi hydrogen bonds links the molecules into bilayers and these bilayers are themselves linked into a continuous structure by pi-pi stacking interactions.

[Zn(phen)(O,N,O)(H2O)] and [Zn(phen)(O,N)(H2O)] with O,N,O is 2,6-dipicolinate and N,O is L-threoninate: synthesis, characterization, and biomedical properties.

PubMed

Chin, Lee-Fang; Kong, Siew-Ming; Seng, Hoi-Ling; Tiong, Yee-Lian; Neo, Kian-Eang; Maah, Mohd Jamil; Khoo, Alan Soo-Beng; Ahmad, Munirah; Hor, Tzi-Sum Andy; Lee, Hong-Boon; San, Swee-Lan; Chye, Soi-Moi; Ng, Chew-Hee

2012-10-01

Two ternary Zn(II) complexes, with 1,10-phenanthroline (phen) as the main ligand and a carboxylate-containing ligand [dipicolinate (dipico) or L-threoninate (L-Thr)] as the subsidiary ligand, were prepared and characterized by elemental analysis, Fourier transform IR, UV, and fluorescence spectroscopy, X-ray diffraction, molar conductivity, and electrospray ionization mass spectrometry. X-ray structure analysis shows that both [Zn(phen)(dipico)(H(2)O)]·H(2)O (1) and [Zn(phen)(L-Thr)(H(2)O)Cl]·2H(2)O (2) have octahedral geometry about the Zn(II) atom. Both complexes can inhibit topoisomerase I, and have better anticancer activity than cisplatin against nasopharyngeal cancer cell lines, HK1 and HONE-1, with concentrations causing 50 % inhibition of cell proliferation (IC(50)) in the low micromolar range. Complex 2 has the highest therapeutic index for HK1. Both Zn(II) complexes can induce cell death by apoptosis. Changing the subsidiary ligand in the Zn(II) complexes affects the UV-fluorescence spectral properties of the coordinated phen ligand, the binding affinity for some DNA sequences, nucleobase sequence-selective binding, the phase at which cell cycle progression was arrested for treated cancer cells, and their therapeutic index.

Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)2(L)H]+ congeners.

PubMed

Häller, L Jonas L; Mas-Marzá, Elena; Cybulski, Mateusz K; Sanguramath, Rajashekharayya A; Macgregor, Stuart A; Mahon, Mary F; Raynaud, Christophe; Russell, Christopher A; Whittlesey, Michael K

2017-02-28

Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC) 4 (L)H] 0/+ species (NHC = N-heterocyclic carbene; L = vacant, H 2 , N 2 , CO, MeCN, O 2 , P 4 , SO 2 , H - , F - and Cl - ), as well as selected phosphine analogues [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 (L)H] + (R = i Pr, Cy; L = vacant, O 2 ). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl - , F - ) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru d π orbitals and the unoccupied σ* Ru-H orbital. In [Ru(NHC) 4 (η 2 -O 2 )H] + a δ-interaction with the O 2 ligand results in a low-lying LUMO of d π character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) d π orbital under the L z angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru( i Pr 2 PCH 2 CH 2 P i Pr 2 ) 2 (η 2 -O 2 )H] + (δ = -6.2 ppm) and [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 H] + (ca. -32 ppm, R = i Pr, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC) 4 H] + analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily

Synthesis, spectral and antifungal analysis of diaryldithiophosphates of mono- and dibutyltin(IV): x-ray structure of [{(3,5-CH3)2C6H3O)2PS2}2Sn(nBu)2].

PubMed

Syed, Atiya; Khajuria, Ruchi; Kumar, Sandeep; Jassal, Amanpreet Kaur; Hundal, Maninder S; Pandey, Sushil K

2014-01-01

Diaryldithiophosphate complexes of mono- and dibutyltin(IV) corresponding to [(ArO)(2)PS(2)(n)Sn(nBu)xCl(4-x-n)] (Ar = o-CH(3)C(6)H(4), m-CH(3)C(6)H(4), p-CH(3)C(6)H(4), 4-Cl-3-CH(3)C(6)H(3), (3,5-CH(3))(2)C(6)H(3); n = 1, 2 for x = 1 and n = 2 for x = 2) were successfully isolated and characterized by elemental analyses, IR, multinuclear NMR ((1)H, (13)C, (31)P and (119)Sn) spectroscopy and X-ray analysis. The thermal properties of the complex [(3,5-CH(3))(2)C(6)H(3)O(2)PS(2)](2)Sn(nBu)(2) (12) have been examined by combined DTA/ DTG thermal analyses. Single crystal X-ray analysis of [(3,5-CH(3))(2)C(6)H(3)O(2)PS(2)](2)S(n)(nBu)(2) (12) revealed that two diaryldithiophosphate ions are coordinated to tin atom in an anisobidentate fashion through the sulfur atoms of each dithiophosphate moiety leading to distorted skew-trapezoidal bipyramidal geometry. The antifungal activity depicts that these complexes are active against fungus Penicillium chrysogenium.

Theoretical study of negatively charged Fe(-)-(H2O)(n ≤ 6) clusters.

PubMed

Castro, Miguel

2012-06-14

Interactions of a singly negatively charged iron atom with water molecules, Fe(-)-(H(2)O)(n≤6), in the gas phase were studied by means of density functional theory. All-electron calculations were performed using the B3LYP functional and the 6-311++G(2d,2p) basis set for the Fe, O, and H atoms. In the lowest total energy states of Fe(-)-(H(2)O)(n), the metal-hydrogen bonding is stronger than the metal-oxygen one, producing low-symmetry structures because the water molecules are directly attached to the metal by basically one of their hydrogen atoms, whereas the other ones are involved in a network of hydrogen bonds, which together with the Fe(δ-)-H(δ+) bonding accounts for the nascent hydration of the Fe(-) anion. For Fe(-)-(H(2)O)(3≤n), three-, four-, five-, and six-membered rings of water molecules are bonded to the metal, which is located at the surface of the cluster in such a way as to reduce the repulsion with the oxygen atoms. Nevertheless, internal isomers appear also, lying less than 3 or 5 kcal/mol for n = 2-3 or n = 4-6. These results are in contrast with those of classical TM(+)-(H(2)O)(n) complexes, where the direct TM(+)-O bonding usually produces high symmetry structures with the metal defining the center of the complex. They show also that the Fe(-) anions, as the TM(+) ions, have great capability for the adsorption of water molecules, forming Fe(-)-(H(2)O)(n) structures stabilized by Fe(δ-)-H(δ+) and H-bond interactions.

(1H-pyrazole-κN2)(2,2':6',2''-terpyridine-κ3N,N',N'')platinum(II) bis(perchlorate) nitromethane monosolvate.

PubMed

Akerman, Matthew; Akerman, Kate; Jaganyi, Deogratius; Reddy, Desigan

2011-09-01

The reaction between [PtCl(terpy)]·2H(2)O (terpy is 2,2':6',2''-terpyridine) and pyrazole in the presence of two equivalents of AgClO(4) in nitromethane yields the title compound, [Pt(C(3)H(4)N(2))(C(15)H(11)N(3))](ClO(4))(2)·CH(3)NO(2), as a yellow crystalline solid. Single-crystal X-ray diffraction shows that the dicationic platinum(II) chelate is square planar with the terpyridine ligand occupying three sites and the pyrazole ligand occupying the fourth. The torsion angle subtended by the pyrazole ring relative to the terpyridine chelate is 62.4 (6)°. Density functional theory calculations at the LANL2DZ/PBE1PBE level of theory show that in vacuo the lowest-energy conformation has the pyrazole ligand in an orientation perpendicular to the terpyridine ligand (i.e. 90°). Seemingly, the stability gained by the formation of hydrogen bonds between the pyrazole NH group and the perchlorate anion in the solid-state structure is sufficient for the chelate to adopt a higher-energy conformation.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils.

PubMed

Samad, Md Sainur; Biswas, Ambarish; Bakken, Lars R; Clough, Timothy J; de Klein, Cecile A M; Richards, Karl G; Lanigan, Gary J; Morales, Sergio E

2016-10-26

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N 2 O and N 2 emissions. Soil pH regulates the reduction of N 2 O to N 2 , however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N 2 O emission ratio (N 2 O/(NO + N 2 O + N 2 )) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N 2 O emission ratio and community changes. Soil pH was negatively associated with N 2 O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir &nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N 2 O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N 2 O emission ratio through more efficient conversion of N 2 O to N 2 .

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

NASA Astrophysics Data System (ADS)

Samad, M. D. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-10-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

PubMed Central

Samad, M. d. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-01-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2. PMID:27782174

Tris(5,6-dimethyl-1H-benzimidazole-κN(3))(pyridine-2,6-dicarboxyl-ato-κ(3)O(2),N,O(6))nickel(II).

PubMed

Li, Yue-Hua; Li, Feng-Feng; Liu, Xin-Hua; Zhao, Ling-Yan

2012-06-01

The title mononuclear complex, [Ni(C(7)H(3)NO(4))(C(9)H(10)N(2))(3)], shows a central Ni(II) atom which is coordinated by two carboxyl-ate O atoms and the N atom from a pyridine-2,6-dicarboxyl-ate ligand and by three N atoms from different 5,6-dimethyl-1H--benzimidazole ligands in a distorted octa-hedral geometry. The crystal structure shows intermolecular N-H⋯O hydrogen bonds.

Excessive use of nitrogen in Chinese agriculture results in high N2O/(N2O+N2) product ratio of denitrification, primarily due to acidification of the soils

PubMed Central

Qu, Zhi; Wang, Jingguo; Almøy, Trygve; Bakken, Lars R

2014-01-01

China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long-term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 mM, we measured oxic respiration (R), potential denitrification (D), substrate-induced denitrification, and the denitrification product stoichiometry (NO, N2O, N2). Soils with a history of high fertilizer N levels had high N2O/(N2O+N2) ratios, but only in those field experiments where soil pH had been lowered by N fertilization. By comparing all soils, we found a strong negative correlation between pH and the N2O/(N2O+N2) product ratio (r2 = 0.759, P < 0.001). In contrast, the potential denitrification (D) was found to be a linear function of oxic respiration (R), and the ratio D/R was largely unaffected by soil pH. The immediate effect of liming acidified soils was lowered N2O/(N2O+N2) ratios. The results provide evidence that soil pH has a marginal direct effect on potential denitrification, but that it is the master variable controlling the percentage of denitrified N emitted as N2O. It has been known for long that low pH may result in high N2O/(N2O+N2) product ratios of denitrification, but our documentation of a pervasive pH-control of this ratio across soil types and management practices is new. The results are in good agreement with new understanding of how pH may interfere with the expression of N2O reductase. We argue that the management of soil pH should be high on the agenda for mitigating N2O emissions in the future, particularly for countries where ongoing intensification of plant production is likely to acidify the soils. PMID:24249526

Availability of O(2) and H(2)O(2) on pre-photosynthetic Earth.

PubMed

Haqq-Misra, Jacob; Kasting, James F; Lee, Sukyoung

2011-05-01

Old arguments that free O(2) must have been available at Earth's surface prior to the origin of photosynthesis have been revived by a new study that shows that aerobic respiration can occur at dissolved oxygen concentrations much lower than had previously been thought, perhaps as low as 0.05 nM, which corresponds to a partial pressure for O(2) of about 4 × 10(-8) bar. We used numerical models to study whether such O(2) concentrations might have been provided by atmospheric photochemistry. Results show that disproportionation of H(2)O(2) near the surface might have yielded enough O(2) to satisfy this constraint. Alternatively, poleward transport of O(2) from the equatorial stratosphere into the polar night region, followed by downward transport in the polar vortex, may have brought O(2) directly to the surface. Thus, our calculations indicate that this "early respiration" hypothesis might be physically reasonable.

Octa-akis(4-amino-pyridine)-1κN,2κN-aqua-2κO-μ-carbonato-1:2κO,O':O''-dinickel(II) dichloride penta-hydrate.

PubMed

Fun, Hoong-Kun; Sinthiya, A; Jebas, Samuel Robinson; Ravindran Durai Nayagam, B; Alfred Cecil Raj, S

2008-10-18

In the title compound, [Ni(2)(CO(3))(C(5)H(6)N(2))(8)(H(2)O)]Cl(2)·5H(2)O, one of the the Ni(II) ions is six-coordinated in a distorted octa-hedral geometry, with the equatorial plane defined by four pyridine N atoms from four amino-pyridine ligands, the axial positions being occupied by one water O and a carbonate O atom. The other Ni(II) ion is also six-coordinated, by four other pyridine N atoms from four other amino-pyridine ligands and two carbonate O atoms to complete a distorted octa-hedral geometry. In the crystal structure, mol-ecules are linked into an infinite three-dimensional network by O-H⋯O, N-H⋯Cl, N-H⋯O, O-H⋯N, C-H⋯O, C-H⋯N and C/N-H⋯π inter-actions involving the pyridine rings.

Synthesis, characterization and antimicrobial activity of novel platinum(IV) and palladium(II) complexes with meso-1,2-diphenyl-ethylenediamine-N,N‧-di-3-propanoic acid - Crystal structure of H2-1,2-dpheddp·2HCl·H2O

NASA Astrophysics Data System (ADS)

Radić, Gordana P.; Glođović, Verica V.; Ratković, Zoran R.; Novaković, Slađana B.; Garcia-Granda, Santiago; Roces, Laura; Menéndez-Taboada, Laura; Radojević, Ivana D.; Stefanović, Olgica D.; Čomić, Ljiljana R.; Trifunović, Srećko R.

2012-12-01

In the reaction of meso-1,2-diphenyl-ethylenediamine (1,2-dphen) with neutralized 3-chlor-propanoic acid, the new linear tetradentate edda-like ligand (edda = ethylenediamine-N,N'-diacetic ion) meso-1,2-diphenyl-ethylenediamine-N,N'-di-3-propanoic acid dihydrochloride monohydrate (H2-1,2-dpheddp·2HCl·H2O) was prepared. The corresponding platinum(IV) complex, s-cis-dichlorido-(meso-1,2-diphenyl-ethylenediamine-N,N'-di-3-propanoate)-platinum(IV) ([PtCl2(1,2-dpheddp)]) was synthesized by heating potassium-hexachloridoplatinate(IV) and H2-1,2-dpheddp·2HCl·H2O on steam bath for 12 h with neutralization by means of lithium-hydroxide. The palladium(II) complex, cis-dichlorido-(meso-1,2-diphenyl-ethylenediamine-N,N'-di-3-propanoate)-palladium(II) ([PdCl2(1,2-dpheddp)]) was obtained in the similar way using potassium-tetrachloridopalladate(II), H2-1,2-dpheddp·2HCl·H2O and lithium-hydroxide. The compounds were characterized by elemental analysis and infrared spectroscopy. The spectroscopically predicted structure of the synthesized tetradentate ligand was confirmed by X-ray analysis of the H2-1,2-dpheddp·2HCl·H2O. Antimicrobial activity of the ligand and corresponding palladium(II) and platinum(IV) complexes is investigated against 25 species of microorganisms. Testing is preformed by microdilution method and minimum inhibitory concentrations (MIC) and minimum microbicidal concentration (MMC) have been determined. The difference between antimicrobial activity of the ligand and corresponding platinum(IV) and palladium(II) complex is noticed and, in general, palladium(II) complex was the most active.

trans-Bis(azido-kappaN)bis(pyridine-2-carboxamide-kappa2N1,O2)nickel(II).

PubMed

Daković, Marijana; Popović, Zora

2007-11-01

In the title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N-H...N hydrogen bonds.

H2/O2 three-body rates at high temperatures

NASA Technical Reports Server (NTRS)

Marinelli, William J.; Kessler, William J.; Carleton, Karen L.

1991-01-01

Hydrogen atoms are produced in the presence of excess O2, and the first-order decay are studied as a function of temperature and pressure in order to obtain the rate coefficient for the three-body reaction between H-atoms and O2. Attention is focused on the kinetic scheme employed as well as the reaction cell and photolysis and probe laser system. A two-photon laser-induced fluorescence technique is employed to detect H-atoms without optical-thickness or O2-absorption problems. Results confirm measurements reported previously for the H + O2 + N2 reaction at 300 K and extend these measurements to higher temperatures. Preliminary data indicate non-Arrehenius-type behavior of this reaction rate coefficient as a function of temperature. Measurements of the rate coefficient for H + O2 + Ar reaction at 300 K give a rate coefficient of 2.1 +/- 0.1 x 10 to the -32nd cm exp 6/molecule sec.

Degradation mechanism of alachlor during direct ozonation and O(3)/H(2)O(2) advanced oxidation process.

PubMed

Qiang, Zhimin; Liu, Chao; Dong, Bingzhi; Zhang, Yalei

2010-01-01

The degradation of alachlor by direct ozonation and advanced oxidation process O(3)/H(2)O(2) was investigated in this study with focus on identification of degradation byproducts. The second-order reaction rate constant between ozone and alachlor was determined to be 2.5+/-0.1M(-1)s(-1) at pH 7.0 and 20 degrees C. Twelve and eight high-molecular-weight byproducts (with the benzene ring intact) from alachlor degradation were identified during direct ozonation and O(3)/H(2)O(2), respectively. The common degradation byproducts included N-(2,6-diethylphenyl)-methyleneamine, 8-ethyl-3,4-dihydro-quinoline, 8-ethyl-quinoline, 1-chloroacetyl-2-hydro-3-ketone-7-acetyl-indole, 2-chloro-2',6'-diacetyl-N-(methoxymethyl)acetanilide, 2-chloro-2'-acetyl-6'-ethyl-N-(methoxymethyl)-acetanilide, and two hydroxylated alachlor isomers. In direct ozonation, four more byproducts were also identified including 1-chloroacetyl-2,3-dihydro-7-ethyl-indole, 2-chloro-2',6'-ethyl-acetanilide, 2-chloro-2',6'-acetyl-acetanilide and 2-chloro-2'-ethyl-6'-acetyl-N-(methoxymethyl)-acetanilide. Degradation of alachlor by O(3) and O(3)/H(2)O(2) also led to the formation of low-molecular-weight byproducts including formic, acetic, propionic, monochloroacetic and oxalic acids as well as chloride ion (only detected in O(3)/H(2)O(2)). Nitrite and nitrate formation was negligible. Alachlor degradation occurred via oxidation of the arylethyl group, N-dealkylation, cyclization and cleavage of benzene ring. After O(3) or O(3)/H(2)O(2) treatment, the toxicity of alachlor solution examined by the Daphnia magna bioassay was slightly reduced. 2009 Elsevier Ltd. All rights reserved.

Micropore Formation of [Zn2(Oxac) (Taz)2]·(H2O)2.5 via CO2 Adsorption.

PubMed

Zubir, Moondra; Hamasaki, Atom; Iiyama, Taku; Ohta, Akira; Ohki, Hiroshi; Ozeki, Sumio

2017-01-24

As-synthesized [Zn 2 (Oxac) (Taz) 2 ]·(H 2 O) 2.5 , referred to as ZOTW 2.5 , was prepared from aqueous methanol solutions of Zn 5 (CO 3 ) 2 (OH) 6 and two kinds of ligands of 1,2,4-triazole (Taz) and oxalic acid (Oxac) at 453 K for 12 h. The crystal structure was determined by the Rietveld method. As-synthesized ZOTW 2.5 was pretreated at 383 K and 1 mPa for t pt h, ZOTW x (t pt h). ZOTW x (≥3h) showed a type I adsorption isotherm for N 2 at 77 K having a saturation amount (V s ) of 180 mg/g, but that pretreated shortly showed only 1/10 in V s . CO 2 was adsorbed at 303 K in sigmoid on nonporous ZOTW x (≤2h) and in Langmuir-type on ZOTW x (≥3h) to reach the adsorption amount of 120 mg/g at 700 Torr. N 2 adsorption on ZOTW x (≤2h)deCO 2 , degassed after CO 2 adsorption on ZOTW x (≤2h), was promoted 5-fold from 180 mg/g on ZOTW x (t pt h) and ZOTW x (≥3h)deCO 2 up to ca. 1000 mg/g. The interaction of CO 2 and H 2 O molecules in micropores may lead to a new route for micropore formation.

NCI calculations for understanding a physical phase transition in (C6H14N2)[Mn(H2O)6](SeO4)2

NASA Astrophysics Data System (ADS)

Naïli, Houcine; François, Michel; Norquist, Alexander J.; Rekik, Walid

2017-12-01

An organically templated manganese selenate, (C6H14N2)[Mn(H2O)6](SeO4)2, has been synthesized by slow evaporation and crystallographically characterized. The title compound crystallizes at room temperature in the monoclinic centrosymmetric space group P21/n, with the following unit cell parameters: a = 7.2373(4) Å; b = 12.5600(7) Å; c = 10.1945(7) Å; β = 91.155(4)°, V = 926.50(10) Å3and Z = 2. Its crystal structure is built of manganese(II) cations coordinated by six water molecules in octahedral geometry, disordered dabcodiium cations and selenate anions, resulting in an extensive hydrogen-bonding network. Differential scanning calorimetry (DSC) measurement indicated that the precursor undergoes a reversible phase transition at about 216 and 218 K during the cooling and heating processes respectively. Below this temperature the title compound is noncentrosymmetric with space group P21 and lattice parameters a = 7.2033(8) Å; b = 12.4981(13) Å; c = 10.0888(11) Å; β = 91.281(2)°, V = 908.04(17) Å3 and Z = 2. The disorder-order transformation of the C atoms of (C6H14N2)2+ cation may drive the structural phase transition. The low temperature phase obtained by breaking symmetry presents a fully ordered structure. The noncovalent interaction (NCI) method was used not only to locate, quantify, and visualize intermolecular interactions in the high and low temperature phases but also to confirm the phase transition detected by DSC measurement. The thermal decomposition of this new compound proceeds through four stages giving rise to the manganese oxide as final product at 850 °C.

Evolution of resistive switching mechanism through H2O2 sensing by using TaOx-based material in W/Al2O3/TaOx/TiN structure

NASA Astrophysics Data System (ADS)

Chakrabarti, Somsubhra; Panja, Rajeswar; Roy, Sourav; Roy, Anisha; Samanta, Subhranu; Dutta, Mrinmoy; Ginnaram, Sreekanth; Maikap, Siddheswar; Cheng, Hsin-Ming; Tsai, Ling-Na; Chang, Ya-Ling; Mahapatra, Rajat; Jana, Debanjan; Qiu, Jian-Tai; Yang, Jer-Ren

2018-03-01

Understanding of resistive switching mechanism through H2O2 sensing and improvement of switching characteristics by using TaOx-based material in W/Al2O3/TaOx/TiN structure have been reported for the first time. Existence of amorphous Al2O3/TaOx layer in the RRAM devices has been confirmed by transmission electron microscopy. By analyzing the oxidation states of Ta2+/Ta5+ for TaOx switching material and W0/W6+ for WOx layer at the W/TaOx interface through X-ray photoelectron spectroscopy and H2O2 sensing, the reduction-oxidation mechanism under Set/Reset occurs only in the TaOx layer for the W/Al2O3/TaOx/TiN structures. This leads to higher Schottky barrier height at the W/Al2O3 interface (0.54 eV vs. 0.46 eV), higher resistance ratio, and long program/erase endurance of >108 cycles with 100 ns pulse width at a low operation current of 30 μA. Stable retention of more than 104 s at 85 °C is also obtained. Using conduction mechanism and reduction-oxidation reaction, current-voltage characteristic has been simulated. Both TaOx and WOx membranes have high pH sensitivity values of 47.65 mV/pH and 49.25 mV/pH, respectively. Those membranes can also sense H2O2 with a low concentration of 1 nM in an electrolyte-insulator-semiconductor structure because of catalytic activity, while the Al2O3 membrane does not show sensing. The TaOx material in W/Al2O3/TaOx/TiN structure does not show only a path towards high dense, small size memory application with understanding of switching mechanism but also can be used for H2O2 sensors.

The pH dependency of N-converting enzymatic processes, pathways and microbes: effect on net N2 O production.

PubMed

Blum, Jan-Michael; Su, Qingxian; Ma, Yunjie; Valverde-Pérez, Borja; Domingo-Félez, Carlos; Jensen, Marlene Mark; Smets, Barth F

2018-05-01

Nitrous oxide (N 2 O) is emitted during microbiological nitrogen (N) conversion processes, when N 2 O production exceeds N 2 O consumption. The magnitude of N 2 O production vs. consumption varies with pH and controlling net N 2 O production might be feasible by choice of system pH. This article reviews how pH affects enzymes, pathways and microorganisms that are involved in N-conversions in water engineering applications. At a molecular level, pH affects activity of cofactors and structural elements of relevant enzymes by protonation or deprotonation of amino acid residues or solvent ligands, thus causing steric changes in catalytic sites or proton/electron transfer routes that alter the enzymes' overall activity. Augmenting molecular information with, e.g., nitritation or denitrification rates yields explanations of changes in net N 2 O production with pH. Ammonia oxidizing bacteria are of highest relevance for N 2 O production, while heterotrophic denitrifiers are relevant for N 2 O consumption at pH > 7.5. Net N 2 O production in N-cycling water engineering systems is predicted to display a 'bell-shaped' curve in the range of pH 6.0-9.0 with a maximum at pH 7.0-7.5. Net N 2 O production at acidic pH is dominated by N 2 O production, whereas N 2 O consumption can outweigh production at alkaline pH. Thus, pH 8.0 may be a favourable pH set-point for water treatment applications regarding net N 2 O production. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Quantitative Measurements of HO2 and other products of n-butane oxidation (H2O2, H2O, CH2O, and C2H4) at elevated temperatures by direct coupling of a jet-stirred reactor with sampling nozzle and cavity ring-down spectroscopy (cw-CRDS).

PubMed

Djehiche, Mokhtar; Le Tan, Ngoc Linh; Jain, Chaithanya D; Dayma, Guillaume; Dagaut, Philippe; Chauveau, Christian; Pillier, Laure; Tomas, Alexandre

2014-11-26

For the first time quantitative measurements of the hydroperoxyl radical (HO2) in a jet-stirred reactor were performed thanks to a new experimental setup involving fast sampling and near-infrared cavity ring-down spectroscopy at low pressure. The experiments were performed at atmospheric pressure and over a range of temperatures (550-900 K) with n-butane, the simplest hydrocarbon fuel exhibiting cool flame oxidation chemistry which represents a key process for the auto-ignition in internal combustion engines. The same technique was also used to measure H2O2, H2O, CH2O, and C2H4 under the same conditions. This new setup brings new scientific horizons for characterizing complex reactive systems at elevated temperatures. Measuring HO2 formation from hydrocarbon oxidation is extremely important in determining the propensity of a fuel to follow chain-termination pathways from R + O2 compared to chain branching (leading to OH), helping to constrain and better validate detailed chemical kinetics models.

Crystal structure of tetra­aqua­[2-(pyridin-2-yl)-1H-imidazole-κ2 N 2,N 3]iron(II) sulfate

PubMed Central

Setifi, Zouaoui; Setifi, Fatima; Francuski, Bojana M.; Novaković, Sladjana B.; Merazig, Hocine

2015-01-01

In the title compound, [Fe(C8H7N3)(H2O)4]SO4, the central FeII ion is octa­hedrally coordinated by two N atoms from the bidentate 2-(pyridin-2-yl)-1H-imidazole ligand and by four O atoms of the aqua ligands. The largest deviation from the ideal octa­hedral geometry is reflected by the small N—Fe—N bite angle of 76.0 (1)°. The Fe—N coordination bonds have markedly different lengths [2.1361 (17) and 2.243 (2) Å], with the shorter one to the pyrimidine N atom. The four Fe—O coordination bond lengths vary from 2.1191 (18) to 2.1340 (17) Å. In the crystal, the cations and anions are arranged by means of medium-strength O—H⋯O hydrogen bonds into layers parallel to the ab plane. Neighbouring layers further inter­connect by N—H⋯O hydrogen bonds involving the imidazole fragment as donor group to one sulfate O atom as an acceptor. The resulting three-dimensional network is consolidated by C—H⋯O, C—H⋯π and π–π inter­actions. PMID:26029386

VUV photoionization cross sections of HO2, H2O2, and H2CO.

PubMed

Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

2015-02-26

The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra.

CO2 in solid para-hydrogen: spectral splitting and the CO2···(o-H2)n clusters.

PubMed

Du, Jun-He; Wan, Lei; Wu, Lei; Xu, Gang; Deng, Wen-Ping; Liu, An-Wen; Chen, Yang; Hu, Shui-Ming

2011-02-17

Complicated high-resolution spectral structures are often observed for molecules doped in solid molecular hydrogen. The structures can result from miscellaneous effects and are often interpreted differently in references. The spectrum of the ν(3) band of CO(2) in solid para-H(2) presents a model system which exhibits rich spectral structures. With the help of the potential energy simulation of the CO(2) molecule doped in para-hydrogen matrix, and extensive experiments with different CO(2) isotopologues and different ortho-hydrogen concentrations in the matrix, the spectral features observed in p-H(2) matrix are assigned to the CO(2)···(o-H(2))(n) clusters and also to energy level splitting that is due to different alignments of the doped CO(2) molecules in the matrix. The assignments are further supported by the dynamics analysis and also by the spectrum recorded with sample codoped with O(2) which serves as catalyst transferring o-H(2) to p-H(2) in the matrix at 4 K temperature. The observed spectral features of CO(2)/pH(2) can potentially be used as an alternative readout of the temperature and orthohydrogen concentration in the solid para-hydrogen.

H2O Paradox and its Implications on H2O in Moon

NASA Astrophysics Data System (ADS)

Zhang, Youxue

2017-04-01

The concentration of H2O in the mantle of a planetary body plays a significant role in the viscosity and partial melting and hence the convection and evolution of the planetary body. Even though the composition of the primitive terrestrial mantle (PTM) is thought to be well known [1-2], the concentration of H2O in PTM remains paradoxial because different methods of estimation give different results [3]: Using H2O/Ce ratio in MORB and OIB and Ce concentration in PTM, the H2O concentration in PTM would be (300÷×1.5) ppm; using mass balance by adding surface water to the mantle [3-4], H2O concentration in PTM would be (900÷×1.3) ppm [2-3]. The inconsistency based on these two seemingly reliable methods is referred to as the H2O paradox [3]. For Moon, H2O contents in the primitive lunar mantle (PLM) estimated from H2O in plagioclase in lunar anorthosite and that from H2O/Ce ratio in melt inclusions are roughly consistent at ˜110 ppm [5-6] even though there is still debate about the volatile depletion trend [7]. One possible solution to the H2O paradox in PTM is to assume that early Earth experienced whole mantle degassing, which lowered the H2O/Ce ratio in the whole mantle but without depleting Ce in the mantle. The second possible solution is that some deep Earth reservoirs with high H2O/Ce ratios have not been sampled by MORB and OIB. Candidates include the transition zone [8] and the D" layer. The third possible solution is that ocean water only partially originated from mantle degassing, but partially from extraterrestrial sources such as comets [9-10]. At present, there is not enough information to determine which scenario is the answer to the H2O paradox. On the other hand, each scenario would have its own implications to H2O in PLM. If the first scenario applies to Moon, because degassed H2O or H2 would have escaped from the lunar surface, the very early lunar mantle could have much higher H2O [11] than that obtained using the H2O/Ce ratio method. The

Infrared spectra and anharmonic coupling of proton-bound nitrogen dimers N2-H+-N2, N2-D+-N2, and 15N2-H+-15N2 in solid para-hydrogen.

PubMed

Liao, Hsin-Yi; Tsuge, Masashi; Tan, Jake A; Kuo, Jer-Lai; Lee, Yuan-Pern

2017-08-09

The proton-bound nitrogen dimer, N 2 -H + -N 2 , and its isotopologues were investigated by means of vibrational spectroscopy. These species were produced upon electron bombardment of mixtures of N 2 (or 15 N 2 ) and para-hydrogen (p-H 2 ) or normal-D 2 (n-D 2 ) during deposition at 3.2 K. Reduced-dimension anharmonic vibrational Schrödinger equations were constructed to account for the strong anharmonic effects in these protonated species. The fundamental lines of proton motions in N 2 -H + -N 2 were observed at 715.0 (NH + N antisymmetric stretch, ν 4 ), 1129.6 (NH + N bend, ν 6 ), and 2352.7 (antisymmetric NN/NN stretch, ν 3 ) cm -1 , in agreement with values of 763, 1144, and 2423 cm -1 predicted with anharmonic calculations using the discrete-variable representation (DVR) method at the CCSD/aug-cc-pVDZ level. The lines at 1030.2 and 1395.5 cm -1 were assigned to combination bands involving nν 2 + ν 4 (n = 1 and 2) according to theoretical calculations; ν 2 is the N 2 N 2 stretching mode. For 15 N 2 -H + - 15 N 2 in solid p-H 2 , the corresponding major lines were observed at 710.0 (ν 4 ), 1016.7 (ν 2 + ν 4 ), 1124.3 (ν 6 ), 1384.8 (2ν 2 + ν 4 ), and 2274.9 (ν 3 ) cm -1 . For N 2 -D + -N 2 in solid n-D 2 , the corresponding major lines were observed at 494.0 (ν 4 ), 840.7 (ν 2 + ν 4 ), 825.5 (ν 6 ), and 2356.2 (ν 3 ) cm -1 . In addition, two lines at 762.0 (weak) and 808.3 cm -1 were tentatively assigned to be some modes of N 2 -H + -N 2 perturbed or activated by a third N 2 near the proton.

A Novel Dimeric Ni-Substituted beta-Keggin Silicotungstate: Structure and Magnetic Properties of K(12)[{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)].20H(2)O.

PubMed

Kortz, Ulrich; Jeannin, Yves P.; Tézé, André; Hervé, Gilbert; Isber, Samih

1999-08-09

The novel dimeric polyoxometalate [{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)](12)(-) (1) has been synthesized and characterized by IR spectroscopy, polarography, elemental analysis, thermogravimetric analysis, and magnetic measurements. An X-ray single-crystal analysis was carried out on K(12)[{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)].20H(2)O, which crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.701(4) Å, b = 24.448(11) Å, c = 13.995(5) Å, beta = 99.62(3) degrees, and Z = 4. The anion consists of two [beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)] Keggin moieties linked via two OH bridging groups, leading to a planar Ni(2)(OH)(2) unit. The two half-units are related by an inversion center and each contain one Ni atom in the rotated triad. The formation of the new anion involves insertion, isomerization, and dimerization. Magnetic measurements show that the central Ni(4) unit exhibits ferromagnetic (J' = 4.14 cm(-)(1)) as well as weak antiferromagnetic (J = -0.65 cm(-)(1)) Ni-Ni exchange interactions.

Characteristics of supercritical turbulence from Direct Numerical Simulations of C(sub 7)H(sub 16)/N(sub 2) and O(sub 2)/H(sub 2)

NASA Technical Reports Server (NTRS)

Okong'o, N. A.; Bellan, J.

2003-01-01

Analysis of Direct Numerical Simulations (DNS) transitional states of temporal, supercritical mixing layers for C7H16/N2 and O2/H2 shows that the evolution of all layers is characterized by the formation of high-density-gradient magnitude (HDGM) regions.

Comparative study of the degradation of real textile effluents by photocatalytic reactions involving UV/TiO2/H2O2 and UV/Fe2+/H2O2 systems.

PubMed

Garcia, J C; Oliveira, J L; Silva, A E C; Oliveira, C C; Nozaki, J; de Souza, N E

2007-08-17

This work investigated the treatability of real textile effluents using several systems involving advanced oxidation processes (AOPs) such as UV/H2O2, UV/TiO2, UV/TiO2/H2O2, and UV/Fe2+/H2O2. The efficiency of each technique was evaluated according to the reduction levels observed in the UV absorbance of the effluents, COD, and organic nitrogen reduction, as well as mineralization as indicated by the formation of ammonium, nitrate, and sulfate ions. The results indicate the association of TiO2 and H2O2 as the most efficient treatment for removing organic pollutants from textile effluents. In spite of their efficiency, Fenton reactions based treatment proved to be slower and exhibited more complicated kinetics than the ones using TiO2, which are pseudo-first-order reactions. Decolorization was fast and effective in all the experiments despite the fact that only H2O2 was used.

Laboratory IR Detection of H2O, CO2 in Ion-Irradiated Ices Relevant to Europa

NASA Technical Reports Server (NTRS)

Moore, Marla H.; Hudson, R. L.

1999-01-01

Hydrogen peroxide has been identified on Europa (Carlson et al. 1999) based in part on the 3.50 micron absorption feature observed in Galileo NIMS spectra. The observed feature was fitted with laboratory reflectance spectra of H2O + H2O2. Since condensed phase molecules on Europa (H2O, CO2, SO2, and H2O2) are bombarded with a significant flux of energetic particles (H(+), O(n+), S(n+) and e-), we examined the proton irradiation of H2O at 80 K and the conditions for the IR detection of H2O2 near 3.5 microns. Contrary to expectations, H2O2 was not detected if pure H2O ice was irradiated at 80 K. This was an unexpected result since, H2O2 was detected if pure H2O was irradiated at 18 K. We find, however, that if H2O ice contains either O2 or CO2 then H2O2 is detected after irradiation at 80 K (Moore and Hudson, 1999). The source of O2 for the H2O ice on Europa could come from surface interactions with the tenuous oxygen atmosphere, or from the bombardment of the surface by O(n+).

Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

PubMed Central

Zhang, Guo-Fang; Cai, Mei-Yu; Jing, Ping; He, Chong; Li, Ping; Zhao, Feng-Qi; Li, Ji-Zhen; Fan, Xue-Zhong; Ng, Seik Weng

2010-01-01

Two transition-metal compounds derived from 2,4-dinitroimidazole, {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O, 1, and Pb(DNI)2(H2O)4, 2, were characterized by elemental analysis, FT-IR, TG-DSC and X-ray single-crystal diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 26.826(3), b = 7.7199(10), c = 18.579(2) Å, β = 111.241(2)° and Z = 4; 2: monoclinic, space group C2/c, a = 6.5347(6), b = 17.1727(17), c = 14.1011(14) Å, β = 97.7248(10) and Z = 4. Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon. PMID:20526419

Kinetic removal of haloacetonitrile precursors by photo-based advanced oxidation processes (UV/H2O2, UV/O3, and UV/H2O2/O3).

PubMed

Srithep, Sirinthip; Phattarapattamawong, Songkeart

2017-06-01

The objective of the study is to evaluate the performance of conventional treatment process (i.e., coagulation, flocculation, sedimentation and sand filtration) on the removals of haloacetonitrile (HAN) precursors. In addition, the removals of HAN precursors by photo-based advanced oxidation processes (Photo-AOPs) (i.e., UV/H 2 O 2 , UV/O 3 , and UV/H 2 O 2 /O 3 ) are investigated. The conventional treatment process was ineffective to remove HAN precursors. Among Photo-AOPs, the UV/H 2 O 2 /O 3 was the most effective process for removing HAN precursors, followed by UV/H 2 O 2 , and UV/O 3 , respectively. For 20min contact time, the UV/H 2 O 2 /O 3 , UV/H 2 O 2 , and UV/O 3 suppressed the HAN formations by 54, 42, and 27% reduction. Increasing ozone doses from 1 to 5 mgL -1 in UV/O 3 systems slightly improved the removals of HAN precursors. Changes in pH (6-8) were unaffected most of processes (i.e., UV, UV/H 2 O 2 , and UV/H 2 O 2 /O 3 ), except for the UV/O 3 system that its efficiency was low in the weak acid condition. The pseudo first-order kinetic constant for removals of dichloroacetonitrile precursors (k' DCANFP ) by the UV/H 2 O 2 /O 3 , UV/H 2 O 2 and standalone UV systems were 1.4-2.8 orders magnitude higher than the UV/O 3 process. The kinetic degradation of dissolved organic nitrogen (DON) tended to be higher than the k' DCANFP value. This study firstly differentiates the kinetic degradation between DON and HAN precursors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of H2O, CO2, and N2 Air Contaminants on Critical Airside Strain Rates for Extinction of Hydrogen-Air Counterflow Diffusion Flames

NASA Technical Reports Server (NTRS)

Pellett, G. L.; Wilson, L. G.; Northam, G. B.; Guerra, Rosemary

1989-01-01

Coaxial tubular opposed jet burners (OJB) were used to form dish shaped counterflow diffusion flames (CFDF), centered by opposing laminar jets of H2, N2 and both clean and contaminated air (O2/N2 mixtures) in an argon bath at 1 atm. Jet velocities for flame extinction and restoration limits are shown versus wide ranges of contaminant and O2 concentrations in the air jet, and also input H2 concentration. Blowoff, a sudden breaking of CFDF to a stable ring shape, occurs in highly stretched stagnation flows and is generally believed to measure kinetically limited flame reactivity. Restore, a sudden restoration of central flame, is a relatively new phenomenon which exhibits a H2 dependent hysteresis from Blowoff. For 25 percent O2 air mixtures, mole for mole replacement of 25 percent N2 contaminant by steam increased U(air) or flame strength at Blowoff by about 5 percent. This result is consistent with laminar burning velocity results from analogous substitution of steam for N2 in a premixed stoichiometric H2-O2-N2 (or steam) flame, shown by Koroll and Mulpuru to promote a 10 percent increase in experimental and calculated laminar burning velocity, due to enhanced third body efficiency of water in: H + O2 + M yields HO2 + M. When the OJB results were compared with Liu and MacFarlane's experimental laminar burning velocity of premixed stoichiometric H2 + air + steam, a crossover occurred, i.e., steam enhanced OJB flame strength at extinction relative to laminar burning velocity.

Production of N2O/+/ by reaction of metastable O2/+/ ions with N2

NASA Technical Reports Server (NTRS)

Ajello, J. M.; Rayermann, P.

1975-01-01

Photoionization mass spectrometry examination of the production of N2O(+) was undertaken to determine whether N2(+) or O2(+) ions are responsible for onset of N2O(+). It appears that the N2(+) ion does not contribute significantly to the production of N2O(+) in this experiment. Therefore, it is clear that excited O2(+) is responsible for the formation of N2O(+) near the appearance potential of these ions.

The reaction of H2O2 with NO2 and NO

NASA Technical Reports Server (NTRS)

Gray, D.; Lissi, E.; Heicklen, J.

1972-01-01

The reactions of NO and NO2 with H2O2 have been examined at 25 C. Reaction mixtures were monitored by continuously bleeding through a pinhole into a monopole mass spectrometer. NO2 was also monitored by its optical absorption in the visible part of the spectrum. Reaction mixtures containing initially 1.5 - 2.5 torr of NO2 and 0.8 - 1.4 torr of H2O2 or 1 - 12 torr of NO and 0.5 - 1.5 torr of H2O2 were studied. The H2O2 - NO reaction was complex. There was an induction period followed by a marked acceleration in reactant removal. The final products of the reaction, NO2, probably H2O, and possibly HONO2 were produced mainly after all the H2O2 was removed. The HONO intermediate was shown to disproportionate to NO2 + NO + H2O in a relatively slow first order reaction. The acceleration in H2O2 removal after the NO - H2O2 reaction is started is caused by NO2 catalysis.

Synthesis and characterization of two novel inorganic/organic hybrid materials based on polyoxomolybdate clusters: (C5H5N5)2(C5H6N5)4[(HAsO4)2Mo6O18]·11H2O and Na2(Himi)3[SeMo6O21(CH3COO)3]·6H2O

NASA Astrophysics Data System (ADS)

Ayed, Meriem; Mestiri, Imen; Ayed, Brahim; Haddad, Amor

2017-01-01

Two new organic-inorganic hybrid compound, (C5H5N5)2(C5H6N5)4[(HAsO4)2Mo6O18]·11H2O (I) and Na2(Himi)3[SeMo6O21(CH3COO)3]·6H2O (II) were synthesized and structurally characterized by scanning electron microscopy (SEM), elemental analyses, FTIR, UV spectroscopy, thermal stability analysis, XRD and single crystal X-ray diffraction. Crystal data: (I) triclinic system, space group P-1, a = 11,217 (9) Å, b = 11,637 (8) Å, c = 14,919 (8) Å, α = 70,90 (5)°, β = 70,83 (2)°, γ = 62,00(1)° and Z = 1; (II) triclinic system, space group P-1, a = 10.6740(1) Å, b = 10.6740(1) Å, c = 20.0570(1) Å, α = 76.285(1)°, β = 82.198(2)°, γ = 87.075(1)°, Z = 1. The crystal structure of (I) can be described by infinite polyanions [(HAsO4)2Mo6O18]4- organized with water molecules in layers parallel to the c-direction; adjacent layers are further joined up by hydrogen bonding interactions with organic groups which were associated in chains spreading along the b-direction. The structure of (II) consists of functionalized selenomolybdate clusters [SeMo6O21(CH3COO)3]5-, protonated imidazole cations, sodium ions and lattice water molecules, which are held together to generate a three-dimensional supramolecular network via hydrogen-bonding interaction. Furthermore, the electrochemical properties of these compounds have been studied.

Electrochemical Quantification of Extracellular Local H2O2 Kinetics Originating from Single Cells.

PubMed

Bozem, Monika; Knapp, Phillip; Mirčeski, Valentin; Slowik, Ewa J; Bogeski, Ivan; Kappl, Reinhard; Heinemann, Christian; Hoth, Markus

2017-05-15

H 2 O 2 is produced by all eukaryotic cells under physiological and pathological conditions. Due to its enormous relevance for cell signaling at low concentrations and antipathogenic function at high concentrations, precise quantification of extracellular local H 2 O 2 concentrations ([H 2 O 2 ]) originating from single cells is required. Using a scanning electrochemical microscope and bare platinum disk ultramicroelectrodes, we established sensitive long-term measurements of extracellular [H 2 O 2 ] kinetics originating from single primary human monocytes (MCs) ex vivo. For the electrochemical techniques square wave voltammetry, cyclic and linear scan voltammetry, and chronoamperometry, detection limits for [H 2 O 2 ] were determined to be 5, 50, and 500 nM, respectively. Following phorbol ester stimulation, local [H 2 O 2 ] 5-8 μm above a single MC increased by 3.4 nM/s within the first 10 min before reaching a plateau. After extracellular addition of H 2 O 2 to an unstimulated MC, the local [H 2 O 2 ] decreased on average by 4.2 nM/s due to degradation processes of the cell. Using the scanning mode of the setup, we found that H 2 O 2 is evenly distributed around the producing cell and can still be detected up to 30 μm away from the cell. The electrochemical single-cell measurements were validated in MC populations using electron spin resonance spectroscopy and the Amplex ® UltraRed assay. Innovation and Conclusion: We demonstrate a highly sensitive, spatially, and temporally resolved electrochemical approach to monitor dynamics of production and degradation processes for H 2 O 2 separately. Local extracellular [H 2 O 2 ] kinetics originating from single cells is quantified in real time. Antioxid. Redox Signal. 00, 000-000.

Oxidative degradation of endotoxin by advanced oxidation process (O3/H2O2 & UV/H2O2).

PubMed

Oh, Byung-Taek; Seo, Young-Suk; Sudhakar, Dega; Choe, Ji-Hyun; Lee, Sang-Myeong; Park, Youn-Jong; Cho, Min

2014-08-30

The presence of endotoxin in water environments may pose a serious public health hazard. We investigated the effectiveness of advanced oxidative processes (AOP: O3/H2O2 and UV/H2O2) in the oxidative degradation of endotoxin. In addition, we measured the release of endotoxin from Escherichia coli following typical disinfection methods, such as chlorine, ozone alone and UV, and compared it with the use of AOPs. Finally, we tested the AOP-treated samples in their ability to induce tumor necrosis factor alpha (TNF-α) in mouse peritoneal macrophages. The production of hydroxyl radical in AOPs showed superior ability to degrade endotoxin in buffered solution, as well as water samples from Korean water treatment facilities, with the ozone/H2O2 being more efficient compared to UV/H2O2. In addition, the AOPs proved effective not only in eliminating E. coli in the samples, but also in endotoxin degradation, while the standard disinfection methods lead to the release of endotoxin following the bacteria destruction. Furthermore, in the experiments with macrophages, the AOPs-deactivated endotoxin lead to the smallest induction of TNF-α, which shows the loss of inflammation activity, compared to ozone treatment alone. In conclusion, these results suggest that AOPs offer an effective and mild method for endotoxin degradation in the water systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Vibrational energy transfer and relaxation in O2 and H2O.

PubMed

Huestis, David L

2006-06-01

Near-resonant vibrational energy exchange between oxygen and water molecules is an important process in the Earth's atmosphere, combustion chemistry, and the chemical oxygen iodine laser (COIL). The reactions in question are (1) O2(1) + O2(0) --> O2(0) + O2(0); (2) O2(1) + H2O(000) --> O2(0) + H2O(000); (3) O2(1) + H2O(000) <--> O2(0) + H2O(010); (4) H2O(010) + H2O(000) --> H2O(000) + H2O(000); and (5) H2O(010) + O2(0) --> H2O(000) + O2(0). Reanalysis of the data available in the chemical kinetics literature provides reliable values for rate coefficients for reactions 1 and 4 and strong evidence that reactions 2 and 5 are slow in comparison with reaction 3. Analytical solution of the chemical rate equations shows that previous attempts to measure the rate of reaction 3 are unreliable unless the water mole fraction is higher than 1%. Reanalysis of data from the only experiment satisfying this constraint provides a rate coefficient of (5.5 +/- 0.4) x 10(-13) cm3/s at room temperature, between the values favored by the atmospheric and laser modeling communities.

A novel highly efficient adsorbent {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n: Synthesis, crystal structure, magnetic and arsenic (V) absorption capacity

NASA Astrophysics Data System (ADS)

Zhang, Chong; Xiao, Yu; Qin, Yan; Sun, Quanchun; Zhang, Shuhua

2018-05-01

A novel highly efficient adsorbent-microporous tetranuclear Co(II)-based polymer, {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n (1, H3L = 4-(N,N‧-bis(4-carboxybenzyl)amino) benzenesulfonic acid, 4,4‧-bipy = 4,4‧-bipyridine), was hydrothermally synthesized. The complex 1 is a metal-organic framework (MOF) material which was characterized by single-crystal X-ray diffraction, BET and platon software. Co-MOF (complex 1) reveals excellent adsorption property. The capacity of Co-MOF to remove arsenic As(V) from sodium arsenate aqueous solutions was investigated (The form of As(V) is AsO43-). The experimental results showed that Co-MOF had a higher stable and relatively high As(V) removal rate (> 98%) at pH 4-10. The adsorption kinetics followed a pseudo-second-order kinetic model, and the adsorption isotherm followed the Langmuir equation. Co-MOF exhibits a very high adsorption capacity of As(V) in aqueous solution (Qmax of 96.08 mg/g). Finally, the optimal adsorption conditions for the model were obtained through a Box-Behnken response surface experiment which was designed with adsorption time, dose, temperature and rotational speed of the shaker as the influencing factors to determine two-factor interaction effects. Co-MOF was further characterized using FTIR, PXRD, X-ray photoelectron spectroscopy before and after adsorption As (V). The magnetism of Co-MOF was also discussed.

The role of electric field in enhancing separation of gas molecules (H2S, CO2, H2O) on VIB modified g-C3N4 (0 0 1)

NASA Astrophysics Data System (ADS)

Wang, Fang; Li, Penghui; Wei, Shiqian; Guo, Jiaxing; Dan, Meng; Zhou, Ying

2018-07-01

In this study, the first-principles calculations were performed to investigate the adsorption behaviors of gas molecules H2S, CO2 and H2O on Cr, Mo and W modified g-C3N4 (0 0 1) surface. The results show that H2S, CO2 and H2O are physically adsorbed on the pristine g-C3N4, while the adsorption becomes chemisorbed due to the introduction of transition metals which significantly improve the interfacial electron transfer and narrow the band gap of g-C3N4 (0 0 1). Furthermore, it is found that the adsorption behaviors can be greatly influenced by the applied electric field. The adsorption energy is generally arranged in the order of Eads(H2S) > Eads(H2O) > Eads(CO2), and W/g-C3N4 (0 0 1) exhibits the best separation capability. The study could provide a versatile approach to selectively capture and separate the mixed gases in the catalytic reactions by controlling the applied intensity of electric field.

Revisit the landscape of protonated water clusters H+(H2O)n with n = 10-17: An ab initio global search.

PubMed

Shi, Ruili; Li, Keyao; Su, Yan; Tang, Lingli; Huang, Xiaoming; Sai, Linwei; Zhao, Jijun

2018-05-07

Using a genetic algorithm incorporated with density functional theory, we explore the ground state structures of protonated water clusters H + (H 2 O) n with n = 10-17. Then we re-optimize the isomers at B97-D/aug-cc-pVDZ level of theory. The extra proton connects with a H 2 O molecule to form a H 3 O + ion in all H + (H 2 O) 10-17 clusters. The lowest-energy structures adopt a monocage form at n = 10-16 and core-shell structure at n = 17 based on the MP2/aug-cc-pVTZ//B97-D/aug-cc-pVDZ+ZPE single-point-energy calculation. Using second-order vibrational perturbation theory, we further calculate the infrared spectra with anharmonic correction for the ground state structures of H + (H 2 O) 10-17 clusters at the PBE0/aug-cc-pVDZ level. The anharmonic correction to the spectra is crucial since it reproduces the experimental results quite well. The extra proton weakens the O-H bond strength in the H 3 O + ion since the Wiberg bond order of the O-H bond in the H 3 O + ion is smaller than that in H 2 O molecules, which causes a red shift of the O-H stretching mode in the H 3 O + ion.

Revisit the landscape of protonated water clusters H+(H2O)n with n = 10-17: An ab initio global search

NASA Astrophysics Data System (ADS)

Shi, Ruili; Li, Keyao; Su, Yan; Tang, Lingli; Huang, Xiaoming; Sai, Linwei; Zhao, Jijun

2018-05-01

Using a genetic algorithm incorporated with density functional theory, we explore the ground state structures of protonated water clusters H+(H2O)n with n = 10-17. Then we re-optimize the isomers at B97-D/aug-cc-pVDZ level of theory. The extra proton connects with a H2O molecule to form a H3O+ ion in all H+(H2O)10-17 clusters. The lowest-energy structures adopt a monocage form at n = 10-16 and core-shell structure at n = 17 based on the MP2/aug-cc-pVTZ//B97-D/aug-cc-pVDZ+ZPE single-point-energy calculation. Using second-order vibrational perturbation theory, we further calculate the infrared spectra with anharmonic correction for the ground state structures of H+(H2O)10-17 clusters at the PBE0/aug-cc-pVDZ level. The anharmonic correction to the spectra is crucial since it reproduces the experimental results quite well. The extra proton weakens the O-H bond strength in the H3O+ ion since the Wiberg bond order of the O-H bond in the H3O+ ion is smaller than that in H2O molecules, which causes a red shift of the O-H stretching mode in the H3O+ ion.

Full-dimensional, high-level ab initio potential energy surfaces for H{sub 2}(H{sub 2}O) and H{sub 2}(H{sub 2}O){sub 2} with application to hydrogen clathrate hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Homayoon, Zahra; Conte, Riccardo; Qu, Chen

2015-08-28

New, full-dimensional potential energy surfaces (PESs), obtained using precise least-squares fitting of high-level electronic energy databases, are reported for intrinsic H{sub 2}(H{sub 2}O) two-body and H{sub 2}(H{sub 2}O){sub 2} three-body potentials. The database for H{sub 2}(H{sub 2}O) consists of approximately 44 000 energies at the coupled cluster singles and doubles plus perturbative triples (CCSD(T))-F12a/haQZ (aug-cc-pVQZ for O and cc-pVQZ for H) level of theory, while the database for the three-body interaction consists of more than 36 000 energies at the CCSD(T)-F12a/haTZ (aug-cc-pVTZ for O, cc-pVTZ for H) level of theory. Two precise potentials are based on the invariant-polynomial technique and are comparedmore » to computationally faster ones obtained via “purified” symmetrization. All fits use reduced permutational symmetry appropriate for these non-covalent interactions. These intrinsic potentials are employed together with existing ones for H{sub 2}, H{sub 2}O, and (H{sub 2}O){sub 2}, to obtain full PESs for H{sub 2}(H{sub 2}O) and H{sub 2}(H{sub 2}O){sub 2}. Properties of these full PESs are presented, including a diffusion Monte Carlo calculation of the zero-point energy and wavefunction, and dissociation energy of the H{sub 2}(H{sub 2}O) dimer. These PESs together with an existing one for water clusters are used in a many-body representation of the PES of hydrogen clathrate hydrates, illustrated for H{sub 2}@(H{sub 2}O){sub 20}. An analysis of this hydrate is presented, including the electronic dissociation energy to remove H{sub 2} from the calculated equilibrium structure.« less

A Computational Investigation of the Oxidative Deboronation of BoroGlycine, H2N–CH2–B(OH)2, Using H2O and H2O2

PubMed Central

Larkin, Joseph D.; Markham, George D.; Milkevitch, Matt; Brooks, Bernard R.; Bock, Charles W.

2014-01-01

We report results from a computational investigation of the oxidative deboronation of BoroGlycine, H2N–CH2–B(OH)2, using H2O and H2O2 as the reactive oxygen species (ROS) to yield aminomethanol, H2N–CH2–OH; these results complement our study on the protodeboronation of BoroGlycine to produce methylamine, H2N–CH3 (Larkin et al. J. Phys. Chem. A, 111, 6489–6500, 2007). Second-order Møller-Plesset (MP2) perturbation theory with Dunning-Woon correlation-consistent (cc) basis sets were used for the calculations with comparisons made to results from Density Functional Theory (DFT) at the PBE1PBE/6-311++G(d,p)(cc-pVDZ) levels. The effects of a bulk aqueous environment were also incorporated into the calculations employing PCM and CPCM methodology. Using H2O as the ROS, the reaction H2O + H2N–CH2–B(OH)2 → H2N–CH2–OH + H–B(OH)2 was calculated to be endothermic, the value of ΔH2980 was +12.0 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and +13.7 kcal/mol in PCM aqueous media; the corresponding value for the activation barrier, ΔH‡, was +94.3 kcal/mol relative to the separated reactants in vacuo and +89.9 kcal/mol in PCM aqueous media. In contrast, the reaction H2O2 + H2N–CH2–B(OH)2 → H2N–CH2–OH + B(OH)3 was calculated to be highly exothermic with a ΔH2980 value of −100.9 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and −99.6 kcal/mol in CPCM aqueous media; the highest-energy transition state for the multi-step process associated with this reaction involved the rearrangement of H2N–CH2–B(OH)(OOH) to H2N–CH2–O–B(OH)2 with a ΔH‡ value of +23.2 kcal/mol in vacuo relative to the separated reactants. These computational results for BoroGlycine are in accord with the experimental observations for the deboronation of the FDA approved anti-cancer drug Bortezomib (Velcade™, PS-341) where it was found to be the principle deactivation pathway. (Labutti et al. Chem. Res. Toxicol., 19, 539–546

Communication: H-atom reactivity as a function of temperature in solid parahydrogen: The H + N2O reaction

NASA Astrophysics Data System (ADS)

Mutunga, Fredrick M.; Follett, Shelby E.; Anderson, David T.

2013-10-01

We present low temperature kinetic measurements for the H + N2O association reaction in solid parahydrogen (pH2) at liquid helium temperatures (1-5 K). We synthesize 15N218O doped pH2 solids via rapid vapor deposition onto an optical substrate attached to the cold tip of a liquid helium bath cryostat. We then subject the solids to short duration 193 nm irradiations to generate H-atoms produced as byproducts of the in situ N2O photodissociation, and monitor the subsequent reaction kinetics using rapid scan FTIR. For reactions initiated in solid pH2 at 4.3 K we observe little to no reaction; however, if we then slowly reduce the temperature of the solid we observe an abrupt onset to the H + N2O → cis-HNNO reaction at temperatures below 2.4 K. This abrupt change in the reaction kinetics is fully reversible as the temperature of the solid pH2 is repeatedly cycled. We speculate that the observed non-Arrhenius behavior (negative activation energy) is related to the stability of the pre-reactive complex between the H-atom and 15N218O reagents.

Volume properties and refraction of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids lysine, threonine, and oxyproline (C60(C6H13N2O2)2, C60(C4H8NO3)2, and C60(C5H9NO2)2) at 25°C

NASA Astrophysics Data System (ADS)

Semenov, K. N.; Ivanova, N. M.; Charykov, N. A.; Keskinov, V. A.; Kalacheva, S. S.; Duryagina, N. N.; Garamova, P. V.; Kulenova, N. A.; Nabieva, A.

2017-02-01

Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (H2O and corresponding bisadducts) are calculated for C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems at 25°C. Concentration dependences of the indices of refraction of C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

Step-by-step thermal transformations of a new porous coordination polymer [(H{sub 2}O){sub 5}CuBa(Me{sub 2}mal){sub 2}]{sub n} (Me{sub 2}mal{sup 2-}=dimethylmalonate): Thermal degradation to barium cuprate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zauzolkova, Natalya, E-mail: zauzolkova@igic.ras.ru; Dobrokhotova, Zhanna; Lermontov, Anatoly

The reactions of CuSO{sub 4}{center_dot}5H{sub 2}O, dimethylmalonic acid and Ba(OH){sub 2}{center_dot}H{sub 2}O (Cu: H{sub 2}Me{sub 2}mal: Ba=1: 2: 2) in aqueous and aqueous-ethanol solutions (H{sub 2}O: EtOH=1: 1) resulted in formation of 3D-porous coordination polymers [(H{sub 2}O){sub 3}({mu}-H{sub 2}O){sub 2}CuBa({mu}{sub 3}-Me{sub 2}mal)(Me{sub 2}mal)]{sub n} (1) and [({mu}-H{sub 2}O)CuBa({mu}{sub 3}-Me{sub 2}mal)({mu}{sub 4}-Me{sub 2}mal)]{sub n} (2), respectively. It has been shown that compound 2 was an intermediate in the thermal degradation of compound 1. Thorough studies of solid-state thermolysis of 1 and 2 allowed to detect formation of coordination polymer [CuBa({mu}{sub 4}-Me{sub 2}mal)({mu}{sub 5}-Me{sub 2}mal)]{sub n} (3), structure of which was determinedmore » by X-ray powder diffraction. It has been found that the channels in polymer 3 were accessible for guest molecules (MeOH). Theoretical estimation of methanol diffusion barrier was carried out. Complete solid-phase thermolysis of 1 and 2 leads to a mixture of BaCuO{sub 2}, BaCO{sub 3}, and CuO. Special conditions for obtaining of a crystalline phase of pure cubic BaCuO{sub 2} were determined. - Graphical abstract: Step-by-step transformation of new coordination polymer [(H{sub 2}O){sub 5}CuBa(Me{sub 2}mal){sub 2}]{sub n} to [(H{sub 2}O)CuBa(Me{sub 2}mal){sub 2}]{sub n} and [CuBa(Me{sub 2}mal){sub 2}]{sub n} were performed. Dehydration of initial compound leads to structural changes of 12-membered ring fragment. All compounds have porous structure. The final product of thermal decomposition is crystalline phase of individual cubic BaCuO{sub 2}. Highlights: Black-Right-Pointing-Pointer New 3D-polymers [(H{sub 2}O){sub 5}CuBa(Me{sub 2}mal){sub 2}]{sub n} and [(H{sub 2}O)CuBa(Me{sub 2}mal){sub 2}]{sub n} were synthesized. Black-Right-Pointing-Pointer Thermal analysis showed step-by-step transformations of [(H{sub 2}O){sub 5}CuBa(Me{sub 2}mal){sub 2}]{sub n}. Black

Quenching of I(2P1/2) by NO2, N2O4, and N2O.

PubMed

Kabir, Md Humayun; Azyazov, Valeriy N; Heaven, Michael C

2007-10-11

Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.

Reactions of electronically excited molecular nitrogen with H2 and H2O molecules: theoretical study

NASA Astrophysics Data System (ADS)

Pelevkin, Alexey V.; Sharipov, Alexander S.

2018-05-01

Comprehensive quantum chemical analysis with the usage of the second-order perturbation multireference XMCQDPT2 approach was carried out to study the processes in the   +  H2 and   +  H2O systems. The energetically favorable reaction pathways have been revealed based on the exploration of potential energy surfaces. It has been shown that the reactions   +  H2 and   +  H2O occur with small activation barriers and, primarily, lead to the formation of N2H  +  H and N2H  +  OH products, respectively. Further, the interaction of these species could give rise to the ground state and H2 (or H2O) products, however, the estimations, based on RRKM theory and dynamic reaction coordinate calculations, exhibited that the   +  H2 and   +  H2O reactions lead to the dissociative quenching predominately. Appropriate rate constants for revealed reaction channels have been estimated by using a canonical variational theory and capture approximation. Corresponding three-parameter Arrhenius expressions for the temperature range T  =  300  ‑  3000 K were reported.

Microwave spectroscopy of the seeded binary and ternary clusters CO-(pH{sub 2}){sub 2}, CO-pH{sub 2}-He, CO-HD, and CO-(oD{sub 2}){sub N=1,2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raston, Paul L., E-mail: paul.raston@adelaide.edu.au; Jäger, Wolfgang

We report the Fourier transform microwave spectra of the a-type J = 1-0 transitions of the binary and ternary CO-(pH{sub 2}){sub 2}, CO-pH{sub 2}-He, CO-HD, and CO-(oD{sub 2}){sub N=1,2} clusters. In addition to the normal isotopologue of CO for all clusters, we observed the transitions of the minor isotopologues, {sup 13}C{sup 16}O, {sup 12}C{sup 18}O, and {sup 13}C{sup 18}O, for CO-(pH{sub 2}){sub 2} and CO-pH{sub 2}-He. All transitions lie within 335 MHz of the experimentally or theoretically predicted values. In comparison to previously reported infrared spectra [Moroni et al., J. Chem. Phys. 122, 094314 (2005)], we are able to tentativelymore » determine the vibrational shift for CO-pH{sub 2}-He, in addition to its b-type J = 1-0 transition frequency. The a-type frequency of CO-pH{sub 2}-He is similar to that of CO-He{sub 2} [Surin et al., Phys. Rev. Lett. 101, 233401 (2008)], suggesting that the pH{sub 2} molecule has a strong localizing effect on the He density. Perturbation theory analysis of CO-oD{sub 2} reveals that it is approximately T-shaped, with an anisotropy of the intermolecular potential amounting to ∼9 cm{sup −1}.« less

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils

PubMed Central

Obia, Alfred; Cornelissen, Gerard; Mulder, Jan; Dörsch, Peter

2015-01-01

Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH. PMID:26397367

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

PubMed

Obia, Alfred; Cornelissen, Gerard; Mulder, Jan; Dörsch, Peter

2015-01-01

Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.

Tris(5,6-dimethyl-1H-benzimidazole-κN 3)(pyridine-2,6-dicarboxyl­ato-κ3 O 2,N,O 6)nickel(II)

PubMed Central

Li, Yue-Hua; Li, Feng-Feng; Liu, Xin-Hua; Zhao, Ling-Yan

2012-01-01

The title mononuclear complex, [Ni(C7H3NO4)(C9H10N2)3], shows a central NiII atom which is coordinated by two carboxyl­ate O atoms and the N atom from a pyridine-2,6-dicarboxyl­ate ligand and by three N atoms from different 5,6-dimethyl-1H-­benzimidazole ligands in a distorted octa­hedral geometry. The crystal structure shows intermolecular N—H⋯O hydrogen bonds. PMID:22719301

Hydrogen bonding in microsolvation: photoelectron imaging and theoretical studies on Au(x)(-)-(H2O)(n) and Au(x)(-)-(CH3OH)(n) (x = 1, 2; n = 1, 2) complexes.

PubMed

Wu, Xia; Tan, Kai; Tang, Zichao; Lu, Xin

2014-03-14

We have combined photoelectron velocity-map imaging (VMI) spectroscopy and theoretical calculations to elucidate the geometry and energy properties of Aux(-)(Solv)n clusters with x = 1, 2; n = 1, 2; and Solv = H2O and CH3OH. Besides the blue-shifted vertical electron detachment energies (VDEs) of the complexes Au1,2(-)(Solv)n with the increase of the solvation number (n), we independently probed two distinct Au(-)(CH3OH)2 isomers, which combined with MP2/aug-cc-pVTZ(pp) calculations represent a competition between O···H-O hydrogen bonds (HBs) and Au···H-O nonconventional hydrogen bonds (NHBs). Complementary calculations provide the total binding energies of the low-energy isomers. Moreover, the relationship between the total binding energies and total VDEshift is discussed. We found that the Au1,2(-) anions exhibit halide-analogous behavior in microsolvation. These findings also demonstrate that photoelectron velocity map imaging spectroscopy with the aid of the ab initio calculations is an effective tool for investigating weak-interaction complexes.

Airborne testing and demonstration of a new flight system based on an Aerodyne N2O-CO2-CO-H2O mini-spectrometer

NASA Astrophysics Data System (ADS)

Gvakharia, A.; Kort, E. A.; Smith, M. L.; Conley, S.

2017-12-01

Nitrous oxide (N2O) is a powerful greenhouse gas and ozone depleting substance. With high atmospheric backgrounds and small relative signals, N2O emissions have been challenging to observe and understand on regional scales with traditional instrumentation. Fast-response airborne measurements with high precision and accuracy can potentially bridge this observational gap. Here we present flight assessments of a new flight system based on an Aerodyne mini-spectrometer as well as a Los Gatos N2O/CO analyzer during the Fertilizer Emissions Airborne Study (FEAST). With the Scientific Aviation Mooney aircraft, we conducted test flights for both analyzers where a known calibration gas was sampled throughout the flight (`null' tests). Clear altitude/cabin-pressure dependencies were observed for both analyzers if operated in an "off-the-shelf' manner. For the remainder of test flights and the FEAST campaign we used a new flight system based on an Aerodyne mini-spectrometer with the addition of a custom pressure control/calibration system. Instead of using traditional approaches with spectral-zeros and infrequent in-flight calibrations, we employ a high-flow system with stable flow control to enable high frequency (2 minutes), short duration (15 seconds) sampling of a known calibration gas. This approach, supported by the null test, enables correction for spectral drift caused by a variety of factors while maintaining a 90% duty cycle for 1Hz sampling from an aircraft. Preliminary in-flight precisions are estimated at 0.05 ppb, 0.1 ppm, 1 ppb, and 10 ppm for N2O, CO2, CO, and H2O respectively. We also present a further 40 hours of inter-comparison in flight with a Picarro 2301-f ring-down spectrometer demonstrating consistency between CO2 and H2O measurements and no altitude dependent error.

TES/Aura L2 Water Vapor (H2O) Limb V6 (TL2H2OL)

Atmospheric Science Data Center

2018-03-01

TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access: OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

Structural evolution of the [(CO2)n(H2O)]- cluster anions: quantifying the effect of hydration on the excess charge accommodation motif.

PubMed

Muraoka, Azusa; Inokuchi, Yoshiya; Hammer, Nathan I; Shin, Joong-Won; Johnson, Mark A; Nagata, Takashi

2009-08-06

The [(CO2)n(H2O)]- cluster anions are studied using infrared photodissociation (IPD) spectroscopy in the 2800-3800 cm(-1) range. The observed IPD spectra display a drastic change in the vibrational band features at n = 4, indicating a sharp discontinuity in the structural evolution of the monohydrated cluster anions. The n = 2 and 3 spectra are composed of a series of sharp bands around 3600 cm(-1), which are assignable to the stretching vibrations of H2O bound to C2O4- in a double ionic hydrogen-bonding (DIHB) configuration, as was previously discussed (J. Chem. Phys. 2005, 122, 094303). In the n > or = 4 spectrum, a pair of intense bands additionally appears at approximately 3300 cm(-1). With the aid of ab initio calculations at the MP2/6-31+G* level, the 3300 cm(-1) bands are assigned to the bending overtone and the hydrogen-bonded OH vibration of H2O bound to CO2- via a single O-H...O linkage. Thus, the structures of [(CO2)n(H2O)]- evolve with cluster size such that DIHB to C2O4- is favored in the smaller clusters with n = 2 and 3 whereas CO2- is preferentially stabilized via the formation of a single ionic hydrogen-bonding (SIHB) configuration in the larger clusters with n > or = 4.

Preparation, Characterization, and Structure of Two Layered Molybdenum(VI) Phosphates: KMo(H 2O)O 2PO 4 and NH 4Mo(H 2O)O 2PO 4

NASA Astrophysics Data System (ADS)

Millini, Roberto; Carati, Angela

1995-08-01

New layered Mo(VI) compounds, KMo(H 2O)O 2PO 4 (I) and NH 4Mo(H 2O)O 2PO 4 (II), were synthesized hydrothermally and their structures were determined from single-crystal X-ray analysis. Compounds (I) and (II) are isostructural and crystallize in the monoclinic P2 1/ n space group with a = 12.353(3), b = 8.623(2), c = 5.841(1) Å, β = 102.78(1)°, V = 606.8(2) Å 3, Z = 4, and R = 0.027 ( Rw = 0.030) for compound (I) and a = 12.435(3), b = 8.761(2), c = 6.015(1), β = 103.45(1)°, V = 637.3(2) Å 3, Z = 4, and R = 0.040 ( Rw = 0.041) for compound (II). The structure consists of layers built up of eight- and four-membered rings resulting from the alternation of corner-sharing [MoO 6] octahedra and [PO 4] tetrahedra. The layers stack along the (1¯01) direction by intercalating K and NH 4 ions.