Sample records for uranyl coordination complexes

  1. Electron transfer dissociation of dipositive uranyl and plutonyl coordination complexes.

    PubMed

    Rios, Daniel; Rutkowski, Philip X; Shuh, David K; Bray, Travis H; Gibson, John K; Van Stipdonk, Michael J

    2011-12-01

    Reported here is a comparison of electron transfer dissociation (ETD) and collision-induced dissociation (CID) of solvent-coordinated dipositive uranyl and plutonyl ions generated by electrospray ionization. Fundamental differences between the ETD and CID processes are apparent, as are differences between the intrinsic chemistries of uranyl and plutonyl. Reduction of both charge and oxidation state, which is inherent in ETD activation of [An(VI) O(2) (CH(3) COCH(3) )(4) ](2+) , [An(VI) O(2) (CH(3) CN)(4) ](2) , [U(VI) O(2) (CH(3) COCH(3) )(5) ](2+) and [U(VI) O(2) (CH(3) CN)(5) ](2+) (An?=?U or Pu), is accompanied by ligand loss. Resulting low-coordinate uranyl(V) complexes add O(2) , whereas plutonyl(V) complexes do not. In contrast, CID of the same complexes generates predominantly doubly-charged products through loss of coordinating ligands. Singly-charged CID products of [U(VI) O(2) (CH(3) COCH(3) )(4,5) ](2+) , [U(VI) O(2) (CH(3) CN)(4,5) ](2+) and [Pu(VI) O(2) (CH(3) CN)(4) ](2+) retain the hexavalent metal oxidation state with the addition of hydroxide or acetone enolate anion ligands. However, CID of [Pu(VI) O(2) (CH(3) COCH(3) )(4) ](2+) generates monopositive plutonyl(V) complexes, reflecting relatively more facile reduction of Pu(VI) to Pu(V). PMID:22223415

  2. Roles of acetone and diacetone alcohol in coordination and dissociation reactions of uranyl complexes.

    PubMed

    Rios, Daniel; Schoendorff, George; Van Stipdonk, Michael J; Gordon, Mark S; Windus, Theresa L; Gibson, John K; de Jong, Wibe A

    2012-12-01

    Combined collision-induced dissociation mass spectrometry experiments with DFT and MP2 calculations were employed to elucidate the molecular structures and energetics of dissociation reactions of uranyl species containing acetone and diacetone alcohol ligands. It is shown that solutions containing diacetone alcohol ligands can produce species with more than five oxygen atoms available for coordination. Calculations confirm that complexes with up to four diacetone alcohol ligands can be energetically stable but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Water elimination reactions of diacetone alcohol ligands are shown to have two coordination-dependent reaction channels, through formation of mesityl oxide ligands or formation of alkoxide and protonated mesityl oxide species. The present results provide an explanation for the implausible observation of "[UO(2)(ACO)(6,7,8)](2+)" in and observed water-elimination reactions from purportedly uranyl-acetone complexes (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). PMID:23146003

  3. Uranyl-copper(II) heterometallic oxalate complexes: coordination polymers and frameworks.

    PubMed

    Thury, Pierre; Rivire, Eric

    2013-08-01

    Five oxalate complexes containing both uranyl and copper(II) ions and 2,2?-bipyridine (bipy), 2,2?-bipyrimidine (bipym) or 1,10-phenanthroline (phen) as co-ligands have been synthesized under hydrothermal conditions and their crystal structures were determined. [UO2Cu(C2O4)(NO3)2(bipy)(H2O)] (1) is a molecular complex in which the two cations are connected by the bis-chelating oxalate. A one-dimensional uranyl oxalate ribbon is formed in [UO2Cu(C2O4)2(bipym)(H2O)] (2), with uranyl ions bound to two chelating anions and to a third, monodentate oxalate which holds the decorating [Cu(bipym)(H2O)]2+ groups. Complex [(UO2)2Cu2(C2O4)2(bipym)3(OH)2]2NO3 (3) is a two-dimensional assembly in which uranyl oxalate chains are linked to one another by [Cu2(bipym)3]4+ dinuclear units through bridging hydroxide ions. Finally, [UO2Cu(C2O4)2(bipy)] (4) and [UO2Cu(C2O4)2(phen)] (5) display identical three-dimensional arrangements containing uranyl oxalate sheets connected to one another by copper oxalate dinuclear units. The magnetic properties of compounds 2 and 4 have been investigated. Weak inter-chain antiferromagnetic interactions between copper(II) atoms are present in 2, while 4 displays strong oxalate-mediated antiferromagnetic exchange (J = -335 cm(-1)). These complexes are the first uranyl-d block metal oxalate complexes to be reported. PMID:23760346

  4. Thermochromic properties of low-melting ionic uranyl isothiocyanate complexes.

    PubMed

    Aoyagi, Noboru; Shimojo, Kojiro; Brooks, Neil R; Nagaishi, Ryuji; Naganawa, Hirochika; Van Hecke, Kristof; Van Meervelt, Luc; Binnemans, Koen; Kimura, Takaumi

    2011-04-21

    Temperature-dependent yellow-to-red colour changes of uranyl thiocyanate complexes with 1-alkyl-3-methylimidazolium cations have been studied by different spectroscopic methods and this phenomenon is attributed to changes in the local environment of the uranyl ion, including the coordination number, as well as to cation-anion interactions. PMID:21399798

  5. Alkali-metal ion coordination in uranyl(VI) poly-peroxide complexes in solution. Part 1: the Li?, Na? and K?--peroxide-hydroxide systems.

    PubMed

    Zanonato, Pier Luigi; Di Bernardo, Plinio; Vallet, Valerie; Szab, Zoltn; Grenthe, Ingmar

    2015-01-28

    The alkali metal ions Li(+), Na(+) and K(+) have a profound influence on the stoichiometry of the complexes formed in uranyl(VI)-peroxide-hydroxide systems, presumably as a result of a templating effect, resulting in the formation of two complexes, M[(UO2)(O2)(OH)]2(-) where the uranyl units are linked by one peroxide bridge, ?-?(2)-?(2), with the second peroxide coordinated "end-on", ?(2), to one of the uranyl groups, and M[(UO2)(O2)(OH)]4(3-), with a four-membered ring of uranyl ions linked by ?-?(2)-?(2) peroxide bridges. The stoichiometry and equilibrium constants for the reactions: M(+) + 2UO2(2+) + 2HO2(-) + 2H2O ? M[(UO2)(O2)(OH)]2(-) + 4H(+) (1) and M(+) + 4UO2(2+) + 4HO2(-) + 4H2O ? M[(UO2)(O2)(OH)]4(3-) + 8H(+) (2) have been measured at 25 C in 0.10 M (tetramethyl ammonium/M(+))NO3 ionic media using reaction calorimetry. Both reactions are strongly enthalpy driven with large negative entropies of reaction; the observation that ?H(2) ? 2?H(1) suggests that the enthalpy of reaction is approximately the same when peroxide is added in bridging and "end-on" positions. The thermodynamic driving force in the reactions is the formation of strong peroxide bridges and the role of M(+) cations is to provide a pathway with a low activation barrier between the reactants and in this way "guide" them to form peroxide bridged complexes; they play a similar role as in the synthesis of crown-ethers. Quantum chemical (QC) methods were used to determine the structure of the complexes, and to demonstrate how the size of the M(+)-ions affects their coordination geometry. There are several isomers of Na[(UO2)(O2)(OH)]2(-) and QC energy calculations show that the ones with a peroxide bridge are substantially more stable than the ones with hydroxide bridges. There are isomers with different coordination sites for Na(+) and the one with coordination to the peroxide bridge and two uranyl oxygen atoms is the most stable one. PMID:25286234

  6. Uranyl Sequestration: Synthesis and Structural Characterization of Uranyl Complexes with a Tetradentate Methylterephthalamide Ligand

    SciTech Connect

    Ni, Chengbao; Shuh, David; Raymond, Kenneth

    2011-03-07

    Uranyl complexes of a bis(methylterephthalamide) ligand (LH{sub 4}) have been synthesized and characterized by X-ray crystallography. The structure is an unexpected [Me{sub 4}N]{sub 8}[L(UO{sub 2})]{sub 4} tetramer, formed via coordination of the two MeTAM units of L to two uranyl moieties. Addition of KOH to the tetramer gave the corresponding monomeric uranyl methoxide species [Me{sub 4}N]K{sub 2}[LUO{sub 2}(OMe)].

  7. Uranyl-halide complexation in N,N-dimethylformamide: halide coordination trend manifests hardness of [UO2]2+.

    PubMed

    Takao, Koichiro; Takao, Shinobu; Ikeda, Yasuhisa; Bernhard, Gert; Hennig, Christoph

    2013-09-28

    Complexation of [UO2](2+) with Cl(-), Br(-), and I(-) in N,N-dimethylformamide (DMF) was studied by UV-vis absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) to clearly differentiate halide coordination strengths to [UO2](2+). In the Cl(-) system, it was clarified that the Cl(-) coordination to [UO2](2+) in DMF proceeds almost quantitatively. The coordination number of Cl(-) almost quantitatively increases up to 4, i.e., the limiting complex is [UO2Cl4](2-). Logarithmic gross stability constants of [UO2Cl(x)](2-x) (x = 1-4) were evaluated as log ?1 = 9.67, log ?2 = 15.49, log ?3 = 19.89, and log ?4 = 24.63 from UV-vis titration experiments. The EXAFS results well demonstrated not only the Cl(-) coordination, but also the DMF solvation in the equatorial plane of [UO2](2+). The interaction of Br(-) and I(-) with [UO2](2+) in DMF was also investigated. As a result, the Br(-) coordination to [UO2](2+) stops at the second step, i.e., only [UO2Br](+) and UO2Br2 were observed. The molecular structure of each occurring species was confirmed by EXAFS. The evaluated log ?x values of [UO2Br(x)](2-x) (x = 1, 2) are 3.45 and 5.42, respectively. The much smaller log ?x than those of [UO2Cl(x)](2-x) indicates that Br(-) is a much weaker ligand to [UO2](2+) than Cl(-). The EXAFS experiments revealed that the presence of I(-) in the test solution does not modify any coordination structure around [UO2](2+). Thus, I(-) does not form any stable [UO2](2+) complexes in DMF. Consequently, the stability of the halido complexes of [UO2](2+) in DMF is exactly in line with the hardness order of halides. PMID:23877093

  8. Water versus acetonitrile coordination to uranyl. Effect of chloride ligands.

    PubMed

    Bhl, Michael; Sieffert, Nicolas; Chaumont, Alain; Wipff, Georges

    2012-02-01

    Optimizations at the BLYP and B3LYP levels are reported for the mixed uranyl chloro/water/acetonitrile complexes [UO(2)Cl(n)(H(2)O)(x)(MeCN)(5-n-x)](2-n) (n = 1-3) and [UO(2)Cl(n)(H(2)O)(x)(MeCN)(4-n-x)](2-n) (n = 2-4), in both the gas phase and a polarizable continuum modeling acetonitrile. Car-Parrinello molecular dynamics (CPMD) simulations have been performed for [UO(2)Cl(2)(H(2)O)(MeCN)(2)] in the gas phase and in a periodic box of liquid acetonitrile. According to population analyses and dipole moments evaluated from maximally localized Wannier function centers, uranium is less Lewis acidic in the neutral UO(2)Cl(2) than in the UO(2)(2+) moiety. In the gas phase the latter binds acetonitrile ligands more strongly than water, whereas in acetonitrile solution, the trend is reversed due to cooperative polarization effects. In the polarizable continuum the chloro complexes have a slight energetic preference for water over acetonitrile ligands, but several mixed complexes are so close in free energy ?G that they should exist in equilibrium, in accord with previous interpretations of EXAFS data in solution. The binding strengths of the fifth neutral ligands decrease with increasing chloride content, to the extent that the trichlorides should be formulated as four-coordinate [UO(2)Cl(3)L](-) (L = H(2)O, MeCN). Limitations to their accuracy notwithstanding, density functional calculations can offer insights into the speciation of a complex uranyl system in solution, a key feature in the context of nuclear waste partitioning by complexant molecules. PMID:22233256

  9. Luminescence spectra of the uranyl ion in two geometrically similar coordination environments. Uranyl nitrate hexahydrate and di-. mu. -aquo-bis(dioxobis(nitrato)uranium(VI)) diimidazole

    Microsoft Academic Search

    Harry G. Brittain; Dale L. Perry

    1980-01-01

    The luminescence spectra of the uranyl ion have been obtained at room and liquid-nitrogen temperatures in the crystal hosts of uranyl nitrate hexahydrate (UNH) and di-..mu..-aquo-bis(dioxobis(nitrato)uranium(VI)) diimidazole (UNI). In both coordination spheres, the uranyl ion lies at the center of similar, distorted coordination hexagons consisting of two bidentate nitrate groups and two water molecules; the only difference in the coordination

  10. A Spectrophotometric Study on Uranyl Nitrate Complexation to 150?C

    Microsoft Academic Search

    O. M. Suleimenov; T. M. Seward; J. K. Hovey

    2007-01-01

    The formation constant of the mononitratouranyl complex was studied spectrophotometrically at temperatures of 25, 40, 55,\\u000a 70, 100 and 150?C (298, 313, 328, 343, 373 and 423 K). The uranyl ion concentration was fixed at approximately 0.008 mol?kg?1 and the ligand concentration was varied from 0.05 to 3.14 mol?kg?1. The uranyl nitrate complex, UO2NO3+, is weak at 298 K but

  11. Bonding and charge transfer in nitrogen-donor uranyl complexes: insights from NEXAFS spectra.

    PubMed

    Pemmaraju, C D; Copping, Roy; Wang, Shuao; Janousch, Markus; Teat, Simon J; Tyliszcak, Tolek; Canning, Andrew; Shuh, David K; Prendergast, David

    2014-11-01

    We investigate the electronic structure of three newly synthesized nitrogen-donor uranyl complexes [(UO2)(H2bbp)Cl2], [(UO)2(Hbbp)(Py)Cl], and [(UO2)(bbp)(Py)2] using a combination of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments and simulations. The complexes studied feature derivatives of the tunable tridentate N-donor ligand 2,6-bis(2-benzimidazyl)pyridine (bbp) and exhibit discrete chemical differences in uranyl coordination. The sensitivity of the N K-edge X-ray absorption spectrum to local bonding and charge transfer is exploited to systematically investigate the evolution of structural as well as electronic properties across the three complexes. A thorough interpretation of the measured experimental spectra is achieved via ab initio NEXAFS simulations based on the eXcited electron and Core-Hole (XCH) approach and enables the assignment of spectral features to electronic transitions on specific absorbing sites. We find that ligand-uranyl bonding leads to a signature blue shift in the N K-edge absorption onset, resulting from charge displacement toward the uranyl, while changes in the equatorial coordination shell of the uranyl lead to more subtle modulations in the spectral features. Theoretical simulations show that the flexible local chemistry at the nonbinding imidazole-N sites of the bbp ligand is also reflected in the NEXAFS spectra and highlights potential synthesis strategies to improve selectivity. In particular, we find that interactions of the bbp ligand with solvent molecules can lead to changes in ligand-uranyl binding geometry while also modulating the K-edge absorption. Our results suggest that NEXAFS spectroscopy combined with first-principles interpretation can offer insights into the coordination chemistry of analogous functionalized conjugated ligands. PMID:25330350

  12. The catalytic role of uranyl in formation of polycatechol complexes

    PubMed Central

    2011-01-01

    To better understand the association of contaminant uranium with natural organic matter (NOM) and the fate of uranium in ground water, spectroscopic studies of uranium complexation with catechol were conducted. Catechol provides a model for ubiquitous functional groups present in NOM. Liquid samples were analyzed using Raman, FTIR, and UV-Vis spectroscopy. Catechol was found to polymerize in presence of uranyl ions. Polymerization in presence of uranyl was compared to reactions in the presence of molybdate, another oxyion, and self polymerization of catechol at high pH. The effect of time and dissolved oxygen were also studied. It was found that oxygen was required for self-polymerization at elevated pH. The potential formation of phenoxy radicals as well as quinones was monitored. The benzene ring was found to be intact after polymerization. No evidence for formation of ether bonds was found, suggesting polymerization was due to formation of C-C bonds between catechol ligands. Uranyl was found to form outer sphere complexes with catechol at initial stages but over time (six months) polycatechol complexes were formed and precipitated from solution (forming humic-like material) while uranyl ions remained in solution. Our studies show that uranyl acts as a catalyst in catechol-polymerization. PMID:21396112

  13. Gas phase uranyl activation: formation of a uranium nitrosyl complex from uranyl azide.

    PubMed

    Gong, Yu; de Jong, Wibe A; Gibson, John K

    2015-05-13

    Activation of the oxo bond of uranyl, UO2(2+), was achieved by collision induced dissociation (CID) of UO2(N3)Cl2(-) in a quadrupole ion trap mass spectrometer. The gas phase complex UO2(N3)Cl2(-) was produced by electrospray ionization of solutions of UO2Cl2 and NaN3. CID of UO2(N3)Cl2(-) resulted in the loss of N2 to form UO(NO)Cl2(-), in which the "inert" uranyl oxo bond has been activated. Formation of UO2Cl2(-) via N3 loss was also observed. Density functional theory computations predict that the UO(NO)Cl2(-) complex has nonplanar Cs symmetry and a singlet ground state. Analysis of the bonding of the UO(NO)Cl2(-) complex shows that the side-on bonded NO moiety can be considered as NO(3-), suggesting a formal oxidation state of U(VI). Activation of the uranyl oxo bond in UO2(N3)Cl2(-) to form UO(NO)Cl2(-) and N2 was computed to be endothermic by 169 kJ/mol, which is energetically more favorable than formation of NUOCl2(-) and UO2Cl2(-). The observation of UO2Cl2(-) during CID is most likely due to the absence of an energy barrier for neutral ligand loss. PMID:25906363

  14. Spectroscopic study on uranyl carboxylate complexes formed at the surface layer of Sulfolobus acidocaldarius.

    PubMed

    Reitz, Thomas; Rossberg, Andre; Barkleit, Astrid; Steudtner, Robin; Selenska-Pobell, Sonja; Merroun, Mohamed L

    2015-02-14

    The complexation of U(vi) at the proteinaceous surface layer (S-layer) of the archaeal strain Sulfolobus acidocaldarius was investigated over a pH range from pH 1.5 to 6 at the molecular scale using time-resolved laser-induced fluorescence spectroscopy (TRLFS) and U L(III)-edge extended X-ray absorption fine structure (EXAFS). The S-layer, which represents the interface between the cell and its environment, is very stable against high temperatures, proteases, and detergents. This allowed the isolation and purification of S-layer ghosts (= empty cells) that maintain the size and shape of the cells. In contrast to many other microbial cell envelope compounds the studied S-layer is not phosphorylated, enabling the investigation of uranyl carboxylate complexes formed at microbial surfaces. The latter are usually masked by preferentially formed uranyl phosphate complexes. We demonstrated that at highly acidic conditions (pH 1.5 to 3) no uranium was bound by the S-layer. In contrast to that, at moderate acidic pH conditions (pH 4.5 and 6) a complexation of U(vi) at the S-layer via deprotonated carboxylic groups was stimulated. Titration studies revealed dissociation constants for the carboxylic groups of glutamic and aspartic acid residues of pK(a) = 4.78 and 6.31. The uranyl carboxylate complexes formed at the S-layer did not show luminescence properties at room temperature, but only under cryogenic conditions. The obtained luminescence maxima are similar to those of uranyl acetate. EXAFS spectroscopy demonstrated that U(vi) in these complexes is mainly coordinated to carboxylate groups in a bidentate binding mode. The elucidation of the molecular structure of these complexes was facilitated by the absence of phosphate groups in the studied S-layer protein. PMID:25387060

  15. Predicting stability constants for uranyl complexes using density functional theory.

    PubMed

    Vukovic, Sinisa; Hay, Benjamin P; Bryantsev, Vyacheslav S

    2015-04-20

    The ability to predict the equilibrium constants for the formation of 1:1 uranyl/ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We use density functional theory (B3LYP) and the integral equation formalism polarizable continuum model (IEF-PCM) to compute aqueous stability constants for UO2(2+) complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root-mean-square deviation from experiment <1.0 for log K1 values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono- and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelating capability to uranyl. PMID:25835578

  16. Intrinsic Hydration of Uranyl-Hydroxide, -Nitrate and -Acetate Complexes

    SciTech Connect

    Winnie Chien; Dorothy Hanna; Victor Anbalagan; Garold Gresham; Gary Groenewold; Michael Van Stipdonk

    2004-06-01

    The intrinsic hydration of three monopositive uranyl-anion complexes (UO2A)+ (where A = acetate, nitrate, or hydroxide) was investigated using ion-trap mass spectrometry (IT-MS). The relative rates for the formation of the monohydrates [(UO2A)(H2O)]+, with respect to the anion, followed the trend: Acetate = nitrate >> hydroxide. This finding was rationalized in terms of the donation of electron density by the strongly basic OH- to the uranyl metal center, thereby reducing the Lewis acidity of U and its propensity to react with incoming nucleophiles, viz., H2O. An alternative explanation is that the more complex acetate and nitrate anions provide increased degrees of freedom that could accommodate excess energy from the hydration reaction. The monohydrates also reacted with water, forming dihydrates and then trihydrates. The rates for formation of the nitrate and acetate dihydrates [(UO2A)(H2O)2]+ were very similar to the rates for formation of the monohydrates; the presence of the first H2O ligand had no influence on the addition of the second. In contrast, formation of the [(UO2OH)(H2O)2]+ was nearly three times faster than the formation of the monohydrate.

  17. Complex Nanoscale Cage Clusters Built from Uranyl Polyhedra and Phosphate Tetrahedra

    SciTech Connect

    Unruh, Daniel K. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Ling, Jie [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Qiu, Jie [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Pressprich, Laura [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Baranay, Melissa [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Ward, Matthew [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Burns, Peter C. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences

    2011-06-20

    Five cage clusters that self-assemble in alkaline aqueous solution have been isolated and characterized. Each is built from uranyl hexagonal bipyramids with two or three equatorial edges occupied by peroxide, and three also contain phosphate tetrahedra. These clusters contain 30 uranyl polyhedra; 30 uranyl polyhedra and six pyrophosphate groups; 30 uranyl polyhedra, 12 pyrophosphate groups, and one phosphate tetrahedron; 42 uranyl polyhedra; and 40 uranyl polyhedra and three pyrophosphate groups. These clusters present complex topologies as well as a range of compositions, sizes, and charges. Two adopt fullerene topologies, and the others contain combinations of topological squares, pentagons, and hexagons. An analysis of possible topologies further indicates that higher-symmetry topologies are favored.

  18. Evaluation of the stability of uranyl peroxo-carbonato complex ions in carbonate media at different temperatures.

    PubMed

    Kim, Kwang-Wook; Lee, Keun-Young; Chung, Dong-Yong; Lee, Eil-Hee; Moon, Jei-Kwon; Shin, Dong-Woo

    2012-09-30

    This work studied the stability of peroxide in uranyl peroxo carbonato complex ions in a carbonate solution with hydrogen peroxide using absorption and Raman spectroscopies, and evaluated the temperature dependence of the decomposition characteristics of uranyl peroxo carbonato complex ions in the solution. The uranyl peroxo carbonato complex ions self-decomposed more rapidly into uranyl tris-carbonato complex ions in higher temperature carbonate solutions. The concentration of peroxide in the solution without free hydrogen peroxide represents the concentration of uranyl peroxo carbonato complex ions in a mixture of uranyl peroxo carbonato complex and uranyl tris-carbonato complex ions. The self-decomposition of the uranyl peroxo carbonato complex ions was a first order reaction, and its activation energy was evaluated to be 7.14410(3) J mol(-1). The precipitation of sodium uranium oxide hydroxide occurred when the amount of uranyl tris-carbonato complex ions generated from the decomposition of the uranyl peroxo carbonato complex ions exceeded the solubility of uranyl tris-carbonato ions in the solution at the solution temperature. PMID:22831997

  19. Complexation of the Carbonate, Nitrate, and Acetate Anions with the Uranyl Dication: Density Functional Studies with Relativistic Effective Core Potentials

    SciTech Connect

    De Jong, Wibe A.; Apra, Edoardo; Windus, Theresa L.; Nichols, Jeffrey A.; Harrison, Robert J.; Gutowski, Keith E.; Dixon, David A.

    2005-12-22

    The structures and vibrational frequencies of uranyl carbonates, [UO?(CO?)n](?- ??) and [(UO?)?(CO?)?]??, uranyl nitrates, [UO? (NO?)n](?-?), and uranyl acetates, [UO?(CH?COO)n](?-?) (n = 1,2,3) have been calculated by using local density functional theory (LDFT). Only bidentate ligand coordination modes to the uranyl dication have been modeled. The calculated structures and frequencies are compared to available experimental data, including IR, Raman, X-ray diffraction, and EXAFS solution and crystal structure data. The energetics of ligand binding have been calculated using the B3LYP hybrid functional. In general, the structural and vibrational results at the LDFT level are in good agreement with experimental results and provide realistic pictures of solution phase and solid state behavior. For the [UO? (CO?)?]?? anion, calculations suggest that complexity in the CO??? stretching signature upon complexation is due to the formation of C=O and C-O domains, the latter of which can split by as much as 300 cm??. Assessment of the binding energies indicate that the [UO? (CO?)?]?? anion is more stable than the [UO?(CO?)?]?? anion due to the accumulation of excess charge, whereas the tri-ligand species are the most stable in the nitrate and acetate anions.

  20. X-ray absorption spectroscopy identifies calcium-uranyl-carbonate complexes at environmental concentrations.

    SciTech Connect

    Kelly, S. D.; Kemner, K. M.; Brooks, S. C.; Biosciences Division; ORNL

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO{sub 2}-CO{sub 3} complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO{sub 2}-CO{sub 3} complex. Such a complex might exist even at high calcium concentrations, as some UO{sub 2}-CO{sub 3} complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 {micro}M uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO{sub 2}-CO{sub 3} complex to approximately 0.6 and enables spectroscopic identification of the Na-UO{sub 2}-CO{sub 3} complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  1. X-ray Absorption Spectroscopy Identifies Calcium-Uranyl-Carbonate Complexes at Environmental Concentrations

    SciTech Connect

    Kelly, Shelly D [Argonne National Laboratory (ANL); Kemner, Kenneth M [Argonne National Laboratory (ANL); Brooks, Scott C [ORNL

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO2-CO3 complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO2-CO3 complex. Such a complex might exist even at high calcium concentrations, as some UO2-CO3 complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 lM uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO2-CO3 complex to approximately 0.6 and enables spectroscopic identification of the Na-UO2-CO3 complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  2. Uranyl Sensitization of Samarium(III) Luminescence in a Two-Dimensional Coordination Polymer

    SciTech Connect

    Knope, Karah E. [George Washington Univ., Washington, DC (United States); de Lill, Daniel T. [Univ. of Nevada, Reno, NV (United States); Rowland, Clare E. [George Washington Univ., Washington, DC (United States); Cantos, Paula M. [George Washington Univ., Washington, DC (United States); de Bettencourt-Dias, Ana [Univ. of Nevada, Reno, NV (United States); Cahill, Christopher L. [George Washington Univ., Washington, DC (United States)

    2012-01-02

    Heterometallic carboxyphosphonates UO?2+/Ln3+ have been prepared from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H?PPA). Compound 1, (UO?)?(PPA)(HPPA)?Sm(H?O)2H?O (1) adopts a two-dimensional structure in which the UO?2+ metal ions bind exclusively to the phosphonate moiety, whereas the Ln3+ ions are coordinated by both phosphonate and carboxylate functionalities. Luminescence studies of 1 show very bright visible and near-IR samarium(III)-centered emission upon direct excitation of the uranyl moiety. The Sm3+ emissive state exhibits a double-exponential decay with lifetimes of 67.2 6.5 and 9.0 1.3 ?s as measured at 594 nm, after excitation at both 365 and 420 nm. No emission is observed in the region typical of the uranyl cation, indicating that all energy is either transferred to the Sm3+ center or lost to nonradiative processes. Herein we report the synthesis, crystal structure, and luminescent behavior of 1, as well as those of the isostructural terbium, erbium, and ytterbium analogues.

  3. The Influence of Linker Geometry on Uranyl Complexation by Rigidly-Linked Bis(3-hydroxy-N-methyl-pyridin-2-one)

    SciTech Connect

    Szigethy, Geza; Raymond, Kenneth

    2010-04-22

    A series of bis(3-hydroxy-N-methyl-pyridin-2-one) ligands was synthesized, and their respective uranyl complexes were characterized by single crystal X-ray diffraction analyses. These structures were inspected for high-energy conformations and evaluated using a series of metrics to measure co-planarity of chelating moieties with each other and the uranyl coordination plane, as well as to measure coordinative crowding about the uranyl dication. Both very short (ethyl, 3,4-thiophene and o-phenylene) and very long ({alpha},{alpha}{prime}-m-xylene and 1,8-fluorene) linkers provide optimal ligand geometries about the uranyl cation, resulting in planar, unstrained molecular arrangements. The planarity of the rigid linkers also suggests there is a degree of pre-organization for a planar coordination mode that is ideal for uranyl-selective ligand design. Comparison of intramolecular N{sub amide}-O{sub phenolate} distances and {sup 1}H NMR chemical shifts of amide protons supports earlier results that short linkers provide the optimal geometry for intramolecular hydrogen bonding.

  4. Metal-exchange reactions between the uranyl-18-crown-6 complex and Na/sup +/ ion in propylene carbonate

    SciTech Connect

    Fux, P.; Lagrange, J.; Lagrange, P.

    1988-01-13

    An intermediate complex, UO/sub 2/L/sup 2+/, is proposed to help explain the metal-exchange reaction between the uranyl-18-crown-6 and Na/sup +/ ion in propylene carbonate. This intermediate is thought to be an outer-sphere complex where the coordinating center UO/sub 2//sup 2+/ is partially enclosed in the ligand cavity and where the Na/sup +/ ion is completely desolvated. A total reaction scheme is proposed, and mathematical treatment of the data is presented. 20 refs., 2 figs.

  5. Designing the Ideal Uranyl Ligand: a Sterically-Induced Speciation Change in Complexes with Thiophene-Bridged Bis(3-hydroxy-N-methylpyridin-2-one)

    SciTech Connect

    Szigethy, Geza; Raymond, Kenneth N.

    2009-09-11

    Structural characterization of a mononuclear uranyl complex with a tetradentate, thiophene-linked bis(3-hydroxy-N-methylpyridin-2-one) ligand reveals the most planar coordination geometry yet observed with this ligand class. The introduction of ethylsulfanyl groups onto the thiophene linker disrupts this planar, conjugated ligand arrangement, resulting in the formation of dimeric (UO{sub 2}){sub 2}L{sub 2} species in which each ligand spans two uranyl centers. Relative energy calculations reveal that this tendency toward dimer formation is the result of steric interference between ethylsulfanyl substituents and linking amides.

  6. Designing the ideal uranyl ligand: a sterically induced speciation change in complexes with thiophene-bridged bis(3-hydroxy-n-methylpyridin-2-one).

    PubMed

    Szigethy, Gza; Raymond, Kenneth N

    2009-12-21

    Structural characterization of a mononuclear uranyl complex with a tetradentate, thiophene-linked bis(3-hydroxy-N-methylpyridin-2-one) ligand reveals the most planar coordination geometry yet observed with this ligand class. The introduction of ethylsulfanyl groups onto the thiophene linker disrupts this planar, conjugated ligand arrangement, resulting in the formation of dimeric (UO(2))(2)L(2) species in which each ligand spans two uranyl centers. Relative energy calculations reveal that this tendency toward dimer formation is the result of steric interference between ethylsulfanyl substitutents and linking amides. PMID:19928845

  7. Uranyl and uranyl-3d block cation complexes with 1,3-adamantanedicarboxylate: crystal structures, luminescence, and magnetic properties.

    PubMed

    Thury, Pierre; Rivire, Eric; Harrowfield, Jack

    2015-03-16

    The reaction of 1,3-adamantanedicarboxylic acid (LH2) with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Co(2+), Ni(2+), or Cu(2+)) gives a series of nine complexes displaying a wide range of architectures. While [UO2(L)(H2O)]1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]1.5H2O (3), which includes dimethylammonium counterions generated in situ, is a three-dimensional (3D) framework, and [UO2(L)(NMP)] (4) (NMP = N-methyl-2-pyrrolidone) is a braid-shaped 1D polymer. When 3d block metal ions are present and bound to 2,2'-bipyridine (bipy) coligands, their role is reduced to that of decorating species attached to uranyl-containing 1D polymers, as in [UO2M(L)2(bipy)2]0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]3H2O (7), in which a two-dimensional (2D) assembly is built from tetranuclear uranyl-containing building units. In contrast, the heterometallic 3D framework [UO2Cu(L)2] (8) can be isolated in the absence of bipy. The emission spectra measured in the solid state display the usual uranyl vibronic fine structure, with various degrees of resolution and quenching, except for that of complex 7, which shows emission from the nickel(II) centers. The magnetic properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the presence of zero-field splitting effects in 6 and weak antiferromagnetic interactions in 9. PMID:25710676

  8. Uranyl nitrate complex extraction into TBP/dodecane organic solutions: a molecular dynamics study.

    PubMed

    Ye, Xianggui; Cui, Shengting; de Almeida, Valmor F; Hay, Benjamin P; Khomami, Bamin

    2010-12-21

    Liquid-liquid extraction of uranyl is studied by conducting atomistic molecular dynamics simulation using quantum chemistry calibrated force fields via restrained electrostatic potential fitting of atomic forces. The simulations depict the migration of uranyl nitrate complexes from the aqueous-organic interface into the tri-n-butyl phosphate (TBP)/dodecane organic phase, in the form of UO(2)(NO(3))(2)H(2)O2TBP and UO(2)(NO(3))(2)3TBP. The migration process is characterized by the gradual breaking of all the hydrogen bonds between the complex and the water molecules at the interface. Moreover, our simulation results suggest that the experimentally observed complex UO(2)(NO(3))(2)2TBP is formed after the migration of the aforementioned complexes into the organic phase by means of a reorganization of the nitrate binding mode from mono to bidentate which removes the excess oxygen atoms bound to uranyl. PMID:20967313

  9. Ternary uranyl-citrate-surface complex formation on geothite gibbsite, and phylosilicate minerals

    SciTech Connect

    Redden, G.D.; Li, J.; Leckie, J.O. [Stanford Univ., CA (United States)

    1996-10-01

    Liquid radioactive wastes that contain transuranic elements are often associated with complexing organic co-contaminants. Prediction of radionuclide transpose in contaminated groundwater will require accounting for the effect of both organic co-solutes and naturally occurring compounds. A study has been conducted on the adsorption of uranyl ion (UO{sub 2}{sup 2+}) on goethite, gibbsite, and phylosilicate minerals in the presence of varying concentrations of citric acid. Adsorption of either solute separately as functions of pH yield sorption curves that are generally typical for cations and anions with differences in features reflecting differences in properties of the surface functional groups. At equimolar concentrations of uranyl and citrate little effect on the sorption of either solute is observed. However, at higher citrate concentrations uranyl sorption dramatically increases with nearly complete uranyl sorption even at relatively low pH values. A stable bridging structure involving uranyl and citrate is implied. These results have significant relevance to radionuclide transport modeling where soluble chelators may increase rather than decrease sorption of uranyl.

  10. Structural insights into the binding of uranyl with human serum protein apotransferrin structure and spectra of protein-uranyl interactions.

    PubMed

    Benavides-Garcia, Maria G; Balasubramanian, Krishnan

    2009-09-01

    Ab initio quantum mechanical computational studies for the structure and IR spectra of the uranyl complex with human serum apotransferrin (TF) protein are carried out to model uranyl intake into the human cell through endocytosis and formation of a coordination complex with the protein binding sites. The computed IR spectra and structure of the uranyl-protein complex facilitate interpretation of the observed spectra and confirm the primary binding sites of the transferrin protein with the uranyl ion. Our computed equilibrium geometry and the IR spectra of the uranyl-TF complex reveal that uranyl ion is bound to two tyrosines, one aspartate group, and one carbonate ion. Our IR spectra indicate that histidine is not involved in binding to uranyl with transferrin protein. Our computations reveal a short, strong hydrogen bond, which could play an important role in the stabilization and formation of the uranyl-TF complex. Computed Laplacian charge plots indicate high chemical reactivity on this complex as both an electrophile and a nucleophile, facilitating binding to different receptors and thus entry into a number of target organs and the blood-brain barrier. The Mulliken charge density plots and the three-dimensional charge density plots suggest a donor-acceptor mechanism in the complex formation. PMID:19678663

  11. Toward equatorial planarity about uranyl: synthesis and structure of tridentate nitrogen-donor {UO2}2+ complexes.

    PubMed

    Copping, Roy; Jeon, Byoungseon; Pemmaraju, C Das; Wang, Shuao; Teat, Simon J; Janousch, Markus; Tyliszczak, Tolek; Canning, Andrew; Grnbech-Jensen, Niels; Prendergast, David; Shuh, David K

    2014-03-01

    The reaction of UO2Cl23THF with the tridentate nitrogen donor ligand 2,6-bis(2-benzimidazolyl)pyridine (H2BBP) in pyridine leads to the formation of three different complexes: [(UO2)(H2BBP)Cl2] (1), [(UO)2(HBBP)(Py)Cl] (2), and [(UO2)(BBP)(Py)2] (3) after successive deprotonation of H2BBP with a strong base. Crystallographic determination of 1-3 reveals that increased charge through ligand deprotonation and displacement of chloride leads to equatorial planarity about uranyl as well as a more compact overall coordination geometry. Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectra of 1-3 at the U-4d edges have been recorded using a soft X-ray Scanning Transmission X-ray Microscope (STXM) and reveal the uranium 4d5/2 and 4d3/2 transitions at energies associated with uranium in the hexavalent oxidation state. First-principles Density Functional Theory (DFT) electronic structure calculations for the complexes have been performed to determine and validate the coordination characteristics, which correspond well to the experimental results. PMID:24528285

  12. Ligand Exchange and Nature of Luminescence Centers in the Crystals of Uranyl Nitrates and Perchlorates

    Microsoft Academic Search

    A. I. Komyak; A. A. Zazhogin; A. P. Zazhogin; D. S. Umreiko

    2002-01-01

    We obtained complexes of uranyl nitrates and uranyl perchlorates with neutral ligands in crystalline and amorphous states and also with variable composition (as regards both water and the quantity of acid ligands entering into the first coordination sphere of UO22+). We studied their luminescence spectra at T = 77 K. Correlation between the frequencies of electronic and vibronic transitions and

  13. Gas-phase coordination complexes of dipositive plutonyl, PuO2(2+): chemical diversity across the actinyl series.

    PubMed

    Rios, Daniel; Rutkowski, Philip X; Van Stipdonk, Michael J; Gibson, John K

    2011-06-01

    We report the first transmission of solvent-coordinated dipositive plutonyl ion, Pu(VI)O(2)(2+), from solution to the gas phase by electrospray ionization (ESI) of plutonyl solutions in water/acetone and water/acetonitrile. ESI of plutonyl and uranyl solutions produced the isolable gas-phase complexes, [An(VI)O(2)(CH(3)COCH(3))(4,5,6)](2+), [An(VI)O(2)(CH(3)COCH(3))(3)(H(2)O)](2+), and [An(VI)O(2)(CH(3)CN)(4)](2+); additional complex compositions were observed for uranyl. In accord with relative actinyl stabilities, U(VI)O(2)(2+) > Pu(VI)O(2)(2+) > Np(VI)O(2)(2+), the yields of plutonyl complexes were about an order of magnitude less than those of uranyl, and dipositive neptunyl complexes were not observed. Collision-induced dissociation (CID) of the dipositive coordination complexes in a quadrupole ion trap produced doubly- and singly-charged fragment ions; the fragmentation products reveal differences in underlying chemistries of plutonyl and uranyl, including the lower stability of Pu(VI) as compared with U(VI). Particularly notable was the distinctive CID fragment ion, [Pu(IV)(OH)(3)](+) from [Pu(VI)O(2)(CH(3)COCH(3))(6)](2+), where the plutonyl structure has been disrupted and the tetravalent plutonium hydroxide produced; this process was not observed for uranyl. PMID:21517017

  14. Coordination Complexes of Cobalt.

    ERIC Educational Resources Information Center

    Williams, Gregory M.; And Others

    1989-01-01

    Described is an experiment involving the synthesis and spectral studies of cobalt complexes that not only give general chemistry students an introduction to inorganic synthesis but allows them to conduct a systematic study on the effect of different ligands on absorption spectra. Background information, procedures, and experimental results are

  15. Aqueous uranyl complexes. 3. Potentiometric measurements of the hydrolysis of uranyl(VI) ion at 25{degrees}C

    SciTech Connect

    Palmer, D.A.; Nguyen-Trung, C. [Oak Ridge National Lab., TN (United States)

    1995-12-01

    Potentiometric titrations of uranyl(VI) solutions were conducted using a standard glass/calomel electrode combination over the pH range 3 to 12 at 0.1 mol-kg{sup {minus}1} ionic strength with tetramethylammonium trifluoromethanesulfonate as the supporting electrolyte. The electrodes were calibrated directly on the hydrogen ion concentration scale during the initial stage of each titration. The species, UO{sub 2}{sup 2+}, (UO{sub 2}){sub 2}(OH){sub 2}{sup 2+}, (UO{sub 2}){sub 3}(OH){sub 5}{sup +}, (UO{sub 2}){sub 3}(OH){sub 7}{sup {minus}}, (UO{sub 2}){sub 3}(OH){sub 8}{sup 2-}, and (UO{sub 2}){sub 3}(OH){sub 10}{sup 4-} identified in an earlier Raman study were compatible with the analysis of the titration data. Based on this analysis and application of the extended Debye-Hueckel treatment, the polynuclear species indicated above were assigned overall formation constants at 25{degrees}C and at infinite dilution of -5.51{plus_minus}0.04, -15.3{plus_minus}0.1, -27.77{plus_minus}0.09, -37.65{plus_minus}0.14, and -62.4{plus_minus}0.3, respectively. The results are discussed in reference to hydrolysis quotients reported in the literature for the first three species. Formation quotients for the last two species have not been reported previously.

  16. Uranyl adsorption and surface speciation at the imogolite-water interface: Self-consistent spectroscopic and surface complexation models

    USGS Publications Warehouse

    Arai, Y.; McBeath, M.; Bargar, J.R.; Joye, J.; Davis, J.A.

    2006-01-01

    Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using batch adsorption experiments, X-ray absorption spectroscopy (XAS), and surface complexation modeling. U(VI) uptake on imogolite surfaces was greatest at pH ???7-8 (I = 0.1 M NaNO3 solution, suspension density = 0.4 g/L [U(VI)]i = 0.01-30 ??M, equilibration with air). Uranyl uptake decreased with increasing sodium nitrate concentration in the range from 0.02 to 0.5 M. XAS analyses show that two U(VI) inner-sphere (bidentate mononuclear coordination on outer-wall aluminol groups) and one outer-sphere surface species are present on the imogolite surface, and the distribution of the surface species is pH dependent. At pH 8.8, bis-carbonato inner-sphere and tris-carbonato outer-sphere surface species are present. At pH 7, bis- and non-carbonato inner-sphere surface species co-exist, and the fraction of bis-carbonato species increases slightly with increasing I (0.1-0.5 M). At pH 5.3, U(VI) non-carbonato bidentate mononuclear surface species predominate (69%). A triple layer surface complexation model was developed with surface species that are consistent with the XAS analyses and macroscopic adsorption data. The proton stoichiometry of surface reactions was determined from both the pH dependence of U(VI) adsorption data in pH regions of surface species predominance and from bond-valence calculations. The bis-carbonato species required a distribution of surface charge between the surface and ?? charge planes in order to be consistent with both the spectroscopic and macroscopic adsorption data. This research indicates that U(VI)-carbonato ternary species on poorly crystalline aluminosilicate mineral surfaces may be important in controlling U(VI) mobility in low-temperature geochemical environments over a wide pH range (???5-9), even at the partial pressure of carbon dioxide of ambient air (pCO2 = 10-3.45 atm). ?? 2006 Elsevier Inc. All rights reserved.

  17. Scale-Dependent Rates of Uranyl Surface Complexation Reaction in Sediments

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Kerisit, Sebastien N.; Zachara, John M.; Zhu, Weihuang

    2013-03-15

    Scale-dependency of uranyl[U(VI)] surface complexation rates was investigated in stirred flow-cell and column systems using a U(VI)-contaminated sediment from the US Department of Energy, Hanford site, WA. The experimental results were used to estimate the apparent rate of U(VI) surface complexation at the grain-scale and in porous media. Numerical simulations using molecular, pore-scale, and continuum models were performed to provide insights into and to estimate the rate constants of U(VI) surface complexation at the different scales. The results showed that the grain-scale rate constant of U(VI) surface complexation was over 3 to 10 orders of magnitude smaller, dependent on the temporal scale, than the rate constant calculated using the molecular simulations. The grain-scale rate was faster initially and slower with time, showing the temporal scale-dependency. The largest rate constant at the grain-scale decreased additional 2 orders of magnitude when the rate was scaled to the porous media in the column. The scaling effect from the grain-scale to the porous media became less important for the slower sorption sites. Pore-scale simulations revealed the importance of coupled mass transport and reactions in both intragranular and inter-granular domains, which caused both spatial and temporal dependence of U(VI) surface complexation rates in the sediment. Pore-scale simulations also revealed a new rate-limiting mechanism in the intragranular porous domains that the rate of coupled diffusion and surface complexation reaction was slower than either process alone. The results provided important implications for developing models to scale geochemical/biogeochemical reactions.

  18. Strongly coupled binuclear uraniumoxo complexes from uranyl oxo rearrangement and reductive silylation

    Microsoft Academic Search

    Guy M. Jones; Samuel O. Odoh; Georg Schreckenbach; Nicola Magnani; Polly L. Arnold; Jason B. Love

    2012-01-01

    The most common motif in uranium chemistry is the d0f0 uranyl ion [UO2]2+ in which the oxo groups are rigorously linear and inert. Alternative geometries, such as the cis-uranyl, have been identified theoretically and implicated in oxo-atom transfer reactions that are relevant to environmental speciation and nuclear waste remediation. Single electron reduction is now known to impart greater oxo-group reactivity,

  19. Critical Parameters of Complex Geometries of Intersecting Cylinders Containing Uranyl Nitrate Solution

    SciTech Connect

    J. B. Briggs (INEEL POC); R. E. Rothe

    1999-06-14

    About three dozen previously unreported critical configurations are presented for very complex geometries filled with high concentration enriched uranyl nitrate solution. These geometries resemble a tall, thin Central Column (or trunk of a ''tree'') having long, thin arms (or ''branches'') extending up to four directions off the column. Arms are equally spaced from one another in vertical planes, and that spacing ranges from arms in contact to quite wide spacings. Both the Central Column and the many different arms are critically safe by themselves with each, alone, is filled with fissile solution; but, in combination, criticality occurs due to the interactions between arms and the column. Such neutronic interactions formed the principal focus of this study. While these results are fresh to the nuclear criticality safety industry and to those seeking novel experiments against which to validate computer codes, the experiments, themselves, are not recent. Over 100 experiments were performed at the Rocky Flats Critical Mass Laboratory between September, 1967, and February of the following year.

  20. Critical Parameters of Complex Geometry Intersecting Cylinders Containing Uranyl Nitrate Solution

    SciTech Connect

    Rothe, Robert Emil; Briggs, Joseph Blair

    1999-06-01

    About three dozen previously unreported critical configurations are presented for very complex geometries filled with high concentration enriched uranyl nitrate solution. These geometries resemble a tall, thin Central Column (or trunk of a "tree") having long, thin arms (or "branches") extending up to four directions off the column. Arms are equally spaced from one another in vertical planes; and that spacing ranges from arms in contact to quite wide spacings. Both the Central Column and the many different arms are critically safe by themselves when each, alone, is filled with fissile solution; but, in combination, criticality occurs due to the interactions between arms and the column. Such neutronic interactions formed the principal focus of this study. While these results are fresh to the nuclear criticality safety industry and to those seeking novel experiments against which to validate computer codes, the experiments, themselves, are not recent. Over 100 experiments were performed at the Rocky Flats Critical Mass Laboratory between September, 1967, and February of the following year.

  1. Influence of Acidity on Uranyl Nitrate Association in Aqueous Solutions: A Molecular Dynamics Simulation Study

    SciTech Connect

    de Almeida, Valmor F [ORNL; Cui, Shengting [ORNL; Khomami, Bamin [ORNL; Ye, Xianggui [ORNL; Smith, Rodney Bryan [ORNL

    2010-01-01

    Uranyl ion complexation with water and nitrate is a key aspect of the uranium/plutonium extraction process. We have carried out a molecular dynamics simulation study to investigate this complexation process, including the molecular composition of the various complex species, the corresponding structure, and the equilibrium distribution of the complexes. The observed structures of the complexes suggest that in aqueous solution, uranyls are generally hydrated by 5 water molecules in the equatorial plane. When associating with nitrate ions, a water molecule is replaced by a nitrate ion, preserving the five-fold coordination and planar symmetry. Analysis of the pair correlation function between uranyl and nitrate suggests that nitrates bind to uranyl in aqueous solution mainly in a monodentate mode, although a small portion of bidentates occur. Dynamic association and dissociation between uranyls and nitrates take place in aqueous solution with a substantial amount of fluctuation in the number of various uranyl nitrate species. The average number of the uranyl mononitrate complexes shows a dependence on acid concentration consistent with equilibrium-constant analysis, namely, the concentration of [UO2NO3]+ increases with nitric acid concentration.

  2. Discussion on the complexing ability of the uranyl ion with several crown ethers and cryptands in water and in propylene carbonate

    SciTech Connect

    Brighli, M.; Fux, P.; Lagrange, J.; Lagrange, P.

    1985-01-02

    Interactions of the uranyl ion (UO/sub 2//sup 2 +/) with some common crown ethers (12C4, 15C5, 18C6, DB-18C6) and cryptands (22,222) are investigated in aqueous and propylene carbonate (PC) solutions, I = 0.1 M ((TEA)ClO/sub 4/). Stability constants of the complexes formed are determined by potentiometric and spectrophotometric measurements. Discussions on the stability constants of the complexes allow us to postulate whether or not direct uranyl-macrocycle bonds are obtained. In PC solution, uranyl inner-sphere complexes with 18C6, DB-18C6, 22, and 222 are formed with the uranyl ion probably inside or partially enclosed in the ligand cavity. In aqueous media, complexation occurs only with crown ethers by formation of hydrogen bonds between hydrogen of water molecules of the hydrate shell of the uranyl ion and oxygen atoms of the crown ether (UO/sub 2//sup 2 +/ outer-sphere complexes). 31 references, 5 figures, 3 tables.

  3. Sodium glass electrode in propylene carbonate for study of uranyl ion complexed to 18-crown-6 and substituted derivatives

    SciTech Connect

    Fux, P.; Lagrange, J.; Lagrange, P.

    1984-02-01

    Complexation of the uranyl ion (UO/sub 2//sup 2 +/) by 18-crown-6 and its substituted derivatives (dibenzo and dicyclohexyl) has been studied in propylene carbonate (0.1 M TEACIO/sub 4/) at 25/sup 0/C, using Na/sup +/ as a competing ion and a Na/sup +/ glass selective electrode. The response of the Na/sup +/ glass electrode in propylene carbonate with H/sup +/ as an interfering ion has been studied. Concentrations of Na/sup +/-free ions were calculated by using the extended Nicolsky equation. The stability constants determined by this method agree with those determined spectrophotometrically. 24 references, 3 figures, 1 table.

  4. Polymer complexes. LX. Supramolecular coordination and structures of N(4-(acrylamido)-2-hydroxybenzoic acid) polymer complexes.

    PubMed

    Ghoneim, M M; El-Sonbati, A Z; El-Bindary, A A; Diab, M A; Serag, L S

    2015-04-01

    A number of novel polymer complexes of various anions of copper(II), cobalt(II), nickel(II) and uranyl(II) with N(4-(acrylamido)-2-hydroxy benzoic acid) (ABH) have been synthesized and characterized by elemental analysis, IR, 1H NMR, magnetic susceptibility measurements, electronic spin resonance, vibrational spectra and thermal analysis. The molecular structures of the ligand are optimized theoretically and the quantum chemical parameters are calculated. Tentative structures for the polymeric metal complexes due to their potential application are also suggested. The IR data exhibit the coordination of ONO2/OAc/SO4 with the metal ions in the polymeric metal complex. Vibrational spectra indicate coordination of carboxylate oxygen and phenolic OH of the ligand giving a MO4 square planar chromophore. Ligand field ESR spectra support square planar geometry around Cu(II). The thermal decomposition of the polymer complexes were discussed in relation to structure, and the thermodynamic parameters of the decomposition stages were evaluated applying Coast-Redfern and Horowitz-Metzger methods. PMID:25589393

  5. Polymer complexes. LX. Supramolecular coordination and structures of N(4-(acrylamido)-2-hydroxybenzoic acid) polymer complexes

    NASA Astrophysics Data System (ADS)

    Ghoneim, M. M.; El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.; Serag, L. S.

    2015-04-01

    A number of novel polymer complexes of various anions of copper(II), cobalt(II), nickel(II) and uranyl(II) with N(4-(acrylamido)-2-hydroxy benzoic acid) (ABH) have been synthesized and characterized by elemental analysis, IR, 1H NMR, magnetic susceptibility measurements, electronic spin resonance, vibrational spectra and thermal analysis. The molecular structures of the ligand are optimized theoretically and the quantum chemical parameters are calculated. Tentative structures for the polymeric metal complexes due to their potential application are also suggested. The IR data exhibit the coordination of ONO2/OAc/SO4 with the metal ions in the polymeric metal complex. Vibrational spectra indicate coordination of carboxylate oxygen and phenolic OH of the ligand giving a MO4 square planar chromophore. Ligand field ESR spectra support square planar geometry around Cu(II). The thermal decomposition of the polymer complexes were discussed in relation to structure, and the thermodynamic parameters of the decomposition stages were evaluated applying Coast-Redfern and Horowitz-Metzger methods.

  6. Uranyl complexes with diamide ligands: a quantum mechanics study of chelating properties in the gas phase.

    PubMed

    Coupez, Bernard; Wipff, Georges

    2003-06-01

    We report a quantum mechanical study on the complexes of UO(2)(2+) with diamide ligands L of malonamide and succinamide type, respectively, forming 6- and 7-chelate rings in their bidentate coordination to uranium. The main aims are to (i) assess how strong the chelate effect is (i.e., the preference for bi- versus monodentate binding modes of L), (ii) compare these ligands as a function of the chelate ring size, and (iii) assess the role of neutralizing counterions. For this purpose, we consider UO(2)L(2+), UO(2)L(2)(2+), UO(2)L(3)(2+), and UO(2)X(2)L type complexes with X(-) = Cl(-) versus NO(3)(-). Hartree-Fock and DFT calculations lead to similar trends and reveal the importance of saturation and steric repulsions ("strain") in the first coordination sphere. In the unsaturated UO(2)L(2+), UO(2)L(2)(2+), and UO(2)Cl(2)L complexes, the 7-ring chelate is preferred over the 6-ring chelate, and bidentate coordination is preferred over the monodentate one. However, in the saturated UO(2)(NO(3))(2)L complexes, the 6- and 7-chelating ligands have similar binding energies, and for a given ligand, the mono- and bidentate binding modes are quasi-isoenergetic. These conclusions are confirmed by the calculations of free energies of complexation in the gas phase. In condensed phases, the monodentate form of UO(2)X(2)L complexes should be further stabilized by coordination of additional ligands, as well as by interactions (e.g., hydrogen bonding) of the "free" carbonyl oxygen, leading to an enthalpic preference for this form, compared to the bidentate one. We also considered an isodesmic reaction exchanging one bidentate ligand L with two monoamide analogues, which reveals that the latter are clearly preferred (by 23-14 kcal/mol at the HF level and 24-12 kcal/mol at the DFT level). Thus, in the gas phase, the studied bidentate ligands are enthalpically disfavored, compared to bis-monodentate analogues. The contrast with trends observed in solution hints at the importance of "long range" forces (e.g., second shell interactions) and entropy effects on the chelate effect in condensed phases. PMID:12767210

  7. The Complexes of Bisphosphonate and Magnetite Nanoparticles to Remove Uranyl Ions from Aqueous Phase

    SciTech Connect

    Wang, L.; Yang, Z.; Gao, J.; Xu, K.; Gu, H.; Xu, B. [Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China); Zhang, B.; Zhang, X. [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)

    2007-03-20

    Using tetraethyl-3-amino-propane-1,1-bisphosphonate (BP) as the functional molecule, we functionalized Fe3O4 magnetic nanoparticles via dopamine (DA) linkage to create a system with an Fe3O4-DA-BP nanostructure, which possesses high specificity for removing uranyl ions from water or blood. This work demonstrates that magnetic nanoparticles, combined with specific receptor-ligand interactions, promise a sensitive and rapid platform for the detection, recovery, and decorporation of radioactive metal toxins from biological environment.

  8. COMPLEXANTS FOR ACTINIDE ELEMENT COORDINATION AND IMMOBILIZATION

    EPA Science Inventory

    We propose that inorganic clusters known as polyoxoanions (POAs) can be exploited as complexants for actinide (An) ion coordination and immobilization. Our objective is to develop rugged, stoichiometrically well-defined POAs that act as molecular containers of An elements. Poly...

  9. Effect of nitrate, perchlorate, and water on uranyl(VI) speciation in a room-temperature ionic liquid: a spectroscopic investigation.

    PubMed

    Pasilis, Sofie P; Blumenfeld, Alexander

    2011-09-01

    Room-temperature ionic liquids form potentially important solvents in novel nuclear waste reprocessing methods, and the solvation, speciation, and complexation behaviors of lanthanides and actinides in these solvents are of great current interest. In the study reported here, the coordination environment of uranyl(VI) in solutions of the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf(2)N]) containing perchlorate, tetrabutylammonium nitrate, and water was investigated using Raman, ATR-FTIR, and NMR spectroscopies in order to better understand the role played in uranyl(VI) solution chemistry in room-temperature ionic liquids by water and other small, weakly complexing ligands. The (2)H NMR chemical shift for water in a solution of uranyl perchlorate hexahydrate in [EMIM][Tf(2)N] appears at 6.52 ppm, indicating that water is coordinated to uranyl(VI). A broad ?(OH) stretching mode at 3370 cm(-1) in the ATR-FTIR spectrum shows that this coordinated water is engaged in hydrogen bonding with water molecules in a second coordination sphere. A significant upfield shift in the (2)H NMR signal for water and the appearance of distinct ?(as)(HOH) (at 3630 cm(-1)) and ?(s)(HOH) (at 3560 cm(-1)) vibrational bands in the ATR-FTIR spectra show that coordinated water is displaced by nitrate upon formation of the UO(2)(NO(3))(2) and UO(2)(NO(3))(3)(-) complexes. The Raman spectra indicate that perchlorate complexed to uranyl(VI) is also displaced by nitrate. Our results indicate that perchlorate and water, though weakly complexing ligands, do have a role in uranyl(VI) speciation in room-temperature ionic liquids and that Raman, infrared, and NMR spectroscopies are valuable additions to the suite of tools currently used to study the chemical behavior of uranyl(VI)-ligand complexes in these solvents. PMID:21786806

  10. Nitrite complexes of uranium and thorium.

    PubMed

    Dulong, Florian; Pouessel, Jacky; Thury, Pierre; Berthet, Jean-Claude; Ephritikhine, Michel; Cantat, Thibault

    2013-03-25

    The first examples of inorganic nitrite complexes of the natural actinides are described, including the structures of the homoleptic thorium(IV) [PPh(4)](2)[Th(NO(2))(6)] and the uranyl(VI) [PPh(4)](2)[UO(2)(NO(2))(4)] complexes; the nitrite ligand can adopt two different coordination modes in the coordination sphere of the uranyl ion and is unstable towards reduction. PMID:23416542

  11. Development and Application of an Assay for Uranyl Complexation by Fungal Metabolites, Including Siderophores

    Microsoft Academic Search

    Joanna C. Renshaw; Verity Halliday; Geoffrey D. Robson; Anthony P. J. Trinci; Marilyn G. Wiebe; Francis R. Livens; David Collison; Robin J. Taylor

    2003-01-01

    An assay to detect UO2 2 complexation was developed based on the chrome azurol S (CAS) assay for siderophores (B. Schwyn and J. B. Neilands, Anal. Biochem. 160:47-56, 1987) and was used to investigate the ability of fungal metabolites to complex actinides. In this assay the discoloration of two dyed agars (one containing a CAS-Fe3 dye and the other containing

  12. SYNTHESIS, CHARACTERIZATION, AND STRUCTURE OF A URANYL COMPLEX WITH A DISULFIDE LIGAND, BIS(DI-n-PROPYLAMMONIUM) DISULFIDOBIS (DI-n-PROPYLMONOTHIOCARBAMATO) DIOXOURANATE(VI)

    SciTech Connect

    Perry, Dale L.; Zalkin, Allan; Ruben, Helena; Templeton, David H.

    1981-05-01

    Olive-green crystals of the title compound, [({underline n}-C{sub 3}H{sub 7}){sub 2}NH{sub 2}{sup +}]{sub 2} [UO(({underline n}-C{sub 3}H{sub 7}){sub 2}NCOS){sub 2}(S{sub 2}){sup -2}, are orthorhombic, space group Pcan, with {underline a}= 15.326(6) {Angstrom}, {underline b} = 17.474(6) {Angstrom}, {underline C} = 14.728(6) {Angstrom}, and Z = 4, (d{sub X} = 1.45 g/cm{sup 3}). For 1833 data, I >{sigma}, R = 0.052, and R{sub w} = 0.069. The structure was revealed by single-crystal x-ray diffraction studies to consist of [(n-C{sub 3}H{sub 7}){sub 2}NH{sub 2}]+ cations and [UO{sub 2}(({underline n|-C{sub 3}H{sub 7}){sub 2}NCOS){sub 2}(S{sub 2}){sup -2} anions with the uranium atom at the center of an irregular hexagonal bipyramid. The uranyl oxygen atoms occupy the axial positions. The equatorial coordination plane contains the disulfide (S{sub 2}{sup -2}) group bonded in a "side-on" fashion, and two oxygen and two sulfur donor atoms from the monothiocarbamate ligands. Interatomic distances are S-S = 2.05(1) {Angstrom}, U-S= 2.714(3) {Angstrom} (disulfide); U-S= 2.871(3) {Angstrom} and U-O = 2.46(1) {Angstrom} (thiocarbamate); U-O = 1.81(1) {Angstrom} (uranyl), The nitrogen atom in the dipropylammonium cation is hydrogen bonded to the uranyl oxgyen atoms,

  13. Development and application of an assay for uranyl complexation by fungal metabolites, including siderophores.

    PubMed

    Renshaw, Joanna C; Halliday, Verity; Robson, Geoffrey D; Trinci, Anthony P J; Wiebe, Marilyn G; Livens, Francis R; Collison, David; Taylor, Robin J

    2003-06-01

    An assay to detect UO(2)(2+) complexation was developed based on the chrome azurol S (CAS) assay for siderophores (B. Schwyn and J. B. Neilands, Anal. Biochem. 160:47-56, 1987) and was used to investigate the ability of fungal metabolites to complex actinides. In this assay the discoloration of two dyed agars (one containing a CAS-Fe(3+) dye and the other containing a CAS-UO(2)(2+) dye) caused by ligands was quantified. The assay was tested by using the siderophore desferrioxamine B (DFO), and the results showed that there was a regular, reproducible relationship between discoloration and the amount of siderophore added. The ratio of the discoloration on the CAS-UO(2)(2+) agar to the discoloration on the CAS-Fe(3+) agar was independent of the amount of siderophore added. A total of 113 fungi and yeasts were isolated from three soil samples taken from the Peak District National Park. The fungi were screened for the production of UO(2)(2+) chelators by using the CAS-based assay and were also tested specifically for hydroxamate siderophore production by using the hydroxamate siderophore auxotroph Aureobacterium flavescens JG-9. This organism is highly sensitive to the presence of hydroxamate siderophores. However, the CAS-based assay was found to be less sensitive than the A. flavescens JG-9 assay. No significant difference between the results for each site for the two tests was found. Three isolates were selected for further study and were identified as two Pencillium species and a Mucor species. Our results show that the new assay can be effectively used to screen fungi for the production of UO(2)(2+) chelating ligands. We suggest that hydroxamate siderophores can be produced by mucoraceous fungi. PMID:12788768

  14. Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments

    SciTech Connect

    Stewart, B.D. [Stanford University; Mayes, Melanie [ORNL; Fendorf, Scott [ORNL

    2010-01-01

    Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO{sub 2}{sup 2+} speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K{sub d} values decrease from 48 to 17 L kg{sup -1} for goethite, from 64 to 29 L kg{sup -1} for Hanford sediments, and from 95 to 51 L kg{sup -1} for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ({approx}5) and limited dissolved calcium are optimal for uranium adsorption.

  15. Synthesis of uranyl(II), vanadyl(II) and zirconyl urate complexes, spectral, thermal and biological studies

    NASA Astrophysics Data System (ADS)

    El-Megharbel, Samy M.; El-Metwaly, Nashwa M.; Refat, Moamen S.

    2015-10-01

    Three urate chelations were obtained when uric acid was reacted with UO2(CH3COO)2H2O, VOSO4XH2O and ZrOCl2XH2O salts with neutralized with 0.1 M NaOH aqueous media. The 1:2 metal-to-ligand complexes [(UO2)2(C5H2N4O3)2](H2O), [(ZrO)2(H2O)2(C5H2N4O3)2] and [VO((C5H3N4O3)2] were characterized by elemental analyses, molar conductivity, (infrared, Raman and UV-vis) spectra, effective magnetic moment in Bohr magnetons, and thermal analysis (TG/DTG). The urate ligand coordinates as mononegative bidentate donor towards the mononuclear central vanadium atom and coordinated as binegative tetradentate mode towards the binuclear dioxouranium and zirconyl centers. The antibacterial activity of the metal complexes were tested against some kind of bacteria and fungi strains and compared with uric acid. The ligand, ZrO(II) and UO2(II) complex showed a week potential degradation on calf thymus DNA, whereas VO(II) complex slightly degraded the DNA.

  16. Extended structures and physicochemical properties of uranyl-organic compounds.

    PubMed

    Wang, Kai-Xue; Chen, Jie-Sheng

    2011-07-19

    The ability of uranium to undergo nuclear fission has been exploited primarily to manufacture nuclear weapons and to generate nuclear power. Outside of its nuclear physics, uranium also exhibits rich chemistry, and it forms various compounds with other elements. Among the uranium-bearing compounds, those with a uranium oxidation state of +6 are most common and a particular structural unit, uranyl UO(2)(2+) is usually involved in these hexavalent uranium compounds. Apart from forming solids with inorganic ions, the uranyl unit also bonds to organic molecules to generate uranyl-organic coordination materials. If appropriate reaction conditions are employed, uranyl-organic extended structures (1-D chains, 2-D layers, and 3-D frameworks) can be obtained. Research on uranyl-organic compounds with extended structures allows for the exploration of their rich structural chemistry, and such studies also point to potential applications such as in materials that could facilitate nuclear waste disposal. In this Account, we describe the structural features of uranyl-organic compounds and efforts to synthesize uranyl-organic compounds with desired structures. We address strategies to construct 3-D uranyl-organic frameworks through rational selection of organic ligands and the incorporation of heteroatoms. The UO(2)(2+) species with inactive U?O double bonds usually form bipyramidal polyhedral structures with ligands coordinated at the equatorial positions, and these polyhedra act as primary building units (PBUs) for the construction of uranyl-organic compounds. The geometry of the uranyl ions and the steric arrangements and functionalities of organic ligands can be exploited in the the design of uranyl--organic extended structures, We also focus on the investigation of the promising physicochemical properties of uranyl-organic compounds. Uranyl-organic materials with an extended structure may exhibit attractive properties, such as photoluminescence, photocatalysis, photocurrent, and photovoltaic responses. In particular, the intriguing, visible-light photocatalytic activities of uranyl-organic compounds are potentially applicable in decomposition of organic pollutants and in water-splitting with the irradiation of solar light. We ascribe the photochemical properties of uranyl-organic compounds to the electronic transitions within the U?O bonds, which may be affected by the presence of organic ligands. PMID:21612214

  17. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Watkins, B.E.; Satcher, J.H.

    1995-07-01

    A binuclear, unsymmetric coordinating ligand that is an effective metal chelator has been designed and synthesized. The new ligand has been shown to react readily with iron(II)/(III) forming a variety of coordination complexes. The binuclear complexes are of significant interest since they represent proof-of-principle for the development of coordinatively asymmetric, binuclear metal chelate compounds. Although this structural type of chelator now appears to be common in biological systems, it has not been previously described for inorganic coordination chemistry. The isolation of oxidation products will be helpful in establishing reaction mechanism(s) of these complexes with molecular oxygen. It is expected that this ligand and derivatives of it will play an important role in the development of bioinorganic complexes that aim to mimic enzyme active sites that function by substrate interaction at only one metal site of a multimetal active site.

  18. EXAFS Characterization of Uranyl Interaction at the Calcite-Water Interface

    NASA Astrophysics Data System (ADS)

    Reeder, R. J.; Elzinga, E. J.; Tait, C. D.

    2002-12-01

    Recent studies using X-ray absorption and luminescence spectroscopies have demonstrated uptake and incorporation of uranyl by calcite. X-ray microprobe studies on uranyl-reacted calcite single crystals reveal that uranyl exhibits preferences for specific surface sites. These preferences are likely expressed upon adsorption of uranyl species at the calcite-water interface. We have used X-ray absorption fine structure (EXAFS), combined with luminescence spectroscopy, to characterize the interactions of uranyl carbonate species with the calcite surface in the pH range 7.4-8.3. To minimize the potential for dissolution or precipitation, solutions were pre-equilibrated with reagent calcite powder for 3 weeks, with pH stabilizing at 8.3. For other experiments, the pH was adjusted initially to achieve a final pH of 7.4 after aging for 3 weeks. Uranyl carbonate solution was added to the pre-equilibrated suspensions to achieve initial U(VI) concentrations ranging from 5 uM to 5 mM. Suspensions were filtered to recover the calcite, but were kept moist to retain the sorbed complexes at the calcite-water interface. Multiple EXAFS spectra were collected using a multi-element Ge detector at beamline 12-BM at the APS and analyzed using standard methods. Fourier transforms (FT) of the spectra contain features corresponding to two axial oxygens and a shell of equatorial oxygens, as well as weaker features at higher R. For suspensions having initial U(VI) concentrations from 5-100 uM, a shoulder is observed in the FT on the high-R side of the equatorial oxygen, and fitting suggests minor splitting of this shell. For higher initial U(VI) concentrations, including the highest U(VI) concentration, 5 mM, the splitting becomes more pronounced. Weak features in the FT at higher-R can be fitted with backscattering from carbon, oxygen, and calcium shells, although fits without calcium provide nearly the same agreement. Luminescence spectroscopy reveals the presence of multiple uranyl species sorbed on the calcite from suspensions with 100 uM U(VI) and lower concentrations. The presence of multiple species may account for the splitting of the equatorial coordination indicated by EXAFS. For higher U(VI) concentrations, the luminescence results are consistent with formation of a schoepite-like precipitate. Understanding the complex interactions of uranyl at the calcite-water interface requires complementary data from multiple techniques.

  19. Polythiophene coordination complexes as high performance lithium storage materials

    NASA Astrophysics Data System (ADS)

    Mao, Ya; Kong, Qingyu; Shen, Lian; Wang, Zhaoxiang; Chen, Liquan

    2014-02-01

    Polythiophene (PTh)-based coordination complexes, polythiophene-iron (PTh-Fe) and polythiophene-iron-oxygen (PTh-Fe-O) were synthesized by chemical method and proved to be novel high-performance organometallic lithium-storage materials. Extended X-ray absorption ?ne structural (EXAFS) spectroscopy and density functional theory (DFT) calculations indicate that these complexes have layered structures. It is believed that the strong and stable Fe-S coordination creates sites of lithium storage and ensures the high specific capacity and outstanding cycle performance of the PTh-based complexes.

  20. Charge transfer vibronic transitions in uranyl tetrachloride compounds;

    SciTech Connect

    Liu, G. K.; Deifel, N. P.; Cahill, C. L. (Chemical Sciences and Engineering Division); (George Washington University)

    2012-01-01

    The electronic and vibronic interactions of uranyl (UO{sub 2}){sup 2+} in three tetrachloride crystals have been investigated with spectroscopic experiments and theoretical modeling. Analysis and simulation of the absorption and photoluminescence spectra have resulted in a quantitative understanding of the charge transfer vibronic transitions of uranyl in the crystals. The spectra obtained at liquid helium temperature consist of extremely narrow zero-phonon lines (ZPL) and vibronic bands. The observed ZPLs are assigned to the first group of the excited states formed by electronic excitation from the 3{sigma} ground state into the f{sub {delta}{phi}}, orbitals of uranyl. The Huang-Rhys theory of vibronic coupling is modified successfully for simulating both the absorption and luminescence spectra. It is shown that only vibronic coupling to the axially symmetric stretching mode is Franck-Condon allowed, whereas other modes are involved through coupling with the symmetric stretching mode. The energies of electronic transitions, vibration frequencies of various local modes, and changes in the O=U=O bond length of uranyl in different electronic states and in different coordination geometries are evaluated in empirical simulations of the optical spectra. Multiple uranyl sites derived from the resolution of a superlattice at low temperature are resolved by crystallographic characterization and time- and energy-resolved spectroscopic studies. The present empirical simulation provides insights into fundamental understanding of uranyl electronic interactions and is useful for quantitative characterization of uranyl coordination.

  1. Charge Transfer Vibronic Transitions in Uranyl Tetrachloride Compounds

    SciTech Connect

    Liu, Guokui [Argonne National Lab. (ANL), Argonne, IL (United States); Deifel, Nicholas P. [George Washington Univ., Washington, DC (United States); Cahill, Christopher L. [George Washington Univ., Washington, DC (United States); Zhurov, Vladimir V. [Univ. of Toledo, OH (United States); Pinkerton, A. Alan [Univ. of Toledo, OH (United States)

    2012-01-19

    The electronic and vibronic interactions of uranyl (UO?)2+ in three tetrachloride crystals have been investigated with spectroscopic experiments and theoretical modeling. Analysis and simulation of the absorption and photoluminescence spectra have resulted in a quantitative understanding of the charge transfer vibronic transitions of uranyl in the crystals. The spectra obtained at liquid helium temperature consist of extremely narrow zero-phonon lines (ZPL) and vibronic bands. The observed ZPLs are assigned to the first group of the excited states formed by electronic excitation from the 3? ground state into the f?,? orbitals of uranyl. The HuangRhys theory of vibronic coupling is modified successfully for simulating both the absorption and luminescence spectra. It is shown that only vibronic coupling to the axially symmetric stretching mode is FranckCondon allowed, whereas other modes are involved through coupling with the symmetric stretching mode. The energies of electronic transitions, vibration frequencies of various local modes, and changes in the O?U?O bond length of uranyl in different electronic states and in different coordination geometries are evaluated in empirical simulations of the optical spectra. Multiple uranyl sites derived from the resolution of a superlattice at low temperature are resolved by crystallographic characterization and time- and energy-resolved spectroscopic studies. The present empirical simulation provides insights into fundamental understanding of uranyl electronic interactions and is useful for quantitative characterization of uranyl coordination.

  2. Expanded uncertainty regions for complex quantities in polar coordinates

    NASA Astrophysics Data System (ADS)

    Hall, B. D.

    2015-04-01

    The expanded measurement uncertainty of a complex quantity is a region in the complex plane surrounding the measured value. When an estimate is expressed in polar coordinates, simultaneous intervals expressing the uncertainty in the radial and angular coordinates define an annular sector. The performance of annular sectors as uncertainty regions is assessed when the respective uncertainty interval calculations follow the Guide to the Expression of Uncertainty in Measurement. That approach is found to be satisfactory provided the measurand is far from the origin and an appropriate coverage factor is used. An alternative, more conservative, method is investigated that achieves no less than nominal coverage probability for any measurand.

  3. Gas-phase coordination complexes of U(VI)O2(2+), Np(VI)O2(2+), and Pu(VI)O2(2+) with dimethylformamide.

    PubMed

    Rutkowski, Philip X; Rios, Daniel; Gibson, John K; Van Stipdonk, Michael J

    2011-11-01

    Electrospray ionization of actinyl perchlorate solutions in H(2)O with 5% by volume of dimethylformamide (DMF) produced the isolatable gas-phase complexes, [An(VI)O(2)(DMF)(3)(H(2)O)](2+) and [An(VI)O(2)(DMF)(4)](2+), where An = U, Np, and Pu. Collision-induced dissociation confirmed the composition of the dipositive coordination complexes, and produced doubly- and singly-charged fragment ions. The fragmentation products reveal differences in underlying chemistries of uranyl, neptunyl, and plutonyl, including the lower stability of Np(VI) and Pu(VI) compared with U(VI). PMID:21952769

  4. Formic acid interaction with the uranyl(VI) ion: structural and photochemical characterization.

    PubMed

    Lucks, Christian; Rossberg, Andr; Tsushima, Satoru; Foerstendorf, Harald; Fahmy, Karim; Bernhard, Gert

    2013-10-01

    Complex formation between the uranyl(VI) ion and formic acid was studied by infrared absorption (IR) and X-ray absorption (EXAFS) spectroscopy as well as density functional theory (DFT) calculations. In contrast to the acetate ion which forms exclusively a bidentate complex with uranyl(VI), the formate ion binds to uranyl(VI) in a unidentate fashion. The photochemistry of the uranyl(VI)-formic acid system was explored by DFT calculations and photoreduction of uranyl(VI) in the presence of formic acid was found to occur via an intermolecular process, that is, hydrogen abstraction from hydrogenformate by the photo-excited uranyl(VI). There is no photo-induced decarboxylation of uranyl(VI) formate via an intramolecular process, presumably due to lack of a C=C double bond. PMID:23900668

  5. Expanding the crystal chemistry of uranyl peroxides: four hybrid uranyl-peroxide structures containing EDTA.

    PubMed

    Qiu, Jie; Ling, Jie; Sieradzki, Claire; Nguyen, Kevin; Wylie, Ernest M; Szymanowski, Jennifer E S; Burns, Peter C

    2014-11-17

    The first four uranyl peroxide compounds containing ethylenediaminetetra-acetate (EDTA) were synthesized and characterized from aqueous uranyl peroxide nitrate solutions with a pH range of 5-7. Raman spectra demonstrated that reaction solutions that crystallized [NaK15[(UO2)8(O2)8(C10H12O10N2)2(C2O4)4](H2O)14] (1) and [Li4K6[(UO2)8(O2)6(C10H12O10N2)2(NO3)6](H2O)26] (2) contained excess peroxide, and their structures contained oxidized ethylenediaminetetraacetate, EDTAO2(4-). The solutions from which [K4[(UO2)4(O2)2(C10H13O8N2)2(IO3)2](H2O)16] (3) and LiK3[(UO2)4(O2)2(C10H12O8N2)2(H2O)2](H2O)18 (4) crystallized contained no free peroxide, and the structures incorporated intact EDTA(4-). In contrast to the large family of uranyl peroxide cage clusters, coordination of uranyl peroxide units in 1-4 by EDTA(4-) or EDTAO2(4-) results in isolated tetramers or dimers of uranyl ions that are bridged by bidentate peroxide groups. Two tetramers are bridged by EDTAO2(4-) to form octamers in 1 and 2, and dimers of uranyl polyhedra are linked through iodate groups in 3 and EDTA(4-) in 4, forming chains in both cases. In each structure the U-O2-U dihedral angle is strongly bent, at ?140, consistent with the configuration of this linkage in cage clusters and other recently reported uranyl peroxides. PMID:25350361

  6. High-coordinate gold(I) complexes with dithiocarboxylate ligands.

    PubMed

    Kaub, Christoph; Augenstein, Timo; Bauer, Thomas O; Rothe, Elisa; Esmezjan, Lars; Schnemann, Volker; Roesky, Peter W

    2014-05-01

    Ferrocene dithiocarboxylate has been introduced into the chemistry of gold(I) and copper(I). First, a modified synthesis of piperidinium ferrocene dithiocarboxylate (1) is reported. Reaction of this reagent with [Au(tht)Cl] in the presence of different phosphines resulted in monomeric, dimeric, and polymeric structures. Although gold(I) is usually two coordinate, mainly three- and four-fold coordinated compounds were obtained by using ferrocene dithiocarboxylate as ligands. The isolated compounds are [(FcCSS)Au(PPh3)2] (2) (FcCSS = ferrocene dithiocarboxylate), [(FcCSS)Au2(dppm)2] (3) (dppm = bis(diphenylphosphino)methane), and [(FcCSS)Au(dppf)]n (4) (dppf = bis(diphenylphosphino)ferrocene) [{(FcCSS)Au}2(dppp)] (5) (dppp = bis(diphenylphosphino)propane). The FcCSS ligand shows a remarkable flexible coordination mode. It coordinates either in a monodentate, a chelating, or in a metal bridging mode. In the four gold(I) complexes 2-5 four different coordination modes of the FcCSS ligand are seen. Attempts to extend this rich coordination chemistry to other coinage metals were only partly successful. [(FcCSS)Cu(PPh3)2] (6) was obtained from the reaction of piperidinium ferrocene dithiocarboxylate with [(Ph3P)3CuCl]. (57)Fe-Mssbauer spectroscopy was performed for compounds 2-4. The spectra show isomer shifts and quadrupole splittings that are typical for diamagnetic ferrocenes. PMID:24735256

  7. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Baldwin, D.; Watkins, B.E.; Satcher, J.H.

    1993-12-31

    The authors are investigating the structure/activity relationships of the bacterial enzyme, methane monooxygenase, which catalyzes the specific oxidation of methane to methanol. They then utilize this information to design and synthesize inorganic coordination complexes that mimic the function of the native enzyme but are more robust and have higher catalytic site density. They envision these catalysts to be useful in process catalytic reactors in the conversion of methane in natural gas to liquid methanol.

  8. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Watkins, B.E.; Satcher, J.H.

    1995-03-01

    We are investigating the structure/activity relationships of the bacterial enzyme methane monooxygenase, which catalyzes the specific oxidation of methane to methanol. We then utilize this information to design and synthesize inorganic coordination complexes that mimic the function of the native enzyme but are more robust and have higher catalytic site density. We envision these catalysts to be useful in process catalytic reactors in the conversion of methane in natural gas to liquid ethanol.

  9. Coordinating postmitotic nuclear pore complex assembly with abscission timing

    PubMed Central

    Mackay, Douglas R

    2011-01-01

    Cells divide and accurately inherit genomic and cellular content through synchronized changes in cellular organization and chromosome dynamics. Although DNA segregation, nuclear reformation and cytokinesis/abscission temporally overlap, little is known about how these distinct events are coordinated to ensure accurate cell division. Recently, we found that disruption of postmitotic nuclear pore complex assembly, an essential aspect of the newly forming nuclear envelope, triggers an Aurora B-dependent delay in abscission. This delay is further characterized by mislocalized, aberrantly active Aurora B in the cytoplasm of midbody-stage cells. These results support a model in which an Aurora B-mediated abscission checkpoint provides surveillance of nuclear pore complex formation to ensure that elements of nuclear architecture are fully formed before daughter cells are physically separated. Here we discuss the process of nuclear pore complex assembly, describe potential mechanisms that may explain how this process could be coordinated with abscission and postulate why such a checkpoint mechanism may exist. PMID:21941107

  10. Temperature-dependent electroluminescence from (Eu, Gd) coordination complexes

    Microsoft Academic Search

    Xianmin Zhang; Runguang Sun; Qianbing Zheng; Takayoshi Kobayashi; Wenlian Li

    1997-01-01

    Light emission from single-layered electroluminescent devices is described in which (Eu, Gd) coordination complexes, (Eu0.1Gd0.9)(TTA)3(TPPO)2, and electron transport material oxadiazole derivative, 2-(4-biphenyl)-5-(4-t-butylphenylyl)-1,3,4-oxadiazole, are dispersed in a hole-transporting host polymer poly(N-vinylcarbazole) film. The color of the emitted electroluminescence changes smoothly from green-white to red with temperature varying from 77 to 300 K. This phenomenon is discussed in terms of temperature dependent

  11. Ionothermal synthesis of uranyl compounds that incorporate imidazole derivatives

    SciTech Connect

    Wylie, Ernest M.; Dustin, Megan K.; Smith, Jeremy S. [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2013-01-15

    Ionothermal reactions of uranyl nitrate with various salts in methylimidazolium-based ionic liquids have produced single crystals of three uranyl compounds that incorporate imidazole derivatives as charge-balancing cations. (C{sub 4}H{sub 7}N{sub 2})[(UO{sub 2})(PO{sub 3}F)(F)] (1) crystallizes in space group C2, a=17.952(1) A, b=6.9646(6) A, c=8.5062(7) A, {beta}=112.301(1) Degree-Sign , (C{sub 6}H{sub 11}N{sub 2}){sub 2}[(UO{sub 2})(SO{sub 4}){sub 2}] (2) crystallizes in space group C2/c, a=31.90(1) A, b=9.383(5) A, c=13.770(7) A, {beta}=93.999(7) Degree-Sign and (C{sub 6}H{sub 11}N{sub 2})[(UO{sub 2}){sub 2}(PO{sub 4})(HPO{sub 4}) (3) crystallizes in space group P2{sub 1}/n, a=9.307(2), b=18.067(4), c=9.765(2), {beta}=93.171(2). The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions coordinated by three O atoms and two F atoms in 1 and five O atoms in 2 and 3 to give pentagonal bipyramids. The structural unit in 1 is composed of F-sharing dimers of uranyl pentagonal bipyramids linked into sheets through corner-sharing fluorophosphate tetrahedra. The structural unit in 2 is composed of uranyl pentagonal bipyramids with one chelating sulfate tetrahedron linked into chains by three other corner-sharing sulfate tetrahedra. In 3, the structural unit is composed of chains of uranyl pentagonal bipyramids linked into sheets through edge- and corner-sharing phosphate and hydrogen phosphate tetrahedra. N-methylimidazolium cations occupy the interstitial space between the uranyl fluorophosphate sheets in 1, whereas 1-ethyl-3-methylimidazolium cations link the uranyl sulfate and phosphate units in 2 and 3 into extended structures. - Graphical abstract: The synthesis of uranyl compounds by ionothermal treatment is explored, and provides three novel compounds and insights concerning the role of water in controlling the structural units. Highlights: Black-Right-Pointing-Pointer Ionothermal syntheses have produced three new uranyl compounds. Black-Right-Pointing-Pointer Imidazole derivatives are incorporated as charge-balancing agents. Black-Right-Pointing-Pointer X-ray and spectroscopic analyses reveal variability between imidazole derivatives. Black-Right-Pointing-Pointer This method offers synthetic insight in the absence of water at low temperatures.

  12. Tetranuclear Uranyl Polyrotaxanes: Preferred Selectivity toward Uranyl Tetramer for Stabilizing a Flexible Polyrotaxane Chain Exhibiting Weakened Supramolecular Inclusion.

    PubMed

    Mei, Lei; Wang, Lin; Liu, Cai-Ming; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-07-01

    Introduction of mechanically interlocked components into actinide-based metal-organic materials such as polyrotaxanes will generate an entirely new type of inorganic-organic hybrid materials showing more supramolecular encapsulation-based dynamics. In this work, tetranuclear uranyl-directed polyrotaxanes (UO2 )4 O2 -C5A3-CB6 (1) and (UO2 )4 O2 -C6A3-CB6 (2), which are the first actinide pseudorotaxanes with high-nuclearity uranium centers, were obtained through systematic extension of the string spacer in pseudorotaxane ligands from 1,4-butylene (C4) to 1,5-pentylene (C5) and 1,6-hexylene (C6). Both of the as-synthesized tetranuclear uranyl polyrotaxanes were structurally characterized and analyzed. Considering the structure of UO2 -C4A3-CB6 and the 1,4-butylene string spacer, the preference for the uranyl tetramer may be related to the configurational inversion of the pseudorotaxane ligands from trans mode to cis mode on coordination to the uranyl center. Detailed structural analysis suggests that the length of the stretched string molecules for CB6-encapsulated pseudorotaxanes has remarkable effect on the supramolecular inclusion interactions and the configurations of pseudorotaxanes, and should be responsible for the configurational inversion of pseudorotaxane spacers and subsequent distinct changes of the uranyl building units and geometric structures. PMID:26036243

  13. Novel uranyl(VI) complexes incorporating propylene-bridged salen-type N2O2-ligands: a structural and computational approach.

    PubMed

    Azam, Mohammad; Al-Resayes, Saud I; Velmurugan, Gunasekaran; Venuvanalingam, Ponnambalam; Wagler, Jrg; Kroke, Edwin

    2015-01-14

    The synthesis of the tetradentate dianionic ligand, H2L (2,2'-(1E,1'E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene)bis(methanylylidene)diphenol), from 2,2-dimethyl-1,3-diaminopropane and its reaction with UO2(CH3COO)22H2O in a 1:1 molar ratio in methanol to produce the complex [UO2(L)(CH3OH)] are reported. The isolated compounds have been characterized by elemental analysis, ionization mass spectrometry (ESI-MS), UV/Vis, FT-IR, (1)H- and (13)C-NMR, DEPT-135 spectroscopy, TGA and single-crystal X-ray diffraction. As shown by X-ray crystallography, the coordination geometry around the uranium centre is distorted pentagonal bipyramidal with two imine nitrogen atoms, two phenolic oxygen atoms and one methanol O atom occupying equatorial sites, together with two axial oxo groups. To obtain insights into the structure and spectral properties of the studied complex, density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations have been carried out. The computed results show that LUMO of the complex is featured with uranium f orbital character. TD-DFT results indicate that the complex displays two intense bands and one weak charge transfer band. The charge transfer band is primarily due to HOMO ? LUMO (53%). Two intense bands have main contributions from HOMO-2 ? LUMO (81%) and HOMO-3 ? LUMO (77%) transitions, respectively. TD-DFT results indicate that the complex displays the charge transfer band primarily due to HOMO ? LUMO (53%) and other two charge transfer bands have main contributions from HOMO-2 ? LUMO (81%), HOMO-3 ? LUMO (77%) transitions, respectively. NBO analysis reveals that the ground state of the complex is mainly stabilized by n?n* interaction. EDA analysis reveals that the interaction existing between the ligand and other parts of the complex is mainly electrostatic in nature. PMID:25380389

  14. Barium uranyl diphosphonates

    SciTech Connect

    Nelson, Anna-Gay D., E-mail: nelsoa@umich.edu [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005 (United States); Alekseev, Evgeny V. [Institute of Energy and Climate Research (IEK-6), Forschungszentrum Juelich Wilhelm-Johnen-Strasse, Juelich 52428 (Germany); Ewing, Rodney C. [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005 (United States); Albrecht-Schmitt, Thomas E. [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2012-08-15

    Three Ba{sup 2+}/UO{sub 2}{sup 2+} methylenediphosphonates have been prepared from mild hydrothermal treatment of uranium trioxide, methylendiphosphonic acid (C1P2) with barium hydroxide octahydrate, barium iodate monohydrate, and small aliquots of HF at 200 Degree-Sign C. These compounds, Ba[UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{center_dot}1.4H{sub 2}O (Ba-1), Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2}F{sub 6}]{center_dot}6H{sub 2}O (Ba-2), and Ba{sub 2}[(UO{sub 2}){sub 2}(CH{sub 2}(PO{sub 3}){sub 2})F{sub 4}]{center_dot}5.75H{sub 2}O (Ba-3) all adopt layered structures based upon linear uranyl groups and disphosphonate molecules. Ba-2 and Ba-3 are similar in that they both have UO{sub 5}F{sub 2} pentagonal bipyramids that are bridged and chelated by the diphosphonate moiety into a two-dimensional zigzag anionic sheet (Ba-2) and a one-dimensional ribbon anionic chain (Ba-3). Ba-1, has a single crystallographically unique uranium metal center where the C1P2 ligand solely bridges to form [UO{sub 2}[CH{sub 2}(PO{sub 3}){sub 2}]{sup 2-} sheets. The interlayer space of the structures is occupied by Ba{sup 2+}, which, along with the fluoride ion, mediates the structure formed and maintains overall charge balance. - Graphical abstract: Illustration of the stacking of the layers in Ba{sub 3}[(UO{sub 2}){sub 4}(CH{sub 2}(PO{sub 3}){sub 2}){sub 2})F{sub 6}]{center_dot}6H{sub 2}O viewed along the c-axis. The structure is constructed from UO{sub 7} pentagonal bipyramidal units, U(1)O{sub 7}=gray, U(2)O{sub 7}=yellow, barium=blue, phosphorus=magenta, fluorine=green, oxygen=red, carbon=black, and hydrogen=light peach. Highlights: Black-Right-Pointing-Pointer The polymerization of the UO{sub 2}{sup 2+} sites to form uranyl dimers leads to structural variations in compounds. Black-Right-Pointing-Pointer Barium cations stitch uranyl diphosphonate anionic layers together, and help mediate structure formation. Black-Right-Pointing-Pointer HF acts as both a mineralizing agent and a ligand.

  15. Composition for detecting uranyl

    DOEpatents

    Baylor, L.C.; Stephens, S.M.

    1994-01-01

    The present invention relates to an indicator composition for use in spectrophotometric detection of a substance in a solution, and a method for making the composition. Useful indicators are sensitive to the particular substance being measured, but are unaffected by the fluid and other chemical species that may be present in the fluid. Optical indicators are used to measure the uranium concentration of process solutions in facilities for extracting uranium from ores, production of nuclear fuels, and reprocessing of irradiated fuels. The composition comprises an organohalide covalently bonded to an indicator for the substance, in such a manner that the product is itself an indicator that provides increased spectral resolution for detecting the substance. The indicator is preferably arsenazo III and the organohalide is preferably cyanuric chloride. These form a composition that is ideally suited for detecting uranyl.

  16. Polymer complexes. LIII. Supramolecular coordination modes and structural of novel sulphadrug complexes

    NASA Astrophysics Data System (ADS)

    Diab, M. A.; El-Sonbati, A. Z.; Mohamed, R. H.

    2010-11-01

    Novel polymer complexes of copper(II), palladium(II), platinum(II) and cadmium(II) containing homopolymer [4-acrylamido benzene sulphonyl guanidine; (HL)] and various anions (SO 42-, CH 3COO -, NO 3-, Br - or Cl -) have been designed and carried out. Their structures were investigated by elemental analyses, spectral (IR, UV-vis, 1H NMR and ESR) and magnetic moments. The modes of interactions between the ligand and the metals were discussed, where oxygen (of O dbnd S dbnd O group) and nitrogen atom [of imino nitrogen (NH/N) of the guanidine group] are involved in chelation. The homopolymer shows two types of coordination behaviour. In mononuclear polymer complexes 4 and 6- 10, it acts as a neutral bidentate ligand chelated through the NH and O atoms, whereas in the polymer complexes 1- 3, 5 and 11, monobasic bidentate ligand is coordinated through the -N and -O atoms. The poly-chelates are of 1:1/1:2 (metal-homopolymer) stoichiometry and exhibit four coordination. On the basis of electronic spectral data and magnetic susceptibility measurement square planar geometry has been proposed. The ESR spectral data provided information about their structure on the basis Hamiltonian parameters and degree of covalency. From the electron paramagnetic resonance and spectral data, the orbital reduction factors were calculated.

  17. Understanding the bonding nature of uranyl ion and functionalized graphene: a theoretical study.

    PubMed

    Wu, Qun-Yan; Lan, Jian-Hui; Wang, Cong-Zhi; Xiao, Cheng-Liang; Zhao, Yu-Liang; Wei, Yue-Zhou; Chai, Zhi-Fang; Shi, Wei-Qun

    2014-03-20

    Studying the bonding nature of uranyl ion and graphene oxide (GO) is very important for understanding the mechanism of the removal of uranium from radioactive wastewater with GO-based materials. We have optimized 22 complexes between uranyl ion and GO applying density functional theory (DFT) combined with quasi-relativistic small-core pseudopotentials. The studied oxygen-containing functional groups include hydroxyl, carboxyl, amido, and dimethylformamide. It is observed that the distances between uranium atoms and oxygen atoms of GO (U-OG) are shorter in the anionic GO complexes (uranyl/GO(-/2-)) compared to the neutral GO ones (uranyl/GO). The formation of hydrogen bonds in the uranyl/GO(-/2-) complexes can enhance the binding ability of anionic GO toward uranyl ions. Furthermore, the thermodynamic calculations show that the changes of the Gibbs free energies in solution are relatively more negative for complexation reactions concerning the hydroxyl and carboxyl functionalized anionic GO complexes. Therefore, both the geometries and thermodynamic energies indicate that the binding abilities of uranyl ions toward GO modified by hydroxyl and carboxyl groups are much stronger compared to those by amido and dimethylformamide groups. This study can provide insights for designing new nanomaterials that can efficiently remove radionuclides from radioactive wastewater. PMID:24592814

  18. Coordination and structure of some transition metal piperidinium pentamethylene dithiocarbamate complexes

    Microsoft Academic Search

    Virendra K. Sinha; M. N. Srivastava; H. L. Nigam

    1978-01-01

    Summary Cobalt(II), nickel(ll), and copper(II) complexes of piperidinum pentamethylene dithiocarbamate (pipmdte) have been prepared and studied by spectral (i.r. and absorption) and magnetic methods. The M(pipmdte)CI complexes are probably four coordinate and square planar, the tridentate ligand being coordinated via the two thiocarbamate sulphur atoms and the nitrogen atom of the piperidinium group.

  19. Coordination

    NSDL National Science Digital Library

    Olivia Worland (Purdue University; Biological Sciences)

    2008-06-06

    Coordination is an organized working together of muscles and groups of muscles aimed at bringing about a purposeful movement such as walking or standing. Coordination involves timing and concentration.

  20. Coordinates

    NSDL National Science Digital Library

    David Stern

    This introduction to the labeling of points on a plane by their Cartesian coordinates can optionally be extended to coordinates in 3-dimensional space, to plane polar coordinates and to 3-dimensional polar coordinates. Students should learn to use Cartesian coordinates (x,y) for defining the position of a point in two dimensions and to use Cartesian coordinates (x,y,z) in 3-dimensional space and learn to appreciate the two ways of defining the z axis. Students should also become familiar with some of the tools and terms used by surveyors such as theodolite, azimuth, elevation, and zenith. Optional items for students familiar with trigonometry and with the theorem of Pythagoras are polar coordinates (r,f ) on the plane, Converting (r,f) to (x,y) and vice versa, at least for r, and Spherical polar coordinates (r,q, f) in 3-dimensional space.

  1. Synthesis, characterization, and crystal structures of uranyl compounds containing mixed chromium oxidation states

    SciTech Connect

    Unruh, Daniel K.; Quicksall, Andrew; Pressprich, Laura; Stoffer, Megan; Qiu, Jie [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Nuzhdin, Kirill; Wu, Weiqiang; Vyushkova, Mariya [Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2012-07-15

    The mixed-valence chromium uranyl compounds Li{sub 5}[(UO{sub 2}){sub 4}(Cr(V)O{sub 5})(Cr(VI)O{sub 4}){sub 4}](H{sub 2}O){sub 17} (1), (Mg(H{sub 2}O){sub 6}){sub 5}[(UO{sub 2}){sub 8}(Cr(V)O{sub 5}){sub 2}(Cr(VI)O{sub 4}){sub 8}] (2) and (NH{sub 4}){sub 5}[(UO{sub 2}){sub 4}(Cr(V)O{sub 5})(Cr(VI)O{sub 4}){sub 2}]H{sub 2}O{sub 11} (3) have been synthesized and characterized. Each contains an identical sheet of cation-centered polyhedra. Central to the connectivity of the sheet are four uranyl pentagonal bipyramids that share some of their equatorial vertices, giving a four-membered ring. The Cr(V) cation located near the center of this ring is coordinated by O atoms in a square pyramidal arrangement. The Cr(VI) is tetrahedrally coordinated by O atoms, and these tetrahedra link the four-membered rings of bipyramids. The mixed-valence nature of the sheet was verified by XANES, an EPR spectrum, and bond-valence analysis. Low-valence cations and H{sub 2}O groups reside between the sheets of uranyl and chromate polyhedra, where they provide linkages between adjacent sheets. - Graphical abstract: Three uranyl chromate compounds contain both pentavalent and hexavalent chromium. The unusual topology of the uranyl chromate sheet contains unusual pentavalent chromium in a square pyramidal coordination environment. Highlights: Black-Right-Pointing-Pointer The first uranyl compounds with mixed Cr valences are reported. Black-Right-Pointing-Pointer A sheet of uranyl polyhedra stabilizes pentavalent chromium. Black-Right-Pointing-Pointer Uranyl and chromate polyhedra form a topologically novel sheet.

  2. Selective extraction of uranyl ions using ion-imprinted chelating microspheres.

    PubMed

    Monier, M; Elsayed, Nadia H

    2014-06-01

    In this work, uranyl complex with Schiff base derived from condensation of p-aminostyrene and salicyaldehyde (HASS) was synthesized. Both ligand and uranyl complex were characterized using elemental analysis, FTIR, (1)H and (13)C NMR spectra. The complex was then copolymerized with styrene and divinylbenzene cross-linker using potassium persulfate free radical initiator through emulsion polymerization technique. The uranyl ions were then leached out from the cross-linked network to finally produce uranyl ion-imprinted microspheres (U-PASS), which were investigated using SEM and FTIR. The effect of various significant parameters such as pH, temperature, contact times and initial uranyl concentration on the removal of uranyl from aqueous solution was examined and the results indicated that the adsorption was exothermic in nature and the kinetics of adsorption fit with the second-order kinetic model. Also, Langmuir adsorption isotherm exhibited the best fit with the experimental results with maximum adsorption capacity 147.8 mg/g. Moreover, the selectivity studies revealed that the ion-imprinted microspheres resin exhibited an obvious affinity toward the uranyl ions in presence of other interfering metal ions compared to the non-imprinted resin. PMID:24703676

  3. Barium uranyl diphosphonates

    NASA Astrophysics Data System (ADS)

    Nelson, Anna-Gay D.; Alekseev, Evgeny V.; Ewing, Rodney C.; Albrecht-Schmitt, Thomas E.

    2012-08-01

    Three Ba2+/UO22+ methylenediphosphonates have been prepared from mild hydrothermal treatment of uranium trioxide, methylendiphosphonic acid (C1P2) with barium hydroxide octahydrate, barium iodate monohydrate, and small aliquots of HF at 200 C. These compounds, Ba[UO2[CH2(PO3)2]1.4H2O (Ba-1), Ba3[(UO2)4(CH2(PO3)2)2F6]6H2O (Ba-2), and Ba2[(UO2)2(CH2(PO3)2)F4]5.75H2O (Ba-3) all adopt layered structures based upon linear uranyl groups and disphosphonate molecules. Ba-2 and Ba-3 are similar in that they both have UO5F2 pentagonal bipyramids that are bridged and chelated by the diphosphonate moiety into a two-dimensional zigzag anionic sheet (Ba-2) and a one-dimensional ribbon anionic chain (Ba-3). Ba-1, has a single crystallographically unique uranium metal center where the C1P2 ligand solely bridges to form [UO2[CH2(PO3)2]2- sheets. The interlayer space of the structures is occupied by Ba2+, which, along with the fluoride ion, mediates the structure formed and maintains overall charge balance.

  4. Recent advances in nanoparticle carriers for coordination complexes.

    PubMed

    Sato, Mariana Rillo; da Silva, Patricia Bento; de Souza, Rodrigo Alves; dos Santos, Karen Cristina; Chorilli, Marlus

    2015-01-01

    Coordination compounds are substances in which a central metal atom is bonded to nonmetal atoms, or groups of atoms, called ligands. Examples include vitamin B12, hemoglobin, chlorophyll, dyes and pigments, as well as catalysts used in organic synthesis. Coordination compounds have received much attention in recent years. This interest was prompted by the discovery that several coordination compounds exhibit activity against bacteria, fungi and cancer. Some coordination compounds are not in clinical use, because of poor water solubility. Because they are unable to cross the lipid membranes of cells, bioavailability and efficacy are low. Some researchers have applied nanotechnology to coordination compounds, hoping to reduce the number of doses required and the severity of side effects, and also to improve biological activity. Nanotechnology can deliver active components in sufficient concentrations throughout treatment, guiding it to the desired location of action; conventional treatments do not meet these requirements. In this study we review some drug delivery systems based on nanotechnology, such as microemulsions (MEs), cyclodextrin (CD), polymeric nanoparticles (PN), solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), magnetic and gold nanoparticles (MNPs / AuNPs) and liquid crystalline systems (LC), and coordination compounds. PMID:25579344

  5. Effects of aqueous uranyl speciation on the kinetics of microbial uranium reduction

    NASA Astrophysics Data System (ADS)

    Belli, Keaton M.; DiChristina, Thomas J.; Van Cappellen, Philippe; Taillefert, Martial

    2015-05-01

    The ability to predict the success of the microbial reduction of soluble U(VI) to highly insoluble U(IV) as an in situ bioremediation strategy is complicated by the wide range of geochemical conditions at contaminated sites and the strong influence of aqueous uranyl speciation on the bioavailability and toxicity of U(VI) to metal-reducing bacteria. To determine the effects of aqueous uranyl speciation on uranium bioreduction kinetics, incubations and viability assays with Shewanella putrefaciens strain 200 were conducted over a range of pH and dissolved inorganic carbon (DIC), Ca2+, and Mg2+ concentrations. A speciation-dependent kinetic model was developed to reproduce the observed time series of total dissolved uranium concentration over the range of geochemical conditions tested. The kinetic model yielded the highest rate constant for the reduction of uranyl non-carbonate species (i.e., the 'free' hydrated uranyl ion, uranyl hydroxides, and other minor uranyl complexes), indicating that they represent the most readily reducible fraction of U(VI) despite being the least abundant uranyl species in solution. The presence of DIC, Ca2+, and Mg2+ suppressed the formation of more bioavailable uranyl non-carbonate species and resulted in slower bioreduction rates. At high concentrations of bioavailable U(VI), however, uranium toxicity to S. putrefaciens inhibited bioreduction, and viability assays confirmed that the concentration of non-carbonate uranyl species best predicts the degree of toxicity. The effect of uranium toxicity was accounted for by incorporating the free ion activity model of metal toxicity into the bioreduction rate law. Overall, these results demonstrate that, in the absence of competing terminal electron acceptors, uranium bioreduction kinetics can be predicted over a wide range of geochemical conditions based on the bioavailability and toxicity imparted on U(VI) by solution composition. These findings also imply that the concentration of uranyl non-carbonate species, despite being extremely low, is a determining factor controlling uranium bioreduction at contaminated sites.

  6. Six-coordinate lanthanide complexes: slow relaxation of magnetization in the dysprosium(III) complex.

    PubMed

    Na, Bo; Zhang, Xue-Jing; Shi, Wei; Zhang, Yi-Quan; Wang, Bing-Wu; Gao, Chen; Gao, Song; Cheng, Peng

    2014-11-24

    A series of six-coordinate lanthanide complexes {(H3O)[Ln(NA)2]?H2O}n (H2NA=5-hydroxynicotinic acid; Ln=Gd(III) (1?Gd); Tb(III) (2?Tb); Dy(III) (3?Dy); Ho(III) (4?Ho)) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3?Dy. To suppress the quantum tunneling of the magnetization, 3?Dy diluted by diamagnetic Y(III) ions was also synthesized and magnetically studied. Interesting butterfly-like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3?Dy. The energy barrier (?(?)) and pre-exponential factor (?0) of the diluted 3?Dy are 75?K and 4.2110(-5) s, respectively. This work illustrates a successful way to obtain low-coordination-number lanthanide complexes by a framework approach to show single-ion-magnet-like behavior. PMID:25297951

  7. Control of oxo-group functionalization and reduction of the uranyl ion.

    PubMed

    Arnold, Polly L; Pcharman, Anne-Frdrique; Lord, Rianne M; Jones, Guy M; Hollis, Emmalina; Nichol, Gary S; Maron, Laurent; Fang, Jian; Davin, Thomas; Love, Jason B

    2015-04-01

    Uranyl complexes of a large, compartmental N8-macrocycle adopt a rigid, "Pacman" geometry that stabilizes the U(V) oxidation state and promotes chemistry at a single uranyl oxo-group. We present here new and straightforward routes to singly reduced and oxo-silylated uranyl Pacman complexes and propose mechanisms that account for the product formation, and the byproduct distributions that are formed using alternative reagents. Uranyl(VI) Pacman complexes in which one oxo-group is functionalized by a single metal cation are activated toward single-electron reduction. As such, the addition of a second equivalent of a Lewis acidic metal complex such as MgN?2 (N? = N(SiMe3)2) forms a uranyl(V) complex in which both oxo-groups are Mg functionalized as a result of Mg-N bond homolysis. In contrast, reactions with the less Lewis acidic complex [Zn(N?)Cl] favor the formation of weaker U-O-Zn dative interactions, leading to reductive silylation of the uranyl oxo-group in preference to metalation. Spectroscopic, crystallographic, and computational analysis of these reactions and of oxo-metalated products isolated by other routes have allowed us to propose mechanisms that account for pathways to metalation or silylation of the exo-oxo-group. PMID:25799215

  8. SOME ASPECTS OF THE ANION EXCHANGE BEHAVIOR OF URANYL NITRATE IN THE PRESENCE OF OTHER INORGANIC NITRATES

    Microsoft Academic Search

    J. K. Foreman; I. R. McGowan; T. D. Smith

    1959-01-01

    The addition of inorganic nitrates to aqueous solutions of uranyl ; nitrate enhances the uptake of uranium on the anion-exchange resin Deacidite FF ; in the onder anuninum> calcium> lithium> ammonium. The predominating cause is ; considered to be the facilitation of formation of nitrate complexes by the uranyl ; ion, and of the subsequent ion-exchange, due to the decrease

  9. Investigation of uranyl nitrate extraction from ketone solutions by dimethyl sulfoxide

    Microsoft Academic Search

    A. P. Zazhogin; A. A. Zazhogin; A. I. Komyak; A. I. Serafimovich

    1997-01-01

    Based on an analysis of low-temperature luminescence spectra (T=77 K) of UO2(NO3)2?6H2O solutions in acetone, the mechanisms of formation of a wide group of uranyl complexes in uranyl extraction from solutions\\u000a by dimethyl sulfoxide are studied. It is shown that to increase the coefficient of uranyl distribution between the solution\\u000a and solid phase (in the form of UO2(NO3)2?2DMSO) it is

  10. Coordinates

    NSDL National Science Digital Library

    In this activity, developed by the Lane Community College Geo-STAC program??, students "understand geographic location (absolute and relative) using an interactive Web-based GIS map." The lesson helps review basic concepts of coordinate geometry as they move about the world identifying coordinate relationships and important reference lines. On the site, visitors will find a link to the student activity and teaching guide, as well as link to the web-based GIS map. This is an excellent activity for high school or early undergraduate students for hands-on work with GIS and coordinate systems.

  11. Novel zwitterionic complexes arising from the coordination of an ambiphilic phosphorus-aluminum ligand to gold.

    PubMed

    Devillard, Marc; Nicolas, Emmanuel; Appelt, Christian; Backs, Jana; Mallet-Ladeira, Sonia; Bouhadir, Ghenwa; Slootweg, J Chris; Uhl, Werner; Bourissou, Didier

    2014-12-01

    Coordination of Mes2PC(=CHPh)AltBu2 to metal chlorides has been studied. Bridging P?M-Cl?Al coordinations were observed with Rh and Pd fragments, while chloride abstraction systematically occurred with gold. The resulting zwitterionic complexes have been fully characterized and analyzed by DFT calculations. PMID:25319140

  12. Influence of Nitric Acid on Uranyl Nitrate Association in Aqueous Solutions: A Molecular Dynamics Simulation Study

    Microsoft Academic Search

    Xianggui Ye; R. Bryan Smith; Shengting Cui; Valmor de Almeida; Bamin Khomami

    2010-01-01

    Uranyl ion complexation with water and nitrate is a key aspect of the uranium\\/plutonium extraction process. We have carried out a molecular dynamics simulation study to investigate this complexation process, including the molecular composition of the various complex species, the corresponding structure, and the equilibrium distribution of the complexes. The observed structures of the complexes suggest that in aqueous solution,

  13. Emergent complexity matching in interpersonal coordination: Local dynamics and global variability.

    PubMed

    Fine, Justin M; Likens, Aaron D; Amazeen, Eric L; Amazeen, Polemnia G

    2015-06-01

    Rhythmic coordination with stimuli and other people's movements containing variable or unpredictable fluctuations might involve distinct processes: detecting the fluctuation structure and tuning to or matching the structure's temporal complexity. This framework predicts that global tuning and local parameter adjustments (e.g., position, velocity or phase) can operate independently during coordination (Marmelat & Delignires, 2012). Alternatively, we propose that complexity matching is a result of local phase adjustments during coordination (Delignires & Marmelat, 2014; Torre, Varlet, & Marmelat, 2013). The current study examined this relationship in a rhythmic interpersonal coordination task. Dyads coordinated swinging pendulums that differed in their uncoupled frequencies (detuning). We predicted that frequency detuning would require increased local corrections to maintain the intended phase pattern (in phase). This was expected to yield a relative phase shift accompanied by a change in period complexity and matching. Experimental data and numerical modeling of the pendulum dynamics confirmed our predictions. Increased relative phase shifts occurred simultaneously with increased dissociation between individuals' movement period complexity. This provided evidence that global complexity matching is intricately linked to local movement adjustments and is not a distinct coordination mechanism. These findings are considered with respect to dynamical and computational approaches to interpersonal coordination. (PsycINFO Database Record PMID:25798782

  14. Investigation on coordination number and geometrical conformation of rare earth complexes with catenulate aminopolycarboxylic acid ligands

    Microsoft Academic Search

    Jun Wang; Ping Hu; Bin Liu; Xudong Jin; Yumei Kong; Jingqun Gao; Dan Wang; Baoxin Wang; Rui Xu; Xiangdong Zhang

    2010-01-01

    This article gives an overview on the molecular and crystal structures of rare earth metal (REM) complexes with a series of aminopolycarboxylic acid (APCA) ligands, nitrilotriacetic acid (NTA), ethylenediamine-N,N,N?,N?-tetraacetic acid (EDTA), diethylenetriamine-N,N,N?,N?,N?-pentaacetic acid (DTPA), and triethylenetetramine-N,N,N?,N?,N???,N???-hexaacetic acid (TTHA). Among the REM complexes with the same APCA ligand, the coordination law of coordination numbers and geometrical conformation are discussed. The research

  15. Assessment of CE-ICP/MS hyphenation for the study of uranyl/protein interactions.

    PubMed

    Huynh, Thi-Ngoc Suong; Bourgeois, Damien; Basset, Christian; Vidaud, Claude; Hagge, Agns

    2015-06-01

    Identification of uranyl transport proteins is key to develop efficient detoxification approaches. Therefore, analytical approaches have to be developed to cope with the complexity of biological media and allow the analysis of metal speciation. CE-ICP/MS was used to combine the less-intrusive character and high separation efficiency of CE with the sensitive detection of ICP/MS. The method was based on the incubation of samples with uranyl prior to the separation. Electrophoretic buffers were compared to select a 10 mM Tris to 15 mM NaCl buffer, which enabled analyses at pH 7.4 and limited dissociation. This method was applied to the analysis of a serum. Two main fractions were observed. By comparison with synthetic mixtures of proteins, the first one was attributed to fetuin and in a lesser extent to HSA, and the second one to uranyl unbound to proteins. The analysis showed that fetuin was likely to be the main target of uranyl. CE-ICP/MS was also used to investigate the behavior of the fetuin-uranyl complex, in the presence of carbonate, an abundant complexing agent of uranyl in blood. This method enabled association constants determination, suggesting the occurrence of both FETUA(UO2 (2+) ) and FETUA(UO2 (2+) )(CO3 (2-) ) complexes, depending on the carbonate concentration. PMID:25630637

  16. Interactions of 1-Methylimidazole with UO?(CH?CO?)? and UO?(NO?)?: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion.

    SciTech Connect

    Gutowski, Keith E.; Cocalia, Violina A.; Griffin, Scott T.; Bridges, Nicholas J.; Dixon, David A.; Rogers, Robin D.

    2007-01-24

    The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO?(Ac)? (Ac ) CH?CO?) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H?O binding to both UO?(Ac)? and UO?(NO?)?. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H?O and Meimid ligands to UO?R? (R ) Ac, NO?). For both UO?(NO?)? and UO?(Ac)?, the displacement of H?O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.

  17. Interactions of 1-Methylimidazole with UO?(CH?CO?)? and UO?(NO?)?: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion

    SciTech Connect

    Gutowski, Keith E.; Cocalia, Violina A.; Griffin, Scott T.; Bridges, Nicholas J.; Dixon, David A.; Rogers, Robin D.

    2007-01-24

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO?(Ac)? (Ac =CH?CO?) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H?2O binding to both UO?(Ac)? and UO?(NO?)?. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H?O and Meimid ligands to UO?R? (R ) Ac, NO?). For both UO?(NO?)? and UO?(Ac)?, the displacement of H?O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.

  18. An Extensible Space-Based Coordination Approach for Modeling Complex Patterns in Large Systems

    NASA Astrophysics Data System (ADS)

    Khn, Eva; Mordinyi, Richard; Schreiber, Christian

    Coordination is frequently associated with shared data spaces employing Linda coordination. But in practice, communication between parallel and distributed processes is carried out with message exchange patterns. What, actually, do shared data spaces contribute beyond these? In this paper we present a formal representation for a definition of shared spaces by introducing an "extensible tuple model", based on existing research on Linda coordination, some Linda extensions, and virtual shared memory. The main enhancements of the extensible tuple model comprise: means for structuring of spaces, Internet- compatible addressing of resources, more powerful coordination capabilities, a clear separation of user data and coordination information, support of symmetric peer application architectures, and extensibility through programmable aspects. The advantages of the extensible tuple model (XTM) are that it allows for a specification of complex coordination patterns.

  19. Density functional theory and molecular dynamics study of the uranyl ion (UO?)?.

    PubMed

    Rodrguez-Jeangros, Nicols; Seminario, Jorge M

    2014-03-01

    The detection of uranium is very important, especially in water and, more importantly, in the form of uranyl ion (UO?)?, which is one of its most abundant moieties. Here, we report analyses and simulations of uranyl in water using ab initio modified force fields for water with improved parameters and charges of uranyl. We use a TIP4P model, which allows us to obtain accurate water properties such as the boiling point and the second and third shells of water molecules in the radial distribution function thanks to a fictitious charge that corrects the 3-point models by reproducing the exact dipole moment of the water molecule. We also introduced non-bonded interaction parameters for the water-uranyl intermolecular force field. Special care was taken in testing the effect of a range of uranyl charges on the structure of uranyl-water complexes. Atomic charges of the solvated ion in water were obtained using density functional theory (DFT) calculations taking into account the presence of nitrate ions in the solution, forming a neutral ensemble. DFT-based force fields were calculated in such a way that water properties, such as the boiling point or the pair distribution function stand. Finally, molecular dynamics simulations of a water box containing uranyl cations and nitrate anions are performed at room temperature. The three peaks in the oxygen-oxygen radial distribution function for water were found to be kept in the presence of uranyl thanks to the improvement of interaction parameters and charges. Also, we found three shells of water molecules surrounding the uranyl ion instead of two as was previously thought. PMID:24573498

  20. Theoretical study of the microhydration of mononuclear and dinuclear uranium(VI) species derived from solvolysis of uranyl nitrate in water.

    PubMed

    Onck, Milan; Schrder, Detlef; Slavcek, Petr

    2010-09-01

    The structures and energetics of mononuclear and dinuclear uranium species formed upon speciation of uranyl(VI) nitrate, UO(2)(NO(3))(2), in water are investigated by quantum chemistry using density functional theory and the wavefunction-based methods (MP2, CCSD, CCSD(T)). We provide a discussion of the basic coordination patterns of the various mono- and dinuclear uranyl compounds [(UO(2))(m)(X,Y)(2m-1)(H2O)(n)](+) (m = 1, 2; n = 0-4) found in a recent mass spectrometric study (Tsierkezos et al., Inorg Chem 2009, 48, 6287). The energetics of the complexation of the uranyl dication to the counterions OH(-) and NO(3) (-) as well as the degradation of the dinuclear species were studied by reference to a test set of 16 representative molecules with the MP2 method and the B3LYP, M06, M06-HF, and M06-2X DFT functionals. All DFT functionals provide structures and energetics close to MP2 results, with M06 family being slightly superior to the standard B3LYP functional. PMID:20340110

  1. Supramolecular inclusion-based molecular integral rigidity: a feasible strategy for controlling the structural connectivity of uranyl polyrotaxane networks.

    PubMed

    Mei, Lei; Wang, Lin; Yuan, Li-Yong; An, Shu-Wen; Zhao, Yu-Liang; Chai, Zhi-Fang; Burns, Peter C; Shi, Wei-Qun

    2015-07-14

    The assembly of two-dimensional (2D) large channel uranyl-organic polyrotaxane networks as well as structural regulation of uranyl-bearing units using jointed cucurbit[6]uril-based pseudorotaxanes with integral rigidity based on supramolecular inclusion is presented for the first time. This construction strategy concerning controlling molecular integral rigidity based on supramolecular inclusion may afford an entirely new methodology for coordination chemistry. PMID:26121567

  2. Hybrid uranyl-vanadium nano-wheels.

    PubMed

    Senchyk, G A; Wylie, E M; Prizio, S; Szymanowski, J E S; Sigmon, G E; Burns, P C

    2015-06-01

    Hybrid uranyl-vanadium oxide clusters intermediate between transition metal polyoxometalates and uranyl peroxide cage clusters were obtained by dissolving uranyl nitrate in the ionic liquid 3-ethyl-1-methylimidazolium ethyl sulfate mixed with an aqueous solution containing vanadium. Where sulfate was present, wheel-shaped {U20V20} crystallized and contains ten sulfate tetrahedra, and in the absence of added sulfate, {U2V16}, a derivative of {V18}, was obtained. PMID:26008125

  3. Five coordinated complexes of divalent nickel and copper with ligands derived from acid hydrazides and acetylacetone

    Microsoft Academic Search

    Mahendra P. Teotia; Ishwar Singh; Vidya B. Rana

    1981-01-01

    Summary Picolinic acid hydrazide (PH) and isonicotinic acid hydrazide (INH) react with acetylacetone to form complexes, containing open chain tetradentate ligands, through anin situ process in the presence of nickel and copper salts. The complexes were isolated and characterised as five-coordinate with the aid of analyses, magnetic, e.s.r., electronic and i.r. spectral studies.

  4. Effect of the transition metals on the carnosine coordination complexes structure

    Microsoft Academic Search

    S. D. Demukhamedova; I. N. Alieva; N. M. Gojayev

    2009-01-01

    The spatial and electronic structures of the carnosine monomer coordination complexes with zinc and copper ions were investigated by the semi-empirical of MM+ molecular mechanics and PM3 quantum chemistry methods. The effect of the transition atoms on the geometrical and energy parameters of the monomer complexes with two forms of imidazole ring was studied.

  5. Functional cooperation between FACT and MCM is coordinated with cell cycle and differential complex formation

    Microsoft Academic Search

    Bertrand Chin-Ming Tan; Hsuan Liu; Chih-Li Lin; Sheng-Chung Lee

    2010-01-01

    BACKGROUND: Functional cooperation between FACT and the MCM helicase complex constitutes an integral step during DNA replication initiation. However, mode of regulation that underlies the proper functional interaction of FACT and MCM is poorly understood. METHODS & RESULTS: Here we present evidence indicating that such interaction is coordinated with cell cycle progression and differential complex formation. We first demonstrate the

  6. A Convergent Coordination Chemistry-Based Approach to Dissymmetric Macrocyclic Cofacial Porphyrin Complexes

    SciTech Connect

    Oliveri, Christopher G.; Heo, Jungseok; Nguyen, SonBinh T.; Mirkin, Chad A.; Wawrzak, Zdzislaw (NWU)

    2010-12-03

    We report a highly convergent and modular approach for the synthesis of dissymmetric cofacial porphyrin complexes, which is based upon the weak-link approach to supramolecular coordination chemistry. Specifically, we have utilized a halide-induced ligand rearrangement reaction, which is capable of providing heteroligated mixed-metal porphyrin complexes in quantitative yield. Significantly, the adoption of a coordination chemistry based approach for the synthesis of these complexes allows for facile in situ regulation of the porphyrin-porphyrin interactions through the addition of external chemical stimuli.

  7. Exploring the complexity of the academic fieldwork coordinator role.

    PubMed

    Stutz-Tanenbaum, Patricia; Hanson, Debra J; Koski, Jeanette; Greene, David

    2015-04-01

    A nation-wide survey was conducted of occupational therapy and occupational therapy assistant academic fieldwork coordinators (AFWCs) to describe demographic characteristics and tasks of the role. From the data, 10 clusters of role tasks of the AFWC are described. AFWCs view the position as a final career goal although the majority of respondents reported 5years or less experience. Administrative assistant support and hours dedicated to fieldwork tasks are higher at the professional level than for occupational therapy assistant AFWCs. AFWCs reported difficulty accomplishing tasks in a 40-h work week and limited time for research and scholarship. Recommendations are provided for recruitment and retention through development of a systematic training program and establishment of a national fieldwork education research agenda. PMID:25821881

  8. Surprising Coordination Geometry Differences in Ce(IV)- and Pu(IV)-Maltol Complexes

    SciTech Connect

    Lawrence Berkeley National Laboratory; Raymond, Kenneth; Szigethy, Geza; Xu, Jide; Gorden, Anne E.V.; Teat, Simon J.; Shuh, David K.; Raymond, Kenneth N.

    2008-02-12

    As part of a study to characterize the detailed coordination behavior of Pu(IV), single crystal X-ray diffraction structures have been determined for Pu(IV) and Ce(IV) complexes with the naturally-occurring ligand maltol (3-hydroxy-2-methyl-pyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methyl-pyran-4-one). Although Ce(IV) is generally accepted as a structural analog for Pu(IV), and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the Ce(IV)-bromomaltol complex displays an uncommon ligand arrangement not mirrored in the Pu(IV) complex, although the two metal species are generally accepted to be structural analogs.

  9. Role of the coordination center in photocurrent behavior of a tetrathiafulvalene and metal complex dyad.

    PubMed

    Sun, Yong-Gang; Ji, Shu-Fang; Huo, Peng; Yin, Jing-Xue; Huang, Yu-De; Zhu, Qin-Yu; Dai, Jie

    2014-03-17

    Small organic molecule-based compounds are considered to be promising materials in photoelectronics and high-performance optoelectronic devices. However, photoelectron conversion research based on functional organic molecule and metal complex dyads is very scarce. We design and prepare a series of compounds containing a tetrathiafulvalene (TTF) moiety substituted with pyridylmethylamide groups of formulas [Ni(acac)2L]2CH3OH (1), [Cu2I2L2]THF2CH3CN (2), and [MnCl2L2]n2nCH3CH2OH (3) (L = 4,5-bis(3-pyridylmethylamide)-4',5'-bimethylthio-tetrathiafulvalene, acac = acetylacetone) to study the role of the coordination center in photocurrent behavior. Complex 1 is a mononuclear species, and complex 2 is a dimeric species. Complex 3 is a two-dimensional (2-D) coordination polymer. Spectroscopic and electrochemical properties of these complexes indicate that they are electrochemically active materials. The tetrathiafulvalene ligand L is a photoelectron donor in the presence of electron acceptor methylviologen. The effect of metal coordination centers on photocurrent response behavior is examined. The redox-active metal coordination centers should play an important role in improvement of the photocurrent response property. The different morphologies of the electrode films reflect the dimensions in molecular structures of the coordination compounds. PMID:24592888

  10. Modeling and simulation of complex network attributes on coordinating large multiagent system.

    PubMed

    Xu, Yang; Li, Xiang; Liu, Ming

    2014-01-01

    With the expansion of distributed multiagent systems, traditional coordination strategy becomes a severe bottleneck when the system scales up to hundreds of agents. The key challenge is that in typical large multiagent systems, sparsely distributed agents can only communicate directly with very few others and the network is typically modeled as an adaptive complex network. In this paper, we present simulation testbed CoordSim built to model the coordination of network centric multiagent systems. Based on the token-based strategy, the coordination can be built as a communication decision problem that agents make decisions to target communications and pass them over to the capable agents who will potentially benefit the team most. We have theoretically analyzed that the characters of complex network make a significant difference with both random and intelligent coordination strategies, which may contribute to future multiagent algorithm design. PMID:24955399

  11. Modeling and Simulation of Complex Network Attributes on Coordinating Large Multiagent System

    PubMed Central

    Li, Xiang; Liu, Ming

    2014-01-01

    With the expansion of distributed multiagent systems, traditional coordination strategy becomes a severe bottleneck when the system scales up to hundreds of agents. The key challenge is that in typical large multiagent systems, sparsely distributed agents can only communicate directly with very few others and the network is typically modeled as an adaptive complex network. In this paper, we present simulation testbed CoordSim built to model the coordination of network centric multiagent systems. Based on the token-based strategy, the coordination can be built as a communication decision problem that agents make decisions to target communications and pass them over to the capable agents who will potentially benefit the team most. We have theoretically analyzed that the characters of complex network make a significant difference with both random and intelligent coordination strategies, which may contribute to future multiagent algorithm design. PMID:24955399

  12. Intrinsic hydration of monopositive uranyl hydroxide, nitrate, and acetate cations

    Microsoft Academic Search

    Winnie Chien; Victor Anbalagan; Melvin Zandler; Michael Van Stipdonk; Dorothy Hanna; Garold Gresham; Gary Groenewold

    2004-01-01

    The intrinsic hydration of three monopositive uranyl-anion complexes (UO2A)+ (where A = acetate, nitrate, or hydroxide) was investigated using ion-trap mass spectrometry (IT-MS). The relative rates\\u000a for the formation of the monohydrates [(UO2A)(H2O)]+, with respect to the anion, followed the trend: Acetate ? nitrate ? hydroxide. This finding was rationalized in terms of\\u000a the donation of electron density by the

  13. Coordination of Complex Systems Based on Multi-agent Planning: Application to the Aircraft Simulation Domain

    Microsoft Academic Search

    Frdric Marc; Amal El Fallah-seghrouchni; Irene Degirmenciyan-cartault

    2004-01-01

    \\u000a The design of complex systems needs sophisticated coordination mechanisms. This paper proposes an approach based on multi-agent\\u000a planning to coordinate such systems in the tactical aircraft simulation domain. This paper presents an integral cycle, from\\u000a modelling to validation, that enables the building of feasible multi-agent plans as developped in a project named SCALA promoted\\u000a at Dassault Aviation.

  14. Complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid and related compounds

    Microsoft Academic Search

    D. Vulpius; G. Geipel; L. Baraniak; A. Rossberg; G. Bernhard

    2006-01-01

    SummaryThe complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid as well as with benzoic acid and 4-hydroxybenzoic\\u000a acid was studied. In aqueous solution weak carboxylic 1 : 1 complexes, are formed in which the carboxyl group is bidentately\\u000a coordinated to the metal atom. The logarithmic stability constants of these complexes regarding the reaction of the uranyl\\u000a ion with the single charged

  15. Uranyl carboxyphosphonates that incorporate Cd(II)

    SciTech Connect

    Alsobrook, Andrea N. [Department of Civil Engineering and Geological Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Alekseev, Evgeny V.; Depmeier, Wulf [Institut fuer Geowissenschaften, Universitaet zu Kiel, 24118 Kiel (Germany); Albrecht-Schmitt, Thomas E., E-mail: talbrec1@nd.ed [Department of Civil Engineering and Geological Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States)

    2011-05-15

    The hydrothermal treatment of UO{sub 3}, Cd(CH{sub 3}CO{sub 2}){sub 2}.2H{sub 2}O, and triethyl phosphonoacetate results in the formation of Cd{sub 2}[(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 3}O{sub 3}(OH)(H{sub 2}O){sub 2}].16H{sub 2}O (CdUPAA-1), [Cd{sub 3}(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 6}(H{sub 2}O){sub 13}].6H{sub 2}O (CdUPAA-2), and Cd(H{sub 2}O){sub 2}[(UO{sub 2})(PO{sub 3}CH{sub 2}CO{sub 2})(H{sub 2}O)]{sub 2} (CdUPAA-3). CdUPAA-1 adopts a cubic three-dimensional structure constructed from planar uranyl oxide clusters containing both UO{sub 7} pentagonal bipyramids and UO{sub 8} hexagonal bipyramids that are linked by Cd(II) cations and phosphonoacetate to yield large cavities approximately 16 A across that are filled with disordered water molecules. CdUPAA-2 forms a rhombohedral three-dimensional channel structure that is assembled from UO{sub 7} pentagonal bipyramids that are bridged by phosphonoacetate. CdUPAA-3 is layered with the hydrated Cd(II) cations incorporated directly into the layers linking one-dimensional uranyl phosphonate substructures together. In this structure, there are complex networks of hydrogen bonds that exist within the sheets, and also stitch the sheets together. -- Graphical abstract: A view of part of the cubic structure of Cd{sub 2}[(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 3}O{sub 3}(OH)(H{sub 2}O){sub 2}].16H{sub 2}O. Display Omitted highlights: > High symmetry uranyl compounds. > Three-dimensional structures. > Porous materials. > Heterobimetallic compounds.

  16. Slow magnetic relaxation in mononuclear seven-coordinate cobalt(ii) complexes with easy plane anisotropy.

    PubMed

    Chen, Lei; Chen, Shu-Yang; Sun, Yi-Chen; Guo, Yu-Mei; Yu, Lu; Chen, Xue-Tai; Wang, Zhenxing; Ouyang, Z W; Song, You; Xue, Zi-Ling

    2015-07-01

    Two mononuclear seven-coordinate cobalt(ii) complexes [Co(L)3(NO3)2] (L = 4-tert-butylpyridine, 1; L = isoquinoline, 2) were prepared and structurally analyzed by single-crystal X-ray crystallography. The coordination spheres of 1 and 2 exhibit distorted pentagonal bipyramid geometry. Analysis of their direct-current magnetic data reveals the existence of easy plane anisotropy (D > 0) with a small transverse anisotropy (E), which was further confirmed by high-field electron paramagnetic resonance (HFEPR) spectroscopy. Field-induced slow magnetic relaxations were observed under the applied dc field in complexes 1 and 2 by alternating-current magnetic susceptibility measurements. Importantly, these complexes are new instances of mononuclear high-coordinate cobalt(ii)-based single-molecule magnets. PMID:26027953

  17. Polar Coordinates and Multiplication In the last chapter we wrote complex numbers in the form x + iy where x

    E-print Network

    Wortman, Kevin

    Polar Coordinates and Multiplication In the last chapter we wrote complex numbers in the form x + iy where x and y are real numbers. We can think of this as writing complex numbers using Cartesian coordinates. Every complex number is the sum of a number on the real axis and a number on the imaginary axis

  18. Optical apparatus and method for sensing uranyl

    DOEpatents

    Baylor, L.C.; Buchanan, B.R.

    1994-01-01

    An optical sensing device for uranyl and other substances, a method for making an optical sensing device and a method for chemically binding uranyl and other indicators to glass, quartz, cellulose and similar substrates. The indicator, such as arsenazo III, is immobilized on the substrate using a chemical binding process. The immobilized arsenazo III causes uranyl from a fluid sample to bind irreversibly to the substrate at its active sites, thus causing absorption of a portion of light transmitted through the substrate. Determination of the amount of light absorbed, using conventional means, yields the concentration of uranyl present in the sample fluid. The binding of uranyl on the substrate can be reversed by subsequent exposure of the substrate to a solution of 2,6-pyridinedicarboxylic acid. The chemical binding process is suitable for similarly binding other indicators, such as bromocresol green.

  19. Attributes of advanced practice registered nurse care coordination for children with medical complexity.

    PubMed

    Cady, Rhonda G; Kelly, Anne M; Finkelstein, Stanley M; Looman, Wendy S; Garwick, Ann W

    2014-01-01

    Care coordination is an essential component of the pediatric health care home. This study investigated the attributes of relationship-based advanced practice registered nurse care coordination for children with medical complexity enrolled in a tertiary hospital-based health care home. Retrospective review of 2,628 care coordination episodes conducted by telehealth over a consecutive 3-year time period for 27 children indicated that parents initiated the majority of episodes and the most frequent reason was acute and chronic condition management. During this period, care coordination episodes tripled, with a significant increase (p < .001) between years 1 and 2. The increased episodes could explainpreviously reported reductions in hospitalizations for this group of children. Descriptive analysis of a program-specific survey showed that parents valued having a single place to call and assistance in managing their child's complex needs. The advanced practice registered nurse care coordination model has potential for changing the health management processes for children with medical complexity. PMID:23988611

  20. Coordination chemistry, thermodynamics and DFT calculations of copper(II) NNOS Schiff base complexes.

    PubMed

    Esmaielzadeh, Sheida; Azimian, Leila; Shekoohi, Khadijeh; Mohammadi, Khosro

    2014-12-10

    Synthesis, magnetic and spectroscopy techniques are described for five copper(II) containing tetradentate Schiff bases are synthesized from methyl-2-(N-2'-aminoethane), (1-methyl-2'-aminoethane), (3-aminopropylamino)cyclopentenedithiocarboxylate. Molar conductance and infrared spectral evidences indicate that the complexes are four-coordinate in which the Schiff bases are coordinated as NNOS ligands. Room temperature ?eff values for the complexes are 1.71-1.80B.M. corresponding to one unpaired electron respectively. The formation constants and free energies were measured spectrophotometrically, at constant ionic strength 0.1M (NaClO4), at 25?C in DMF solvent. Also, the DFT calculations were carried out to determine the structural and the geometrical properties of the complexes. The DFT results are further supported by the experimental formation constants of these complexes. PMID:24992917

  1. Chiral phosphites as ligands in asymmetric metal complex catalysis and synthesis of coordination compounds

    NASA Astrophysics Data System (ADS)

    Gavrilov, Konstantin N.; Bondarev, Oleg G.; Polosukhin, Aleksei I.

    2004-07-01

    The data published during the last five years on the application of chiral derivatives of phosphorous acid in coordination chemistry and enantioselective catalysis are summarised and discussed. The effect of the nature of these ligands on the structure of metal complexes and on the efficiency of catalytic organic syntheses is shown. Hydroformylation, hydrogenation, allylic substitution and conjugate addition catalysed by transition metal complexes with optically active phosphites and hydrophosphoranes are considered. The prospects for the development of this field of research are demonstrated.

  2. Cationcation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    SciTech Connect

    Balboni, Enrica [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2014-05-01

    The isotypical compounds (UO{sub 2}){sub 3}(WO{sub 6})(H{sub 2}O){sub 5} (1), Ag(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3} (2), K(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 4} (3), Rb(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3.5} (4), and Cs(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 3} (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), ?=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), ?=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), ?=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), ?=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), ?=101.661 (4). Compounds 15 are a framework of uranyl and tungsten polyhedra containing cationcation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 25, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO{sub 2}){sup 2+} uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO{sub 6} octahedra. Chains are linked through cationcation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [?1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 C. - Graphical abstract: Chains of uranium and tungsten polyhedra are connected into a three dimensional framework by cationcation interactions occurring between two symmetrically independent uranyl pentagonal bipyramids. Monovalent cations present in channels within the structure can be exchanged by room temperature or mild hydrothermal treatments. The framework of these compounds is robust to cation exchange and heat. (yellow polyhedra=uranium pentagonal bipyramids; blue polyhedra=tungsten octahedral, purple balls=K; yellow balls=Na; grey balls=Tl). - Highlights: Five isostructural uranyl tungstates compounds were synthesized hydrothermally. The structures consist of a chains of uranium and tungstate polyhedral. Chains are connected into a framework by cationcation interactions. Cation exchange does not alter the structural integrity of the compounds. Cation exchange was successful at room temperature and mild hydrothermal conditions.

  3. Complex-coordinate calculation of 1D(e) resonances using Hylleraas functions

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Ho, Y. K.

    1990-01-01

    The lowest 1D(e) resonances below the n = 2 and n = 3 thresholds are calculated using a method of complex-coordinate rotation. The results, obtained with the use of Hylleraas functions, are believed to be of high accuracy. This work should serve as a useful reference for other investigations.

  4. Fluorophore-linked zinc(II)dipicolylamine coordination complexes as sensors for

    E-print Network

    Smith, Bradley D.

    Fluorophore-linked zinc(II)dipicolylamine coordination complexes as sensors for phosphatidylserine and The Walther Center for Cancer Research, University of Notre Dame, 251 Nieuwland Hall, Notre Dame, IN 46556 with an attached NBD fluorophore are synthesized and evaluated as fluorescent sensors. The sensors do not respond

  5. English cum, a borrowed coordinator turned complex-compound marker Vincent Renner

    E-print Network

    Paris-Sud XI, Universit de

    1 English cum, a borrowed coordinator turned complex-compound marker Vincent Renner Abstract This article takes issue with the traditional view of English compounds such as governess-cum- piano-teacher, according to which the medial morpheme -cum- is insignificant. The study is first centered on the appearance

  6. Order Release and Product Mix Coordination in a Complex PCB Manufacturing Line with Batch Processors

    Microsoft Academic Search

    Rohit Bhatnagar; Pankaj Chandra; Richard Loulou; Jin Qiu

    1999-01-01

    In this paper, we study the role of order releases and product mix coordination in a complex manufacturing line with batch processors. We develop a planning methodology for synchronizing production in such manufacturing lines and discuss the decision-making process in the context of a PCB production environment at Northern Telecom's Fiberworld Division. The planning methodology includes developing mathematical programming models

  7. Influence of topology in the evolution of coordination in complex networks under information diffusion constraints

    NASA Astrophysics Data System (ADS)

    Kasthurirathna, Dharshana; Piraveenan, Mahendra; Harr, Michael

    2014-01-01

    In this paper, we study the influence of the topological structure of social systems on the evolution of coordination in them. We simulate a coordination game ("Stag-hunt") on four well-known classes of complex networks commonly used to model social systems, namely scale-free, small-world, random and hierarchical-modular, as well as on the well-mixed model. Our particular focus is on understanding the impact of information diffusion on coordination, and how this impact varies according to the topology of the social system. We demonstrate that while time-lags and noise in the information about relative payoffs affect the emergence of coordination in all social systems, some topologies are markedly more resilient than others to these effects. We also show that, while non-coordination may be a better strategy in a society where people do not have information about the payoffs of others, coordination will quickly emerge as the better strategy when people get this information about others, even with noise and time lags. Societies with the so-called small-world structure are most conducive to the emergence of coordination, despite limitations in information propagation, while societies with scale-free topologies are most sensitive to noise and time-lags in information diffusion. Surprisingly, in all topologies, it is not the highest connected people (hubs), but the slightly less connected people (provincial hubs) who first adopt coordination. Our findings confirm that the evolution of coordination in social systems depends heavily on the underlying social network structure.

  8. Chitosan-Copper (II) complex as antibacterial agent: synthesis, characterization and coordinating bond- activity correlation study

    NASA Astrophysics Data System (ADS)

    Mekahlia, S.; Bouzid, B.

    2009-11-01

    The antimicrobial activity of chitosan is unstable and sensitive to many factors such as molecular weight. Recent investigations showed that low molecular weight chitosan exhibited strong bactericidal activities compared to chitosan with high molecular weight. Since chitosan degradation can be caused by the coordinating bond, we attempt to synthesize and characterize the chitosan-Cu (II) complex, and thereafter study the coordinating bond effect on its antibacterial activity against Salmonella enteritidis. Seven chitosan-copper complexes with different copper contents were prepared and characterized by FT-IR, UV-vis, XRD and atomic absorption spectrophotometry (AAS). Results indicated that for chitosan-Cu (II) complexes with molar ratio close to 1:1, the inhibition rate reached 100%.

  9. Cation-cation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    NASA Astrophysics Data System (ADS)

    Balboni, Enrica; Burns, Peter C.

    2014-05-01

    The isotypical compounds (UO2)3(WO6)(H2O)5 (1), Ag(UO2)3(WO6)(OH)(H2O)3 (2), K(UO2)3(WO6)OH(H2O)4 (3), Rb(UO2)3(WO6)(OH)(H2O)3.5 (4), and Cs(UO2)3(WO6)OH(H2O)3 (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), ?=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), ?=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), ?=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), ?=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), ?=101.661 (4). Compounds 1-5 are a framework of uranyl and tungsten polyhedra containing cation-cation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 2-5, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO2)2+ uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO6 octahedra. Chains are linked through cation-cation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [-1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 C.

  10. Sorption of uranyl ions on titanium oxide studied by ATR-IR spectroscopy.

    PubMed

    Lefvre, G; Kneppers, J; Fdoroff, M

    2008-11-01

    ATR-IR spectroscopy was used to study the sorption of uranyl ions (10(-4) M) onto titanium oxide (mixture of rutile and anatase). A circulation setup, filled with a solution in D(2)O, allowed recording of the evolution of the antisymmetric O=U=O stretching of uranyl species onto titanium oxide particles deposited on the ATR crystal. The band centered at 915 cm(-1) has been decomposed in two Gaussian peaks at 920 and 905 cm(-1). From these values, and the observation that the ratio of the areas of the two peaks vs pH was constant, we have proposed that uranyl sorption on titanium oxide in the pH range 4-7 leads to the formation of one surface complex where uranium atoms have two different chemical environments. A trimer surface complex linked by two uranium atoms to the titanium oxide surface would be consistent with this interpretation. PMID:18760420

  11. Zinc(II)-Coordination Complexes as Membrane Active Fluorescent Probes and Antibiotics

    PubMed Central

    DiVittorio, Kristy M.; Leevy, W. Matthew; ONeil, Edward J.; Johnson, James R.; Vakulenko, Sergei; Morris, Joshua D.; Rosek, Kristine D.; Serazin, Nathan; Hilkert, Sarah; Hurley, Scott; Marquez, Manuel; Smith, Bradley D.

    2010-01-01

    Molecular probes with zinc(II)-(2,2-dipicolylamine) coordination complexes associate with oxyanions in aqueous solution and target biomembranes that contain anionic phospholipids. This study examines a new series of coordination complexes with 2,6-bis(zinc(II)-dipicolylamine) phenoxide as the molecular recognition unit. Two lipophilic analogues are observed to partition into the membranes of zwitterionic and anionic vesicles and induce the transport of phospholipids and hydrophilic anions (carboxyfluorescein). These lipophilic zinc complexes are moderately toxic to mammalian cells. A more hydrophilic analogue does not exhibit mammalian cell toxicity (LD50 >50 g/mL), but it is highly active against the Gram-positive bacteria Staphylococcus aureus (MIC of 1 g/mL). Furthermore, it is active against clinically important S. aureus strains that are resistant to various antibiotics including vancomycin and oxacillin. The antibiotic action is attributed to its ability to depolarize the bacterial cell membrane. The intense bacterial staining exhibited by a fluorescent conjugate suggests that this family of zinc coordination complexes can be used as molecular probes for the detection and imaging of bacteria. PMID:18076009

  12. Interactions of 1-methylimidazole with UO2(CH3CO2)2 and UO2(NO3)2: structural, spectroscopic, and theoretical evidence for imidazole binding to the uranyl ion.

    PubMed

    Gutowski, Keith E; Cocalia, Violina A; Griffin, Scott T; Bridges, Nicholas J; Dixon, David A; Rogers, Robin D

    2007-01-24

    The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO2(Ac)2 (Ac = CH3CO2) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H2O binding to both UO2(Ac)2 and UO2(NO3)2. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H2O and Meimid ligands to UO2R2 (R = Ac, NO3). For both UO2(NO3)2 and UO2(Ac)2, the displacement of H2O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions. PMID:17227015

  13. Coordination complex of dipicolinato cobalt(III) complex cation and anion

    Microsoft Academic Search

    Babulal Das; Kaushik Ghosh; Jubaraj B. Baruah

    2011-01-01

    Two examples of a new class of high oxidation state complexes having complex anion and complex cation of cobalt(III) are presented. The complexes [CoL(py)3][CoL2]??2H2O (1) and [CoL(im)3][CoL2]??H2O (2) (where L?=?dipicolinato anion, py?=?pyridine and im?=?imidazole) are characterized by determining their crystal structures and studying their properties in solution. The complex anionic and cationic parts form layered structures through hydrogen-bond interactions with

  14. Prebiotic coordination chemistry: The potential role of transition-metal complexes in the chemical evolution

    NASA Technical Reports Server (NTRS)

    Beck, M.

    1979-01-01

    In approaching the extremely involved and complex problem of the origin of life, consideration of the coordination chemistry appeared not only as a possibility but as a necessity. The first model experiments appear to be promising because of prebiotic-type synthesis by means of transition-metal complexes. It is especially significant that in some instances various types of vitally important substances (nucleic bases, amino acids) are formed simultaneously. There is ground to hope that systematic studies in this field will clarify the role of transition-metal complexes in the organizatorial phase of chemical evolution. It is obvious that researchers working in the fields of the chemistry of cyano and carbonyl complexes, and of the catalytic effect of transition-metal complexes are best suited to study these aspects of the attractive and interesting problem of the origin of life.

  15. Coordination properties of hydralazine Schiff base. Synthesis and equilibrium studies of some metal ion complexes

    NASA Astrophysics Data System (ADS)

    Shoukry, Azza A.; Shoukry, Mohamed M.

    2008-08-01

    In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and 1H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies.

  16. A Rac1-GDP Trimer Complex Binds Zinc with Tetrahedral and Octahedral Coordination, Displacing Magnesium

    SciTech Connect

    Prehna,G.; Stebbins, E.

    2007-01-01

    The Rho family of small GTPases represent well characterized signaling molecules that regulate many cellular functions such as actin cytoskeletal arrangement and the cell cycle by acting as molecular switches. A Rac1-GDP-Zn complex has been crystallized in space group P3{sub 2}21 and its crystal structure has been solved at 1.9 {angstrom} resolution. These trigonal crystals reveal the unexpected ability of Rac1 to coordinate Zn atoms in a tetrahedral fashion by use of its biologically relevant switch I and switch II regions. Upon coordination of zinc, the switch I region is stabilized in the GDP-bound conformation and contributes to a Rac1 trimer in the asymmetric unit. Zinc coordination causes switch II to adopt a novel conformation with a symmetry-related molecule. Additionally, zinc was found to displace magnesium from its octahedral coordination at switch I, although GDP binding remained stable. This structure represents the first reported Rac1-GDP-Zn complex, which further underscores the conformational flexibility and versatility of the small GTPase switch regions.

  17. A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium

    SciTech Connect

    Prehna, G.; Stebbins, C

    2007-01-01

    The Rho family of small GTPases represent well characterized signaling molecules that regulate many cellular functions such as actin cytoskeletal arrangement and the cell cycle by acting as molecular switches. A Rac1-GDP-Zn complex has been crystallized in space group P3221 and its crystal structure has been solved at 1.9 {angstrom} resolution. These trigonal crystals reveal the unexpected ability of Rac1 to coordinate Zn atoms in a tetrahedral fashion by use of its biologically relevant switch I and switch II regions. Upon coordination of zinc, the switch I region is stabilized in the GDP-bound conformation and contributes to a Rac1 trimer in the asymmetric unit. Zinc coordination causes switch II to adopt a novel conformation with a symmetry-related molecule. Additionally, zinc was found to displace magnesium from its octahedral coordination at switch I, although GDP binding remained stable. This structure represents the first reported Rac1-GDP-Zn complex, which further underscores the conformational flexibility and versatility of the small GTPase switch regions.

  18. Uranyl fluoride luminescence in acidic aqueous solutions

    SciTech Connect

    Beitz, J.V.; Williams, C.W. [Argonne National Lab., IL (United States). Chemistry Div.

    1996-08-01

    Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269 {+-} 0.006 ms, was observed from uranyl in 1 M HF + 1 M HClO{sub 4} at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to UO{sub 2}F{sub 2}. Studies on the effect of added LiNO{sub 3} or Na{sub 2}WO{sub 4}{center_dot}2H{sub 2}O showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the UF{sub 6} content of WF{sub 6} gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure WF{sub 6}.

  19. Combination of optically measured coordinates and displacements for quantitative investigation of complex objects

    Microsoft Academic Search

    Peter Andrae; Manfred-Andreas Beeck; Werner P. Jueptner; Werner Nadeborn; Wolfgang Osten

    1996-01-01

    Holographic interferometry makes it possible to measure high precision displacement data in the range of the wavelength of the used laser light. However, the determination of 3D- displacement vectors of objects with complex surfaces requires the measurement of 3D-object coordinates not only to consider local sensitivities but to distinguish between in-plane deformation, i.e. strains, and out-of-plane components, i.e. shears, too.

  20. Addressing complexity, coordination, and automation in software development with the KBSA\\/ADM

    Microsoft Academic Search

    Kevin M. Benner

    1996-01-01

    This paper describes how the Knowledge-Based Software Assistant\\/Advanced Development Model brings together technologies from the KBSE domain along with more traditional software engineering practices in order to address the pervasive software development problems associated with complexity coordination, and automation. This paper describes how the KBSA\\/ADM realizes and refines the vision of Rome Laboratory's Knowledge-Based Software Assistant research program. The most

  1. Universal spectrochemical series of six-coordinate octahedral metal complexes for modifying the ligand field splitting.

    PubMed

    Ishii, Tomohiko; Tsuboi, Shino; Sakane, Genta; Yamashita, Masahiro; Breedlove, Brian K

    2009-01-28

    We studied a novel universal spectrochemical series of six-coordinated octahedral 3d transition metal complexes, which can be used for any combination of central metal atom and ligand molecules. A two dimensional spectrochemical series could be used to estimate the ligand field splitting energy of not only known compounds but also the unknown compounds. Therefore, it should be possible to control the physical properties, such as the electronic and magnetic properties and the optical phenomena of octahedral transition metal complexes by modifying the ligand field splitting. PMID:19378561

  2. Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units

    NASA Astrophysics Data System (ADS)

    Wylie, Ernest M.; Dawes, Colleen M.; Burns, Peter C.

    2012-12-01

    Single crystals of Zn4(OH)2[(UO2)(PO4)2(OH)2(H2O)] (UZnP), Cs[(UO2)(HPO4)NO3] (UCsP), and In3[(UO2)2(PO4)4OH(H2O)6].2H2O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) ; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) , ?=72.974(2), ?=74.261(2), ?=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) ?=101.289(1), ?=114.642(1), ?=99.203(2). The U6+ cations are present as (UO2)2+ uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry.

  3. Temperature programmed decomposition of uranyl nitrate hexahydrate

    NASA Astrophysics Data System (ADS)

    Dash, S.; Kamruddin, M.; Bera, Santanu; Ajikumar, P. K.; Tyagi, A. K.; Narasimhan, S. V.; Raj, Baldev

    1999-01-01

    Temperature programmed decomposition (TPD) of uranyl nitrate hexahydrate has been studied using evolved gas analysis mass spectrometry (EGA-MS) in the temperature range 300-1400 K. Thermogravimetric (TGA) investigations were performed in the temperature range 300-1100 K. An attempt has been made to resolve the complexity of decomposition behaviour through suitable comparison of TGA and EGA-MS data. Kinetic control regimes for various decomposition stages could be deduced from EGA-MS data. The corresponding activation energies and frequency factors were also evaluated. Kinetics based on random nucleation and diffusion was found to be rate controlling. The residue left over after each decomposition stage was analysed by XRD and XPS to determine structure and composition. The ultimate product was found to be a mixture of UO 3H 1.17 and U 3O 8: the former being a topotactic hydrogen spill over compound of UO 3. Complete conversion of this residue to U 3O 8 was noticed during ion beam exposure of the residue which was performed in the course of XPS investigations.

  4. Removalof uranyl ions from wastewaters using cellulose and modified cellulosematerials

    Microsoft Academic Search

    D. Bontea; C. Mita; D. Humelnicu

    2006-01-01

    SummaryThree\\u000a silylcellulosic derivatives with different substitution degree were examined as\\u000a sorbents for uranyl ions. The adsorption rate and capacity of cellulose and\\u000a modified cellulose were investigated in aqueous media, at various pH and\\u000a temperature values. The polymer - metal complexes of UO22+\\u000a were characterized by infrared and electronic spectra, and thermogravimetry.\\u000a The thermal behavior of cellulose (C), trimethylsilyl - cellulose

  5. The Cbp3Cbp6 complex coordinates cytochrome b synthesis with bc1 complex assembly in yeast mitochondria

    PubMed Central

    Gruschke, Steffi; Rmpler, Katharina; Hildenbeutel, Markus; Kehrein, Kirsten; Khl, Inge; Bonnefoy, Nathalie

    2012-01-01

    Respiratory chain complexes in mitochondria are assembled from subunits derived from two genetic systems. For example, the bc1 complex consists of nine nuclear encoded subunits and the mitochondrially encoded subunit cytochrome b. We recently showed that the Cbp3Cbp6 complex has a dual function for biogenesis of cytochrome b: it is both required for efficient synthesis of cytochrome b and for protection of the newly synthesized protein from proteolysis. Here, we report that Cbp3Cbp6 also coordinates cytochrome b synthesis with bc1 complex assembly. We show that newly synthesized cytochrome b assembled through a series of four assembly intermediates. Blocking assembly at early and intermediate steps resulted in sequestration of Cbp3Cbp6 in a cytochrome bcontaining complex, thereby making Cbp3Cbp6 unavailable for cytochrome b synthesis and thus reducing overall cytochrome b levels. This feedback loop regulates protein synthesis at the inner mitochondrial membrane by directly monitoring the efficiency of bc1 complex assembly. PMID:23007649

  6. Highly valence-diversified binuclear uranium complexes of a schiff-base polypyrrolic macrocycle: prediction of unusual structures, electronic properties, and formation reactions.

    PubMed

    Yao, Jun; Zheng, Xiu-Jun; Pan, Qing-Jiang; Schreckenbach, Georg

    2015-06-01

    On the basis of relativistic density functional theory calculations, homo- and heterovalent binuclear uranium complexes of a polypyrrolic macrocycle in a U-O-U bridging fashion have been investigated. These complexes show a variety of oxidation states for uranium ranging from III to VI, which have been confirmed by the calculated electron-spin density on each metal center. An equatorially 5-fold uranyl coordination mode is suitable for hexavalent uranium complexes, while silylation of the uranyl oxo is favored by pentavalent uranium. Uranyl oxo ligands are not required anymore for the coordination environment of tetra- and trivalent uranium because of their replacement by strong donors such as tetrahydrofuran and iodine. Optimization of binuclear U(VI)-U(III) complexes with various coordinating modes of U(III), donor numbers, and donor types reveals that 0.5-1.0 electron has been transferred from U(III) to U(VI). Consequently, U(V)-U(IV) complexes are more favorable. Electronic structures and formation reactions of several representative uranium complexes were calculated. For example, a 5f-based ?(U-U) bonding orbital is found in the diuranium(IV) complex, rationalizing the fact that it shows the shortest U-U distance (3.82 ) among the studied binuclear complexes. PMID:25955709

  7. Polymeric coordination complexes based on cobalt, nickel, and ruthenium that exhibit synergistic thermal properties

    SciTech Connect

    Belfoire, L.A. [Colorado State Univ., Fort Collins, CO (United States)

    1993-12-31

    d-Block metal-containing polymer blends which form coordination complexes are the focus of this research. The model compounds are cobalt chloride hexahydrate, nickel acetate tetrahydrate, and diclorotricarbonylruthenium(II) dimer. The ligand is poly(4-vinylpyridine), P4VP, or copolymers that contain 4-vinylpyridine repeat units. Thermal analysis via differential scanning calorimetry suggests that the glass transition temperature of the polymeric ligand(s) is enhanced by the d-block metal salt in binary and ternary blends. The cobalt and nickel salts function as transition-metal compatibilizers for two immiscible copolymers of styrene with 4-vinylpyridine and butyl methaacrylate with 4-vinylpyridine. At the molecular level, Fourier transform infrared spectroscopy of P4VP-ruthenium precipitates reveals that the pyridine nitrogen lone pair coordinates to the metal center and strengthens ruthenium-carbonyl bonds in the polymeric complex. A thermodynamic interpretation of ligand field stabilization enhancement of the glass transition temperature, particularly when coordination crosslinks are present.

  8. Coordination chemistry and functionalization of white phosphorus via transition metal complexes.

    PubMed

    Peruzzini, Maurizio; Gonsalvi, Luca; Romerosa, Antonio

    2005-12-01

    The chemistry of phosphorus is nowadays rivaling that of carbon in terms of complexity and diversity. This tutorial review highlights the state-of-the-art in the field of metal-mediated activation and functionalization of white phosphorus. Particular attention is given to an illustration of the coordination abilities of the intact molecule as well as the disaggregating and reaggregating metal-mediated processes resulting in different polyphosphorus ligands from P(1) to P(12). The metal-promoted P-C and P-H bond forming processes are also reviewed showing that an ecoefficient catalytic protocol for transforming P(4) into high value organophosphorus compounds is a concrete possibility for chemical companies. This tutorial review deals with the activation and functionalization of white phosphorus in the coordination sphere of transition metal complexes. Particular attention is given to the coordination abilities of the intact molecule as well as to the disaggregating and reaggregating metal-mediated processes yielding various polyphosphorus ligands from P(1) to P(12). The metal-promoted processes for P-C and P-H bond formation are also reviewed showing that an ecoefficient catalytic protocol for transforming P(4) into high value organophosphorus compounds offers good opportunities for chemical companies. PMID:16284670

  9. A Codeposition Route to CuI-Pyridine Coordination Complexes for OLEDs

    PubMed Central

    Liu, Zhiwei; Qayyum, Munzarin F.; Wu, Chao; Whited, Matthew T.; Djurovich, Peter I.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.; Thompson, Mark E.

    2011-01-01

    We demonstrate a new approach to utilize copper(I) iodide coordination complexes as emissive layers in organic light-emitting diodes (OLEDs), by in situ codeposition of copper(I) iodide and 3,5-bis(carbazol-9-yl)pyridine (mCPy). With a simple three-layer device structure, pure green electroluminescence at 530 nm from a copper(I) complex was observed. Maximum luminance and external quantum efficiency (EQE) of 9700 cd/m2 and 4.4% have been achieved, respectively. The luminescent species has been identified as [CuI(mCPy)2]2 based on photophysical studies of model complexes and X-ray absorption spectroscopy (XAS). PMID:21366248

  10. Three new silver uranyl diphosphonates: structures and properties.

    PubMed

    Nelson, Anna-Gay D; Rak, Zsolt; Albrecht-Schmitt, Thomas E; Becker, Udo; Ewing, Rodney C

    2014-03-17

    The hydrothermal reaction of uranium trioxide and methylenediphosphonic acid in the presence of silver nitrate resulted in the formation of three new uranyl coordination polymers: AgUO2[CH2(PO3)(PO3H)] (Ag-1), [Ag2(H2O)1.5]{(UO2)2[CH2(PO3)2]F2}(H2O)0.5 (Ag-2), and Ag2UO2[CH2(PO3)2] (Ag-3). All consist of uranyl pentagonal bipyramids that form two-dimensional layered structures. Ag-1 and Ag-3 possess the same structural building unit, but the structures are different; Ag-3 is formed through edge-sharing of F atoms to form UO5F2 dimers. The pH and silver cation have significant effects on the structure that is synthesized. Raman spectra of single crystals of Ag-1, Ag-2, and Ag-3 reveal v1 UO2(2+) symmetric stretches of 816 and 829, 822, and 802 cm(-1), respectively. Electronic structure calculations were performed using the projector augmented wave (PAW) method with density functional theory (DFT) to gain insight into the nature of bonding and electronic characteristics of the synthesized compounds. Herein, we report the syntheses, crystal structures, Raman spectroscopy, and luminescent behavior of these three compounds. PMID:24524249

  11. Challenging conventional f-element separation chemistry--reversing uranyl(VI)/lanthanide(III) solvent extraction selectivity.

    PubMed

    Hawkins, C A; Bustillos, C G; Copping, R; Scott, B L; May, I; Nilsson, M

    2014-08-14

    The water soluble tetradentate Schiff base, N,N'-bis(5-sulfonatosalicylidene)-diaminoethane (H2salen-SO3), will readily coordinate to the uranyl(VI) cation, but not to the same extent to trivalent lanthanide cations. This allows for the reversal of conventional solvent extraction properties and opens the possibility for novel separation processes. PMID:24958394

  12. Engineering a uranyl specific binding protein from NikR.

    SciTech Connect

    Wegner, S. V.; Boyaci, H.; Chen, H.; Jensen, M. P.; He, C. (Chemical Sciences and Engineering Division); ( PSC-USR); (Univ. of Chicago)

    2009-03-16

    The first uranyl-selective DNA-binding protein is designed using the E. coli nickel(II)-responsive protein NikR as the template. The resulting NikR? protein binds uranyl (see picture) with a dissociation constant Kd=53?nM and selectively binds to DNA in the presence of uranyl.

  13. An europium(III) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction.

    PubMed

    Antonio, Mark R; McAlister, Daniel R; Horwitz, E Philip

    2015-01-14

    The synthesis, stoichiometry, and structural characterization of a homoleptic, cationic europium(III) complex with three neutral tetraalkyldiglycolamide ligands are reported. The tri(bismuth tetrachloride)tris(N,N,N',N'-tetra-n-octyldiglycolamide)Eu salt, [Eu(TODGA)3][(BiCl4)3] obtained from methanol was examined by Eu L3-edge X-ray absorption spectroscopy (XAS) to reveal an inner-sphere coordination of Eu(3+) that arises from 9 O atoms and two next-nearest coordination spheres that arise from 6 carbon atoms each. A structural model is proposed in which each TODGA ligand with its O=Ca-Cb-O-Cb-Ca=O backbone acts as a tridentate O donor, where the two carbonyl O atoms and the one ether O atom bond to Eu(3+). Given the structural rigidity of the tridentate coordination motif in [Eu(TODGA)3](3+) with six 5-membered chelate rings, the six Eu-Ca and six Eu-Cb interactions are readily resolved in the EXAFS (extended X-ray absorption fine structure) spectrum. The three charge balancing [BiCl4](-) anions are beyond the cationic [Eu(TODGA)3](3+) cluster in an outer sphere environment that is too distant to be detected by XAS. Despite their sizeable length and propensity for entanglement, the four n-octyl groups of each TODGA (for a total of twelve) do not perturb the Eu(3+) coordination environment over that seen from previously reported single-crystal structures of tripositive lanthanide (Ln(3+)) complexes with tetraalkyldiglycolamide ligands (of the same 1:3 metal-to-ligand ratio stoichiometry) but having shorter i-propyl and i-butyl groups. The present results set the foundation for understanding advanced solvent extraction processes for the separation of the minor, tripositive actinides (Am, Cm) from the Ln(3+) ions in terms of the local structure of Eu(3+) in a solid state coordination complex with TODGA. PMID:25310364

  14. Using antibodies to perturb the coordination sphere of a transition metal complex.

    PubMed

    Ghosh, P; Shabat, D; Kumar, S; Sinha, S C; Grynszpan, F; Li, J; Noodleman, L; Keinan, E

    1996-07-25

    Metal ions in the active sites of many metalloenzymes exhibit distinctive spectral and chemical features which are different from those of small inorganic complexes. These features are the result of the unusual geometric and electronic constraints that are imposed on the metal ion within the protein environment. Much effort has been invested to try to mimic this feature of metalloenzymes in synthetic systems, but this remains a formidable task. Here we show that one of the key lessons learned from the science of catalytic antibodies--that binding energy can be converted into chemical energy--can be exploited to 'fine-tune' the physicochemical properties of a metal complex. We show that an antibody's binding site can reversibly perturb the coordination geometry of a metal ion, and can stabilize a high-energy coordinated species. Specifically, antibodies designed to bind the organosilicon compound 1 also bind the geometrically similar Cu(I) complex 2. However, the antibody binds a slightly compressed form of 2, which is closer in size to 1. This distortion is manifested by a spectral shift--an 'immunochromic' effect. PMID:8684461

  15. New Routes to Low-Coordinate Iron Hydride Complexes: The Binuclear Oxidative Addition of H2

    PubMed Central

    Dugan, Thomas R.; Holland, Patrick L.

    2009-01-01

    The oxidative addition and reductive elimination reactions of H2 on unsaturated transition-metal complexes are crucial in utilizing this important molecule. Both biological and man-made iron catalysts use iron to perform H2 transformations, and highly unsaturated iron complexes in unusual geometries (tetrahedral and trigonal planar) are anticipated to give unusual or novel reactions. In this paper, two new synthetic routes to the low-coordinate iron hydride complex [LtBuFe(?-H)]2 are reported. Et3SiH was used as the hydride source in one route by taking advantage of the silaphilicity of the fluoride ligand in three-coordinate LtBuFeF. The other synthetic method proceeded through the binuclear oxidative addition of H2 or D2 to a putative Fe(I) intermediate. Deuteration was verified through reduction of an alkyne and release of the deuterated alkene product. Mssbauer spectra of [LtBuFe(?-H)]2 indicate that the samples are pure, and that the iron(II) centers are high-spin. PMID:20161197

  16. Talking about the institutional complexity of the integrated rehabilitation systemthe importance of coordination

    PubMed Central

    Miettinen, Sari; Ashorn, Ulla; Lehto, Juhani

    2013-01-01

    Rehabilitation in Finland is a good example of functions divided among several welfare sectors, such as health services and social services. The rehabilitation system in Finland is a complex one and there have been many efforts to create a coordinated entity. The purpose of this study is to open up a complex welfare system at the upper policy level and to understand the meaning of coordination at the level of service delivery. We shed light in particular on the national rehabilitation policy in Finland and how the policy has tried to overcome the negative effects of institutional complexity. In this study we used qualitative content analysis and frame analysis. As a result we identified four different welfare state frames with distinct features of policy problems, policy alternatives and institutional failure. The rehabilitation policy in Finland seems to be divided into different components which may cause problems at the level of service delivery and thus in the integration of services. Bringing these components together could at policy level enable a shared view of the rights of different population groups, effective management of integration at the level of service delivery and also an opportunity for change throughout the rehabilitation system. PMID:23687479

  17. An interesting coordination complex formed between the azo dye Sudan Red G and cobalt ion

    NASA Astrophysics Data System (ADS)

    Garcia, Humberto C.; Ferreira, Gilson Rodrigues; de Oliveira, Luiz Fernando C.

    2014-03-01

    In this study, the synthesis, spectroscopic analysis (Raman and infrared) and crystal structure of compound denominated [Co(SRG)2]CH3CH2OH have been investigated, were SRG is 1-(2-methoxyphenyl-azo)-2-naphthol or simply Sudan Red G and CH3CH2OH is one molecule of ethanol. The repeating unit is formed by the presence of an adduct complex constituted by two SRG ligands coordinated to the cobalt ion in a slightly distorted octahedral geometry. The other building block consists of a molecule of ethanol, which was used as the reaction solvent. The spectroscopic analysis provided important information related to coordination and formation of molecular complex through its mains bands. In the Raman spectrum the presence of marker bands as in at 1224 cm-1 ascribed to the binder SRG [?(NH) + ?(COC) + ?(CH) + ?(CC)] were displaced in the complex formed to 1232 cm-1 due to the loss of the proton from the azo group and the formation of a bond between the oxygen of the ether group with the metal ion. In the infrared spectrum the bands at 653/489 cm-1 and 622/528 cm-1 were attributed to [?(CoO) + ?CC)] and [?CoN + ?CC] characteristic of the metal-ligand bond.

  18. VO(2+)-hydroxyapatite complexes as models for vanadyl coordination to phosphate in bone.

    PubMed

    Dikanov, Sergei A; Liboiron, Barry D; Orvig, Chris

    2013-09-01

    We describe a 1D and 2D ESEEM investigation of VO(2+) adsorbed on hydroxyapatite (HA) at different concentrations and compare with VO(2+)-triphosphate (TPH) complexes studied previously in detail, in an effort to provide more insight into the structure of VO(2+)coordination in bone. Structures of this interaction are important because of the role of bone in the long-term storage of administered vanadium, and the likely role of bone in the steady-state release of vanadium leading to the chronic insulin-enhancing anti-diabetic effects of vanadyl complexes. Three similar sets of cross-peaks from phosphorus nuclei observed in the (31)P HYSCORE spectra of VO(2+)-HA, VO(2+)-TPH, and VO(2+)-bone suggest a common tridentate binding motif for triphosphate moieties to the vanadyl ion. The similarities between the systems present the possibility that in vivo vanadyl coordination in bone is relatively uniform. Experiments with HA samples containing different amounts of adsorbed VO(2+) demonstrate additional peculiarities of the ion-adsorbent interaction which can be expected in vivo. HYSCORE spectra of HA samples show varying relative intensities of (31)P lines from phosphate ligands and (1)H lines, especially lines from protons of coordinated water molecules. This result suggests that the number of equatorial phosphate ligands in HA could be different depending on the water content of the sample and the VO(2+) concentration; complexes of different structure probably contribute to the spectra of VO(2+)-HA. Similar behavior can be also expected in vivo during VO(2+) accumulation in bones. PMID:24829511

  19. Lipid bilayer interactions of Eu(III) tris-?-diketonato coordination complex

    NASA Astrophysics Data System (ADS)

    Yudintsev, Andrey; Trusova, Valeriya; Gorbenko, Galyna; Deligeorgiev, Todor; Vasilev, Aleksey; Gadjev, Nikolai

    2008-05-01

    Membrane-associating and bilayer-modifying properties of Eu(III) tris-?-diketonato coordination compound (LC) displaying anti-tumor activity were evaluated using absorption and fluorescence spectroscopy techniques. Quantifying the lipid-induced changes in LC absorbance in terms of partitioning formalism yielded the partition coefficient of (6.7 1.4) 10 3. Examination of LC effect on the structural state of PC bilayer with fluorescent probe pyrene revealed the ability of europium complex to increase membrane free volume, supposedly associated with bilayer disordering and increased rate of trans-gauche isomerization of acyl chains.

  20. Synthesis and equilibrium binding studies of cationic, two-coordinate gold(I) ?-alkyne complexes

    PubMed Central

    Brown, Timothy J.; Widenhoefer, Ross A.

    2013-01-01

    Reaction of a 1:1 mixture of (L)AuCl [L = P(t-Bu)2o-biphenyl or IPr] and AgSbF6 with internal alkynes led to isolation of the corresponding cationic, two-coordinate gold ?-alkyne complexes in ? 90% yield. Equilibrium binding studies show that the binding affinities of alkynes to gold(I) are strongly affected by the electron density of the alkyne and to a lesser extent on the steric bulk of the alkyne. These substituent effects on alkyne binding affinity are greater than are the differences between the inherent binding affinities of alkynes and alkenes to gold(I). PMID:24265509

  1. Indolocarbazole-based ligands for ladder-type four-coordinate boron complexes.

    PubMed

    Curiel, David; Ms-Montoya, Miriam; Usea, Laura; Espinosa, Arturo; Orenes, Ral A; Molina, Pedro

    2012-07-01

    A novel class of ?-conjugated systems, which combine the indolo[3,2-b]carbazole unit with the formation of four-coordinate boron complexes, is presented. The resulting conjugated compounds have a double-laddered structure that provides interesting optical and electrochemical properties. The wide absorption range, covering most of the visible spectrum, along with the narrowing of the HOMO-LUMO energy gap, due to the presence of diphenylboryl centers, reinforces the potential of these molecules within the area of organic electronics. PMID:22716949

  2. The DREAM complex: Master coordinator of cell cycle dependent gene expression

    PubMed Central

    Sadasivam, Subhashini; DeCaprio, James A.

    2014-01-01

    Preface The dimerization partner (DP), retinoblastoma (RB)-like, E2F and MuvB (DREAM) complex provides a previously unsuspected unifying role in the cell cycle by directly linking p130, p107, E2F, BMYB and FOXM1. DREAM mediates gene repression during G0 and coordinates periodic gene expression with peaks during G1/S and G2/M. Perturbations in DREAM regulation shift the balance from quiescence towards proliferation and contribute to increased mitotic gene expression levels frequently observed in cancers with poor prognosis. PMID:23842645

  3. Uranyl sorption onto gibbsite studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS).

    PubMed

    Baumann, Nils; Brendler, Vinzenz; Arnold, Thuro; Geipel, Gerhard; Bernhard, Gert

    2005-10-15

    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was combined with batch experiments to study the sorption of uranium(VI) onto gibbsite (gamma-Al(OH)3). The experiments were performed under ambient conditions in 0.1 M NaClO4 solution in the pH range from 5.0 to 8.5 using a total uranium concentration of 1x10(-5) M, and a solid concentration of 0.5 g/40 ml. Two uranyl surface species with fluorescence lifetimes of 330+/-115 and 5600+/-1640 ns, respectively, were identified. The first species was dominating the more acid pH region whereas the second one became gradually more prominent towards higher pH values. The fluorescence spectra of both adsorbed uranyl(VI) surface species were described with six characteristic fluorescence emission bands situated at 479.5+/-1.1, 497.4+/-0.8, 518.7+/-1.0, 541.6+/-0.7, 563.9+/-1.2, and 585.8+/-2.1 nm. The surface species with the short-lived fluorescence lifetime of 330 ns is attributed to a bidentate mononuclear inner-sphere surface complex in which the uranyl(VI) is bound to two reactive OH- groups at the broken edge linked to one Al. The second surface species with the significant longer fluorescence lifetime of 5600 ns was attributed to small sorbed clusters of polynuclear uranyl(VI) surface species. The longer fluorescence lifetime of the long-lived uranyl surface species at pH 8.5 is explained with the growing average size of the adsorbed polynuclear uranyl surface species. PMID:16129445

  4. Different Coordination Modes of a Tripod Phosphine in Gold(I) and Silver(I) Complexes

    PubMed Central

    Sevillano, P.; Habtemariam, A.; Parsons, S.; Sadler, P. J.

    1999-01-01

    The following gold(I) and silver(I) complexes of the tritertiary phosphine 1,1,1- tris(diphenylphosphinomethyl)ethane, tripod , have been synthesised: Au3(tripod)X3 [X = Cl(1), Br(2), I(3)]; [Au3(tripod)2Cl2]Cl (4); Au(tripod)X [X = Br(5), I(6)]; Ag3(tripod) (NO3)4 (7), Ag(tripod)NO3 (8). They were characterized by X-ray diffraction (complexes 2, 3 and 4), 31P NMR spectroscopy, electrospray and FAB mass spectrometry and infrared spectroscopy. Complexes 2 and 3 show a linear coordination geometry for Au(I), with relatively short Au-P bond distances. Complex 3 has a AuAu intramolecular distance of 3.326 A , while complex 2 had a short AuAu intermolecular interaction of 3.048 A . Complexes 4-6 were found by 31P NMR spectroscopy studies to contain a mixture of species in solution, one of which crystallised as [Au3(tripod|)2Cl2]Cl which was shown by X-ray diffraction to contain both tetrahedral and linear Au(I), the first example of a Au(I) complex containing such a mixture of geometries. The reaction of [Au3 (tripod)Cl3] (1) with tripod led successfully to the formation of [Au3(tripod|)2Cl2]+ and [Au3(tripod)2Cl3]+ and [Au3(tripod|)3Cl]2+. The silver(I) complexes, 7 and 8 appear to contain linear and tetrahedral Ag(I), respectively. PMID:18475895

  5. Utilization of IR spectral detailed analysis for coordination mode determination in novel Zn-cyclen-aminoacid complexes

    NASA Astrophysics Data System (ADS)

    Vargov, Z.; Almi, M.; Arabuli, L.; Gyryov, K.; Zele?k, V.; Kuchr, J.

    2011-02-01

    The infrared spectra, elemental and thermal (TG/DTG and DTA) analyses of novel [Zn(cyclen-? 4N 1,4,7,10)(HGly-? 2O,O')](ClO 4) 2 ( 1), and [Zn 2(cyclen-? 4N 1,4,7,10) 2(?-S-Ala-? 2N,O)](ClO 4) 32H 2O ( 2) complexes (cyclen - 1,4,7,10-tetraazacyclododecane) were recorded and analyzed in the relation to their structural peculiarities. IR spectral data indicate both mono- or bidentate coordination mode of a carboxylate group in the prepared complexes (at pH ? 9). The results indicate unusual bidentate carboxylate coordination mode (in complex ( 1)) toward to Zn 2+-cyclen unit. Therefore the crystal structure determination of the crystalline complex [Zn(cyclen-? 4N 1,4,7,10)(NO 3-? 2O,O')](NO 3) was attached in order to support the coordination mode assignment in complex ( 1).

  6. Mononuclear three-coordinate magnesium complexes of a highly sterically encumbered ?-diketiminate ligand.

    PubMed

    Arrowsmith, Merle; Maitland, Brant; Kociok-Khn, Gabriele; Stasch, Andreas; Jones, Cameron; Hill, Michael S

    2014-10-01

    The highly sterically encumbered chelating ?-diketiminate ligand, [HC{C(Me)N(2,6-CHPh2-4-MeC6H2)}2](-), (Ar)L(-), has been used to prepare a series of heteroleptic three-coordinate magnesium complexes. Both the bis(imine) and imine-enamine tautomers of the ligand precursor, (Ar)LH, as well as the diethyl ether adduct of the bromide complex [(Ar)LMgBr(OEt2)], the monomeric methyl complex [(Ar)LMgMe], the THF-solvated and unsolvated n-butylmagnesium complexes [(Ar)LMg(n)Bu(THF)] and [(Ar)LMg(n)Bu], and the 1-hexynyl analogue [(Ar)LMgC?C(n)Bu] have been crystallographically characterized. Both n-butylmagnesium complexes showed remarkable stability in air, both in the solid state and in solution. Single crystals of the highly sensitive magnesium hydride, [(Ar)LMgH], underwent partial hydrolysis by solid-state water diffusion to the isostructural hydroxide compound [(Ar)LMgOH]. PMID:25203490

  7. Nitrogen-rich compounds of the actinoids: dioxouranium(VI) 5,5'-azobis[tetrazolide] pentahydrate and its unusually small uranyl angle.

    PubMed

    Steinhauser, Georg; Giester, Gerald; Wagner, Christoph; Weinberger, Peter; Zachhuber, Bernhard; Ramer, Georg; Villa, Mario; Lendl, Bernhard

    2012-06-18

    Uranyl(VI) 5,5'-azobis[tetrazolide] pentahydrate was synthesized and characterized using X-ray crystallography, elemental analysis, UV/vis, MIR, FIR, and Raman spectroscopy. It is the second-most nitrogen rich compound of uranium (26.72 wt % N) and only the second structurally characterized uranium complex with a tetrazole ligand described in the literature. The compound's structure is characterized by an exceptionally small uranyl angle of 172.4(1), which provides information on the coordination properties of tetrazole ligands as they affect the donor's environment by strong steric and perhaps electrostatic repulsion. The compound showed luminescence under excitation with a near UV laser. The mean lifetime of its excited state was shorter than in the case of UO(2)(NO(3))(2)6H(2)O, indicating quenching by the ligand. Despite its high nitrogen content (and thus potentially explosive character), the title compound proved to be stable even under neutron radiation causing induced fission processes. PMID:22651244

  8. U(III)-CN versus U(IV)-NC coordination in tris(silylamide) complexes.

    PubMed

    Herv, Alexandre; Bouzidi, Yamina; Berthet, Jean-Claude; Belkhiri, Lotfi; Thury, Pierre; Boucekkine, Abdou; Ephritikhine, Michel

    2015-03-01

    Treatment of the metallacycle [UN*2(N,C)] [N* = N(SiMe3)2; N,C = CH2SiMe2N(SiMe3)] with [HNEt3][BPh4], [HNEt3]Cl, and [pyH][OTf] (OTf = OSO2CF3) gave the cationic compound [UN*3][BPh4] (1) and the neutral complexes [UN*3X] [X = Cl (3), OTf (4)], respectively. The dinuclear complex [{UN*(?-N,C)(?-OTf)}2] (5) and its tetrahydrofuran (THF) adduct [{UN*(N,C)(THF)(?-OTf)}2] (6) were obtained by thermal decomposition of 4. The successive addition of NEt4CN or KCN to 1 led to the formation of the cyanido-bridged dinuclear compound [(UN*3)2(?-CN)][BPh4] (7) and the mononuclear mono- and bis(cyanide) complexes [UN*3(CN)] (2) and [M][UN*3(CN)2] [M = NEt4 (8), K(THF)4 (9)], while crystals of [K(18-crown-6)][UN*3(CN)2] (10) were obtained by the oxidation of [K(18-crown-6)][UN*3(CN)] with pyridine N-oxide. The THF adduct of 1, [UN*3(THF)][BPh4], and complexes 2-7, 9 and 10 were characterized by their X-ray crystal structure. In contrast to their U(III) analogues [NMe4][UN*3(CN)] and [K(18-crown-6)]2[UN*3(CN)2] in which the CN anions are coordinated to the metal center via the C atom, complexes 2 and 9 exhibit the isocyanide U-NC coordination mode of the cyanide ligand. This U(III)/U(IV) differentiation has been analyzed using density functional theory calculations. The observed preferential coordinations are well explained considering the electronic structures of the different species and metal-ligand bonding energies. A comparison of the different quantum descriptors, i.e., bond orders, NPA/QTAIM data, and energy decomposition analysis, has allowed highlighting of the subtle balance between covalent, ionic, and steric factors that govern the U-CN/NC bonding. PMID:25686295

  9. Meeting the Needs of Children with Medical Complexity Using a Telehealth Advanced Practice Registered Nurse Care Coordination Model

    PubMed Central

    Erickson, Mary; Lunos, Scott; Finkelstein, Stanley M.; Looman, Wendy; Celebreeze, Margaret; Garwick, Ann

    2015-01-01

    Effective care coordination is a key quality and safety strategy for populations with chronic conditions, including children with medical complexity (CMC). However, gaps remain in parent report of the need for care coordination help and receipt of care coordination help. New models must close this gap while maintaining family-centered focus. A three-armed randomized controlled trial conducted in an established medical home utilized an advanced practice registered nurse intervention based on Preslers model of clinic-based care coordination. The model supported families of CMC across settings using telephone only or telephone and video telehealth care coordination. Effectiveness was evaluated from many perspectives and this paper reports on a subset of outcomes that includes family-centered care (FCC), need for care coordination help and adequacy of care coordination help received. FCC at baseline and end of study showed no significant difference between groups. Median FCC scores of 18.020.0 across all groups indicated high FCC within the medical home. No significant differences were found in the need for care coordination help within or between groups and over time. No significant difference was found in the adequacy of help received between groups at baseline. However, this indicator increased significantly over time for both intervention groups. These findings suggest that in an established medical home with high levels of FCC, families of CMC have unmet needs for care coordination help that are addressed by the APRN telehealth care coordination model. PMID:25424455

  10. Meeting the Needs of Children with Medical Complexity Using a Telehealth Advanced Practice Registered Nurse Care Coordination Model.

    PubMed

    Cady, Rhonda G; Erickson, Mary; Lunos, Scott; Finkelstein, Stanley M; Looman, Wendy; Celebreeze, Margaret; Garwick, Ann

    2014-11-26

    Effective care coordination is a key quality and safety strategy for populations with chronic conditions, including children with medical complexity (CMC). However, gaps remain in parent report of the need for care coordination help and receipt of care coordination help. New models must close this gap while maintaining family-centered focus. A three-armed randomized controlled trial conducted in an established medical home utilized an advanced practice registered nurse intervention based on Presler's model of clinic-based care coordination. The model supported families of CMC across settings using telephone only or telephone and video telehealth care coordination. Effectiveness was evaluated from many perspectives and this paper reports on a subset of outcomes that includes family-centered care (FCC), need for care coordination help and adequacy of care coordination help received. FCC at baseline and end of study showed no significant difference between groups. Median FCC scores of 18.0-20.0 across all groups indicated high FCC within the medical home. No significant differences were found in the need for care coordination help within or between groups and over time. No significant difference was found in the adequacy of help received between groups at baseline. However, this indicator increased significantly over time for both intervention groups. These findings suggest that in an established medical home with high levels of FCC, families of CMC have unmet needs for care coordination help that are addressed by the APRN telehealth care coordination model. PMID:25424455

  11. Cation-? and CH-? Interactions in the Coordination and Solvation of Cu(+)(acetylene)n Complexes.

    PubMed

    Brathwaite, Antonio D; Ward, Timothy B; Walters, Richard S; Duncan, Michael A

    2015-06-01

    Copper-acetylene cation complexes of the form Cu(C2H2)n(+) (n = 1-8) are produced by laser ablation in a supersonic expansion of acetylene/argon. The ions are mass selected and studied via infrared laser photodissociation spectroscopy in the C-H stretching region (3000-3500 cm(-1)). The structure and bonding of these complexes are investigated through the number of infrared active bands, their relative intensities and their frequency positions. Density functional theory calculations are carried out in support of the experimental data. The combined data show that cation-? complexes are formed for the n = 1-3 species, resulting in red-shifted C-H stretches on the acetylene ligands. The coordination of the copper cation is completed with three acetylene ligands, forming a "propeller" structure with D3 symmetry. Surprisingly, complexes with even greater numbers of acetylenes than this (4-6) have distinctive infrared band patterns quite different from those of the smaller complexes. Experiment combined with theory establishes that there is a fascinating pattern of second-sphere solvation involving the binding of acetylenes in bifurcated CH-? binding sites at the apex of two core ligands. This binding motif leads to three equivalent sites for second-sphere ligands, which when filled form a highly symmetrical Cu(+)(C2H2)6 complex. Solvent binding in this complex induces a structural change to planarity in the core, producing an appealing "core-shell" structure with D3h symmetry. PMID:25951753

  12. Synthesis and structure of six-coordinate iron borohydride complexes supported by PNP ligands.

    PubMed

    Koehne, Ingo; Schmeier, Timothy J; Bielinski, Elizabeth A; Pan, Cassie J; Lagaditis, Paraskevi O; Bernskoetter, Wesley H; Takase, Michael K; Wrtele, Christian; Hazari, Nilay; Schneider, Sven

    2014-02-17

    The preparation of a number of iron complexes supported by ligands of the type HN{CH2CH2(PR2)}2 [R = isopropyl (((i)Pr)PNP) or cyclohexyl ((Cy)PNP)] is reported. This is the first time this important bifunctional ligand has been coordinated to iron. The iron(II) complexes (((i)Pr)PNP)FeCl2(CO) (1a) and ((Cy)PNP)FeCl2(CO) (1b) were synthesized through the reaction of the appropriate free ligand and FeCl2 in the presence of CO. The iron(0) complex (((i)Pr)PNP)Fe(CO)2 (2a) was prepared through the reaction of Fe(CO)5 with ((i)Pr)PNP, while irradiating with UV light. Compound 2a is unstable in CH2Cl2 and is oxidized to 1a via the intermediate iron(II) complex [(((i)Pr)PNP)FeCl(CO)2]Cl (3a). The reaction of 2a with HCl generated the related complex [(((i)Pr)PNP)FeH(CO)2]Cl (4a), while the neutral iron hydrides (((i)Pr)PNP)FeHCl(CO) (5a) and ((Cy)PNP)FeHCl(CO) (5b) were synthesized through the reaction of 1a or 1b with 1 equiv of (n)Bu4NBH4. The related reaction between 1a and excess NaBH4 generated the unusual ?(1)-HBH3 complex (((i)Pr)PNP)FeH(?(1)-HBH3)(CO) (6a). This complex features a bifurcated intramolecular dihydrogen bond between two of the hydrogen atoms associated with the ?(1)-HBH3 ligand and the N-H proton of the pincer ligand, as well as intermolecular dihydrogen bonding. The protonation of 6a with 2,6-lutidinium tetraphenylborate resulted in the formation of the dimeric complex [{(((i)Pr)PNP)FeH(CO)}2(?2,?(1):?(1)-H2BH2)][BPh4] (7a), which features a rare example of a ?2,?(1):?(1)-H2BH2 ligand. Unlike all previous examples of complexes with a ?2,?(1):?(1)-H2BH2 ligand, there is no metal-metal bond and additional bridging ligand supporting the borohydride ligand in 7a; however, it is proposed that two dihydrogen-bonding interactions stabilize the complex. Complexes 1a, 2a, 3a, 4a, 5a, 6a, and 7a were characterized by X-ray crystallography. PMID:24499462

  13. MICOS coordinates with respiratory complexes and lipids to establish mitochondrial inner membrane architecture.

    PubMed

    Friedman, Jonathan R; Mourier, Arnaud; Yamada, Justin; McCaffery, J Michael; Nunnari, Jodi

    2015-01-01

    The conserved MICOS complex functions as a primary determinant of mitochondrial inner membrane structure. We address the organization and functional roles of MICOS and identify two independent MICOS subcomplexes: Mic27/Mic10/Mic12, whose assembly is dependent on respiratory complexes and the mitochondrial lipid cardiolipin, and Mic60/Mic19, which assembles independent of these factors. Our data suggest that MICOS subcomplexes independently localize to cristae junctions and are connected via Mic19, which functions to regulate subcomplex distribution, and thus, potentially also cristae junction copy number. MICOS subunits have non-redundant functions as the absence of both MICOS subcomplexes results in more severe morphological and respiratory growth defects than deletion of single MICOS subunits or subcomplexes. Mitochondrial defects resulting from MICOS loss are caused by misdistribution of respiratory complexes in the inner membrane. Together, our data are consistent with a model where MICOS, mitochondrial lipids and respiratory complexes coordinately build a functional and correctly shaped mitochondrial inner membrane. PMID:25918844

  14. Matrix isolation infrared spectroscopic and theoretical study of noble gas coordinated rhodium-dioxygen complexes.

    PubMed

    Yang, Rui; Gong, Yu; Zhou, Han; Zhou, Mingfei

    2007-01-11

    Reactions of rhodium atoms with dioxygen molecules in solid argon have been investigated using matrix isolation infrared absorption spectroscopy. The rhodium-dioxygen complexes, Rh(eta2-O2), Rh(eta2-O2)2, and Rh(eta2-O2)2(eta1-OO), are produced spontaneously on annealing. The Rh(eta2-O2) complex rearranges to the inserted RhO2 molecule under visible light irradiation. Experiments doped with xenon in argon show that the rhodium-dioxygen complexes are coordinated by one or two noble gas atoms in solid noble gas matrixes. Hence, the Rh(eta2-O2), Rh(eta2-O2)2, and Rh(eta2-O2)2(eta1-OO) molecules trapped in solid noble gas matrixes should be regarded as the Rh(eta2-O2)(Ng)2, Rh(eta2-O2)2(Ng)2, and Rh(eta2-O2)2(eta1-OO)(Ng) (Ng = Ar or Xe) complexes. The product absorptions are identified on the basis of isotopic substitution and density functional theory calculations. PMID:17201389

  15. Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)[subscript 2

    ERIC Educational Resources Information Center

    Charleton, Kimberly D. M.; Prokopchuk, Ernest M.

    2011-01-01

    A laboratory experiment aimed at students who are studying coordination chemistry of transition-metal complexes is described. A simple vanadyl acetylacetonate complex can be used as a catalyst in the hydrogen peroxide oxidation of anthracene to produce anthraquinone. The reaction can be performed under a variety of reaction conditions, ideally by

  16. Assembly of Heterometallic Rigid-Rod Complexes and Coordination Oligomers from Gold(I) Metalloligands.

    PubMed

    Cmara, Vernica; Barquero, Natalia; Bautista, Delia; Gil-Rubio, Juan; Vicente, Jos

    2015-07-01

    The reactions of TpylC6H4C?CAuL (Tpyl = 2,2':6',2?-terpyridin-4'-yl; L = PPh3, CNXy; Xy = 2,6-dimethylphenyl) with MX2nH2O (M = Fe, X = ClO4; M = Co, X = BF4; M = Zn, X = TfO, ClO4) in a 2:1 molar ratio give complexes [M(TpylC6H4C?CAuL)2]X2. Similarly, the reactions of PPN[(TpylC6H4C?C)2Au] (PPN = (Ph3P)2N) with an equimolar amount of MX2nH2O give coordination oligomers [M{(TpylC6H4C?C)2Au}]nXn (M = Fe, Zn, X = ClO4; M = Co, X = BF4). The complexes and oligomers have been isolated and characterized. The crystal structures of [Fe(TpylC6H4C?CAuCNXy)2](ClO4)2 and [Co(TpylC6H4C?CAuPPh3)2](BF4)2 have been determined by X-ray diffraction. The hydrodynamic sizes of complexes [M(TpylC6H4C?CAuPPh3)2]X2 and coordination oligomers [M{(TpylC6H4C?C)2Au}]nXn have been studied by NMR diffusion spectroscopy and dynamic light scattering measurements. PMID:26087239

  17. Integrated complex care coordination for children with medical complexity: A mixed-methods evaluation of tertiary care-community collaboration

    PubMed Central

    2012-01-01

    Background Primary care medical homes may improve health outcomes for children with special healthcare needs (CSHCN), by improving care coordination. However, community-based primary care practices may be challenged to deliver comprehensive care coordination to complex subsets of CSHCN such as children with medical complexity (CMC). Linking a tertiary care center with the community may achieve cost effective and high quality care for CMC. The objective of this study was to evaluate the outcomes of community-based complex care clinics integrated with a tertiary care center. Methods A before- and after-intervention study design with mixed (quantitative/qualitative) methods was utilized. Clinics at two community hospitals distant from tertiary care were staffed by local community pediatricians with the tertiary care center nurse practitioner and linked with primary care providers. Eighty-one children with underlying chronic conditions, fragility, requirement for high intensity care and/or technology assistance, and involvement of multiple providers participated. Main outcome measures included health care utilization and expenditures, parent reports of parent- and child-quality of life [QOL (SF-36, CPCHILD, PedsQL)], and family-centered care (MPOC-20). Comparisons were made in equal (up to 1 year) pre- and post-periods supplemented by qualitative perspectives of families and pediatricians. Results Total health care system costs decreased from median (IQR) $244 (981) per patient per month (PPPM) pre-enrolment to $131 (355) PPPM post-enrolment (p=.007), driven primarily by fewer inpatient days in the tertiary care center (p=.006). Parents reported decreased out of pocket expenses (p<.0001). Parental QOL did not significantly change over the course of the study. Child QOL improved between baseline and 6 months in two PedsQL domains [Social (p=.01); Emotional (p=.003)], and between baseline and 1 year in two CPCHILD domains [Health Standardization Section (p=.04); Comfort and Emotions (p=.03)], while total CPCHILD score decreased between baseline and 1 year (p=.003). Parents and providers reported the ability to receive care close to home as a key benefit. Conclusions Complex care can be provided in community-based settings with less direct tertiary care involvement through an integrated clinic. Improvements in health care utilization and family-centeredness of care can be achieved despite minimal changes in parental perceptions of child health. PMID:23088792

  18. Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

    2003-02-01

    The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

  19. Anion recognition by uranyl-salophen derivatives as probed by infrared multiple photon dissociation spectroscopy and ab initio modeling.

    PubMed

    Bodo, Enrico; Ciavardini, Alessandra; Dalla Cort, Antonella; Giannicchi, Ilaria; Yafteh Mihan, Francesco; Fornarini, Simonetta; Vasile, Silvana; Scuderi, Debora; Piccirillo, Susanna

    2014-09-01

    The vibrational features and molecular structures of complexes formed by a series of uranyl-salophen receptors with simple anions, such as Cl(-) , H(-) , and HCOO(-) , have been investigated in the gas phase. Spectra of the anionic complexes were studied in the $\\tilde \

  20. Cobalamin reduction by dithionite. Evidence for the formation of a six-coordinate cobalamin(II) complex.

    PubMed

    Salnikov, Denis S; Silaghi-Dumitrescu, Radu; Makarov, Sergei V; van Eldik, Rudi; Boss, Gerry R

    2011-10-14

    Evidence for the formation of a unique, six-coordinate cobalamin(II) complex with the anion-radical SO(2)(-) during the reduction of aquacobalamin(III) by sodium dithionite, was obtained from spectrophotometric and EPR measurements. The pK(a) value of the weakly coordinated dimethylbenzimidazole group was found to be 4.8 0.1 at 25 C. PMID:21879074

  1. Synthesis and Characterization of Three-Coordinate Ni(III)-Imide Complexes

    PubMed Central

    Iluc, Vlad M.; Miller, Alexander J. M.; Anderson, John S.; Monreal, Marisa J.; Mehn, Mark P.; Hillhouse, Gregory L.

    2011-01-01

    A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. The oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III) imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two nickel(III)-imide compounds showed different variable-temperature magnetic properties, but analogous EPR spectra at low temperatures. In order to account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted imide nickel(III) complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the nickel(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the Ni=N core but also in favoring one rotamer of the resulting nickel(III) imide, by locking in the phenyl ring in a perpendicular orientation with respect to the NiPP plane. PMID:21797224

  2. Synthesis and study of cationic, two-coordinate triphenylphosphine-gold-? complexes.

    PubMed

    Brooner, Rachel E M; Brown, Timothy J; Widenhoefer, Ross A

    2013-06-17

    Cationic, two-coordinate triphenylphosphine-gold(I)-? complexes of the form [(PPh?)Au(? ligand)]?SbF?? (? ligand=4-methylstyrene, 1?SbF?), 2-methyl-2-butene (3?SbF?), 3-hexyne (6?SbF?), 1,3-cyclohexadiene (7?SbF?), 3-methyl-1,2-butadiene (8?SbF?), and 1,7-diphenyl-3,4-heptadiene (10?SbF?) were generated in situ from reaction of [(PPh?)AuCl], AgSbF?, and ? ligand at -78 C and were characterized by low-temperature, multinuclear NMR spectroscopy without isolation. The ? ligands of these complexes were both weakly bound and kinetically labile and underwent facile intermolecular exchange with free ligand (?G(?) ?9 kcal mol(-1) in the case of 6?SbF?) and competitive displacement by weak ? donors, such as trifluoromethane sulfonate. Triphenylphosphine-gold(I)-? complexes were thermally unstable and decomposed above -20 C to form the bis(triphenylphosphine) gold cation [(PPh?)?Au]?SbF?? (2?SbF?). PMID:23592521

  3. Revised coordination model and stability constants of Cu(II) complexes of tris buffer.

    PubMed

    Nagaj, Justyna; Stokowa-So?tys, Kamila; Kurowska, Ewa; Fr?czyk, Tomasz; Je?owska-Bojczuk, Ma?gorzata; Bal, Wojciech

    2013-12-16

    2-Amino-2-hydroxymethyl-propane-1,3-diol, or tris(hydroxymethyl)aminomethane (Tris), is probably the most common biochemical buffer used alone or in combination with other buffers because it is stable, unreactive, and compatible with most proteins and other biomolecules. Being nontoxic, it has even found applications in medicine. Tris is known, however, to coordinate transition metal ions, Cu(II) among them. Although often ignored, this feature affects interactions of Cu(II) ions with biomolecules, as Tris is usually used in high molar excess. Therefore, it is important to have precise knowledge on the stoichiometry, stability, and reactivity of cupric Tris complexes. The literature data are incoherent in this respect. We reinvestigated the complex formation in the Tris-Cu(II) system by potentiometry, UV-vis, ESI-MS, and EPR at a broad range of concentrations and ratios. We found, contrary to several previous papers, that the maximum stoichiometry of Tris to Cu(II) is 2 and at neutral pH, dimeric complexes are formed. The apparent affinity of Tris buffer for Cu(II), determined by the competitivity index (CI) approach [Kr??el, A.; Wjcik, J.; Maciejczyk, M.; Bal, W. Chem. Commun. 2003, 6, 704-705] at pH 7.4 varies between 2 10(6) and 4 10(4) M(-1), depending on the Tris and Cu(II) concentrations and molar ratio. PMID:24304384

  4. Insights into copper coordination in the EcoRIDNA complex by ESR spectroscopy

    PubMed Central

    Ji, Ming; Tan, Likun; Jen-Jacobson, Linda; Saxena, Sunil

    2015-01-01

    The EcoRI restriction endonuclease requires one divalent metal ion in each of two symmetrical and identical catalytic sites to catalyse double-strand DNA cleavage. Recently, we showed that Cu2+ binds outside the catalytic sites to a pair of new sites at H114 in each sub-unit, and inhibits Mg2+ -catalysed DNA cleavage. In order to provide more detailed structural information on this new metal ion binding site, we performed W-band (~94 GHz) and X-band (~9.5 GHz) electron spin resonance spectroscopic measurements on the EcoRIDNA(Cu2+ )2 complex. Cu2+ binding results in two distinct components with different gzz and Azz values. X-band electron spin echo envelope modulation results indicate that both components arise from a Cu2+ coordinated to histidine. This observation is further confirmed by the hyperfine sub-level correlation results. W-band electron nuclear double resonance spectra provide evidence for equatorial coordination of water molecules to the Cu2+ ions. PMID:25750461

  5. Analytical description for the critical fixations of evolutionary coordination games on finite complex structured populations.

    PubMed

    Zhang, Liye; Zou, Yong; Guan, Shuguang; Liu, Zonghua

    2015-04-01

    Evolutionary game theory is crucial to capturing the characteristic interaction patterns among selfish individuals. In a population of coordination games of two strategies, one of the central problems is to determine the fixation probability that the system reaches a state of networkwide of only one strategy, and the corresponding expectation times. The deterministic replicator equations predict the critical value of initial density of one strategy, which separates the two absorbing states of the system. However, numerical estimations of this separatrix show large deviations from the theory in finite populations. Here we provide a stochastic treatment of this dynamic process on complex networks of finite sizes as Markov processes, showing the evolutionary time explicitly. We describe analytically the effects of network structures on the intermediate fixations as observed in numerical simulations. Our theoretical predictions are validated by various simulations on both random and scale free networks. Therefore, our stochastic framework can be helpful in dealing with other networked game dynamics. PMID:25974547

  6. Analytical description for the critical fixations of evolutionary coordination games on finite complex structured populations

    NASA Astrophysics Data System (ADS)

    Zhang, Liye; Zou, Yong; Guan, Shuguang; Liu, Zonghua

    2015-04-01

    Evolutionary game theory is crucial to capturing the characteristic interaction patterns among selfish individuals. In a population of coordination games of two strategies, one of the central problems is to determine the fixation probability that the system reaches a state of networkwide of only one strategy, and the corresponding expectation times. The deterministic replicator equations predict the critical value of initial density of one strategy, which separates the two absorbing states of the system. However, numerical estimations of this separatrix show large deviations from the theory in finite populations. Here we provide a stochastic treatment of this dynamic process on complex networks of finite sizes as Markov processes, showing the evolutionary time explicitly. We describe analytically the effects of network structures on the intermediate fixations as observed in numerical simulations. Our theoretical predictions are validated by various simulations on both random and scale free networks. Therefore, our stochastic framework can be helpful in dealing with other networked game dynamics.

  7. Influence of second coordination sphere hydroxyl groups on the reactivity of copper(I) complexes.

    PubMed

    Letko, Christopher S; Rauchfuss, Thomas B; Zhou, Xiaoyuan; Gray, Danielle L

    2012-04-16

    We report the enhanced reactivity of hydroxyl substituted CuN(3)(+) derivatives, where N(3) = tris(picolinyl)methane (tripic) and related derivatives, upon deprotonation of the O-H functionality. The work capitalizes on new methodology for incorporating hydroxyl groups into the second coordination sphere of copper centers. The key synthetic methodology relies on Pd-catalyzed coupling reactions of dilithiated 6-methyl-2-pyridone with bromopyridyl derivatives. These building blocks allow the preparation of tridentate N(3) ligands with OH and OMe substituents flanking the fourth coordination site of a tetrahedral complex. Coupling of these tridendate ligands gives the corresponding hydroxy- and methoxy-functionalized bistripodal ligands. [Cu[bis(2-methylpyrid-6-yl)(2-hydroxypyrid-6-yl)methane](NCMe)](+) ([Cu(2H)(NCMe)](+)) oxidizes readily in air to afford the mixed valence Cu(1.5) dimer ([Cu(2)(2)(2)](+)). Formation of [Cu(2)(2)(2)](+) is accelerated in the presence of base and can be reversed with a combination of decamethylferrocene and acid. The reactivity of [Cu(2H)(NCMe)](+) with dioxygen requires deprotonation of the hydroxyl substituent: neither [Cu(tripic)(NCMe)](+) nor the methoxy-derivatives displayed comparable reactivity. A related mixed valence dimer formed upon oxidation of the dicopper(I) complex of a tetrahydroxy bis(tridentate) ligand, [Cu(2)(6H(4))(NCMe)(2)](2+). The dicopper(I) complex of the analogous tetramethoxy N(6)-ligand, [Cu(2)(5)(NCMe)(2)](2+), instead reversibly binds O(2). Deprotonation of [Cu(2H)(CO)](+) and [Cu(2H)(NCMe)](+) afforded the neutral derivatives Cu(2)(CO) and Cu(2)(2)(2), respectively. The dicopper(I) derivative Cu(2)(2)(2) can be reoxidized, reprotonated, and carbonylated. The silver(I) complex, [Ag(2H)(NCMe)]BF(4), forms an analogous neutral dimer (Ag(2)(2)(2)) upon deprotonation of the hydroxyl group. The structures of ligand 2H, [Cu(2)(5)(NCMe)(2)](+), [Cu(2)(2)(2)](+), [Cu(2)(6H(2))](+), [Ag(2H)(NCMe)]BF(4), and Ag(2)(2)(2) were confirmed by single crystal X-ray diffraction. PMID:22452599

  8. Overcoming spontaneous patterns of coordination during the acquisition of a complex balancing task.

    PubMed

    Caillou, N; Delignieres, D; Nourrit, D; Deschamps, T; Lauriot, B

    2002-12-01

    Learning in complex tasks is usually conceived as the problem of mastering the multiple and redundant degrees of freedom of the system. To reduce control requirements, two different strategies are conceivable. The first one consists of a "freezing-freeing" process for most articular joints to reduce the number of active biomechanical degrees of freedom to be managed. The second strategy consists of introducing rigid couplings between the oscillators building the system. In this case, learning implies the dissolution of initial couplings and the emergence of new, more task-specific couplings. The goal of our study was to analyze the spontaneous coordination of beginners and its development in a complex balancing task on a stabilometer, and to examine the emergence of these two strategies. Our results showed that beginners were characterized by strong couplings between the joints of the lower limbs. During learning, new and more task-specific couplings emerged that reflected a new organization of the trunk and a decoupling of some joints of the lower limbs that were initially coupled during the first few trials. PMID:12491652

  9. Emissive iridium(III) diimine complexes formed by double cyclometalation of coordinated triphenylphosphite.

    PubMed

    Chang, Yao-Yuan; Hung, Jui-Yi; Chi, Yun; Chyn, Jong-Pyng; Chung, Min-Wen; Lin, Chia-Li; Chou, Pi-Tai; Lee, Gene-Hsiang; Chang, Chih-Hao; Lin, Wei-Chieh

    2011-06-01

    We report on the synthesis of a new series of iridium(III) complexes functionalized with various diimine chromophores, together with a facially coordinated dicyclometalated phosphite chelate and a monodentate anionic ancillary. This conceptual design presents a novel strategy in obtaining a new class of iridium(III) diimine complexes without employment of traditional nitrogen-containing polyaromatic cyclometalates. Additionally, we discuss the basic charactersistics of the ground and lower-lying excited states involved, as documented by crystal structural, photophysical studies, and density functional theory calculations. Fabrication of the green-emitting organic light-emitting diodes with one such dopant, [Ir(dbbpy)(tpit)NCS] (2b), where dbbpy and tpit represent di-tert-butyl-2,2'-bipyridine and dicyclometalated triphenylphosphite, respectively, was successfully made, attaining a peak external quantum efficiency (?(ext)), a luminance efficiency (?(l)), and a power efficiency (?(p)) of 14.1%, 46.6 cd A(-1), and 39.9 lm W(-1), respectively. PMID:21542620

  10. X-ray Emission Spectroscopy to Study Ligand Valence Orbitals in Mn Coordination Complexes

    SciTech Connect

    Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes; Merz, Kathrin; Weyhermuller, Thomas; Bergmann, Uwe; Pushkar, Yulia; Yano, Junko; Yachandra, Vittal K.; Glatzel, Pieter

    2009-03-02

    We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in X-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular X-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g., C, N, O...), to be distinguished. A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)6]2+, [Mn(H2O)5OH]+, [Mn(H2O)5NH2]+, and [Mn(H2O)5NH3]2+. An application of the method, with comparison between theory and experiment, is presented for the solvated Mn2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N3]BPh4, [LMn(B2O3Ph2)(ClO4)], and [LMn(acac)N]BPh4, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion, and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion.

  11. X-ray emission spectroscopy to study ligand valence orbitals in Mn coordination complexes

    PubMed Central

    Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes; Merz, Kathrin; Weyhermller, Thomas; Bergmann, Uwe; Pushkar, Yulia; Yano, Junko; Yachandra, Vittal K.; Glatzel, Pieter

    2009-01-01

    We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in x-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular x-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g. C, N, O...), to be distinguished . A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)6]2+, [Mn(H2O)5OH]+, [Mn(H2O)5NH2]+ and [Mn(H2O)5NH3]2+. An application of the method, with comparison between theory and experiment, is presented for solvated Mn2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N3]BPh4, [LMn(B2O3Ph2)(ClO4)] and [LMn(acac)N]BPh4 where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion. PMID:19663435

  12. Characterization of Ce SUP 3+-tributyl phosphate coordination complexes produced by fused droplet electrospray ionization with a target capillary

    SciTech Connect

    Gary S. Groenewold; Jean-Jacques Gaumet

    2011-12-01

    Coordination complexes containing Ce(III) and tri-n-butyl phosphate (TBP) in the 1+, 2+ and 3+ charge states were generated using desorption electrospray ionization (DESI) mass spectrometry, in which the analyte solutions were supplied via a target capillary orthogonally situated with respect to the electrospray. Comparison with direct electrospray (ESI) showed that the same coordination complexes were produced in each experiment, and could be described by the general formula [Ce(NO3)m=0-2(TBP)n](3-m)+. This result indicates that DESI has utility for measuring metal speciation for metal ligand solutions where the gas-phase complexes generated by ESI have been correlated with solution speciation. Such an application would be useful for analyses where it is desirable to limit the total amount of metal being handled, or that have solvent systems that are not readily amenable to ESI. Both the direct ESI and DESI mass spectra showed similar trends with respect to the TBP:Ce ratio, viz. high values tend to favor formation of a larger fraction of the 1+ species, and the 2+ and 3+ species become relatively more important as the ratio is decreased. Within individual charge state ion envelopes, lower TBP:Ce ratios produce coordination complexes with fewer ligands, a trend also seen using both approaches. These trends again point toward strong similarity between the direct ESI and DESI analyses of the metal-ligand solutions. The DESI experiments were less sensitive for measuring the coordination complexes compared to the direct ESI experiments, by a factor of 10 - 100 depending on whether minimum detectable concentration or absolute ion abundances were considered. Nevertheless, mid-picomolar quantities of coordination complexes were measured using the target capillary, indicating that sensitivity would be sufficient for measuring species in many industrial separations processes.

  13. Pillared and open-framework uranyl diphosphonates

    NASA Astrophysics Data System (ADS)

    Adelani, Pius O.; Albrecht-Schmitt, Thomas E.

    2011-09-01

    The hydrothermal reactions of uranium trioxide, uranyl acetate, or uranyl nitrate with 1,4-benzenebisphosphonic acid in the presence of very small amount of HF at 200 C results in the formation of three different uranyl diphosphonate compounds, [H 3O] 2{(UO 2) 6[C 6H 4(PO 3)(PO 2OH)] 2[C 6H 4(PO 2OH) 2] 2[C 6H 4(PO 3) 2]}(H 2O) 2 ( Ubbp-1), [H 3O] 4{(UO 2) 4[C 6H 4(PO 3) 2] 2F 4}H 2O ( Ubbp-2), and {(UO 2)[C 6H 2F 2(PO 2OH) 2(H 2O)} 2H 2O ( Ubbp-3). The crystal structures of these compounds were determined by single crystal X-ray diffraction experiments. Ubbp-1 consists of UO 7 pentagonal bipyramids that are bridged by the phosphonate moieties to form a three-dimensional pillared structure. Ubbp-2 is composed of UO 5F 2 pentagonal bipyramids that are bridged through the phosphonate oxygen atoms into one-dimensional chains that are cross-linked by the phenyl spacers into a pillared structure. The structure of Ubbp-3 is a three-dimensional open-framework with large channels containing water molecules with internal dimensions of approximately 10.910.9 . Ubbp-1 and Ubbp-2 fluoresce at room temperature.

  14. A protein carboxylate coordinated oxo-centered tri-nuclear iron complex with possible implications for ferritin mineralization

    Microsoft Academic Search

    Martin Hgbom; Pr Nordlund

    2004-01-01

    The crystal structure of an oxo-centered tri-nuclear iron complex formed on a protein surface is presented. The cluster forms when crystals of the class Ib ribonucleotide reductase R2 protein from Corynebacterium ammoniagenes are subjected to iron soaking. The tri-iron-oxo complex is coordinated by protein-derived carboxylate ligands arranged in a motif similar to the one found on the inner surface of

  15. Liquid chromatographic separation of metal-tetraphenylporphine complexes based on coordination interaction with immobilized neutral ligand in stationary phase

    Microsoft Academic Search

    Tomohiro Suzuki; Koichi Matsumoto; Kin-ichi Tsunoda; Hideo Akaiwa

    1997-01-01

    Proposed is a novel liquid chromatographic system for metal chelates based on the coordination interaction between the central metal in a complex and immobilized neutral ligand in the stationary phase. For this purpose, a 2-(4-pyridyl)ethyl bonded silica gel (4-PES) column was newly prepared, and cobalt(II)-, nickel(II)-, copper(II)-, and zinc(II)-tetraphenylporphine (TPP) complexes were separated on the 4-PES column as well as

  16. NMR crystallography for structural characterization of oxovanadium(V) complexes: deriving coordination geometry and detecting weakly coordinated ligands at atomic resolution in the solid state.

    PubMed

    Li, Mingyue; Yehl, Jenna; Hou, Guangjin; Chatterjee, Pabitra B; Goldbourt, Amir; Crans, Debbie C; Polenova, Tatyana

    2015-02-16

    NMR crystallography is an emerging method for atomic-resolution structural analysis of ubiquitous vanadium(V) sites in inorganic and bioinorganic complexes as well as vanadium-containing proteins. NMR crystallography allows for characterization of vanadium(V) containing solids, based on the simultaneous measurement of (51)V-(15)N internuclear distances and anisotropic spin interactions, described by (13)C, (15)N, and (51)V chemical shift anisotropy and (51)V electric field gradient tensors. We show that the experimental (51)V, (13)C, and (15)N NMR parameters are essential for inferring correct coordination numbers and deriving correct geometries in density functional theory (DFT) calculations, particularly in the absence of single-crystal X-ray structures. We first validate this approach on a structurally known vanadium(V) complex, ((15)N-salicylideneglycinate)-(benzhydroxamate)oxovanadium(V), VO(15)NGlySalbz. We then apply this approach to derive the three-dimensional structure of (methoxo)((15)N-salicylidene-glycinato)oxovanadium(V) with solvated methanol, [VO((15)NGlySal)(OCH3)](CH3OH). This is a representative complex with potentially variable coordination geometry depending on the solvation level of the solid. The solid material containing molecules of CH3OH, formally expressed as [VO((15)NGlySal)(OCH3)](CH3OH), is found to have one molecule of CH3OH weakly coordinated to the vanadium. The material is therefore best described as [VO((15)NGlySal)(OCH3)(CH3OH)] as deduced by the combination of multinuclear solid-state NMR experiments and DFT calculations. The approach reported here can be used for structural analysis of systems that are not amenable to single-crystal X-ray diffraction characterization and which can contain weakly associated solvents. PMID:25590382

  17. Electronic Transitions as a Probe of Tetrahedral versus Octahedral Coordination in Nickel(II) Complexes: An Undergraduate Inorganic Chemistry Experiment.

    ERIC Educational Resources Information Center

    Filgueiras, Carlos A. L.; Carazza, Fernando

    1980-01-01

    Discusses procedures, theoretical considerations, and results of an experiment involving the preparation of a tetrahedral nickel(II) complex and its transformation into an octahedral species. Suggests that fundamental aspects of coordination chemistry can be demonstrated by simple experiments performed in introductory level courses. (Author/JN)

  18. Polymer complexes. LV. Spectroscopic, thermal studies, and coordination of metal ions N-[3-(5-amino-1,2,4-triazolo)] acrylamide polymer complexes

    Microsoft Academic Search

    M. A. Diab; A. Z. El-Sonbati; M. E. Attallah

    2012-01-01

    Novel polymeric complexes with a potentially bidentate ligand formed by amidation of 3,5-diamino-1,2,4-triazole with acryloyl chloride were synthesized and characterized on the basis of elemental analyses, IR, H-NMR, UV-Vis, magnetic susceptibility measurements, molar conductance, and thermal analyses. The molar conductance data reveal that all the polymer complexes are non-electrolytes. Spectral studies reveal that the free ligand coordinates bidentate to the

  19. Behaviors of acrylamide/itaconic acid hydrogels in uptake of uranyl ions from aqueous solutions

    SciTech Connect

    Karadag, E.; Saraydin, D. [Cumhuriyet Univ., Sivas (Turkey); Gueven, O. [Hacettepe Univ., Ankara (Turkey)

    1995-12-01

    In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with {gamma}-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178-219 mg uranyl ions from the solutions of uranyl acetate, 42-76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.

  20. Coordinatively saturated cationic ruthenium(II) complexes. Preparation, characterization, and reaction with potassium superoxide

    SciTech Connect

    Oshima, N.; Suzuki, H.; Moro-oka, Y.

    1986-09-10

    Coordinatively saturated cationic ruthenium(II) complexes, (eta/sup 5/-C/sub 5/H/sub 5/)(eta/sup 6/-C/sub 6/H/sub 6/)Ru/sup II/)(BF/sub 4/) (1), (eta/sup 5/-C/sub 5/Me/sub 5/)(eta/sup 6/-C/sub 66/)Ru/sup II/)(BF/sub 4/) (2), ((1-5-eta/sup 5/-C/sub 6/H/sub 7/)(eta/sup 6/-C/sub 6/H/sub 6/)Ru/sup II/)(BF/sub 4/) (3), ((1-5-eta/sup 5/-C/sub 7/H/sub 9/)(eta/sup 6/-C/sub 6/H/sub 7/)Ru/sup II/)(BF/sub 4/) (4), ((1-3:5,6-eta/sup 5/-C/sub 8/H/sub 1/exclamation)(eta/sup 6/-C/sub 6/H/sub 6/)Ru/sup II/)(BG/sub 4/)(5), and ((6-EtO-1-5-eta /sup 5/-C/sub 7/H/sub 8/)(eta/sup 6/-C/sub 6/H/sub 6/)Ru/sup II/)(BF/sub 4/) (7), are prepared by the reaction of (eta/sup 6/-C/sub 6/H/sub 6/)RuCl/sub 2/)/sub 2/ with cyclopentadiene, pentamethylcyclopentadiene, 1,3-cyclohexadiene, 1,3-cycloheptadiene, 1,5-cyclooctadiene, and 1,3,5-cycloheptatriene, respectively, in ethanol in the presence of AgBF/sub 4/. Superoxide anion attacks at the terminal position of the dienyl moiety of 3-5 to yield ruthenium(0) complexes 8-10, containing cyclic dienone ligand. 25 references, 4 figures, 4 tables.

  1. Coordination of tRNA transcription with export at nuclear pore complexes in budding yeast.

    PubMed

    Chen, Miao; Gartenberg, Marc R

    2014-05-01

    tRNAs are encoded by RNA polymerase III-transcribed genes that reside at seemingly random intervals along the chromosomes of budding yeast. Existing evidence suggests that the genes congregate together at the nucleolus and/or centromeres. In this study, we re-examined spatial and temporal aspects of tRNA gene (tDNA) expression. We show that tDNA transcription fluctuates during cell cycle progression. In M phase, when tRNA synthesis peaks, tDNAs localize at nuclear pore complexes (NPCs). Docking of a tDNA requires the DNA sequence of the contacted gene, nucleoporins Nup60 and Nup2, and cohesin. Characterization of mutants that block NPC localization revealed that docking is a consequence of elevated tDNA transcription. NPC-tDNA contact falters in the absence of the principal exportin of nascent tRNA, Los1, and genetic assays indicate that gating of tDNAs at NPCs favors cytoplasmic accumulation of functional tRNA. Collectively, the data suggest that tDNAs associate with NPCs to coordinate RNA polymerase III transcription with the nuclear export of pre-tRNA. The M-phase specificity of NPC contact reflects a regulatory mechanism that may have evolved, in part, to avoid collisions between DNA replication forks and transcribing RNA polymerase III machinery at NPCs. PMID:24788517

  2. Coordination Sphere Tuning of the Electron Transfer Dissociation Behavior of Cu(II)-Peptide Complexes

    NASA Astrophysics Data System (ADS)

    Dong, Jia; Vachet, Richard W.

    2012-02-01

    In contrast to previous electron capture dissociation (ECD) studies, we find that electron transfer dissociation (ETD) of Cu(II)-peptide complexes can generate c- and z-type product ions when the peptide has a sufficient number of strongly coordinating residues. Double-resonance experiments, ion-molecule reactions, and collision-induced dissociation (CID) prove that the c and z product ions are formed via typical radical pathways without the associated reduction of Cu(II), despite the high second ionization energy of Cu. A positive correlation between the number of Cu(II) binding groups in the peptide sequence and the extent of c and z ion formation was also observed. This trend is rationalized by considering that the recombination energy of Cu(II) can be lowered by strong binding ligands to an extent that enables electron transfer to non-Cu sites (e.g., protonation sites) to compete with Cu(II) reduction, thereby generating c/z ions in a manner similar to that observed for protonated (i.e., nonmetalated) peptides.

  3. Coordinatively saturated cationic ruthenium(II) complexes. Preparation, characterization, and reaction with potassium superoxide

    Microsoft Academic Search

    Noriaki Oshima; Hiroharu Suzuki; Yoshihiko Moro-oka

    1986-01-01

    Coordinatively saturated cationic ruthenium(II) complexes, (eta⁵-CH)(eta⁶-CH)Ru\\/sup II\\/)(BF) (1), (eta⁵-CMe)(eta⁶-C)Ru\\/sup II\\/)(BF) (2), ((1-5-eta⁵-CH)(eta⁶-CH)Ru\\/sup II\\/)(BF) (3), ((1-5-eta⁵-CH)(eta⁶-CH)Ru\\/sup II\\/)(BF) (4), ((1-3:5,6-eta⁵-CHexclamation)(eta⁶-CH)Ru\\/sup II\\/)(BG)(5), and ((6-EtO-1-5-eta ⁵-CH)(eta⁶-CH)Ru\\/sup II\\/)(BF) (7), are prepared by the reaction of (eta⁶-CH)RuCl) with cyclopentadiene, pentamethylcyclopentadiene, 1,3-cyclohexadiene, 1,3-cycloheptadiene, 1,5-cyclooctadiene, and 1,3,5-cycloheptatriene, respectively, in ethanol in the presence of AgBF. Superoxide anion attacks at the terminal position of the dienyl moiety of 3-5

  4. Biological activity and coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands.

    PubMed

    Creaven, Bernadette Sarah; Czegldi, Eszter; Devereux, Michael; Enyedy, va Anna; Foltyn-Arfa Kia, Agnieszka; Karcz, Dariusz; Kellett, Andrew; McClean, Siobhn; Nagy, Nra Veronika; Noble, Andy; Rockenbauer, Antal; Szab-Plnka, Terzia; Walsh, Maureen

    2010-12-01

    The coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands, which had previously shown good anti-Candida activity, were investigated by pH-potentiometric and UV-Vis spectroscopic methods. These studies confirmed the coordination mode of the ligands to be through the N of the imine and deprotonated phenol of the coumarin-derived ligand in solution. In addition, the more active complexes and their corresponding ligands were investigated in the presence of copper(II) in liquid and frozen solution by ESR spectroscopic methods. A series of secondary amine derivatives of the Schiff base ligands, were isolated with good solubility characteristics but showed little anti-Candida activity. However, cytotoxicity studies of the secondary amines, together with the copper complexes and their corresponding ligands, against human colon cancer and human breast cancer cells identified the chemotherapeutic potential of these new ligands. PMID:20949224

  5. Two coordination modes around the Cu(II) cations in complexes with benzo[b]furancarboxylic acids

    NASA Astrophysics Data System (ADS)

    Drzewiecka, Aleksandra; Koziol, Anna E.; Klepka, Marcin T.; Wolska, Anna; Jimenez-Pulido, Sonia B.; Lis, Tadeusz; Ostrowska, Kinga; Struga, Marta

    2013-02-01

    Three Cu(II) complexes with derivatives of the benzo[b]furancarboxylic acid have been synthesized and characterized by the elemental and thermal analyses, and IR spectroscopy. The geometry of metal-ligand interaction for all compounds has been described using X-ray absorption spectroscopy and for one of them by X-ray crystallography. Two mononuclear Cu(II) complexes, with 7-acetyl-5-bromo-6-hydroxy-3-methylbenzo[b]furan-2-carboxylic and 6-acetyl-5-hydroxy-2-methylbenzo[b]furan-3-carboxylic acids, exhibit a tetra-fold coordination, CuO4. The Cu(II) cation in crystals with 7-acetyl-6-methoxy-3-methyl-benzo[b]furan-2-carboxylic acid is penta-coordinated; the bridging COO- groups and ethanol molecule stabilize the dinuclear center Cu2O10. The powdered form of this complex is based on the Cu2O8 units, indicating the absence of the ethanol molecules.

  6. Interactions of platinum and ruthenium coordination complexes with pancreatic phospholipase A(2) and phospholipids investigated by MALDI TOF mass spectrometry.

    PubMed

    Kam?eva, Tina; Radisavljevi?, Maja; Vuki?evi?, Iva; Arnhold, Jrgen; Petkovi?, Marijana

    2013-11-01

    Phospholipase A2 is involved in propagation of inflammatory processes and carcinogenesis through its role in phospholipid metabolism, and release of arachidonic acid and lysophospholipids. Recent findings on correlation between elevated PLA2 activity and metastatic cancer render this enzyme an attractive target for cancer therapy. On the other hand, due to a broad range of oxidation states under physiological conditions and a high affinity for protein binding, platinum and ruthenium coordination complexes are promising candidates for PLA2 inhibitors. In this article, we discuss the interactions of Pt and Ru coordination complexes with PLA2 and phospholipids, as well as the application of MALDI-TOF mass spectrometry for screening PLA2 inhibitors. Owing to the ability of this technique to simultaneously detect and monitor changes in substrate and product concentrations, the inhibitor mechanisms of both Pt and Ru complexes with various ligands were determined. PMID:24243606

  7. AI Support of Teamwork for Coordinated Care of Children with Complex Ofra Amir and Barbara J. Grosz and Krzysztof Z. Gajos

    E-print Network

    Gajos, Krzysztof

    AI Support of Teamwork for Coordinated Care of Children with Complex Conditions Ofra Amir University leesanders@stanford.edu Abstract Children with complex health conditions require care from a large types of medical professionals. Coordination of their care is essential for good outcomes, and extensive

  8. Pro-oxidative, genotoxic and cytotoxic properties of uranyl ions.

    PubMed

    Garmash, S A; Smirnova, V S; Karp, O E; Usacheva, A M; Berezhnov, A V; Ivanov, V E; Chernikov, A V; Bruskov, V I; Gudkov, S V

    2014-01-01

    It is demonstrated that hydroxyl radicals and hydrogen peroxide are formed under the action of uranyl ions in aqueous solutions containing no reducing agents. In the presence of uranyl ions, formation of 8-oxoguanine in DNA and long-lived protein radicals are observed invitro. It is shown that the pro-oxidant properties of uranyl at micromolar concentrations mostly result from the physico-chemical nature of the compound rather than its radioactive decay. Uranyl ions lead to damage in DNA and proteins causing death of HEp-2 cells by necrotic pathway. It is revealed that the uranyl ions enhance radiation-induced oxidative stress and significantly increase a death rate of mice exposed to sublethal doses of X-rays. PMID:23312590

  9. Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: temperature effect and coordination modes.

    PubMed

    Rao, Linfeng; Garnov, Alexander Yu; Jiang, Jun; Di Bernardo, Plinio; Zanonato, PierLuigi; Bismondo, Arturo

    2003-06-01

    The complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg(-1) NaClO(4) is studied at variable temperatures (25-70 degrees C). Three U(VI)/ODA complexes (UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-)) and three Sm(III)/ODA complexes (SmL(j)((3-2)(j)+) with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (Delta C(p) degrees in J K(-1) mol(-1)) are 95 +/- 6, 297 +/- 14, and 162 +/- 19 for UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-), and 142 +/- 6, 198 +/- 14, and 157 +/- 19 for SmL(+), SmL(2)(-), and SmL(3)(3-), respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure. PMID:12767209

  10. Pillared and open-framework uranyl diphosphonates

    SciTech Connect

    Adelani, Pius O. [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: talbrec1@nd.edu [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2011-09-15

    The hydrothermal reactions of uranium trioxide, uranyl acetate, or uranyl nitrate with 1,4-benzenebisphosphonic acid in the presence of very small amount of HF at 200 deg. C results in the formation of three different uranyl diphosphonate compounds, [H{sub 3}O]{sub 2}{l_brace}(UO{sub 2}){sub 6}[C{sub 6}H{sub 4}(PO{sub 3})(PO{sub 2}OH)]{sub 2}[C{sub 6}H{sub 4}(PO{sub 2}OH){sub 2}]{sub 2}[C{sub 6}H{sub 4}(PO{sub 3}){sub 2}]{r_brace}(H{sub 2}O){sub 2} (Ubbp-1), [H{sub 3}O]{sub 4}{l_brace}(UO{sub 2}){sub 4}[C{sub 6}H{sub 4}(PO{sub 3}){sub 2}]{sub 2}F{sub 4}{r_brace}.H{sub 2}O (Ubbp-2), and {l_brace}(UO{sub 2})[C{sub 6}H{sub 2}F{sub 2}(PO{sub 2}OH){sub 2}(H{sub 2}O){r_brace}{sub 2}.H{sub 2}O (Ubbp-3). The crystal structures of these compounds were determined by single crystal X-ray diffraction experiments. Ubbp-1 consists of UO{sub 7} pentagonal bipyramids that are bridged by the phosphonate moieties to form a three-dimensional pillared structure. Ubbp-2 is composed of UO{sub 5}F{sub 2} pentagonal bipyramids that are bridged through the phosphonate oxygen atoms into one-dimensional chains that are cross-linked by the phenyl spacers into a pillared structure. The structure of Ubbp-3 is a three-dimensional open-framework with large channels containing water molecules with internal dimensions of approximately 10.9x10.9 A. Ubbp-1 and Ubbp-2 fluoresce at room temperature. - Graphical Abstract: Illustration of the three-dimensional open-framework structure of {l_brace}(UO{sub 2})[C{sub 6}H{sub 2}F{sub 2}(PO{sub 2}OH){sub 2}(H{sub 2}O){r_brace}{sub 2}.H{sub 2}O viewed along the c-axis. The structure is constructed from UO{sub 7} units, pentagonal bipyramids=green, oxygen=red, phosphorus=magenta, carbon=black, hydrogen=white. Highlights: > The influence of the uranyl salt anions and pH were critically examined in relation to structural variation. > The acetate and nitrate counter ions of uranyl may be acting as structure directing agents. > The use of rigid phenyl spacer yield a three-dimensional network of pillared structures of uranyl diphosphonates that fluoresce. > The fluorination of the phenyl ring under hydrothermal condition. > The large voids in this structure are suggestive of potential applications in sorption, separation of gases and in catalytic processes.

  11. Ligand displacement for fixing manganese: relevance to cellular metal ion transport and synthesis of polymeric coordination complexes.

    PubMed

    Sanchez-Ballester, Noelia M; Shrestha, Lok Kumar; Elsegood, Mark R J; Schmitt, Wolfgang; Ariga, Katsuhiko; Anson, Christopher E; Hill, Jonathan P; Powell, Annie K

    2013-02-28

    A dinuclear manganese(III) complex (1) of an N-(carboxymethyl)-N-[3,5-bis(?,?-dimethylbenzyl-2-hydroxybenzyl)]glycine (HDA) ligand (L) binds a manganese(II) species through displacement of its solvating ligands by appropriately dispositioned carbonyl groups of a dinuclear complex {[Mn(2)(L)(2)(OH)(OCH(3))][Mn(H(2)O)(3)(CH(3)OH)(3)], 2, triclinic P1, a = 13.172(3) , b = 15.897(3) , c = 19.059(4) , V = 3461.9(13) (3)} leading to a trinuclear complex {3, monoclinic P21/n, a = 11.7606(8) , b = 21.3505(8) , c = 26.7827(17) , V = 6722.7(7) (3)} with cyclization of two of the carboxy groups through the doubly-carboxy group coordinated Mn(2+) ion. The reaction is discussed in terms of its significance as an illustration of how Mn(2+) ions might be sequestered in biological systems. A similar solvato-ligand displacement reaction was used to synthesise coordination polymers of an HDA iron(III) complex involving polymerization through a bridging carboxylato group. Several isostructural polymers (5-7; for 5: orthorhombic Pbca, a = 9.411(5) , b = 16.390(8) , c = 37.968(19) , V = 5856(5) (3)) with different coordinated alcohols could be prepared indicating the potential synthetic uses of this method. PMID:23238775

  12. Synthesis, Characterization, and Theoretical Investigation of Two-Coordinate Palladium(0) and Platinum(0) Complexes Utilizing ?-Accepting Carbenes.

    PubMed

    Roy, Sudipta; Mondal, Kartik Chandra; Meyer, Jann; Nieptter, Benedikt; Khler, Christian; Herbst-Irmer, Regine; Stalke, Dietmar; Dittrich, Birger; Andrada, Diego M; Frenking, Gernot; Roesky, Herbert W

    2015-06-22

    An elegant general synthesis route for the preparation of two coordinate palladium(0) and platinum(0) complexes was developed by reacting commercially available tetrakis(triphenylphosphine)palladium/platinum with ?-accepting cyclic alkyl(amino) carbenes (cAACs). The complexes are characterized by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. The palladium complexes exhibit sharp color changes (crystallochromism) from dark maroon to bright green if the C-Pd-C bond angle is sharpened by approximately 6, which is chemically feasible by elimination of one lattice THF solvent molecule. The analogous dark orange-colored platinum complexes are more rigid and thus do not show this phenomenon. Additionally, [(cAAC)2 Pd/Pt] complexes can be quasi-reversibly oxidized to their corresponding [(cAAC)2 Pd/Pt](+) cations, as evidenced by cyclic voltammetry measurements. The bonding and stability are studied by theoretical calculations. PMID:25940809

  13. Experimental and theoretical studies on photophysical properties: tuning redox-active amido-tetrathiafulvalene derivatives in paramagnetic coordination complexes.

    PubMed

    Pointillart, Fabrice; Cauchy, Thomas; Le Gal, Yann; Golhen, Stphane; Cador, Olivier; Ouahab, Lahcne

    2010-02-15

    Amido-5-pyrimidine (1), -4-pyridine (2), -2-pyrazine (3), -2-pyridine (4), and -2-pyridine-N-oxide (5) derivatives of TTF (TTF = tetrathiafulvalene) have been synthesized and characterized. The crystal structure of 1 has been resolved. Their capacities to coordinate paramagnetic transition metal have been explored. The following new molecular compounds have been synthesized and obtained as single crystals: {[Cu(hfac)(2)(1)](H(2)O)}(2) (6), cis-[Mn(hfac)(2)(2)(2)](THF)(2) (7), trans-[Cu(hfac)(2)(3)(2)] (8), trans-[Cu(hfac)(2)(4)(2)] (9), and trans-[M(hfac)(2)(5)(2)] (M = Cu (10), Mn (11), Zn (12)). The crystal structures reveal that the nature of the coordinating substituent plays a fundamental role on the crystalline organization. Cyclic voltammetry measurements have been performed for all the species and they have permitted us to observe the redox activity of the free and linked donors. EPR measurements are in agreement with the solid-state structures. All the ligands and corresponding coordination complexes have been studied by UV-visible absorption spectroscopy. Gaussian deconvolutions have been performed to fit the experimental solid-state absorption curves. Molecular orbital diagram for ligands 4 and 5; and their coordination complexes have been determined. The nature of the thirty to fifty low-lying monoelectronic transitions occurring in the TTF derivatives have been identified by TD-DFT calculations and their corresponding UV-visible absorption spectra have been simulated. Concerning the open-shell complexes, the excitations in the low energy region of their spectra have been calculated to determine the coordination effect on the TTF to acceptor transitions of the ligand fragments. PMID:20092348

  14. Cryoscopic Studies of the Uranyl SulfateWater, Uranyl NitrateWater, and Uranyl NitrateNitric AcidWater Systems

    Microsoft Academic Search

    Alexander Apelblat

    1999-01-01

    Freezing point lowerings of aqueous solutions of uranyl sulfate in the concentration range m = 0.40 mol-kg-1 and the activity and osmotic coefficients, which were calculated using the Pitzer equations for 2:2 electrolytes, are presented. Crystallization temperatures are reported for 0 to 13 molar nitric acid and 10150 g uranium per liter uranyl nitratenitric acidwater solutions.

  15. 4f4f absorption spectra of nine-coordinate Pr (III) and Nd (III) complexes in different environments

    Microsoft Academic Search

    Azad A Khan; H. A Hussain; K Iftikhar

    2003-01-01

    Absorption spectroscopic studies on the mixed-ligand complexes of Pr (III) and Nd (III) with 2,2?-bipyridyl and thiocyanate in pyridine, DMSO, DMF and methanol are presented. The oscillator strengths for the hypersensitive and non-hypersensitive transitions have been calculated and variation in the oscillator strength and band shapes with respect to solvent type is rationalized in terms of solvent structures and coordinating

  16. Sustainable Coordination

    Microsoft Academic Search

    Martin Fredriksson; Rune Gustavsson; Alessandro Ricci

    2003-01-01

    Coordination, accounting for the global coherence of system behaviour, is a fundamental aspect of complex multi-agent systems.\\u000a As such, coordination in multi-agent systems provides a suitable level of abstraction to deal with system organisation and\\u000a control. However, current coordination approaches in multi-agent systems are not always fully equipped to model and support\\u000a the global coherence of open computational systems, i.e.,

  17. A protein carboxylate coordinated oxo-centered tri-nuclear iron complex with possible implications for ferritin mineralization.

    PubMed

    Hgbom, Martin; Nordlund, Pr

    2004-06-01

    The crystal structure of an oxo-centered tri-nuclear iron complex formed on a protein surface is presented. The cluster forms when crystals of the class Ib ribonucleotide reductase R2 protein from Corynebacterium ammoniagenes are subjected to iron soaking. The tri-iron-oxo complex is coordinated by protein-derived carboxylate ligands arranged in a motif similar to the one found on the inner surface of ferritins and may mimic an early stage in the mineralization of iron in ferritins. In addition, the structure adds to the very limited data on protein-mineral interfaces. PMID:15178319

  18. Redox cycling of copper-amyloid ? 1-16 peptide complexes is highly dependent on the coordination mode.

    PubMed

    Trujano-Ortiz, Lidia G; Gonzlez, Felipe J; Quintanar, Liliana

    2015-01-01

    Copper (Cu)-amyloid ? (A?) interactions play a role in the etiology of Alzheimer's disease. This work presents a spectroscopic and electrochemical study of two physiologically relevant A?-Cu(II) complexes, as a function of pH and relative Cu-A?(1-16) concentrations. Our results reveal that these coordination modes display distinct redox behaviors and provide experimental evidence for the existence of an intermediate Cu(I) species. A mechanism for the redox cycling of these complexes is proposed, providing further insight into the redox relevance of A?-Cu interactions. PMID:25521160

  19. Behavior of the potential antitumor V(IV)O complexes formed by flavonoid ligands. 1. Coordination modes and geometry in solution and at the physiological pH.

    PubMed

    Sanna, Daniele; Ugone, Valeria; Lubinu, Giuseppe; Micera, Giovanni; Garribba, Eugenio

    2014-11-01

    The coordination modes and geometry assumed in solution by the potent antitumor oxidovanadium(IV) complexes formed by different flavonoids were studied by spectroscopic (Electron Paramagnetic Resonance, EPR) and computational (Density Functional Theory, DFT) methods. A series of bidentate flavonoid ligands (L) with increasing structural complexity was examined, which can involve (CO, O(-)) donors and formation of five- and six-membered chelate rings, or (O(-), O(-)) donors and five-membered chelate rings. The geometry corresponding to these coordination modes can be penta-coordinated, [VOL2], or cis-octahedral, cis-[VOL2(H2O)]. The results show that, at physiological pH, ligands provided with (CO, O(-)) donor set yield cis-octahedral species with "maltol-like" coordination when five-membered chelate rings are formed (as with 3-hydroxyflavone), while penta-coordinated structures with "acetylacetone-like" coordination are preferred when the chelate rings are six-membered (as with chrysin). When both the binding modes are possible, as with morin, the "acetylacetone-like" coordination is observed. For the ligands containing a catecholic donor set, such as 7,8-dihydroxyflavone, baicalein, fisetin, quercetin and rutin, the formation of square pyramidal complexes with (O(-), O(-)) "catechol-like" coordination and five-membered chelate rings is preferred at physiological pH. The determination of the different coordination modes and geometry is important to define the biotransformation in the blood and the interaction of these complexes with the biological membranes. PMID:25127230

  20. Chemical speciation of the uranyl ion under alkaline conditions. Synthesis, structures, and oxo ligand exchange dynamics

    SciTech Connect

    Clark, D.L.; Conradson, S.D.; Donohoe, R.J.; Keogh, D.W.; Morris, D.E.; Palmer, P.D.; Tait, C.D. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States); Rogers, R.D. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States); [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Chemistry

    1999-04-05

    The aqueous chemistry of the uranyl(VI) ion (UO{sub 2}{sup 2+}) under acidic conditions is relatively well-known, and uranyl chemistry in near-neutral solutions has received considerable attention due to its importance in radioactive waste isolation and disposal. In contrast, aqueous solution chemistry of the uranyl ion under strongly alkaline conditions, such as those found in aging waste tanks within the DOE complex, is only poorly understood. The tetramethylammonium counterion was used to suppress formation of insoluble uranate salts, M{sub 2}U{sub 2}O{sub 7}, and allow for a detailed structural and spectroscopic characterization of UO{sub 2}(OH){sub n}{sup 2{minus}n} (n = 4, 5) under highly alkaline aqueous solution conditions. Single crystals of [Co(NH{sub 3}){sub 6}]{sub 2}[UO{sub 2}(OH){sub 4}]{sub 3}{center_dot}H{sub 2}O were obtained by cooling a dilute solution of Co(NH{sub 3}){sub 6}Cl{sub 3} and UO{sub 2}(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O in 3.5 M (Me{sub 4}N)OH to 5 C.

  1. Modulation of electronics and thermal stabilities of photochromic phosphino-aminoazobenzene derivatives in weak-link approach coordination complexes.

    PubMed

    Park, Jung Su; Lifschitz, Alejo M; Young, Ryan M; Mendez-Arroyo, Jose; Wasielewski, Michael R; Stern, Charlotte L; Mirkin, Chad A

    2013-11-13

    A series of d(8) transition-metal (Pt(II) and Pd(II)) coordination complexes incorporating phosphine-functionalized aminoazobenzene derivatives as hemilabile phosphino-amine (P,N) ligands were synthesized and studied as model weak-link approach (WLA) photoresponsive constructs. The optical and photochemical properties of these complexes were found to be highly influenced by various tunable parameters in WLA systems, which include type of metal, coordination mode, type of ancillary ligand, solvent, and outer-sphere counteranions. In dichloromethane, reversible chelation and partial displacement of the P,N coordinating moieties allow for toggling between aminoazobenzene- or pseudostilbene- and azobenzene-type derivatives. The reversible switching between electronic states of azobenzene can be controlled through either addition or extraction of chloride counterions and is readily visualized in the separation between ?-?* and n-?* bands in the complexes' electronic spectra. In acetonitrile solution, the WLA variables inherent to semiopen complexes have a significant impact on the half-lives of the corresponding cis isomers, allowing one to tune their half-lives from 20 to 21000 s, while maintaining photoisomerization behaviors with visible light. Therefore, one can significantly increase the thermal stability of a cis-aminoazobenzene derivative to the extent that single crystals for X-ray diffraction analysis can be grown for the first time, uncovering an unprecedented edge-to-face arrangement of the phenyl rings in the cis isomer. Overall, the azobenzene-functionalized model complexes shed light on the design parameters relevant for photocontrolled WLA molecular switches, as well as offer new ways of tuning the properties of azobenzene-based, photoresponsive materials. PMID:24187977

  2. Hydrothermal syntheses and structures of the uranyl tellurates AgUO{sub 2}(HTeO{sub 5}) and Pb{sub 2}UO{sub 2}(TeO{sub 6})

    SciTech Connect

    Ling, Jie; Ward, Matthew [Department of Civil Engineering and Geological Science, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.ed [Department of Civil Engineering and Geological Science, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2011-02-15

    Two uranyl tellurates, AgUO{sub 2}(HTeO{sub 5}) (1) and Pb{sub 2}UO{sub 2}(TeO{sub 6}) (2), were synthesized under hydrothermal conditions and were structurally, chemically, and spectroscopically characterized. 1 crystallizes in space group Pbca, a=7.085(2) A, b=11.986(3) A, c=13.913(4) A, V=1181.5(5) A{sup 3}, Z=8; 2 is in P2(1)/c, a=5.742(1) A, b=7.789(2) A, c=7.928(2) A, V=90.703(2) A{sup 3}, and Z=2. These are the first structures reported for uranyl compounds containing tellurate. The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions that are coordinated by O atoms to give pentagonal and square bipyramids in compounds 1 and 2, respectively. The structural unit in 1 is a sheet consisting of chains of edge-sharing uranyl pentagonal bipyramids that are one bipyramid wide, linked through the dimers of TeO{sub 6} octahedra. In 2, uranyl square bipyramids share each of their equatorial vertices with different TeO{sub 6} octahedra, giving a sheet with the autunite-type topology. Sheets in 1 and 2 are connected through the low-valence cations that are located in the interlayer region. The structures of 1 and 2 are compared to those of uranyl compounds containing octahedrally coordinated cations. -- Graphical abstract: Two hydrothermally synthesized uranyl tellurates, AgUO{sub 2}(HTeO{sub 5}) and Pb{sub 2}UO{sub 2}(TeO{sub 6}), contain sheets built from uranyl pentagonal or square bipyramids, as well as tellurate octahedra. Display Omitted Research highlights: > Compounds AgUO{sub 2}(HTeO{sub 5}) and Pb{sub 2}UO{sub 2}(TeO{sub 6}) are the first uranyl tellurate compounds. > The structure of AgUO{sub 2}(HTeO{sub 5}) consists of sheets of uranyl pentagonal bipyramids and TeO{sub 6} octahedra. > The structure of Pb{sub 2}UO{sub 2}(TeO{sub 6}) contains sheets of TeO{sub 6} octahedra and uranyl square bipyramids.

  3. Thermodynamic properties of autunite, uranyl hydrogen phosphate, and uranyl orthophosphate from solubility and calorimetric measurements

    SciTech Connect

    Gorman-Lewis, Drew; Shareva, Tatiana; kubatko, Karrie-Ann; burns, Peter; Wellman, Dawn M.; McNamara, Bruce K.; szymanowski, jennifer; Navrotsky, Alexandra; Fein, Jeremy B.

    2009-10-01

    In this study, we use solubility and oxide melt solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite (abbreviated: CaUP), uranyl hydrogen phosphate (HUP), and uranyl orthophosphate (UP). Solubility measurements from both supersaturated and undersaturated conditions, as well as under different pH conditions, rigorously demonstrate attainment of equilibrium and yield well-constrained solubility product values of -48.36 (-0.03 /+ 0.03), -13.17 (-0.11 / +0.07), and -49.36 (-0.04 / +0.02) for CaUP, HUP, and UP, respectively. We use the solubility data to calculate standard state Gibbs free energies of formation for all phases (-7630.61 9.69, -3072.27 4.76, and -6138.95 12.24 kJ mol-1 for CaUP, HUP, and UP, respectively), and calorimetry data to calculate standard state enthalpies of formation of -3223.22 4.00 and -7001.01 15.10 kJ mol-1 for HUP and UP, respectively. Combining these results allows us also to calculate the standard state entropies of formation of -506.54 10.48 and -2893.12 19.44 kJ mol-1 K-1 for HUP and UP phases, respectively. The results from this study are part of a combined effort to develop reliable and internally consistent thermodynamic data for environmentally relevant uranyl minerals. Data such as these are required in order to optimize and quantitatively assess the effect of phosphate amendment remediation technologies for uranium contaminated systems.

  4. Assessment of accidental intakes of uranyl acetylacetonate (UAA)

    SciTech Connect

    Fisher, D.R.; Briant, J.K.

    1993-12-01

    Uranyl acetylacetonate (UAA) is an organic complex of uranium used for military applications as a chemical catalyst in high explosives. It is prepared from depleted uranium metal (in lots of 5 kg to 7 kg) by dissolution in nitric acid, neutralization, and complexation with 2,4-pentanedione; the precipitate is dissolved in benzene and recrystallized, dried, ground, and packaged. About six workers at a small chemical company were exposed over a period of time to UAA powders during routine preparation and packaging of the uranium catalyst. The dissolution characteristics of the inhaled material were unknown and could not be determined from the published scientific literature. A 1.05-g sample of UAA powder was obtained from the responsible regulatory authority for further study to determine its chemical composition, and for dissolution in simulated lung fluid. We found the solubility of UAA to be equivalent to a mixture of 52% ICRP class D and 48% ICRP class W material. The annual limit on intake and the derived air concentration for radiological protection were estimated from this result for airborne exposure to UAA. A recycling biokinetic model was used to estimate both material-specific variations in urinary excretion rates and lung retention with time after accidental intakes. This study provides new information for evaluating future exposures to UAA.

  5. Automatic Method for Identifying Reaction Coordinates in Complex Systems Ao Ma and Aaron R. Dinner*

    E-print Network

    Dinner, Aaron

    a set of trajectories, each of which consists of a series of points in a many-dimensional phase space. To interpret these data and construct analytic theories that allow generalization and con- nection or by exhaustive exploration14,15 for only the simplest of systems. Consequently, the coordinates that provide

  6. Secondary Coordination Sphere Influence on the Reactivity of Nonheme Iron(II) Complexes: An Experimental and DFT Approach

    PubMed Central

    2013-01-01

    The new biomimetic ligands N4Py2Ph (1) and N4Py2Ph,amide (2) were synthesized and yield the iron(II) complexes [FeII(N4Py2Ph)(NCCH3)](BF4)2 (3) and [FeII(N4Py2Ph,amide)](BF4)2 (5). Controlled orientation of the Ph substituents in 3 leads to facile triplet spin reactivity for a putative FeIV(O) intermediate, resulting in rapid arene hydroxylation. Addition of a peripheral amide substituent within hydrogen-bond distance of the iron first coordination sphere leads to stabilization of a high-spin FeIIIOOR species which decays without arene hydroxylation. These results provide new insights regarding the impact of secondary coordination sphere effects at nonheme iron centers. PMID:23834409

  7. A new role for RINT-1 in SNARE complex assembly at the trans-Golgi network in coordination with the COG complex

    PubMed Central

    Arasaki, Kohei; Takagi, Daichi; Furuno, Akiko; Sohda, Miwa; Misumi, Yoshio; Wakana, Yuichi; Inoue, Hiroki; Tagaya, Mitsuo

    2013-01-01

    Docking and fusion of transport vesicles/carriers with the target membrane involve a tethering factormediated initial contact followed by soluble N-ethylmaleimidesensitive factor attachment protein receptor (SNARE)catalyzed membrane fusion. The multisubunit tethering CATCHR family complexes (Dsl1, COG, exocyst, and GARP complexes) share very low sequence homology among subunits despite likely evolving from a common ancestor and participate in fundamentally different membrane trafficking pathways. Yeast Tip20, as a subunit of the Dsl1 complex, has been implicated in retrograde transport from the Golgi apparatus to the endoplasmic reticulum. Our previous study showed that RINT-1, the mammalian counterpart of yeast Tip20, mediates the association of ZW10 (mammalian Dsl1) with endoplasmic reticulumlocalized SNARE proteins. In the present study, we show that RINT-1 is also required for endosome-totrans-Golgi network trafficking. RINT-1 uncomplexed with ZW10 interacts with the COG complex, another member of the CATCHR family complex, and regulates SNARE complex assembly at the trans-Golgi network. This additional role for RINT-1 may in part reflect adaptation to the demand for more diverse transport routes from endosomes to the trans-Golgi network in mammals compared with those in a unicellular organism, yeast. The present findings highlight a new role of RINT-1 in coordination with the COG complex. PMID:23885118

  8. Functional models for catechol dioxygenases: iron(III) complexes of cis-facially coordinating linear 3N ligands.

    PubMed

    Velusamy, Marappan; Mayilmurugan, Ramasamy; Palaniandavar, Mallayan

    2005-05-01

    A series of 1:1 iron(III) complexes of simple and sterically hindered tridentate 3N donor ligands have been synthesized and studied as functional models for catechol dioxygenases. All of them are of the type [FeLCl3], where L is bis(pyrid-2-yl-methyl)amine (L1), N,N-bis(benzimidazol-2-ylmethyl)amine (L2), N-methyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L3), N,N-dimethyl-N'-(pyrid-2-ylmethyl)-ethylenediamine (L4) and N-phenyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L5). They have been characterised by spectral and electrochemical methods. The X-ray crystal structure of the complex [Fe(L4)Cl3] has been successfully determined. The complex crystallizes in the triclinic space group P1 with a = 7.250(6), b = 8.284(3), c = 12.409(4) angstroms, alpha = 80.84(3) degrees, beta = 86.76(6) degrees, gamma = 72.09(7) degrees and Z = 2. It possesses a distorted octahedral geometry in which the L4 ligand is cis-facially coordinated to iron(III) and the chloride ions occupy the remaining coordination sites. The systematic variation in the ligand donor atom type significantly influences the Lewis acidity of the iron(III) center and hence the binding interaction of the complexes with simple and substituted catechols. The spectroscopic and electrochemical properties of the catecholate complexes generated in situ have been investigated. All the complexes catalyze mainly the oxidative intradiol cleavage of 3,5-di-tert-butylcatechol (H2DBC) in the presence of dioxygen, which is unexpected of the cis-facial coordination of the ligands. The rate of intradiol catechol cleavage reaction depends upon the Lewis acidity of iron(III) center and steric demand and hydrogen-bonding functionalities of the ligands. Interestingly, the electron-sink property of N-phenyl substituent in [Fe(L5)Cl3] complex leads to enhancement in rate of cleavage. All these observations provide support to the substrate activation mechanism proposed for intradiol-cleaving enzymes. PMID:15833326

  9. Uranyl Precipitation by Pseudomonas aeruginosa via Controlled Polyphosphate Metabolism

    PubMed Central

    Renninger, Neil; Knopp, Roger; Nitsche, Heino; Clark, Douglas S.; Keasling, Jay D.

    2004-01-01

    The polyphosphate kinase gene from Pseudomonas aeruginosa was overexpressed in its native host, resulting in the accumulation of 100 times the polyphosphate seen with control strains. Degradation of this polyphosphate was induced by carbon starvation conditions, resulting in phosphate release into the medium. The mechanism of polyphosphate degradation is not clearly understood, but it appears to be associated with glycogen degradation. Upon suspension of the cells in 1 mM uranyl nitrate, nearly all polyphosphate that had accumulated was degraded within 48 h, resulting in the removal of nearly 80% of the uranyl ion and >95% of lesser-concentrated solutions. Electron microscopy, energy-dispersive X-ray spectroscopy, and time-resolved laser-induced fluorescence spectroscopy (TRLFS) suggest that this removal was due to the precipitation of uranyl phosphate at the cell membrane. TRLFS also indicated that uranyl was initially sorbed to the cell as uranyl hydroxide and was then precipitated as uranyl phosphate as phosphate was released from the cell. Lethal doses of radiation did not halt phosphate secretion from polyphosphate-filled cells under carbon starvation conditions. PMID:15574942

  10. Reduction and selective oxo group silylation of the uranyl dication.

    PubMed

    Arnold, Polly L; Patel, Dipti; Wilson, Claire; Love, Jason B

    2008-01-17

    Uranium occurs in the environment predominantly as the uranyl dication [UO2]2+. Its solubility renders this species a problematic contaminant which is, moreover, chemically extraordinarily robust owing to strongly covalent U-O bonds. This feature manifests itself in the uranyl dication showing little propensity to partake in the many oxo group functionalizations and redox reactions typically seen with [CrO2]2+, [MoO2]2+ and other transition metal analogues. As a result, only a few examples of [UO2]2+ with functionalized oxo groups are known. Similarly, it is only very recently that the isolation and characterization of the singly reduced, pentavalent uranyl cation [UO2]+ has been reported. Here we show that placing the uranyl dication within a rigid and well-defined molecular framework while keeping the environment anaerobic allows simultaneous single-electron reduction and selective covalent bond formation at one of the two uranyl oxo groups. The product of this reaction is a pentavalent and monofunctionalized [O = U...OR]+ cation that can be isolated in the presence of transition metal cations. This finding demonstrates that under appropriate reaction conditions, the uranyl oxo group will readily undergo radical reactions commonly associated only with transition metal oxo groups. We expect that this work might also prove useful in probing the chemistry of the related but highly radioactive plutonyl and neptunyl analogues found in nuclear waste. PMID:18202653

  11. Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

    NASA Astrophysics Data System (ADS)

    Abou-Hussein, Azza A.; Linert, Wolfgang

    2014-01-01

    Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultraviolet-visible spectra, as well as 1H NMR spectra. Reactions of the Schiff bases ligands with ruthenium(III), oxovanadium(IV) and dioxouranium(VI) afforded the corresponding transition metal complexes. The properties of the newly prepared complexes were analyse by elemental analyses, infrared, electronic spectra, 1H NMR as well as the magnetic susceptibility and conductivity measurement. The metal complexes exhibits different geometrical arrangements such as octahedral and square pyramidal coordination. Schiff base ligands and their metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi to study their biological activity. All the complexes exhibit antibacterial and antifungal activities against these organisms.

  12. Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

    PubMed Central

    Abou-Hussein, Azza A.; Linert, Wolfgang

    2014-01-01

    Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultravioletvisible spectra, as well as 1H NMR spectra. Reactions of the Schiff bases ligands with ruthenium(III), oxovanadium(IV) and dioxouranium(VI) afforded the corresponding transition metal complexes. The properties of the newly prepared complexes were analyse by elemental analyses, infrared, electronic spectra, 1H NMR as well as the magnetic susceptibility and conductivity measurement. The metal complexes exhibits different geometrical arrangements such as octahedral and square pyramidal coordination. Schiff base ligands and their metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi to study their biological activity. All the complexes exhibit antibacterial and antifungal activities against these organisms. PMID:24070648

  13. Influence of the ligand frameworks on the coordination environment and properties of new phenylmercury(II) ?-oxodithioester complexes.

    PubMed

    Rajput, Gunjan; Yadav, Manoj Kumar; Drew, Michael G B; Singh, Nanhai

    2015-03-28

    New phenylmercury(II) complexes of the form [PhHg(L1), PhHg(L2) and PhHg(L3)] (L1 = methyl-3-hydroxy-3-(p-methoxyphenyl)-2-propenedithioate (1), L2 = methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (2) and L3 = methyl-3-hydroxy-(3-pyridyl)-2-propenedithioate (3)) have been synthesized and characterized by elemental analysis, IR, UV-Vis, 1H and 13C NMR. The crystal structures of 13 reveal a linear geometry about the mercury atom via ipso-C and S11 atoms. 1 and 2 exhibited O,S-coordination whereas 3 preferred S,S-coordination. Intramolecular Hg???O bonding interactions are also observed in 1 and 2 at distances of 2.638(14), 2.644(10) respectively. However in 3, incorporation of the 3-pyridyl substituent on the ligand enhanced the proximity of S13 and N14, giving rise to significant intramolecular Hg???S and intermolecular Hg???N interactions at 3.141(5) and 2.77(2) respectively generating a 1-D polymeric chain motif. The O,S- or S,S-coordination preference and Hg???N interactions have been assessed by DFT calculations. All the complexes show metal perturbed ligand-centred luminescence characteristics in solution and in the solid phase. The band gap values 2.54, 2.66 and 2.61 eV for 1, 2 and 3, respectively, evaluated from the diffuse reflectance spectroscopy show the semiconducting nature of the complexes. PMID:25720560

  14. Multiagent Coordination Techniques for Complex Environments: The Case of a Fleet of Combat Ships

    Microsoft Academic Search

    Patrick Beaumont; Brahim Chaib-draa

    2007-01-01

    The use of agent and multiagent techniques to assist humans in their daily routines has been increasing for many years, notably in Command and Control (C2) systems. In this context, we propose using multiagent planning and coordination techniques for resources management in real-time C2 systems. The particular problem we studied is the design of a decision-support for Anti-Air Warfare (AAW)

  15. Synthesis, coordination behavior, and investigations of pharmacological effects of some transition metal complexes with isoniazid Schiff bases

    Microsoft Academic Search

    Krishna K. Sharma; Ritu Singh; Nighat Fahmi; R. V. Singh

    2010-01-01

    Two isoniazid Schiff bases, N-isonicotinamido-2-furanketimine (INH-F) and N-isonicotinamido-5-methyl-2-furanketimine (INH-F), possessing potential N and O coordination sites have been prepared by the reaction of isoniazid with 2-acetylfuran and 2-acetyl-5-methylfuran, respectively. Complexes of Pd(II) and Pt(II) have been prepared and characterized by elemental analyses, melting point determinations and electronic, infrared, H NMR, C NMR spectral studies, and X-ray powder diffraction studies. In

  16. Modeling the magnetic properties of lanthanide complexes: relationship of the REC parameters with Pauling electronegativity and coordination number.

    PubMed

    Baldov, Jos J; Gaita-Ario, Alejandro; Coronado, Eugenio

    2015-07-01

    In a previous study, we introduced the Radial Effective Charge (REC) model to study the magnetic properties of lanthanide single ion magnets. Now, we perform an empirical determination of the effective charges (Zi) and radial displacements (Dr) of this model using spectroscopic data. This systematic study allows us to relate Dr and Zi with chemical factors such as the coordination number and the electronegativities of the metal and the donor atoms. This strategy is being used to drastically reduce the number of free parameters in the modeling of the magnetic and spectroscopic properties of f-element complexes. PMID:26105010

  17. Sliding Autonomy for Complex Coordinated Multi-Robot Tasks: Analysis & Experiments

    E-print Network

    Singh, Sanjiv

    results support both our expectations and modeling and show that our combined robot-human team is able of complex tasks, such as the assembly of large structures by a team of robots. Here we introduce an approach the abilities of any single robot of manageable complexity. One approach to this problem is to use teams

  18. The S. Cerevisiae HAP Complex, a Key Regulator of Mitochondrial Function, Coordinates Nuclear and Mitochondrial Gene Expression

    PubMed Central

    Buschlen, S.; Amillet, J-M; Guiard, B.; Fournier, A.; Marcireau, C.

    2003-01-01

    We have compared Saccharomyces cerevisiae global gene expression in wild-type and mutants (?hap2 and ?hap4) of the HAP transcriptional complex, which has been shown to be necessary for growth on respiratory substrates. Several hundred ORFs are under positive or negative control of this complex and we analyse here in detail the effect of HAP on mitochondria. We found that most of the genes upregulated in the wild-type strain were involved in organelle functions, but practically none of the downregulated ones. Nuclear genes encoding the different subunits of the respiratory chain complexes figure in the genes more expressed in the wild-type than in the mutants, as expected, but in this group we also found key components of the mitochondrial translation apparatus. This control of mitochondrial translation may be one of the means of coordinating mitochondrial and nuclear gene expression in elaborating the respiratory chain. In addition, HAP controls the nuclear genes involved in several other mitochondrial processes (import, mitochondrial division) that define the metabolic state of the cell, but not mitochondrial DNA replication and transcription. In most cases, a putative CCAAT-binding site is present upstream of the ORF, while in others no such sites are present, suggesting the control to be indirect. The large number of genes regulated by the HAP complex, as well as the fact that HAP also regulates some putative transcriptional activators of unknown function, place this complex at a hierarchically high position in the global transcriptional regulation of the cell. PMID:18629096

  19. Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes

    SciTech Connect

    Andersen, Richard; Walter, Marc D.; Berg, David J.; Andersen, Richard A.

    2006-11-04

    The paramagnetic 1:1 coordination complexes of (C5Me5)2Yb with a series of diazabutadiene ligands, RN=C(R')C(R')=NR, where R= CMe3, CHMe2, adamantyl, p-tolyl, p-anisyl, and mesityl when R'=H, and R= p-anisyl when R'= Me, have been prepared. The complexes are paramagnetic, but their magnetic moments are less than expected for the two uncoupled spin carriers, (C5Me5)2Yb(III, 4f13) and the diazabutadiene radical anions (S=1/2), which implies exchange coupling between the spins. The variable temperature 1H NMR spectra show that rotation about the R-N bond is hindered and these barriers are estimated. The barriers are largely determined by steric effects but electronic effects are not unimportant.

  20. Extraction of uranyl, La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylamine

    Microsoft Academic Search

    A. K. Pyartman; V. V. Lishchuk; V. A. Keskinov

    2007-01-01

    Extraction of uranyl, La(III), and Y(III) nitrates from aqueous solutions containing 04 M sodium nitrate with a composite\\u000a solid extractant based on a polymeric support impregnated with trialkylamine (C7-C9) was studied. The extraction isotherms were analyzed assuming that La(III), Y(III), and uranyl nitrates are extracted with\\u000a the solid extractant in the form of complexes (R3NH)3[Ln(NO3)6] and (R3NH)2[UO2(NO3)4], respectively. The extraction

  1. Extraction of uranyl, La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate

    Microsoft Academic Search

    A. K. Pyartman; V. A. Keskinov; V. V. Lishchuk; A. V. Konstantinova; V. V. Belova

    2007-01-01

    Extraction of uranyl, La(III), and Y(III) nitrates from aqueous solutions containing 04 M sodium nitrate with a composite\\u000a solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate (Aliquat-336) was studied. The\\u000a extraction isotherms were analyzed assuming that uranyl, La(III), and Y(III) nitrates are extracted with the solid extractant\\u000a in the form of complexes (R4N)2[Ln(NO3)5] and (R4N)2[UO2(NO3)4], respectively. The

  2. Complex regulatory pathways coordinate cell cycle progression and development in Caulobacter crescentus

    PubMed Central

    Brown, Pamela J.B.; Hardy, Gail G.; Trimble, Michael J.; Brun, Yves V.

    2008-01-01

    Caulobacter crescentus has become the predominant bacterial model system to study the regulation of cell cycle progression. Stage specific processes such as chromosome replication and segregation, and cell division are coordinated with the development of four polar structures: the flagellum, pili, stalk, and holdfast. The production, activation, localization, and proteolysis of specific regulatory proteins at precise times during the cell cycle culminate in the ability of the cell to produce two physiologically distinct daughter cells. We examine the recent advances that have enhanced our understanding of the mechanisms of temporal and spatial regulation that occur during cell cycle progression. PMID:18929067

  3. Polymer complexes: XLXII-interplay of coordination ?-? stacking and hydrogen bonding in supramolecular assembly of [sulpha drug derivatives-N,S:N,O] complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; Diab, M. A.; El-Halawany, M. M.; Salam, N. E.

    2010-11-01

    A novel series of nickel(II) polymer complexes of 5-sulphadiazineazo-3-phenylamino-2-thio-4-thiazolidinone (HL 1), 5-sulphamethazine-3-phenylamino-2-thioxo-4-thiazolidinone (HL 2), 5-sulphamethoxazole-3-phenylamino-2-thioxo-4-thiazolidinone (HL 3), 5-sulphacetamide-3-phenyl-2-thioxo-4-thiazolidinone (HL 4) and 5-sulphaguanidine-3-phenylamino-2-thioxo-4-thiazolidinone (HL 5) were prepared and characterized. IR spectra show that HL n ( n = 1-5) is coordinated to the metal ion in a neutral tetradentate manner with NSNO donor sites of NH (hydrazone's), NH (3-phenylamine), carbonyl group and Ph-NH. The title [Ni 3(HL n) 2(?-OAc) 2(OAc) 4] n consists of three Ni(II) atoms linked by interchain ?-? interaction are observed between aromatic rings of two ligands (HL n) which are further doubly bridged two adjacent nickel atoms by acetate group. The geometrical structures of these complexes are found to be octahedral. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, thermal, infrared, 1H NMR, electronic spectra, magnetic susceptibility and conductivity measurements. The richness of electronic spectral in these complexes is also supporting evidence for the trinuclearity of the Ni(II) polymer complexes.

  4. A novel hemilabile calix[4],quinoline-based P,N-ligand: coordination chemistry and complex characterisation.

    PubMed

    Marson, Angelica; Ernsting, Johanneke E; Lutz, Martin; Spek, Anthony L; van Leeuwen, Piet W N M; Kamer, Paul C J

    2009-01-28

    The synthesis of the calix[4]arene-based P,N-ligand 3 (5,11,17,23-tetra-tert-butyl-25-[(2-quinolylmethyl)oxy]-26,27,28-(mu3-phosphorustrioxy)calix[4]arene), in which the nitrogen atom-containing moiety has been introduced at the lower rim of the cavity prior to P-functionalisation, is described and its coordination properties investigated. In the crystal structure, the calix[4]-cavity adopts a cone conformation with an exo orientation of the phosphorus lone pair enabling P-N chelation. 1H, 13C, 31P and 1H{15N} HMQC NMR spectra indicated that, in complexes [PdCl(CH3)(3)] (4) and [Rh(CO)Cl(3)] (5), ligand 3 coordinates in a chelating fashion, while in cis-[PtC12(3)2] (6) and [Rh(acac)(CO)(3)] (7) it behaves as a monodentate ligand, coordinating via the phosphorus atom only. X-Ray crystal structure determinations were performed for [PdCl(CH3)(3)] (4) and cis-[PtCl2(3)2] (6). The cationic Pd complex [Pd(CH3)(CH3CN)(3)][PF5] (8) was found to be active in a CO/ethylene copolymerisation reaction. Good selectivities were observed for the Pd-catalysed allylic alkylation of cinnamyl acetate with in situ prepared catalysts. [Rh(acac)(CO)2] modified with ligand 3 catalyses the hydroformylation of 1-octene with low selectivities towards linear aldehydes. High-pressure NMR experiments on the hydrido carbonyl rhodium(3) were inconclusive, different species were formed. PMID:19378555

  5. Aging induced loss of complexity and dedifferentiation: consequences for coordination dynamics within and between brain, muscular and behavioral levels.

    PubMed

    Sleimen-Malkoun, Rita; Temprado, Jean-Jacques; Hong, S Lee

    2014-01-01

    Growing evidence demonstrates that aging not only leads to structural and functional alterations of individual components of the neuro-musculo-skeletal system (NMSS) but also results in a systemic re-organization of interactions within and between the different levels and functional domains. Understanding the principles that drive the dynamics of these re-organizations is an important challenge for aging research. The present Hypothesis and Theory paper is a contribution in this direction. We propose that age-related declines in brain and behavior that have been characterized in the literature as dedifferentiation and the loss of complexity (LOC) are: (i) synonymous; and (ii) integrated. We argue that a causal link between the aforementioned phenomena exists, evident in the dynamic changes occurring in the aging NMSS. Through models and methods provided by a dynamical systems approach to coordination processes in complex living systems, we: (i) formalize operational hypotheses about the general principles of changes in cross-level and cross-domain interactions during aging; and (ii) develop a theory of the aging NMSS based on the combination of the frameworks of coordination dynamics (CD), dedifferentiation, and LOC. Finally, we provide operational predictions in the study of aging at neural, muscular, and behavioral levels, which lead to testable hypotheses and an experimental agenda to explore the link between CD, LOC and dedifferentiation within and between these different levels. PMID:25018731

  6. Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes

    SciTech Connect

    Rao, Linfeng; Tian, Guoxin

    2008-12-10

    Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55 and 70 C) by spectrophotometry and microcalorimetry. The NdNO{sub 3}{sup 2+} complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 C was determined by microcalorimetry to be small and positive, (1.5 {+-} 0.2) kJ {center_dot} mol{sup -1}, in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) and nitrate in aqueous solutions. Specific Ion Interaction approach (SIT) was used to obtain the stability constants of NdNO{sub 3}{sup 2+} at infinite dilution and variable temperatures.

  7. Synthesis, structures and properties of a series of manganese coordination complexes constructed from dicarboxylic fluorene derivatives

    SciTech Connect

    Li Xing, E-mail: lixing@nbu.edu.cn [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211 (China); Zhao Xiuhua; Bing Yue; Zha Meiqin; Xie Hongzhen; Guo Zhiyong [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211 (China)

    2013-01-15

    Assembly reactions of 9,9-diethylfluorene-2,7-dicarboxylic acid (H{sub 2}DFDC) and Mn(CH{sub 3}COO){sub 2}{center_dot}4H{sub 2}O or MnCl{sub 2}{center_dot}4H{sub 2}O by tuning of various secondary ligands such as 2,2 Prime -bipyridine (2,2 Prime -bpy), 4,4 Prime -bipyridine (4,4 Prime -bpy) or 1,3-bis(4-pyridyl)propane) (bpp), gave rise to four complexes {l_brace} [Mn{sub 2}(DFDC){sub 2}(DMF){sub 2}]{center_dot}H{sub 2}O{r_brace} {sub n} (1), [Mn(DFDC)(2,2 Prime -bpy)]{sub n} (2), {l_brace} [Mn{sub 2}(DFDC){sub 2}(4,4 Prime -bpy){sub 2}]{center_dot}2CH{sub 3}OH{r_brace} {sub n} (3), and {l_brace} [Mn{sub 4}(DFDC){sub 4}(bpp){sub 2}(CH{sub 3}OH){sub 3} (H{sub 2}O){sub 3}]{center_dot}3(CH{sub 3}OH){center_dot}3(H{sub 2}O){r_brace} {sub n} (4). Single crystal X-ray diffraction analysis reveal that complex 1 is three dimensional structure with rhombic channels filled by guest water molecules; 2 presents a close-packed structure with high thermal stability; 3 exhibits a three dimensional framework with micro-porous channels filled by guest methanol molecules and 4 is a two-dimensional structure. The photoluminescent properties of 1-4 have been studied, respectively, showing that the Mn(II) ions, accessorial organic ligands or crystal structures exert important influences on the photoluminescence emissions of H{sub 2}DFDC ligands. Thermogravimetric analysis show that the complexes have remarkably high thermal stability. Magnetic susceptibility measurements have been finished and discussed for the complexes. - Graphical abstract: Assembly of 9,9-diethylfluorene-2,7-dicarboxylic acid and Mn(II) salts by tuning of various accessorial ligands resulted in four manganese complexes with different topological frameworks. Highlights: Black-Right-Pointing-Pointer Four manganese complexes based on 9,9-diethylfluorene-2,7-dicarboxylic acid were obtained. Black-Right-Pointing-Pointer The complexes were structurally characterized by single-crystal X-ray diffraction. Black-Right-Pointing-Pointer The complexes 1-4 display different topological structures. Black-Right-Pointing-Pointer Thermogravimetric analysis show the complexes have remarkably high thermal stability.

  8. Multispecies diffusion models: A study of uranyl species diffusion

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-14

    Rigorous numerical description of multi-species diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication for imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multi-species diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multi-species diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multi-species U(VI) diffusion under steady-state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that a fully coupled diffusion model can be well approximated by a component-based diffusion model, which considers difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be rigorously enforced, if necessary, by adding an artificial kinetic reaction term induced by the charge separation. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from US Department of Energy's Hanford 300A where intragrain diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that has been described using a semi-empirical, multi-rate model. Compared with the multi-rate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

  9. Hydrothermal Phase Relations Among Uranyl Minerals at the Nopal I Analog Site

    SciTech Connect

    Murphy, William M. [Geological and Environmental Sciences, California State University, Chico, CA, 95929 (United States)

    2007-07-01

    Uranyl mineral paragenesis at Nopal I is an analog of spent fuel alteration at Yucca Mountain. Petrographic studies suggest a variety of possible hydrothermal conditions for uranium mineralization at Nopal I. Calculated equilibrium phase relations among uranyl minerals show uranophane stability over a broad range of realistic conditions and indicate that uranyl mineral variety reflects persistent chemical potential heterogeneity. (author)

  10. Metal ion as both a cofactor and a probe of metal-binding sites in a uranyl-specific DNAzyme: a uranyl photocleavage study

    PubMed Central

    Cepeda-Plaza, Marjorie; Null, Eric L.; Lu, Yi

    2013-01-01

    DNAzymes are known to bind metal ions specifically to carry out catalytic functions. Despite many studies since DNAzymes were discovered nearly two decades ago, the metal-binding sites in DNAzymes are not fully understood. Herein, we adopt uranyl photocleavage to probe specific uranyl-binding sites in the 39E DNAzyme with catalytically relevant concentrations of uranyl. The results indicate that uranyl binds between T23 and C25 in the bulge loop, G11 and T12 in the stem loop of the enzyme strand, as well as between T2.4 and G3 close to the cleavage site in the substrate strand. Control experiments using two 39E DNAzyme mutants revealed a different cleavage pattern of the mutated region. Another DNAzyme, the 817 DNAzyme, which has a similar secondary structure but shows no activity in the presence of uranyl, indicated a different uranyl-dependent photocleavage as well. In addition, a close correlation between the concentration-dependent photocleavage and enzymatic activities is also demonstrated. Together, these experiments suggest that uranyl photocleavage has been successfully used to probe catalytically relevant uranyl-binding sites in the 39E DNAzyme. As uranyl is the cofactor of the 39E DNAzyme as well as the probe, specific uranyl binding has now been identified without disruption of the structure. PMID:23939617

  11. DOI: 10.1002/anie.200905797 Synthesis and Properties of a Fifteen-Coordinate Complex: The

    E-print Network

    Girolami, Gregory S.

    ] The complexes tetrakis(cyclopentadienyl)uranium [UCp4] and its thorium analogue [ThCp4] are each connected to 20 be considered as a separate bond. Accordingly, [Zr(BH4)4],[1517] [Hf(BH4)4],[15,16,18] [Np- (BH4

  12. School Nurses and Care Coordination for Children with Complex Needs: An Integrative Review

    ERIC Educational Resources Information Center

    McClanahan, Rachel; Weismuller, Penny C.

    2015-01-01

    Health care for students with chronic needs can be complex and specialized, resulting in fragmentation, duplication, and inefficiencies. Students who miss school due to chronic conditions lose valuable educational exposure that contributes to academic success. As health-related disabilities increase in prevalence so does the need for the

  13. Reactivity of coordinatively unsaturated bis(N-heterocyclic carbene) Pt(II) complexes toward H(2). Crystal structure of a 14-electron Pt(II) hydride complex.

    PubMed

    Rivada-Wheelaghan, Orestes; Rosell-Merino, Marta; Ortuo, Manuel A; Vidossich, Pietro; Gutirrez-Puebla, Enrique; Lleds, Agust; Conejero, Salvador

    2014-04-21

    The reactivity toward H2 of coordinatively unsaturated Pt(II) complexes, stabilized by N-heterocyclic carbene (NHC) ligands, is herein analyzed. The cationic platinum complexes [Pt(NHC')(NHC)](+) (where NHC' stands for a cyclometalated NHC ligand) react very fast with H2 at room temperature, leading to hydrogenolysis of the Pt-CH2 bond and concomitant formation of hydride derivatives [PtH(NHC)2](+) or hydrido-dihydrogen complexes [PtH(H2)(NHC)2](+). The latter species release H2 when these compounds are subjected to vacuum. The X-ray structure of complex [PtH(IPr)2][SbF6] revealed its unsaturated nature, exhibiting a true T-shaped structure without stabilization by agostic interactions. Density functional theory calculations indicate that the binding and reaction of H2 in complexes [PtH(H2)(NHC)2](+) is more favored for derivatives bearing aryl-substituted NHCs (IPr, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene and IMes = 1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene) than for those containing tert-butyl groups (I(t)Bu). This outcome is related to the higher close-range steric effects of the I(t)Bu ligands. Accordingly, H/D exchange reactions between hydrides [PtH(NHC)2](+) and D2 take place considerably faster for IPr and IMes* derivatives than for I(t)Bu ones. The reaction mechanisms for both H2 addition and H/D exchange processes depend on the nature of the NHC ligand, operating through oxidative addition transition states in the case of IPr and IMes* or by a ?-complex assisted-metathesis mechanism in the case of I(t)Bu. PMID:24716606

  14. Care Coordination for Children with Complex Special Health Care Needs: The Value of the Advanced Practice Nurses Enhanced Scope of Knowledge and Practice

    PubMed Central

    Looman, Wendy S.; Presler, Elizabeth; Erickson, Mary M.; Garwick, Ann E.; Cady, Rhonda G.; Kelly, Anne M.; Finkelstein, Stanley M.

    2012-01-01

    Efficiency and effectiveness of care coordination depends on a match between the needs of the population and the skills, scope of practice, and intensity of services provided by the care coordinator. There is limited existing literature that addresses the relevance of the APN role as a fit for coordination of care for children with SHCN. The objective of this paper is to describe the value of the advanced practice nurses (APNs) enhanced scope of knowledge and practice for relationship-based care coordination in healthcare homes that serve children with complex special health care needs (SHCN). The TeleFamilies project is provided as an example of the integration of an APN care coordinator in a healthcare home for children with SHCN. PMID:22560803

  15. Care coordination for children with complex special health care needs: the value of the advanced practice nurse's enhanced scope of knowledge and practice.

    PubMed

    Looman, Wendy S; Presler, Elizabeth; Erickson, Mary M; Garwick, Ann W; Cady, Rhonda G; Kelly, Anne M; Finkelstein, Stanley M

    2013-01-01

    Efficiency and effectiveness of care coordination depends on a match between the needs of the population and the skills, scope of practice, and intensity of services provided by the care coordinator. Existing literature that addresses the relevance of the advanced practice nurse (APN) role as a fit for coordination of care for children with special health care needs (SHCN) is limited. The objective of this article is to describe the value of the APN's enhanced scope of knowledge and practice for relationship-based care coordination in health care homes that serve children with complex SHCN. The TeleFamilies project is provided as an example of the integration of an APN care coordinator in a health care home for children with SHCN. PMID:22560803

  16. Ligand and coordination-plane distortions in platinum(II) complexes of isomers of dimethyl-2,2'-bipyridine.

    PubMed

    Maheshwari, Vidhi; Carlone, Maria; Fronczek, Frank R; Marzilli, Luigi G

    2007-08-01

    Pseudo-square-planar platinum(II) complexes containing 4,4' (4,4'-Me(2)bipy), 5,5' (5,5'-Me(2)bipy) and 6,6' (6,6'-Me(2)bipy) isomers of dimethyl-2,2'-bipyridine (Me(2)bipy) were synthesized and structurally characterized to assess the effects of methyl-group position on structure. The Pt-N distances in (Me(2)bipy)PtCl(2) complexes fall in the typical range [2.017 (3)-2.032 (3) Angstroms]. Only minor distortions such as 2.4 and 5.5 degrees twisting of the two pyridyl rings in (4,4'-Me(2)bipy)PtCl(2) (I) and (5,5'-Me(2)bipy)PtCl(2) (II), respectively, occur. However, (6,6'-Me(2)bipy)PtCl(2) (III) is highly distorted: the two pyridyl rings in (III) have a large bowing angle (theta(B)) of 19.2 degrees . The presence of distortions in (III), but not in (I) and (II), is attributed to repulsions between the 6,6'-methyl groups and the cis chloro ligands. [(4,4'-Me(2)bipy)(2)Pt](BF(4))(2) (IV) undergoes a bow-incline deformation having a large theta(B) value (24.2 degrees), and the ligands are inclined relative to the coordination plane by 18.80 (13) degrees. Complex (IV) joins a small list of distorted bis-bipyridine complexes; this finding can be attributed to the unfavorable repulsions between the 6,6' hydrogen substituents of opposing ligands. Some of these complexes exhibit canting rather than bow-incline distortion, a trend suggesting that subtle solid-state effects determine the nature of the distortion. PMID:17641431

  17. Investigations of iron coordination and redox reactions in seawater using 59Fe radiometry and ion-pair solvent extraction of amphiphilic iron complexes

    Microsoft Academic Search

    Robert J. M. Hudson; Dianne T. Covault; Francois M. M. Morel

    1992-01-01

    Hudson, R.J.M., Covault, D.T. and Morel, F.M.M., 1992. Investigations of iron coordination and redox reactions in seawater using 59Fe radiometry and ion-pair solvent extraction of amphiphilic iron complexes. Mar. Chem., 38: 209-235. Iron coordination and redox reactions in synthetic and coastal seawater were investigated at na- nomolar concentrations using 59Fe radiometry and ion-pair solvent extraction of iron chelated by sulfoxine

  18. Coordinated regulation of transcriptional repression by the RBP2 H3K4 demethylase and Polycomb-Repressive Complex 2.

    PubMed

    Pasini, Diego; Hansen, Klaus H; Christensen, Jesper; Agger, Karl; Cloos, Paul A C; Helin, Kristian

    2008-05-15

    Polycomb group (PcG) proteins regulate important cellular processes such as embryogenesis, cell proliferation, and stem cell self-renewal through the transcriptional repression of genes determining cell fate decisions. The Polycomb-Repressive Complex 2 (PRC2) is highly conserved during evolution, and its intrinsic histone H3 Lys 27 (K27) trimethylation (me3) activity is essential for PcG-mediated transcriptional repression. Here, we show a functional interplay between the PRC2 complex and the H3K4me3 demethylase Rbp2 (Jarid1a) in mouse embryonic stem (ES) cells. By genome-wide location analysis we found that Rbp2 is associated with a large number of PcG target genes in mouse ES cells. We show that the PRC2 complex recruits Rbp2 to its target genes, and that this interaction is required for PRC2-mediated repressive activity during ES cell differentiation. Taken together, these results demonstrate an elegant mechanism for repression of developmental genes by the coordinated regulation of epigenetic marks involved in repression and activation of transcription. PMID:18483221

  19. Coordinated regulation of transcriptional repression by the RBP2 H3K4 demethylase and Polycomb-Repressive Complex 2

    PubMed Central

    Pasini, Diego; Hansen, Klaus H.; Christensen, Jesper; Agger, Karl; Cloos, Paul A.C.; Helin, Kristian

    2008-01-01

    Polycomb group (PcG) proteins regulate important cellular processes such as embryogenesis, cell proliferation, and stem cell self-renewal through the transcriptional repression of genes determining cell fate decisions. The Polycomb-Repressive Complex 2 (PRC2) is highly conserved during evolution, and its intrinsic histone H3 Lys 27 (K27) trimethylation (me3) activity is essential for PcG-mediated transcriptional repression. Here, we show a functional interplay between the PRC2 complex and the H3K4me3 demethylase Rbp2 (Jarid1a) in mouse embryonic stem (ES) cells. By genome-wide location analysis we found that Rbp2 is associated with a large number of PcG target genes in mouse ES cells. We show that the PRC2 complex recruits Rbp2 to its target genes, and that this interaction is required for PRC2-mediated repressive activity during ES cell differentiation. Taken together, these results demonstrate an elegant mechanism for repression of developmental genes by the coordinated regulation of epigenetic marks involved in repression and activation of transcription. PMID:18483221

  20. Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 resolution

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng; Morais-Cabral, Joo H.; Kaufman, Amelia; MacKinnon, Roderick

    2001-11-01

    Ion transport proteins must remove an ion's hydration shell to coordinate the ion selectively on the basis of its size and charge. To discover how the K+ channel solves this fundamental aspect of ion conduction, we solved the structure of the KcsA K+ channel in complex with a monoclonal Fab antibody fragment at 2.0 resolution. Here we show how the K+ channel displaces water molecules around an ion at its extracellular entryway, and how it holds a K+ ion in a square antiprism of water molecules in a cavity near its intracellular entryway. Carbonyl oxygen atoms within the selectivity filter form a very similar square antiprism around each K+ binding site, as if to mimic the waters of hydration. The selectivity filter changes its ion coordination structure in low K+ solutions. This structural change is crucial to the operation of the selectivity filter in the cellular context, where the K+ ion concentration near the selectivity filter varies in response to channel gating.

  1. Pyro without fire: synthesis, structure, and reactivity of a dimeric vanadyl pyrophosphate coordination complex.

    PubMed

    Marino, Nadia; Hanson, Susan K; Mller, Peter; Doyle, Robert P

    2012-10-01

    The complex {[(V(IV)O)bipy(H(2)O)](2)(?-P(2)O(7))}3H(2)O (2) was readily obtained as a nanocrystalline powder by one-pot synthesis under mild conditions. Single crystals of 2 were grown at room temperature over 2 months, and its structure was determined. Fundamental catalytic activity was proven for this species by testing for oxidation of benzyl alcohol in air. PMID:22974202

  2. Evaluation of chiral recognition ability of a novel uranyl-salophen-based receptor: an easy and rapid testing protocol.

    PubMed

    Dalla Cort, Antonella; Murua, Jos Ignacio Miranda; Pasquini, Chiara; Pons, Miquel; Schiaffino, Luca

    2004-07-01

    A novel member of a new class of chiral uranyl-salophen complexes has been synthesised. The chiral recognition ability of this receptor toward the enantiomers of two primary amines, a sulfoxide, and a quaternary ammonium chloride has been evaluated for the first time. The enantioselectivities obtained are encouraging. The NMR method developed for this purpose allows a fast, quantitative determination of the enantioselectivity of the host directly from its racemic mixture and could find application as a preliminary screening tool in the search for new receptors using combinatorial methods. The experiments carried out in this context demonstrated also that the activation barrier for the racemisation of such chiral uranyl-salophen receptors is much higher than the lower limit of 21 kcal mol(-1) previously reported. PMID:15224339

  3. Syntheses and characterization of novel lanthanide adamantine-dicarboxylate coordination complexes

    SciTech Connect

    Li Xing; Wei Danyi; Huang Shijie [Institute of Solid Materials Chemistry, State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211 (China); Zheng Yueqing [Institute of Solid Materials Chemistry, State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211 (China)], E-mail: zhengyueqing@nbu.edu.cn

    2009-01-15

    Hydrothermal reactions of 1,10-phenanthroline (phen), 1,3-adamantanedicarboxylic acid (H{sub 2}L) and lanthanide chlorides yielded six compounds: [Ln(L)(HL)(phen)] (Ln=Pr, 1; Nd, 2), [Ln(L)(HL)(phen)(H{sub 2}O)] (Sm, 3; Eu, 4), [Tb(L)(HL)(phen)(H{sub 2}O)]{sub 2}.2H{sub 2}O (5), [Er{sub 3}(L){sub 4}(OH)(phen)]{sub 2} (6). Compounds 1-4 are structurally featured by one-dimensional polymeric chains; 5 hold binuclear structure constructed from eight-coordinated lanthanide center LnN{sub 2}O{sub 6} of distorted bicapped trigonal prism bridged by dicarboxylate ligands; 6 shows that erbium ions are in mono and bicapped trigonal prismatic geometries, respectively, which are further connected by {mu}{sub 3}-OH to give rise to trinuclear structure. Thermogravimetric analyses of 1, 3 and 5 were performed. Fluorescent measurements of 4 and 5 were carried out, respectively. - Grapical Abstract: Hydrothermal reactions of 1,10-phenanthroline, 1,3-adamantanedicarboxylic acid and lanthanide choloride yielded a novel supramolecular architectures constructed from polyhedral LnN{sub 2}O{sub 6} of distorted bicapped trigonal prism bridged by dicarboxylate.

  4. Iron Complexes for the Electrocatalytic Oxidation of Hydrogen: Tuning Primary and Secondary Coordination Spheres

    SciTech Connect

    Darmon, Jonathan M.; Raugei, Simone; Liu, Tianbiao L.; Hulley, Elliott B.; Weiss, Charles J.; Bullock, R. Morris; Helm, Monte L.

    2014-04-04

    A series of iron hydride complexes featuring PRNR'PR (PRNR'PR = R2PCH2N(R')CH2PR2 where R = Ph, R' = Me; R = Et, R' = Ph, Bn, Me, tBu) and cyclopentadienyl (CpX = C5H4X where X = H, C5F4N) ligands has been synthesized, characterized by NMR spectroscopy, X-ray diffraction and cyclic voltammetry, and examined by quantum chemistry calculations. Each compound was tested for the electrocatalytic oxidation of H2 and the most active complex, (CpC5F4N)Fe(PEtNMePEt)(H), exhibited a turnover frequency of 8.6 s-1 at 1 atm of H2 with an overpotential of 0.41 V, as measured from the half peak potential of the catalytic wave. Control complexes that do not contain pendant amine groups were also prepared and characterized, but no catalysis was observed. This work demonstrates the importance of the pendant amine in facilitating heterolytic H2 cleavage and subsequent proton movement necessary for electrocatalytic H2 oxidation. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  5. The MRN complex: coordinating and mediating the response to broken chromosomes.

    PubMed

    van den Bosch, Michael; Bree, Ronan T; Lowndes, Noel F

    2003-09-01

    The MRE11-RAD50-NBS1 (MRN) protein complex has been linked to many DNA metabolic events that involve DNA double-stranded breaks (DSBs). In vertebrate cells, all three components are encoded by essential genes, and hypomorphic mutations in any of the human genes can result in genome-instability syndromes. MRN is one of the first factors to be localized to the DNA lesion, where it might initially have a structural role by tethering together, and therefore stabilizing, broken chromosomes. This suggests that MRN could function as a lesion-specific sensor. As well as binding to DNA, MRN has other roles in both the processing and assembly of large macromolecular complexes (known as foci) that facilitate efficient DSB responses. Recently, a novel mediator protein, mediator of DNA damage checkpoint protein 1 (MDC1), was shown to co-immunoprecipitate with the MRN complex and regulate MRE11 foci formation. However, whether the initial recruitment of MRN to DSBs requires MDC1 is unclear. Here, we focus on recent developments in MRN research and propose a model for how DSBs are sensed and the cellular responses to them are mediated. PMID:12949583

  6. Optimization of a uranyl nitrate passive neutron counter

    SciTech Connect

    Rauch, Eric Benton [Los Alamos National Laboratory; Bracken, David [Los Alamos National Laboratory; West, James [Los Alamos National Laboratory; Freeman, Corey [Los Alamos National Laboratory; Newell, Matthew R [Los Alamos National Laboratory; Bourret, Steven C [Los Alamos National Laboratory; Rothrock, Richard B [Los Alamos National Laboratory; Ladd - Lively, Jennifer L [ORNL; Schuh, Denise [ORNL

    2010-01-01

    Safeguarding natural uranium as it enters the fuel cycle has become a priority for the safeguards community in recent years. Uranyl nitrate is a material of interest in this endeavor because it is normally a step in the process from converting uranium ores to more concentrated forms like UO{sub 2} and U{sub 3}O{sub 8}. This paper will detail the improvements and design optimizations made for a uranyl nitrate neutron detector. The original design of the detector was based on standard neutron counter designs and featured 2 rings of He-3 tubes fully moderated and shielded from background. Several areas for enhancement were identified after months of testing in three different locations. An operating uranyl nitrate facility was included as one of the test locations. Three significant upgrades to the counter addressed in the redesign were: real time background detection, counter reliability improvements, and optimization of the detector design for the detection of neutrons emitted by the uranyl nitrate flowing through the monitored process pipe. The optimized detector design includes significant electronics upgrades, the ability to detect neutrons (background and signal) with 36 degree spatial resolution around the process pipe for signal and 45 degree spatial resolution for background, inner and outer rings of He-3 tubes for real time background corrections, and notably more reliable cabling. Monte Carlo N-Particle (MCNP) modeling was used to optimize the signal (neutrons from uranyl nitrate in the monitored process pipe) to noise (background neutrons from all sources) ratio of the inner ring of He-3 tubes. Additionally, MCNP modeling maximized noise to signal on the outer ring of He-3 tubes. Details of the detector optimization as well as all the additional detector enhancements will be discussed. The neutron counter will be field tested on the Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory (ORNL).

  7. Adsorption of uranyl on gibbsite: A time-resolved laser-induced fluorescence spectroscopy study.

    PubMed

    Chang, Hyun-Shik; Korshin, Gregory V; Wang, Zheming; Zachara, John M

    2006-02-15

    Uranyl adsorbed on gibbsite at pH 4.0-8.0 and ionic strengths (ISs) 0.001-0.4 M (NaClO4) in the absence of carbonate was studied using time-resolved laser-induced fluorescence spectroscopy (TRLIFS) under cryogenic conditions. TRLIFS data showed the presence of several distinct emission components. Their contributions were determined using the evolving factor analysis approach. Four components denoted as species A, B, C, and D were discerned. Each of them was characterized by a characteristic response to pH and IS changes and also by a unique combination of the values of the fundamental transition energy E0,0, vibronic spacing deltaE, and half-width of the vibronic lines deltaW. Species A and B were major contributors to the overall emission. They were mainly affected by the pH and predominated below and above pH 5.0, respectively. In contrast with that, the contribution of species C was noticeable only at IS = 0.001 M, while it was suppressed or absent at high IS values. It was concluded that species A and B are likely to correspond to inner-sphere surface aluminol complexes =AlO-(UO2)+ and =AlO-(UO2)OH degrees, while species C was hypothesized to correspond to electrostatically bound uranyl complexes (predominantly [UO2(OH)3]-). PMID:16572782

  8. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

    SciTech Connect

    Spencer, B.B.

    1995-08-01

    DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.

  9. Rapid Self-Assembly of Uranyl Polyhedra into Crown Clusters

    SciTech Connect

    Sigmon, Ginger E. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences; Burns, Peter C. [Univ. of Notre Dame, IN (United States). Dept. of Civil Engineering and Geological Sciences

    2011-06-22

    Clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions. These novel crown-shaped clusters are remarkable in that they form so quickly, have extraordinarily low aqueous solubility, form with at least two distinct peroxide to hydroxyl ratios, and form in very high yield. The clusters, which have outer diameters of 23 , topologically consist of eight pentagons and four hexagons. Their rapid formation and low solubility in aqueous systems may be useful properties at various stages in an advanced nuclear energy system.

  10. Noble gas-transition-metal complexes: coordination of VO2 and VO4 by Ar and Xe atoms in solid noble gas matrixes.

    PubMed

    Zhao, Yanying; Gong, Yu; Chen, Mohua; Zhou, Mingfei

    2006-02-01

    The matrix isolation infrared spectroscopic and quantum chemical calculation results indicate that vanadium oxides, VO2 and VO4, coordinate noble gas atoms in forming noble gas complexes. The results showed that VO2 coordinates two Ar or Xe atoms and that VO4 coordinates one Ar or Xe atom in solid noble gas matrixes. Hence, the VO2 and VO4 molecules trapped in solid noble gas matrixes should be regarded as the VO2(Ng)2 and VO4(Ng) (Ng = Ar or Xe) complexes. The total V-Ng binding energies were predicted to be 12.8, 18.2, 5.0, and 7.3 kcal/mol, respectively, for the VO2(Ar)2, VO2(Xe)2, VO4(Ar), and VO4(Xe) complexes at the CCSD(T)//B3LYP level of theory. PMID:16451016

  11. Ligand field influence on the electronic and magnetic properties of quasi-linear two-coordinate iron(ii) complexes.

    PubMed

    Chilton, Nicholas F; Lei, Hao; Bryan, Aimee M; Grandjean, Fernande; Long, Gary J; Power, Philip P

    2015-06-28

    The 2 to 300 K magnetic susceptibilities of Fe{N(SiMe2Ph)2}2, 1, Fe{N(SiMePh2)2}2, 2, and the diaryl complex Fe(Ar(Pr(i)4))2, 3, where Ar(Pr(i)4) is C6H3-2,6(C6H3-2,6-Pr(i)2)2 have been measured. Initial fits of these properties in the absence of an independent knowledge of their ligand field splitting have proven problematic. Ab initio calculations of the CASSCF/RASSI/SINGLE-ANISO type have indicated that the orbital energies of the complexes, as well as those of Fe(Ar(Me6))2, 4, where Ar(Me6) is C6H3-2,6(C6H2-2,4,6-Me3)2), are in the order dxy? dx(2)-y(2) < dxz? dyz < dz(2), and the iron(ii) complexes in this ligand field have the (dxy, dx(2)-y(2))(3)(dxz, dyz)(2)(dz(2))(1) ground electronic configuration with a substantial orbital contribution to their effective magnetic moments. An ab initio-derived ligand field and spin-orbit model is found to yield an excellent simulation of the observed magnetic properties of 1-3. The calculated ligand field strengths of these ligands are placed in the broader context of common coordination ligands in hypothetical two-coordinate linear iron(ii) complexes. This yields the ordering I(-) < H(-) < Br(-)? PMe3 < CH3(-) < Cl(-)? C(SiMe3)3(-) < CN(-)? SAr(Pr(i)6-) < Ar(Pr(i)4-) < Ar(Me6-)? N3(-) < NCS(-)? NCSe(-)? NCBH3(-)? MeCN ? H2O ? NH3 < NO3(-)? THF ? CO ? N(SiMe2Ph)2(-)? N(SiMePh2)2(-) < F(-)? N(H)Ar(Pr(i)6-)? N(SiMe3)Dipp(-) < OAr(Pr(i)4-). The magnetic susceptibility of the bridged dimer, [Fe{N(SiMe3)2}2]2, 5, has also been measured between 2 and 300 K and a fit of ?MT with the isotropic Heisenberg Hamiltonian, ? = -2J?1?2 yields an antiferromagnetic exchange coupling constant, J, of -131(2) cm(-1). PMID:26006177

  12. Complex-coordinate calculation of (1,3)P resonances in Ps(-) using Hylleraas functions

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Ho, Y. K.

    1990-01-01

    An accurate calculation for (1,3)P autodetaching resonances in Ps(-) has been carried out using the complex-rotation method, which has the advantage of giving resonance position and width at the same time. The wave function is of the Hylleraas type with an available number of terms up to 1140. One 1P and two 3P resonances below the n = 2 threshold and two 1P and two 3P resonances below the n = 3 threshold of the positronium atom. Resonance parameters are compared with those obtained from scattering and adiabatic calculations where available.

  13. Nickel(II) isopropylxanthate complexes containing phosphorus donor ligands in the coordination sphereII

    Microsoft Academic Search

    Zden?k Trvn?ek; Richard Pastorek; Zden?k indel?; Frantiek Kaprek; Jaromr Marek

    1997-01-01

    Nickel(II) isopropylxanthate complexes, [Ni(Prixa)2(PPh3)], [NiX(Prixa)(TCEP)], [Ni(Prixa)2(TRIPHOS]H2O and [Ni(Prixa)(TRIPHOS)][Ni(Prixa)3] {Pri = i-C3H7, xca = S2CO?, X = Cl?orBr?, PPh3 = triphenylphosphine, TCEP = tris(2-cyanoethyl)phosphine and TRIPHOS = 1,1,1-tris-(diphenylphosphino-methyl)ethane}, have been synthesized. The compounds have been characterized by elemental analysis, magnetochemical and conductivity measurements and IR and electron spectroscopies. The structure of [Ni(Prixa)2(PPh3)] has been determined by single-crystal X-ray diffraction. The nickel

  14. Studies of the Antiproliferative Activity of Ruthenium (II) Cyclopentadienyl-Derived Complexes with Nitrogen Coordinated Ligands

    PubMed Central

    Moreno, Virtudes; Lorenzo, Julia; Aviles, Francesc X.; Garcia, M. Helena; Ribeiro, Joo P.; Morais, Tnia S.; Florindo, Pedro; Robalo, M. Paula

    2010-01-01

    Four cationic ruthenium(II) complexes with the formula [Ru(?5-C5H5)(PPh3)2]+, with L = 5-phenyl-1H-tetrazole (TzH) 1, imidazole (ImH) 2, benzo[1,2-b;4,3-b?] dithio-phen-2-carbonitrile (Bzt) 3, and [5-(2-thiophen-2-yl)-vinyl]-thiophene-2-carbonitrile] (Tvt) 4 were prepared and characterized in view to evaluate their potentialities as antitumor agents. Studies by Circular Dichroism indicated changes in the secondary structure of ct-DNA. Changes in the tertiary structure of pBR322 plasmid DNA were also observed in gel electrophoresis experiment and the images obtained by atomic force microscopy (AFM) suggest strong interaction with pBR322 plasmid DNA; the observed decreasing of the viscosity with time indicates that the complexes do not intercalate between DNA base pairs. Compounds 1, 2, and 3 showed much higher cytotoxicity than the cisplatin against human leukaemia cancer cells (HL-60 cells). PMID:20689715

  15. Coordination effects on electron distributions for rhodium complexes of the redox-active bis(3,5-di-tert-butyl-2-phenolate)amide ligand.

    PubMed

    Szigethy, Gza; Shaffer, David W; Heyduk, Alan F

    2012-12-01

    New rhodium complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO(cat)]H(3)) were synthesized, and their electronic properties were investigated. These compounds were prepared by combining [ONO(q)]K and [(cod)Rh(?-Cl)](2) in the presence of an auxiliary donor ligand to yield complexes of the type [ONO]RhL(n) (n = 3, L = py (1); n = 2, L = PMe(3) (2a), L = PMe(2)Ph (2b), PMePh(2) (2c), PPh(3) (2d)). Single-crystal X-ray diffraction studies on [ONO]Rh(py)(3) (1) revealed a six-coordinate, octahedral rhodium complex. In the case of [ONO]Rh(PMe(3))(2) (2a), X-ray diffraction showed a five-coordinate, distorted square-pyramidal coordination environment around the rhodium center. While 1 is static on the NMR time scale, complexes 2a-d are fluxional, displaying both rapid isomerization of the square-pyramidal structure and exchange of coordinated and free phosphine ligands. UV-vis spectroscopy shows stark electronic differences between 1 and 2a-d. Whereas 1 displays a strong absorbance at 380 nm with a much weaker band at 585 nm in the absorption spectrum, complexes 2a-d display an intense (? > 10(4) M(-1) cm(-1)), low-energy absorption band in the region 580-640 nm; however, in the cases of 2a and 2b, the addition of excess phosphine resulted in changes to the UV-vis spectrum indicating the formation of six-coordinate adducts [ONO]Rh(PMe(3))(3) (3a) and [ONO]Rh(PMe(2)Ph)(3) (3b), respectively. The experimental and DFT computational data for the six-coordinate complexes 1, 3a, and 3b are consistent with their formulation as classical, d(6), pseudo-octahedral, coordination complexes. In the five-coordinate complexes 2a-2d, ?-bonding between the rhodium center and the [ONO] ligand leads to a high degree of covalency and metal-ligand electron distributions that are not accurately described by formal oxidation state assignments. PMID:22482509

  16. A water-soluble multisite ionophore ligand bearing pyridine and aminothiophenol functionality. Synthesis, spectroscopy and electrochemistry of its complexes, and peripheral reactivity of the ( E,E )M (M = Ni) complex with Pd 2+ and Ag +

    Microsoft Academic Search

    Mehmet Kandaz; Ali R??za zkaya; At??f Koca

    2004-01-01

    The design, synthesis and coordination of a novel multisite vic-dioxime compound, LH2, containing flexible pyridine substituents and aminophenylsulfanyl moieties on the periphery, facilitating solubility in water as pyridinium hydrochloride salt are described. LH2 was prepared by the reaction between 2-(2-pyridylethylamino)-benzenethiol and (E,E)-dichloroglydioxime. Mononuclear [(E,E)M] (M=NiII, CuII, CoII, FeII and MnII) and dinuclear uranyl (UO2II) complexes of LH2 were isolated and

  17. High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of layered uranyl arsenates.

    PubMed

    Liu, Hsin-Kuan; Ramachandran, Eswaran; Chen, Yi-Hsin; Chang, Wen-Jung; Lii, Kwang-Hwa

    2014-09-01

    Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) , b = 12.1324(4) , c = 13.7428(5) , ? = 64.175(2), ? = 89.092(2), ? = 85.548(2), V = 1047.26(7) (3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P2?/c, a = 6.8615(3) , b = 24.702(1) , c = 7.1269(3) , ? = 98.749(2), V = 1193.89(9) (3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P2?/c, a = 6.7852(3) , b = 17.3640(8) , c = 7.1151(3) , ? = 98.801(3), V = 828.42(6) (3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P2?/m, a = 6.9783(3) , b = 17.4513(8) , c = 7.0867(3) , ? = 90.808(3), V = 862.94(7) (3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) , b = 9.3324(4) , c = 11.9336(4) , ? = 75.611(2), ? = 73.136(2), ? = 86.329(2), V = 801.37(5) (3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by splitting the ?-U3O8-type sheet into complex chains and connecting the chains by arsenates. PMID:25133864

  18. Influence of the ?-coordinated arene on the anticancer activity of ruthenium(II) carbohydrate organometallic complexes

    PubMed Central

    Hanif, Muhammad; Meier, Samuel M.; Nazarov, Alexey A.; Risse, Julie; Legin, Anton; Casini, Angela; Jakupec, Michael A.; Keppler, Bernhard K.; Hartinger, Christian G.

    2013-01-01

    The synthesis and in vitro cytotoxicity of a series of RuII(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA, indicating that other biological targets are responsible for its cytotoxic effect. PMID:24790955

  19. Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

    SciTech Connect

    K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

    2005-05-11

    The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

  20. Two mechanisms coordinate replication termination by the Escherichia coli Tus-Ter complex.

    PubMed

    Pandey, Manjula; Elshenawy, Mohamed M; Jergic, Slobodan; Takahashi, Masateru; Dixon, Nicholas E; Hamdan, Samir M; Patel, Smita S

    2015-07-13

    The Escherichia coli replication terminator protein (Tus) binds to Ter sequences to block replication forks approaching from one direction. Here, we used single molecule and transient state kinetics to study responses of the heterologous phage T7 replisome to the Tus-Ter complex. The T7 replisome was arrested at the non-permissive end of Tus-Ter in a manner that is explained by a composite mousetrap and dynamic clamp model. An unpaired C(6) that forms a lock by binding into the cytosine binding pocket of Tus was most effective in arresting the replisome and mutation of C(6) removed the barrier. Isolated helicase was also blocked at the non-permissive end, but unexpectedly the isolated polymerase was not, unless C(6) was unpaired. Instead, the polymerase was blocked at the permissive end. This indicates that the Tus-Ter mechanism is sensitive to the translocation polarity of the DNA motor. The polymerase tracking along the template strand traps the C(6) to prevent lock formation; the helicase tracking along the other strand traps the complementary G(6) to aid lock formation. Our results are consistent with the model where strand separation by the helicase unpairs the GC(6) base pair and triggers lock formation immediately before the polymerase can sequester the C(6) base. PMID:26007657

  1. Coordinated regulation of retinoic acid signaling pathway by KDM5B and polycomb repressive complex 2.

    PubMed

    Zhang, Yu; Liang, Jing; Li, Qian

    2014-09-01

    Polycomb repressive complex 2 (PRC2) is a critical epigenetic regulator in many biological processes, including maintenance of cell identity, stem cell self-renewal, differentiation, and deregulation of PRC2 is often observed in human cancers and diseases. Here we report that KDM5B (PLU-1/JARID1B), a histone lysine demethylase of Jumonji family, associates with PRC2 and colocalizes with PRC2 in nuclear bodies, and their physical association is dependent on direct interaction between KDM5B and the SUZ12 component of PRC2. Interestingly, co-occupancy of KDM5B and PRC2 was evidenced at the conserved cis-regulatory DNA element on retinoic acid (RA) responsive genes. Transcription readout and in vitro pull-down experiments suggest that KDM5B is an essential co-activator, but not a co-repressor, for the RA signaling, and the interface between KDM5B's JMJC domain and retinoic acid receptor ? (RAR?) is crucial for RA-mediated gene expression. Detailed chromatin immunoprecipitation assays addressed the seemingly paradox by revealing a biphasic effect of KDM5B on RA-induced gene activation through decoupled H3K4me3 demethylation and PRC2-antagonizing activities. These results demonstrate that KDM5B and PRC2 regulate RA signaling cascade in a cooperative and orchestrated fashion. PMID:24619877

  2. Structure and dynamics of aqueous solution of uranyl ions

    SciTech Connect

    Chopra, Manish [Radiation Safety Systems Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Choudhury, Niharendu, E-mail: nihcho@barc.gov.in [Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2014-04-24

    The present work describes a molecular dynamics simulation study of structure and dynamics of aqueous solution of uranyl ions in water. Structural properties of the system in terms of radial distribution functions and dynamical characteristics as obtained through velocity autocorrelation function and mean square displacements have been analyzed. The results for radial distribution functions show the oxygen of water to form the first solvation shell at 2.4 around the uranium atom, whereas the hydrogen atoms of water are distributed around the uranium atom with the major peak at around 3.0 . Analyses of transport behaviors of ions and water through MSD indicates that the diffusion of the uranyl ion is much less as compared to that of the water molecules. It is also observed that the dynamical behavior of water molecules gets modified due to the presence of uranyl ion. The effect of increase in concentration of uranyl ions on the structure and dynamics of water molecules is also studied.

  3. CATALYTIC DECOMPOSTION OF HYDROGEN PEROXIDE AND URANYL PEROXIDE

    Microsoft Academic Search

    Louis Silverman; Robert Sallach; Rachel Seitz; Wanda Bradshaw

    1958-01-01

    Decomposition rates are given of peroxide in dilute uranyl sulfate-; hydrogen peroxide solutions. A wide variety of catalysts and combination of ; cataiysts was tested. but the investigation was generally limited to the pH range ; oi 1 to 3. The effects of temperature, catalyst concentration, acidity. and ; uranium concentraiion on the decomposition are discussed. (J.H.M.);

  4. Acute toxicity of uranium hexafluoride, uranyl fluoride and hydrogen fluoride

    Microsoft Academic Search

    Just

    1988-01-01

    Uranium hexafluoride (UF) released into the atmosphere will react rapidly with moisture in the air to form the hydrolysis products uranyl fluoride (UOF) and hydrogen fluoride (HF). Uranium compounds such as UF and UOF exhibit both chemical toxicity and radiological effects, while HF exhibits only chemical toxicity. This paper describes the development of a methodology for assessing the human health

  5. An infrared and Raman spectroscopic study of the uranyl micas

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.

    2004-06-01

    Vibrational spectroscopy using a combination of infrared and Raman spectroscopy has been used to study the uranyl micas also known as the autunite minerals, of general formula M(UO 2) 2(XO 4) 28-12H 2O where M may be Ba, Ca, Cu, Fe 2+, Mg, Mn 2+ or 1/2(HAl) and X is As or P. Included in these minerals are autunite, metautunite, torbernite, meta-torbernite, meta-zeunerite, saleite and sabugalite. Compared with the results of infrared spectroscopy, Raman microscopy shows excellent band separation enabling the separation and identification of bands attributed to (UO 2) 2+ units, PO 4 and AsO 4 units. Common to all spectra were bands at around 900 and 818 cm -1, attributed to the antisymmetric and symmetric stretching vibrations of the (UO 2) 2+ units. Water in autunites is in a highly structured arrangement in the interlayer of the uranyl micas. Water molecules are differentiated according to the strength of the hydrogen bonds formed between the water and the adjacent uranyl-phosphate or uranyl-arsenate surfaces and the hydration sphere of the interlayer cation.

  6. Analysis of High Enriched Uranyl Nitrate Solution Containing Cadmium

    SciTech Connect

    S. S. Kim

    2006-09-01

    A benchmark evaluation has been performed for a set of twenty-one critical experiments involving high enriched uranyl nitrate solution with and without cadmium nitrate as a soluble neutron absorber. The critical experiments analyzed include two types of cylindrical vessels with 24.18 and 29.16 cm in diameters. The vessels were reflected with water and in some cases with water containing dissolved cadmium nitrate. The uranium concentration ranged from 482 to 529 g/l, and cadmium concentration in the uranyl nitrate solution ranged from 0.0 to 11.31 g/l. The cadmium concentration in the reflector solution ranged from 0.0 to 15.16 g/l. Using MCNP and KENO-V.a, complete three-dimensional models were created for the two vessels filled with the uranyl nitrate solution and reflector solution. A series of criticality calculations were performed with KENO-V.a, MCNP4b, and MCNP5. In general, good agreement between KENO-V.a and MCNP4b was observed. However, MCNP5 results show consistently lower values compared with MCNP4b results with the maximum difference of 1.2 %. This ICSBEP supported evaluation provides valuable data for the effect of soluble neutron absorber (cadmium nitrate) on the criticality safety of high-enriched uranyl nitrate solution. These data can also be used in determining critical controls and for validation of the calculation methods.

  7. Engineering and Coordination of Regulatory Networks and Intracellular Complexes to Maximize Hydrogen Production by Phototrophic Microorganisms

    SciTech Connect

    James C. Liao

    2012-05-22

    This project is a collaboration with F. R. Tabita of Ohio State. Our major goal is to understand the factors and regulatory mechanisms that influence hydrogen production. The organisms to be utilized in this study, phototrophic microorganisms, in particular nonsulfur purple (NSP) bacteria, catalyze many significant processes including the assimilation of carbon dioxide into organic carbon, nitrogen fixation, sulfur oxidation, aromatic acid degradation, and hydrogen oxidation/evolution. Our part of the project was to develop a modeling technique to investigate the metabolic network in connection to hydrogen production and regulation. Organisms must balance the pathways that generate and consume reducing power in order to maintain redox homeostasis to achieve growth. Maintaining this homeostasis in the nonsulfur purple photosynthetic bacteria is a complex feat with many avenues that can lead to balance, as these organisms possess versatile metabolic capabilities including anoxygenic photosynthesis, aerobic or anaerobic respiration, and fermentation. Growth is achieved by using H{sub 2} as an electron donor and CO{sub 2} as a carbon source during photoautotrophic and chemoautotrophic growth, where CO{sub 2} is fixed via the Calvin-Benson-Bassham (CBB) cycle. Photoheterotrophic growth can also occur when alternative organic carbon compounds are utilized as both the carbon source and electron donor. Regardless of the growth mode, excess reducing equivalents generated as a result of oxidative processes, must be transferred to terminal electron acceptors, thus insuring that redox homeostasis is maintained in the cell. Possible terminal acceptors include O{sub 2}, CO{sub 2}, organic carbon, or various oxyanions. Cells possess regulatory mechanisms to balance the activity of the pathways which supply energy, such as photosynthesis, and those that consume energy, such as CO{sub 2} assimilation or N{sub 2} fixation. The major route for CO{sub 2} assimilation is the CBB reductive pentose phosphate pathway, whose key enzyme is ribulose 1,5-biphosphate carboxylase/oxygenase (RubisCO). In addition to providing virtually all cellular carbon during autotrophic metabolism, RubisCO-mediated CO{sub 2} assimilation is also very important for nonsulfur purple photosynthetic bacteria under photoheterotrophic growth conditions since CO{sub 2} becomes the major electron sink under these conditions. In this work, Ensemble Modeling (EM) was developed to examine the behavior of CBB-compromised RubisCO knockout mutant strains of the nonsulfur purple photosynthetic bacterium Rhodobacter sphaeroides. Mathematical models of metabolism can be a great aid in studying the effects of large perturbations to the system, such as the inactivation of RubisCO. Due to the complex and highly-interconnected nature of these networks, it is not a trivial process to understand what the effect of perturbations to the metabolic network will be, or vice versa, what enzymatic perturbations are necessary to yield a desired effect. Flux distribution is controlled by multiple enzymes in the network, often indirectly linked to the pathways of interest. Further, depending on the state of the cell and the environmental conditions, the effect of a perturbation may center around how it effects the carbon flow in the network, the balancing of cofactors, or both. Thus, it is desirable to develop mathematical models to describe, understand, and predict network behavior. Through the development of such models, one may gain the ability to generate a set of testable hypotheses for system behavior.

  8. Probing the Influence of Local Coordination Environment on the Properties of Fe-Type Nitrile Hydratase Model Complexes

    PubMed Central

    Jackson, Henry L.; Shoner, Steven C.; Rittenberg, Durrell; Cowen, Jerry A.; Lovell, Scott; Barnhart, David; Kovacs, Julie A.

    2015-01-01

    A series of four structurally related cis-dithiolate-ligated Fe(III) complexes, [FeIII(DITpy)2]Cl (1), [FeIII(DITIm)2]Cl (2), [FeIII(ADIT)2]Cl (3), and [FeIII(AMIT)2]Cl (4), are described. The structural characterization of 3 as well as the spectroscopic properties of 3 and 4 has been previously reported. Crystal data for 1, 2, and 4 are as follows: 13H2O crystallizes in the orthorhombic space group Pca21 with a = 19.800(4) , b = 18.450(4) , c = 14.800(3) , and Z = 8. 2EtOHH2O crystallizes in the monoclinic space group Cc with a = 24.792(4) , b = 14.364(3) , c = 17.527(3) , ? = 124.91(2), and Z = 8. 4 crystallizes in the triclinic space group P1? with a = 8.0152(6) , b = 10.0221(8) , c = 11.8384(10) , ? = 73.460(3), ? = 71.451(5) , ? = 72.856(4), and Z = 2. Complexes 14 share a common S2N4 coordination environment that consists of two cis-thiolates, two trans-imines, and two cis-terminal nitrogen donors: Nterm = pyridine (1), imidazole (2), and primary amine (3 and 4). The crystallographically determined mean FeS bond distances in 14 range from 2.196 to 2.232 and are characteristic of low-spin Fe(III)thiolate complexes. The low-spin S = ground state was confirmed by both EPR and magnetic susceptibility measurements. The electronic spectra of these complexes are characterized by broad absorption bands centered near ~700 nm that are consistent with ligand-to-metal charge-transfer (CT) bands. The complexes were further characterized by cyclic voltammetry measurements, and all possess highly negative Fe(III)/Fe(II) redox couples (~ ?1 V vs SCE, saturated calomel electrode) indicating that alkyl thiolate donors are effective at stabilizing Fe(III) centers. Both the redox couple and the 700 nm band in the visible spectra show solvent-dependent shifts that are dependent upon the H-bonding ability of the solvent. The implications of these results with respect to the active site of the iron-containing nitrile hydratases are also discussed. PMID:11261975

  9. Tunable N-substitution in zwitterionic benzoquinonemonoimine derivatives: metal coordination, tandemlike synthesis of zwitterionic metal complexes, and supramolecular structures.

    PubMed

    Yang, Qing-Zheng; Siri, Olivier; Braunstein, Pierre

    2005-12-01

    Full details on a very efficient transamination reaction for the synthesis of zwitterionic N,N-dialkyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium derivatives [C6H2(=NHR)2(=O)2] 5-16 are reported. The molecular structures of zwitterions 5 (R=CH3) in 5.H2O, 13 (R=CH2CH2OMe), 15 (R=CH2CH2NMe2), and of the parent, unsubstituted system [C6H2(=NH2)2(=O)2] 4 in 4.H2O have been established by single-crystal X-ray diffraction. This one-pot preparation can be carried out in water, MeOH, or EtOH and allows access to new zwitterions with N-substituents bearing functionalities such as -OMe (13), -OH (9-12), NR1R2 with R1 = or not equal R2 (14-16) or an alkene (8), leading to a rich coordination chemistry and allowing fine-tuning of the supramolecular arrangements in the solid state. As previously described for 15, which reacted with Zn(acac)2 to afford the octahedral Zn(II) complex [Zn[C6H2(NCH2CH2NMe2)O(O)(NHCH2CH2NMe2)]2] (20), ligands 13 and 16 with coordinating "arms" afforded with Zn(acac)2 the 2:1 adducts [Zn[C6H2(NCH2CH2X)O(=O)(NHCH2CH2NX)]2] 19 (X=OMe) and 21 (X=NHEt), with N2O4 and N4O2 donor sets around the octahedral Zn(II) center, respectively. Furthermore, zwitterions 15 and 16 reacted with ZnCl2 to give the stable, crystallographically characterized Zn(II) zwitterionic complexes [ZnCl2[C6H2(NCH2CH2NR1R2)O(=O)(NHCH2CH2NHR1R2)

  10. Cluster-Models for Uranyl(VI) Adsorption on alpha-Alumina

    SciTech Connect

    Glezakou, Vassiliki Alexandra; De Jong, Wibe A.

    2011-02-24

    Aqueous complexation, adsorption and redox chemistry of actinide species at mineral surfaces have significant impact on their transport and reactive behaviour in chemically and physically heterogeneous environments. The adsorption configurations and energies of micro-solvated uranyl dication, UO2 2+, on fully hydroxylated and H-deficient a-alumina (0001)-like finite cluster models were studied. The significant size of the models provides faithful representations of features that have emerged from periodic calculations, but most importantly, they afford us a systematic study of the preferred adsorption configurations, effect of secondary solvation shells and explicit treatment of the total charge. The energetics computed from the difference between the optimized structures and the appropriate reference states, point at a preference for inner sphere type complex.

  11. Synthesis, reactivity, and coordination chemistry relevant to the copolymerization of CO2 and epoxides by first row transition metal schiff base complexes

    E-print Network

    Frantz, Eric Benjamin

    2009-05-15

    the copolymerization of CO2 and epoxide to form aliphatic polycarbonates. A new chromium(III) Schiff base complex has been synthesized and evaluated for its ability to catalyze the formation of polymer. The ligand employed bears an N2O2 coordination sphere identical...

  12. Synthesis, crystal structures, and urease inhibition of an acetohydroxamate-coordinated oxovanadium(V) complex derived from N'-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide.

    PubMed

    Qu, Dan; Niu, Fang; Zhao, Xinlu; Yan, Ke-Xiang; Ye, Yu-Ting; Wang, Jia; Zhang, Mei; You, Zhonglu

    2015-05-01

    A new benzohydrazone compound N'-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H?L) was prepared. Reaction of H?L and acetohydroxamic acid (HAHA) with VO(acac)? in methanol gave the complex [VOL(AHA)]. Both H?L and the oxovanadium complex were characterized by elemental analysis, IR, UV-vis and (1)H NMR spectra, and single crystal X-ray diffraction. H?L was also characterized by high-resolution mass spectrum. Thermal analysis of the oxovanadium complex was carried out. The benzohydrazone ligand, in its dianionic form, coordinates to V atom through the phenolate oxygen, imino nitrogen and enolate oxygen. The acetohydroxamic acid coordinates to V atom through the carbonyl oxygen and deprotonated hydroxyl oxygen. The V atom is in octahedral coordination. H?L, HAHA and the oxovanadium complex were tested for their urease inhibitory activities. The percent inhibition at concentration of 100 ?molL(-1) on Helicobacter pylori urease is 78% for the oxovanadium complex. The IC?? value for the complex is 36.5 ?molL(-1). Molecular docking study was performed to study the inhibition. PMID:25840795

  13. Fluorescence properties of a uranyl(V)-carbonate species [U(V)O(2)(CO(3))(3)](5-) at low temperature.

    PubMed

    Grossmann, Kay; Arnold, Thuro; Ikeda-Ohno, Atsushi; Steudtner, Robin; Geipel, Gerhard; Bernhard, Gert

    2009-03-01

    Fluorescence properties of a uranyl(V)-carbonate species in solution are reported for the first time. The fluorescence characteristics of the stable aqueous uranyl(V)-carbonate complex [U(V)O(2)(CO(3))(3)](5-) was determined in a frozen solution (T=153K) of 0.5mM uranium and 1.5M Na(2)CO(3) at pH 11.8 by time resolved laser-induced fluorescence spectroscopy (TRLFS). Two different wavelengths of 255nm and 408nm, respectively were used to independently of each other excite the uranyl(V)-carbonate species. The resulting U(V) fluorescence emission bands were detected between 380nm and 440nm, with a maxima at 404.7nm (excitation with 255nm) and 413.3nm (excitation with 408nm), respectively. It was found that by using an excitation wavelength of 255nm the corresponding extinction coefficient was much higher and the fluorescence spectrum better structured than the ones excited at 408nm. The fluorescence lifetime of the uranyl(V)-carbonate species was determined at 153K as 120micros. TRLFS investigations at room temperature, however, showed no fluorescence signal at all. PMID:19091628

  14. Multispecies diffusion models: A study of uranyl species diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-01

    Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A, where intragranular diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that had been previously described using a semiempirical, multirate model. Compared with the multirate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

  15. Characterization and Dioxygen Reactivity of a New Series of Coordinatively Unsaturated Thiolate-Ligated Manganese(II) Complexes

    PubMed Central

    Coggins, Michael K.; Toledo, Santiago; Shaffer, Erika; Kaminsky, Werner; Shearer, Jason; Kovacs, Julie A.

    2012-01-01

    The synthesis, structural, and spectroscopic characterization of four new coordinatively unsaturated mononuclear thiolate-ligated manganese(II) complexes ([MnII(SMe2N4(6-Me-DPEN))](BF4) (1), [MnII(SMe2N4(6-Me-DPPN))](BPh4)MeCN (3), [MnII(SMe2N4(2-QuinoPN))](PF6)MeCNEt2O (4), and [MnII(SMe2N4(6-H-DPEN)(MeOH)](BPh4) (5)) is described, along with their magnetic, redox, and reactivity properties. These complexes are structurally-related to recently reported [MnII(SMe2N4(2-QuinoEN))](PF6) (2) Dioxygen addition to complexes 1-5 is shown to result in the formation of five new rare examples of Mn(III) dimers containing a single, unsupported oxo bridge: [MnIII(SMe2N4(6-Me-DPEN)]2-(?-O)(BF4)22MeOH (6), [MnIII(SMe2N4(QuinoEN)]2-(?-O)(PF6)2Et2O (7), [MnIII(SMe2N4(6-Me-DPPN)]2-(?-O)(BPh4)2 (8), [MnIII(SMe2N4(QuinoPN)]2-(?-O)(BPh4)2 (9), and [MnIII(SMe2N4(6-H-DPEN)]2-(?-O)(PF6)22MeCN (10). Labeling studies show that the oxo atom is derived from 18O2. Ligand modifications, involving either the insertion of a methylene into the backbone, or the placement of an ortho substituent on the N-heterocyclic amine, are shown to noticeably modulate the magnetic and reactivity properties. Fits to solid-state magnetic susceptibility data show that the Mn(III) ions of ? -oxo dimers 6-10 are moderately antiferromagnetically coupled, with coupling constants (2J) that fall within the expected range. Metastable intermediates, which ultimately convert to ?-oxo bridged 6 and 7, are observed in low-temperature reactions between 1 and 2 and dioxygen. Complexes 3-5, on the other hand, do not form observable intermediates, thus illustrating the effect that relatively minor ligand modifications have upon the stability of metastable dioxygen-derived species. PMID:22642272

  16. A complex regulatory network coordinating cell cycles during C. elegans development is revealed by a genome-wide RNAi screen.

    PubMed

    Roy, Sarah H; Tobin, David V; Memar, Nadin; Beltz, Eleanor; Holmen, Jenna; Clayton, Joseph E; Chiu, Daniel J; Young, Laura D; Green, Travis H; Lubin, Isabella; Liu, Yuying; Conradt, Barbara; Saito, R Mako

    2014-05-01

    The development and homeostasis of multicellular animals requires precise coordination of cell division and differentiation. We performed a genome-wide RNA interference screen in Caenorhabditis elegans to reveal the components of a regulatory network that promotes developmentally programmed cell-cycle quiescence. The 107 identified genes are predicted to constitute regulatory networks that are conserved among higher animals because almost half of the genes are represented by clear human orthologs. Using a series of mutant backgrounds to assess their genetic activities, the RNA interference clones displaying similar properties were clustered to establish potential regulatory relationships within the network. This approach uncovered four distinct genetic pathways controlling cell-cycle entry during intestinal organogenesis. The enhanced phenotypes observed for animals carrying compound mutations attest to the collaboration between distinct mechanisms to ensure strict developmental regulation of cell cycles. Moreover, we characterized ubc-25, a gene encoding an E2 ubiquitin-conjugating enzyme whose human ortholog, UBE2Q2, is deregulated in several cancers. Our genetic analyses suggested that ubc-25 acts in a linear pathway with cul-1/Cul1, in parallel to pathways employing cki-1/p27 and lin-35/pRb to promote cell-cycle quiescence. Further investigation of the potential regulatory mechanism demonstrated that ubc-25 activity negatively regulates CYE-1/cyclin E protein abundance in vivo. Together, our results show that the ubc-25-mediated pathway acts within a complex network that integrates the actions of multiple molecular mechanisms to control cell cycles during development. PMID:24584095

  17. Radical anionic versus neutral 2,2'-bipyridyl coordination in uranium complexes supported by amide and ketimide ligands.

    PubMed

    Diaconescu, Paula L; Cummins, Christopher C

    2015-02-14

    The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipyridyl, Ar = 3,5-C(6)H(3)Me(2)), (bipy)U(N[(1)Ad]Ar)(3) (2-bipy), (bipy)(2)U(NC[t-Bu]Mes)(3) (3-(bipy)(2), Mes = 2,4,6-C(6)H(2)Me(3)), and IU(bipy)(NC[t-Bu]Mes)(3) (3-I-bipy) are reported. X-ray crystallography studies indicate that bipy coordinates as a radical anion in 1-(bipy)(2) and 2-bipy, and as a neutral ligand in 3-I-bipy. In 3-(bipy)(2), one of the bipy ligands is best viewed as a radical anion, the other as a neutral ligand. The electronic structure assignments are supported by NMR spectroscopy studies of exchange experiments with 4,4'-dimethyl-2,2'-bipyridyl and also by optical spectroscopy. In all complexes, uranium was assigned a +4 formal oxidation state. PMID:25510329

  18. Effect of citrate on the local Fe coordination in ferrihydrite, arsenate binding, and ternary arsenate complex formation

    NASA Astrophysics Data System (ADS)

    Mikutta, Christian; Frommer, Jakob; Voegelin, Andreas; Kaegi, Ralf; Kretzschmar, Ruben

    2010-10-01

    In oxic environments contaminated with arsenate (As(V)), small polyhydroxycarboxylates such as citrate may impact the structure of precipitating ferrihydrite (Fh) and thus the surface speciation of As(V). In this study, '2-line' Fh was precipitated from ferric nitrate solutions that were neutralized to pH 6.5 in the presence of increasing citrate concentrations and in the absence or presence of As(V). The initial citrate/Fe and As/Fe ratios were 0-50 mol% and 5 mol%, respectively. The reaction products, enriched with up to 0.32 mol citrate per mole Fe, were characterized by X-ray diffraction, transmission electron microscopy, and Fe and As K-edge X-ray absorption spectroscopy. Citrate decreased the particle size of Fh by impairing the polymerization of Fe(O,OH) 6 octahedra via edge and corner linkages. In the presence of citrate and As(V), coordination numbers of Fe decreased by up to 28% relative to pure Fh. Citrate significantly reduced the static disorder of Fe-O bonds, implying a decreased octahedral distortion in Fh. Mean bond distances in Fh were not affected by citrate and remained constant within error at 1.98 for Fe-O, 3.03 for Fe-Fe1, and 3.45 for Fe-Fe2. Likewise, citrate had no effect on the As-Fe (3.31 ) bond distance in As(V) coprecipitated with Fh. The As K-edge EXAFS data comply with the formation of (i) only monodentate binuclear ( 2C) As(V) surface complexes and (ii) combinations of 2C, monodentate mononuclear ( 1V), and outersphere As(V) surface complexes. Our results suggest that increasing citrate concentrations led to a decreasing 1V/ 2C ratio and/or that citrate increasingly impaired the formation of outersphere As(V) complexes. Moreover, citrate stabilized colloidal suspensions of Fh (pH 4.3-6.6, I 0.45 M) and reduced Fh formation at the expense of soluble Fe(III)-citrate complexes. At initial citrate/Fe ratios ?25 mol%, between 8% and 41% of total Fe was bound in Fe(III)-citrate complexes after Fh formation. Polynuclear Fe(III)-citrate species were found to bind As(V) via surface complexes indistinguishable by EXAFS from those of As(V) adsorbed to or coprecipitated with Fh. Our study implies that low molecular weight polyhydroxycarboxylates may enhance the mobility of As(V) in aqueous systems of high ionic strength (e.g., neutralizing acid mine drainage) by colloidal stabilization of suspended Fh particles and the formation of ternary As(V) complexes.

  19. Toxicity of Certain Penta-Coordinated Organotin(IV) and Tetra-Coordinated Tin(II) Complexes of Heterocyclic ?-Diketones Against the Larvae of Aedes Aegypti (Liston)

    PubMed Central

    Jain, Asha; Saxena, Sanjiv; Saxena, Prabhu N.; Rao, J. Venkateshwara

    1999-01-01

    Some organotin(IV) and tin(II) complexes of composition R3Sn[R'COC:CON(C6H5)N:CCH3] (where R=C4H9, R'=CH3, C3H5, p-ClC6H4; R=C6H5, R'=C6H5 and p-ClC6H4) and Sn[p-ClC6H4COC:CON(C6H5)N:CCH3]2 were screened for their toxicity against Aedes aegypti larvae. Organotin(IV) complexes were more active than tin(II) complexes. PMID:18472910

  20. Luminescent nine-coordinate lanthanide complexes derived from fluorinated ?-diketone and 2,4,6-tris(2-pyridyl)-1,3,5-triazine

    Microsoft Academic Search

    Rashid Ilmi; K. Iftikhar

    2012-01-01

    The synthesis, photoluminescence, 4f4f absorptions, and NMR studies of nine-coordinate lanthanide(III) complexes, [Ln(tfaa)3(tptz)] (Ln?=?La, Nd, Sm, and Eu; tfaa is the anion of 1,1,1-trifluoro-2,4-pantanedione; and tptz?=?2,4,6-tris(2-pyridyl)-1,3,5-triazine), are reported. These complexes are synthesized in a single pot by in situ method and thoroughly characterized. The ?-diketone and tptz chemical shifts, in the cases of paramagnetic complexes, are in the opposite directions.

  1. Preparation and properties of [Ni II(BEES)(Cl)](BPh 4): a Ni II complex in a mixed nitrogen\\/thioether coordination environment

    Microsoft Academic Search

    Jason Shearer; Johnny Lai; Danielle L Jacobs; Julie A Kovacs

    2002-01-01

    The synthesis and properties of the NiII complex [NiII(BEES)(Cl)](BPh4) are described. The ligand bis-2-?-benzylthioethylaminoethylsulfideHCl (BEESHCl) was prepared in good yield in three steps from bis-ethylaminosulfide and acetyl chloride. Complexation of NiII in the presence of chloride affords [NiII(BEES)(Cl)](BPh4), which contains high-spin NiII in a pseudo-octahedral coordination environment, ligated by amine nitrogens, thioether sulfurs, and a chloride. The complex is irreversibly

  2. Synthesis and visible light luminescence of mononuclear nine-coordinate lanthanide complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine

    Microsoft Academic Search

    Zubair Ahmed; K. Iftikhar

    2010-01-01

    Synthesis of four nine-coordinate lanthanide (III) complexes of the type, [Ln(hfaa)3(tptz)], where Ln=La, Nd, Sm and Tb; hfaa=the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine, by a new modified one pot in situ method is reported. The lanthanide ions are coordinated to three N-atoms of three 2-pyridyl units of tptz besides six O-atoms of three hfaa units. The formation of these volatile

  3. Synthesis, Characterization, and Reactivity of a Uranium(VI) Carbene Imido Oxo Complex**

    PubMed Central

    Lu, Erli; Cooper, Oliver J; McMaster, Jonathan; Tuna, Floriana; McInnes, Eric J L; Lewis, William; Blake, Alexander J; Liddle, Stephen T

    2014-01-01

    We report the uranium(VI) carbene imido oxo complex [U(BIPMTMS)(NMes)(O)(DMAP)2] (5, BIPMTMS=C(PPh2NSiMe3)2; Mes=2,4,6-Me3C6H2; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPMTMS)(O)2(DMAP)2] (6). PMID:24842784

  4. Mutual solubility in the system uranyl trifluoroacetate--water--diethyl ether

    Microsoft Academic Search

    V. M. Vdovenko; A. V. Baluev; I. G. Suglobova

    1975-01-01

    A study was made of mutual solubility in the system uranyl trifluoroacetate--water--diethyl ether at 25°C. It was found that uranyl trifluoroacetate, like the trichloroacetate which was investigated previously, is extracted by diethyl ether much better than uranyl nitrate over a wide range of concentrations. The solubility of UO(CFCOO) in ether depends strongly on the water content of the system. While

  5. Preparation and Reactions of the 1,1-Dithiolato Complexes of Ni(II). An Undergraduate Coordination Chemistry Experiment.

    ERIC Educational Resources Information Center

    Ballester, L.; Perpinan, M. F.

    1988-01-01

    Described is an undergraduate coordination chemistry experiment that enables students to relate concepts developed in class about the stereochemistry and coordination numbers to the interpretation of the electronic and infrared spectra and their magnetic behavior. Indicates that thermal decomposition and x-ray diffraction studies can also be

  6. Photoactivated Uranyl Ion Produces Single Strand Breaks in Plasmid DNA

    PubMed Central

    George, Shannon A.; Whittaker, Aaron M.; Stearns, Diane M.

    2011-01-01

    Uranium is an important emerging toxicant whose use has outpaced the rate at which we are learning about its health effects. One unexplored pathway for uranium toxicity involves the photoactivation of uranyl ion by UV light to produce U5+ and oxygen radicals. The purpose of this study was to provide proof of principle data by testing the hypothesis that coexposures of DNA to uranyl acetate and UVB irradiation should produce more DNA strand breaks than individual exposures. Results supported the hypothesis and suggest that investigations of uranium toxicity be expanded to include skin as a potential target organ for carcinogenesis, especially in populations with high uranium and high UV radiation exposures. PMID:22013951

  7. Tritium gettering from air with hydrogen uranyl phosphate. Revision 1

    SciTech Connect

    Souers, P.C.; Uribe, F.S.; Stevens, C.G.; Tsugawa, R.T.

    1985-01-01

    Hydrogen uranyl phosphate (HUP), a solid proton electrolyte, getters tritium gas and water vapor from air by DC electrical action. We have reduced the formation of residual tritiated water to less than 2%, and demonstrated that HUP can clean a 5.5 m/sup 3/ working glove box. Data are presented to illustrate the parameters of the gettering and a model is derived. Two other tritium gettering electrolytes have been discovered. 9 refs., 5 figs., 3 tabs.

  8. Tritium gettering from air with hydrogen uranyl phosphate

    SciTech Connect

    Souers, P.C.; Uribe, F.S.; Stevens, C.G.; Tsugawa, R.T.

    1985-01-01

    Hydrogen uranyl phosphate (HUP), a solid proton electrolyte, getters tritium gas and water vapor from air by DC electrical action. We have reduced the formation of residual tritiated water to less than 2%, and demonstrated that HUP can clean a 5.5 m/sup 3/ working glove box. Data are presented to illustrate the parameters of the gettering and a model is derived. Two other tritium gettering electrolytes have been discovered. 9 refs., 5 figs., 3 tabs.

  9. Stereochemical control over Mn(II)-Thio versus Mn(II)-Oxy coordination in adenosine 5 prime -O-(1-thiodiphosphate) complexes at the active site of creatine kinase

    SciTech Connect

    Smithers, G.W.; Sammons, R.D.; Goodhart, P.J.; LoBrutto, R.; Reed, G.H. (Univ. of Wisconsin, Madison (USA))

    1989-02-21

    The stereochemical configurations of the Mn(II) complexes with the resolved epimers of adenosine 5{prime}-O-(1-thiodiphosphate) (ADP{alpha}S), bound at the active site of creatine kinase, have been determined in order to assess the relative strengths of enzymic stereoselectivity versus Lewis acid/base preferences in metal-ligand binding. Electron paramagnetic resonance (EPR) data have been obtained for Mn(II) in anion-stabilized, dead-end (transition-state analogue) complexes, in ternary enzyme-Mn{sup II}ADP{alpha}S complexes, and in the central complexes of the equilibrium mixture. The modes of coordination of Mn(II) at P{sub alpha} in the nitrate-stabilized, dead-end complexes with each epimer of ADP{alpha}S were ascertained by EPR measurements with (R{sub p})-({alpha}-{sup 17}O)ADP{alpha}S and (S{sub p})-({alpha}-{sup 17}O)ADP{alpha}S. A reduction in the magnitude of the {sup 55}Mn hyperfine coupling constant in the spectrum for the complex containing (S{sub p})-ADP{alpha}S is indicative of Mn(II)-thio coordination at P{sub alpha}. The results indicate that a strict discrimination for a unique configuration of the metal-nucleotide substrate is expressed upon binding of all of the substrates to form the active complex (or an analogue thereof). This enzymic stereoselectivity provides sufficient binding energy to overcome an intrinsic preference for the hard Lewis acid Mn(II) to coordinate to the hard Lewis base oxygen.

  10. Electroluminescence cells based on the lamellar solid hydrogen uranyl phosphate

    SciTech Connect

    Dieckmann, G.R.,; Ellis, A.B.; Hellstrom, E.E. (Dept. of Chemistry, Univ. of Wisconsin-Madison, Madison, WI (US))

    1990-07-01

    Electroluminescence (EL) cells have been constructed with the layered, ionically conducting solid, hydrogen uranyl phosphate, HUO{sub 2}PO{sub 4} {center dot} 4H{sub 2}O (HUP), as the emissive medium. With ac excitation, both uranyl emission and molecular nitrogen plasma emission are observed, with the latter appearing to excite the former; the uranyl EL spectrum matches the photoluminescence spectrum of the solid. Similar results were obtained with fully substituted sodium (NaUP), magnesium (Mg{sub 0.5}UP), and pyridinium (pyHUP) derivatives of HUP. For all of these solids, the dependence of the EL intensity on sample thickness, ac frequency, and applied voltage has been determined. Typical operating conditions are 1.5--3.0 kV at 0.2--4 kHz. Impedance measurements permitted acquisition of dielectric constants and ionic conductivities for these solids, both of which decrease in the order HUP {gt} NaUP {gt} Mg{sub 0.5}UP {gt} pyHUP. A model describing the dependence of EL intensity on cell parameters is presented.

  11. Incorporation of Cerium and Neodymium in Uranyl Phases

    SciTech Connect

    Kim, C W.; Wronkiewicz, David J.; Finch, R J.; Buck, Edgar C.

    2006-07-15

    The potential for incorporating rare earth elements (REE) into/onto crystalline compounds has been evaluated by precipitating uranyl phases from aqueous solutions containing either cerium or neodymium. These REEs serve both as monitors for evaluating the potential repository behavior of REE radionuclides, and as surrogate elements for actinides (e.g., Ce4 and Nd3 for Pu4 and Am3, respectively). The present experiments examined the behavior of REE in the presence of ianthinite Formula Not Shown, becquerelite (Ca(UO2)6O4(OH)6(H2O)8), and other uranyl hydroxide compounds commonly noted as alteration products during the corrosion of UO2, spent nuclear fuel, and naturally occurring uraninite. The results of these experiments demonstrate that significant quantities of both cerium (Kd=1020) and neodymium (Kd=840) are incorporated within the uranium alteration phases and suggest that ionic substitution and/or adsorption to the uranyl phases can play a key role in the limiting the mobility of REE (and by analogy, actinide elements) in a nuclear waste repository.

  12. How are Centrosymmetric and Noncentrosymmetric Structures Achieved in Uranyl Borates?

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-01-01

    Four uranyl borates, UO{sub 2}B{sub 2}O{sub 4} (UBO-1), ?-(UO{sub 2}){sub 2}[B{sub 9}O{sub 14}(OH){sub 4}] (UBO-2), ?-(UO{sub 2}){sub 2}[B{sub 9}O{sub 14}(OH){sub 4}] (UBO-3), and (UO{sub 2}){sub 2}[B{sub 13}O{sub 20}(OH){sub 3}]1.25H{sub 2}O (UBO-4), have been prepared from boric acid fluxes at 190 C. UBO-3 and UBO-4 are centrosymmetric, whereas UBO-1 and UBO-2 are noncentrosymmetric (chiral and polar). These uranyl borates possess layered structures constructed from UO{sub 8} hexagonal bipyramids, BO{sub 3} triangles, and BO{sub 4} tetrahedra. In the case of UBO-4, clusters of BO{sub 3} triangles link the layers together to form open slabs with a thickness of almost 2 nm. The ability of uranyl borates to use very similar layers to yield both centrosymmetric and noncentrosymmetric layers is detailed in this work.

  13. Ezrin-anchored Protein Kinase A Coordinates Phosphorylation-dependent Disassembly of a NHERF1 Ternary Complex to Regulate Hormone-sensitive Phosphate Transport*

    PubMed Central

    Wang, Bin; Means, Chris K.; Yang, Yanmei; Mamonova, Tatyana; Bisello, Alessandro; Altschuler, Daniel L.; Scott, John D.; Friedman, Peter A.

    2012-01-01

    Congenital defects in the Na/H exchanger regulatory factor-1 (NHERF1) are linked to disordered phosphate homeostasis and skeletal abnormalities in humans. In the kidney, these mutations interrupt parathyroid hormone (PTH)-responsive sequestration of the renal phosphate transporter, Npt2a, with ensuing urinary phosphate wasting. We now report that NHERF1, a modular PDZ domain scaffolding protein, coordinates the assembly of an obligate ternary complex with Npt2a and the PKA-anchoring protein ezrin to facilitate PTH-responsive cAMP signaling events. Activation of ezrin-anchored PKA initiates NHERF1 phosphorylation to disassemble the ternary complex, release Npt2a, and thereby inhibit phosphate transport. Loss-of-function mutations stabilize an inactive NHERF1 conformation that we show is refractory to PKA phosphorylation and impairs assembly of the ternary complex. Compensatory mutations introduced in mutant NHERF1 re-establish the integrity of the ternary complex to permit phosphorylation of NHERF1 and rescue PTH action. These findings offer new insights into a novel macromolecular mechanism for the physiological action of a critical ternary complex, where anchored PKA coordinates the assembly and turnover of the Npt2a-NHERF1-ezrin complex. PMID:22628548

  14. Syntheses, structures, photoluminescence of four dicarboxylate-controlled Zn(II) coordination complexes incorporating flexible 1-(4-pyridylmethyl)-benzimidazole ligand

    NASA Astrophysics Data System (ADS)

    Hao, Hong-Jun; Du, Ming-Yue; Wang, Dan-Feng; Sun, Cheng-Jie; Wang, Zhan-Hui; Huang, Rong-Bin; Zheng, Lan-Sun

    2013-09-01

    Four Zn(II) coordination complexes, namely {[Zn(pmbm)2(tpa)]H2O}n (1), {[Zn(pmbm)(phda)]2(H2O)}n (2), [Zn(pmbm)(aze)]n (3), {[Zn(pmbm)(1,4-ndc)]2(CH3OH)}n (4) [pmbm = 1-(4-pyridylmethyl)-benzimidazole, H2tpa = terephthalic acid, H2phda = phenylenediacetic acid, H2aze = azelaic acid, 1,4-ndcH2 = 1,4-naphthalenedicarboxylic acid] have been synthesized by solution phase ultrasonic reactions of Zn(AC)22H2O with pmbm and various dicarboxylates ligands under the ammoniacal condition. All the complexes have been characterized by elemental analyses, IR spectra and X-ray diffraction. Complexes 1 and 2 exhibit one-dimensional chains structure and complex 3 and 4 are two-dimensional sheets structure with (4,4) topology. Complexes 1-4 spanning from one-dimensional chains to two-dimensional sheets suggest that dicarboxylates play significant roles in the formation of such coordination architectures. The photoluminescences of the complexes were also investigated in the solid state at room temperature.

  15. Synthesis and characterization of uranyl chromate sheet compounds containing edge-sharing dimers of uranyl pentagonal bipyramids

    SciTech Connect

    Unruh, Daniel K.; Baranay, Michelle; Pressprich, Laura; Stoffer, Megan [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil Engineering and Geological Sciences, 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2012-02-15

    Eight uranyl chromates have been crystallized from aqueous solution and characterized: Mg(H{sub 2}O){sub 6}[(UO{sub 2}){sub 2}(CrO{sub 4}){sub 2}(OH){sub 2}](H{sub 2}O){sub 3} (1), (NH{sub 4}){sub 2}[(UO{sub 2}){sub 2}(CrO{sub 4}){sub 2}(OH){sub 2}](H{sub 2}O){sub 3}, Rb{sub 2}[(UO{sub 2}){sub 2}(CrO{sub 4}){sub 2}(OH){sub 2}](H{sub 2}O){sub 3} (3), Cs[(UO{sub 2})(CrO{sub 4})(OH)]H{sub 2}O (4), Rb[(UO{sub 2})(CrO{sub 4})(OH)]H{sub 2}O (5) Co(H{sub 2}O){sub 4}(Co(H{sub 2}O){sub 6}){sub 2}[(UO{sub 2}){sub 4}(CrO{sub 4}){sub 6}(OH){sub 2}](H{sub 2}O){sub 4} (6), Li{sub 2}[(UO{sub 2}){sub 2}(CrO{sub 4}){sub 3}](H{sub 2}O){sub 7} (7), and Zn(H{sub 2}O){sub 6}[(UO{sub 2}){sub 2}(CrO{sub 4}){sub 3}](H{sub 2}O){sub 3} (8). The structural units of 1 through 8 each consist of a sheet of uranyl pentagonal bipyramids and (Cr(VI)O{sub 4}){sup 2-} tetrahedra. In each case two uranyl pentagonal bipyramids share an equatorial edge, giving a dimer that is linked into the sheet through vertex sharing with (Cr(VI)O{sub 4}){sup 2-} tetrahedra. The sheets are based upon three distinct sheet anion topologies, and the sheets based on a given anion topology can differ in the orientations of the non-bridging O atoms of (CrO{sub 4}){sup 2-} tetrahedra. The interlayers of these compounds contain either monovalent or divalent cations, as well as H{sub 2}O groups that are either bonded to the interlayer cation or are held in place by H bonding only. We explore the relationships between sheet topologies and interlayer configuration in these compounds. - Graphical abstract: Eight uranyl chromate compounds containing sheet structural units built from uranyl pentagonal bipyramids and (CrO{sub 4}){sup 2-} tetrahedra are reported. Relationships between sheet topologies and interstitial constituents is examined. Highlights: Black-Right-Pointing-Pointer Eight uranyl Cr(VI) compounds with sheet structural units are reported. Black-Right-Pointing-Pointer Relationships between the topology of the uranyl chromate sheets and interlayers are examined. Black-Right-Pointing-Pointer Uranyl and chromate polyhedra form a topologically novel sheet.

  16. Stereoselective Polymerization of rac-Lactide Catalyzed by Zinc Complexes with Tetradentate Aminophenolate Ligands in Different Coordination Patterns: Kinetics and Mechanism.

    PubMed

    Yang, Yang; Wang, Haobing; Ma, Haiyan

    2015-06-15

    A series of monomeric zinc silylamido complexes bearing [NNNO]-type tetradentate aminophenolate ligands, LZnN(SiMe3)2 [L = {(2-R(1))ArCH2N[(CH2)2R(2)]CH2(4-R(4)-6-R(3))C6H2O-}, R(1) = NMe2, R(2) = N(i)Pr2, R(3) = R(4) = Cl (1), R(3) = R(4) = cumyl (3); R(1) = NMe2, R(2) = NEt2, R(3) = R(4) = cumyl (2), R(3) = CPh3, R(4) = Me (4); R(1) = NEt2, R(2) = NEt2, R(3) = CPh3, R(4) = Me (5); R(1) = NMe2, R(2) = (S)-1-butylpyrrolidin-2-yl, R(3) = R(4) = cumyl (6), R(3) = CPh3, R(4) = Me (7)], have been synthesized via reactions of Zn[N(SiMe3)2]2 and 1 equiv of the corresponding aminophenols. The monomeric nature and versatile coordination patterns of these complexes in the solid state were further confirmed by X-ray diffraction studies on complexes 2, 3, 5, and 7. In complex 3, the N,N-diisopropylamino group on the pendant side arm does not coordinate to the metal center; only the remaining three donors of the aminophenolate ligand and the silylamido group interact with the zinc center. By contrast, in complexes 2, 5, and 7, the amino group of the aryl moiety does not coordinate to the metal center, while the amino group on the pendant side arm coordinates. At room temperature, the above-mentioned structural features of these complexes are retained in solution, as confirmed by (1)H NMR spectroscopy. Complexes 1-7 proved to be efficient initiators for the ring-opening polymerization of rac-lactide (rac-LA) at ambient temperature, and the polymerizations were better controlled in the presence of 2-propanol. The coordination pattern of the aminophenolate ligand exerted a significant influence on the stereoselectivity of the corresponding complex toward the polymerization of rac-LA, leading to the production of heterotactic biased polylactides (PLAs) by complexes 1 and 3 (Pm = 0.40-0.46) and moderately to highly isotactic PLAs by complexes 2 and 4-7 (Pm = 0.70-0.81). Detailed kinetic investigations revealed a first-order dependence on the monomer concentration for all complexes and different orders in the initiator concentration ranging from 1.78 to 1.81. The nature of the solvent as well as the molar ratio of the zinc complex and 2-propanol also displayed certain influence on the order of rac-LA polymerization in the initiator concentration. Factional orders of 1.80, 1.38, and 1.11 were obtained by using complex 5/(i)PrOH (1:1) in toluene and tetrahydrofuran and complex 5/(i)PrOH (1:2) in toluene, respectively. On the basis of DOSY and (1)H and (13)C NMR studies of zinc alkoxide model complexes "LZn(OCMe2COOMe)" as well as the fractional orders of 1.78-1.81 in the initiator concentration, activation/insertion processes likely involving more than one monomeric active species were then hypothesized. PMID:25996447

  17. 4f4f absorption spectra and hypersensitivity in nine-coordinate Ho(III) and Er(III) complexes in different environments

    Microsoft Academic Search

    Azad A Khan; H. A Hussain; K Iftikhar

    2004-01-01

    The effect of change in the environment upon 4f4f absorption spectra of nine-coordinate Ho(III) and Er(III) complexes with thiocyanate and 2,2?-bipyridyl in methanol, DMSO, DMF and pyridine have been investigated. The oscillator strength for hypersensitive and non-hypersensitive transitions have been calculated and variation in the intensity and band shape with respect to solvent type is rationalized in terms of solvent

  18. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters.

    PubMed

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(?-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M2(?2-NO)]; (c) threefold nitrosyl bridges, [M3(?3-NO)]; (d) ?/?-dihaptonitrosyls or "side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 ?/1.60-1.90 ?/180-160 and for bent nitrosyls are 1.16-1.22 ?/1.80-2.00 ?/140-110. The [M2(?2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M?M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 ?/1.18-1.22 ?/1.80-2.00 ?/90-70, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 ?/1.20-1.24 ?/1.90-2.10 ?/130-110. In both situations the N-O vector is approximately at right angle to the M-M (or M?M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 ?/1.80-1.90 ?, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the "effective atomic number (EAN)" or "18-electron" rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ?(NO)-values. The wide wavenumber range found for the ?(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm(-1)] whereas for a unit negative charge it is [minus 145 cm(-1)]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm(-1)]; terminal halogens [plus 30 cm(-1)]; bridging or quasi-bridging halogens [plus 15 cm(-1)]. (c) For electro donating co-ligands they are: PF3 [plus 10 cm(-1)]; P(OPh)3 [-30 cm(-1)]; P(OR)3 (R=alkyl group) [-40 cm(-1)]; PPh3 [-55 cm(-1)]; PR3 (R=alkyl group) [-70 cm(-1)]; and ?5-C5H5 [-60 cm(-1)]; ?5-C5H4Me [-70 cm(-1)]; ?5-C5Me5 [-80 cm(-1)]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted 'neutral-co-ligand' ?(NO)*-values (in cm(-1)) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (5s4d5p): [1730 Mo(NO)]; [-, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [-, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solu

  19. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

    NASA Astrophysics Data System (ADS)

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(?-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M 2(? 2-NO)]; (c) threefold nitrosyl bridges, [M 3(? 3-NO)]; (d) ?/?-dihaptonitrosyls or " side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 /1.60-1.90 /180-160 and for bent nitrosyls are 1.16-1.22 /1.80-2.00 /140-110. The [M 2(? 2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 /1.18-1.22 /1.80-2.00 /90-70, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 /1.20-1.24 /1.90-2.10 /130-110. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M 3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 /1.80-1.90 , respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the " effective atomic number (EAN)" or "18-electron" rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ?(NO)-values. The wide wavenumber range found for the ?(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm -1] whereas for a unit negative charge it is [minus 145 cm -1]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm -1]; terminal halogens [plus 30 cm -1]; bridging or quasi-bridging halogens [plus 15 cm -1]. (c) For electro donating co-ligands they are: PF 3 [plus 10 cm -1]; P(OPh) 3 [-30 cm -1]; P(OR) 3 (R = alkyl group) [-40 cm -1]; PPh 3 [-55 cm -1]; PR 3 (R = alkyl group) [-70 cm -1]; and ? 5-C 5H 5 [-60 cm -1]; ? 5-C 5H 4Me [-70 cm -1]; ? 5-C 5Me 5 [-80 cm -1]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted 'neutral-co-ligand' ?(NO)*-values (in cm -1) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (5s4d5p): [1730 Mo(NO)]; [, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [, Pt] respectively. Environmental differences to these values, e.g. data taken

  20. The metal complexes of amino acids and their N-substituted derivativesVII. The i.r. spectra and normal coordinate analyses of bivalent metal complexes with N-methylglycine and N-phenylglycine

    NASA Astrophysics Data System (ADS)

    Inomata, Yoshie; Shibata, Akio; Yukawa, Yasuhiko; Takeuchi, Toshio; Moriwaki, Takao

    Twelve complexes of bivalent metals with N-methylglycine (sarcosine) and N-phenylglycine have been prepared over wide pH ranges and characterized by means of i.r. powder diffuse reflection, electronic spectra and magnetic susceptibility. These complexes are classified into two types, either with or without chloride ions, from elemental analyses: the former type (A) consists of ML 2 nH 2O (M = Co, Ni, Cu, Zn for L = sarcosinate anion; M = Co, Ni, Cu, Zn, Cd for L = N-phenylglycinate anion), which appear to be octahedral complexes. The metal is coordinated through a nitrogen atom, a carboxyl oxygen atom and water molecules or the carboxyl oxygen atoms of neighboring molecules. The latter type (B) consists of CoCl 2 (HL) 22H 2O, ZnCl 2 (HL) 2 and CdCl 2 (HL) (HL = sarcosine), in which the ligand has a zwitterion structure and has metal ions coordinated through only a carboxyl oxygen atom, but does not chelate through a nitrogen atom. In the cadmium (II) complex, a chloride ion seems to bridge to two cadmium (II) ions. In order to assign the observed frequencies of i.r. spectra in detail, normal coordinate analyses have been carried out for the complexes of the A type. The frequency separation of COO - antisymmetric and symmetric vibrations of A type complexes with sarcosine increases in the order: Co (II) < Ni (II) < Zn (II) < Cu (II). These separations of A type complexes with sarcosine and N-phenylglycine are larger than those of the corresponding complexes with glycine, alanine and other ?-amino acids. The frequencies of metal-nitrogen and metal-oxygen stretching vibrations increase in the order: Co (II) < Zn (II) < Ni (II) < Cu (II) for sarcosine A type complexes.

  1. Synthesis, properties and structures of eight-coordinate zirconium(IV) and hafnium(IV) halide complexes with phosphorus and arsenic ligands.

    PubMed

    Levason, William; Matthews, Melissa L; Patel, Bhavesh; Reid, Gillian; Webster, Michael

    2004-10-21

    Eight-coordinate [MX(4)(L-L)(2)] (M = Zr or Hf; X = Cl or Br; L-L = o-C(6)H(4)(PMe(2))(2) or o-C(6)H(4)(AsMe(2))(2)) were made by displacement of Me(2)S from [MX(4)(Me(2)S)(2)] by three equivalents of L-L in CH(2)Cl(2) solution, or from MX(4) and L-L in anhydrous thf solution. The [MI(4)(L-L)(2)] were made directly from reaction of MI(4) with the ligand in CH(2)Cl(2) solution. The very moisture-sensitive complexes were characterised by IR, UV/Vis, and (1)H and (31)P NMR spectroscopy and microanalysis. Crystal structures of [ZrCl(4)[o-C(6)H(4)(AsMe(2))(2)](2)], [ZrBr(4)[-C(6)H(4)(PMe(2))(2)](2)], [ZrI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] and [HfI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] all show distorted dodecahedral structures. Surprisingly, unlike the corresponding Ti(iv) systems, only the eight-coordinate complex was found in each system. In contrast, the ligand o-C(6)H(4)(PPh(2))(2) forms only six-coordinate complexes [MX(4)[-C(6)H(4)(PPh(2))(2)

  2. Novel Ni(II) and Zn(II) complexes coordinated by 2-arylaminomethyl-1H-benzimidazole: Molecular structures, spectral, DFT studies and evaluation of biological activity

    NASA Astrophysics Data System (ADS)

    Abdel-Ghani, Nour T.; Abo El-Ghar, Maha F.; Mansour, Ahmed M.

    2013-03-01

    [NiL1,2Cl2(OH2)3]zH2O and [ZnL1,2(CH3CO2)2] (L1 = (1H-benzimidazol-2-ylmethyl)-N-phenyl amine, z = 0 and L2 = 2-[(1H-Benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester, z = 1) complexes have been synthesized and characterized by a variety of physico-chemical techniques. The central Ni(II) ion is coordinated by only the pyridine-type nitrogen (Npy) of benzimidazole ring, three water molecules and two chlorido ligands forming a distorted octahedral geometry. Five coordinated zinc complexes were obtained, where the coordination sphere of zinc ion is made up of secondary amino group (NHsec), Npy and two acetate groups, one acts as a unidentate and the other as a bidentate. A theoretical DFT/UB3LYP method combined with LANL2DZ basis set shows that all the metal-ligand bonds are of the L ? M type. Electronic structures have been calculated using TD-DFT method. The antibacterial activity of NiL2 complexes decreases by the introduction of COOCH3 group in the ortho-position of the aniline moiety.

  3. Lanthanide complexes of triethylenetetramine tetra-, penta-, and hexaacetamide ligands as paramagnetic chemical exchange-dependent saturation transfer contrast agents for magnetic resonance imaging: nona- versus decadentate coordination.

    PubMed

    Burdinski, Dirk; Pikkemaat, Jeroen A; Lub, Johan; de Peinder, Peter; Nieto Garrido, Lidia; Weyhermller, Thomas

    2009-07-20

    The solid state and solution structure of a series of lanthanide complexes of the decadentate ligand triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetamide, (ttham), its two decadentate derivatives di-tert-butyl N,N,N''',N'''-tetra(carbamoylmethyl)-triethylenetetramine-N',N''-diacetate (Bu(2)ttha-tm) and N,N,N''',N'''-tetra(carbamoylmethyl)-triethylenetetramine-N',N''-diacetic acid (H(2)ttha-tm), and its two nonadentate derivatives N-benzyl-triethylenetetramine-N,N',N'',N''',N'''-pentaacetamide (1bttpam) and N'-benzyl-triethylenetetramine-N,N,N'',N''',N'''-pentaacetamide (4bttpam) have been investigated by infrared and Raman spectroscopy, X-ray crystallography, cyclovoltammetry, and NMR spectroscopy. In these mononuclear lanthanide complexes, the first coordination sphere is generally saturated by four amine nitrogens of the triethylenetetramine ligand backbone and five or six carbonyl oxygen atoms of the pendent amide or acetate donor groups. In the [Ln(ttham)](3+) complex series, a switch from a decadentate to a nonadentate coordination occurs between [Er(ttham)](3+) and [Tm(ttham)](3+). This switch in coordination mode, which is caused by decreasing metal ion radii going from lanthanum to lutetium (lanthanide contraction), has no significant effect on the T(1)-relaxivity of these complexes. It is shown that the T(1)-relaxivity is dominated by second coordination sphere interactions, with an ascendant contribution of the classical dipolar relaxation mechanism for the earlier (Ce-Sm) and very late (Tm, Yb) lanthanides, and a prevailing Curie relaxation mechanism for most of the remaining paramagnetic lanthanide ions. In chemical exchange-dependent saturation transfer (CEST) (1)H NMR experiments, most of the above complexes exhibit multiple strong CEST peaks of the paramagnetically shifted amide protons spread over a >100 ppm chemical shift range. The effective CEST effect of the studied thulium complexes strongly depends on temperature and pH. The pH at which the CEST effect maximizes (generally between pH 7 and 8) is determined by the overall charge of the complex. Depending on the used saturation frequency offset, the temperature-dependence varies between the extremes of strongly linearly dependent and fully independent in the case of [Tm(ttham)](3+). In combination with the strong pH-dependence of the CEST effect at the latter frequency offset, this complex is highly suitable for simultaneous temperature and pH mapping using magnetic resonance imaging. PMID:19507818

  4. Impact of Coordination Geometry, Bite Angle, and Trans Influence on Metal-Ligand Covalency in Phenyl-Substituted Phosphine Complexes of Ni and Pd.

    PubMed

    Donahue, Courtney M; McCollom, Samuel P; Forrest, Chelsie M; Blake, Anastasia V; Bellott, Brian J; Keith, Jason M; Daly, Scott R

    2015-06-15

    Despite the long-standing use of phosphine and diphosphine ligands in coordination chemistry and catalysis, questions remain as to their effects on metal-ligand bonding in transition metal complexes. Here we report ligand K-edge XAS, DFT, and TDDFT studies aimed at quantifying the impact of coordination geometry, diphosphine bite angle, and phosphine trans influence on covalency in M-P and M-Cl bonds. A series of four-coordinate NiCl2 and PdCl2 complexes containing PPh3 or Ph2P(CH2)nPPh2, where n = 1 (dppm), 2 (dppe), 3 (dppp), and 4 (dppb), was analyzed. The XAS data revealed that changing the coordination geometry from tetrahedral in Ni(PPh3)2Cl2 (1) to square planar in Ni(dppe)Cl2 (2) more than doubles the intensity of pre-edge features assigned to Ni-P and Ni-Cl 1s ? ?* transitions. By way of comparison, varying the diphosphine in Pd(dppm)Cl2 (4), Pd(dppp)Cl2 (6), and Pd(dppb)Cl2 (7) yielded Pd-P 1s ? ?* transitions with identical intensities, but a 10% increase was observed in the P K-edge XAS spectrum of Pd(dppe)Cl2 (5). A similar observation was made when comparing Ni(dppe)Cl2 (2) to Ni(dppp)Cl2 (3), and DFT and TDDFT calculations corroborated XAS results obtained for both series. Comparison of the spectroscopic and theoretical results to the diphosphine structures revealed that changes in M-P covalency were not correlated to changes in bite angles or coordination geometry. As a final measure, P and Cl K-edge XAS data were collected on trans-Pd(PPh3)2Cl2 (8) for comparison to the cis diphosphine complex Pd(dppe)Cl2 (5). Consistent with phosphine's stronger trans influence compared to chloride, a 35% decrease in the intensity of the Pd-P 1s ? ?* pre-edge feature and a complementary 34% increase in Pd-Cl 1s ? ?* feature was observed for 8 (trans) compared to 5 (cis). Overall, the results reveal how coordination geometry, ligand arrangement, and diphosphine structure affect covalent metal-phosphorus and metal-chloride bonding in these late transition metal complexes. PMID:25996554

  5. Synthesis of 2D polymeric dicyanamide bridged hexa-coordinated Cu(II) complex: Structural characterization, spectral studies and TDDFT calculation

    NASA Astrophysics Data System (ADS)

    Konar, Saugata; Saha, Urmila; Dolai, Malay; Chatterjee, Sudipta

    2014-10-01

    A rare 2D polymeric dicyanamide bridged hexa-coordinated copper(II) complex [Cu(L1?)(?1,5-dca)2]n (1) (L1? = 2-carboxypyrazine) has been synthesized from the reaction of Cu(NO3)2?6H2O, 2-pyrazinecarbonitrile (L1) and sodium dicyanamide (Nadca) in methanolic medium. Single crystal X-ray analysis reveals that the complex has a 2D infinite zigzag chain structure in which copper(II) ions are bridged by single dicyanamide ligand in an end-to-end fashion. Such 2-carboxypyrazine can be obtained on the way of metal-assisted nitrile hydrolysis which well connected with Cu(NO3)2?6H2O and dicyanamide (dca) to give rare 2D Cu(II) polymeric complex due to the flexibility in the coordination ability of the copper(II) ions within the polymeric chain. The geometry of the asymmetric unit of the complex was optimized in singlet state by DFT method with multilayer ONIOM model at doublet spin state accordance with repeating asymmetric unit only. The electronic spectrum of the complex is explained using TDDFT calculation.

  6. On the Sensitivity of X-ray Core Spectroscopy to Changes in Metal Ligation: A Systematic Study of Low-Coordinate High-Spin Ferrous Complexes

    PubMed Central

    Chandrasekaran, P.; Chiang, Karen P.; Nordlund, Dennis; Bergmann, Uwe; Holland, Patrick L.; DeBeer, Serena

    2014-01-01

    In order to assess the sensitivity and complementarity of X-ray absorption and emission spectroscopies for determining changes in the metal ligation sphere, a systematic experimental and theoretical study of iron model complexes has been carried out. A series of high-spin ferrous complexes, in which the ligation sphere has been varied from a three coordinate complex, [LtBuFe(SPh)] (1) (where, LtBu = bulky ?-diketiminate ligand; SPh = Phenyl thiolate) to four-coordinate complexes [LtBuFe(SPh)(X)], (where, X = CNtBu (2); 1-Methylimidazole (3); or N,N-dimethylformamide (DMF) (4)), has been investigated using a combination of Fe K-edge X-ray absorption (XAS) and K? X-ray emission (XES) spectroscopies. The Fe K XAS pre-edge and edge of all four complexes are consistent with a high-spin ferrous assignment, with the largest differences in the pre-edge intensities attributed to changes in covalency of the fourth coordination site. The X-ray emission spectra show pronounced changes in the valence to core region (V2C) as the identity of the coordinated ligand is varied. The experimental results have been correlated to DFT calculations, to understand key molecular orbital contributions to the observed absorption and emission features. The calculations also have been extended to a series of hypothetical high-spin iron complexes to understand the sensitivity of XAS and XES techniques to different ligand protonation states ([LtBuFeII(SPh)(NHn)]3-n (n = 3, 2, 1, 0)), metal oxidation states [LtBuFe(SPh)(N)]n- (n = 3, 2, 1), and changes in the ligand identity [LtBuFeIV(SPh)(X)]n- (X = C4-, N3-, O2-; n = 2, 1, 0). This study demonstrates that XAS pre-edge data have greater sensitivity to changes in oxidation state, while valence to core (V2C) XES data provide a more sensitive probe of ligand identity and protonation state. The combination of multiple X-ray spectroscopic methods with DFT results thus has the potential to provide for detailed characterization of complex inorganic systems in both chemical and biological catalysis. PMID:23662855

  7. Impedimetric sensing of uranyl ion based on phosphate functionalized cysteamine self-assembled monolayers

    Microsoft Academic Search

    Reza Karimi Shervedani; Seyed Ahmad Mozaffari

    2006-01-01

    A phosphate functionalized cysteamine self-assembled monolayer based on gold electrode is designed for uranyl ion (UO22+) detection. The response of the modified electrode is studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The EIS data are approximated using constant phase element (CPE) model from which kinetic and analytical parameters are evaluated. Uranyl ion is recognized based on blocking effect

  8. Analyst, July 1996, Vol. 121 (905-908) 905 Uranyl Photophysics on Colloidal Silica: an

    E-print Network

    Strathclyde, University of

    Analyst, July 1996, Vol. 121 (905-908) 905 Uranyl Photophysics on Colloidal Silica: an Alternative of uranyl (UOz2+)in aqueous colloidal silica solution is illustrated and its biexponential decay with time solution. The suitabilityof aqueous colloidal silica as a dispersed medium for enhancing luminescence

  9. Automated Evaluation of Coordination Approaches

    Microsoft Academic Search

    Tibor Bosse; Mark Hoogendoorn; Jan Treur

    2006-01-01

    How to coordinate the processes in a complex component-based software system is a nontrivial issue. Many different coordination approaches exist, each with its own specific advantages and drawbacks. To support their mutual comparison, this paper proposes a formal methodology to automatically evaluate the performance of coordination approaches. This methodology comprises (1) creation of simulation models of coordination approaches, (2) execution

  10. Mdm10 as a dynamic constituent of the TOB\\/SAM complex directs coordinated assembly of Tom40

    Microsoft Academic Search

    Koji Yamano; Sachiko Tanaka-Yamano; Toshiya Endo

    2010-01-01

    The mitochondrial outer membrane contains two protein translocators: the TOM40 and TOB\\/SAM complexes. Mdm10 is distributed in the TOB complex for ?-barrel protein assembly and in the MMM1 complex for tethering of the endoplasmic reticulum and mitochondria. Here, we establish a system in which the Mdm10 level in the TOB complexbut not in the MMM1 complexis altered to analyse its

  11. Structural studies of uranium and thorium complexes with 4,5-dihydroxy-3,5-benzenesdisulfonate (Tiron) at low and neutral pH by X-ray absorption spectroscopy.

    PubMed

    Sylwester, E R; Allen, P G; Dharmawardana, U R; Sutton, M

    2001-06-01

    We have determined the structure of uranyl, UO(2)(2+), and Th(4+) complexes formed in aqueous solution with 4,5-dihydroxy-3,5-benzenedisulfonate (Tiron) as function of pH and concentration. At equimolar concentrations of 0.05 M UO(2)(2+) and Tiron, the predominant species was found to be aqueous uranyl at pH = 2.0. At pH = 6.0, the formation of a 3:3 UO(2)(2+):Tiron trimer (proposed in earlier studies) was observed. In this structure, bidentate catecholate complexation to Tiron as well as oxygen bridging between uranyl units is detected. Th(4+) structural changes were observed both as a function of pH and Th:L (L = Tiron) ratio. At Th:L = 1:1 and pH = 1.4, a monomeric complex is observed with each Th center complexing monodentate to approximately 2 sulfonate functional groups. At pH 4.0 similar sulfonate ligation is observed along with oligomer formation. At pH 6.0 thorium hydrolysis products are detected, with little evidence for inner-sphere Tiron coordination. When the Th:L is changed to 1:2 at pH = 6.0, a stable oligomeric complex is formed that dominates the speciation for Th:L ratios up to 1:5. This complex is characterized by bidentate catechol and monodentate sulfonate ligation to Tiron along with oxygen bridging between Th(4+) atoms and is consistent with the formation of the 2:3 Th:L polymeric species proposed from earlier work. At a Th:L ratio of 1:10, Th(4+) complexation is dominated by bidentate catechol ligation and the formation of a monomeric Th(Tiron)(x) species, where x > or = 2. PMID:11375702

  12. 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

    2015-07-01

    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. PMID:26090963

  13. Synthesis, characterization, and in vitro evaluation of new coordination complexes of platinum(II) and rhenium(I) with a ligand targeting the translocator protein (TSPO).

    PubMed

    Margiotta, Nicola; Denora, Nunzio; Piccinonna, Sara; Laquintana, Valentino; Lasorsa, Francesco Massimo; Franco, Massimo; Natile, Giovanni

    2014-11-21

    The 18 kDa translocator protein (TSPO) is overexpressed in many types of cancers and is also abundant in activated microglial cells occurring in inflammatory neurodegenerative diseases. The TSPO-selective ligand 2-(8-(2-(bis-(pyridin-2-yl-methyl)amino)acetamido)-2-(4-chlorophenyl)H-imidazo[1,2-a]pyridin-3-yl)-N,N-dipropylacetamide (CB256), which fulfills the requirements of a bifunctional chelate approach, has been used to synthesize coordination complexes containing either Pt (1) or Re (3), or both metal ions (2). The new metal complexes showed a cellular uptake markedly greater than that of the precursor metallic compounds and were also able to induce apoptosis in C6 glioma cells. The good cytotoxicity of the free ligand CB256 towards C6, A2780, and A2780cisR tumor cell lines was attenuated after coordination of the dipicolylamine moiety to Pt while coordination of the imidazopyridine residue to Re reduces the affinity towards TSPO. The results of the present investigation are essential for the design of new imidazopyridine bifunctional chelate ligands targeted to TSPO. PMID:25069996

  14. Coordination Chemistry of Polyaromatic Thiosemicarbazones 2: Synthesis and Biological Activity of Zinc, Cobalt, and Copper Complexes of 1-(Naphthalene-2-yl)ethanone Thiosemicarbazone

    PubMed Central

    LeBlanc, Marc-Andre; Gonzalez-Sarras, Antonio; Beckford, Floyd A.; Mbarushimana, P. Canisius; Seeram, Navindra P.

    2012-01-01

    A novel thiosemicarbazone from 2-acetonaphthone (represented as acnTSC) has been synthesized and its basic coordination chemistry with zinc(II), cobalt(II), and copper(II) explored. The complexes were characterized by elemental analysis and various spectroscopic techniques and are best formulated as [M(acnTSC)2Cl2] with the metal likely in an octahedral environment. The anticancer activity of the complexes was determined against a panel of human colon cancer cells (HCT-116 and Caco-2). The compounds bind to DNA via an intercalative mode with binding constants of 9.7 104 M?1, 1.8 105 M?1, and 9.5 104 M?1 for the zinc, cobalt, and copper complexes, respectively. PMID:22303515

  15. Synthesis, characterization, and antitumor activity of unusual pseudo five coordinate gold(III) complexes: distinct cytotoxic mechanism or expensive ligand delivery systems?

    PubMed

    Olsen, Pauline M; Ruiz, Charles; Lussier, Daniel; Le, Brian Khoa; Angel, Noah; Smith, Michelle; Hwang, Chihyun Brian; Khatib, Raneen; Jenkins, Julia; Adams, Kaitlyn; Getcher, Jonathan; Tham, Fook; Chen, Zhou Georgia; Wilson, Emma H; Eichler, Jack F

    2014-12-01

    Gold(III) complexes bearing bidentate ligands based on the 1,10-phenanthroline and 2,2'-bipyridine scaffolds have shown promising anticancer activity against a variety of tumor cell lines. In particular, our laboratory has previously found that a pseudo five coordinate gold(III) complex possessing the 2,9-di-sec-butyl-1,10-phenanthroline ligand {[((di-sec-butyl)phen)AuCl3]} exhibits antitumor activity against a panel of five different lung and head-neck tumor cell lines. However, the [((di-sec-butyl)phen)AuCl3] complex was determined to be less active than the free 2,9-di-sec-butyl-1,10-phenanthroline ligand. In order to determine if this class of gold(III) complexes has a distinct mechanism of initiating tumor cell death or if these gold complexes simply release the polypyridyl ligand in the intracellular environment, structural analogues of the [((di-sec-butyl)phen)AuCl3] complex have been synthesized and structurally characterized. These structural congeners were prepared by using mono-alkyl and di-phenyl substituted 1,10-phenanthroline ligands, di-alkyl and di-phenyl substituted 4-methyl-1,10-phenanthroline ligands, and mono-alkyl 2,2'-bipyridine ligands. The redox stability of this library of distorted square pyramidal gold(III) complexes has been studied and the in vitro antitumor activity of gold(III) complexes and corresponding polypyridyl ligands has been determined. The [((di-n-butyl)phen)AuCl3] and [((mono-n-butyl)phen)AuCl3] complexes have been found to be significantly more potent at inhibiting the growth of A549 lung tumor cells than the clinically used drug cisplatin. More importantly, these two gold(III) complexes are significantly more active than their respective free ligands, providing evidence that this class of pseudo five coordinate gold(III) complexes has a mechanism of initiating tumor cell death that is independent of the free ligand. PMID:25243390

  16. Unusual sevenfold coordination of Ru in complex hydride Na3RuH7: Prospect for formation of [FeH7]3- anion

    NASA Astrophysics Data System (ADS)

    Takagi, Shigeyuki; Ikeshoji, Tamio; Matsuo, Motoaki; Sato, Toyoto; Saitoh, Hiroyuki; Aoki, Katsutoshi; Orimo, Shin-ichi

    2013-09-01

    We used density-functional calculations to clarify the origin of the unusual sevenfold coordination of Ru by H in Na3RuH7. We found that the D5h symmetry of the ligands enables the formation of strong covalent bonds of Ru and H through ligand-field effects, stabilizing the sevenfold coordination. We also examined the possible synthesis of the hypothetical 3d analog, Li3FeH7, which has a gravimetric hydrogen density of 8.4 mass%. The calculated enthalpy change of -16 kJ/mol H2 for the reaction, 3LiH+Fe+2H2?Li3FeH7, reveals a possible route to a stable complex hydride containing [FeH7]3-.

  17. Thiocyanate complexes of uranium in multiple oxidation states: a combined structural, magnetic, spectroscopic, spectroelectrochemical, and theoretical study.

    PubMed

    Hashem, Emtithal; Platts, James A; Hartl, Frantiek; Lorusso, Giulia; Evangelisti, Marco; Schulzke, Carola; Baker, Robert J

    2014-08-18

    A comprehensive study of the complexes A4[U(NCS)8] (A = Cs, Et4N, (n)Bu4N) and A3[UO2(NCS)5] (A = Cs, Et4N) is described, with the crystal structures of [(n)Bu4N]4[U(NCS)8]2MeCN and Cs3[UO2(NCS)5]O0.5 reported. The magnetic properties of square antiprismatic Cs4[U(NCS)8] and cubic [Et4N]4[U(NCS)8] have been probed by SQUID magnetometry. The geometry has an important impact on the low-temperature magnetic moments: at 2 K, ?eff = 1.21 ?B and 0.53 ?B, respectively. Electronic absorption and photoluminescence spectra of the uranium(IV) compounds have been measured. The redox chemistry of [Et4N]4[U(NCS)8] has been explored using IR and UV-vis spectroelectrochemical methods. Reversible 1-electron oxidation of one of the coordinated thiocyanate ligands occurs at +0.22 V vs Fc/Fc(+), followed by an irreversible oxidation to form dithiocyanogen (NCS)2 which upon back reduction regenerates thiocyanate anions coordinating to UO2(2+). NBO calculations agree with the experimental spectra, suggesting that the initial electron loss of [U(NCS)8](4-) is delocalized over all NCS(-) ligands. Reduction of the uranyl(VI) complex [Et4N]3[UO2(NCS)5] to uranyl(V) is accompanied by immediate disproportionation and has only been studied by DFT methods. The bonding in [An(NCS)8](4-) (An = Th, U) and [UO2(NCS)5](3-) has been explored by a combination of DFT and QTAIM analysis, and the U-N bonds are predominantly ionic, with the uranyl(V) species more ionic that the uranyl(VI) ion. Additionally, the U(IV)-NCS ion is more ionic than what was found for U(IV)-Cl complexes. PMID:25072532

  18. Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination

    SciTech Connect

    Samuel Traina; Shankar Sharma

    2005-07-12

    The Department of Energy has a goal of decontaminating an estimated 180,000 metric tons of metal wastes in various surplus facilities. Uranium (U) and other radioactive actinides and lanthanides are embedded within the mixed oxide structures of the passivity layers of corroded iron and steel. These toxic metals can be dissolved out of the surface layers by a naturally occurring bacterial siderophore called Desferrioxamine B (DFB). DFB is a trihydroxamate ligand with one amine and three hydroxamate groups, which chelates with metals through hydroxamate coordination. Complexation of DFB with U can be utilized in decontamination strategy of the passivity layers. Therefore, we have been studying reactions of uranyl U(VI) with zerovalent iron (Fe0) followed by dissolution by DFB. The objectives were to determine the structure and speciation of solution and solid phases of U and to assess the effectiveness of DVB in U dissolution.

  19. Controlling Proton Movement: Electrocatalytic Oxidation of Hydrogen by a Nickel(II) Complex Containing Proton Relays in the Second and Outer Coordination Spheres

    SciTech Connect

    Das, Partha Pratim; Ho, Ming-Hsun; O'Hagan, Molly J.; Shaw, Wendy J.; Bullock, R. Morris; Raugei, Simone; Helm, Monte L.

    2014-02-21

    A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(PCy2N(CH2)2OMe)2, (PCy2N(CH2)2OMe = 1,5-di(methoxyethyl)-3,7-dicy?clohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to? the Ni(II) complex results in rapid formation of three isomers of the doubly protonated ?Ni(0) complex, [Ni(PCy2N(CH2)2OMe2H)2]2+. The three isomers show fast intramolecular interconversion at 40 ?C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s?1 and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(PCy2NBn)2 complex, the new complex operates at a faster rate and at a lower overpotential. The results of this study indicate that the presence of the pendant methoxy group in the outer coordination sphere of the catalyst plays a key role, facilitating intramolecular proton movement prior to intermolecular proton removal required to complete the catalytic cycle. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  20. Synthesis, characterization, and magnetism of divalent aryl transition-metal complexes of the simplest dialkylamide, NMe(2): rare T-shaped coordination at chromium.

    PubMed

    Ni, Chengbao; Long, Gary J; Grandjean, Fernande; Power, Philip P

    2009-12-21

    The synthesis and characterization of a series of first-row aryl transition metal derivatives of the simplest dialkylamido ligand NMe(2) are reported. The complexes Cr{Ar'Cr(mu-NMe(2))(2)}(2) (1) and {Ar'M(mu-NMe(2))}(2) (M = Mn (2), Fe (3); Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) were obtained by reaction of the aryl metal halides {Ar'M(mu-X)}(2) (M = Cr, X = Cl; M = Fe, X = Br) or {Li(THF)Ar'MnI(2)}(2) with LiNMe(2) in a 1:2 ratio. A similar reaction of {Ar(#)Co(mu-I)}(2) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2)) and LiNMe(2) in hexanes gave the unusual complex {Ar(#)Co(mu-I)(eta(1)-CH(2) horizontal lineNCH(3))}(2) (4), in which the NMe(2) ligand is dehydrogenated to afford a complexed imine. Complexes 1-4 were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. In the unique trinuclear complex 1, the central chromium(II) ion is bound to four NMe(2) groups in a square planar fashion. The NMe(2) groups also bridge to the two outer chromium(II) ions, which are bound to a terminal Ar' group to yield a rare example of three-coordinate T-shaped geometry at these atoms. In the dimers 2 and 3, each metal center is coordinated to a terminal terphenyl ligand and two bridging NMe(2) groups to give a distorted trigonal planar geometry. In contrast, the reaction of LiNMe(2) with {Ar(#)Co(mu-I)}(2) in a 2:1 ratio did not yield an amido product; instead, the NMe(2) ligand underwent hydrogen elimination. As a result, in the dimeric structure of 4, each cobalt ion is coordinated to a terphenyl ligand, two bridging iodides, and a neutral methylimine ligand, CH(2) horizontal lineNCH(3), to yield a very distorted tetrahedral cobalt(II) coordination environment. The magnetic properties of 1-4 revealed antiferromagnetic exchange coupling between the metal ions with J = -47(1) cm(-1) and J(13) = -25(1) cm(-1) for 1, J = -38(1) cm(-1) for 2, J = -75(3) cm(-1) for 3, and J = -32(4) cm(-1) for 4; the latter compound exhibited an unusually large temperature independent contribution to its molar magnetic susceptibility. PMID:20000648

  1. Zirconium and hafnium complexes containing N-alkyl substituted amine biphenolate ligands: coordination chemistry and living ring-opening polymerization catalysis.

    PubMed

    Liang, Lan-Chang; Lin, Sheng-Ta; Chien, Chia-Cheng; Chen, Ming-Tsz

    2013-07-01

    The coordination chemistry of zirconium and hafnium complexes containing the tridentate amine biphenolate ligands [RN(CH2-2-O-3,5-C6H2(tBu)2)2](2-) ([R-ONO](2-); R = tBu (1a), iPr (1b), nPr (1c)) featuring distinct N-alkyl substituents is described. Alcoholysis of Zr(OiPr)4(HOiPr) or Hf(OiPr)4(HOiPr) with H2[1a] in diethyl ether solutions at -35 C generates the corresponding five-coordinate [1a]M(OiPr)2 (M = Zr (2a), Hf (3a)) in high isolated yield. Similar reactions employing H2[1b] produce six-coordinate [1b]M(OiPr)2(HOiPr) (M = Zr (2bHOiPr), Hf (3bHOiPr)) as an isopropanol adduct. Repetitive trituration of 2bHOiPr and 3bHOiPr with diethyl ether gives five-coordinate 2b and 3b, respectively. Treatment of M(OiPr)4(HOiPr) with H2[1c] under similar conditions affords six-coordinate [1c]M(OiPr)2(HOiPr) (M = Zr (2cHOiPr), Hf (3cHOiPr)), subsequent recrystallization of which from acetonitrile-diethyl ether solutions leads to acetonitrile adducts 2cMeCN and 3cMeCN. Reactivity studies of these zirconium and hafnium complexes revealed that they are all active catalysts for ring-opening polymerization of ?-caprolactone. Among them, the N-isopropyl derived complexes are most reactive. Polymerizations catalyzed by 2b, 3b and 3cMeCN were proved to be living. The X-ray structures of 2aHOiPr, 2aMeCN, 2cHOiPr, 2cMeCN, and 3cMeCN are presented. PMID:23518868

  2. NH-S hydrogen bonding in zinc enzyme model complex with S 2N 2 binding set studied by normal coordinate analysis of vibrational spectra

    NASA Astrophysics Data System (ADS)

    Shi, Xiao-Feng; Sun, Wei-Yin; Zhang, Li; Li, Chong-De

    2000-02-01

    In order to provide theoretical evidence for the existence and effect of NH-S hydrogen bonding in the zinc enzyme model complex [Zn(S-2-C 6H 4NHCOC 6H 5) 2(1-MeIm) 2] (1-MeIm=1-methylimidazole) in addition to the spectroscopic and crystallographic investigations, normal coordinate analysis (NCA) was carried out using a modified Urey-Bradley force field. The vibrational frequencies of the complex with and without the NH-S hydrogen bonding as well as the corresponding internal coordinates were obtained. The good agreement found between the calculated and observed frequencies in the presence of the NH-S hydrogen bond, supports the reliability of the analysis. The stretching force constant of the NH-S hydrogen bond obtained from the calculation is 0.18 mdyne per . The calculation shows that the N-H bond is weakened by formation of the NH-S hydrogen bond. The results are indicative of the existence of the NH-S hydrogen bond in the complex.

  3. RME-8 coordinates the activity of the WASH complex with the function of the retromer SNX dimer to control endosomal tubulation.

    PubMed

    Freeman, Caroline L; Hesketh, Geoffrey; Seaman, Matthew N J

    2014-05-01

    Retromer is a vital element of the endosomal protein sorting machinery and comprises two subcomplexes that operate together to sort membrane proteins (cargo) and tubulate membranes. Tubules are formed by a dimer of sorting nexins, a key component of which is SNX1. Cargo selection is mediated by the VPS35-VPS29-VPS26 trimer, which additionally recruits the WASH complex through VPS35 binding to the WASH complex subunit FAM21. Loss of function of the WASH complex leads to dysregulation of endosome tubulation, although it is unclear how this occurs. Here, we show that FAM21 also binds to the SNX1-interacting DNAJ protein RME-8. Loss of RME-8 causes altered kinetics of SNX1 membrane association and a pronounced increase in highly branched endosomal tubules. Building on previous observations from other laboratories, we show that these tubules contain membrane proteins that are dependent upon WASH complex activity for their localization to the plasma membrane. Therefore, we propose that the interaction between RME-8 and the WASH complex provides a means to coordinate the activity of the WASH complex with the membrane-tubulating function of the sorting nexins at sites where retromer-mediated endosomal protein sorting occurs. PMID:24643499

  4. Stabilizing coordinated radicals via metal-ligand covalency: a structural, spectroscopic, and theoretical investigation of group 9 tris(dithiolene) complexes.

    PubMed

    Morsing, Thorbjrn J; MacMillan, Samantha N; Uebler, Jacob W H; Brock-Nannestad, Theis; Bendix, Jesper; Lancaster, Kyle M

    2015-04-01

    Proper assignment of redox loci in coordination complexes with redox-active ligands to either the metal or the ligand is essential for rationalization of their chemical reactivity. However, the high covalency endemic to complexes of late, third-row transition metals complicates such assignments. Herein, we systematically explore the redox behavior of a series of group 9 tris(dithiolene) complexes, [M(mnt)3]3 (M = Ir, Rh, Co; mnt = maleonitriledithiolate). The Ir species described comprise the first examples of homoleptic Ir dithiolene complexes. The enhanced metalligand covalency of the IrS interaction leads to remarkable reactivity of [Ir(mnt)3]3 and stabilization of mononuclear [Ir(mnt)3]2 complex ions as well as dimerized versions featuring weak, covalent, intermolecular SS bonds. The dianionic Rh and Co analogues are, in contrast, highly unstable, resulting in the rapid formation of [Rh2(mnt)5]4 and [Co(mnt)2]22, respectively. The synthesized complexes were studied by single-crystal X-ray diffraction, X-ray absorption spectroscopy, optical spectroscopy, magnetometry, density functional theory, and spectroscopy-oriented configuration interaction calculations. Spectroscopic and theoretical analyses suggest that the stability of [Ir(mnt)3]2 may be attributed to dilution of ligand radical character by a high degree of Ir 5d character in the singly occupied molecular orbital. PMID:25756298

  5. RME-8 coordinates the activity of the WASH complex with the function of the retromer SNX dimer to control endosomal tubulation

    PubMed Central

    Freeman, Caroline L.; Hesketh, Geoffrey; Seaman, Matthew N. J.

    2014-01-01

    ABSTRACT Retromer is a vital element of the endosomal protein sorting machinery and comprises two subcomplexes that operate together to sort membrane proteins (cargo) and tubulate membranes. Tubules are formed by a dimer of sorting nexins, a key component of which is SNX1. Cargo selection is mediated by the VPS35VPS29VPS26 trimer, which additionally recruits the WASH complex through VPS35 binding to the WASH complex subunit FAM21. Loss of function of the WASH complex leads to dysregulation of endosome tubulation, although it is unclear how this occurs. Here, we show that FAM21 also binds to the SNX1-interacting DNAJ protein RME-8. Loss of RME-8 causes altered kinetics of SNX1 membrane association and a pronounced increase in highly branched endosomal tubules. Building on previous observations from other laboratories, we show that these tubules contain membrane proteins that are dependent upon WASH complex activity for their localization to the plasma membrane. Therefore, we propose that the interaction between RME-8 and the WASH complex provides a means to coordinate the activity of the WASH complex with the membrane-tubulating function of the sorting nexins at sites where retromer-mediated endosomal protein sorting occurs. PMID:24643499

  6. Free energies and mechanisms of water exchange around Uranyl from first principles molecular dynamics

    SciTech Connect

    Atta-Fynn, Raymond; Bylaska, Eric J.; De Jong, Wibe A.

    2012-02-01

    From density functional theory (DFT) based ab initio (Car-Parrinello) metadynamics, we compute the activation energies and mechanisms of water exchange between the first and second hydration shells of aqueous Uranyl (UO{sub 2}{sup 2+}) using the primary hydration number of U as the reaction coordinate. The free energy and activation barrier of the water dissociation reaction [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) {yields} [UO{sub 2}(OH{sub 2})4]{sup 2+}(aq) + H{sub 2}O are 0.7 kcal and 4.7 kcal/mol respectively. The free energy is in good agreement with previous theoretical (-2.7 to +1.2 kcal/mol) and experimental (0.5 to 2.2 kcal/mol) data. The associative reaction [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) + H{sub 2}O {yields} [UO{sub 2}(OH{sub 2})6]{sup 2+}(aq) is short-lived with a free energy and activation barrier of +7.9 kcal/mol and +8.9 kca/mol respectively; it is therefore classified as associative-interchange. On the basis of the free energy differences and activation barriers, we predict that the dominant exchange mechanism between [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) and bulk water is dissociative.

  7. Mossbauer and FTIR spectroscopic studies of iron anthranilates: coordination, structure and some ecological aspects of iron complexation

    Microsoft Academic Search

    A. A. Kamneva; E. Kuzmann; A. Vertes

    The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mossbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic (o-aminobenzoic) acid,

  8. Mssbauer and FTIR spectroscopic studies of iron anthranilates: coordination, structure and some ecological aspects of iron complexation

    Microsoft Academic Search

    A. A. Kamnev; E. Kuzmann; Yu. D. Perfiliev; Gy. Vank; A. Vrtes

    1999-01-01

    The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mssbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic (o-aminobenzoic) acid,

  9. Spin-filtering, giant magnetoresistance, rectifying and negative differential resistance effects in planar four-coordinate Fe complex with graphene nanoribbon electrodes.

    PubMed

    Zhao, P; Wu, Q H; Liu, D S; Chen, G

    2014-01-28

    By using the nonequilibrium Green's function formalism combined with the density functional theory, we have investigated the spin-polarized transport properties of a planar four-coordinate Fe complex sandwiched between two zigzag-edge graphene nanoribbon (ZGNR) electrodes, where the ZGNRs are modulated by external magnetic field. The results show that the system can exhibit perfect dual spin-filtering and spin-rectifying effects at a wide bias range, giant magnetoresistance effect with large magnetoresistance ratio at small bias, and obvious negative differential resistance behavior. The mechanisms are proposed for these phenomena. PMID:25669527

  10. Spin-filtering, giant magnetoresistance, rectifying and negative differential resistance effects in planar four-coordinate Fe complex with graphene nanoribbon electrodes

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Wu, Q. H.; Liu, D. S.; Chen, G.

    2014-01-01

    By using the nonequilibrium Green's function formalism combined with the density functional theory, we have investigated the spin-polarized transport properties of a planar four-coordinate Fe complex sandwiched between two zigzag-edge graphene nanoribbon (ZGNR) electrodes, where the ZGNRs are modulated by external magnetic field. The results show that the system can exhibit perfect dual spin-filtering and spin-rectifying effects at a wide bias range, giant magnetoresistance effect with large magnetoresistance ratio at small bias, and obvious negative differential resistance behavior. The mechanisms are proposed for these phenomena.

  11. Increase in coordination number of lanthanide complexes with 2,2?-bipyridine and 1,10-phenanthroline by using ?-diketonates with electron-withdrawing groups

    Microsoft Academic Search

    Dave R. van Staveren; Gerard A. van Albada; Jaap G. Haasnoot; Huub Kooijman; Anna Maria Manotti Lanfredi; Peter J. Nieuwenhuizen; Anthony L. Spek; Franco Ugozzoli; Thomas Weyhermller; Jan Reedijk

    2001-01-01

    The coordination chemistry of Ln(hfpd)3 (hfpd=1,1,1,5,5,5-hexafluoropentane-2,4-dionate) with phen and bpy depends on the size of the Ln3+ ion and on the used solvent. The complexes [Er(hfpd)3(phen)] (7) and [Er(hfpd)3(bpy)] (14) were obtained from the synthesis of Er(CF3SO3)3 with Hhfpd, CsOH and either 1,10-phenanthroline or 2,2?-bipyridine in acetonitrile. The structure of 7 was determined by X-ray crystallography. Similar reactions, but performed

  12. Escherichia coli Response to Uranyl Exposure at Low pH and Associated Protein Regulations

    PubMed Central

    Khemiri, Arbia; Carrire, Marie; Bremond, Nicolas; Ben Mlouka, Mohamed Amine; Coquet, Laurent; Llorens, Isabelle; Chapon, Virginie; Jouenne, Thierry; Cosette, Pascal; Berthomieu, Catherine

    2014-01-01

    Better understanding of uranyl toxicity in bacteria is necessary to optimize strains for bioremediation purposes or for using bacteria as biodetectors for bioavailable uranyl. In this study, after different steps of optimization, Escherichia colicells were exposed to uranyl at low pH to minimize uranyl precipitation and to increase its bioavailability. Bacteria were adapted to mid acidic pH before exposure to 50 or 80 M uranyl acetate for two hours at pH?3. To evaluate the impact of uranium, growth in these conditions were compared and the same rates of cells survival were observed in control and uranyl exposed cultures. Additionally, this impact was analyzedby two-dimensional differential gel electrophoresis proteomics to discover protein actors specifically present or accumulated in contact with uranium.Exposure to uranium resulted in differential accumulation of proteins associated with oxidative stress and in the accumulation of the NADH/quinone oxidoreductase WrbA. This FMN dependent protein performs obligate two-electron reduction of quinones, and may be involved in cells response to oxidative stress. Interestingly, this WrbA protein presents similarities with the chromate reductase from E. coli, which was shown to reduce uranyl in vitro. PMID:24587082

  13. Enhanced Adsorption and Recovery of Uranyl Ions by NikR Mutant-Displaying Yeast

    PubMed Central

    Kuroda, Kouichi; Ebisutani, Kazuki; Iida, Katsuya; Nishitani, Takashi; Ueda, Mitsuyoshi

    2014-01-01

    Uranium is one of the most important metal resources, and the technology for the recovery of uranyl ions (UO22+) from aqueous solutions is required to ensure a semi-permanent supply of uranium. The NikR protein is a Ni2+-dependent transcriptional repressor of the nickel-ion uptake system in Escherichia coli, but its mutant protein (NikRm) is able to selectively bind uranyl ions in the interface of the two monomers. In this study, NikRm protein with ability to adsorb uranyl ions was displayed on the cell surface of Saccharomyces cerevisiae. To perform the binding of metal ions in the interface of the two monomers, two metal-binding domains (MBDs) of NikRm were tandemly fused via linker peptides and displayed on the yeast cell surface by fusion with the cell wall-anchoring domain of yeast ?-agglutinin. The NikRm-MBD-displaying yeast cells with particular linker lengths showed the enhanced adsorption of uranyl ions in comparison to the control strain. By treating cells with citrate buffer (pH 4.3), the uranyl ions adsorbed on the cell surface were recovered. Our results indicate that the adsorption system by yeast cells displaying tandemly fused MBDs of NikRm is effective for simple and concentrated recovery of uranyl ions, as well as adsorption of uranyl ions. PMID:24970221

  14. Copper(II)-bis-Histidine Coordination Structure in Fibrillar Amyloid-? Peptide Fragment and Model Complexes Revealed by using Electron Spin Echo Envelope Modulation Spectroscopy

    PubMed Central

    Hernndez-Guzmn, Jessica; Sun, Li; Mehta, Anil K.; Dong, Jijun; Lynn, David G.; Warncke, Kurt

    2013-01-01

    Truncated and mutated amyloid-? (A?) peptides are models for systematic study of the molecular origins of metal ion effects on A? aggregation rates, types of aggregate structures formed, and cytotoxicity, in homogeneous preparations. The 3-D geometry of bis-histidine imidazole coordination of Cu(II) in fibrils of the nonapetide, acetyl-A?(13-21)H14A, is determined by using powder 14N electron spin echo envelope modulation (ESEEM) spectroscopy. The method of simulation of the anisotropic combination modulation is described, and benchmarked for a Cu(II)-bis-cis-imidazole complex of known structure. The revealed bis-cis coordination mode, and mutual orientation of the imidazole rings, for Cu(II) in Ac-A?(13-21)H14A fibrils are consistent with the proposed ?-sheet structural model, and pair-wise peptide interaction with Cu(II), with alternating [metalvacancy]n pattern, along the N-terminal edge. Metal coordination does not significantly distort the intra-?-strand peptide interactions, which provides a rationale for the Cu(II)-acceleration of Ac-A?(13-21)H14A fibrillization, through stabilization of the associated state, and low-reorganization integration of ?-strand peptide pair precursors. PMID:24014287

  15. Template and coordination interactions of 4,4?-bipyridine (Bipy) in nickel(II) complexes of 2-propyl-4,5-dicarboxylate-imidazole

    NASA Astrophysics Data System (ADS)

    Deng, Ji-Hua; Zhong, Di-Chang; Wang, Ke-Jun; Luo, Xu-Zhong; Lu, Wen-Guan

    2013-03-01

    Two nickel(II) complexes, (H2Bipy)0.5[Ni(H2PIDC)3](Bipy)5H2O (1) and [Ni(H2PIDC)2(Bipy)]n (2) (H3PIDC = 2-propyl-4,5-dicarboxylate-imidazole, Bipy = 4,4'-bipyridine), have been solvothermally synthesized and structurally characterized by infrared spectra (IR), elemental analysis, thermogravimetic analysis (TG), and single-crystal/powder X-ray diffraction. The single-crystal X-ray diffraction analysis indicates that 1 is a mononuclear coordination compound, in which the [Ni(H2PIDC)3]- coordination units are connected together through indirect hydrogen interactions to form a 3D supramolecular structure with 1D supramolecular channels. The Bipy and H2Bipy2+, as templates, fill in the channels. 2 is a 1D chain-shaped coordination polymer, in which the Bipy molecules serve as bridging ligand linking the [Ni(H2PIDC)2] units together to form a 1D chain. Through the interactions of intermolecular hydrogen bonds, these 1D chains are further stacked together to form a 3D overpass-like supramolecular network.

  16. Uranyl photoprobing of conformational changes in DNA induced by drug binding.

    PubMed

    Nielsen, P E; Mllegaard, N E; Jeppesen, C

    1990-02-01

    The effect on DNA conformation upon binding of the bis-intercalator, N,N'-diacridinyl spermidine is studied by uranyl mediated DNA photocleavage and gel retardation. It is shown that a characteristic A-tract correlated 10 base pair modulation of the uranyl photocleavage of bent (kinetoplast) DNA is suppressed upon binding of the diacridine. Likewise, the anomalous slow gel electrophoretic migration of bent-DNA is abolished by diacridine binding. At higher diacridine/DNA ratios a DNA conformation in which G-residues become hypersensitive to uranyl photocleavage is induced. PMID:2156513

  17. Removal of uranyl ions from residual waters using some algae types

    NASA Astrophysics Data System (ADS)

    Cecal, Al; Palamaru, I.; Humelnicu, D.; Popa, K.; Salaru, V. V.; Rudic, V.; Gulea, A.

    1999-01-01

    This paper deals with a study on the bioaccumulation of uranyl ions resulted from residual effluents by means of some microbiological collectors: Scenedesmus quadricauda, Anabaena karakumica, Calothrix brevissima, Penicillinium sp, as well as the Glucide extract of Porphyridium cruentum, under various experimental conditions. The retaining degree of the bioaccumulated uranyl ions, as well as the leaching degree, in HCl and H2O media, of the same ions previously retained on algae were established. The retaining degree decreases in the serie: Scenedesmus quadricauda >Anabaena karakumica >Penicillinium sp>Calothrix brevissima. The leaching effect of bioaccumulated uranyl ions is higher in hydrochloric acid than in water.

  18. Investigation of the coordination modes of tris(pyrazolylmethane)\\/1,4,7-trithiacyclononane ruthenium(II) complex ions by electrospray ionization mass spectrometry

    Microsoft Academic Search

    Raul A. Izquierdo; J. Madureira; Catarina I. V. Ramos; M. Graa O. Santana-Marques; Teresa M. Santos

    2011-01-01

    Electrospray ionization mass spectrometry (ESIMS) was used to investigate the coordination modes of the complexes [RuII([9]aneS3)(HCpz3)Cl]Cl, [RuII([9]aneS3)(HCpz3)](Cl)PF6 and [RuII([9]aneS3)(HCpz3)](PF6)2 ([9]aneS3=1,4,7-trithiacyclononane; HCpz3=tris(1-pyrazolyl)methane) in methanol, acetonitrile and methanol\\/water solutions. The complex [RuII([9]aneS3)(HCpz3)Cl]Cl shows a rapidly exchangeable Cl ligand, with formation of a doubly charged ion [RuII([9]aneS3)(HCpz3)]2+, m\\/z 248, but the [RuII([9]aneS3)(HCpz3)Cl]+, m\\/z 531, is also observed and both species still coexist after

  19. A novel hemilabile calix[4],quinoline-based P,N-ligand: coordination chemistry and complex characterisation

    Microsoft Academic Search

    Angelica Marson; Johanneke E. Ernsting; Martin Lutz; Anthony L. Spek; Piet W. N. M. van Leeuwen; Paul C. J. Kamer

    2009-01-01

    The synthesis of the calix[4]arene-based P,N-ligand 3 (5,11,17,23-tetra-tert-butyl-25-[(2-quinolylmethyl)oxy]-26,27,28-(3-phosphorustrioxy)calix[4]arene), in which the nitrogen atom-containing moiety has been introduced at the lower rim of the cavity prior to P-functionalisation, is described and its coordination properties investigated. In the crystal structure, the calix[4]-cavity adopts a cone conformation with an exo orientation of the phosphorus lone pair enabling P-N chelation. 1H, 13C, 31P and

  20. Cobalt(II) chloride complexes with 1,1'-dimethyl-4,4'-bipyrazole featuring first- and second-sphere coordination of the ligand.

    PubMed

    Domasevitch, Konstantin V

    2014-03-01

    In catena-poly[[dichloridocobalt(II)]-?-(1,1'-dimethyl-4,4'-bipyrazole-?(2)N(2):N(2'))], [CoCl2(C8H10N4)]n, (1), two independent bipyrazole ligands (Me2bpz) are situated across centres of inversion and in tetraaquabis(1,1'-dimethyl-4,4'-bipyrazole-?N(2))cobalt(II) dichloride-1,1'-dimethyl-4,4'-bipyrazole-water (1/2/2), [Co(C8H10N4)2(H2O)4]Cl22C8H10N42H2O, (2), the Co(2+) cation lies on an inversion centre and two noncoordinated Me2bpz molecules are also situated across centres of inversion. The compounds are the first complexes involving N,N'-disubstituted 4,4'-bipyrazole tectons. They reveal a relatively poor coordination ability of the ligand, resulting in a Co-pyrazole coordination ratio of only 1:2. Compound (1) adopts a zigzag chain structure with bitopic Me2bpz links between tetrahedral Co(II) ions. Interchain interactions occur by means of very weak C-H...Cl hydrogen bonding. Complex (2) comprises discrete octahedral trans-[Co(Me2bpz)2(H2O)4](2+) cations formed by monodentate Me2bpz ligands. Two equivalents of additional noncoordinated Me2bpz tectons are important as `second-sphere ligands' connecting the cations by means of relatively strong O-H...N hydrogen bonding with generation of doubly interpenetrated pcu (?-Po) frameworks. Noncoordinated chloride anions and solvent water molecules afford hydrogen-bonded [(Cl(-))2(H2O)2] rhombs, which establish topological links between the above frameworks, producing a rare eight-coordinated uninodal net of {4(24).5.6(3)} (ilc) topology. PMID:24594715

  1. Formation in aqueous solution of a non-oxido V(IV) complex with VN6 coordination. Potentiometric, ESI-MS, spectroscopic and computational characterization.

    PubMed

    Lodyga-Chruscinska, Elzbieta; Szebesczyk, Agnieszka; Sanna, Daniele; Hegetschweiler, Kaspar; Micera, Giovanni; Garribba, Eugenio

    2013-10-01

    The behaviour of the system formed by V(IV)O(2+) ion with all-cis-2,4,6-trimethoxycyclohexane-1,3,5-triamine (tmca) was characterized in aqueous solution through the combined application of electron paramagnetic resonance (EPR) and UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), pH-potentiometry and DFT methods. The formation of an unusual non-oxido [V(tmcaH-2)2] species with VN6 coordination, with the ligand in the bianionic form, was demonstrated. The geometry, EPR and UV-Vis spectra and electronic structure of [V(tmcaH-2)2] were simulated with Gaussian 09 and ORCA software and the results were compared with those of similar oxido and non-oxido vanadium(iv) species formed by other polyamine and polyol related ligands, such as 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci), 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci), cis-inositol (ino) and 1,3,5-trideoxy-1,3,5-trimethoxy-cis-inositol (tmci). The results indicate that V(IV)O(2+) species are formed in acid and weakly basic solution and that [V(tmcaH-2)2] is observed above pH 10. In the non-oxido complex, DFT calculations suggest that the two -NH2 groups are in trans position and that the pre-organization of the ligands favours the metal complexation and the formation of the hexa-coordinated species with VN6 coordination. PMID:23893076

  2. Extending the NIF DISCO framework to automate complex workflow: coordinating the harvest and integration of data from diverse neuroscience information resources

    PubMed Central

    Marenco, Luis N.; Wang, Rixin; Bandrowski, Anita E.; Grethe, Jeffrey S.; Shepherd, Gordon M.; Miller, Perry L.

    2014-01-01

    This paper describes how DISCO, the data aggregator that supports the Neuroscience Information Framework (NIF), has been extended to play a central role in automating the complex workflow required to support and coordinate the NIFs data integration capabilities. The NIF is an NIH Neuroscience Blueprint initiative designed to help researchers access the wealth of data related to the neurosciences available via the Internet. A central component is the NIF Federation, a searchable database that currently contains data from 231 data and information resources regularly harvested, updated, and warehoused in the DISCO system. In the past several years, DISCO has greatly extended its functionality and has evolved to play a central role in automating the complex, ongoing process of harvesting, validating, integrating, and displaying neuroscience data from a growing set of participating resources. This paper provides an overview of DISCOs current capabilities and discusses a number of the challenges and future directions related to the process of coordinating the integration of neuroscience data within the NIF Federation. PMID:25018728

  3. A four-dimensional potential energy surface for the Ar-D2O van der Waals complex: Bending normal coordinate dependence.

    PubMed

    Wang, Shenhao; He, Shanshan; Dai, Liangchen; Feng, Eryin; Huang, Wuying

    2015-06-14

    In this paper, we report a four-dimensional potential energy surface (PES) of the Ar-D2O complex. The ab initio calculations are carried out by the coupled-cluster singles and doubles level with noniterative inclusion of connected triples [CCSD(T)] method with a large basis set supplemented with bond functions. The PES includes explicit dependence on the ?2 bending normal coordinate of Q2 the D2O molecule. Two vibrationally averaged PESs with D2O molecule in its ground and first ?2 excited vibrational states are generated by integrating over the Q2 normal coordinate. Based on these two PESs, the bound state energies are determined and used in the infrared spectra prediction. The theoretical frequencies for 104 infrared transitions of ?111(?2 = 1)??000, ?111(?2 = 1)??000, ?110(?2 = 1)??001, and ?101(?2 = 1)??101 of Ar-D2O complex are in good agreement with the available experimental values. PMID:26071710

  4. Extending the NIF DISCO framework to automate complex workflow: coordinating the harvest and integration of data from diverse neuroscience information resources.

    PubMed

    Marenco, Luis N; Wang, Rixin; Bandrowski, Anita E; Grethe, Jeffrey S; Shepherd, Gordon M; Miller, Perry L

    2014-01-01

    This paper describes how DISCO, the data aggregator that supports the Neuroscience Information Framework (NIF), has been extended to play a central role in automating the complex workflow required to support and coordinate the NIF's data integration capabilities. The NIF is an NIH Neuroscience Blueprint initiative designed to help researchers access the wealth of data related to the neurosciences available via the Internet. A central component is the NIF Federation, a searchable database that currently contains data from 231 data and information resources regularly harvested, updated, and warehoused in the DISCO system. In the past several years, DISCO has greatly extended its functionality and has evolved to play a central role in automating the complex, ongoing process of harvesting, validating, integrating, and displaying neuroscience data from a growing set of participating resources. This paper provides an overview of DISCO's current capabilities and discusses a number of the challenges and future directions related to the process of coordinating the integration of neuroscience data within the NIF Federation. PMID:25018728

  5. Long-term kinetics of uranyl desorption from sediments under advective conditions

    NASA Astrophysics Data System (ADS)

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John

    2014-02-01

    Long-term (>4 months) column experiments were performed to investigate the kinetics of uranyl (U(VI)) desorption in sediments collected from the Integrated Field Research Challenge site at the U.S. Department of Energy Hanford 300 Area. The experimental results were used to evaluate alternative multirate surface complexation reaction (MRSCR) approaches to describe the short and long-term kinetics of U(VI) desorption under flow conditions. The surface complexation reaction (SCR) stoichiometry and equilibrium constants and multirate parameters in the MRSCR models were independently characterized in batch and stirred flow-cell reactors. MRSCR models that were either additively constructed using the MRSCRs for individual size fractions, or composite in nature, could effectively describe short-term U(VI) desorption under flow conditions. The long-term desorption results, however, revealed that using the labile U concentration measured by carbonate extraction underestimated desorbable U(VI) and the long-term rate of U(VI) desorption. This study also found that the gravel size fraction (2-8 mm), which is typically treated as nonreactive in modeling U(VI) reactive transport because of low external surface area, can have an important effect on the U(VI) desorption in the sediment. This study demonstrates an approach to effectively extrapolate U(VI) desorption kinetics for field-scale application and identifies important parameters and uncertainties affecting model predictions.

  6. A series of Zn-4f heterometallic coordination polymers and a zinc complex containing a flexible mixed donor dicarboxylate ligand.

    PubMed

    Feng, Xun; Feng, Yu-Quan; Liu, Lang; Wang, Li-Ya; Song, Hong-Liang; Ng, Seik-Weng

    2013-06-01

    A new zinc compound, together with a corresponding series of Zn-4f heterometallic coordination polymers, namely, [Zn(H2PBDA)(PBDA)]n (1), {[Ln2(PBDA)22H2O] [Zn2(PBDA)2Cl2]}n [H2PBDA = 3-(pyridin-3-yl-oxy) benzene-1,2-dicarboxylic acid, and Ln = Pr(2), Nd(3), Eu(4), Gd(5), Dy(6), Ho(7), Er(8)] have been hydrothermally synthesized and characterized systematically. Polymers 2-8 feature two-dimensional (2D) 4,4 networks, containing the original 1D heterometallic double stranded chains composed of [Ln2Zn2(PBDA)2] entities. The extensive hydrogen bonding and ?-? stacking interactions were observed to stabilize the extended architectures. The luminescence emission spectra of the polymers vary depending on the lanthanide(III) ion present. Informative magnetic susceptibility measurements show that the same carboxylate bridging fashion of the PBDA ligand results in the different magnetic properties occurring within the heterometallic coordination polymers. In addition, polymer 6 exhibits an interesting slow magnetic relaxation behavior at lower temperatures. PMID:23549773

  7. Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions

    SciTech Connect

    Stewart, B.D.; Amos, R.T.; Nico, P.S.; Fendorf, S.

    2010-03-15

    Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO{sub 2}{sup 2+} and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO{sub 2}. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, specifically the formation of uranyl-calcium-carbonato complexes, and ferrihydrite on the rate and extent of uranium reduction in complex geochemical systems.

  8. Using low-frequency IR spectra for the unambiguous identification of metal ion-ligand coordination sites in purpose-built complexes

    NASA Astrophysics Data System (ADS)

    Varga, Gbor; Csendes, Zita; Peintler, Gbor; Berkesi, Ott; Sipos, Pl; Plink, Istvn

    2014-03-01

    One of the aims of our long-term research is the identification of metal ion-ligand coordination sites in bioinspired metal ion-C- or N-protected amino acid (histidine, tyrosine, cysteine or cystine) complexes immobilised on the surface of chloropropylated silica gel or Merrifield resin. In an attempt to reach this goal, structurally related, but much simpler complexes have been prepared and their metal ion-ligand vibrations were determined from their low-frequency IR spectra. The central ions were Mn(II), Co(II), Ni(II) or Cu(II) and the ligands (imidazole, isopropylamine, monosodium malonate) were chosen to possess only one-type of potential donor group. The low-frequency IR spectra were taken of the complexes for each ion-ligand combination and the typical metal ion-functional group vibration bands were selected and identified. The usefulness of the obtained assignments is demonstrated on exemplary immobilised metal ion-protected amino acid complexes.

  9. Ultrafiltration of uranyl peroxide nanoclusters for the separation of uranium from aqueous solution.

    PubMed

    Wylie, Ernest M; Peruski, Kathryn M; Weidman, Jacob L; Phillip, William A; Burns, Peter C

    2014-01-01

    Uranyl peroxide cluster species were produced in aqueous solution by the treatment of uranyl nitrate with hydrogen peroxide, lithium hydroxide, and potassium chloride. Ultrafiltration of these cluster species using commercial sheet membranes with molecular mass cutoffs of 3, 8, and 20 kDa (based on polyethylene glycol) resulted in U rejection values of 95, 85, and 67% by mass, respectively. Ultrafiltration of untreated uranyl nitrate solutions using these membranes resulted in virtually no rejection of U. These results demonstrate the ability to use the filtration of cluster species as a means for separating U from solutions on the basis of size. Small-angle X-ray scattering, Raman spectroscopy, and electrospray ionization mass spectrometry confirmed the presence of uranyl peroxide cluster species in solution and were used to characterize their size, shape, and dispersity. PMID:24313601

  10. A simplified method to create quantitative, "fixed" uranyl-contaminated metal coupons.

    PubMed

    McKeown, Catherine K; Davison, Brian H

    2004-05-01

    A method was developed and validated to quantitatively apply and "fix" uranyl contamination onto a metal surface (steel). Simple approaches are needed to create test surfaces in order to quantify contaminant removal or "decon" methods. We used steel discs sized to allow direct and accurate alpha counting in a Ludlum scanner from radioactive contaminants. A typical 3.8-cm-diameter coupon had a depleted uranyl loading of about 0.1 mg U cm with a count of 980 dpm. The resulting alpha radiation was measured with a precision of >97% for the same coupon. The alpha concentration on replicate coupons differed by as much as 9% (standard deviation). This method, based on earlier methods, required a uranyl solution to be dried but lowers the baking temperature to less than 100 degrees C to increase safety in a typical radiological laboratory. A dike was used to provide a uniform coating of the uranyl solution. PMID:15069301

  11. Influence of the coordination environment of zinc(II) complexes of designed Mannich ligands on phosphatase activity: a combined experimental and theoretical study.

    PubMed

    Sanyal, Ria; Guha, Averi; Ghosh, Totan; Mondal, Tapan Kumar; Zangrando, Ennio; Das, Debasis

    2014-01-01

    A mononucleating (HL(1)) and a dinucleating (HL(2)) "end-off" compartmental ligand have been designed and synthesized by controlled Mannich reaction using p-cresol and bis(2-methoxyethyl)amine, and their formation has been rationalized. Six complexes have been prepared on treating HL(1) and HL(2) with Zn(II)X2 (X = Cl(-), Br(-), I(-)) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn2(L(1))2X2] (1-3), while the potential dinucleating ligand generated mononuclear complexes, [Zn(HL(2))X2] (4-6). Four (1-4), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (kcat) in the range 2-10 s(-1) at 25 C. In each case kinetic data analyses have been run by Michaelis-Menten treatment. The efficacy in the order of conversion of substrate to product (p-nitrophenolate ion) follows the trend 1 > 2 > 3 > 4 > 5 > 6, and the ratio of kcat of an analogous dinuclear to mononuclear complex is ?2. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the active site affects the overall rate in the order: Cl(-) > Br(-) > I(-) regardless of nuclearity; (2) dinuclear complexes prevail over the mononuclear ones. PMID:24354306

  12. Polarized x-ray-absorption spectroscopy of the uranyl ion: Comparison of experiment and theory

    SciTech Connect

    Hudson, E.A.; Allen, P.G.; Terminello, L.J. [Glenn T. Seaborg Institute for Transactinium Science, Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States)] [Glenn T. Seaborg Institute for Transactinium Science, Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States); Denecke, M.A.; Reich, T. [Institut fuer Radiochemie, Forschungszentrum Rossendorf, Postfach 510119, D-01314 Dresden (Germany)] [Institut fuer Radiochemie, Forschungszentrum Rossendorf, Postfach 510119, D-01314 Dresden (Germany)

    1996-07-01

    The x-ray linear dichroism of the uranyl ion (UO{sub 2}{sup 2+}) in uranium {ital L}{sub 3}-edge extended x-ray-absorption fine structure (EXAFS), and {ital L}{sub 1}- and {ital L}{sub 3}-edge x-ray-absorption near-edge structure (XANES), has been investigated both by experiment and theory. A striking polarization dependence is observed in the experimental XANES and EXAFS for an oriented single crystal of uranyl acetate dihydrate [UO{sub 2}(CH{sub 3}CO{sub 2}){sub 2}{center_dot}2H{sub 2}O], with the x-ray polarization vector aligned either parallel or perpendicular to the bond axis of the linear uranyl cation (O-U-O). Single-crystal results are compared to experimental spectra for a polycrystalline uranyl acetate sample and to calculations using the {ital ab} {ital initio} multiple-scattering (MS) code FEFF 6. Theoretical XANES spectra for uranyl fluoride (UO{sub 2}F{sub 2}) reproduce all the features of the measured uranyl acetate spectra. By identifying scattering paths which contribute to individual features in the calculated spectrum, a detailed understanding of the {ital L}{sub 1}-edge XANES is obtained. MS paths within the uranyl cation have a notable influence upon the XANES. The measured {ital L}{sub 3}-edge EXAFS is also influenced by MS, especially when the x-ray polarization is parallel to the uranyl species. These MS contributions are extracted from the total EXAFS and compared to calculations. The best agreement with the isolated MS signal is obtained by using nonoverlapped muffin-tin spheres in the FEFF 6 calculation. This contrasts the {ital L}{sub 1}-edge XANES calculations, in which overlapping was required for the best agreement with experiment. {copyright} {ital 1996 The American Physical Society.}

  13. PHYSICOCHEMICAL PROPERTIES OF URANYL NITRATES, NITRIC ACID SOLUTIONS AND DETERMINATION OF THEIR COMPOSITION

    Microsoft Academic Search

    T. A. Slepyan; S. M. Karpacheva

    1960-01-01

    Specific weight, viscosity, electroconductivity, and refractive index of ; uranyl nitrate --nitric acid--water systems in the concentration ranges 0 to 2 M ; uranyl nitrate were investigated. The specific weight was calculated by the ; formula d = d + 0.17c\\/sub U\\/ + 0.029c\\/sub H\\/ with an order of accuracy of ; 0.5%; the index of refraction was calculated by

  14. Differences and comparisons of the properties and reactivities of iron(III)-hydroperoxo complexes with saturated coordination sphere.

    PubMed

    Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frdric; de Visser, Sam P

    2015-01-12

    Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)-oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)-hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)-hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)-hydroperoxo reacted directly with substrates or that an initial O-O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)-hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)-hydroperoxo complex with pentadentate ligand system (L5(2)). Direct C-O bond formation by an iron(III)-hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L5(2))Fe(III)(OOH)](2+) should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)-hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O-O bond, whereas a heterolytic O-O bond breaking in heme iron(III)-hydroperoxo is found. PMID:25399782

  15. Differences and Comparisons of the Properties and Reactivities of Iron(III)hydroperoxo Complexes with Saturated Coordination Sphere

    PubMed Central

    Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frdric; de Visser, Sam P

    2015-01-01

    Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)hydroperoxo reacted directly with substrates or that an initial OO bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)hydroperoxo complex with pentadentate ligand system (L52). Direct CO bond formation by an iron(III)hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L52)FeIII(OOH)]2+ should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the OO bond, whereas a heterolytic OO bond breaking in heme iron(III)hydroperoxo is found. PMID:25399782

  16. Solution equilibrium studies on metal complexes of 2,3-dihydroxy-phenylalanine-hydroxamic acid (Dopaha) and models: catecholate versus hydroxamate coordination in iron(III), aluminium(III) and molybdenum(VI)Dopaha complexes

    Microsoft Academic Search

    Etelka Farkas; Hajnalka Cska

    2002-01-01

    Equilibrium results based on pH potentiometric, spectrophotometric and 1H NMR measurements for the complexes of Fe(III), Al(III) and Mo(VI) with 2,3-dihydroxy-phenylalanine-hydroxamic acid (Dopaha) as well as for binary model systems Fe(III), Al(III), Mo(VI)acetohydroxamic acid (Aha), ?-alaninehydroxamic acid (?-Alaha) and 1,2-dihydroxy-3,5-benzene-disulphonate (Tiron) and ternary model systems Fe(III), Al(III), Mo(VI)TironAha, are summarized in this paper. The amine-type coordination mode is not detectable

  17. Zinc(II) and Cadmium(II) complexes with N4-coordinate pyrazole based ligand: Syntheses, characterization and structure

    NASA Astrophysics Data System (ADS)

    Solanki, Ankita; Sadhu, Mehul H.; Kumar, Sujit Baran; Mitra, Partho

    2014-11-01

    A series of six new mononuclear zinc(II) complexes of the type [Zn(X)(dbdmp)]Y (1-6) (X = N3-/NCO-/NCS-, Y = ClO4-/PF6-, and dbdmp = N,N-diethyl-N?,N?-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine), two binuclear cadmium(II) complexes [{Cd(dbdmp)}2(?-N3)2](Y)2 (7-8) and three mononuclear cadmium(II) complexes [Cd(NCO)(dbdmp)]Y (Y = ClO4-/PF6-) (9-10) and [Cd(NCS)2(dbdmp)] (11) have been synthesized and characterized by physico-chemical methods. Crystal structures of the complexes [Zn(N3)(dbdmp)]ClO4 (1), [{Cd(dbdmp)}2(?-N3)2](ClO4)2 (7), [Cd(NCO)(dbdmp)]ClO4 (9) and [Cd(NCS)2(dbdmp)] (11) have been solved by single crystal X-ray diffraction studies and showed that [Zn(N3)(dbdmp)]ClO4 (1) and [Cd(NCO)(dbdmp)]ClO4 (9) have distorted trigonal bipyramidal geometry, [Cd(NCS)2(dbdmp)] (11) and [(dbdmp)Cd(?-N3)]2(ClO4)2 (7) have distorted octahedral geometry.

  18. Control of emission colour with N-heterocyclic carbene (NHC) ligands in phosphorescent three-coordinate Cu(I) complexes.

    PubMed

    Krylova, Valentina A; Djurovich, Peter I; Conley, Brian L; Haiges, Ralf; Whited, Matthew T; Williams, Travis J; Thompson, Mark E

    2014-07-11

    A series of three phosphorescent mononuclear (NHC)-Cu(I) complexes were prepared and characterized. Photophysical properties were found to be largely controlled by the NHC ligand chromophore. Variation of the NHC ligand leads to emission colour tuning over 200 nm range from blue to red, and emission efficiencies of 0.16-0.80 in the solid state. PMID:24853355

  19. Complexation of Mercury(II) in Soil Organic Matter: EXAFS Evidence for Linear Two-Coordination with Reduced Sulfur Groups

    Microsoft Academic Search

    Ulf Skyllberg; Paul R. Bloom; Jin Qian; Chung-Min Lin; William F. Bleam

    2006-01-01

    The chemical speciation of inorganic mercury (Hg) is to a great extent controlling biologically mediated processes, such as mercury methylation, in soils, sediments, and surface waters. Of utmost importance are complexation reactions with functional groups of natural organic matter (NOM), indirectly determining concentrations of bioavailable, inorganic Hg species. Two previous extended X-ray absorption fine structure (EXAFS) spectroscopic studies have revealed

  20. Coordination complexes exhibiting room-temperature phosphorescence: Evaluation of their suitability as triplet emitters in organic light emitting diodes

    Microsoft Academic Search

    Rachel C. Evans; Peter Douglas; Christopher J. Winscom

    2006-01-01

    The aim of this review is to evaluate the potential of known main-group, transition metal and lanthanide complexes exhibiting room-temperature phosphorescence, either for direct application as dopants in the emissive layer of OLED devices, or as an aid to deduce which structural trends might lead to new materials for this purpose. A systematic analysis of emission characteristics such as wavelength,

  1. Adsorption-induced crystallization of U-rich nanocrystals on nano-Mg(OH)(2) and the aqueous uranyl enrichment.

    PubMed

    Chen, Zhi; Zhuang, Zanyong; Cao, Qing; Pan, Xiaohong; Guan, Xiong; Lin, Zhang

    2014-01-22

    The mechanism of the interaction between nano-Mg(OH)2 adsorbent and uranyl in water was studied. At trace levels, the uranyl is adsorbed as a monolayer on nano-Mg(OH)2, and occupied a small proportion of the adsorption sites. As the uranyl concentration crosses over a threshold, continuous increase of adsorption capacity takes place. It indicates that, by taking the pre-adsorbed uranyl as the nucleation centers, the additional uranyl crystallizes and forms U-rich nanocrystals well-scattered on the surface of nano-Mg(OH)2. A strategy of inducing fast crystal growth of nano-Mg(OH)2 to micrometer-sized Na2Mg(CO3)2 enables the desorption and enrichment of uranyl. The recycling and reuse of nano-Mg(OH)2 can be achieved simultaneously. The finding in this work provides fundamental understanding of the efficient usage of nano-Mg(OH)2 in practical applications. PMID:24369706

  2. Four-coordinate cobalt pincer complexes: electronic structure studies and ligand modification by homolytic and heterolytic pathways.

    PubMed

    Semproni, Scott P; Milsmann, Carsten; Chirik, Paul J

    2014-06-25

    A family of cobalt chloride, methyl, acetylide and hydride complexes bearing both intact and modified tert-butyl substituted bis(phosphino)pyridine pincer ligands has been synthesized and structurally characterized and their electronic structures evaluated. Treatment of the unmodified compounds with the stable nitroxyl radical, TEMPO (2,2,6,6-tetramethylpiperidin-1-yloxidanyl) resulted in immediate H- atom abstraction from the benzylic position of the chelate yielding the corresponding modified pincer complexes, ((tBu)mPNP)CoX (X = H, CH3, Cl, CCPh). Thermolysis of the methyl and hydride derivatives, ((tBu)PNP)CoCH3 and ((tBu)PNP)CoH, at 110 C also resulted in pincer modification by H atom loss while the chloride and acetylide derivatives proved inert. The relative ordering of benzylic C-H bond strengths was corroborated by H atom exchange experiments between appropriate intact and modified pincer complexes. The electronic structures of the modified compounds, ((tBu)mPNP)CoX were established by EPR spectroscopy and DFT computations and are best described as low spin Co(II) complexes with no evidence for ligand centered radicals. The electronic structures of the intact complexes, ((tBu)PNP)CoX were studied computationally and bond dissociation free energies of the benzylic C-H bonds were correlated to the identity of the X-type ligand on cobalt where pure ? donors such as hydride and methyl produce the weakest C-H bonds. Comparison to a rhodium congener highlights the impact of the energetically accessible one-electron redox couple of the first row metal ion in generating weak C-H bonds in remote positions of the supporting pincer ligand. PMID:24897302

  3. Molecular structures and magnetic resonance spectroscopic investigations of highly distorted six-coordinate low-spin iron(III) porphyrinate complexes.

    PubMed

    Ogura, H; Yatsunyk, L; Medforth, C J; Smith, K M; Barkigia, K M; Renner, M W; Melamed, D; Walker, F A

    2001-07-11

    Three bis-axially ligated complexes of iron(III) octaethyltetraphenylporphyrin, (OETPP)Fe(III), have been prepared, which are low-spin complexes, each with two axial nitrogen-donor ligands (N-methylimidazole (N-MeIm), 4-(dimethylamino)pyridine (4-NMe(2)Py), and 2-methylimidazole (2-MeImH)). The crystal and molecular structure of the bis-(2-MeImH) complex shows the macrocycle to be in a saddled conformation, with the ligands in perpendicular planes aligned at 14 degrees to the porphyrin nitrogens so as to relieve the steric interaction between the 2-methyl groups and the porphyrin. The Fe-N(por) bond lengths are typical of nonplanar six-coordinate low-spin Fe(III) complexes, while the axial Fe-N(ax) bond lengths are substantially longer than those of [(TPP)Fe(2-MeImH)(2)](+) (2.09(2) A as compared to 2.015(4) and 2.010(4) A). The crystal and molecular structure of the bis-(4-NMe(2)Py) complex also shows the macrocycle to be in a mainly saddled conformation, but with a significant ruffled component. As a result, the average Fe-N(por) bonds are significantly shorter (1.951 A as compared to 1.974 A) than those of the bis-(2-MeImH) complex. One ligand is aligned at 9 degrees to two trans porphyrin nitrogens, while the other is at 79 degrees to the same porphyrin nitrogens, producing a dihedral angle of 70 degrees between the ligand planes. The EPR spectrum of this complex, like that of the bis-(2-MeImH) complex, is of the "large g(max)" type, with g(max) = 3.29 and 3.26, respectively. However, in frozen CD(2)Cl(2), [(OETPP)Fe(N-MeIm)(2)](+) exhibits both "large g(max)" and normal rhombic signals, suggesting the presence of both "perpendicular" and "parallel" ligand orientations. The 1- and 2D (1)H NMR spectra of each of these complexes, as well as the chloroiron(III) starting material, were investigated as a function of temperature. The COSY and NOESY/EXSY spectra of the chloride complex are consistent with the expected J-coupling and saddle inversion dynamics, respectively. Complete spectral assignments for the bis-(N-MeIm) and -(4-NMe(2)Py) complexes have been made using 2D (1)H NMR techniques. In each case, the number of resonances due to methylene (two) and phenyl protons (one each) is consistent with D(2)(d)() symmetry, and therefore an effective perpendicular orientation of the axial ligands on the time scale of the NMR experiments. The temperature dependences of the (1)H resonances of these complexes show significant deviations from Curie behavior, and also evidence of extensive ligand exchange and rotation. Spectral assignment of the eight methylene resonances of the bis-(2-MeImH) complex to the four ethyl groups was possible through the use of 2D (1)H NMR techniques. The complex is fluxional, even at -90 degrees C, and ROESY data suggest that the predominant process is saddle inversion accompanied by simultaneous rotation of the axial ligands. Saddle inversion becomes slow on the 2D NMR time scale as the temperature is lowered in the ligand order of N-MeIm > 4-NMe(2)Py > 2-MeImH, probably due mainly to progressive destabilization of the ground state rather than progressive stabilization of the transition state of the increasingly "hindered" bis-ligand complexes. PMID:11439043

  4. Designed single-step synthesis, structure, and derivative textural properties of well-ordered layered penta-coordinate silicon alcoholate complexes.

    PubMed

    Li, Xiansen; Michaelis, Vladimir K; Ong, Ta-Chung; Smith, Stacey J; Griffin, Robert G; Wang, Evelyn N

    2014-05-19

    The controllable synthesis of well-ordered layered materials with specific nanoarchitecture poses a grand challenge in materials chemistry. Here the solvothermal synthesis of two structurally analogous 5-coordinate organosilicate complexes through a novel transesterification mechanism is reported. Since the polycrystalline nature of the intrinsic hypervalent Si complex thwarts the endeavor in determining its structure, a novel strategy concerning the elegant addition of a small fraction of B species as an effective crystal growth mediator and a sacrificial agent is proposed to directly prepare diffraction-quality single crystals without disrupting the intrinsic elemental type. In the determined crystal structure, two monomeric primary building units (PBUs) self-assemble into a dimeric asymmetric secondary BU via strong Na(+)-O(2-) ionic bonds. The designed one-pot synthesis is straightforward, robust, and efficient, leading to a well-ordered (10?)-parallel layered Si complex with its principal interlayers intercalated with extensive van der Waals gaps in spite of the presence of substantial Na(+) counter-ions as a result of unique atomic arrangement in its structure. However, upon fast pyrolysis, followed by acid leaching, both complexes are converted into two SiO2 composites bearing BET surface areas of 163.3 and 254.7?m(2) ?g(-1) for the pyrolyzed intrinsic and B-assisted Si complexes, respectively. The transesterification methodology merely involving alcoholysis but without any hydrolysis side reaction is designed to have generalized applicability for use in synthesizing new layered metal-organic compounds with tailored PBUs and corresponding metal oxide particles with hierarchical porosity. PMID:24737615

  5. Designed Single-Step Synthesis, Structure, and Derivative Textural Properties of Well-Ordered Layered Penta-Coordinate Silicon Alcoholate Complexes

    PubMed Central

    Li, Xiansen; Michaelis, Vladimir K.; Ong, Ta-Chung; Smith, Stacey J.; Griffin, Robert G.; Wang, Evelyn N.

    2014-01-01

    The controllable synthesis of well-ordered layered materials with specific nanoarchitecture poses a grand challenge in materials chemistry. We report the solvothermal synthesis of two structurally analogous 5-coordinate organosilicate complexes via a novel transesterification mechanism. Since the polycrystalline nature of the intrinsic hypervalent Si complex thwarts the endeavor in determining its structure, a novel strategy concerning the elegant addition of a small fraction of B species as an effective crystal growth mediator and a sacrificial agent is proposed to directly prepare diffraction-quality single crystals without disrupting the intrinsic elemental type. In the determined crystal structure, two monomeric primary building units (PBUs) self-assemble into a dimeric asymmetric secondary BU via strong Na+-O2? ionic bonds. The designed one-pot synthesis is straightforward, robust, and efficient, leading to a well-ordered (10?)-parallel layered Si complex with its principal interlayers intercalated with extensive van der Waals gaps in spite of the presence of substantial Na+ counterions as a result of unique atomic arrangement in its structure. On the other hand, upon fast pyrolysis, followed by acid leaching, both complexes are converted into two SiO2 composites bearing BET surface areas of 163.3 and 254.7 m2 g?1 for the pyrolyzed intrinsic and B-assisted Si complexes, respectively. The transesterification methodology merely involving alcoholysis but without any hydrolysis side reaction is designed to have generalized applicability for use in synthesizing new layered metal-organic compounds with tailored PBUs and corresponding metal oxide particles with hierarchical porosity. PMID:24737615

  6. High ethene/ethane selectivity in 2,2'-bipyridine-based silver(i) complexes by removal of coordinated solvent.

    PubMed

    Cowan, Matthew G; McDanel, William M; Funke, Hans H; Kohno, Yuki; Gin, Douglas L; Noble, Richard D

    2015-05-01

    Following removal of coordinated CH3 CN, the resulting complexes [Ag(I) (2,2'-bipyridine)][BF4 ] (1) and [Ag(I) (6,6'-dimethyl-2,2'-bipyridine)][OTf] (2) show ethene/ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18?mmol?g(-1) when tested at an applied gas pressure of 90?kPa and a temperature of (201)?C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2, ethene sorption reached 90?% of equilibrium capacity within 15?minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes. PMID:25765760

  7. Acetamide Coordination in a Nickel(I) Macrocyclic Complex: Synthesis, Properties, and X-ray Crystal Structure

    E-print Network

    Paik Suh, Myunghyun

    , has been prepared by the reduction of Ni(II) complex (R,R,S,S)-[Ni(L)]- (ClO4)2,1/2H2O with Na(Hg, is a prosthetic group of S-methyl coenzyme M reductase which catalyzes the reductive cleavage of S-methyl coenzyme bacteria.11-14 An EPR signal detected with Methanobacterium thermoautotrophi- cum was attributed to a Ni

  8. Mechanistic Insight into N=N Cleavage by a Low-Coordinate Iron(II) Hydride Complex

    PubMed Central

    Sadique, Azwana R.; Gregory, Elizabeth A.; Brennessel, William W.

    2008-01-01

    The reaction pathways of high-spin iron hydride complexes are relevant to the mechanism of N2 reduction by nitrogenase, which has been postulated to involve paramagnetic iron-hydride species. However, almost all known iron hydrides are low-spin, diamagnetic Fe(II) compounds. We have demonstrated that the first high-spin iron hydride complex, LtBuFeH (LtBu = bulky ?-diketiminate), reacts with PhN=NPh to completely cleave the N-N double bond, giving LtBuFeNHPh. Here, we disclose a series of experiments that elucidate the mechanism of this reaction. Crossover and kinetic experiments rule out common non-radical mechanisms, and support a radical chain mechanism mediated by iron(I) species including a rare ?2-azobenzene complex. Therefore, this high-spin iron(II) hydride can perform [1,2]-insertion through both non-radical and radical insertion mechanisms, a special feature that enables novel reactivity. PMID:17564444

  9. Chemical, mass spectrometric, spectrochemical, nuclear, and radiochemical analysis of nuclear-grade uranyl nitrate solutions

    SciTech Connect

    Not Available

    1981-01-01

    The standard covers analytical procedures to determine compliance of nuclear-grade uranyl nitrate solution to specifications. The following methods are described in detail: uranium by ferrous sulfate reduction-potassium dichromate titrimetry and by ignition gravimetry; specific gravity by pycnometry; free acid by oxalate complexation; thorium by the Arsenazo(III) (photometric) method; chromium by the diphenylcarbazide (photometric) method; molybdenum by the thiocyanate (photometric) method; halogens separation by steam distillation; fluorine by specific ion electrode; halogen distillate analysis: chloride, bromide and iodide by amperometric microtitrimetry; bromine by the fluorescein (photometric) method; sulfate sulfur by (photometric) turbidimetry; phosphorus by the molybdenum blue (photometric) method; silicon by the molybdenum blue (photometric) method; carbon by persulfate oxidation-acid titrimetry; nonvolatile impurities by spectrography; volatile impurities by rotating-disk spark spectrography; boron by emission spectrography; impurity elements by spark source mass spectrography; isotopic composition by multiple filament surface-ionization mass spectrometry; uranium-232 by alpha spectrometry; total alpha activity by direct alpha counting; fission product activity by beta and gamma counting; entrained organic matter by infrared spectrophotometry. (JMT)

  10. Calix[4]bis(thiacrown): assembly of an endocyclic disilver(I) complex and exocyclic 3D copper(I) coordination polymers.

    PubMed

    Lee, Jai Young; Lee, So Young; Seo, Joobeom; Park, Chul Soon; Go, Jung Nam; Sim, Wonbo; Lee, Shim Sung

    2007-08-01

    Calix[4]bis(thiacrown-5) (L) with 1,3-alternating conformation was employed as a strong dinucleating ligand for the soft metal ions AgI and CuI. The reaction of L with AgPF6 afforded a discrete endo-coordinated disilver(I) complex 1, [Ag2L](PF6)2. In contrast, mixed products (2a + 2b) consisting of 3D networks were obtained from the reaction of L and CuI; 2b linked with a Cu4I4 cubane unit was shown to generate photoluminescence, while 2a linked with a Cu2I2 rhomboid unit does not. PMID:17630685

  11. coordinate plane

    NSDL National Science Digital Library

    olsen

    2010-10-07

    Become familiar with the coordinate plane. Learn the quadrants and how to graph points and read points on a coordinate plane. You are required to do the assignment and take the quiz. The other resources are to help prepare you for the quiz and book assignment. This is a quick review of the lesson.The Coordinate Plane This is a game to practice plotting and reading points.coordinates game *Assignment: Watch Powerpoint 3.3 and fill in your ...

  12. Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces

    USGS Publications Warehouse

    Arai, Yuji; Fuller, C.C.

    2012-01-01

    Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na2SO4 solutions to simulate the major chemical composition of U-contaminatedgroundwater (i.e., [SO42-]~13 mM L-1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO2-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydritewater interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.557.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO2, there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO2 fluctuates between 1 and 2 pCO2%.

  13. Crystal structure, physical and photophysical properties of a platinum(II) complex coordinated to the biphenyl dianion and cyclooctadiene

    SciTech Connect

    Chen, Y.; Perkovic, M.W.; Rillema, D.P. [Wichita State Univ., KS (United States)] [and others

    1996-08-01

    The complex, Pt(bph)(COD), where bph is the biphenyl dianion and COD is 1,5-cyclooctadiene, crystallizes in the orthorhombic space group Pbca with a = 12.178(4) {Angstrom}, b = 9.693(3) {Angstrom} and c = 25.344(9) {Angstrom} and Z = 8. The Pt-C distances to the olefinic carbon atoms that result from the {pi} electron donation of the COD ligand are in the range 2.20(3)-2.27(3) {Angstrom} and the Pt-C distances to the {sigma} bonded bph ligand are shorter at 2.01(3)-2.03(2) {Angstrom}. The lowest energy absorption of the complex is at 383 nm ({epsilon}=1.2 x 10{sup 3}). The emission spectrum is structured in fluid solution at room temperature with the emission energy maximum at 537 nm, {phi}{sub em} = 1.68 x 10{sup {minus}3}, and {tau} = 1.93 {mu}s. Temperature dependent emission lifetime measurements result in a k{sub o} value of 2.69 x 10{sup 4}, a preexponential factor of 2.47 x 10{sup 6} and a {delta}E{sub 1} value of 324 cm{sup {minus}1}.

  14. Measurement of extreme hyperfine fields in two-coordinate high-spin Fe2+ complexes by Mssbauer spectroscopy: essentially free-ion magnetism in the solid state.

    PubMed

    Bryan, Aimee M; Lin, Chun-Yi; Sorai, Michio; Miyazaki, Yuji; Hoyt, Helen M; Hablutzel, Annelise; LaPointe, Anne; Reiff, William M; Power, Philip P; Schulz, Charles E

    2014-11-17

    Mssbauer studies of three two-coordinate linear high-spin Fe(2+) compounds, namely, Fe{N(SiMe3)(Dipp)}2 (1) (Dipp = C6H3-2,6-(i)Pr2), Fe(OAr')2 (2) [Ar' = C6H3-2,6-(C6H3-2,6-(i)Pr2)2], and Fe{C(SiMe3)3}2 (3), are presented. The complexes were characterized by zero- and applied-field Mssbauer spectroscopy (1-3), as well as zero- and applied-field heat-capacity measurements (3). As 1-3 are rigorously linear, the distortion(s) that might normally be expected in view of the Jahn-Teller theorem need not necessarily apply. We find that the resulting very large unquenched orbital angular momentum leads to what we believe to be the largest observed internal magnetic field to date in a high-spin iron(II) compound, specifically +162 T in 1. The latter field is strongly polarized along the directions of the external field for both longitudinal and transverse field applications. For the longitudinal case, the applied field increases the overall hyperfine splitting consistent with a dominant orbital contribution to the effective internal field. By contrast, 2 has an internal field that is not as strongly polarized along a longitudinally applied field and is smaller in magnitude at ca. 116 T. Complex 3 behaves similarly to complex 1. They are sufficiently self-dilute (e.g., FeFe distances of ca. 9-10 ) to exhibit varying degrees of slow paramagnetic relaxation in zero field for the neat solid form. In the absence of EPR signals for 1-3, we show that heat-capacity measurements for one of the complexes (3) establish a geff value near 12, in agreement with the principal component of the ligand electric field gradient being coincident with the z axis. PMID:25368962

  15. Two Pathways for Electrocatalytic Oxidation of Hydrogen by a Nickel Bis(diphosphine) Complex with Pendant Amines in the Second Coordination Sphere

    SciTech Connect

    Yang, Jenny Y.; Smith, Stuart E.; Liu, Tianbiao L.; Dougherty, William G.; Hoffert, Wesley A.; Kassel, W. S.; Rakowski DuBois, Mary; DuBois, Daniel L.; Bullock, R. Morris

    2013-07-03

    A nickel bis(diphosphine) complex containing pendant amines in the second coordination sphere, [Ni(PCy2Nt-Bu2)2](BF4)2 (PCy2Nt-Bu2 = 1,5-di(tert-butyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. Under 1.0 atm H2 using NEt3 as a base and with added water, a turnover frequency of 45 s-1 is observed at 23 C; this is the fastest observed for a molecular catalyst. The addition of hydrogen to the NiII complex gives thee isomers of the doubly protonated Ni0 complex [Ni(PCy2HNt-Bu2)2](BF4)2; these complexes have been studied by 1H and 31P NMR spectroscopy, and for one isomer, an X-ray diffraction study. Using the pKa values and NiII/I and NiI/0 redox potentials in a thermochemical cycle, the free energy of hydrogen addition to [Ni(PCy2Nt-Bu2)2]2+ was determined to be -7.9 kcal mol-1. The catalytic rate observed in dry acetonitrile for the oxidation of H2 at the NiII/I couple depends on base size, with larger bases (NEt3, tert-BuNH2) resulting in slower catalysis than n-BuNH2. Addition of water accelerates the rate of catalysis, especially for the larger bases. The results of these studies provide important insights into the design of catalysts for hydrogen oxidation that facilitate proton movement and operate at moderate potentials. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  16. Coordination and Processing of DNA Ends During Double-Strand Break Repair: The Role of the Bacteriophage T4 Mre11/Rad50 (MR) Complex

    PubMed Central

    Almond, Joshua R.; Stohr, Bradley A.; Panigrahi, Anil K.; Albrecht, Dustin W.; Nelson, Scott W.; Kreuzer, Kenneth N.

    2013-01-01

    The in vivo functions of the bacteriophage T4 Mre11/Rad50 (MR) complex (gp46/47) in double-strand-end processing, double-strand break repair, and recombination-dependent replication were investigated. The complex is essential for T4 growth, but we wanted to investigate the in vivo function during productive infections. We therefore generated a suppressed triple amber mutant in the Rad50 subunit to substantially reduce the level of complex and thereby reduce phage growth. Growth-limiting amounts of the complex caused a concordant decrease in phage genomic recombination-dependent replication. However, the efficiencies of double-strand break repair and of plasmid-based recombination-dependent replication remained relatively normal. Genetic analyses of linked markers indicated that double-strand ends were less protected from nuclease erosion in the depleted infection and also that end coordination during repair was compromised. We discuss models for why phage genomic recombination-dependent replication is more dependent on Mre11/Rad50 levels when compared to plasmid recombination-dependent replication. We also tested the importance of the conserved histidine residue in nuclease motif I of the T4 Mre11 protein. Substitution with multiple different amino acids (including serine) failed to support phage growth, completely blocked plasmid recombination-dependent replication, and led to the stabilization of double-strand ends. We also constructed and expressed an Mre11 mutant protein with the conserved histidine changed to serine. The mutant protein was found to be completely defective for nuclease activities, but retained the ability to bind the Rad50 subunit and double-stranded DNA. These results indicate that the nuclease activity of Mre11 is critical for phage growth and recombination-dependent replication during T4 infections. PMID:23979587

  17. Hydrothermal Synthesis and Structural Characterization of Organically Templated Uranyl Diphosphonates

    SciTech Connect

    Adelani, Pius O.; Oliver, A. G.; Albrecht-Schmitt, Thomas E.

    2011-01-01

    The hydrothermal treatment of uranyl nitrate and 1,4-benzenebisphosphonic acid with a variety of aliphatic amines (tetramethylammonium hydroxide, tetraethylammonium hydroxide, and diethyldimethylammonium hydroxide) and small quantities of hydrofluoric acid at 200 C results in the crystallization of a series of layered uranyl diphosphonate compounds, [(CH{sub 3}){sub 4}N][(UO{sub 2}){sub 3}(O{sub 3}PC{sub 6}H{sub 4}PO{sub 3}H){sub 2}F(H{sub 2}O)]0.5H{sub 2}O (Me{sub 4}Ubbp), [(CH{sub 3}CH{sub 2}){sub 4}N]{(UO{sub 2})[C{sub 6}H{sub 4}(PO{sub 3}H)(PO{sub 3}H{sub 1.5})]{sub 2}(H{sub 2}O)} (Et{sub 4}Ubbp), and [(CH{sub 3}CH{sub 2}){sub 2}N(CH{sub 3}){sub 2}][(UO{sub 2}){sub 3}(O{sub 3}PC{sub 6}H{sub 4}PO{sub 3}H){sub 2}F(H{sub 2}O)] (Et{sub 2}Me{sub 2}Ubbp). All these new compounds have layered structures, but the structures of Me{sub 4}Ubbp and Et{sub 2}Me{sub 2}Ubbp are similar in that they both contain UO{sub 6}F and UO{sub 7} pentagonal bipyramids within dimers that are bridged by the phosphonate into a three-dimensional structure. The structure of Et{sub 4}Ubbp contains a single crystallographically unique UO{sub 7} unit. The edge-sharing pentagonal bipyramids are linked into chains formulated as {(UO{sub 2})[C{sub 6}H{sub 4}(PO{sub 3}H)(PO{sub 3}H{sub 1.5})]{sub 2}(H{sub 2}O)}{sup 1?}. The voids in these structures are filled with the organic templates so that the overall charge balance is maintained. Intense fluorescence was observed from these compounds at room temperature.

  18. Tuning the silver(I) complexes of 3-(2-pyridyl)pyrazole-based ligands: Syntheses and crystal structures of the complexes, as well as theoretical investigations on the coordination abilities of the ligands

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Sen; Li, Jian-Rong; Zou, Ru-Qiang; Zhou, Jiang-Ning; Shi, Xue-Song; Wang, Jun-Jie; Bu, Xian-He

    2007-10-01

    In our efforts to investigate the influences of different pendant aromatic groups and the spatial position of N donors in 3-(2-pyridyl)pyrazole-based ligands on the structures of their metal complexes, five structurally related ligands: 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]benzene ( L1), 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]naphthalene ( L2), 8-[3-(2-pyridyl)pyrazol-1-ylmethyl]quinoline ( L3), 3-[3-(2-pyridyl)pyrazol-1-ylmethyl]pyridine ( L4) and 4-[3-(2- pyridyl)pyrazol-1-ylmethyl]pyridine ( L5), have been used to react with AgClO 4 to form five Ag(I) complexes, [Ag( L1) 2](ClO 4) ( 1), [Ag( L2) 2](ClO 4) ( 2), [Ag( L3)(H L3)](ClO 4) 2(CH 3CN) ( 3), {[Ag( L4)](ClO 4)} 2 ( 4), and {[Ag( L5)](ClO 4)} ? ( 5). The structural differences of these complexes may be attributed to the coordination geometries or N donor position of the pendant aromatic groups in ligands L1- L5. Also, the result reveals that various intra- and/or inter-molecular weak interactions, such as ?⋯? stacking, C-H⋯? and C-H⋯O H-bonding interactions, play important roles in the formation of 1- 5, especially in the aspect of linking the multi-nuclear discrete subunits or low-dimensional entities into high-dimensional frameworks. Moreover, the coordination behaviors of ligands L1- L5 have been briefly evaluated by DFT calculations.

  19. PI(3)P-bound UVRAG coordinates Golgi-ER retrograde and Atg9 transport by differential interactions with the ER tether and the Beclin1 complex

    PubMed Central

    Lee, Joo-Hyung; Zhang, Tian; Ghozalli, Irene; Pirooz, Sara Dolatshahi; Zhao, Zhen; Bharatham, Nagakumar; Li, Baihong; Oh, Soohwan; Lee, Wen-Hwa; Takahashi, Yoshinori; Wang, Hong-Gang; Minassian, Arlet; Feng, Pinghui; Deretic, Vojo; Pepperkok, Rainer; Tagaya, Mitsuo; Yoon, Ho Sup; Liang, Chengyu

    2013-01-01

    ER-Golgi membrane transport and autophagy are intersecting trafficking pathways that are tightly regulated and crucial for homeostasis, development and diseases. Here, we identify UVRAG, a Beclin1-binding autophagic factor, as a PI(3)P-binding protein that depends on PI(3)P for its ER localization. We further show that UVRAG interacts with RINT-1, and acts as an integral component of the RINT-1-containing ER tethering complex, which couples phosphoinositide metabolism to COPI-vesicle tethering. Displacement or knockdown of UVRAG profoundly disrupted COPI cargo transfer to the ER and Golgi integrity. Intriguingly, autophagy caused the dissociation of UVRAG from the ER tether, which in turn worked in concert with the Bif-1-Beclin-PI(3)KC3 complex to mobilize Atg9 translocation for autophagosome formation. These findings identify a regulatory mechanism that coordinates Golgi-ER retrograde and autophagy-related vesicular trafficking events through physical and functional interactions between UVRAG, phosphoinositide, and their regulatory factors, thereby ensuring spatiotemporal fidelity of membrane trafficking and maintenance of organelle homeostasis. PMID:24056303

  20. Enantioseparation of dansyl amino acids and dipeptides by chiral ligand exchange capillary electrophoresis based on Zn(II)-L-hydroxyproline complexes coordinating with ?-cyclodextrins.

    PubMed

    Mu, Xiaoyu; Qi, Li; Qiao, Juan; Yang, Xinzheng; Ma, Huimin

    2014-10-10

    A chiral ligand exchange capillary electrophoresis (CLE-CE) method using Zn(II) as the central ion and L-4-hydroxyproline as the chiral ligand coordinating with ?-cyclodextrin (?-CD) was developed for the enantioseparation of amino acids (AAs) and dipeptides. The effects of various separation parameters, including the pH of the running buffer, the ratio of Zn(II) to L-4-hydroxyproline, the concentration of complexes and cyclodextrins (CDs) were systematically investigated. After optimization, it has been found that eight pairs of labeled AAs and six pairs of labeled dipeptides could be baseline-separated with a running electrolyte of 100.0mM boric acid, 5.0mM ammonium acetate, 3.0mM Zn(II), 6.0mM L-hydroxyproline and 4.0mM ?-CD at pH 8.2. The quantitation of AAs and dipeptides was conducted and good linearity (r(2)?0.997) and favorable repeatability (RSD?3.6%) were obtained. Furthermore, the proposed method was applied in determining the enantiomeric purity of AAs and dipeptides. Meanwhile, the possible enantiorecognition mechanism based on the synergistic effect of chiral metal complexes and ?-CD was explored and discussed briefly. PMID:25220143

  1. Coordination of 2,2'-bipyridyl and 1,10-phenanthroline to yttrium and lanthanum complexes based on a scorpionate ligand.

    PubMed

    Roitershtein, Dmitrii; Domingos, Angela; Pereira, Laura C J; Ascenso, Jos R; Marques, Nomia

    2003-11-17

    Reaction of yttrium and lanthanum trichloride with 1 equiv of sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate and 1 equiv of 2,2'-bipyridine gives good yields of the complexes [MCl(2)(Tp(Me2))(C(10)H(8)N(2))] (M = Y (1), La (2)). The analogous compounds with 1,10-phenanthroline, [MCl(2)(Tp(Me2))(C(12)H(8)N(2))] (M = Y (3), La (4)), have been obtained by a similar procedure. The solid-state structures of 2-4 were determined by single-crystal X-ray diffraction and revealed that the compounds are all seven-coordinate with capped octahedral geometry. In contrast, reaction of yttrium trichloride with 1 equiv of sodium hydrotris(3,5-dimethylpyrazolyl)borate in the presence of 1 equiv of neocuproine affords [YCl(3)(Tp(Me2))][Na(neoc)(3))] (5). Compounds 1 and 2 provide an entry for the synthesis of complexes containing the bipyridyl ligand in a radical anionic form or in a dianionic form. Reaction of 1 and 2 with an excess of sodium amalgam gives [Y(Tp(Me2))(bipy)(THF)(2)] (6) and [La(Tp(Me2))(2)(bipy)] (7), respectively. The structures of both compounds have been determined by X-ray crystallography. Compound 7 can be oxidized with iodine to give [La(Tp(Me2))(2)(bipy)]I (8). PMID:14606865

  2. Co(II), Ni(II), Cu(II) and Zn(II) complexes of a bipyridine bis-phenol conjugate: generation and properties of coordinated radical species.

    PubMed

    Arora, Himanshu; Philouze, Christian; Jarjayes, Olivier; Thomas, Fabrice

    2010-11-14

    Four bis-phenolate complexes [Zn(II)L], [Ni(II)L], [Cu(II)L] and [Co(II)L] (where [H(2)L = 2,2'-[2,2']bipyridinyl-6-yl-bis-4,6-di-tert-butylphenol] have been synthesized. The copper(II) and nickel(II) complexes have been characterized by X-ray diffraction, showing a metal ion within a square planar geometry, slightly distorted towards tetrahedral. The cyclic voltametry (CV) curve of [Zn(II)L] consists of a single bi-electronic reversible wave at 0.06 V vs. Fc/Fc(+). The electrochemically generated dication is a diradical species [Zn(II)L??](2+) that exhibits the typical phenoxyl ?-?* band at 395 nm. It is EPR-silent due to magnetic interactions between the phenoxyl moieties. The CV curves of [Ni(II)L] and [Cu(II)L] exhibit two distinct ligand-centred one-electron oxidation waves. The first one is observed at E(1/2)(1) = 0.38 and 0.40 V for the nickel and copper complex, respectively, and corresponds to the formation of M(II)-coordinated phenoxyl radicals. Accordingly, [Ni(II)L?](+) exhibits a strong absorption band at 960 nm and an (S = ) EPR signal centred at g(iso) = 2.02. [Cu(II)L?](+) is EPR-silent, in agreement with a magnetic coupling between the metal and the radical spin. In contrast with the other complexes, [Co(II)L] was found to react with dioxygen (mostly in the presence of pyridine), giving rise to a stable (S = ) superoxo radical complex [Co(III)L(Py)(O(2)?)]. One-electron oxidation of [Co(II)L] at -0.01 V affords a diamagnetic cobalt(III) complex [Co(III)L](+) that is inert towards O(2) binding, whereas two-electron oxidation leads to the paramagnetic phenoxyl radical species [Co(III)L?](+) whose EPR spectrum features an (S = ) signal at g(iso) = 2.00. PMID:20820605

  3. Synthesis, structure, spectra and reactivity of iron(III) complexes of facially coordinating and sterically hindering 3N ligands as models for catechol dioxygenases.

    PubMed

    Sundaravel, Karuppasamy; Dhanalakshmi, Thirumanasekaran; Suresh, Eringathodi; Palaniandavar, Mallayan

    2008-12-28

    A series of 1 : 1 iron(III) complexes of sterically hindered and systematically modified tridentate 3N donor ligands have been isolated and studied as functional models for extradiol-cleaving catechol dioxygenases. All of them are of the type [Fe(L)Cl(3)], where L is N-methyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L1), N-ethyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L2), N-benzyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L3), N,N-dimethyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L4), N'-methyl-N'-(pyrid-2-ylmethyl)-N,N-dimethylethylenediamine (L5), N'-ethyl-N'-(pyrid-2-ylmethyl)-N,N-dimethylethylenediamine (L6) and N'-benzyl-N'-(pyrid-2-ylmethyl)-N,N-dimethylethylenediamine (L7). They have been characterized by elemental analysis and spectral and electrochemical methods. The X-ray crystal structures of the complexes [Fe(L2)Cl(3)] 2, [Fe(L3)Cl(3)] 3 and [Fe(L7)Cl(3)] 7 have been successfully determined. All the three complexes possess a distorted octahedral coordination geometry in which the ligand is facially coordinated to iron(III) and the chloride ions occupy the remaining coordination sites. Upon replacing the N-ethyl group on the terminal nitrogen donor in 2 by the bulky N-benzyl group as in 3, the terminal Fe-N bond distance increases slightly from 2.229(5) A to 2.244(5) A. Upon incorporating the sterically demanding N-benzyl group on the central nitrogen donor in 4 to obtain 7, the central Fe-N(amine) bond distance increases from 2.181(5) A to 2.299(2) A. The catecholate adducts [Fe(L)(DBC)(Cl)] and [Fe(L)(DBC)(Sol)](+), where H(2)DBC is 3,5-di-tert-butylcatechol and Sol = solvent (H(2)O/DMF), have been generated in situ and their spectral and redox properties and dioxygenase activities have been studied in N,N-dimethylformamide and dichloromethane solutions. The adducts [Fe(L)(DBC)(Sol)](+) undergo cleavage of DBC(2-) in the presence of molecular oxygen to afford both intra- and extradiol cleavage products. The extradiol products are higher in dichloromethane than in DMF solution and the extradiol to intradiol product selectivity (E/I, 7.2 : 1-18.5 : 1) observed decreases upon increasing the steric bulk of N-alkyl substituent on the terminal nitrogen atom and upon incorporating an N-alkyl substituent on the central nitrogen atom. The plot of log(k(O(2))) vs. energy of the low energy catecholate-iron(III) LMCT band is linear, which is consistent with the proposal that the LMCT band energy corresponds to the energy needed for a spin-inversion process at the iron center upon dioxygen attack. Also, the rate of oxygenation is dictated by the solvent as well as the Lewis acidity of the iron(III) center, as shown by the linear plot of log(k(O(2))) vs.E(1/2) of the Fe(III)/Fe(II) redox potentials of the [Fe(L)(Sol)(3)](3+) complexes. PMID:19050788

  4. Coordinated Destruction of Cellular Messages in Translation Complexes by the Gammaherpesvirus Host Shutoff Factor and the Mammalian Exonuclease Xrn1

    PubMed Central

    Kumar, G. Renuka; Wong, Wesley; Jackson, Andrew O.; Glaunsinger, Britt A.

    2011-01-01

    Several viruses encode factors that promote host mRNA degradation to silence gene expression. It is unclear, however, whether cellular mRNA turnover pathways are engaged to assist in this process. In Kaposi's sarcoma-associated herpesvirus this phenotype is enacted by the host shutoff factor SOX. Here we show that SOX-induced mRNA turnover is a two-step process, in which mRNAs are first cleaved internally by SOX itself then degraded by the cellular exonuclease Xrn1. SOX therefore bypasses the regulatory steps of deadenylation and decapping normally required for Xrn1 activation. SOX is likely recruited to translating mRNAs, as it cosediments with translation initiation complexes and depletes polysomes. Cleaved mRNA intermediates accumulate in the 40S fraction, indicating that recognition occurs at an early stage of translation. This is the first example of a viral protein commandeering cellular mRNA turnover pathways to destroy host mRNAs, and suggests that Xrn1 is poised to deplete messages undergoing translation in mammalian cells. PMID:22046136

  5. Tritium gettering from air with hydrogen uranyl phosphate

    SciTech Connect

    Souers, P.C.; Uribe, F.S.; Stevens, C.G.; Tsugawa, T.T.

    1985-08-01

    The managers of all tritium facilities now worry about their emissions into the atmosphere. The only method for cleaning tritium out of air is to catalyze the formation of tritiated water which is adsorbed, along with the overwhelming bulk of naturally occurring water vapor, on a zeolite molecular sieve. This method generally costs several million dollars for a small system, because of the necessary steel ducting, compressors and holding tanks. We have long had the dream of finding another getter that might be cheaper to use and would, hopefully, not make tritiated water (HTO). In a previous paper, we discovered that hydrogen uranyl phosphate (HUP, with the formula HUO/sub 2/PO/sub 4/ x 4H/sub 2/O) getters 1 ppM of tritium gas out of moist air. This makes HUP the first known ''direct'' tritium getter to work in air. However, the tritium enters a hydroxyl network within the HUP, so that it is effectively still in ''water'' form within the HUP. Worse yet, we found up to 10% tritiated water formed during the previous gettering experiments. HUP is unusual in possessing the exceptionally low vapor pressure of 0.6 torr water vapor at 298/sup 0/K. This allows HUP to be used in fairly dry environments. 14 refs., 3 figs., 2 tabs.

  6. Renal Toxicogenomic Response to Chronic Uranyl Nitrate Insult in Mice

    PubMed Central

    Taulan, Magali; Paquet, Franois; Maubert, Christophe; Delissen, Olivia; Demaille, Jacques; Romey, Marie-Catherine

    2004-01-01

    Although the nephrotoxicity of uranium has been established through numerous animal studies, relatively little is known about the effects of long-term environmental uranium exposure. Using a combination of conventional biochemical studies and serial analysis of gene expression (SAGE), we examined the renal responses to uranyl nitrate (UN) chronic exposure. Renal uranium levels were significantly increased 4 months after ingestion of uranium in drinking water. Creatinine levels in serum were slightly but significantly increased compared with those in controls. Although no further significant differences in other parameters were noted, substantial molecular changes were observed in toxicogenomic profiles. UN induced dramatic alterations in expression levels of more than 200 genes, mainly up-regulated, including oxidative-responserelated genes, genes encoding for cellular metabolism, ribosomal proteins, signal transduction, and solute transporters. Seven differentially expressed transcripts were confirmed by real-time quantitative polymerase chain reaction. In addition, significantly increased peroxide levels support the implication of oxidative stress in UN toxicant response. This report highlights the potential of SAGE for the discovery of novel toxicant-induced gene expression alterations. Here, we present, for the first time, a comprehensive view of renal molecular events after uranium long-term exposure. PMID:15598614

  7. Uranyl adsorption in multi-mineralic systems: Devitrified tuff and granite

    SciTech Connect

    Ong, C.G.; Leckie, J.O. [Stanford Univ., CA (United States)

    1996-10-01

    Earth materials including a devitrified tuff ({approximately}64% feldspar) and a granite ({approximately}66% feldspar) were pulverised and used in pH sorption edge batch experiments involving uranyl ion (10{sup -6} M total uranyl concentration, 1 g/L solids concentration, 0.1 M NaCl background electrolyte, 25{degrees}C, and CO{sub 2}-free using an Ar blanket). Surface treatments, intended to facilitate to various extents the dissolution of Al and Si from mineral phases, of the earth material suspensions prior to the addition of uranyl included: (1) equilibration in the electrolyte solution for a few days, (2) exposure to electrolyte solution for about a month during which the supernatant was periodically removed and replaced by fresh 0.1 M NaCl solution, and (3) equilibration in electrolyte solution without supernatant exchange in parallel with the second set. The uranyl sorption edge exhibited uptake increasingly from about pH 4 to 7, with about 50% uptake occurring at about pH 5.5. Above pH 7, uranyl desorption is observed and the rate of decline with pH is dependent on the surface treatment. Similar sorption behavior is exhibited by the single mineral albite.

  8. Uranyl photoprobing of nonbent A/T- and bent A-tracts. A difference of flexibility?

    PubMed

    Mllegaard, Niels Erik; Lindemose, Sren; Nielsen, Peter E

    2005-05-31

    In this study, we have systematically compared the uranyl photocleavage of a range of bent A-tracts and nonbent TA-tracts as well as interrupted A-tracts. We demonstrate that uranyl photocleavage of A-tracts and TA-tracts is almost identical, indicating a very similar minor groove conformation. Furthermore, a 10 base pair A-tract is divided into two independent tracts by an intervening TA or GC step. Uranyl probing also clearly distinguishes the bent A4T4 and the nonbent T4A4 sequences as adopting different structures, and our interpretation of the data is consistent with a structure for the bent A4T4 sequence that resembles a continuous A-tract, whereas the nonbent T4A4 sequences are closer to two independent and opposite A-tracts that cancel each other in terms of macroscopic bending. Finally, we also note that even single TA and TAT steps are highly sensitive to uranyl photocleavage and propose that in addition to average minor groove width, uranyl also senses DNA helix flexibility/deformability. Thus, the structural difference of TA-tracts and A-tracts may to a large extent reflect a difference in flexibility, and DNA curvature may consequently require a rigid narrow minor groove conformation that creates distinct A-tract-B-DNA junctions as the predominant cause of the bending. PMID:15909999

  9. Determination of trace uranyl ion by thermoresponsive porphyrin-terminated polymeric sensor.

    PubMed

    Shu, Xiaowen; Wang, Yingjie; Zhang, Shuang; Huang, Li; Wang, Shuao; Hua, Daoben

    2015-01-01

    Uranyl ion exists at trace levels in the environment and can cause severe adverse effects to human health. Therefore, it is desirable to develop analytical methods that can determine the trace uranyl ion in aqueous medium. We report here a new method using a thermo-responsive polymeric fluorescent sensor. Specifically, 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin terminated poly(N-isopropylacrylamide) (TCPP-PNIPAM) was synthesized by controlled free radical polymerization for the detection of uranyl ion. The maximum fluorescence intensity at ~ 658 nm of TCPP-PNIPAM increases with molecular weights and is also closely related to the temperature. The polymeric sensor is sensitive to pH (1.0 ~ 5.0) with a fast responsive time (~ 3 min). Under optimized experimental conditions, the sensor exhibits a stable response for uranyl ion with high selectivity over a concentration range from 1.0 10(-3) to 1.0 10(-7)mol/L. For the trace uranyl ion (such as 1.0 10(-8) or 10(-9)mol/L), the determination could be successfully achieved after concentrating 100 times by centrifugation above 32C. The properties enable the polymeric sensor to have great potential for environmental application. PMID:25281093

  10. Characterization and Detection of Uranyl Ion Sorption on Silver Surfaces using Surface Enhanced Raman Spectroscopy

    SciTech Connect

    Retterer, Scott T [ORNL; Wells, Sabrina M [ORNL; Sepaniak, Michael [University of Tennessee, Knoxville (UTK)

    2009-01-01

    The study of the chemical behavior of uranyl species and its rapid detection is of primary environmental and non-proliferation concern. Herein we report on a surface enhanced Raman spectroscopic study of uranyl ion (UO22+) sorption onto the thermally vapor deposited silver particle surface. The ability of vibrational spectroscopy to characterize surface phenomenon and the remarkable sensitivity of the surface enhanced Raman spectroscopy (SERS) have been introduced as an appropriate combination for the surface characterization and detection of UO22+ onto the silver surface. The appearance of symmetric stretching frequency of UO22+ around 700 cm-1 and the disappearance of the 854 cm-1 band is attributed to the development of a chemical bond between silver surface and uranyl species. The effects of temperature, solute-surface interaction time, and pH have been studied using silver modified polypropylene filter (PPF) substrates. Results show that under appropriate conditions, the concentration of uranyl ion as low as 20 ng/mL can be easily detected using the discussed SERS approach without any surface modification of silver nanoparticles. Moreover, an alteranative SERS approach of uranyl detection is demonstrated using nano-lithographically fabricated SERS substrates.

  11. Versatile coordination modes of bis[5-(2-pyridine-2-yl)-1,2,4-triazole-3-yl]alkanes in Cu(II) complexes.

    PubMed

    Gusev, Alexey N; Nemec, Ivan; Herchel, Radovan; Bayjyyev, Eziz; Nyshchimenko, Galyna A; Alexandrov, Grigory G; Eremenko, Igor L; Trvn?ek, Zden?k; Hasegawa, Miki; Linert, Wolfgang

    2014-05-21

    Nine new mononuclear and polynuclear Cu(II) complexes [Cu(H2L(2))Cl]Cl3H2O (1), [Cu(H2L(3))Cl]ClH2O (2), [Cu(H2L(4))Cl]Cl2.5H2O (3), [Cu3(?(3)-L(1))2(H2O)3](ClO4)2H2O (4), [Cu4(?-HL(1))4](ClO4)8CH3OH5H2O (5), [Cu2(HL(3))2](ClO4)22H2O (6a), [Cu2(?-HL(3))2](ClO4)2H2O (6b), [Cu2(?-HL(3))(L(3))Cu(teta)](ClO4)32H2O (7) and [Cu2(H2L(3))2(ox)](ClO4)22H2O2MeOH (8) containing [5-(2-pyridine-2-yl)-1,2,4-triazole-3-yl]alkanes (H2L(n), n = 1-4) in combination with other ligands, such as chlorido, aqua, triethylenetetramine (teta) and/or oxalato (ox(2-)), were synthesized and characterized by various techniques such as elemental analysis, FTIR, NMR and UV-Vis spectroscopy. X-ray structures of H2L(3) and H2L(4) as well as complexes 1-8 were determined. The X-ray structures revealed that relatively small composition and structural changes in the H2L(n) ligands have a substantial impact on the coordination geometries of the complexes themselves as well as on their resulting magnetic properties. It has been found that the geometries of the complexes vary from square-pyramidal to trigonal-bipyramidal (with ? ranging from 0.00 to 0.96) and, moreover, that the trigonal bipyramidal geometry becomes more preferable with the increase in the length of the polymethylene chain within the corresponding H2L(n) ligand. The magnetic properties of the polynuclear compounds 4, 5, 6, 7 and 8 were analysed using the spin Hamiltonian formalism, which revealed the presence of antiferromagnetic exchange in the polynuclear systems mediated by the title ligands. The significant effect of the geometric parameters on the CuCu exchange interactions in the polynuclear complexes is discussed. PMID:24671486

  12. A CHEMICAL MODEL OF THE SOLVENT EXTRACTION SYSTEM: NITRIC ACID URANYL NITRATE WATER - TRI-n-BUTYL PHOSPHATE (TBP) - DILUENT

    Microsoft Academic Search

    Joef J. ?omor; Miroslav M. Kope?ni; Djordje M. Petkovi?

    1997-01-01

    A mathematical model founded on the equilibrium constants expressions has been developed for the simultaneous extraction of nitric acid and uranyl nitrate with TBP in alkane diluents. The model uses chemical activities of nitric acid and uranyl nitrate in the aqueous phase and the stoichiometric concentrations of their TBP solvates in the organic phase. The apparent formation constants of the

  13. Periodic Trends within a Series of Five-Coordinate Thiolate-Ligated [MII(SMe2N4(tren))]+ (M ) Mn, Fe, Co, Ni, Cu, Zn) Complexes, Including a

    E-print Network

    Kovacs, Julie

    Periodic Trends within a Series of Five-Coordinate Thiolate-Ligated [MII(SMe2N4(tren))]+ (M ) Mn-ligated complexes [MII (tren)N4SMe2 ]+ (M ) Mn, Fe, Co, Ni, Cu, Zn; tren ) tris(2-aminoethyl)amine) are reported. All of the gem-dimethyl derivatized complexes are monomeric and, with the exception of [NiII (SMe2 N4

  14. Toxicity of depleted uranium complexes is independent of p53 activity

    PubMed Central

    Heintze, Ellie; Aguilera, Camille; Davis, Malia; Fricker, Avery; Li, Qiang; Martinez, Jesse; Gage, Matthew J.

    2010-01-01

    The p53 tumor suppressor protein is one of the key checkpoints in cellular response to a variety of stress mechanisms, including exposure to various toxic metal complexes. Previous studies have demonstrated that arsenic and chromium complexes are able to activate p53, but there is a dearth of data investigating whether uranium complexes exhibit similar effects. The use of depleted uranium (DU) has increased in recent years, raising concern about DUs potential carcinogenic effects. Previous studies have shown that uranyl acetate and uranyl nitrate are capable of inducing DNA strand breaks and potentially of inducing oxidative stress through free radical generation, two potential mechanisms for activation of p53. Based on these studies, we hypothesized that either uranyl acetate or uranyl nitrate could act as an activator of p53. We tested this hypothesis using a combination of cytotoxicity assays, p53 activity assays, western blotting and flow cytometry. All of our results demonstrate that there is not a p53-mediated response to either uranyl acetate or uranyl nitrate, demonstrating that any cellular response to uranium exposure likely occurs in a p53-independent fashion under the conditions studied. PMID:21194611

  15. Iron (II) sorption to mineral surfaces in uranyl and silicate rich media

    SciTech Connect

    Tyler A. Sullens; Cynthia-May S. Gong; Kenneth R. Czerwinski

    2006-01-01

    Abstract - The unique composition of the Yucca Mountain repository site, which contains large concentrations of silicate in an oxidative environment, has required extensive research into compound formation involving uranium and iron(II) under such conditions. The possibility of uranium leakage from within the containment vessels into the near-field ground water, as well as iron leaching from the vessel itself, necessitates study of the individual contributions of these elements for compound formation. By mimicking the known silicate concentration found in surrounding ground water and varying concentrations of both uranyl and iron(II), subsequent precipitation of uranyl silicate phases has shown evidence of iron(II) sorption to the available sites on the mineral surface. The mineralization seems to be driven by the formation of uranyl silicate, in contrast to iron(III)-control of precipitation in the oxidated system. We present characterization of this system using ICP-AES/MS, EDAX, XRD, and single-crystal X-ray diffraction.

  16. Definitions Algebra of complex numbers

    E-print Network

    Lega, Joceline

    Definitions Algebra of complex numbers Polar coordinates form of complex numbers Check your knowledge Review of Complex Numbers Definitions, Algebra of complex numbers, Polar coordinates Review of Complex Numbers #12;Definitions Algebra of complex numbers Polar coordinates form of complex numbers Check

  17. Systematic theoretical study of the zero-field splitting in coordination complexes of Mn(III). Density functional theory versus multireference wave function approaches.

    PubMed

    Duboc, Carole; Ganyushin, Dmitry; Sivalingam, Kantharuban; Collomb, Marie-Nolle; Neese, Frank

    2010-10-01

    This paper presents a detailed evaluation of the performance of density functional theory (DFT) as well as complete active space self-consistent field (CASSCF)-based methods (CASSCF and second-order N-electron valence state perturbation theory, NEVPT2) to predict the zero-field splitting (zfs) parameters for a series of coordination complexes containing the Mn(III) ion. The physical origin of the experimentally determined zfs's was investigated by studying the different contributions to these parameters. To this end, a series of mononuclear Mn(III) complexes was chosen for which the structures have been resolved by X-ray diffraction and the zfs parameters have been accurately determined by high-field EPR spectroscopy. In a second step, small models have been constructed to allow for a systematic assessment of the factors that dominate the variations in the observed zfs parameters and to establish magnetostructural correlations. Among the tested functionals, the best predictions have been obtained with B3LYP, followed by the nonhybrid BP86 functional, which in turn is more successful than the meta-hybrid GGA functional TPSSh. For the estimation of the spin-orbit coupling (SOC) part of the zfs, it was found that the coupled perturbed SOC approach CP is more successful than the Pederson-Khanna method. Concerning the spin-spin interaction (SS), the restricted open-shell Kohn-Sham (ROKS) approach led to a slightly better agreement with the experiment than the unrestricted KS (UKS) approach. The ab initio state-averaged CASSCF (SA-CASSCF) method with a minimal active space and the most recent implementation that treats the SOC and SS contributions on an equal footing provides the best predictions for the zfs. The analysis demonstrates that the major contribution to the axial zfs parameter (D) originates from the SOC interaction but that the SS part is far from being negligible (between 10 and 20% of D). Importantly, the various excited triplet ligand field states account for roughly half of the value of D, contrary to popular ligand field models. Despite covering dynamic correlation contributions to the transition energies, NEVPT2 does not lead to large improvements in the results as the excitation energies of the Mn(III) d-d transitions are already fairly accurate at the SA-CASSCF level. For a given type of coordination sphere (e.g., elongated or compressed octahedron), the magnetic anisotropy of the Mn(III) ion, D, does not appear to be highly sensitive to the nature of the ligands, while the E/D ratio is notably affected by all octahedral distortions. Furthermore, the introduction of different halides into the coordination sphere of Mn(III) only leads to small effects on D. Nevertheless, it appears that oxygen-based ligands afford larger D values than nitrogen-based ligands. PMID:20828179

  18. Bimetallic M(V)(2)Cu(II)(3) (M = Mo, W) coordination complexes based on octacyanometalates: structures and magnetic variations tuned by chelated tetradentate macrocyclic ligands.

    PubMed

    Lim, Jeong Hak; You, Young Sin; Yoo, Houng Sik; Yoon, Jung Hee; Kim, Jae Il; Koh, Eui Kwan; Hong, Chang Seop

    2007-12-10

    Four octacyanometalate-based bimetallic Cu-M (M = Mo, W) assemblies coordinated by tetradentate macrocyclic ligands were prepared via self-assembly process in a stoichiometric ratio of [M(CN)8]3- and Cu(macrocycle)2+ and characterized in terms of structures and magnetic properties. The crystal structures are varied depending on the macrocycles used. The employment of cyclam with no pendant groups produced a one-dimensional chain (1) with a rope-ladder pattern, whereas macrocycles with side groups allowed for the formation of two-dimensional honeycomb-like architectures (2-4). From the crystal structures, the variations in apical Cu-Nax lengths and Cu-Nax-Cax angles on the bridging pathways are observed, which arises from the existence of side groups on macrocyclic ligands. The magnetic results reveal that all of the prepared compounds show ferromagnetic couplings between magnetic centers transimitted through CN bridges under the present structural parameters. Comparing the magnetic strength of the Cu-Mo (3d-4d; 2) and Cu-W (3d-5d; 3) complexes supports that 3d-5d magnetic coupling is stronger than 3d-4d because the 5d orbital is more diffuse than 4d. The magnetic analyses for 1-4 and related complexes tentatively suggest that, when the Cu-Nax distances are long enough, the axial Cu-Nax bond length in the bridging route may be one of the major structural parameters to determine the magnitude of the ferromagnetic exchange coupling. PMID:17985870

  19. Sorption of uranyl ions from various acido systems by amphoteric epoxy amine ion-exchange resins

    SciTech Connect

    Rychkov, V.N.; Radionov, B.K.; Molochnikov, L.S. [and others

    1995-03-01

    Sorption of uranyl ions by epoxy amine ampholytes with N-monomethylenephosphonic acid groups modified with pyridine or quaternary ammonium groups was studied under dynamic conditions. Heterocyclic nitrogen favors sorption of uranyl ion from fluoride, sulfate, and fluoride-sulfate solutions. The ESR studies of mono- and bimetallic forms of nitrogen-containing ampholytes with copper(II) as paramagnetic marker revealed the characteristics of uranium(VI) interaction with cation- and anion-exchange groups and its dependence on the fluoride content in solution.

  20. Removal of uranyl ions by p-hexasulfonated calyx[6]arene acid

    NASA Astrophysics Data System (ADS)

    Popescu (Ho?tuc), Ioana-Carmen; Petru, Filip; Humelnicu, Ionel; Mateescu, Marina; Militaru, Ecaterina; Humelnicu, Doina

    2014-10-01

    Radioactive pollution is a significant threat for the peoples health. Therefore highly effective radioactive decontamination methods are required. Ion exchange, biotechnologies and phytoremediation in constructed wetlands have been used as radioactive decontamination technologies for uranium contaminated soil and water remediation. Recently, beside those classical methods the calix[n]arenic derivatives utilization as radioactive decontaminators has jogged attention. The present work aims to present the preliminary research results of uranyl ion sorption studies on the p-hexasulfonated calyx[6]arenic acid. The effect of temperature, contact time, sorbent amount and uranyl concentration variation on sorption efficiency was investigated. Isotherm models revealed that the sorption process fit better Langmuir isotherm.

  1. BRD4 coordinates recruitment of pause release factor P-TEFb and the pausing complex NELF/DSIF to regulate transcription elongation of interferon-stimulated genes.

    PubMed

    Patel, Mira C; Debrosse, Maxime; Smith, Matthew; Dey, Anup; Huynh, Walter; Sarai, Naoyuki; Heightman, Tom D; Tamura, Tomohiko; Ozato, Keiko

    2013-06-01

    RNA polymerase II (Pol II) and the pausing complex, NELF and DSIF, are detected near the transcription start site (TSS) of many active and silent genes. Active transcription starts when the pause release factor P-TEFb is recruited to initiate productive elongation. However, the mechanism of P-TEFb recruitment and regulation of NELF/DSIF during transcription is not fully understood. We investigated this question in interferon (IFN)-stimulated transcription, focusing on BRD4, a BET family protein that interacts with P-TEFb. Besides P-TEFb, BRD4 binds to acetylated histones through the bromodomain. We found that BRD4 and P-TEFb, although not present prior to IFN treatment, were robustly recruited to IFN-stimulated genes (ISGs) after stimulation. Likewise, NELF and DSIF prior to stimulation were hardly detectable on ISGs, which were strongly recruited after IFN treatment. A shRNA-based knockdown assay of NELF revealed that it negatively regulates the passage of Pol II and DSIF across the ISGs during elongation, reducing total ISG transcript output. Analyses with a BRD4 small-molecule inhibitor showed that IFN-induced recruitment of P-TEFb and NELF/DSIF was under the control of BRD4. We suggest a model where BRD4 coordinates both positive and negative regulation of ISG elongation. PMID:23589332

  2. Borane B-C Bond Cleavage by a Low-Coordinate Iron Hydride Complex and N-N Bond Cleavage by the Hydridoborate Product

    PubMed Central

    Yu, Ying; Brennessel, William W.; Holland, Patrick L.

    2008-01-01

    The iron(II) hydride dimers [LRFe(?-H)2FeLR] (LMe = 2,4-bis(2,6-diisopropylphenylimino) pent-3-yl; LtBu = 2,2,6,6-tetramethyl-3,5-bis(2,6-diisopropylphenylimino)hept-4-yl) abstract hydrocarbyl groups from BR?3 (R? = Et, Ph) to give LRFeR? and LRFe(?-H)2BR?2. Mechanistic studies with R = R? = Me are consistent with a process in which the hyride dimer opens one Fe-H bond, and subsequent B-H bond formation is concerted with dissociation of an Fe-H unit. Cleavage of boron-carbon bonds is likely to proceed at least in part from transient quaternary borate anions. In a separate bond-breaking reaction, LMeFe(?-H)2BEt2 reacts with N2H4 to eject H2 from the bridging hydrides and cleave the N-N bond in the diaminoborate complex LMeFe(?-NH2)2BEt2. These novel bond-breaking reactions are facilitated by the low coordination number at the iron(II) center. PMID:18725998

  3. Iron oxide formation from FeCl2 solutions in the presence of uranyl (UO22+) cations and carbonate rich media

    NASA Astrophysics Data System (ADS)

    Doornbusch, Brodie; Bunney, Karl; Gan, Bee K.; Jones, Franca; Grfe, Markus

    2015-06-01

    The mineral goethite (?-FeOOH) has previously been investigated as a thermodynamically stable repository for many potentially toxic metals (e.g., Cd, Pb, Cu). The substitution of uranium (U as uranyl, UO22+) for Fe, however, has been studied sparingly, and conclusive uranium incorporation into the goethite structure has been obscured by formation of ploymineralic Fe systems that all appeared involved in U's sequestration. In this study, we investigated the formation of goethite from FeCl2 in the presence of seven nominal uranyl concentrations (0.2-4 mole percent, U/(U + Fe) 100) and characterised the solids using quantitative X-ray diffraction (QXRD), X-ray absorption fine structure (XAFS) spectroscopy at the U LIII edge (17,166 eV), diffuse reflectance infrared Fourier Transform (DRIFT) spectrometry and congruency of acid dissolution. Our findings show that U does indeed, however sparingly, incorporate into the goethite structure. The unit cell volume, ascertained from Rietveld models of XRD patterns, increased linearly as a function of U content, which could be ascribed to a linear increase of the unit cell length a and c. The highest U-for-Fe substitution was 0.48 mole percent, however, most U-containing goethite samples showed substitution levels around 0.2 mole percent, which was in good agreement with previous findings. DRIFT spectra showed a shift of the symmetric Fe-O and asymmetric Fe-OH stretch modes (?-O and ?-OH bands, respectively) to lower frequency, which by Hooks analogy, can only occur if a heavier atom substitutes for Fe, i.e., U. The congruency of acid dissolution results showed that fractional U release was greater than the corresponding fractional Fe release into solution, suggesting that U was overall more soluble. In two of the synthates, however, (initial U mole percent of 2 and 4), the dissolution was congruent. XAFS data collected on a selected subset of samples showed the disappearance of the uranyl moiety with higher levels of U incorporation and acid extraction. In sample S6, non-linear least-square fits of the extended XAFS data demonstrated that the coordination environment around U atoms was sixfold occupied by O/OH atoms and was further coordinated by next nearest Fe neighbours that are 1.063 0.008 times inflated in distance to the normal Fe-Fe distances in goethite without U substitution. Despite low levels of incorporation, U bound by goethite was recalcitrant to desorption/dissolution in increasingly acidic solutions thus warranting further research into the possibility of using iron oxides as a sink for U.

  4. Binuclear complexes of technetium. Evidence for bis(terdentate)bidentate coordination by the bridging ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine to technetium(V)

    SciTech Connect

    Du Preez, J.G.H.; Gerber, T.I.A.; Gibson, M.L.; Geyser, R. (Univ. of Port Elizabeth (South Africa))

    1990-01-01

    The authors have used the potentially bis(terdentate) nitrogen aromatic heterocyclic ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) to prepare mono- and bimetallic technetium(V) complexes bound to tppz. The stimulus for the development of the coordination chemistry of the man-made element technetium is provided by the use of complexes of this element as anatomical imaging agents in nuclear medicine. Although the chemistry of technetium(V) with nitrogen donor ligands is well understood, no complexes have been prepared using potentially terdentate neutral nitrogen donor ligands of this metal in the +5 oxidation state.

  5. Astronomical Coordinates

    NSDL National Science Digital Library

    David Joiner

    The celestial coordinate system is a projection of earth's coordinate system into the celestial sphere. Being just like Earth's system it contains an "equator", lines of "latitude" and "longitude", and even poles. (Though we don't use the same words for it.) One suggestion one might have would be to just extend the Earth's latitude, longitude, and equator out into the night sky, but the Earth is constantly spinning. For the Celestial coordinates, we have to pick some fixed reference to go by.

  6. Metal complexes of the fourth generation quinolone antimicrobial drug gatifloxacin: Synthesis, structure and biological evaluation

    NASA Astrophysics Data System (ADS)

    Sadeek, Sadeek A.; El-Shwiniy, Walaa H.

    2010-08-01

    Three metal complexes of the fourth generation quinolone antimicrobial agent gatifloxacin (GFLX) with Y(???), Zr(?V) and U(V?) have been prepared and characterized with physicochemical and spectroscopic techniques. In these complexes, gatifloxacin acts as a bidentate deprotonated ligand bound to the metal through the ketone oxygen and a carboxylato oxygen. The complexes are six-coordinated with distorted octahedral geometry. The kinetic parameters for gatifloxacin and the three prepared complexes have been evaluated from TGA curves by using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The calculated bond length and force constant, F(U dbnd O), for the UO 2 bond in uranyl complex are 1.7522 and 639.46 N m -1. The antimicrobial activity of the complexes has been tested against microorganisms, three bacterial species, such as Staphylococcus aureus ( S. aureus), Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) and two fungi species, penicillium ( P. rotatum) and trichoderma ( T. sp.), showing that they exhibit higher activity than free ligand.

  7. Standard test method for isotopic analysis of hydrolyzed uranium hexafluoride and uranyl nitrate solutions by thermal ionization mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This method applies to the determination of isotopic composition in hydrolyzed nuclear grade uranium hexafluoride. It covers isotopic abundance of 235U between 0.1 and 5.0 % mass fraction, abundance of 234U between 0.0055 and 0.05 % mass fraction, and abundance of 236U between 0.0003 and 0.5 % mass fraction. This test method may be applicable to other isotopic abundance providing that corresponding standards are available. 1.2 This test method can apply to uranyl nitrate solutions. This can be achieved either by transforming the uranyl nitrate solution to a uranyl fluoride solution prior to the deposition on the filaments or directly by depositing the uranyl nitrate solution on the filaments. In the latter case, a calibration with uranyl nitrate standards must be performed. 1.3 This test method can also apply to other nuclear grade matrices (for example, uranium oxides) by providing a chemical transformation to uranyl fluoride or uranyl nitrate solution. 1.4 This standard does not purport to address al...

  8. Geoboard - Coordinate

    NSDL National Science Digital Library

    1999-01-01

    This interactive Java applet lets users explore the coordinate plane through the use of a Geoboard. The user places bands on the board where each peg is at an integer coordinate. Once a band has been placed, the applet outputs the perimeter and area of the shape or, if bands are placed as line segments, the applet outputs the distance and slope of the segment.

  9. Synthesis, and characterization of low- and high-spin manganese(II) complexes of polyfunctional adipoyldihydrazone: Effect of coordination of N-donor ligands on stereo-redox chemistry

    NASA Astrophysics Data System (ADS)

    Basumatary, Debajani; Lal, Ram Ashray; Kumar, Arvind

    2015-07-01

    Manganese(II) complexes [MnII(npahH2)] (1), [MnII(npahH2)(A)2] and [MnII(npahH2)(NN)] (where A = pyridine, (2); 2-picoline, (3); 3-picoline, (4); 4-picoline, (5) and NN = 2,2? bipyridine, (6); 1,10-phenanthroline, (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone (npahH4) in methanol. The composition of metal complexes has been established by elemental analyses. Complexes (1) and (3) have been characterized by mass spectral data also. Structural assessments of the complexes have been based on data obtained from molar conductance, magnetic moment, electronic, electron paramagnetic resonance and infrared spectral studies. Conductivity measurements in DMSO suggest that they are non-electrolyte. Electronic spectral studies suggest a six-coordinate octahedral geometry around the manganese center in complexes (2) to (7) and square-planar geometry in complex (1). IR spectral studies reveal that the dihydrazone coordinates to the metal in keto form with an anti-cis configuration. Magnetic moment, and EPR studies suggest manganese in +2 oxidation state in all complexes with high-spin distorted octahedral stereochemistry in complexes (2-7) while low-spin square-planar stereochemistry is involved with significant metal-metal interactions in the solid state in complex (1). Cyclic voltammetric studies reveal that the metal center cycles among the MnII ? MnI ? Mn0 in complexes (2) to (7) and among MnII ? MnI oxidation states in complex (1).

  10. Uranyl nitrate pouring solution for producing nuclear fuel particles and a method for its preparation

    Microsoft Academic Search

    Hein

    1983-01-01

    Sorbitol, or another polyalcohol such as erythritol, dulcitol or xylitol, is added to a solution containing uranyl nitrate which may also contain another heavy metal, such as thorium or plutonium, prior to preneutralization with ammonia in order to provide a highly viscous solution that can be preneutralized to a great extent without premature precipitation of uranium. The high viscosity makes

  11. Solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate

    Microsoft Academic Search

    B. K. Medkov; M. R. Petrov; O. N. Roslyakova

    1988-01-01

    The solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate at 25°C containing 10, 20 and 30 mass % of nitric acid has been studied by the isothermal method. The Schreinemakers method has been used to establish the composition of the solid phases, which has been confirmed by crystallographic and thermographic studies. Data are presented on the viscosity

  12. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

    Microsoft Academic Search

    1995-01-01

    DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO

  13. Degree of dissociation of HNO in aqueous solutions saturated with uranyl nitrate

    Microsoft Academic Search

    Y. S. Fedorov; B. Y. Zilberman

    1986-01-01

    A method has been proposed for the comparative extraction by an inert solvent to find the degree of dissociation of HNO in solutions containing nitrate salts, for example uranyl nitrate. It was shown that in the case of equality of ratios of the ionic strength of the solution to the concentration of water in it, the degree of dissociation of

  14. Critical experiments on 10% enriched uranyl nitrate solution using a 60-cm-diameter cylindrical core

    Microsoft Academic Search

    Yoshinori Miyoshi; Takuya Umano; Kotaro Tonoike; Naoki Izawa; Susumu Sugikawa; Shuji Okazaki

    1997-01-01

    A series of critical experiments with 10% enriched uranyl nitrate solution using a cylindrical core tank 60 cm in diameter have been performed with the Static Experiment Critical Facility at the Nuclear Fuel Cycle Safety Engineering Research Facility in the Tokai research establishment of the Japan Atomic Energy Research Institute. In the first series of experiments using the cylindrical core

  15. The System Uranyl Nitrate-Water-Tributylphosphate-Carbon Tetrachloride; HET SYSTEEM: URANYLNITRAAT-WATER-TRIBUTYLFOSFAAT- TETRACHLOORKOOLSTOF

    Microsoft Academic Search

    Van Aartsen

    1962-01-01

    The extraction of uranyl nitrate from aqueous solutions by mixtures of ; tri-n-butyl phosphate (TBP) and carbon tetrachloride is governed by the ; equilibrium compositions on either side of the miscibility gap in the quaternary ; system UO(NO)-- HO- TBP- CCl. Thermodynamic ; desc riptions of nonideal behavior in binary and ternary mixtures are first ; discussed. The materials used,

  16. Calculation of Phase Equilibria in Ternary Systems Uranyl Salt-Water-Organic Solvent

    Microsoft Academic Search

    M. A. Myagkova-Romanova; L. L. Makarov

    2001-01-01

    Simulation of extraction equilibria in systems consisting of uranyl salt (nitrate, haloacetates), water, and oxygen-containing organic solvent was performed. A method based on a thermodynamic approach was suggested for calculating equilibria, and phase diagrams of 12 extraction systems were calculated. The results were compared with available experimental data, and the efficiency of systems that were not studied experimentally was predicted.

  17. A new test for uranyl ions based on its redox properties

    Microsoft Academic Search

    F. Lucena-Conde; L. Prat

    1955-01-01

    Summary A new test for uranyl ions is proposed. The solution is reduced with liquid zinc amalgam or metallic aluminium. A drop of the reduced solution is treated with excess of ferric iron, and the ferrous ions produced are detected with 1,10-phenanthroline. The test can be improved if the reduced solution is treated with thorium nitrate and ammonium fluoride. The

  18. Depleted uraniumuranyl chloride induces apoptosis in mouse J774 macrophages

    Microsoft Academic Search

    John F Kalinich; Narayani Ramakrishnan; Vilmar Villa; David E McClain

    2002-01-01

    Depleted uranium entering the body as a result of inhalation or embedded fragments becomes associated to a great extent with macrophages. As part of our continuing studies on the health effects of internalized depleted uranium, we investigated the effect of soluble depleted uraniumuranyl chloride on the mouse macrophage cell line, J774. Using a cytochemical staining protocol specific for uranium, we

  19. Molecular dynamics simulation of uranyl(VI) sorption equilibria onto an external montmorillonite surface

    Microsoft Academic Search

    Randall Timothy Cygan; Jeffery A. Greathouse

    2005-01-01

    We used molecular dynamics simulations to study the adsorption of aqueous uranyl species (UO22+) onto clay mineral surfaces in the presence of sodium counterions and carbonato ligands. The large system size (10 000 atoms) and long simulation times (10 ns) allowed us to investigate the thermodynamics of ion adsorption, and the atomistic detail provided clues for the observed adsorption behavior.

  20. Robust iron coordination complexes with N-based neutral ligands as efficient Fenton-like catalysts at neutral pH.

    PubMed

    Canals, Maite; Gonzalez-Olmos, Rafael; Costas, Miquel; Company, Anna

    2013-09-01

    The homogeneous Fenton-like oxidation of organic substrates in water with hydrogen peroxide, catalyzed by six different metal coordination complexes with N-based neutral ligands, was studied at ambient conditions and initial pH 7, employing hydrogen peroxide as the terminal oxidant. At low catalyst concentration, the catalytic oxidative depletion of toluene achieved by selected catalysts was much more efficient than that obtained by the Fenton reagent at pH 3. The influence of pH, the water matrix and the catalyst/hydrogen peroxide concentration were investigated for the oxidation of toluene employing [FeCl2(bpmcn)] (1, bpmcn = N,N'-bis(2-pyridylmethyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), the most efficient catalyst of the series. Moreover, the evolution of catalysts [FeCl2(bpmcn)] (1) and [Fe(OTf)2(Pytacn)] (3, Pytacn = 1-(2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, OTf = trifluoromethanesulfonate anion) during the course of the reaction was also studied by electrospray ionization mass spectrometry (ESI-MS). The oxidation products derived from toluene oxidation were also analyzed. A plausible mechanism of toluene degradation using [FeCl2(bpmcn)] (1) and [Fe(OTf)2(Pytacn)] (3) as catalysts was proposed, which involves the coexistence of a metal-based path, analogous to that operating in organic media where substrate oxidation is executed by an iron(V)-oxo-hydroxo species, in parallel to a Fenton-type process where hydroxyl radicals are formed. PMID:23895017

  1. Extraction of uranyl nitrate with a binary extractant based on di(2,4,4-trimethylpentyl)phosphinic acid

    Microsoft Academic Search

    N. S. Egorova; V. V. Belova; A. A. Voshkin; A. I. Kholkin; A. K. Pyartman; V. A. Keskinov

    2008-01-01

    The extraction of uranyl nitrate with methyltrioctylammomium di(2,4,4-trimethylpentyl)phosphinate is compared to uranyl nitrate\\u000a extraction with constituent cation-and anion-exchange extracting agents at various compositions of aqueous and organic phases.\\u000a In UO2(NO3)2 extraction with quaternary ammonium nitrate and dialkylphosphinic acid solutions in toluene, the compounds (R4N)2UO2(NO3)4 and UO2A2, respectively, are formed in the organic phase. The binary extraction of uranyl nitrate is

  2. Crystal Chemistry of the Potassium and Rubidium Uranyl Borate Families Derived from Boric Acid Fluxes

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-01-01

    The reaction of uranyl nitrate with a large excess of molten boric acid in the presence of potassium or rubidium nitrate results in the formation of three new potassium uranyl borates, K{sub 2}[(UO{sub 2}){sub 2}B{sub 12}O{sub 19}(OH){sub 4}]0.3H{sub 2}O (KUBO-1), K[(UO{sub 2}){sub 2}B{sub 10}O{sub 15}(OH){sub 5}] (KUBO-2), and K[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]0.7H{sub 2}O (KUBO-3) and two new rubidium uranyl borates Rb{sub 2}[(UO{sub 2}){sub 2}B{sub 13}O{sub 20}(OH){sub 5}] (RbUBO-1) and Rb[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]0.7H{sub 2}O (RbUBO-2). The latter is isotypic with KUBO-3. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers and are directed approximately perpendicular to the sheets. All of these compounds adopt layered structures. With the exception of KUBO-1, the structures are all centrosymmetric. All of these compounds fluoresce when irradiated with long-wavelength UV light. The fluorescence spectrum yields well-defined vibronically coupled charge-transfer features.

  3. New insight of coordination and extraction of uranium(VI) with N-donating ligands in room temperature ionic liquids: N,N'-diethyl-N,N'-ditolyldipicolinamide as a case study.

    PubMed

    Yuan, Li-Yong; Sun, Man; Mei, Lei; Wang, Lin; Zheng, Li-Rong; Gao, Zeng-Qiang; Zhang, Jing; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-02-16

    Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium(VI) with N-donating ligands, e.g., N,N'-diethyl-N,N'-ditolyldipicolinamide (EtpTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U(VI), and crystallographic studies of the interactions of EtpTDPA with U(VI) were performed, including the first structurally characterized UO2(EtpTDPA)2(NTf2) and UO2(EtpTDPA)2(PF6)2 compounds and a first case of crystallographic differentiation between the extracted U(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two EtpTDPA molecules coordinate with one U(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf2(-) and PF6(-) act as counterions. The absence of NO3(-) in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO2(2+) coordinates in a neutral complex form with one EtpTDPA molecule and two NO3(-) cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO2(NO3)2, EtpTDPA, and LiNTf2 or KPF6 in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U(VI) and EtpTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the counterions of uranyl or introducing extra anions. PMID:25629464

  4. Designed Single-Step Synthesis, Structure, and Derivative Textural Properties of Well-Ordered Layered Penta-coordinate Silicon Alcoholate Complexes

    E-print Network

    Li, Xiansen

    The controllable synthesis of well-ordered layered materials with specific nanoarchitecture poses a grand challenge in materials chemistry. Here the solvothermal synthesis of two structurally analogous 5-coordinate ...

  5. ALTERNATIVE MODELS FOR PREDICTING THE EXTRACTION OF WATER AND URANYL NITRATE IN THE TWO-PHASE SYSTEM: WATER-URANYL NITRATE-TRIBUTYL PHOSPHATE-AMSCO 125-82

    Microsoft Academic Search

    D. William Tedder; Wallace Davis Jr

    1983-01-01

    Experimental data for the distribution of uranyl nitrate and water between an aqueous phase and an organic phase containing 5-100 vol % trlbutyl phosphate (TBP) in an odorless kerosene-like diluent (Amsco 125-82) have been reexamined by considering alternative models in which competitive equilibria involving water and uranyl nitrate are assumed. These models are compared and contrasted with earlier analyses which

  6. Acid-Base and Metal Ion-Coordinating Properties of Pyrimidine-Nucleoside 5'-Diphosphates (CDP, UDP, dTDP) and of Several Simple Diphosphate Monoesters. Establishment of Relations between Complex Stability and Diphosphate Basicity.

    PubMed

    Sajadi, S. Ali A.; Song, Bin; Gregn, Fridrich; Sigel, Helmut

    1999-02-01

    The stability constants of the 1:1 complexes formed between Mg(2+), Ca(2+), Sr(2+), Ba(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) and the pyrimidine-nucleoside 5'-diphosphates CDP(3)(-), UDP(3)(-), and dTDP(3)(-) (= NDP(3)(-)) were determined by potentiometric pH titration in aqueous solution (I = 0.1 M, NaNO(3); 25 degrees C). For comparison, the same values were measured for the corresponding complexes with the simple diphosphate monoesters (R-DP(3)(-)) phenyl diphosphate, methyl diphosphate, and n-butyl diphosphate. The acidity constants for H(3)(CDP)(+/-), H(2)(UDP)(-), H(2)(dTDP)(-), and H(2)(R-DP)(-) were measured also via potentiometric pH titration and various comparisons with related constants are made. By plotting log versus for the complexes of all six diphosphates mentioned and by a careful evaluation of the deviation of the various data pairs from the straight-line correlations, the expectation is confirmed that in the M(UDP)(-) and M(dTDP)(-) complexes the metal ion is only diphosphate-coordinated. The straight-line equations, which result from the mentioned correlations, together with the pK(a) value of a given monoprotonated diphosphate monoester allow now to predict the stability of the corresponding M(R-DP)(-) complexes. In this way, the experimentally determined stability constants for the M(CDP)(-) complexes are evaluated and it is concluded that the pyridine-like N3 of the cytosine residue does not participate in complex formation; i.e., the stability of the M(CDP)(-) complexes is also solely determined by the coordination tendency of the diphosphate residue. In all the monoprotonated M(H;NDP) and M(H;R-DP) complexes both, H(+) and M(2+), are bound at the diphosphate group. Only the Cu(H;CDP) complex exists in aqueous solution in the form of three different isomers: about 15% of the species have Cu(2+) and H(+) at the diphosphate residue, in about 13% Cu(2+) is bound at N3 and H(+) at the terminal beta-phosphate group, and the dominating isomer with about 72% carries the proton at N3 and the metal ion at the diphosphate residue. Several general features of phosphate-metal ion coordination are discussed, and estimations for the stabilities of the Fe(2+) complexes formed with mono-, di-, and triphosphate monoesters are provided. PMID:11673946

  7. Synthesis, characterisation and crystal structures of a few coordination complexes of nickel(II), cobalt(III) and zinc(II) with N?-[(2-pyridyl)methylene]salicyloylhydrazone Schiff base

    Microsoft Academic Search

    Brajagopal Samanta; Joy Chakraborty; Shyamapada Shit; Stuart R. Batten; Paul Jensen; Jason D. Masuda; Samiran Mitra

    2007-01-01

    Four new coordination complexes, NiII(L)2 (1), [CoIII(L)2]ClO4 (2), [Zn(HL)(L)]ClO4H2O (3) and [Zn(L)2][Zn(L)(HL)]ClO47H2O (4) (where L is a monoanion of a Schiff base ligand, N?-[(2-pyridyl)methylene]salicyloylhydrazone (HL) with NNO tridentate donor set), have been synthesised and systematically characterised by elemental analysis, spectroscopic studies and room temperature magnetic susceptibility measurements. Single crystal X-ray diffraction analysis reveals that 1 is a neutral complex, while

  8. Syntheses, crystal structures and properties of two new coordination complexes containing 1,2,4,5-benzenetetracarboxylate and imidazole: [Ni 2(Him) 12 (bta) 8H 2O] and [Cd 2(Him) 4(? 4-bta)

    Microsoft Academic Search

    Jiang-Feng Song; Rui-Sha Zhou; Xiao-Yu Xu; Ya-Bing Liu; Tie-Gang Wang; Ji-Qing Xu

    2008-01-01

    Two new coordination complexes, [Ni2(Him)12(bta)8H2O] 1 and [Cd2(Him)4(bta)] 2, (H4bta=1,2,4,5-benzenetetracarboxylic acid, Him=imidazole) were prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. X-ray diffraction reveals that complex 1, consisting of two crystallographically independent [Ni(Him)6]2+ fragments, an uncoordinated bta4? anion and eight lattice water molecules, displays an interesting 3D supramolecular network constructed by cationic layers (layer A)

  9. Uptake of uranyl ions from uranium ores and sludges by means of Spirulina platensis, Porphyridium cruentum and Nostok linckia alga.

    PubMed

    Cecal, Alexandru; Humelnicu, Doina; Rudic, Valeriu; Cepoi, Liliana; Ganju, Dumitru; Cojocari, Angela

    2012-08-01

    In this paper was studied the uranyl ions biosorption on three types of alga: Nostok linckia, Porphyridium cruentum and Spirulina platensis. These ions were supplied either from a pure solution of uranyl nitrate, or after leaching process of uranium ore, or from the sludge resulting in the output of pure UO(2) technology. It was investigated the retention degree versus contact time and afterwards the Langmuir and Freundlich biosorption isotherms of uranyl ions on the three alga types. The retention of UO(2)(2+) ions on alga was proved through FTIR spectra plotted before and after biosorption processes. From the experimental data it was found that regardless of origin of uranyl ions, the retention degree on alga decreased in the series. Spirulina platensis > Porphyridium cruentum ? Nostok linckia. PMID:22695141

  10. Coordinates Constellations

    E-print Network

    Walter, Frederick M.

    ;Ecliptic Coordinates #12;Earth's Orbit #12;Analemma The position of the Sun at civil noon (standard time). This demonstrates: The inclination of the ecliptic The equation of time The non-circularity of Earth's orbit #12;Constellations There are about 6000 stars visible to the naked eye under good conditions About 2000

  11. COORDINATED AV.

    ERIC Educational Resources Information Center

    CLEAVES, PAUL C.; AND OTHERS

    THE INSTRUCTIONAL MATERIALS CENTER IS LOCATED IN THE LOCAL HIGH SCHOOL AND SUPPLIES ALL SCHOOLS IN THE AREA. AUDIOVISUAL EQUIPMENT ORDERS, AFTER SELECTIONS ARE MADE BY THE CLASSROOM TEACHER, ARE PROCESSED BY THE CENTER, CONFIRMED AND DELIVERED BY TRUCK THREE TIMES EACH WEEK. EACH SCHOOL HAS A BUILDING COORDINATOR WHO CHECKS THE ORDERS INTO THE

  12. FLUIDIZED-BED PROCESS FOR THE PRODUCTION OF URANIUM TETRAFLUORIDE (GREEN SALT) FROM URANYL NITRATE. Interim Report

    Microsoft Academic Search

    A. A. Jonke; N. M. Levitz; E. J. Petkus; R. G. Taecker

    1954-01-01

    A proposed new processing technique for the production of uranium ;\\u000a tetrafluoride from uranyl nitrate solution is described. This technique involves ;\\u000a the application of the fluidized-bod principle for the contacting of gases with ;\\u000a powdered solids. A new application of fluidization developed at this Laboratory ;\\u000a and applied to the denitration of uranyl nitrate to produce uranium trioxide is

  13. Synthesis, crystal structures, magnetic properties and catecholase activity of double phenoxido-bridged penta-coordinated dinuclear nickel(II) complexes derived from reduced Schiff-base ligands: mechanistic inference of catecholase activity.

    PubMed

    Biswas, Apurba; Das, Lakshmi Kanta; Drew, Michael G B; Arom, Guillem; Gamez, Patrick; Ghosh, Ashutosh

    2012-08-01

    Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni(2)(L(1))(2)(NCS)(2)] (1), [Ni(2)(L(2))(2)(NCS)(2)] (2), and [Ni(2)(L(3))(2)(NCS)(2)] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL(1)), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL(2)), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL(3)), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter ? = 0.47) and 3 (? = 0.29), while it is almost perfect for 2 (? = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm(3) K mol(-1), in the convention H = -2JS(1)S(2)). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes. PMID:22759340

  14. Addition of H2O and O-2 to Acetone and Dimethylsulfoxide Ligated Uranyl (V) Dioxocations

    SciTech Connect

    C. M. Leavitt; V. S. Bryantsev; W. A. deJong; M. S. Diallo; W. A. Goddard III; G. S. Groenewold; M. J. Van Stipdonk

    2009-03-01

    Gas-phase complexes of the formula [UO2(lig)]+ (lig = acetone (aco) or dimethylsulfoxide (dmso)) were generated by electrospray ionization (ESI) and studied by tandem ion-trap mass spectrometry to determine the general effect of ligand charge donation on the reactivity of UO2+ with respect to water and dioxygen. The original hypothesis that addition of O2 is enhanced by strong s-donor ligands bound to UO2+ is supported by results from competitive collision-induced dissociation (CID) experiments, which show near exclusive loss of H2O from [UO2(dmso)(H2O)(O2)]+, whereas both H2O and O2 are eliminated from the corresponding [UO2(aco)(H2O)(O2)]+ species. Ligand-addition reaction rates were investigated by monitoring precursor and product ion intensities as a function of ion storage time in the ion-trap mass spectrometer: these experiments suggest that the association of dioxygen to the UO2+ complex is enhanced when the more basic dmso ligand was coordinated to the metal complex. Conversely, addition of H2O is favored for the analogous complex ion that contains an aco ligand. Experimental rate measurements are supported by density function theory calculations of relative energies, which show stronger bonds between UO2+ and O2 when dmso is the coordinating ligand, whereas bonds to H2O are stronger for the aco complex.

  15. On a new coordinate system with astrophysical application: Spiral coordinates

    NASA Astrophysics Data System (ADS)

    Campos, L. M. B. C.; Gil, P. J. S.

    In this presentation are introduced spiral coordinates, which are a particular case of conformal coordinates, i.e. orthogonal curvelinear coordinates with equal factors along all coordinate axis. The spiral coordinates in the plane have as coordinate curves two families of logarithmic spirals, making a constant angle, respectively phi and pi / 2-phi, with all radial lines, where phi is a parameter. They can be obtained from a complex function, representing a spiral potential flow, due to the superposition of a source/sink with a vortex; the parameter phi in this case specifies the ratio of the ass flux of source/sink to the circulation of the vortex. Regardless of hydrodynamical or other interpretations, spiral coordinates are particulary convenient in situation where physical quantities vary only along a logarithmicspiral. The example chosen is the propagation of Alfven waves along a logarithmic spiral, as an approximation to Parker's spiral. The equation of dissipative MHD are written in spiral coordinates, and eliminated to specify the Alfven wave equation in spiral coordinates; the latter is solved exactly in terms of Bessel functions, and the results analyzed for values of the parameters corresponding to the solar wind.

  16. Supramolecular Chemistry of 4,4'-Bipyridine-N,N'-dioxide in Transition Metal Complexes: A Rich Diversity of Co-ordinate, Hydrogen-Bond and Aromatic Stacking Interactions

    NASA Astrophysics Data System (ADS)

    Jia, Junhua; Hubberstey, Peter; Champness, Neil R.; Schrder, Martin

    4,4'-Bipyridine-N,N'-dioxide (L1) has enormous flexibility as a supramolecular linker since it can be involved not only in co-ordinate and hydrogen bonds via its N,N'-dioxide oxygen centres, but the pyridine-N-oxide rings can also form aromatic ?-? stacking interactions. Thus, L1 can bridge between, or act as a pendant ligand to metal centres and can support hydrogen-bonds within a lattice in a site remote from the metal centre. Of the structurally characterised transition metal complexes abstracted from the literature for this review, 26 form molecular compounds, 14 form 1D chains, 9 form 2D sheets of either 36, 44 or 63 topology, while 5 form 3D networks with either 41263 (?-Po type) or 48668 topology. To target multidimensional architectures it has been found to be necessary to avoid aqueous solutions and strongly co-ordinating anions, and consequently the synthesis of multidimensional L1-bridged transition metal co-ordination polymers has usually involved reaction of L1 with metal salts of weakly co-ordinating anions in low molecular weight alcohols. Of the 98 distinct molecules of L1 reported for complexes in the literature, 42 are bridging, 36 pendant and 20 are non-co-ordinated hydrogen-bonded molecules. Approximately 75% of the bridging L1 molecules adopt an anti-conformation, while the remainder adopt a syn-conformation. This prevalence of the anti-conformation contrasts markedly with the situation observed for lanthanide compounds, for which approximately 75% adopt a syn-conformation. A number of trends in the co-ordination behaviour of L1 with transition metals can be identified. Co-ordination to metal centres is based on sp 2 hybridised oxygen donors, but the ?-interaction between the oxygen p z orbital and the aromatic ring is sufficiently weak that the oxygen lone pairs are normally twisted out of the plane of the pyridine-N-oxide by a steric clash between the metal centre and the ?-hydrogen of the pyridine ring. As a result of this steric hindrance, complexes containing anti- and syn-conformation bridging ligands fall in similar ranges. However, those with syn-conformation ligands show an increase in M \\cdots M separation with increasing

  17. Coordinate Plane

    NSDL National Science Digital Library

    Miss Zilles

    2007-10-31

    5th Grade Math State core Standard 3, Objective 2a: Locate points defined by ordered pairs of integers. Congratulations for earning a game day in the computer lab! Remember that even though it is game day I expect you to stay on task and follow directions. We have been talking in math about graphing integers on the coordinate plane. The games for today require that ...

  18. Polymerization of acrylamide at acid pH using uranyl nitrate

    SciTech Connect

    Deshpande, V.V.; Bodhe, A.M.; Pawar, H.S.; Vartak, H.G.

    1986-03-01

    A new photopolymerizing reagent, uranyl nitrate, is used for the polymerization of acrylamide gels at low pH. The amount of uranyl nitrate (0.2 mg/ml) required for the polymerization of gels at pH 3.0 is considerably less than that of persulfate (7 mg/ml). Use of this reagent obviates the need for the removal of excess of persulfate by preelectrophoresis. The electrophoretic separation of basic proteins in uranium-polymerized gels showed faster movement and better resolution of proteins and proved the gels to be versatile, uniform, and reproducible. Electrophoresis of trypsin in these gels does not affect the enzymatic activity. The catalyst can also be used for the polymerization of gels containing 3 M urea.

  19. Evolution of the synaptonemal complex in Helix aspersa spermatocytes

    Microsoft Academic Search

    P. Esponda; J. C. Stockert

    1972-01-01

    In spermatocytes of Helix aspersa, the structure of the synaptonemal complexes undergoes changes in the course of the pachytene, the lateral elements being transformed into wide bands of lesser density than the chromatin. By using the uranyl-EDTA-lead sequence, which preferentially stains RNA, the lateral elements can be made to appear positive in the early pachytene while the corresponding areas, which

  20. Reactive transport of uranyl in a goethite column: an experimental and modelling study

    Microsoft Academic Search

    U. Gabriel; J.-P. Gaudet; L. Spadini; L. Charlet

    1998-01-01

    We investigated the adsorption of uranium(VI) at atmospheric CO2 partial pressure in a bicarbonate background ionic medium (pH 9.00.2). Goethite-coated sand was used as mine tailings model material. Both static, i.e., batch, and dynamic, i.e., column, experiments were performed. In the column experiments, uranyl adsorption was found to be far from local equilibrium at a pore velocity of 12.1 cm

  1. THIRD PHASE FORMATION IN THE EXTRACTION OF URANYL NITRATE BY N,N-DIALKYL ALIPHATIC AMIDES

    Microsoft Academic Search

    K. K. Gupta; V. K. Manchanda; S. Sriram; George Thomas; P. G. Kulkarni; R. K. Singh

    2000-01-01

    Studies on third phase formation during the extraction of uranyl nitrate from nitric acid media by N,N-dihexyl derivatives of n-hexanamide (DHHA) and n-octanamide (DHOA) in n-dodecane have been carried out. Limiting organic concentration (LOC) of uranium(VI), above which the third phase formation takes place, has been evaluated as a function of nitric acid concentration, extractant concentration, temperature and the ionic

  2. Studies of the biochemical toxicology of uranyl nitrate in the rat

    Microsoft Academic Search

    Maria L. Anthonyl; Kevin P. R. Gartlandl; Christopher R. Beddell; John C. Lindon; Jeremy K. Nicholsonl

    1994-01-01

    High resolution 1H NMR spectroscopy of urine and plasma, conventional clinical chemical methods and histopathology have been applied to investigate\\u000a the effects of uranyl nitrate (UN) on renal function and biochemistry in the Fischer 344 (F344) rat. Administration of UN\\u000a (520 mg\\/kg) to male F344 rats resulted in a dose-related proximal nephropathy assessed conventionally by histopathology and\\u000a urinary excretion of

  3. Chronic ingestion of uranyl nitrate perturbs acetylcholinesterase activity and monoamine metabolism in male rat brain

    Microsoft Academic Search

    C. Bussy; P. Lestaevel; B. Dhieux; C. Amourette; F. Paquet; P. Gourmelon; P. Houpert

    2006-01-01

    Recent animal studies have shown that uranium can reach the brain after chronic exposure. However, little information is available on the neurological effects of chronic long-term exposure to uranium. In the present study, the effects during 1.5, 6 and 9-month periods of chronic ingestion of uranyl nitrate (UN) in drinking water (40mg of uranium per litre) on cholinergic acetylcholinesterase (AChE)

  4. DENSITIES AND BOILING POINTS OF URANYL NITRATE-NITRIC ACID SOLUTIONS

    Microsoft Academic Search

    Perkins

    1953-01-01

    The intercycle evaporators in the Chemical Processing Plant are controlled by density-measuring instruments. Because of difficulties in controlling these evaporators in a satisfactory manner, a series of investigations was begun to measure the boiling points at the elevation of the CPP, and densities near boiling temperatures of a number of solutions in the uranyl nitrate-nitric acid-water system. From these data

  5. STUDIES OF JOINT SOLUBILITY OF URANYL NITRATE AND NITRATES OF ALKALI EARTH METALS IN WATER

    Microsoft Academic Search

    M. A. Yakimov; N. F. Nosova; V. A. Grishin

    1958-01-01

    Isothermic solubility was studied in ternary systems H O, 25, and ; 50 d . The eutectoid point for this system was not found. Three ; solubiliiy curves corresponding to the solubility of tetrahydrate of strontium ; nitrate, anhydrous strontium nitrate, and hexahydrate of uranyl nitrate ; (transition points at 37.33% UO(NO), 13.18% Sr(NO)\\/; sub 2\\/, and 5 UO(NO), 4.78%

  6. Uranyl Nitrate: 91Day Exposure and Recovery Studies in the Male New Zealand White Rabbit

    Microsoft Academic Search

    A. P. Gilman; M. A. Moss; D. C. Villeneuve; V. E. Secours; A. P. Yagminas; B. L. Tracy; J. M. Quinn; G. Long; V. E. Valli

    1998-01-01

    This study was undertaken to examine the reversibility of renal injury in the male New Zealand White rabbit subsequent to a 91-day exposure to uranyl nitrate (UN) in drinking water, followed by various recovery periods. Specific pathogen-free (SPF) animals were exposed for 91 days to UN in their drinking water (24 or 600 mg UN\\/L). Control groups were given municipal

  7. Adsorption of Uranyl Ions into Poly(Acrylamide?co?Acrylic Acid) Hydrogels Prepared by Gamma Irradiation

    Microsoft Academic Search

    Dilek ?olpan; Olgun Gven

    2005-01-01

    Acrylamide (AAm)\\/Acrylic Acid (AAc) copolymers have been prepared by gamma irradiation of binary mixtures at three different compositions where the acrylamide\\/acrylic acid mole ratios varied around 15, 20, and 30%. Threshold dose for 100% conversion of monomers into hydrogels was found to be 8.0kGy. Poly(Acrylamide?co?Acrylic Acid) (poly(AAm?co?AAc)) hydrogels have been considered for the removal of uranyl ions from aqueous solutions.

  8. Synthesis and crystal structure of supramolecular adduct of tetranuclear uranyl chloride aquacomplex with macrocyclic cavitand cucurbituril

    Microsoft Academic Search

    O. A. Gerasko; D. G. Samsonenko; A. A. Sharonova; A. V. Virovets; J. Lipkowski; V. P. Fedin

    2002-01-01

    Crystals of supramolecular compound {[(UO2)4O2Cl4(H2O)6](H2O?C36H36N24O12)}4H2O were obtained under conditions of hydrothermal synthesis from solutions of uranyl(vi) nitrate and cucurbituril in the presence of rubidium chloride. The crystal and molecular structure were determined by X-ray diffraction analysis.

  9. Recuperation of uranyl ions from effluents by means of microbiological collectors

    SciTech Connect

    Cecal, A.; Palamaru, I.; Humelnicu, D.; Goanta, M. [Al.I.Cuza Univ., Iasi (Romania). Faculty of Chemistry] [Al.I.Cuza Univ., Iasi (Romania). Faculty of Chemistry; Rudic, V.; Salaru, V.V. [Academy of Science, Kishinew (Moldova, Republic of). Inst. of Microbiology] [Academy of Science, Kishinew (Moldova, Republic of). Inst. of Microbiology; Gulea, A. [State Univ., Kishinew (Moldova, Republic of). Faculty of Chemistry] [State Univ., Kishinew (Moldova, Republic of). Faculty of Chemistry

    1997-12-31

    This paper deals with the study of bioaccumulation of uranyl ions (UO{sub 2}{sup 2+}) from industrial effluents, using microbiological collectors: Nostoc linkia sp., Tolipotrix sp., Spirulina sp., Porphyridium cruentum and also the glucide extract of P. cruentum. The values of retaining degree of UO{sub 2}{sup 2+} on the biomass, for several experimental conditions, were established between 14.22 and 91.99%.

  10. A comparative study of uranyl nitrate and cisplatin-induced renal failure in rat

    Microsoft Academic Search

    I. Mahmood; D. H. Waters

    1994-01-01

    SummaryRenal dysfunction can have substantial effects on the pharmacokinetics and pharmacodynamics of drugs. A wide variety of animal\\u000a models have been developed in an attempt to mimic conditions seen in human renal failure. In reality, no single animal model\\u000a would be completely satisfactory because the etiology and development of renal failure are diverse. During recent years injection\\u000a of uranyl nitrate

  11. Interplay of coordinative and supramolecular interactions in engineering unusual crystalline architectures of low-dimensional metalpamoate complexes under co-ligand intervention

    Microsoft Academic Search

    Miao Du; Cheng-Peng Li; Xiao-Jun Zhao; Qian Yu

    2007-01-01

    This work presents a systematic investigation on coordination chemistry of a pharmaceutical agent pamoic acid (H2PA), and also reveals the significant function of supramolecular interactions in managing the resultant crystalline networks with the incorporation of secondary co-ligands. Assemblies of pamoic acid with transition metal ions under similar conditions yield a series of eleven Mn II ,C u II ,Z n

  12. Stable five-coordinate silicon(IV) complexes with SiN4 X skeletons (X = S, Se, Te) and Si=X double bonds.

    PubMed

    Junold, Konstantin; Baus, Johannes A; Burschka, Christian; Auerhammer, Dominic; Tacke, Reinhold

    2012-12-14

    Silylenes: Reaction of the donor-stabilized silylene 1 with elemental sulfur, selenium, or tellurium led to the formation of 2?a-c [SiN(4)X skeletons (X = S, Se, Te)], the first stable five-coordinate silicon(IV) compounds with silicon-chalcogen double bonds (see figure). PMID:23172801

  13. Influence of coligands on the. eta. sup 1 -coordination mode of SO sub 2 in L sub 3 NiSO sub 2 complexes. A pseudopotential ab initio study

    SciTech Connect

    Reinhold, J.; Schueler, M. (Univ. of Leipzig (Germany)); Hoffmann, T.; Wenschuh, E. (Humboldt Univ., Berlin (Germany))

    1992-02-19

    In tris(phosphine)(sulfur dioxide)nickel(0) complexes the mode of {eta}{sup 1}-coordination of SO{sub 2} depends in a very sensitive way on the nature of the phosphine coligands, i.e., their electronic and steric influences. MO calculations on the pseudopotential ab initio level show that the experimental structure ({eta}{sup 1}-pyramidal vs {eta}{sup 1}-coplanar coordination of SO{sub 2}) is a consequence of various different and partially counteracting influences of the coligands. The recently found unusual {eta}{sup 1}-pyramidal mode as compared to the usual {eta}{sup 1}-coplanar one can be expected to be obtained by coligands which are small and have strong donor power as well.

  14. Water-Reflected 233U Uranyl Nitrate Solutions in Simple Geometry

    SciTech Connect

    Elam, K.R.

    2001-08-15

    A number of critical experiments involving {sup 233}U were performed in the Oak Ridge National Laboratory Building 9213 Critical Experiments Facility during the years 1952 and 1953. These experiments, reported in Reference 1, were directed toward determining bounding values for the minimum critical mass, minimum critical volume, and maximum safe pipe size of water-moderated solutions of {sup 233}U. Additional information on the critical experiments was found in the experimental logbooks. Two experiments utilizing uranyl nitrate (UO{sub 2}(NO{sub 3}){sub 2}) solutions in simple geometry are evaluated in this report. Experiment 37 is in a 10.4-inch diameter sphere, and Experiment 39 is in a 10-inch diameter cylinder. The {sup 233}U concentration ranges from 49 to 62 g {sup 233}U/l. Both experiments were reflected by at least 6 inches of water in all directions. Paraffin-reflected uranyl nitrate experiments, also reported in Reference 1, are evaluated elsewhere. Experiments with smaller paraffin reflected 5-, 6-, and 7.5-inch diameter cylinders are evaluated in U233-SOL-THERM-004. Experiments with paraffin reflected 8-, 8.5-, 9-, 10-, and 12-inch diameter cylinders are evaluated in U233-SOL-THERM-002. Later experiments with highly-enriched {sup 235}U uranyl fluoride solution in the same 10.4-inch diameter sphere are reported in HEU-SOL-THERM-010. Both experiments were judged acceptable for use as criticality-safety benchmark experiments.

  15. Noble Gas-Uranium Coordination and Intersystem Crossing for the CUO(Ne)x(Ng)n (Ng = Ar, Kr, Xe) Complexes in Solid Neon

    SciTech Connect

    Andrews, Lester; Liang, Binyong; Li, Jun; Bursten, Bruce E.

    2004-02-15

    Atomic uranium excited by laser ablation reacts with CO in excess neon to produce the novel CUO molecule, which forms weak complexes CUO(Ne)m with neon and stronger complexes CUO(Ne)x(Ng)n (Ng = Ar, Kr, Xe) when the heavier noble gas atoms are present. The heavier CUO(Ne)m-1(Ng) complexes are identified through the effects of CO isotopic and Ng substitution on the neon matrix infrared spectra and by comparison to DFT frequency calculations on model complexes CUO(Ng) (Ng = Ne, Ar, Kr, Xe). The U-C and U-O stretching frequencies of CUO(Ne)m-1(Ng) complexes are slightly red shifted from 1047 and 872 cm-1 frequencies for the 1Sigma+ CUO ground state neon complex, which identifies singlet ground state CUO(Ne)m-1(Ng) complexes in solid neon. The next singlet CUO(Ne)x(Ng)2 complexes in excess neon follow in like manner. However, stretching modes and the isotopic shifts of the higher CUO(Ne)x(Ng)n complex approach those of the pure argon matrix CUO(Ar)n complex, which characterizes triple t ground state complexes by comparison to DFT frequency calculations.

  16. Synergistic cytotoxicity and DNA strand breaks in cells and plasmid DNA exposed to uranyl acetate and ultraviolet radiation

    PubMed Central

    Wilson, Janice; Zuniga, Mary C.; Yazzie, Filbert; Stearns, Diane M.

    2015-01-01

    Depleted uranium (DU) has a chemical toxicity that is independent of its radioactivity. The purpose of this study was to explore the photoactivation of uranyl ion by ultraviolet (UV) radiation as a chemical mechanism of uranium genotoxicity. The ability of UVB (302 nm) and UVA (368 nm) radiation to photoactivate uranyl ion to produce single strand breaks was measured in pBR322 plasmid DNA, and the presence of adducts and apurinic/apyrimidinic sites that could be converted to single strand breaks by heat and piperidine was analyzed. Results showed that DNA lesions in plasmid DNA exposed to UVB- or UVA-activated DU were only slightly heat reactive, but were piperidine sensitive. The cytotoxicity of UVB-activated uranyl ion was measured in repair-proficient and repair-deficient Chinese hamster ovary cells and human keratinocyte HaCaT cells. The cytotoxicity of co-exposures of uranyl ion and UVB radiation was dependent on the order of exposure and was greater than co-exposures of arsenite and UVB radiation. Uranyl ion and UVB radiation were synergistically cytotoxic in cells, and cells exposed to photoactivated DU required different DNA repair pathways than cells exposed to non-photoactivated DU. This study contributes to our understanding of the DNA lesions formed by DU, as well as their repair. Results suggest that excitation of uranyl ion by UV radiation can provide a pathway for uranyl ion to be chemically genotoxic in populations with dermal exposures to uranium and UV radiation, which would make skin an overlooked target organ for uranium exposures. PMID:24832689

  17. Hydrothermal synthesis of uranyl squarates and squarate-oxalates: Hydrolysis trends and in situ oxalate formation

    SciTech Connect

    Rowland, Clare E.; Cahill, Christopher L.

    2010-01-01

    We report the synthesis of two uranyl squarates and two mixed-ligand uranyl squarate?oxalates from aqueous solutions under hydrothermal conditions. These products exhibit a range of uranyl building units from squarates with monomers in (UO{sub 2}){sub 2}(C{sub 4}O{sub 4}){sub 5}6NH{sub 4}4H{sub 2}O (1; a = 16.731(17) , b = 7.280(8) , c = 15.872(16) , ? = 113.294(16), monoclinic, P2{sub 1}/c) and chains in (UO{sub 2}){sub 2}(OH){sub 2}(H{sub 2}O){sub 2}(C{sub 4}O{sub 4}) (2; a = 12.909(5) , b = 8.400(3) , c = 10.322(4) , ? = 100.056(7), monoclinic, C2/c) to two squarate?oxalate polymorphs with dimers in (UO{sub 2}){sub 2}(OH)(C{sub 4}O{sub 4})(C{sub 2}O{sub 4})NH{sub 4}H{sub 2}O (3; a = 9.0601(7) , b = 15.7299(12) , c = 10.5108(8) , ? = 106.394(1), monoclinic, P2{sub 1}/n; and 4; a = 8.4469(6) , b = 7.7589(5) , c = 10.5257(7) , ? = 105.696(1), monoclinic, P2{sub 1}/m). The dominance at low pH of monomeric species and the increasing occurrence of oligomeric species with increasing pH suggests that uranyl hydrolysis, mUO{sub 2}{sup 2+} + NH{sub 2}O ? [(UO{sub 2}){sub m}(OH){sub n}]{sup 2m?n} + nH{sup +}, has a significant role in the identity of the inorganic building unit. Additional factors that influence product assembly include in situ hydrolysis of squaric acid to oxalic acid, dynamic metal to ligand concentration, and additional binding modes resulting from the introduction of oxalate anions. These points and the effects of uranyl hydrolysis with changing pH are discussed in the context of the compounds presented herein.

  18. Synthesis, spectral and magnetic studies of mono- and bi-nuclear metal complexes of a new bis(tridentate NO2) Schiff base ligand derived from 4,6-diacetylresorcinol and ethanolamine.

    PubMed

    Shebl, Magdy

    2009-07-15

    A new bis(tridentate NO2) Schiff base ligand, H(4)L, was prepared by the reaction of the bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) with ethanolamine. The ligand reacted with iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), cerium(III) and uranyl(VI) ions, in absence and in presence of LiOH, to yield mono- and bi-nuclear complexes with different coordinating sites. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. In absence of LiOH, mononuclear complexes (2, 3 and 5-9) as well as binuclear complexes (1 and 4) were obtained. In mononuclear complexes, the ligand acted as a neutral, mono- and di-basic/bi- and tetra-dentate ligand while in binuclear complexes (1 and 4), the ligand acted as a bis(mono- or di-basic/tridentate) ligand. On the other hand, in presence of LiOH, only binuclear complexes (10-15) were obtained in which the ligand acted as a bis(dibasic tridentate) ligand. The metal complexes exhibited different geometrical arrangements such as octahedral, tetrahedral, square planar, square pyramidal and pentagonal bipyramidal arrangements. PMID:19345138

  19. Synthesis, spectral and magnetic studies of mono- and bi-nuclear metal complexes of a new bis(tridentate NO2) Schiff base ligand derived from 4,6-diacetylresorcinol and ethanolamine

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy

    2009-07-01

    A new bis(tridentate NO2) Schiff base ligand, H4L, was prepared by the reaction of the bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) with ethanolamine. The ligand reacted with iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), cerium(III) and uranyl(VI) ions, in absence and in presence of LiOH, to yield mono- and bi-nuclear complexes with different coordinating sites. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. In absence of LiOH, mononuclear complexes (2, 3 and 5-9) as well as binuclear complexes (1 and 4) were obtained. In mononuclear complexes, the ligand acted as a neutral, mono- and di-basic/bi- and tetra-dentate ligand while in binuclear complexes (1 and 4), the ligand acted as a bis(mono- or di-basic/tridentate) ligand. On the other hand, in presence of LiOH, only binuclear complexes (10-15) were obtained in which the ligand acted as a bis(dibasic tridentate) ligand. The metal complexes exhibited different geometrical arrangements such as octahedral, tetrahedral, square planar, square pyramidal and pentagonal bipyramidal arrangements.

  20. Complex copper(II) fluorides . IX. Weberite-related NaCu3F7: The first fluoride with copper both in square planar and octahedral coordination

    Microsoft Academic Search

    Jean Renaudin; Marc Leblanc; Grard Ferey; Ariel de Kozak; Maurice Samoul

    1988-01-01

    NaCu3F7 is monoclinic (space group C2\\/c): a = 12.124(6) , b = 7.344(4) , c = 6.924(4) , beta = 120.59(4), Z = 4. The structure is refined from 751 independent reflections to R = 0.047 (Rw = 0.050). Copper ions occupy one square planar and two octahedral sites; sodium ions adopt a distorted cubic coordination. The three-dimensional network is

  1. Biladienones from the photooxidation of a meso-gem-disubstituted phlorin: crystal and molecular structures of the 3N + O coordinated nickel(II) and copper(II) complexes.

    PubMed

    Jeandon, C; Krattinger, B; Ruppert, R; Callot, H J

    2001-06-18

    The photooxidation of a meso-gem-disubstituted phlorin gave two isomeric biladienones in an equilibrium involving a Z-E double bond photoisomerism. The structures of these bile pigments were elucidated using NMR techniques and show terminal benzoyl and pyrrolone moieties. Complexation with divalent cations (nickel(II), copper (II)) gave stable compounds whose crystal and molecular structure could be determined by X-ray diffraction. The metal is coordinated with three pyrrole nitrogen atoms and one oxygen atom of a terminal benzoyl group. In the crystal, the molecules are arranged in pairs through hydrogen bonds between the free terminal pyrrolones. PMID:11399186

  2. Liquid-liquid extraction of metal ions by neutral phosphoramides. Part I. Extraction of uranyl ions from nitrate and sulphate media. Examination of extracted species by UV/VIS and {sup 31}P NMR spectroscopy

    SciTech Connect

    Rodehueser, L.; Rubini, P.R.; Bokolo, K.; Laakel, N.; Delpuech, J.J. [Universite Nancy (France)

    1992-09-01

    The extraction of uranyl nitrate and uranyl sulphate from aqueous media by the neutral chelating diphosphoramides CH{sub 3}-N[P(O)(NMe{sub 2}){sub 2}]{sub 2} (NIPA) and its less hydrophilic homologs R-N[P(O)(NMe{sub 2}){sub 2}]{sub 2} (R = -C{sub 12}H{sub 25} (ODIPA) or -C{sub 16}H{sub 33} (OHDIPA)), diluted in CH{sub 3}NO{sub 2} or toluene, has been studied. In the presence of HNO{sub 3}, NaNO{sub 3}, NaCl, and Na{sub 2}SO{sub 4} as salting-out agents, extraction is generally excellent. Some of the extracted complex species have been identified by comparing their {sup 31}P NMR and UV/vis spectra with those of pure complexes of known structure. The results are compared with extractions using tri-n-butyl phosphate (TBP) as the complexing agent. 20 refs., 9 figs., 4 tabs.

  3. A Novel Cobalt(II) Coordination Complex Constructed from H2Pyri and 4,4'-Bipy: Synthesis, Characterization and Bioactivity.

    PubMed

    Gao, Enjun; Zhao, Fuchen; Zhu, Mingchang; Wang, Meilin

    2015-01-01

    The new complex of {[Co(4,4'-Bipy)(H2O)4](Pyri)3H2O}n (4,4'-Bipy = 4,4'-bipyridyl, H2Pyri = 3,5- Pyridinedicarboxylic acid) was synthesized and characterized by IR, element analysis and X-ray single-crystal diffraction. The binding of the complex with extracted HeLa cells DNA was investigated by UV and fluorescence spectrum. Gel electrophoresis assay demonstrated the ability of the complex cleaving the extracted HC-DNA. The complex exhibited a higher cytotoxicity against tumor cells in vitro. Furthermore, the apoptotic tests indicated the complex had an apoptotic effect on HeLa cells. PMID:23574383

  4. Representations of world coordinates in FITS

    E-print Network

    Eric W. Greisen; Mark R. Calabretta

    2002-11-13

    The initial descriptions of the FITS format provided a simplified method for describing the physical coordinate values of the image pixels, but deliberately did not specify any of the detailed conventions required to convey the complexities of actual image coordinates. Building on conventions in wide use within astronomy, this paper proposes general extensions to the original methods for describing the world coordinates of FITS data. In subsequent papers, we apply these general conventions to the methods by which spherical coordinates may be projected onto a two-dimensional plane and to frequency/wavelength/velocity coordinates.

  5. Mononuclear thiocyanate containing nickel(II) and binuclear azido bridged nickel(II) complexes of N4-coordinate pyrazole based ligand: Syntheses, structures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Solanki, Ankita; Monfort, Montserrat; Kumar, Sujit Baran

    2013-10-01

    Two mononuclear nickel(II) complexes [NiL1(NCS)2] (1) and [NiL2(NCS)2] (2) and two azido bridged binuclear nickel(II) complexes [Ni(()2()2] (3) and [Ni(()2()2] (4), where L1, L2, L1? and L2? are N,N-diethyl-N?,N?-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1), N,N-bis((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2), N,N-diethyl-N?-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1?) and N-((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2?) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS- containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (?-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32 cm-1, respectively.

  6. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: synthesis, structural elucidation and dna binding properties of metal(II) complexes.

    PubMed

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-15

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M=Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, (1)H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.1410(5)M(-1), 1.810(5)M(-1), 6.710(4)M(-1) and 2.510(4)M(-1) respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand. PMID:24835939

  7. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: Synthesis, structural elucidation and DNA binding properties of metal(II) complexes

    NASA Astrophysics Data System (ADS)

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-01

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M = Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, 1H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14 105 M-1, 1.8 105 M-1, 6.7 104 M-1 and 2.5 104 M-1 respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

  8. Coordination chemistry of two heavy metals: I, Ligand preferences in lead(II) complexation, toward the development of therapeutic agents for lead poisoning: II, Plutonium solubility and speciation relevant to the environment

    SciTech Connect

    Neu, M.P. [Lawrence Berkeley Lab., CA (United States)

    1993-11-01

    The coordination chemistry and solution behavior of the toxic ions lead(II) and plutonium(IV, V, VI) have been investigated. The ligand pK{sub a}s and ligand-lead(II) stability constants of one hydroxamic acid and four thiohydroaxamic acids were determined. Solution thermodynamic results indicate that thiohydroxamic acids are more acidic and slightly better lead chelators than hydroxamates, e.g., N-methylthioaceto-hydroxamic acid, pK{sub a} = 5.94, log{beta}{sub 120} = 10.92; acetohydroxamic acid, pK{sub a} = 9.34, log{beta}{sub l20} = 9.52. The syntheses of lead complexes of two bulky hydroxamate ligands are presented. The X-ray crystal structures show the lead hydroxamates are di-bridged dimers with irregular five-coordinate geometry about the metal atom and a stereochemically active lone pair of electrons. Molecular orbital calculations of a lead hydroxamate and a highly symmetric pseudo octahedral lead complex were performed. The thermodynamic stability of plutonium(IV) complexes of the siderophore, desferrioxamine B (DFO), and two octadentate derivatives of DFO were investigated using competition spectrophotometric titrations. The stability constant measured for the plutonium(IV) complex of DFO-methylterephthalamide is log{beta}{sub 110} = 41.7. The solubility limited speciation of {sup 242}Pu as a function of time in near neutral carbonate solution was measured. Individual solutions of plutonium in a single oxidation state were added to individual solutions at pH = 6.0, T = 30.0, 1.93 mM dissolved carbonate, and sampled over intervals up to 150 days. Plutonium solubility was measured, and speciation was investigated using laser photoacoustic spectroscopy and chemical methods.

  9. Implementation and effectiveness of 'care navigation', coordinated management for people with complex chronic illness: rationale and methods of a randomised controlled

    PubMed Central

    2013-01-01

    Background Chronic illness is a significant driver of the global burden of disease and associated health care costs. People living with severe chronic illness are heavy users of acute hospital services; better coordination of their care could potentially improve health outcomes while reducing hospital use. The Care Navigation trial will evaluate an in-hospital coordinated care intervention on health service use and quality of life in chronically ill patients. Methods/Design A randomised controlled trial in 500 chronically ill patients presenting to the emergency department of a hospital in Western Sydney, Australia. Participants have three or more hospital admissions within a previous 12month period and either aged ?70years; or aged ?45years and of Aboriginal or Torres Strait Islander descent; or aged???16 with a diagnosis of a respiratory or cardiology related illness. Patients are randomised to either the coordinated care program (Care Navigation), or to usual care. The Care Navigation program consists of dedicated nurses who conduct patient risk assessments, oversee patient nursing while in hospital, and guide development of a care plan for the management of chronic illness after being discharged from hospital. These nurses also book community appointments and liaise with general practitioners. The main outcome variables are the number of emergency department re-presentations and hospital readmissions, and quality of life during a 24month follow-up. Secondary outcomes are length of hospital stay, mortality, time to first hospital re-admission, time to first emergency department re-presentation, patient satisfaction, adherence to prescribed medications, amount and type of in-hospital referrals made for consultations and diagnostic testing, and the number and type of community health referrals. A process evaluation and economic analysis will be conducted alongside the randomised trial. Discussion A trial of in-hospital care coordination may support recent evidence that engaging primary health services in care plans linked to multidisciplinary team support improves patient outcomes and reduces costs to the health system. This will inform local, national and international health policy. Trial registration Australia New Zealand Clinical Trials Registry ACTRN12609000554268 PMID:23642145

  10. Crystal structures of the NO and N2O4 sorption complexes of fully dehydrated fully Cd2+-exchanged zeolite X (FAU): coordination of neutral NO and N2O4 to Cd2+.

    PubMed

    Lee, Young Mi; Kim, Yang; Seff, Karl

    2005-03-24

    The structures of the nitric oxide and dinitrogen tetroxide sorption complexes of dehydrated fully Cd2+-exchanged zeolite X (FAU) have been determined using single-crystal X-ray diffraction in the cubic space group Fdm at 21(1) degrees C. Ion exchange was accomplished by allowing an aqueous stream 0.05 M in Cd2+ to flow past each crystal for 5 days. Each crystal was then dehydrated at 500 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 100 Torr of zeolitically dry NO or NO2/N2O4 gas. The structures were determined in these atmospheres. The unit cell constants at 21(1) degrees C are 24.877(2) A for the dark-yellow NO complex, |Cd46(NO)16|[Si100Al92O384]-FAU, and 24.735(2) A for the black N2O4 complex, |Cd46(N2O4)25.5|[Si100Al92O384]-FAU. The structure of the NO complex was refined to R1 = 0.072 and wR2 = 0.134. In this structure, Cd2+ ions occupy four crystallographic sites. Fifteen Cd2+ ions occupy site I (at the centers of the double 6-rings (D6Rs)), and one occupies site I' (in the sodalite cavity opposite a D6R). The remaining 30 Cd2+ ions occupy two different sites II (near 6-rings in the supercages): 16 coordinate to nitric oxide molecules and 14 do not. Sixteen NO molecules lie in the supercage where each interacts weakly with a Cd2+ ion: Cd-N = 2.57(22) A. The observed N-O bond distance is 1.28(25) A and Cd-N-O is 118(10) degrees. The structure of the N2O4 complex was refined to R1 = 0.084 and wR2 = 0.216. In this structure, Cd2+ ions occupy only three crystallographic sites. The 16 D6Rs per unit cell are filled with 11.5 Cd2+ ions at site I and 9 Cd2+ ions at site I': 11.5 + 9/2 = 16. The remaining 25.5 Cd2+ ions occupy site II where each coordinates at 2.43(8) A to a nitrogen atom of a N2O4 molecule. At the coordinating nitrogen atom, O-N-O is 147(10) degrees and the N-O bond lengths are 1.07(9) and 1.23(10) A. At the second nitrogen atom, O-N-O is 140(10) degrees, and the N-O bond lengths are 1.03(13) and 1.42(12) A. The imprecisely determined N-N bond length, 2.74(17) A, appears to be very much lengthened by coordination to Cd2+. The Cd-N-N angle is 144(10) degrees. This appears to be the first crystallographic report of the coordination of N2O4 to a cation. PMID:16863145

  11. Computer Simulation of Uranyl Uptake by the Rough Lipopolysaccharide Membrane of Pseudomonas aeruginosa

    SciTech Connect

    Lins, Roberto D.; Vorpagel, Erich R.; Guglielmi, Matteo; Straatsma, TP

    2008-01-01

    Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly non-symmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolisaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer-core.

  12. Uranyl nitrate-exposed rat alveolar macrophages cell death: influence of superoxide anion and TNF ? mediators.

    PubMed

    Orona, N S; Tasat, D R

    2012-06-15

    Uranium compounds are widely used in the nuclear fuel cycle, military and many other diverse industrial processes. Health risks associated with uranium exposure include nephrotoxicity, cancer, respiratory, and immune disorders. Macrophages present in body tissues are the main cell type involved in the internalization of uranium particles. To better understand the pathological effects associated with depleted uranium (DU) inhalation, we examined the metabolic activity, phagocytosis, genotoxicity and inflammation on DU-exposed rat alveolar macrophages (12.5-200 ?M). Stability and dissolution of DU could differ depending on the dissolvent and in turn alter its biological action. We dissolved DU in sodium bicarbonate (NaHCO? 100 mM) and in what we consider a more physiological vehicle resembling human internal media: sodium chloride (NaCl 0.9%). We demonstrate that uranyl nitrate in NaCl solubilizes, enters the cell, and elicits its cytotoxic effect similarly to when it is diluted in NaHCO?. We show that irrespective of the dissolvent employed, uranyl nitrate impairs cell metabolism, and at low doses induces both phagocytosis and generation of superoxide anion (O??). At high doses it provokes the secretion of TNF? and through all the range of doses tested, apoptosis. We herein suggest that at DU low doses O?? may act as the principal mediator of DNA damage while at higher doses the signaling pathway mediated by O?? may be blocked, prevailing damage to DNA by the TNF? route. The study of macrophage functions after uranyl nitrate treatment could provide insights into the pathophysiology of uranium-related diseases. PMID:22561334

  13. Biogeochemical changes induced in uranium mining waste pile samples by uranyl nitrate treatments under anaerobic conditions.

    PubMed

    Geissler, A; Merroun, M; Geipel, G; Reuther, H; Selenska-Pobell, S

    2009-06-01

    Response of the subsurface soil bacterial community of a uranium mining waste pile to treatments with uranyl nitrate over different periods of time was studied under anaerobic conditions. The fate of the added U(VI) without supplementation with electron donors was investigated as well. By using 16S rRNA gene retrieval, we demonstrated that incubation with uranyl nitrate for 4 weeks resulted in a strong reduction in and even disappearance of some of the most predominant bacterial groups of the original sample. Instead, a strong proliferation of denitrifying and uranium-resistant populations of Rahnella spp. from Gammaproteobacteria and of Firmicutes occurred. After longer incubations for 14 weeks with uranyl nitrate, bacterial diversity increased and populations intrinsic to the untreated samples such as Bacteroidetes and Deltaproteobacteria propagated and replaced the above-mentioned uranium-resistant groups. This indicated that U(VI) was immobilized. Mssbauer spectroscopic analysis revealed an increased Fe(III) reduction by increasing the incubation time from four to 14 weeks. This result signified that Fe(III) was used as an electron acceptor by the bacterial community established at the later stages of the treatment. X-ray absorption spectroscopic analysis demonstrated that no detectable amounts of U(VI) were reduced to U(IV) in the time frames of the performed experiments. The reason for this observation is possibly due to the low level of electron donors in the studied oligotrophic environment. Time-resolved laser-induced fluorescence spectroscopic analysis demonstrated that most of the added U(VI) was bound by organic or inorganic phosphate phases both of biotic origin. PMID:19476503

  14. Computer simulation of uranyl uptake by the rough lipopolysaccharide membrane of Pseudomonas aeruginosa.

    PubMed

    Lins, Roberto D; Vorpagel, Erich R; Guglielmi, Matteo; Straatsma, T P

    2008-01-01

    Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly nonsymmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolysaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions, and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer core. PMID:18067253

  15. Hepatitis C Virus NS2 Coordinates Virus Particle Assembly through Physical Interactions with the E1-E2 Glycoprotein and NS3-NS4A Enzyme Complexes ?

    PubMed Central

    Stapleford, Kenneth A.; Lindenbach, Brett D.

    2011-01-01

    The hepatitis C virus (HCV) NS2 protein is essential for particle assembly, but its function in this process is unknown. We previously identified critical genetic interactions between NS2 and the viral E1-E2 glycoprotein and NS3-NS4A enzyme complexes. Based on these data, we hypothesized that interactions between these viral proteins are essential for HCV particle assembly. To identify interaction partners of NS2, we developed methods to site-specifically biotinylate NS2 in vivo and affinity capture NS2-containing protein complexes from virus-producing cells with streptavidin magnetic beads. By using these methods, we confirmed that NS2 physically interacts with E1, E2, and NS3 but did not stably interact with viral core or NS5A proteins. We further characterized these protein complexes by blue native polyacrylamide gel electrophoresis and identified ?520-kDa and ?680-kDa complexes containing E2, NS2, and NS3. The formation of NS2 protein complexes was dependent on coexpression of the viral p7 protein and enhanced by cotranslation of viral proteins as a polyprotein. Further characterization indicated that the glycoprotein complex interacts with NS2 via E2, and the pattern of N-linked glycosylation on E1 and E2 suggested that these interactions occur in the early secretory pathway. Importantly, several mutations that inhibited virus assembly were shown to inhibit NS2 protein complex formation, and NS2 was essential for mediating the interaction between E2 and NS3. These studies demonstrate that NS2 plays a central organizing role in HCV particle assembly by bringing together viral structural and nonstructural proteins. PMID:21147927

  16. Elucidation of tetraboric acid with a new borate fundamental building block in a chiral uranyl fluoroborate.

    PubMed

    Wang, Shuao; Parker, T Gannon; Grant, Daniel J; Diwu, Juan; Alekseev, Evgeny V; Depmeier, Wulf; Gagliardi, Laura; Albrecht-Schmitt, Thomas E

    2012-11-01

    A new neutral borate species, H(2)B(4)O(7) (also known as tetraboric acid), with a one-dimensional chain structure, is found in the interlayer spacing in Rb(2)[(UO(2))(2)B(8)O(12)F(6)]H(2)B(4)O(7) (RbUBOF-2) derived from boric acid flux reaction of uranyl(VI) nitrate with RbBF(4). This new form of tetraboric acid possesses a novel borate fundamental building block with the symbol 4?:<3?>?. PMID:23088377

  17. A density functional study of the various forms of UN4O12 containing uranyl nitrate.

    PubMed

    Berard, Joel J; Shamov, Grigory A; Schreckenbach, Georg

    2007-10-25

    In this paper we report the computational results of a density functional study of 73 UN4O12 isomers containing uranyl nitrate, UO2(NO3)2, as a component. The isomers are grouped into three categories and 19 types. Forty-four isomers of 14 types are dinitrogen tetroxide adducts of uranyl nitrate, UO2(NO3)2.N2O4, 22 are nitrosonium salt adducts of uranyl nitrate, NO+UO2(NO3)3-, NO+UO2(NO3)2O(NO2)-, NO+UO2(NO3)2(ONOO)-, or (NO+)2UO2(NO3)2O22-, and 7 are bis(nitrogen dioxide) adducts of uranyl nitrate, UO2(NO3)2.2NO2. The 22 most stable isomers in solution, representing the 20 most stable gas-phase isomers, were selected for analysis. Of these selected structures only two categories and six types were represented. Structures, frequencies, gas-phase and solution energetics, atomic charges, dipole moments, and the bonding within the N2O4 unit and between NO+ and UO2(NO3)3- components have been analyzed in detail. On the basis of relative Gibbs free energy calculations five isomers (the N2O4 adducts a1, a2, and a3 and the nitrosonium salts b1 and b2) were identified as strong candidates to exist and possibly predominate in the gas phase, with a1 and a2 being the strongest candidates. Similarly, four isomers (a6, a5, a8, and a1, all of them N2O4 adducts) were identified as strong candidates to exist and possibly predominate in a nonaqueous solution of nitromethane/dinitrogen tetroxide. Of these, a6 was determined to be the most likely candidate to predominate in solution. The possibility of dissociation in solution has been addressed briefly. In addition, computational evidence for the existence of four new N2O4 isomers 20, 22, 27, and 28 in both the gas and the solution phases is presented for the first time. PMID:17915837

  18. Measurement of the electric hyperfine coupling constant P/k in a uranyl rubidium nitrate crystal

    SciTech Connect

    Tambovtsev, D. I., E-mail: ditam@ippe.r [Institute of Physics and Power Engineering (Russian Federation)

    2007-11-15

    New investigations with nuclei oriented in a single-crystal sample of uranyl rubidium nitrate required refining values of the constants that determine the degree of orientation. The results obtained from new measurements of the angular anisotropy of the emission of alpha particles from aligned {sup 233}U nuclei are presented in this article. A method for experimental-data treatment is described. New values of the hyperfine coupling constants for {sup 233}U and {sup 235}U are obtained with much smaller uncertainties.

  19. Structure-Property Relationships in Lithium, Silver, and Cesium Uranyl Borates

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Liu, Guokui; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-01-01

    Four new uranyl borates, Li[UO{sub 2}B{sub 5}O{sub 9}]H{sub 2}O (LiUBO-1), Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] (AgUBO-1), ?-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-1), and ?-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-2) were synthesized via the reaction of uranyl nitrate with a large excess of molten boric acid in the presence of lithium, silver, or cesium nitrate. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers, and are directed approximately perpendicular to the sheets. In Li[(UO{sub 2})B{sub 5}O{sub 9}]H{sub 2}O, the additional BO{sub 3} triangles connect these sheets together to form a three-dimensional framework structure. Li[UO{sub 2})B{sub 5}O{sub 9}]H{sub 2}O and ?-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] adopt noncentrosymmetric structures, while Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] and ?-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] are centrosymmetric. Li[(UO{sub 2})B{sub 5}O{sub 9}]H{sub 2}O, which can be obtained as pure phase, displays second-harmonic generation of 532 nm light from 1064 nm light. Topological relationships of all actinyl borates are developed.

  20. Luminescent iridium(III) complexes with N^C^N-coordinated terdentate ligands: dual tuning of the emission energy and application to organic light-emitting devices.

    PubMed

    Brulatti, Pierpaolo; Gildea, Richard J; Howard, Judith A K; Fattori, Valeria; Cocchi, Massimo; Williams, J A Gareth

    2012-03-19

    A family of complexes (1a-3a and 1b-3b) was prepared, having the structure Ir(N^C^N)(N^C)Cl. Here, N^C(?)N represents a terdentate, cyclometallating ligand derived from 1,3-di(2-pyridyl)benzene incorporating CH(3) (1a,b), F (2a,b), or CF(3) (3a,b) substituents at the 4 and 6 positions of the benzene ring, and N^C is 2-phenylpyridine (series a) or 2-(2,4-difluorophenyl)pyridine (series b). The complexes are formed using a stepwise procedure that relies on the initial introduction of the terdentate ligand to form a dichloro-bridged iridium dimer, followed by cleavage with the N^C ligand. (1)H NMR spectroscopy reveals that the isomer that is exclusively formed in each case is that in which the pyridyl ring of the N^C ligand is trans to the cyclometallating aryl ring of the N^C^N ligand. This conclusion is unequivocally confirmed by X-ray diffraction analysis for two of the complexes (1b and 3a). All of the complexes are highly luminescent in degassed solution at room temperature, emitting in the green (1a,b), blue-green (2a,b), and orange-red (3a,b) regions. The bidentate ligand offers independent fine-tuning of the emission energy: for each pair, the "b" complex is blue-shifted relative to the analogous "a" complex. These trends in the excited-state energies are rationalized in terms of the relative magnitudes of the effects of the substituents on the highest occupied and lowest unoccupied orbitals, convincingly supported by time-dependent density functional theory (TD-DFT) calculations. Luminescence quantum yields are high, up to 0.7 in solution and close to unity in a PMMA matrix for the green-emitting complexes. Organic light emitting devices (OLEDs) employing this family of complexes as phosphorescent emitters have been prepared. They display high efficiencies, at least comparable, and in some cases superior, to similar devices using the well-known tris-bidentate complexes such as fac-Ir(ppy)(3). The combination of terdentate and bidentate ligands is seen to offer a versatile approach to tuning of the photophysical properties of iridium-based emitters for such applications. PMID:22400487