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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. Variable Denticity in Carboxylate Binding to the Uranyl Coordination Complexes

    SciTech Connect

    Groenewold, G. S.; De Jong, Wibe A.; Oomens, Jos; Van Stipdonk, Michael J.

    2010-05-01

    Tris-carboxylate complexes of the uranyl [UO2]2+ cation with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transformion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetatouranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric -CO2 stretches of both the monodentate and bidentate acetate, CH3 bending and umbrella vibrations, and a uranyl O-U-O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate, and two bidentate benzoate ligands.

  3. Variable Denticity in Carboxylate Binding to the Uranyl Coordination Complexes

    SciTech Connect

    G. S. Groenewold; W. A. de Jong; J. Oomens; M. J. van Stipdonk

    2010-05-01

    Tris-carboxylate complexes of the uranyl [UO2]2+ cation with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetatouranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of a symmetric and antisymmetric 朇O2 stretches of both the monodentate and bidentate acetate, CH3 bending and umbrella vibrations, and a uranyl OUO asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate, and two bidentate benzoate ligand.

  4. 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

  5. Roles of Acetone and Diacetone Alcohol in Coordination and Dissociation Reactions of Uranyl Complexes

    SciTech Connect

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

    2012-12-03

    Combined collision-induced dissociation mass-spectrometry experiments and DFT calculations were employed to elucidate the molecular structure of "hypercoordinated" species and the energetics of water-elimination reactions of uranyl acetone complexes observed in earlier work (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). It is shown that the "hypercoordinated" species contain diacetone alcohol ligands bonded in either bidentate or monodentate fashion, which are indistinguishable from (acetone)2 in mass spectrometry. Calculations confirm that four diacetone ligands can form stable complexes, but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Diacetone alcohol ligands are shown to form mesityl oxide ligands and alkoxide species through the elimination of water, providing an explanation for the observed water-elimination reactions.

  6. On the Formation of "Hypercoordinated" Uranyl Complexes

    SciTech Connect

    Schoendorff, George E.; De Jong, Wibe A.; van Stipdonk, Michael J.; Gibson, John K.; Rios, Daniel; Gordon, Mark S.; Windus, Theresa L.

    2011-09-05

    Recent gas phase experimental studies suggest the presence of hypercoordinated uranyl complexes. Coordination of acetone (Ace) to uranyl to form hypercoordinated species is examined using density functional theory (DFT) with a range of functionals and second order perturbation theory (MP2). Complexes with up to eight acetones were studied. It is shown that no more than six acetones can bind directly to uranium and that the observed uranyl complexes are not hypercoordinated.

  7. 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)].

  8. Density Functional Studies on the Complexation and Spectroscopy of Uranyl Ligated with Acetonitrile and Acetone Derivatives

    SciTech Connect

    Schoendorff, George E.; Windus, Theresa L.; De Jong, Wibe A.

    2009-12-12

    The coordination of nitrile (acetonitrile, propionitrile, and benzonitrile) and carbonyl (formaldehyde, ethanal, and acetone) ligands to the uranyl dication (UO22+) has been examined using density functional theory (DFT) utilizing relativistic effective core potentials (RECPs). Complexes containing up to six ligands have been modeled for all ligands except formaldehyde, for which no minimum could be found. A comparison of relative binding energies indicates that five coordinate complexes are predominant while a six coordinate complex involving propionitrile ligands might be possible. Additionally, the relative binding energy and the weakening of the uranyl bond is related to the size of the ligand and, in general, nitriles bind more strongly to uranyl than carbonyls.

  9. LUMINESCENCE SPECTRA OF THE URANYL ION IN TWO GEOMETRICALLY SIMILAR COORDINATION ENVIRONMENTS: URANYL NITRATE HEXAHYDRATE AND DI-{mu}-AQUO-BIS (DIOXODINITRA-TOURANIUM(VI) DI-IMIDAZOLE

    SciTech Connect

    Brittain, Harry G.; Perry, Dale L.

    1980-02-01

    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~~-aquo-bis(dioxodinitratouranium(VI)) di-imidazole (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 geometries is that the water molecules are terminal in the UNH complex and bridging in the UNI complex. The uranium-uranium "bond" distance in the UNI complex is 3.93 A. At room temperature, the emission spectra of the two compounds are essentially identical, but significant differences appear upon cooling to 77癒. Vibronic structure is observed in the crystal of the UNI complex b4t not in the crystal of uranyl nitrate hexahydrate; this implies that the geom~try of the uranyl ion in the two excited states is somewhat different. An energy level sequence is presented in which the various emission lines arise from a slightly split excited state (splitting approximately 80-85 cm-1) to several vibrational levels of the ground electronic manifold. The energy spacing of the ground vibrational levels (approximately 860 cm-1) was found to vary when changing crystal systems.

  10. Uranyl oxo activation and functionalization by metal cation coordination

    NASA Astrophysics Data System (ADS)

    Arnold, Polly L.; P閏harman, Anne-Fr閐閞ique; Hollis, Emmalina; Yahia, Ahmed; Maron, Laurent; Parsons, Simon; Love, Jason B.

    2010-12-01

    The oxo groups in the uranyl ion [UO2]2+-one of many oxo cations formed by metals from across the periodic table-are particularly inert, which explains the dominance of this ion in the laboratory and its persistence as an environmental contaminant. In contrast, transition metal oxo (M=O) compounds can be highly reactive and carry out difficult reactions such as the oxygenation of hydrocarbons. Here we show how the sequential addition of a lithium metal base to the uranyl ion constrained in a `Pacman' environment results in lithium coordination to the U=O bonds and single-electron reduction. This reaction depends on the nature and stoichiometry of the lithium reagent and suggests that competing reduction and C-H bond activation reactions are occurring.

  11. The gas-phase bis-uranyl nitrate complex [(UO2)(2)(NO3)(5)](-): infrared spectrum and structure

    SciTech Connect

    Gary S. Groenewold; Michael J. van Stipdonk; Jos Oomens; Wibe de Jong; Michael E. McIlwain

    2011-12-01

    The infrared spectrum of the bis-uranyl nitrate complex [(UO{sub 2}){sub 2}(NO{sub 3}){sub 5}]{sup -} was measured in the gas phase using multiple photon dissociation (IRMPD). Intense absorptions corresponding to the nitrate symmetric and asymmetric vibrations, and the uranyl asymmetric vibration were observed. The nitrate nu3 vibrations indicate the presence of nitrate in a bridging configuration bound to both uranyl cations, and probably two distinct pendant nitrates in the complex. The coordination environment of the nitrate ligands and the uranyl cations were compared to those in the mono-uranyl complex. Overall, the uranyl cation is more loosely coordinated in the bis-uranyl complex [(UO{sub 2}){sub 2}(NO{sub 3}){sub 5}]{sup -} compared to the mono-complex [UO{sub 2}(NO{sub 3}){sub 3}]{sup -}, as indicated by a higher O-U-O asymmetric stretching (nu3) frequency. However, the pendant nitrate ligands are more strongly bound in the bis-complex than they are in the mono-uranyl complex, as indicated by the {nu}{sub 3} frequencies of the pendant nitrate, which are split into nitrosyl and O-N-O vibrations as a result of bidentate coordination. These phenomena are consistent with lower electron density donation per uranyl by the nitrate bridging two uranyl centers compared to that of a pendant nitrate in the mono-uranyl complex. The structure was calculated using density functional theory (B3LYP functional), which produced a structure in which the two uranyl molecules bridged by a single nitrate coordinated in a bis-bidentate fashion. Each uranyl molecule was coordinated by two pendant nitrate ligands. The corresponding vibrational spectrum was in excellent agreement with the IRMPD measurement, confirming the structural assignment.

  12. The gas-phase bis-uranyl nitrate complex [(UO2)2(NO3)5]-: infrared spectrum and structure

    SciTech Connect

    Groenewold, G. S.; van Stipdonk, Michael J.; Oomens, Jos; De Jong, Wibe A.; McIIwain, Michael E.

    2011-12-01

    The infrared spectrum of the bis-uranyl nitrate complex [(UO2)2(NO3)5]- was measured in the gas phase using multiple photon dissociation (IRMPD). Intense absorptions corresponding to the nitrate symmetric and asymmetric vibrations, and the uranyl asymmetric vibration were observed. The nitrate v3 vibrations indicate the presence of nitrate in a bridging configuration bound to both uranyl cations, and probably two distinct pendant nitrates in the complex. The coordination environment of the nitrate ligands and the uranyl cations were compared to those in the mono-uranyl complex. Overall, the uranyl cation is more loosely coordinated in the bis-uranyl complex [(UO2)2(NO3)5]- compared to the mono-complex [UO2(NO3)3]-, as indicated by a higher O-U-O asymmetric stretching (v3) frequency. However, the pendant nitrate ligands are more strongly bound in the bis-complex than they are in the mono-uranyl complex, as indicated by the v3 frequencies of the pendant nitrate, which are split into nitrosyl and O-N-O vibrations as a result of bidentate coordination. These phenomena are consistent with lower electron density donation per uranyl by the nitrate bridging two uranyl centers compared to that of a pendant nitrate in the mono-uranyl complex. The lowest energy structure predicted by density functional theory (B3LYP functional) calculations was one in which the two uranyl molecules bridged by a single nitrate coordinated in a bis-bidentate fashion. Each uranyl molecule was coordinated by two pendant nitrate ligands. The corresponding vibrational spectrum was in excellent agreement with the IRMPD measurement, confirming the structural assignment.

  13. Extraction and coordination studies of a carbonyl-phosphine oxide scorpionate ligand with uranyl and lanthanide(iii) nitrates: structural, spectroscopic and DFT characterization of the complexes.

    PubMed

    Matveeva, Anna G; Vologzhanina, Anna V; Goryunov, Evgenii I; Aysin, Rinat R; Pasechnik, Margarita P; Matveev, Sergey V; Godovikov, Ivan A; Safiulina, Alfiya M; Brel, Valery K

    2016-03-15

    Hybrid scorpionate ligand (OPPh2)2CHCH2C(O)Me () was synthesized and characterized by spectroscopic methods and X-ray diffraction. The selected coordination chemistry of with UO2(NO3)2 and Ln(NO3)3 (Ln = La, Nd, Lu) has been evaluated. The isolated mono- and binuclear complexes, namely, [UO2(NO3)2] (), [{UO2(NO3)}2(渭2-O2)]路EtOH (), [La(NO3)32]路2.33MeCN (), [Nd(NO3)32]路3MeCN (), [Nd(NO3)22](+)路(NO3)(-)路EtOH () and [Lu(NO3)32] () have been characterized by IR spectroscopy and elemental analysis. Single-crystal X-ray structures have been determined for complexes . Intramolecular intraligand 蟺-stacking interactions between two phenyl fragments of the coordinated ligand(s) were observed in all complexes . The 蟺-stacking interaction energy was estimated from Bader's AIM theory calculations performed at the DFT level. Solution properties have been examined using IR and multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopy in CD3CN and CDCl3. Coordination modes of vary with the coordination polyhedron of the metal and solvent nature showing many coordination modes: P(O),P(O), P(O),P(O),C(O), P(O),C(O), and P(O). Preliminary extraction studies of U(vi) and Ln(iii) (Ln = La, Nd, Ho, Yb) from 3.75 M HNO3 into CHCl3 show that scorpionate extracts f-block elements (especially uranium) better than its unmodified prototype (OPPh2)2CH2. PMID:26888745

  14. 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

  15. Series of mixed uranyl-lanthanide (Ce, Nd) organic coordination polymers with aromatic polycarboxylates linkers.

    PubMed

    Mihalcea, Ionut; Volkringer, Christophe; Henry, Natacha; Loiseau, Thierry

    2012-09-17

    Three series of mixed uranyl-lanthanide (Ce or Nd) carboxylate coordination polymers have been successfully synthesized by means of a hydrothermal route using either conventional or microwave heating methods. These compounds have been prepared from mixtures of uranyl nitrate, lanthanide nitrate together with phthalic acid (1,2), pyromellitic acid (3,4), or mellitic acid (5,6) in aqueous solution. The X-ray diffraction (XRD) single-crystal revealed that the phthalate complex (UO(2))(4)O(2)Ln(H(2)O)(7)(1,2-bdc)(4)種H(4)穢H(2)O (Ln = Ce(1), Nd(2); x = 1 for 1, x = 0 for 2), is based on the connection of tetranuclear uranyl-centered building blocks linked to discrete monomeric units LnO(2)(H(2)O)(7) via the organic species to generate infinite chains, intercalated by free ammonium cations. The pyromellitate phase (UO(2))(3)Ln(2)(H(2)O)(12)(btec)(3)5H(2)O (Ce(3), Nd(4)) contains layers of monomeric uranyl-centered hexagonal and pentagonal bipyramids linked via the carboxylate arms of the organic molecules. The three-dimensionality of the structure is ensured by the connection of remaining free carboxylate groups with isolated monomeric units LnO(2)(H(2)O)(7). The network of the third series (UO(2))(2)(OH)Ln(H(2)O)(7)(mel)5H(2)O (Ce(5), Nd(6)) is built up from dinuclear uranyl units forming layers through connection with the mellitate ligands, which are further linked to each other through discrete monomers LnO(3)(H(2)O)(6). The thermal decomposition of the various coordination complexes led to the formation of mixed uranium-lanthanide oxide, with the fluorite-type structure at 1500 癈 (for 1, 2) or 1400 癈 for 3-6. Expected U/Ln ratio from the crystal structures were observed for compounds 1-6. PMID:22931214

  16. EXAFS determinations of uranium structures: The uranyl ion complexed with tartaric, citric, and malic acids

    SciTech Connect

    Allen, P.G.; Shuh, D.K.; Bucher, J.J.

    1996-01-31

    Studies of the coordination chemistry of uranium in aqueous solutions are increasingly important for understanding the behavior of uranium in the environment. Actinide speciation information is essential for assessing and developing long-term strategies addressing problems such as migration in nuclear waste repositories or improvements in the processing of nuclear waste and materials. Relative to the latter, one method for removing uranium contamination from soils involves extraction using a chelating agent such as Tiron, or citrate. These types of extractants are quite efficient at binding the uranyl ion and thus are suitable for removing uranium contamination when it is in the hexavalent uranyl ion form. Martell et al. and Markovits et al. have published a series of articles detailing the complexation of the uranyl ion with tartaric, malic, and citric acids as a function of pH. Using the functional dependencies of potentiometric titration results, they showed that, in the pH range 2-4, the uranyl ion forms a 2:2 dimeric species, (UO{sub 2}){sub 2-} (L){sub 2}, where L = tartrate, malate, or citrate ligands. The authors have reinvestigated the solution structures of the uranyl complexes formed in these systems with the structural technique extended X-ray absorption fine-structure (EXAFS) spectroscopy.

  17. 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

  18. 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

  19. Gas Phase Uranyl Activation: Formation of a Uranium Nitrosyl Complex from Uranyl Azide

    SciTech Connect

    Gong, Yu; De Jong, Wibe A.; Gibson, John K.

    2015-05-13

    Activation of the oxo bond of uranyl, UO22+, was achieved by collision induced dissociation (CID) of UO2(N3)Cl2鈥 in a quadrupole ion trap mass spectrometer. The gas phase complex UO2(N3)Cl2鈥 was produced by electrospray ionization of solutions of UO2Cl2 and NaN3. CID of UO2(N3)Cl2鈥 resulted in the loss of N2 to form UO(NO)Cl2鈥, in which the 鈥渋nert鈥 uranyl oxo bond has been activated. Formation of UO2Cl2鈥 via N3 loss was also observed. Density functional theory computations predict that the UO(NO)Cl2鈥 complex has nonplanar Cs symmetry and a singlet ground state. Analysis of the bonding of the UO(NO)Cl2鈥 complex shows that the side-on bonded NO moiety can be considered as NO3鈥, suggesting a formal oxidation state of U(VI). Activation of the uranyl oxo bond in UO2(N3)Cl2鈥 to form UO(NO)Cl2鈥 and N2 was computed to be endothermic by 169 kJ/mol, which is energetically more favorable than formation of NUOCl2鈥 and UO2Cl2鈥. The observation of UO2Cl2鈥 during CID is most likely due to the absence of an energy barrier for neutral ligand loss.

  20. 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

  1. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    DOE PAGESBeta

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

    2015-04-02

    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 also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ 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 values ranging from 0more聽禄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 chelate capability to uranyl.芦聽less

  2. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    SciTech Connect

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

    2015-04-02

    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 also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ 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 chelate capability to uranyl.

  3. Correlation between stabilities of uranyl ion complexes with various monocarboxylic acids and Hammett-Taft substituent constants

    SciTech Connect

    Poluektov, N.S.; Perfil'ev, V.A.; Meshkova, S.B.; Mishchenko, V.T.

    1987-01-01

    A correlation has been observed between the stabilities of uranyl ion complexes (1:1 composition) and the substituent inductive constants in formic and acetic acid derivatives. For substituents which are not directly involved in couples formation the parameters of the Hammett-Taft equation log K/sub 1/ = A + B have the following values: A = 1.311, B = -2.360. For substituents which form a coordination bond with the uranyl ion, A = 7.0077 and B = - 17.321. In the case of complexes formed between the uranyl ion and salicylic acid and its derivatives, there is a correlation between complex stability and sigma/sub m/ and sigma/sub p/ substituent constants for the meta- and para-positions, respectively (A = 12.72, B = -4.41).

  4. 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.

  5. Complex nanoscale cage clusters built from uranyl polyhedra and phosphate tetrahedra

    SciTech Connect

    Unruh, Daniel K.; Ling, Jie; Qiu, Jie; Pressprich, Laura; Baranay, Melissa; Ward, Matthew; Burns, Peter C.

    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.

  6. Experimental and theoretical approaches to redox innocence of ligands in uranyl complexes: what is formal oxidation state of uranium in reductant of uranyl(VI)?

    PubMed

    Takao, Koichiro; Tsushima, Satoru; Ogura, Toshinari; Tsubomura, Taro; Ikeda, Yasuhisa

    2014-06-01

    Redox behavior of [UO2(gha)DMSO](-)/UO2(gha)DMSO couple (gha = glyoxal bis(2-hydroxanil)ate, DMSO = dimethyl sulfoxide) in DMSO solution was investigated by cyclic voltammetry and UV-vis-NIR spectroelectrochemical technique, as well as density functional theory (DFT) calculations. [UO2(gha)DMSO](-) was found to be formed via one-electron reduction of UO2(gha)DMSO without any successive reactions. The observed absorption spectrum of [UO2(gha)DMSO](-), however, has clearly different characteristics from those of uranyl(V) complexes reported so far. Detailed analysis of molecular orbitals and spin density of the redox couple showed that the gha(2-) ligand in UO2(gha)DMSO is reduced to gha(鈥3-) to give [UO2(gha)DMSO](-) and the formal oxidation state of U remains unchanged from +6. In contrast, the additional DFT calculations confirmed that the redox reaction certainly occurs at the U center in other uranyl(V/VI) redox couples we found previously. The noninnocence of the Schiff base ligand in the [UO2(gha)DMSO](-)/UO2(gha)DMSO redox couple is due to the lower energy level of LUMO in this ligand relative to those of U 5f orbitals. This is the first example of the noninnocent ligand system in the coordination chemistry of uranyl(VI). PMID:24848497

  7. Complex formation between uranyl and various thiosemicarbazide derivatives

    SciTech Connect

    Chuguryan, D.G.; Dzyubenko, V.I.

    1987-01-01

    Complex formation between hexavalent uranium and salicylaldehyde thiosemicarbazone (H/sub 2/L), salicylaldehyde S-methyl-isothiosemicarbazone (H/sub 2/Q), S-methyl-N/sub 1/,N/sub 4/-bis(salicylidene)isothiosemicarbazide(H/sub 2/Z), and thiosemicarbazidodiacetic acid (H/sub 2/R) has been studied spectrophotometrically in solution. Stability constants for complexes having the composition UO/sub 2/A have been calculated. Solid uranyl derivatives having the composition UO/sub 2/L x 2H/sub 2/O, UO/sub 2/Q x 2H/sub 2/O, UO/sub 2/Z x 2H/sub 2/O, and UO/sub 2/R x 2H/sub 2/O have been obtained. These derivatives were isolated and their IR spectroscopic behavior and thermal properties were investigated.

  8. 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

  9. Uranyl sensitization of samarium (III) luminescence in a two-dimensional coordination polymer

    SciTech Connect

    Knope, Karah E.; de Lill, Daniel T.; Rowland, Clare E.; Cantos, Paula M.; de Bettencourt-Dias, Ana; Cahill, Christopher L.

    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.

  10. 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.

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

    SciTech Connect

    Kelly, Shelly D; Kemner, Kenneth M; Brooks, Scott C

    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.

  12. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    SciTech Connect

    Park, Sang-Won; Leckie, J.O.; Siegel, M.D.

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption.

  13. 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.

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

    PubMed

    Thu茅ry, Pierre; Rivi猫re, 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)]路1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]路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]路0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]路0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]路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

  15. 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.

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

    PubMed

    Szigethy, G閦a; 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

  17. Construction of Uranyl Selective Electrode Based on Complex of Uranyl Ion with New Ligand Carboxybenzotriazole in PVC Matrix Membrane

    NASA Astrophysics Data System (ADS)

    Abu-Dalo, M. A.; Al-Rawashdeh, N. A. F.; Al-Mheidat, I. R.; Nassory, N. S.

    2015-10-01

    In the present study uranyl selective electrodes in polyvinyl chloride (PVC) matrix membrane were prepared based on a complex of uranyl ion (UO2) with carboxybenzotriazole (CBT) as ligand. The effect of the nature of plasticizer in PVC matrix were evaluated using three different plasticizers, these are dibutyl phthalate (DBP), dioctyl phthalate (DOP) and bis(2-ethylhexyl) sebacate (BHS). The results of this study indicated that the best plasticizer could be used is the DBP, which may be attributed to its lowest viscosity value compared to DOP and BHS. The electrodes with DBP as plasticizer exhibits a Nernstian response with a slope of 28.0 mV/ decade, over a wide range of concentration from 3.0脳10-5-6.0脳10-2 M and a detection limit of 4.0脳10-6 M. It can be used in the pH range of 4.0-10.0 with a response time of less than 10 s for DBP and 25 s for both DOP and BHS. The effects of ions interferences on the electrode response were evaluated. The di- and tri-valent cations were found to interfere less than univalent cations, which was attributed to the high diffusion and the exchange rate between the univalent ions and the uranyl ion solution. The electrodes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron microscopy (SEM). The results of the standard addition method were satisfactory with errors less than 7%. The developed electrode was found to be fast, sensitive and reliable indicated its potential use in measuring the uranly ion concentration in the field.

  18. Formation of bare UO2(2+) and NUO(+) by fragmentation of gas-phase uranyl-acetonitrile complexes.

    PubMed

    Van Stipdonk, Michael J; Michelini, Maria del Carmen; Plaviak, Alexandra; Martin, Dean; Gibson, John K

    2014-09-11

    In a prior study [Van Stipdonk; et al. J. Phys. Chem. A 2006, 110, 959-970], electrospray ionization (ESI) was used to generate doubly charged complex ions composed of the uranyl ion and acetonitrile (acn) ligands. The complexes, general formula [UO2(acn)n](2+), n = 0-5, were isolated in an 3-D quadrupole ion-trap mass spectrometer to probe intrinsic reactions with H2O. Two general reaction pathways were observed: (a) the direct addition of one or more H2O ligands to the doubly charged complexes and (b) charge-exchange reactions. For the former, the intrinsic tendency to add H2O was dependent on the number and type of nitrile ligand. For the latter, charge exchange involved primarily the formation of uranyl hydroxide, [UO2OH](+), presumably via a collision with gas-phase H2O and the elimination of a protonated nitrile ligand. Examination of general ion fragmentation patterns by collision-induced dissociation, however, was hindered by the pronounced tendency to generate hydrated species. In an update to this story, we have revisited the fragmentation of uranyl-acetonitrile complexes in a linear ion-trap (LIT) mass spectrometer. Lower partial pressures of adventitious H2O in the LIT (compared to the 3-D ion trap used in our previous study) minimized adduct formation and allowed access to lower uranyl coordination numbers than previously possible. We have now been able to investigate the fragmentation behavior of these complex ions completely, with a focus on tendency to undergo ligand elimination versus charge reduction reactions. CID can be used to drive ligand elimination to completion to furnish the bare uranyl dication, UO2(2+). In addition, fragmentation of [UO2(acn)](2+) generated [UO2(NC)](+), which subsequently fragmented to furnish NUO(+). Formation of the nitrido by transfer of N from cyanide was confirmed using precursors labeled with (15)N. The observed formation of [UO2(NC)](+) and NUO(+) was modeled by density functional theory. PMID:25121574

  19. Theoretical study of the coordination behavior of formate and formamidoximate with dioxovanadium(V) cation: implications for selectivity towards uranyl.

    PubMed

    Mehio, Nada; Johnson, J Casey; Dai, Sheng; Bryantsev, Vyacheslav S

    2015-12-21

    Poly(acrylamidoxime)-based fibers bearing random mixtures of carboxylate and amidoxime groups are the most widely utilized materials for extracting uranium from seawater. However, the competition between uranyl (UO2(2+)) and vanadium ions poses a significant challenge to the industrial mining of uranium from seawater using the current generation of adsorbents. To design more selective adsorbents, a detailed understanding of how major competing ions interact with carboxylate and amidoxime ligands is required. In this work, we employ density functional theory (DFT) and wave-function methods to investigate potential binding motifs of the dioxovanadium ion, VO2(+), with water, formate, and formamidoximate ligands. Employing higher level of theory calculations (CCSD(T)) resolve the existing controversy between the experimental results and previous DFT calculations for the structure of the hydrated VO2(+) ion. Consistent with the EXAFS data, CCSD(T) calculations predict higher stability of the distorted octahedral geometry of VO2(+)(H2O)4 compared to the five-coordinate complex with a single water molecule in the second hydration shell, while all seven tested DFT methods yield the reverse stability of the two conformations. Analysis of the relative stabilities of formate-VO2(+) complexes indicates that both monodentate and bidentate forms may coexist in thermodynamic equilibrium in solution. Investigations of VO2(+) coordination with the formamidoximate anion has revealed the existence of seven possible binding motifs, four of which are within 鈭4.0 kcal mol(-1) of each other. Calculations establish that the most stable binding motif entails the coordination of oxime oxygen and amide nitrogen atoms via a tautomeric rearrangement of amidoxime to imino hydroxylamine. The difference in the most stable VO2(+) and UO2(2+) binding conformation has important implications for the design of more selective UO2(2+) ligands. PMID:26559445

  20. A New Form of Triple-Stranded Helicate Found in Uranyl Complexes of Aliphatic ?,?-Dicarboxylates.

    PubMed

    Thu閞y, Pierre; Harrowfield, Jack

    2015-11-16

    The reaction of uranyl ions with azelaic or dodecanedioic acids under solvohydrothermal conditions leads to crystallization of anionic dinuclear cage compounds with [M(bipy/phen)3](2+) counterions (M = 3d-block cation), while the smaller suberic acid yields heterometallic metallacycles. Complexes with the longer aliphatic chains are the first triple-stranded helicates reported in actinide chemistry. PMID:26540200

  1. Density Functional Theory Study of the Complexation of the Uranyl Dication with Anionic Phosphate Ligands with and without Water Molecules

    SciTech Connect

    Jackson, Virgil E.; Gutowski, Keith E.; Dixon, David A.

    2013-09-12

    The structures, vibrational frequencies and energetics of anhydrous and hydrated complexes of UO2 2+ with the phosphate anions H2PO4 鈭, HPO4 2鈭, and PO4 3鈭 were predicted at the density functional theory (DFT) and MP2 molecular orbital theory levels as isolated gas phase species and in aqueous solution by using self-consistent reaction field (SCRF) calculations with different solvation models. The geometries and vibrational frequencies of the major binding modes for these complexes are compared to experiment where possible and good agreement is found. The uranyl moiety is nonlinear in many of the complexes, and the coordination number (CN) 5 in the equatorial plane is the predominant binding motif. The phosphates are found to bind in both monodentate and bidentate binding modes depending on the charge and the number of water molecules. The SCRF calculations were done with a variety of approaches, and different SCRF approaches were found to be optimal for different reaction types. The acidities of HxPO4 3鈥憍 in HxPO4 3鈥憍(H2O)4, x = 0鈭3 complexes were calculated with different SCRF models and compared to experiment. Phosphate anions can displace water molecules from the first solvation shell at the uranyl exothermically. The addition of water molecules can cause the bonding of H2PO4 鈭 and HPO4 2鈭 to change from bidentate to monodentate exothermically while maintaining CN 5. The addition of water can generate monodentate structures capable of cross-linking to other uranyl phosphates to form the types of structures found in the solid state. [UO2(HPO4)(H2O)3] is predicted to be a strong base in the gas phase and in aqueous solution. It is predicted to be a much weaker acid than H3PO4 in the gas phase and in solution.

  2. U-Oyl Stretching Vibrations as a Quantitative Measure of the Equatorial Bond Covalency in Uranyl Complexes: A Quantum-Chemical Investigation.

    PubMed

    Di Pietro, Poppy; Kerridge, Andrew

    2016-01-19

    The molecular structures of a series of uranyl (UO2(2+)) complexes in which the uranium center is equatorially coordinated by a first-row species are calculated at the density functional theory level and binding energies deduced. The resulting electronic structures are investigated using a variety of density-based analysis techniques in order to quantify the degree of covalency in the equatorial bonds. It is shown that a consideration of the properties of both the one-electron and electron-pair densities is required to understand and rationalize the variation in axial bonding effected by equatorial complexation. Strong correlations are found between density-based measures of the covalency and equatorial binding energies, implying a stabilizing effect due to covalent interaction, and it is proposed that uranyl U-Oyl stretching vibrational frequencies can serve as an experimental probe of equatorial covalency. PMID:26700790

  3. Molecular dynamics simulations of uranyl and uranyl carbonate adsorption at aluminosilicate surfaces.

    PubMed

    Kerisit, Sebastien; Liu, Chongxuan

    2014-04-01

    Adsorption at mineral surfaces is a critical factor controlling the mobility of uranium(VI) in aqueous environments. Therefore, molecular dynamics (MD) simulations were performed to investigate uranyl(VI) adsorption onto two neutral aluminosilicate surfaces, namely, the orthoclase (001) surface and the octahedral aluminum sheet of the kaolinite (001) surface. Although uranyl preferentially adsorbs as a bidentate inner-sphere complex on both surfaces, the free energy of adsorption on the orthoclase surface (-15 kcal mol(-1)) is significantly more favorable than that at the kaolinite surface (-3 kcal mol(-1)), which is attributed to differences in surface functional groups and the ability of the orthoclase surface to release a surface potassium ion upon uranyl adsorption. The structures of the adsorbed complexes compare favorably with X-ray absorption spectroscopy results. Simulations of the adsorption of uranyl complexes with up to three carbonate ligands revealed that uranyl complexes coordinated to up to two carbonate ions are stable on the orthoclase surface whereas uranyl carbonate surface complexes are unfavored at the kaolinite surface. Combining the MD-derived equilibrium adsorption constants for orthoclase with aqueous equilibrium constants for uranyl carbonate species indicates the presence of adsorbed uranium complexes with one or two carbonates under alkaline conditions, in support of current uranium(VI) surface complexation models. PMID:24580048

  4. Molecular Dynamics Simulations of Uranyl and Uranyl Carbonate Adsorption at Alumino-silicate Surfaces

    SciTech Connect

    Kerisit, Sebastien N.; Liu, Chongxuan

    2014-03-03

    Adsorption at mineral surfaces is a critical factor controlling the mobility of uranium(VI) in aqueous environments. Therefore, molecular dynamics (MD) simulations were performed to investigate uranyl(VI) adsorption onto two neutral alumino-silicate surfaces, namely the orthoclase (001) surface and the octahedral aluminum sheet of the kaolinite (001) surface. Although uranyl preferentially adsorbed as a bi-dentate innersphere complex on both surfaces, the free energy of adsorption at the orthoclase surface (-15 kcal mol-1) was significantly more favorable than that at the kaolinite surface (-3 kcal mol-1), which was attributed to differences in surface functional groups and to the ability of the orthoclase surface to dissolve a surface potassium ion upon uranyl adsorption. The structures of the adsorbed complexes compared favorably with X-ray absorption spectroscopy results. Simulations of the adsorption of uranyl complexes with up to three carbonate ligands revealed that uranyl complexes coordinated to up to 2 carbonate ions are stable on the orthoclase surface whereas uranyl carbonate surface complexes are unfavored at the kaolinite surface. Combining the MD-derived equilibrium adsorption constants for orthoclase with aqueous equilibrium constants for uranyl carbonate species indicates the presence of adsorbed uranium complexes with one or two carbonates in alkaline conditions, in support of current uranium(VI) surface complexation models.

  5. 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

  6. Selective colorimetric and fluorescent quenching determination of uranyl ion via its complexation with curcumin.

    PubMed

    Zhu, Jing-Hui; Zhao, Xin; Yang, Jidong; Tan, Yu-Ting; Zhang, Lei; Liu, Shao-Pu; Liu, Zhong-Fang; Hu, Xiao-Li

    2016-04-15

    Under pH4.0 HAc-NaAc buffer medium, curcumin alone possesses extraordinary weak fluorescence emission. Nevertheless, the introduction of Triton X-100 micelles can largely enhance the fluorescence intensity of curcumin. Uranyl ions can complex with micelles-capped curcumin, along with the slight red shift of curcumin fluorescence (about 1-7nm), a clear decrement of absorbance (424nm) and fluorescence (507nm) intensities, and a distinct color change from bright yellow to orange. The fluorescence decrements (螖F, 507nm) are positively correlated to the amount of uranyl ions in the concentration range of 3.7脳10(-6)-1.4脳10(-5)molL(-1). The detection limit of this fluorescence quenching methods is 3.7脳10(-6)molL(-1), which is nearly 9000 times lower than the maximum allowable level in drinking water proposed by World Health Organization. Good selectivity is achieved because of a majority of co-existing substances (such as Ce(4+), La(3+), and Th(4+)) do not affect the detection. The content of uranyl ions in tap water samples was determined by the proposed method with satisfactory results. PMID:26845580

  7. Selective colorimetric and fluorescent quenching determination of uranyl ion via its complexation with curcumin

    NASA Astrophysics Data System (ADS)

    Zhu, Jing-Hui; Zhao, Xin; Yang, Jidong; Tan, Yu-Ting; Zhang, Lei; Liu, Shao-Pu; Liu, Zhong-Fang; Hu, Xiao-Li

    2016-04-01

    Under pH 4.0 HAc-NaAc buffer medium, curcumin alone possesses extraordinary weak fluorescence emission. Nevertheless, the introduction of Triton X-100 micelles can largely enhance the fluorescence intensity of curcumin. Uranyl ions can complex with micelles-capped curcumin, along with the slight red shift of curcumin fluorescence (about 1-7 nm), a clear decrement of absorbance (424 nm) and fluorescence (507 nm) intensities, and a distinct color change from bright yellow to orange. The fluorescence decrements (螖F, 507 nm) are positively correlated to the amount of uranyl ions in the concentration range of 3.7 脳 10- 6-1.4 脳 10- 5 mol L- 1. The detection limit of this fluorescence quenching methods is 3.7 脳 10- 6 mol L- 1, which is nearly 9000 times lower than the maximum allowable level in drinking water proposed by World Health Organization. Good selectivity is achieved because of a majority of co-existing substances (such as Ce4 +, La3 +, and Th4 +) do not affect the detection. The content of uranyl ions in tap water samples was determined by the proposed method with satisfactory results.

  8. Uranyl Ion Complexes with 1,1'-Biphenyl-2,2',6,6'-tetracarboxylic Acid: Structural and Spectroscopic Studies of One- to Three-Dimensional Assemblies.

    PubMed

    Thu閞y, Pierre; Harrowfield, Jack

    2015-07-01

    1,1'-Biphenyl-2,2',6,6'-tetracarboxylic acid (H4L) was reacted with uranyl nitrate, either alone or in the presence of additional metal cations (Ni(2+), Cu(2+), Dy(3+)) under (solvo)-hydrothermal conditions, giving six complexes which were characterized by their crystal structure and, in all but one case, their emission spectrum in the solid state. [Ni(bipy)3][UO2(H2L)(H2O)]2(NO3)23H2O (1) crystallizes as a one-dimensional (1D), ribbon-like coordination polymer, while the homometallic complex [(UO2)2(L)(H2O)3]稨2O稢H3CN (2) and the heterometallic complexes [UO2Cu(L)(H2O)2]稨2O (3), [UO2Cu(L)(H2O)]稨2O (4), and [(UO2)5Cu4(HL)6(bipy)4]2H2O (5) display two-dimensional (2D) arrangements. Lastly, the uranyl-lanthanide heterometallic complex [(UO2)8Dy(HL)6(H2O)8](I)8H2O (6) crystallizes as a three-dimensional (3D) framework. Although these assemblies adopt different topologies, the {4(2).6} linear motif found in 1 is discernible in the structures of 2, 5, and 6, in which the higher dimensionality arises from further bridging of these subunits by uranyl (2), copper (5), or both uranyl and dysprosium (6) cations. The tetracarboxylic/ate ligands have their two aromatic rings nearly perpendicular to one another. No two of them adopt the same coordination mode in this series (except in the similar complexes 3 and 4), but chelation involving one carboxylate group from each ring is nearly ubiquitous, and the ensuing position of the cation favors the formation of planar architectures. The emission spectra of complexes 2-5 measured in the solid state show the usual uranyl vibronic fine structure, although with significant differences in the emission intensity, while complete quenching of the luminescence is observed in 1. PMID:26102315

  9. Composition for detecting uranyl

    DOEpatents

    Baylor, Lewis C. (North Augusta, SC); Stephens, Susan M. (Athens, GA)

    1995-01-01

    A composition for detecting the presence and concentration of a substance such as uranyl, comprising an organohalide covalently bonded to an indicator for said substance. The composition has at least one active OH site for forming a complex with the substance to be detected. The composition is made by reacting equimolar amounts of the indicator and the organohalide in a polar organic solvent. The absorbance spectrum of the composition-uranyl complex is shifted with respect to the absorbance spectrum of the indicator-uranyl complex, to provide better spectral resolution for detecting uranyl.

  10. Synthesis and structures of new uranyl malonate complexes with carbamide derivatives

    NASA Astrophysics Data System (ADS)

    Serezhkina, L. B.; Grigor'ev, M. S.; Medvedkov, Ya. A.; Serezhkin, V. N.

    2015-09-01

    Crystals of new malonate-containing uranyl complexes [UO2(C3H2O4)( Imon)(H2O)] ( I) and [UO2(C3H2O4)( Meur)3] ( II), where Imon is imidazolidin-2-one (ethylenecarbamide) and Meur is methyl-carbamide, have been synthesized and studied by X-ray diffraction. Both compounds crystallize in the monoclinic system with the following unit-cell parameters (at 100 K): a = 11.1147(10) , b = 6.9900(6) , c = 14.4934(12) , ? = 92.042(2), V = 1125.30(17) 3, sp. gr. P21/ n, Z = 4, R 1 = 0.0398 ( I); a = 16.6613(5) , b = 9.5635(3) , c = 22.9773(6) , ? = 103.669(2), V = 3557.51(18) 3, sp. gr. C2/ c, Z = 8, R 1 = 0.0207 ( II). The crystals are composed of electroneutral chains [UO2(C3H2O4)( Imon)(H2O)] and mononuclear groups [UO2(C3H2O4)( Meur)3] as the structural units belonging to the crystal-chemical groups AT 11 M {2/1} and AB 01 M {3/1} ( A =UO{2/2+}, T 11 and B 01 = C3H2, M 1 = Imon, H2O, or Meur), respectively, of uranyl complexes. The packing modes of the uranyl-containing complexes were analyzed by the method of molecular Voronoi桪irichlet polyhedra.

  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; Gr鴑bech-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. 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

  13. Complex coordinates in transformation optics

    SciTech Connect

    Popa, Bogdan-Ioan; Cummer, Steven A.

    2011-12-15

    We show that complex coordinates used in conjunction with transformation optics offer an extra degree of freedom that allows control over not only the propagation direction of electromagnetic waves but also their amplitude. We illustrate this idea in two applications. First, we show that in an n-dimensional space one can manipulate the field amplitude for up to n different amplitude distributions in regions that are critical to the performance of the device under consideration, and thus reduce the device's sensitivity to design imperfections in these regions. Second, we expand previous work on reflectionless perfectly matched layers and show how complex coordinates and transformation optics are a natural choice for designing perfectly matched layers of arbitrary shape.

  14. Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation.

    PubMed

    Xiao, Cheng-Liang; Wang, Cong-Zhi; Mei, Lei; Zhang, Xin-Rui; Wall, Nathalie; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-08-28

    The tetradentate N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard-soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1?:?2 Eu-L species ([EuL2(NO3)](2+)) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1?:?1 Eu-L species ([EuL(NO3)2](+)) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)](+)) is the only detected species for the uranyl complexes. The [ThL2(NO3)2](2+) species can be observed at low [M]/[L] ratios; the 1?:?2 species ([ThL2(NO3)](3+)) and a new 1?:?1 species ([ThL(NO3)3](+)) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal-ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M-L complexes in acetonitrile are found to be in good agreement with the ESI-MS results. PMID:26200662

  15. Gas-phase reactions of molecular oxygen with uranyl(V) anionic complexes-synthesis and characterization of new superoxides of uranyl(VI).

    PubMed

    Lucena, Ana F; Carretas, Jos M; Mar鏰lo, Joaquim; Michelini, Maria C; Gong, Yu; Gibson, John K

    2015-04-16

    Gas-phase complexes of uranyl(V) ligated to anions X(-) (X = F, Cl, Br, I, OH, NO3, ClO4, HCO2, CH3CO2, CF3CO2, CH3COS, NCS, N3), [UO2X2](-), were produced by electrospray ionization and reacted with O2 in a quadrupole ion trap mass spectrometer to form uranyl(VI) anionic complexes, [UO2X2(O2)](-), comprising a superoxo ligand. The comparative rates for the oxidation reactions were measured, ranging from relatively fast [UO2(OH)2](-) to slow [UO2I2](-). The reaction rates of [UO2X2](-) ions containing polyatomic ligands were significantly faster than those containing the monatomic halogens, which can be attributed to the greater number of vibrational degrees of freedom in the polyatomic ligands to dissipate the energy of the initial O2-association complexes. The effect of the basicity of the X(-) ligands was also apparent in the relative rates for O2 addition, with a general correlation between increasing ligand basicity and O2-addition efficiency for polyatomic ligands. Collision-induced dissociation of the superoxo complexes showed in all cases loss of O2 to form the [UO2X2](-) anions, indicating weaker binding of the O2(-) ligand compared to the X(-) ligands. Density functional theory computations of the structures and energetics of selected species are in accord with the experimental observations. PMID:25807358

  16. DFT Study of Uranyl Peroxo Complexes with H鈧侽, F鈦, OH鈦, CO鈧 虏鈦, and NO鈧-

    SciTech Connect

    Odoh, Samuel O.; Schreckenbach, Georg

    2013-05-06

    The structural and electronic properties of monomeric uranyl peroxo complexes with aquo, hydroxo, fluoro, carbonate, and nitrate ligands have been studied using DFT calculations with relativistic pseudopotentials. The calculated affinity of the peroxo group for the actinyl moiety far exceeds that of the other ligands tested in this work.

  17. Experimental and Theoretical Studies on the Fragmentation of Gas-Phase Uranyl-, Neptunyl- and Plutonyl-Diglycolamide Complexes

    SciTech Connect

    Gong, Yu; Hu, Han-Shi; Rao, Linfeng; Li, Jun; Gibson, John K.

    2013-10-10

    Fragmentation of actinyl(VI) complexes UVIO2(L)22+, NpVIO2(L)22+ and PuVIO2(L)22+ (L = tetramethyl-3-oxa-glutaramide, TMOGA) produced by electrospray ionization was examined in the gas phase by collision induced dissociation (CID) in a quadrupole ion trap mass spectrometer. Cleavage of the C-Oether bond was observed for all three complexes, with dominant products being UVIO2(L)(L-86)+ with charge reduction, and NpVIO2(L)(L-101)2+ and PuVIO2(L)(L-101)2+ with charge conservation. The neptunyl and plutonyl complexes also exhibited substantial L+ loss to give pentavalent complexes NpVO2(L)+ and PuVO2(L)+, whereas the uranyl complex did not, consistent with the comparative An 5f-orbital energies and the AnVIO22+/AnVO2+ (An = U, Np, Pu) reduction potentials. CID of NpVO2(L)2+ and PuVO2(L)2+ was dominated by neutral ligand loss to form NpVO2(L)+ and PuVO2(L)+, which hydrated by addition of residual water in the ion trap; UVO2(L)2+ was not observed. Theoretical calculations of the structures and bonding of the AnVIO2(L)22+ complexes using density functional theory reveal that the metal centers are coordinated by six oxygen atoms from the two TMOGA ligands. The results are compared with radiolytic decomposition of TMOGA in solution.

  18. Multiphoton dissociation of some volatile uranyl complexes. I. The phenomena of reversible and permanent dissociation

    NASA Astrophysics Data System (ADS)

    Eberhardt, J. E.; Hoare, I. E.; Johnson, D. A.; Knott, R. B.; Pryor, A. W.; Waugh, A. B.

    1982-11-01

    Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato) dioxo uranium (VI) is stable and volatile at ?120癈, particularly with a ligand such as ammonia or trimethyl phosphate, and susceptible to multiphoton dissociation (mpd) via tle uranyl asymmetric vibration at ?950 cm -1. There are two dissociation paths: (i) detachment of the ligand at fluences below 0.2 J cm -2; (ii) permanent dissociation Of UO 2(hfacac) 2 into UO 2F 2 and a furanone C 5F 5O 2H at fluences above 0.6 J cm -2. Ligand detachment appears to be a conventional unimolecular mpd reaction describable by master equations in spite of the remarkably low fluence threshold. Permanent dissociation shows much greater chemical complexity.

  19. 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.

  20. Infrared Multiphoton Dissociation Spectroscopy of a Gas-Phase Complex of Uranyl and 3-Oxa-Glutaramide: An Extreme Red-Shift of the [O=U=O]虏鈦 Asymmetric Stretch

    SciTech Connect

    Gibson, John K.; Hu, Hanshi; Van Stipdonk, Michael J.; Berden, Giel; Oomens, Jos; Li, Jun

    2015-04-09

    The gas-phase complex UO鈧(TMOGA)鈧偮测伜 (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700鈥1800 cm鈦宦 was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm鈦宦 (<1%) and a maximum deviation of 21 cm鈦宦 (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric 谓鈧 mode, which appeared at 965 cm鈦宦 and was predicted by DFT as 953 cm鈦宦. This 谓鈧 frequency is red-shifted relative to bare uranyl, UO鈧偮测伜, by ca. 150 cm鈦宦 due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO鈧(acetone)鈧劼测伜. The uranyl 谓鈧 frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central Oether of TMOGA has been replaced by CH鈧. The computed 谓鈧 for UO鈧(TMGA)鈧偮测伜, 950 cm鈦宦, is essentially the same as that for UO鈧(TMOGA)鈧偮测伜, suggesting that electron donation to uranyl from the Oether of TMOGA is minor. The computed 谓鈧 asymmetric stretching frequencies for the three actinyl complexes, UO鈧(TMOGA)鈧偮测伜, NpO鈧(TMOGA)鈧偮测伜 and PuO鈧(TMOGA)鈧偮测伜, are comparable. This similarity is discussed in the context of the relationship between 谓鈧 and intrinsic actinide-oxygen bond energies in actinyl complexes.

  1. 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.

  2. A calorimetric study of the hydrolysis and peroxide complex formation of the uranyl(VI) ion.

    PubMed

    Zanonato, Pier Luigi; Di Bernardo, Plinio; Grenthe, Ingmar

    2014-02-14

    The enthalpies of reaction for the formation of uranyl(vi) hydroxide {[(UO2)2(OH)2](2+), [(UO2)3(OH)4](2+), [(UO2)3(OH)5](+), [(UO2)3(OH)6](aq), [(UO2)3(OH)7](-), [(UO2)3(OH)8](2-), [(UO2)(OH)3](-), [(UO2)(OH)4](2-)} and peroxide complexes {[UO2(O2)(OH)](-) and [(UO2)2(O2)2(OH)](-)} have been determined from calorimetric titrations at 25 掳C in a 0.100 M tetramethyl ammonium nitrate ionic medium. The hydroxide data have been used to test the consistency of the extensive thermodynamic database published by the Nuclear Energy Agency (I. Grenthe, J. Fuger, R. J. M. Konings, R. J. Lemire, A. B. Mueller, C. Nguyen-Trung and H. Wanner, Chemical Thermodynamics of Uranium, North-Holland, Amsterdam, 1992 and R. Guillaumont, T. Fangh盲nel, J. Fuger, I. Grenthe, V. Neck, D. J. Palmer and M. R. Rand, Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Elsevier, Amsterdam, 2003). A brief discussion is given about a possible structural relationship between the trinuclear complexes [(UO2)3(OH)n](6-n), n = 4-8. PMID:24301256

  3. Complexes of uranyl(II), vanadyl(II) and zirconyl(II) with orotic acid 搗itamin B13: Synthesis, spectroscopic, thermal studies and antibacterial activity

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2007-10-01

    A convenient method for the preparation of complexes of the uranyl [UO 2] 2+, vanadyl [VO] 2+ and [ZrO] 2+ ions with vitamin B13 (Orotic acid; H 3OA) is reported and this has enabled three complexes of orotate anion (1-) to be formulated: [M(C 5H 3N 2O 4) 2(H 2O) 2](H 2O) n [where M = [UO 2] 2+, [VO] 2+, [ZrO] 2+; n = 1, 6, 3, respectively]. The new bisorotate (H 2OA) 1- complexes were synthesis and characterized by elemental analysis, molar conductivity, spectral methods (UV-vis, mass, 1H NMR and mid infrared spectra), and simultaneous thermal analysis (TG and DTG) techniques. Physical measurements indicate that the neutral orotic acid ligand in its mono/anion form, is bonded to oxometal ions through the carboxylic groups (two monodentate orotate anions and complete the coordination sphere by coordinated water molecules). The molar conductance data confirm that the orotate complexes are non-electrolytes. The X-ray powder diffraction (XRD) as well as scanning electron microscopy (SEM) shows that the studied complexes have amorphous structures. The kinetic thermodynamic parameters, such as, E?, ? H?, ? S? and ? G? are calculated from the DTG curves. The antibacterial activity of the orotic acid and their complexes was evaluated against gram positive/negative bacteria.

  4. 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.

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

    SciTech Connect

    J. B. Briggs; 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.

  6. Resonance light scattering detection of fructose bisphosphates using uranyl-salophen complex-modified gold nanoparticles as optical probe.

    PubMed

    Li, Shijun; Liao, Lifu; Wu, Rurong; Yang, Yanyan; Xu, Li; Xiao, Xilin; Nie, Changming

    2015-11-01

    In this paper, we report a resonance light scattering (RLS) method for the determination of fructose bisphosphates (FBPs) in water solution using fructose 1,6-bisphosphate (F-1,6-BP) as a model analyte without the procedure of extracting target analyte. The method used a type of modified gold nanoparticles (GNPs) as optical probe. The modified GNPs are uranyl-salophen-cysteamine-GNPs (U-Sal-Cy-GNPs) which are obtained through the acylation reaction of carboxylated salophen with cysteamine-capped GNPs (Cy-GNPs) to form Sal-Cy-GNPs and then the chelation reaction of uranyl with tetradentate ligand salophen in the Sal-Cy-GNPs. A FBP molecule is used easily to connect two U-Sal-Cy-GNPs to cause the aggregation of the GNPs by utilizing the specific affinity of uranyl-salophen complex to phosphate group, resulting in the production of strong RLS signal from the system. The amount of FBPs can be determined through detecting the RLS intensity change of the system. A linear range was found to be 2.5 to 75爊mol/L with a detection limit of 0.91爊mol/L under optimal conditions. The method has been successfully used to determine FBPs in real samples with the recoveries of 96.5-103.5%. PMID:26403237

  7. 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

  8. 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.

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

    SciTech Connect

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

    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.

  10. A QM/MM Study of Aqueous Solvation of the Uranyl Fluoride [UO?F???] Complex

    SciTech Connect

    Infante, Ivan A.; Visscher, Lucas

    2003-12-16

    The aqueous solvation of the uranylfluoride complex [UO2F42-] was studied using full quantum mechanical (QM) and hybrid QM/molecular mechanics (MM) methods. Inclusion of a complete first solvation shell was found necessary to reproduce the experimentally observed heptacoordination of uranium. An efficient and accurate computational model is proposed that consists of structure optimization of the coordinated uranium complex as QM region, followed by single-point full QM calculations to compute relative energies. This method is proven feasible for studies of large solvated actinide complexes. (C) 2003 Wiley Periodicals, Inc.

  11. Self-assembly of a 3d-5f trinuclear single-molecule magnet from a pentavalent uranyl complex.

    PubMed

    Chatelain, Lucile; Walsh, James P S; P閏aut, Jacques; Tuna, Floriana; Mazzanti, Marinella

    2014-12-01

    Mixed-metal uranium compounds are very attractive candidates in the design of single-molecule magnets (SMMs), but only one 3d-5f hetero-polymetallic SMM containing a uranium center is known. Herein, we report two trimeric heterodimetallic 3d-5f complexes self-assembled by cation-cation interactions between a uranyl(V) complex and a TPA-capped M(II) ?complex (M=Mn (1), Cd (2); TPA=tris(2-pyridylmethyl)amine). The metal centers were strategically chosen to promote the formation of discrete molecules rather than extended chains. Compound 1, which contains an almost linear {Mn?O?U?O?Mn} core, exhibits SMM behavior with a relaxation barrier of 810.5?K-the highest reported for a mono-uranium system-arising from intramolecular Mn-U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. Compound 1 also exhibits an open magnetic hysteresis loop at temperatures less than 3?K, with a significant coercive field of 1.9?T at 1.8?K. PMID:25284018

  12. Global symplectic coordinates on complex domains

    NASA Astrophysics Data System (ADS)

    Cuccu, Fabrizio; Loi, Andrea

    2006-02-01

    In this paper we deal with complex domains M?C equipped with a K鋒ler form ?={i}/{2}??痜, where f:M?R only depends on |zj|2, j=1,,n for the complex coordinates (z1,,zn) in C. We give an explicit symplectic immersion ? of (M,?) into R2n in Section 2. In Section 3 we study when the map ? is a global symplectomorphism for the case of complete Reinhardt domains in C.

  13. 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...

  14. 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.; Zhang, B.; Zhang, X.

    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.

  15. Uranyl Ion Complexes with Long-Chain Aliphatic 伪,蠅-Dicarboxylates and 3d-Block Metal Counterions.

    PubMed

    Thu茅ry, Pierre; Harrowfield, Jack

    2016-03-01

    Twelve new complexes were obtained from reaction of uranyl ions with the aliphatic dicarboxylic acids HOOC-(CH2)n-2-COOH (H2Cn; n = 7-10 and 12) under solvo-hydrothermal conditions, in the presence of 3d-block metal ions (Mn(2+), Fe(3+), Co(2+), Ni(2+), and Cu(2+)) and 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen). In contrast to previously reported triple-stranded helicates obtained with C9(2-) and C12(2-), all these complexes crystallize as polymeric one-dimensional (1D) or two-dimensional (2D) species. [Fe(bipy)3][(UO2)2(C7)3]路3H2O (1), [Cu(phen)2]2[(UO2)3(C7)4(H2O)2]路2H2O (2), and [Cu(bipy)2]2[(UO2)2(C9)3] (6), in which the 3d cation was reduced in situ, are 1D ladderlike polymers displaying tetra- or hexanuclear rings, of sufficient width to encompass two counterions in 2 and 6. The three complexes [Co(phen)3][(UO2)3(C8)3(O)]路H2O (3), [Ni(phen)3][(UO2)3(C8)3(O)]路H2O (4) and [Co(phen)3][(UO2)3(C9)3(O)]路H2O (5) contain bis(渭3-oxo)-bridged tetranuclear secondary building units, and they crystallize as deeply furrowed 2D assemblies. Depending on the nature of the counterion, C10(2-) gives [Ni(bipy)3][(UO2)2(C10)3]路2H2O (7), a 2D network displaying elongated decanuclear rings containing the counterions, or [Mn(phen)3][(UO2)2(C10)3]路6H2O (8), [Co(phen)3][(UO2)2(C10)3]路7H2O (9), and [Ni(phen)3][(UO2)2(C10)3]路7H2O (10), which consist of 2D assemblies with honeycomb topology; the hexanuclear rings in 8-10 are chairlike and occupied by one counterion and two uranyl groups from neighboring layers. Two complexes of the ligand with the longest chain, C12(2-), are reported. [UO2(C12)(bipy)] (11) is a neutral 1D species in which bipy chelates the uranyl ion and plays an important role in the packing through 蟺-stacking interactions. Two polymeric units, 1D and 2D, coexist in the complex [Ni(bipy)3][(UO2)2(C12)3][UO2(C12)(H2O)2]路H2O (12); the 2D network has the honeycomb topology, but the hexanuclear rings are markedly convoluted, with local features akin to those in helicates, and the counterions are embedded in intralayer cavities. Emission spectra measured in the solid state show in most cases various degrees of quenching, with intense and well-resolved uranyl emission being observed only for complexes 2 and 11. PMID:26890047

  16. Ion Pair Binding in the Solid-State with Ditopic Crown Ether Uranyl Salophen Receptors.

    PubMed

    M鋕el, Toni; Minkkinen, Miia-Elina; Rissanen, Kari

    2016-02-01

    Two ditopic uranyl salophen receptors with benzo-15-crown-5 and benzo-18-crown-6 units (R(1) and R(2), respectively) have been synthesized from commercially available starting materials. Comprehensive studies on the solid-state ion pair complexation with various alkali and ammonium halides have been conducted. From the 19 obtained solid-state structures (6 structures with R(1), 13 structures with R(2)), three general interaction motifs I-III have been observed. Interaction motif I has a separated ion pair with the cation coordinated to the crown ether unit, and the anion or oxygen containing solvent molecule coordinated to the uranyl center. The interaction motif II manifests a polymeric structure with a contact ion pair between the uranyl-coordinated anion and cation coordinated in the crown ether in the adjacent receptor. Interaction motif III consists of a more general stacked packing structure of the receptors with or without ion pairs. From the obtained solid-state structures, the complex R(2)種aI shows an interesting formation of infinite coordination polymeric structure where the crown ether complexed sodium cations and the O?U?O units of the adjacent receptors form a nearly linear 1-D chains. In the course of this work also the first solid-state structure of uranyl salophen acetate complex was obtained (R(2)稫AcO). PMID:26788749

  17. 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

  18. 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,

  19. Gas-Phase Coordination Complexes of UVIO{2/2+}, NpVIO{2/2+}, and PuVIO{2/2+} with Dimethylformamide

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    Electrospray ionization of actinyl perchlorate solutions in H2O with 5% by volume of dimethylformamide (DMF) produced the isolatable gas-phase complexes, [AnVIO2(DMF)3(H2O)]2+ and [AnVIO2(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).

  20. Structure Determination of a Complex Tubular Uranyl Phenylphosphonate, (UO(2))(3)(HO(3)PC(6)H(5))(2)(O(3)PC(6)H(5))(2).H(2)O, from Conventional X-ray Powder Diffraction Data.

    PubMed

    Poojary, Damodara M.; Cabeza, Aurelio; Aranda, Miguel A. G.; Bruque, Sebastian; Clearfield, Abraham

    1996-03-13

    The three-dimensional structure of a complex tubular uranyl phosphonate, (UO(2))(3)(HO(3)PC(6)H(5))(2)(O(3)PC(6)H(5))(2).H(2)O, was determined ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. The crystals belong to the space group P2(1)2(1)2(1), with a = 17.1966(2) , b = 7.2125(2) , c = 27.8282(4) , and Z = 4. The structure consists of three independent uranium atoms, among which two are seven-coordinated and the third is eight-coordinated. These metal atoms are connected by four different phosphonate groups to form a one-dimensional channel structure along the b axis. The phenyl groups are arranged on the outer periphery of the channels, and their stacking forces keep the channels intact in the lattice. The determination of this structure which contains 50 non-hydrogen atoms in the asymmetric unit, from conventional X-ray powder data, represents significant progress in the application of powder techniques to structure solution of complex inorganic compounds, including organometallic compounds. PMID:11666360

  1. Selectivity in ligand binding to uranyl compounds: A synthetic, structural, thermodynamic and computational study

    SciTech Connect

    Arnold, John

    2015-01-21

    The uranyl cation (UO鈧偮测伜) is the most abundant form of uranium on the planet. It is estimated that 4.5 billion tons of uranium in this form exist in sea water. The ability to bind and extract the uranyl cation from aqueous solution while separating it from other elements would provide a limitless source of nuclear fuel. A large body of research concerns the selective recognition and extraction of uranyl. A stable molecule, the cation has a linear O=U=O geometry. The short U-O bonds (1.78 脜) arise from the combination of uranium 5f/6d and oxygen 2p orbitals. Due to the oxygen moieties being multiply bonded, these sites were not thought to be basic enough for Lewis acidic coordination to be a viable approach to sequestration. The goal of this research is thus to broaden the coordination chemistry of the uranyl ion by studying new ligand systems via synthetic, structural, thermodynamic and computational methods. It is anticipated that this fundamental science will find use beyond actinide separation technologies in areas such as nuclear waste remediation and nuclear materials. The focus of this study is to synthesize uranyl complexes incorporating amidinate and guanidinate ligands. Both synthetic and computational methods are used to investigate novel equatorial ligand coordination and how this affects the basicity of the oxo ligands. Such an understanding will later apply to designing ligands incorporating functionalities that can bind uranyl both equatorially and axially for highly selective sequestration. Efficient and durable chromatography supports for lanthanide separation will be generated by (1) identifying robust peptoid-based ligands capable of binding different lanthanides with variable affinities, and (2) developing practical synthetic methods for the attachment of these ligands to Dowex ion exchange resins.

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

    PubMed

    Stewart, Brandy D; Mayes, Melanie A; Fendorf, Scott

    2010-02-01

    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(2)(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(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-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 ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption. PMID:20058915

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

    SciTech Connect

    Stewart, B.D.; Mayes, Melanie; Fendorf, Scott

    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.

  4. 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, VOSO4路XH2O and ZrOCl2路XH2O 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.

  5. 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.

  6. Umbellate distortions of the uranyl coordination environment result in a stable and porous polycatenated framework that can effectively remove cesium from aqueous solutions.

    PubMed

    Wang, Yanlong; Liu, Zhiyong; Li, Yuxiang; Bai, Zhuanling; Liu, Wei; Wang, Yaxing; Xu, Xiaomei; Xiao, Chengliang; Sheng, Daopeng; Diwu, Juan; Su, Jing; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2015-05-20

    Searching for new chemically durable and radiation-resistant absorbent materials for actinides and their fission products generated in the nuclear fuel cycle remain highly desirable, for both waste management and contamination remediation. Here we present a rare case of 3D uranyl organic framework material built through polycatenating of three sets of graphene-like layers, which exhibits significant umbellate distortions in the uranyl equatorial planes studied thoroughly by linear transit calculations. This unique structural arrangement leads to high 尾 and 纬 radiation-resistance and chemical stability in aqueous solutions within a wide pH range from 3 to 12. Being equipped with the highest surface area among all actinide compounds known to date and completely exchangeable [(CH3)2NH2](+) cations in the structure, this material is able to selectively remove cesium from aqueous solutions while retaining the polycatenated framework structure. PMID:25939750

  7. Two-Electron Three-Centered Bond in Side-On (?2) Uranyl(V) Superoxo Complexes

    SciTech Connect

    Bryantsev, Vyacheslav; De Jong, Wibe A.; Cossel, Kevin C.; Diallo, Mamadou S.; Goddard III, W. A.; Groenewold, G. S.; Chien, Winnie; Van Stipdonk, Michael J.

    2008-06-10

    Mononuclear dioxygen-metal compounds, such as FeO2 complexes with Schiff base and porphyrin ligands, play an essential role in chemistry ranging from oxyhemoglobin to cytochrome P-450 and cytochrome oxidase. It is well known that the superoxo complexes involved in these systems have end-on (?1) coordination geometries with O朞 bond lengths of ~1.30 , Fe朞朞 bond angles of ~135o, and vibrational frequencies of ~1150 cm-1,1 which reflects a formal change of the oxidation state from Mn+ to Mn+1. In addition, there are side-on (?2) peroxospecies, such as [Fe(porphyrin)(O2)], in which the O朞 bond lengths is ~1.46 and vibrational frequencies of ~820 cm-1.1 These reflect a formal change of the oxidation state from Mn+ to Mn+2.

  8. Colloidal Nanocrystals Fluoresced by Surface Coordination Complexes

    PubMed Central

    Wang, Guan; Ji, Jianwei; Zhang, Xinwen; Zhang, Yan; Wang, Qiangbin; You, Xiaozeng; Xu, Xiangxing

    2014-01-01

    Colloidal Nanocrystals (NCs) with fluorescence originating from surface complexes are successfully prepared. The components of these NCs range from insulator, semiconductor to metal, with either pure phase, doped or core/shell structures. The photoluminescence of these NCs can be reversibly tuned across the visible to infrared spectrum, and even allow multi-color emission. A light emitting device is fabricated and a new in vivo cell imaging method is performed to demonstrate the power of this technology for emerging applications. PMID:24970242

  9. 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 fine 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.

  10. XPS spectra of uranyl minerals and synthetic uranyl compounds. II: The O 1s spectrum

    NASA Astrophysics Data System (ADS)

    Schindler, M.; Hawthorne, F. C.; Freund, M. S.; Burns, P. C.

    2009-05-01

    The O 1s spectrum is examined for 19 uranyl minerals of different composition and structure. Spectra from single crystals were measured with a Kratos Axis Ultra X-ray Photoelectron Spectrometer with a magnetic-confinement charge-compensation system. Well-resolved spectra with distinct maxima, shoulders and inflections points, in combination with reported and measured binding energies for specific O 2- species and structural data of the uranyl minerals are used to resolve the fine structure of the O 1s envelope. The resolution of the O 1s spectra includes, for the first time, different O 2- bands, which are assigned to O atoms linking uranyl with uranyl polyhedra ( Usbnd Osbnd U) and O atoms of uranyl groups ( Odbnd Udbnd O). The resolved bands in the O 1s spectrum occur at distinct ranges in binding energy: bands for ( Usbnd Osbnd U) occur at 529.6-530.4 eV, bands for ( Odbnd Udbnd O) occur at 530.6-531.4 eV, bands for O 2- in the equatorial plane of the uranyl polyhedra linking uranyl polyhedra with ( TO n) groups ( T = Si, S, C, P, Se) ( Tsbnd O) occur at 530.9-532.2 eV; bands for (OH) groups in the equatorial plane of the uranyl polyhedra ( OH) occur at 532.0-532.5 eV, bands of (H 2O) groups in the interstitial complex of the uranyl minerals ( H2O interst) occur at 533.0-533.8 eV and bands of physisorbed (H 2O) groups on the surface of uranyl minerals ( H2O adsorb) occur at 534.8-535.2 eV. Treatment of uranyl minerals with acidic solutions results in a decrease in Usbnd Osbnd U and an increase in OH. Differences in the ratio of OH : Odbnd Udbnd O between the surface and bulk structure is larger for uranyl minerals with a high number of Usbnd Osbnd U and Tsbnd O species in the bulk structure which is explained by protonation of underbonded Usbnd O, Usbnd Osbnd U and Tsbnd O terminations on the surface. The difference in the ratio of H2O interst : Odbnd Udbnd O between the bulk and surface structures is larger for uranyl minerals with higher percentages of H2O interst as well as, with a higher number of interstitial H 2O groups that are not bonded to interstitial cations, resulting in easier dehydration of interstitial H 2O groups in uranyl minerals during exposure to a vacuum.

  11. Identification of coordinately dysregulated subnetworks in complex phenotypes.

    PubMed

    Chowdhury, Salim A; Koyut黵k, Mehmet

    2010-01-01

    In the study of complex phenotypes, single gene markers can only provide limited insights into the manifestation of phenotype. To this end, protein-protein interaction (PPI) networks prove useful in the identification of multiple interacting markers. Recent studies show that, when considered together, many proteins that are connected via physical and functional interactions exhibit significant differential expression with respect to various complex phenotypes, including cancers. As compared to single gene markers, these "coordinately dysregulated subnetworks" improve diagnosis and prognosis of cancer significantly and offer novel insights into the network dynamics of phenotype. However, the problem of identifying coordinately dysregulated subnetworks presents significant algorithmic challenges. Existing approaches utilize heuristics that aim to greedily maximize information-theoretic class separability measures, however, by definition of "coordinate" dysregulation, such greedy algorithms do not suit well to this problem. In this paper, we formulate coordinate dysregulation in the context of the well-known set-cover problem, with a view to capturing the coordination between multiple genes at a sample-specific resolution. Based on this formulation, we adapt state-of-the-art approximation algorithms for set-cover to the identification of coordinately dysregulated subnetworks. Comprehensive experimental results on human colorectal cancer (CRC) show that, when compared to existing algorithms, the proposed algorithm, NETCOVER, improves diagnosis of cancer and prediction of metastasis significantly. Our results also demonstrate that subnetworks in the neighborhood of known CRC driver genes exhibit significant coordinate dysregulation, indicating that the notion of coordinate dysregulation may indeed be useful in understanding the network dynamics of complex phenotypes. PMID:19908366

  12. 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.

  13. Memory for Negation in Coordinate and Complex Sentences

    ERIC Educational Resources Information Center

    Harris, Richard J.

    1976-01-01

    Two experiments were run to test memory for the negation morpheme "not" in coordinate sentences (e.g., The ballerina had twins and the policewoman did not have triplets) and complex sentences (e.g., The ghost scared Hamlet into not murdering Shakespeare). (Editor)

  14. 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.

  15. Molecular Simulation of the Diffusion of Uranyl Carbonate Species in Aqueous Solution

    SciTech Connect

    Kerisit, Sebastien N.; Liu, Chongxuan

    2010-09-01

    Molecular dynamics simulations of aqueous uranyl carbonate species were carried out with two different potential models to gain molecular-level insight into the hydration properties of these species and evaluate the ability of the two models to reproduce published ab initio and experimental data. The simulation results were used to estimate the self-diffusion coefficients of uranyl carbonate species that often dominate uranyl speciation in groundwater systems. The first potential model was based on a series of shell models developed by Parker and co-workers (including (DE LEEUW and PARKER, 1998; KERISIT and PARKER, 2004; PAVESE et al., 1996). The second potential model was a rigid-ion model based on the flexible SPC water model (TELEMAN et al., 1987), the uranyl model of Guilbaud and Wipff (GUILBAUD and WIPFF, 1996), and the parameters for the carbonate ion given by Greathouse and co-workers (GREATHOUSE and CYGAN, 2005; GREATHOUSE et al., 2002). Analysis of structural (mean interatomic distances and coordination numbers) and dynamical (water residence times in hydration shell and self-diffusion coefficients) properties showed that, overall, the first potential model performed best when compared to published data, although the only major discrepancy with the second model was a misrepresentation of the configuration adopted by the alkaline-earth uranyl carbonate ions. The diffusion coefficients obtained for the alkaline-earth cations and the uranyl ion were compared with three variants of the Stokes-Einstein (SE) equation and it was found that none of the three SE models were able to reproduce both the absolute values and the overall trend determined from the molecular dynamics simulations. However, as would be expected based on the SE equation, a plot of the diffusion coefficients of the uranyl carbonate complexes as a function of the inverse of the equivalent spherical radius showed a general linear dependence with the two models yielding almost identical gradients. The nature of the alkaline-earth cation in the uranyl carbonate complexes was found to have only a small effect on the ion抯 diffusion coefficient.

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

    PubMed

    Kaub, Christoph; Augenstein, Timo; Bauer, Thomas O; Rothe, Elisa; Esmezjan, Lars; Sch黱emann, 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-M鰏sbauer spectroscopy was performed for compounds 2-4. The spectra show isomer shifts and quadrupole splittings that are typical for diamagnetic ferrocenes. PMID:24735256

  17. Coordinating complex problem-solving among distributed intelligent agents

    NASA Technical Reports Server (NTRS)

    Adler, Richard M.

    1992-01-01

    A process-oriented control model is described for distributed problem solving. The model coordinates the transfer and manipulation of information across independent networked applications, both intelligent and conventional. The model was implemented using SOCIAL, a set of object-oriented tools for distributing computing. Complex sequences of distributed tasks are specified in terms of high level scripts. Scripts are executed by SOCIAL objects called Manager Agents, which realize an intelligent coordination model that routes individual tasks to suitable server applications across the network. These tools are illustrated in a prototype distributed system for decision support of ground operations for NASA's Space Shuttle fleet.

  18. Six-coordinate nitrito and nitrato complexes of manganese porphyrin.

    PubMed

    Kurtikyan, T S; Hayrapetyan, V A; Mehrabyan, M M; Ford, P C

    2014-11-17

    Reaction of small increments of NO2 gas with sublimed amorphous layers of Mn(II)(TPP) (TPP = meso-tetra-phenylporphyrinato dianion) in a vacuum cryostat leads to formation of the 5-coordinate monodentate nitrato complex Mn(III)(TPP)(畏(1)-ONO2) (II). This transformation proceeds through the two distinct steps with initial formation of the five coordinate O-nitrito complex Mn(III)(TPP)(畏(1)-ONO) (I) as demonstrated by the electronic absorption spectra and by FTIR spectra using differently labeled nitrogen dioxide. A plausible mechanism for the second stage of reaction is offered based on the spectral changes observed upon subsequent interaction of (15)NO2 and NO2 with the layered Mn(TPP). Low-temperature interaction of I and II with the vapors of various ligands L (L = O-, S-, and N-donors) leads to formation of the 6-coordinate O-nitrito Mn(III)(TPP)(L)(畏(1)-ONO) and monodentate nitrato Mn(III)(TPP)(L)(畏(1)-ONO2) complexes, respectively. Formation of the 6-coordinate O-nitrito complex is accompanied by the shifts of the 谓(N鈺怬) band to lower frequency and of the 谓(N-O) band to higher frequency. The frequency difference between these bands 螖谓 = 谓(N鈺怬) - 谓(N-O) is a function of L and is smaller for the stronger bases. Reaction of excess NH3 with I leads to formation of Mn(TPP)(NH3)(畏(1)-ONO) and of the cation [Mn(TPP)(NH3)2](+) plus ionic nitrite. The nitrito complexes are relatively unstable, but several of the nitrato species can be observed in the solid state at room temperature. For example, the tetrahydrofuran complex Mn(TPP)(THF)(畏(1)-ONO2) is stable in the presence of THF vapors (鈭5 mm), but it loses this ligand upon high vacuum pumping at RT. When L = dimethylsulfide (DMS), the nitrato complex is stable only to 鈭-30 掳C. Reactions of II with the N-donor ligands NH3, pyridine, or 1-methylimidazole are more complex. With these ligands, the nitrato complexes Mn(III)(TPP)(L)(畏(1)-ONO2) and the cationic complexes [Mn(TPP)(L)2](+) coexist in the layer at room temperature, the latter formed as a result of NO3(-) displacement when L is in excess. PMID:25369232

  19. 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.

  20. 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.

  1. Charge transfer vibronic transitions in uranyl tetrachloride compounds

    SciTech Connect

    Liu, Guokui; Deifel, Nicholas P.; Cahill, Christopher L.; Zhurov, Vladimir V.; Pinkerton, A. Alan

    2012-01-01

    The electronic and vibronic interactions of uranyl (UO鈧)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蟽 ground state into the f未,桅 orbitals of uranyl. The Huang鈥揜hys 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鈥揅ondon 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. Charge transfer vibronic transitions in uranyl tetrachloride compounds;

    SciTech Connect

    Liu, G. K.; Deifel, N. P.; Cahill, C. L.

    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.

  3. Energetic lanthanide complexes: coordination chemistry and explosives applications

    NASA Astrophysics Data System (ADS)

    Manner, V. W.; Barker, B. J.; Sanders, V. E.; Laintz, K. E.; Scott, B. L.; Preston, D. N.; Sandstrom, M.; Reardon, B. L.

    2014-05-01

    Metals are generally added to organic molecular explosives in a heterogeneous composite to improve overall heat and energy release. In order to avoid creating a mixture that can vary in homogeneity, energetic organic molecules can be directly bonded to high molecular weight metals, forming a single metal complex with Angstrom-scale separation between the metal and the explosive. To probe the relationship between the structural properties of metal complexes and explosive performance, a new series of energetic lanthanide complexes has been prepared using energetic ligands such as NTO (5-nitro-2,4-dihydro-1,2,4-triazole-3-one). These are the first examples of lanthanide NTO complexes where no water is coordinated to the metal, demonstrating novel control of the coordination environment. The complexes have been characterized by X-ray crystallography, NMR and IR spectroscopies, photoluminescence, and sensitivity testing. The structural and energetic properties are discussed in the context of enhanced blast effects and detection. Cheetah calculations have been performed to fine-tune physical properties, creating a systematic method for producing explosives with 'tailor made' characteristics. These new complexes will be benchmarks for further study in the field of metalized high explosives.

  4. Energetic Lanthanide Complexes: Coordination Chemistry and Explosives Applications

    NASA Astrophysics Data System (ADS)

    Manner, Virginia; Barker, Beau; Sanders, Eric; Laintz, Kenneth; Scott, Brian; Preston, Daniel; Sandstrom, Mary; Reardon, Bettina

    2013-06-01

    Metals are generally added to organic molecular explosives in a heterogeneous composite to improve overall heat and energy release. In order to avoid creating a mixture that can vary in homogeneity, energetic organic molecules can be directly bonded to high molecular weight metals, forming a single metal complex with Angstrom-scale separation between the metal and the explosive. To probe the relationship between the structural properties of metal complexes and explosive performance, a new series of energetic lanthanide complexes has been prepared using energetic ligands such as NTO (5-nitro-2,4-dihydro-1,2,4-triazole-3-one). These are the first examples of lanthanide NTO complexes where no water is coordinated to the metal, demonstrating novel control of the coordination environment. The complexes have been characterized by X-ray crystallography, NMR and IR spectroscopies, photoluminescence, and sensitivity testing. The structural and energetic properties are discussed in the context of enhanced blast effects and detection. Cheetah calculations have been performed to fine-tune physical properties, creating a systematic method for producing explosives with ``tailor made'' characteristics. These new complexes will be benchmarks for further study in the field of metalized high explosives.

  5. 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

  6. Giant regular polyhedra from calixarene carboxylates and uranyl

    PubMed Central

    Pasquale, Sara; Sattin, Sara; Escudero-Ad醤, Eduardo C.; Mart韓ez-Belmonte, Marta; de Mendoza, Javier

    2012-01-01

    Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO22+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components. PMID:22510690

  7. Structural classification of metal complexes with three-coordinate centres.

    PubMed

    Davis, Timothy L; Watts, Joshua L; Brown, Kenneth J; Hewage, Jeewantha S; Treleven, Alexander R; Lindeman, Sergey V; Gardinier, James R

    2015-09-21

    Attempts to describe the geometry about three-coordinate silver(i) complexes have proven difficult because interatomic angles generally vary wildly and there is no adequate or readily available classification system found in the literature. A search of the Cambridge Structural Database shows that complexes formed between any metal centre and three non-metal donors (18 001 examples) usually adopt geometries that are quite different than ideal 'textbook' extremes of either trigonal planar (~4% with ? = ? = ? = 120 2), T-shaped (~0.05% with ? = 180 2, ? = ? = 90 2), or trigonal pyramidal (~0.3% with ? = ? = ? = 110 2). Moreover, there are multiple variations of "Y-type" and "other" shapes that require elaboration. Thus, to assist in future structural descriptions, we developed a classification system that spans all known and yet-to-be-discovered three-coordinate geometries. A spreadsheet has also been constructed that utilizes the "shape-space" approach to extract the structural description from a user input of three angles about a tri-coordinate centre and the number of atoms in a plane. The structures of two silver(i) complexes of new N-donor ligands p-NH2C6H4C6H4CH(pz = pyrazol-1-yl)2, L1, and 2-ferrocenyl-4,5-di(2-pyridyl)imidazole, L2, illustrate the utility of this classification system. PMID:26256522

  8. In vacuo formation of peptide-metal coordination complexes

    NASA Astrophysics Data System (ADS)

    McAlister, Graeme C.; Kiessel, Sharon E. B.; Coon, Joshua J.

    2008-10-01

    Here we report on the reaction of rhenate anions (ReO3-) with multiply protonated peptide cations in a quadrupole linear ion trap mass spectrometerE These reactions effect the formation of an anion-cation complex that, upon collisional activation, dissociates along the peptide backbone rather than by displacement of the anion. Cleavage of the peptide backbone, with anion retention, leads us to conclude the anion-cation complex must be tightly bound, most probably through coordination chemistry. We describe this chemistry and detail the possible application of such ion attachment reactions to the characterization of intact proteins.

  9. Modulation of the coordination environment: a convenient approach to tailor magnetic anisotropy in seven coordinate Co(ii) complexes.

    PubMed

    Dey, Mamon; Dutta, Snigdha; Sarma, Bipul; Deka, Ramesh Ch; Gogoi, Nayanmoni

    2015-12-24

    The possibility of controlling magnetic anisotropy by tuning contribution of second order perturbation to spin-orbit coupling through modulation of the coordination environment is investigated. Subtle variation of the coordination environment triggers a remarkable deviation in the axial zero field splitting parameter of seven coordinate Co(ii) complexes. PMID:26568254

  10. The Reactivity Patterns of Low-Coordinate Iron Hydride Complexes

    PubMed Central

    Yu, Ying; Sadique, Azwana R.; Smith, Jeremy M.; Dugan, Thomas R.; Cowley, Ryan E.; Brennessel, William W.; Flaschenriem, Christine J.; Bill, Eckhard; Cundari, Thomas R.; Holland, Patrick L.

    2008-01-01

    We report a survey of the reactivity of the first isolable iron-hydride complexes with a coordination number less than five. The high-spin iron(II) complexes [(?-diketiminate)Fe(?-H)]2 react rapidly with representative cyanide, isocyanide, alkyne, N2, alkene, diazene, azide, CO2, carbodiimide and Br鴑sted acid containing substrates. The reaction outcomes fall into three categories: (1) addition of Fe-H across a multiple bond of the substrate, (2) reductive elimination of H2 to form iron(I) products, and (3) protonation of the hydride to form iron(II) products. The products include imide, isocyanide, vinyl, alkyl, azide, triazenido, benzo[c]cinnoline, amidinate, formate, and hydroxo complexes. These results expand the range of known bond transformations at iron complexes. Additionally, they give insight into the elementary transformations that may be possible at the iron-molybdenum cofactor of nitrogenases, which may have hydride ligands on high-spin, low coordinate metal atoms. PMID:18444648

  11. Uranyl peroxide closed clusters containing topological squares

    SciTech Connect

    Unruh, Daniel K.; Burtner, Alicia; Pressprich, Laura; Sigmon, Ginger E.; Burns, Peter C

    2010-01-01

    Four self-assembling clusters of uranyl peroxide polyhedra have been formed in alkaline aqueous solutions and structurally characterized. These clusters consist of 28, 30, 36 and 44 uranyl polyhedra and exhibit complex new topologies. Each has a structure that contains topological squares, pentagons and hexagons. Analysis of possible topologies within boundary constraints indicates a tendency for adoption of higher symmetry topologies in these cases. Small angle X-ray scattering data demonstrated that crystals of one of these clusters can be dissolved in ultrapure water and that the clusters remain intact for at least several days.

  12. 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

  13. Tuning coordination in s-block carbazol-9-yl complexes.

    PubMed

    Ortu, Fabrizio; Moxey, Graeme J; Blake, Alexander J; Lewis, William; Kays, Deborah L

    2015-04-27

    1,3,6,8-Tetra-tert-butylcarbazol-9-yl and 1,8-diaryl-3,6-di(tert-butyl)carbazol-9-yl ligands have been utilized in the synthesis of potassium and magnesium complexes. The potassium complexes (1,3,6,8-tBu4carb)K(THF)4 (1; carb = C12H4N), [(1,8-Xyl2-3,6-tBu2carb)K(THF)]2 (2; Xyl = 3,5-Me2C6H3) and (1,8-Mes2-3,6-tBu2carb)K(THF)2 (3; Mes = 2,4,6-Me3C6H2) were reacted with MgI2 to give the Hauser bases 1,3,6,8-tBu4carbMgI(THF)2 (4) and 1,8-Ar2-3,6-tBu2carbMgI(THF) (Ar = Xyl 5, Ar = Mes 6). Structural investigations of the potassium and magnesium derivatives highlight significant differences in the coordination motifs, which depend on the nature of the 1- and 8-substituents: 1,8-di(tert-butyl)-substituted ligands gave 蟺-type compounds (1 and 4), in which the carbazolyl ligand acts as a multi-hapto donor, with the metal cations positioned below the coordination plane in a half-sandwich conformation, whereas the use of 1,8-diaryl substituted ligands gave 蟽-type complexes (2 and 6). Space-filling diagrams and percent buried volume calculations indicated that aryl-substituted carbazolyl ligands offer a steric cleft better suited to stabilization of low-coordinate magnesium complexes. PMID:25783772

  14. Tuning Coordination in s-Block Carbazol-9-yl Complexes

    PubMed Central

    Ortu, Fabrizio; Moxey, Graeme J; Blake, Alexander J; Lewis, William; Kays, Deborah L

    2015-01-01

    1,3,6,8-Tetra-tert-butylcarbazol-9-yl and 1,8-diaryl-3,6-di(tert-butyl)carbazol-9-yl ligands have been utilized in the synthesis of potassium and magnesium complexes. The potassium complexes (1,3,6,8-tBu4carb)K(THF)4 (1; carb=C12H4N), [(1,8-Xyl2-3,6-tBu2carb)K(THF)]2 (2; Xyl=3,5-Me2C6H3) and (1,8-Mes2-3,6-tBu2carb)K(THF)2 (3; Mes=2,4,6-Me3C6H2) were reacted with MgI2 to give the Hauser bases 1,3,6,8-tBu4carbMgI(THF)2 (4) and 1,8-Ar2-3,6-tBu2carbMgI(THF) (Ar=Xyl 5, Ar=Mes 6). Structural investigations of the potassium and magnesium derivatives highlight significant differences in the coordination motifs, which depend on the nature of the 1- and 8-substituents: 1,8-di(tert-butyl)-substituted ligands gave 蟺-type compounds (1 and 4), in which the carbazolyl ligand acts as a multi-hapto donor, with the metal cations positioned below the coordination plane in a half-sandwich conformation, whereas the use of 1,8-diaryl substituted ligands gave 蟽-type complexes (2 and 6). Space-filling diagrams and percent buried volume calculations indicated that aryl-substituted carbazolyl ligands offer a steric cleft better suited to stabilization of low-coordinate magnesium complexes. PMID:25783772

  15. {sup 13}C and {sup 17}O NMR binding constant studies of uranyl carbonate complexes in near-neutral aqueous solution. Yucca Mountain Project Milestone Report 3351

    SciTech Connect

    Clark, D.L.; Newton, T.W.; Palmer, P.D.; Zwick, B.D.

    1995-01-01

    Valuable structural information, much of it unavailable by other methods, can be obtained about complexes in solution through NMR spectroscopy. From chemical shift and intensity measurements of complexed species, NMR can serve as a species-specific structural probe for molecules in solution and can be used to validate thermodynamic constants used in geochemical modeling. Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy has been employed to study the speciation of uranium(VI) ions in aqueous carbonate solutions as a function of pH, ionic strength, carbonate concentration, uranium concentration, and temperature. Carbon-13 and oxygen-17 NMR spectroscopy were used to monitor the fractions, and hence thermodynamic binding constants of two different uranyl species U0{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} and (UO{sub 2}){sub 3}(CO{sub 3}){sub 6}{sup 6{minus}} in aqueous solution. Synthetic buffer solutions were prepared under the ionic strength conditions used in the NMR studies in order to obtain an accurate measure of the hydrogen ion concentration, and a discussion of pH = {minus}log(a{sub H}{sup +}) versus p[H] = {minus}log[H+] is provided. It is shown that for quantitative studies, the quantity p[H] needs to be used. Fourteen uranium(VI) binding constants recommended by the OECD NEA literature review were corrected to the ionic strengths employed in the NMR study using specific ion interaction theory (SIT), and the predicted species distributions were compared with the actual species observed by multinuclear NMR. Agreement between observed and predicted stability fields is excellent. This establishes the utility of multinuclear NMR as a species-specific tool for the study of the actinide carbonate complexation constants, and serves as a means for validating the recommendations provided by the OECD NEA.

  16. In vacuo formation of peptide-metal coordination complexes.

    PubMed

    McAlister, Graeme C; Kiessel, Sharon E B; Coon, Joshua J

    2008-10-01

    Here we report on the reaction of rhenate anions (ReO(3) (-)) with multiply protonated peptide cations in a quadrupole linear ion trap mass spectrometer. These reactions effect the formation of an anion-cation complex that, upon collisional activation, dissociates along the peptide backbone rather than by displacement of the anion. Cleavage of the peptide backbone, with anion retention, leads us to conclude the anion-cationcomplexmust be tightly bound, most probably through coordination chemistry. We describe this chemistry and detail the possible application of such ion attachment reactions to the characterization of intact proteins. PMID:19424441

  17. In vacuo formation of peptide杕etal coordination complexes

    PubMed Central

    McAlister, Graeme C.; Kiessel, Sharon E.B.; Coon, Joshua J.

    2009-01-01

    Here we report on the reaction of rhenate anions (ReO3?) with multiply protonated peptide cations in a quadrupole linear ion trap mass spectrometer. These reactions effect the formation of an anion朿ation complex that, upon collisional activation, dissociates along the peptide backbone rather than by displacement of the anion. Cleavage of the peptide backbone, with anion retention, leads us to conclude the anion朿ationcomplexmust be tightly bound, most probably through coordination chemistry. We describe this chemistry and detail the possible application of such ion attachment reactions to the characterization of intact proteins. PMID:19424441

  18. Design of magnetic coordination complexes for quantum computing.

    PubMed

    Arom, Guillem; Aguil, David; Gamez, Patrick; Luis, Fernando; Roubeau, Olivier

    2012-01-21

    A very exciting prospect in coordination chemistry is to manipulate spins within magnetic complexes for the realization of quantum logic operations. An introduction to the requirements for a paramagnetic molecule to act as a 2-qubit quantum gate is provided in this tutorial review. We propose synthetic methods aimed at accessing such type of functional molecules, based on ligand design and inorganic synthesis. Two strategies are presented: (i) the first consists in targeting molecules containing a pair of well-defined and weakly coupled paramagnetic metal aggregates, each acting as a carrier of one potential qubit, (ii) the second is the design of dinuclear complexes of anisotropic metal ions, exhibiting dissimilar environments and feeble magnetic coupling. The first systems obtained from this synthetic program are presented here and their properties are discussed. PMID:21818467

  19. Coordination Chemistry of Homoleptic Actinide(IV)-Thiocyanate Complexes.

    PubMed

    Carter, Tyler J; Wilson, Richard E

    2015-10-26

    The synthesis, X-ray crystal structure, vibrational and optical spectroscopy for the eight-coordinate thiocyanate compounds, [Et4 N]4 [Pu(IV) (NCS)8 ], [Et4 N]4 [Th(IV) (NCS)8 ], and [Et4 N]4 [Ce(III) (NCS)7 (H2 O)] are reported. Thiocyanate was found to rapidly reduce plutonium to Pu(III) in acidic solutions (pH<1) in the presence of NCS(-) . The optical spectrum of [Et4 N][SCN] containing Pu(III) solution was indistinguishable from that of aquated Pu(III) suggesting that inner-sphere complexation with [Et4 N][SCN] does not occur in water. However, upon concentration, the homoleptic thiocyanate complex [Et4 N]4 [Pu(IV) (NCS)8 ] was crystallized when a large excess of [Et4 N][NCS] was present. This compound, along with its U(IV) analogue, maintains inner-sphere thiocyanate coordination in acetonitrile based on the observation of intense ligand-to-metal charge-transfer bands. Spectroscopic and crystallographic data do not support the interaction of the metal orbitals with the ligand ? system, but support an enhanced An(IV) -NCS interaction, as the Lewis acidity of the metal ion increases from Th to Pu. PMID:26493880

  20. Similarities between GCS and human motor cortex: complex movement coordination

    NASA Astrophysics Data System (ADS)

    Rodr铆guez, Jose A.; Macias, Rosa; Molgo, Jordi; Guerra, Dailos

    2014-07-01

    The "Gran Telescopio de Canarias" (GTC1) is an optical-infrared 10-meter segmented mirror telescope at the ORM observatory in Canary Islands (Spain). The GTC control system (GCS), the brain of the telescope, is is a distributed object & component oriented system based on RT-CORBA and it is responsible for the management and operation of the telescope, including its instrumentation. On the other hand, the Human motor cortex (HMC) is a region of the cerebrum responsible for the coordination of planning, control, and executing voluntary movements. If we analyze both systems, as far as the movement control of their mechanisms and body parts is concerned, we can find extraordinary similarities in their architectures. Both are structured in layers, and their functionalities are comparable from the movement conception until the movement action itself: In the GCS we can enumerate the Sequencer high level components, the Coordination libraries, the Control Kit library and the Device Driver library as the subsystems involved in the telescope movement control. If we look at the motor cortex, we can also enumerate the primary motor cortex, the secondary motor cortices, which include the posterior parietal cortex, the premotor cortex, and the supplementary motor area (SMA), the motor units, the sensory organs and the basal ganglia. From all these components/areas we will analyze in depth the several subcortical regions, of the the motor cortex, that are involved in organizing motor programs for complex movements and the GCS coordination framework, which is composed by a set of classes that allow to the high level components to transparently control a group of mechanisms simultaneously.

  1. The Anaphase-promoting Complex Coordinates Initiation of Lens Differentiation

    PubMed Central

    Wu, George; Glickstein, Sara; Liu, Weijun; Fujita, Takeo; Li, Wenqi; Yang, Qi; Duvoisin, Robert

    2007-01-01

    Lens development requires the precise coordination of cell division and differentiation. The mechanisms by which the differentiation program is initiated after cell cycle arrest remains not well understood. Cyclin-dependent kinase inhibitors (CKIs), such as p15 and p21, have been suggested to be critical components that inhibit G1 progression and therefore, their activation is necessary for quiescence and important for the onset of differentiation. Regulation of p15 and p21 is principally governed by transforming growth factor (TGF)-?杝ignaling pathway. We have identified that Cdh1/APC, a critical ubiquitin protein ligase, plays an important role in regulating lens differentiation by facilitating TGF-?杋nduced degradation of SnoN, a transcriptional corepressor that needs to be removed for transcriptional activation of p15 and p21. The depletion of Cdh1 by RNA interference attenuates the TGF-?杕ediated induction of p15 and p21 and significantly blocks lens differentiation. Expression of nondegradable SnoN also noticeably attenuates lens induction. Furthermore, we have shown that Cdh1 and SnoN form a complex at the onset of lens differentiation. In vivo histological analysis confirms our biochemical and genetic results. Thus, Cdh1/APC is crucial to the coordination of cell cycle progression and the initiation of lens differentiation through mediating TGF-?杝ignaling-induced destruction of SnoN. PMID:17215516

  2. Uranyl-water-containing complexes: solid-state UV-MALDI mass spectrometric and IR spectroscopic approach for selective quantitation.

    PubMed

    Ivanova, Bojidarka; Spiteller, Michael

    2014-01-01

    Since primary environmental concept for long storage of nuclear waste involved assessment of water in uranium complexes depending on migration processes, the paper emphasized solid-state matrix-assisted laser desorption/ionization (MALDI) mass spectrometric (MS) and IR spectroscopic determination of UO2(NO3)26H2O; UO2(NO3)23H2O, ?-, ?-, and ?-UO3 modifications; UO3穢H2O (x?=?1 or 2); UO3稨2O, described chemically as UO2(OH)2, ?- and ?-UO2(OH)2 modifications; and UO42H2O, respectively. Advantages and limitation of vibrational spectroscopic approach are discussed, comparing optical spectroscopic data and crystallographic ones. Structural similarities occurred in ?-? modifications of UO3, and UO2(OH)2 compositions are analyzed. Selective speciation achieved by solid-state mass spectrometry is discussed both in terms of its analytical contribution for environmental quality assurance and assessment of radionuclides, and fundamental methodological interest related the mechanistic complex water exchange of UO3稨2O forms in the gas phase. In addition to high selectivity and precision, UV-MALDI-MS, employing an Orbitrap analyzer, was a method that provided fast steps that limited sample pretreatment techniques for direct analysis including imaging. Therefore, random and systematic errors altering metrology and originating from the sample pretreatment stages in the widely implemented analytical protocols for environmental sampling determination of actinides are significantly reduced involving the UV-MALDI-Orbitrap-MS method. The method of quantum chemistry is utilized as well to predict reliably the thermodynamics and nature of U-O bonds in uranium species in gas and condensed phases. PMID:23942998

  3. Micro practices of coordination based on complex adaptive systems: user needs and strategies for coordinating public health in Denmark

    PubMed Central

    Wittrup, Inge; Burau, Viola

    2015-01-01

    Introduction Many highly formalised approaches to coordination poorly fit public health and recent studies call for coordination based on complex adaptive systems. Our contribution is two-fold. Empirically, we focus on public health, and theoretically we build on the patient perspective and treat coordination as a process of contingent, two-level negotiations of user needs. Theory and Methods The paper draws on the concept of user needs-based coordination and sees coordination as a process, whereby needs emerging from the life world of the user are made amenable to the health system through negotiations. The analysis is based on an explorative case study of a health promotion initiative in Denmark. It adopts an anthropological qualitative approach and uses a range of qualitative data. Results The analysis identifies four strategies of coordination: the coordinator focusing on the individual user or on relations with other professionals; and the manager coaching the coordinator or providing structural support. Crucially, the coordination strategies by management remain weak as they do not directly relate to specific user needs. Discussion In process of bottom-up negotiations user needs become blurred and this is especially a challenge for management. The study therefore calls for an increased focus on the level nature of negotiations to bridge the gap that currently weakens coordination strategies by management. PMID:26528097

  4. Complex Interdependence Regulates Heterotypic Transcription Factor Distribution and Coordinates Cardiogenesis.

    PubMed

    Luna-Zurita, Luis; Stirnimann, Christian U; Glatt, Sebastian; Kaynak, Bogac L; Thomas, Sean; Baudin, Florence; Samee, Md Abul Hassan; He, Daniel; Small, Eric M; Mileikovsky, Maria; Nagy, Andras; Holloway, Alisha K; Pollard, Katherine S; M黮ler, Christoph W; Bruneau, Benoit G

    2016-02-25

    Transcription factors (TFs) are thought to function with partners to achieve specificity and precise quantitative outputs. In the developing heart, heterotypic TF interactions, such as between the T-box TF燭BX5 and the homeodomain TF NKX2-5, have been爌roposed as a mechanism for human congenital heart defects. We report extensive and complex爄nterdependent genomic occupancy of TBX5, NKX2-5, and the zinc finger TF GATA4 coordinately controlling cardiac gene expression, differentiation, and morphogenesis. Interdependent binding serves not only to co-regulate gene expression but also to prevent TFs from distributing to ectopic loci and activate lineage-inappropriate genes. We define preferential motif arrangements for TBX5 and NKX2-5 cooperative binding sites, supported at the atomic level by their co-crystal structure bound to DNA, revealing a direct interaction between the two factors and induced DNA bending. Complex interdependent binding mechanisms reveal tightly regulated TF genomic distribution and define a combinatorial logic for heterotypic TF regulation of differentiation. PMID:26875865

  5. Cytotoxicity of Cyclometalated Platinum Complexes Based on Tridentate NCN and CNN-coordinating ligands: Remarkable Coordination Dependence

    PubMed Central

    Vezzu, Dileep A. k.; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

    2014-01-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the N?C?N-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the C?N?N-coordinated platinum complex based on 6-phenyl-2,2?-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by N?C?N- and C?N?N-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the N?C?N-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis was studied by western blot analysis and the activation of PARP via caspase 7 was observed. PMID:24531534

  6. Cytotoxicity of cyclometalated platinum complexes based on tridentate NCN and CNN-coordinating ligands: remarkable coordination dependence.

    PubMed

    Vezzu, Dileep A K; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

    2014-05-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the N^C^N-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the C^N^N-coordinated platinum complex based on 6-phenyl-2,2'-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by N^C^N- and C^N^N-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the N^C^N-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed that the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis were studied by western blot analysis and the activation of PARP via caspase 7 was observed. PMID:24531534

  7. 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.

  8. Uranyl incorporation in natural calcite.

    SciTech Connect

    Kelly, S. D.; Newville, M. G.; Cheng, L.; Kemner, K. M.; Sutton, S. R.; Fenter, P.; Sturchio, N. C.; Spotl, C.; Environmental Research; Univ. of Chicago; Univ. of Illiois at Chicago; Univ. of Innsbruck

    2003-01-01

    The occurrence of trace amounts of uranyl in natural calcite has posed a long-standing problem in crystal chemistry because of speculation that the size and shape of the uranyl ion may preclude its incorporation in a stable lattice position in calcite. This also defines an important environmental problem because of its bearing on the transport and sequestration of uranyl released from nuclear facilities and uranium mining operations. Calcite is a nearly ubiquitous mineral in soils and groundwater aquifers. X-ray absorption spectroscopy and X-ray fluorescence microprobe studies of uranium in relatively U-rich {approx}13700-year-old calcite from a speleothem in northernmost Italy indicate substitution of uranyl for a calcium and two adjacent carbonate ions in calcite. These new data imply that uranyl has a stable lattice position in natural calcite, indicating that it may be reliably sequestered in calcite over long time scales.

  9. Ionothermal synthesis of uranyl compounds that incorporate imidazole derivatives

    SciTech Connect

    Wylie, Ernest M.; Dustin, Megan K.; Smith, Jeremy S.; Burns, Peter C.

    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.

  10. Uranyl formate monohydrate spectroscopy

    SciTech Connect

    Porter, J.T. II; Muller, C.H. III; West, W.P.; Malley, M.M.

    1983-10-01

    We report the fluorescence excitation and emission spectra of normal and isotopically labeled uranyl formate monohydrate powder, UO/sub 2/(HCOO)/sub 2/.H/sub 2/O, at 4.2/sup 0/K. Dual fluorescence from the two lowest excited states, I and II, occurs in this compound giving rise to a temperature-dependent lifetime. The lowest vibronic levels are assigned on the basis of the observed oxygen and uranium isotope shifts. The unusual activity and relative frequencies of the symmetric and asymmetric O-U-O stretches in the excited state and can be successfully predicted with the addition of a bond-bond interaction term in addition to the usual valence bond potential. The kinetics of nonresonant energy transfer between isotopic /sup x/OU/sup y/O/sup +2/ antitraps and the U/sup 16/O/sub 2//sup +2/ lattice were measured over the range from 1.7 to 4.2/sup 0/K. The observed rates are in agreement with a quadrupole-quadrupole coupling mechanism accompanied by one and two phonon processes which compensate for the energy defect. The asymmetric lineshapes, broader linewidths and tenfold reduction of absorption intensity for the U/sup 16/O/sub 2//sup +2/ lattice compared to the isolated isotopically doped uranyl ions are attributed to the collective nature of the excited state for the majority species.

  11. Cation templating and electronic structure effects in uranyl cage clusters probed by the isolation of peroxide-bridged uranyl dimers.

    PubMed

    Qiu, Jie; Vlaisavljevich, Bess; Jouffret, Laurent; Nguyen, Kevin; Szymanowski, Jennifer E S; Gagliardi, Laura; Burns, Peter C

    2015-05-01

    The self-assembly of uranyl peroxide polyhedra into a rich family of nanoscale cage clusters is thought to be favored by cation templating effects and the pliability of the intrinsically bent U-O2-U dihedral angle. Herein, the importance of ligand and cationic effects on the U-O2-U dihedral angle were explored by studying a family of peroxide-bridged dimers of uranyl polyhedra. Four chemically distinct peroxide-bridged uranyl dimers were isolated that contain combinations of pyridine-2,6-dicarboxylate, picolinate, acetate, and oxalate as coordinating ligands. These dimers were synthesized with a variety of counterions, resulting in the crystallographic characterization of 15 different uranyl dimer compounds containing 17 symmetrically distinct dimers. Eleven of the dimers have U-O2-U dihedral angles in the expected range from 134.0 to 156.3; however, six have 180 U-O2-U dihedral angles, the first time this has been observed for peroxide-bridged uranyl dimers. The influence of crystal packing, countercation linkages, and ?-? stacking impact the dihedral angle. Density functional theory calculations indicate that the ligand does not alter the electronic structure of these systems and that the U-O2-U bridge is highly pliable. Less than 3 kcal穖ol(-1) is required to bend the U-O2-U bridge from its minimum energy configuration to a dihedral angle of 180. These results suggest that the energetic advantage of bending the U-O2-U dihedral angle of a peroxide-bridged uranyl dimer is at most a modest factor in favor of cage cluster formation. The role of counterions in stabilizing the formation of rings of uranyl ions, and ultimately their assembly into clusters, is at least as important as the energetic advantage of a bent U-O2-U interaction. PMID:25868048

  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. 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

  14. Barium uranyl diphosphonates

    SciTech Connect

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

    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. [Complex chronic care situations and socio-health coordination].

    PubMed

    Morilla Herrera, Juan Carlos; Morales Asencio, Jos Miguel; Kaknani, Shakira; Garc韆 Mayor, Silvia

    2016-01-01

    Patient-centered healthcare is currently one of the most pursued goals in health services. It is necessary to ensure a sufficient level of cooperative and coordinated work between different providers and settings, including family and social and community resources. Clinical integration occurs when the care provided by health professionals and providers is integrated into a single coherent process through different professions using shared guidelines and protocols. Such coordination can be developed at three levels: macro, which involves the integration of one or more of the three basic elements that support health care (the health plan, primary care and specialty care), with the aim of reducing fragmentation of care; meso, where health and social services are coordinated to provide comprehensive care to elderly and chronic patients; and micro, aimed to improve coordination in individual patients and caregivers. The implementation of new roles, such as Advanced Practice Nursing, along with improvements in family physicians' problem-solving capacity in certain processes, or modifying the place of provision of certain services are key to ensure services adapted to the requirements of chronic patients. PMID:26363991

  16. 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.

  17. Coordinating complex decision support activities across distributed applications

    NASA Technical Reports Server (NTRS)

    Adler, Richard M.

    1994-01-01

    Knowledge-based technologies have been applied successfully to automate planning and scheduling in many problem domains. Automation of decision support can be increased further by integrating task-specific applications with supporting database systems, and by coordinating interactions between such tools to facilitate collaborative activities. Unfortunately, the technical obstacles that must be overcome to achieve this vision of transparent, cooperative problem-solving are daunting. Intelligent decision support tools are typically developed for standalone use, rely on incompatible, task-specific representational models and application programming interfaces (API's), and run on heterogeneous computing platforms. Getting such applications to interact freely calls for platform independent capabilities for distributed communication, as well as tools for mapping information across disparate representations. Symbiotics is developing a layered set of software tools (called NetWorks! for integrating and coordinating heterogeneous distributed applications. he top layer of tools consists of an extensible set of generic, programmable coordination services. Developers access these services via high-level API's to implement the desired interactions between distributed applications.

  18. Bidentate and tridentate metal-ion coordination states within ternary complexes of RB69 DNA polymerase

    SciTech Connect

    Xia, Shuangluo; Eom, Soo Hyun; Konigsberg, William H.; Wang, Jimin

    2012-02-21

    Two divalent metal ions are required for primer-extension catalyzed by DNA polymerases. One metal ion brings the 3'-hydroxyl of the primer terminus and the {alpha}-phosphorus atom of incoming dNTP together for bond formation so that the catalytically relevant conformation of the triphosphate tail of the dNTP is in an {alpha},{beta},{gamma}-tridentate coordination complex with the second metal ion required for proper substrate alignment. A probable base selectivity mechanism derived from structural studies on Dpo4 suggests that the inability of mispaired dNTPs to form a substrate-aligned, tridentate coordination complex could effectively cause the mispaired dNTPs to be rejected before catalysis. Nevertheless, we found that mispaired dNTPs can actually form a properly aligned tridentate coordination complex. However, complementary dNTPs occasionally form misaligned complexes with mutant RB69 DNA polymerases (RB69pols) that are not in a tridentate coordination state. Here, we report finding a {beta},{gamma}-bidentate coordination complex that contained the complementary dUpNpp opposite dA in the structure of a ternary complex formed by the wild type RB69pol at 1.88 {angstrom} resolution. Our observations suggest that several distinct metal-ion coordination states can exist at the ground state in the polymerase active site and that base selectivity is unlikely to be based on metal-ion coordination alone.

  19. Equilibrium between Different Coordination Geometries in Oxidovanadium(IV) Complexes

    ERIC Educational Resources Information Center

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

    2015-01-01

    In this laboratory activity, the equilibrium between square pyramidal and octahedral V(IV)O[superscript 2+] complexes is described. We propose a set of experiments to synthesize and characterize two types of V(IV)O[superscript 2+] complexes. The experiment allows great flexibility and may be effectively used at a variety of levels and the activity鈥

  20. Equilibrium between Different Coordination Geometries in Oxidovanadium(IV) Complexes

    ERIC Educational Resources Information Center

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

    2015-01-01

    In this laboratory activity, the equilibrium between square pyramidal and octahedral V(IV)O[superscript 2+] complexes is described. We propose a set of experiments to synthesize and characterize two types of V(IV)O[superscript 2+] complexes. The experiment allows great flexibility and may be effectively used at a variety of levels and the activity

  1. 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

  2. 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 & Deligni鑢es, 2012). Alternatively, we propose that complexity matching is a result of local phase adjustments during coordination (Deligni鑢es & 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. PMID:25798782

  3. Synthesis and Characterization of Templated Ion Exchange Resins for the Selective Complexation of Actinide Ions

    SciTech Connect

    Uy, O. Manual

    2001-03-01

    The purpose of this research is to develop a polymeric extractant for the selective complexation of uranyl ions (and subsequently other actinyl and actinide ions) from aqueous solutions (lakes, streams, waste tanks and even body fluids). Chemical insights into what makes a good complexation site will be used to synthesize reagents tailor-made for the complexation of uranyl and other actinide ions. These insights, derived from studies of molecular recognition include ion coordination number and geometry, ionic size and ionic shape, as well as ion to ligand thermodynamic affinity. Selectivity for a specific actinide ion will be obtained by providing the polymers with cavities lined with complexing ligands so arranged as to match the charge, coordination number, coordination geometry, and size of the actinide metal ion. These cavity-containing polymers will be produced by using a specific ion (or surrogate) as a template around which monomeric complexing ligands will be polymerized. The complexing ligands will be ones containing functional groups known to form stable complexes with a specific ion and less stable complexes with other cations. Prior investigator's approaches for making templated resins for metal ions have had marginal success. We have extended and amended these methodologies in our work with Pb(II) and uranyl ion, by changing the order of the steps, by the inclusion of sonication, by using higher complex loading, and the selection of functional groups with better complexation constants. This has resulted in significant improvements to selectivity. The unusual shape of the uranyl ion suggests that this approach will result in even greater selectivities than already observed for Pb(II). Preliminary data obtained for uranyl templated polymers shows unprecedented selectivity and has resulted in the first ion selective electrode for uranyl ion.

  4. Proton exchange in acid-base complexes induced by reaction coordinates with heavy atom motions

    NASA Astrophysics Data System (ADS)

    Alavi, Saman; Taghikhani, Mahdi

    2012-06-01

    We extend previous work on nitric acid-ammonia and nitric acid-alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid-strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are <400 cm-1. This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm-1. Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

  5. Solid state and aqueous behavior of uranyl peroxide cage clusters

    NASA Astrophysics Data System (ADS)

    Pellegrini, Kristi Lynn

    Uranyl peroxide cage clusters include a large family of more than 50 published clusters of a variety of sizes, which can incorporate various ligands including pyrophosphate and oxalate. Previous studies have reported that uranyl clusters can be used as a method to separate uranium from a solid matrix, with potential applications in reprocessing of irradiated nuclear fuel. Because of the potential applications of these novel structures in an advanced nuclear fuel cycle and their likely presence in areas of contamination, it is important to understand their behavior in both solid state and aqueous systems, including complex environments where other ions are present. In this thesis, I examine the aqueous behavior of U24Pp 12, as well as aqueous cluster systems with added mono-, di-, and trivalent cations. The resulting solutions were analyzed using dynamic light scattering and ultra-small angle X-ray scattering to evaluate the species in solution. Precipitates of these systems were analyzed using powder X-ray diffraction, X-ray fluorescence spectrometry, and Raman spectroscopy. The results of these analyses demonstrate the importance of cation size, charge, and concentration of added cations on the aqueous behavior of uranium macroions. Specifically, aggregates of various sizes and shapes form rapidly upon addition of cations, and in some cases these aggregates appear to precipitate into an X-ray amorphous material that still contains U24Pp12 clusters. In addition, I probe aggregation of U24Pp12 and U60, another uranyl peroxide cage cluster, in mixed solvent water-alcohol systems. The aggregation of uranyl clusters in water-alcohol systems is a result of hydrogen bonding with polar organic molecules and the reduction of the dielectric constant of the system. Studies of aggregation of uranyl clusters also allow for comparison between the newer uranyl polyoxometalate family and century-old transition metal polyoxometalates. To complement the solution studies of uranyl cage clusters, solid state analyses of U24Pp12 are presented, including single crystal X-ray diffraction and preliminary single crystal neutron diffraction. Solid state analyses are used to probe the complicated bonding environments between U24Pp12 and crystallized counterions, giving further insight into the importance of cluster protonation and counterions in uranyl cluster systems. The combination of solid state and solution techniques provides information about the complicated nature of uranyl peroxide nanoclusters, and insight towards future applications of clusters in the advanced nuclear fuel cycle and the environment.

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

    NASA Astrophysics Data System (ADS)

    K黨n, 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.

  7. A spectroscopic study of uranyl-cytochrome b5/cytochrome c interactions

    NASA Astrophysics Data System (ADS)

    Sun, Mei-Hui; Liu, Shuang-Quan; Du, Ke-Jie; Nie, Chang-Ming; Lin, Ying-Wu

    2014-01-01

    Uranium is harmful to human health due to its radiation damage and the ability of uranyl ion (UO22+) to interact with various proteins and disturb their biological functions. Cytochrome b5 (cyt b5) is a highly negatively charged heme protein and plays a key role in mediating cytochrome c (cyt c) signaling in apoptosis by forming a dynamic cyt b5-cyt c complex. In previous molecular modeling study in combination with UV-Vis studies, we found that UO22+ is capable of binding to cyt b5 at surface residues, Glu37 and Glu43. In this study, we further investigated the structural consequences of cyt b5 and cyt c, as well as cyt b5-cyt c complex, upon uranyl binding, by fluorescence spectroscopic and circular dichroism techniques. Moreover, we proposed a uranyl binding site for cyt c at surface residues, Glu66 and Glu69, by performing a molecular modeling study. It was shown that uranyl binds to cyt b5 (KD = 10 ?M), cyt c (KD = 87 ?M), and cyt b5-cyt c complex (KD = 30 ?M) with a different affinity, which slightly alters the protein conformation and disturbs the interaction of cyt b5-cyt c complex. Additionally, we investigated the functional consequences of uranyl binding to the protein surface, which decreases the inherent peroxidase activity of cyt c. The information of uranyl-cyt b5/cyt c interactions gained in this study likely provides a clue for the mechanism of uranyl toxicity.

  8. A Bridge to Coordination Isomer Selection in Lanthanide(III) DOTA-tetraamide Complexes

    PubMed Central

    Vipond, Jeff; Woods, Mark; Zhao, Piyu; Tircso, Gyula; Ren, Jimin; Bott, Simon G.; Ogrin, Doug; Kiefer, Garry E.; Kovacs, Zoltan; Sherry, A.Dean

    2008-01-01

    Interest in macrocyclic lanthanide complexes such as DOTA is driven largely through interest in their use as contrast agents for MRI. The lanthanide tetraamide derivatives of DOTA have shown considerable promise as PARACEST agents, taking advantage of the slow water exchange kinetics of this class of complex. We postulated that water exchange in these tetraamide complexes could be slowed even further by introducing a group to sterically encumber the space above the water coordination site, thereby hindering the departure and approach of water molecules to the complex. The ligand 8O2-bridged-DOTAM was synthesized in a 34% yield from cyclen. It was found that the lanthanide complexes of this ligand did not possess a water molecule in the inner coordination sphere of the bound lanthanide. The crystal structure of the ytterbium complex revealed that distortions to the coordination sphere were induced by the steric constraints imposed on the complex by the bridging unit. The extent of the distortion was found to increase with increasing ionic radius of the lanthanide ion, eventually resulting in a complete loss of symmetry in the complex. Because this ligand system is bicyclic, the conformation of each ring in the system is constrained by that of the other, in consequence inclusion of the bridging unit in the complexes means only a twisted square antiprismatic coordination geometry is observed for complexes of 8O2-bridged-DOTAM. PMID:17295475

  9. Insertion of Trivalent Lanthanides into Uranyl Vanadate Layers and Frameworks.

    PubMed

    Wang, Yaxing; Yin, Xuemiao; Zhao, Yanyan; Gao, Yang; Chen, Lanhua; Liu, Zhiyong; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2015-09-01

    Two new uranyl vanadates have been prepared from hydrothermal reactions and structurally characterized by single-crystal X-ray diffraction. The structure of (H3O)UO2VO4 (UVO-1) consists of anionic layers containing UO2(2+) pentagonal bipyramids coordinated by edge-sharing VO5 square pyramids, with the charge balanced by interlaminar H3O(+) cations. Vanadium in (UO2)3(VO4)2(H2O)3 (UVO-2) exists as monomeric VO4 tetrahedra coordinating to UO2(2+) pentagonal bipyramids, forming a 3D uranyl(VI) vanadate framework. Similar reactions with the addition of Ln(NO3)3 (Ln = Nd, Eu) afford the three heterobimetallic lanthanide uranyl vanadate frameworks Nd(UO2)3(VO4)3(H2O)11 (NdUVO-1), Eu(UO2)3(VO4)3(H2O)10 (EuUVO-1), and Eu2(UO2)12(VO4)10(H2O)24 (EuUVO-2). In NdUVO-1 and EuUVO-1, Ln(3+) cations are inserted into the interlayer space of UVO-1 substituting for H3O(+) and further bridging adjacent layers into 3D frameworks. Similarly, EuUVO-2 adopts the same sheet topology as UVO-2, with Eu(3+) ions replacing some of the interlayer uranyl ions in UVO-2. Our work has demonstrated that uranyl vanadate extended structures are excellent hosts for further incorporation of trivalent lanthanide/actinide cations and has provided a new way to create new heterobimetallic 4f-5f and 5f-5f compounds. PMID:26292148

  10. The coordination and atom transfer chemistry of titanium porphyrin complexes

    SciTech Connect

    Hays, J.A.

    1993-11-05

    Preparation, characterization, and reactivity of ({eta}{sup 2}- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The {eta}{sup 2}- alkyne complexes are prepared by reaction of (TTP)TiCl{sub 2} with LiAlH{sub 4} in presence of alkyne. Structure of (OEP)Ti({eta}{sup 2}-Ph-C{triple_bond}C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple substitution to displace the alkyne and produce doubly substituted complexes. Structure of (TTP)Ti(4-picoline){sub 2} was also determined by XRD. Reaction of (TTP)Ti{double_bond}O with (OEP)Ti-Cl yields intermetal O/Cl exchange, which is a one-electron redox process mediated by O atom transfer. Also a zero-electron redox process mediated by atom transfer is observed when (TTP)TiCl{sub 2} is reacted with (OEP)Ti{double_bond}O.

  11. Coordination mode and reactivity of copper(II) complexes with kasugamycin.

    PubMed

    Jezowska-Bojczuk, M; Le?niak, W

    2001-06-01

    Protonation and Cu(II) coordination of kasugamycin were studied by potentiometry, UV-vis, CD, EPR, 13C NMR, and 1H NMR. Mononuclear complexes with stoichiometries ranging from CuHL to CuH(-1)L were found. The aminoamidine moiety provides the coordination site in the CuHL species. The additional axial coordination of the amino nitrogen of the aminosugar ring is present in CuL. Finally, the CuH(-1)L complex is formed as a result of a deprotonation and coordination of the hydroxyl group of the inositol ring. The non-planar arrangement of the chelate rings results in the relative stabilization of a Cu(I) species. As a consequence, Cu(I) and superoxide radicals are involved in the redox mechanism of H(2)O(2) activation by the Cu(II) complex of kasugamycin. PMID:11410229

  12. 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; Nuzhdin, Kirill; Wu, Weiqiang; Vyushkova, Mariya; Burns, Peter C.

    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.

  13. Pointing errors in strabismics: complex patterns of distorted visuomotor coordination.

    PubMed

    Fronius, M; Sireteanu, R

    1994-03-01

    Monocular eye-hand coordination was tested in a pointing experiment in the central and peripheral visual field of each eye of strabismic and anisometropic amblyopes, strabismic alternators and normal controls. In the normal controls, pointing was accurate in the central visual field. Towards the periphery, normal observers showed a varying amount of undershoot as well as increasing uncertainty. The pointing pattern was similar in the two eyes of these subjects. Increased uncertainty of pointing responses was found in most amblyopic eyes as compared to the dominant eyes. Three strabismic amblyopes and one strabismic alternator also had systematic pointing errors (i.e. systematic differences between pointing under the control of the dominant as compared to the nondominant eye). The pointing pattern was not uniform across the visual field in some of the strabismics, but was composed of areas of larger and smaller pointing errors. Larger pointing errors (i.e. larger differences between the dominant and nondominant eyes) were usually found in the central visual field. These errors were not closely related to the angle of squint. The clinical history of the strabismics seems to be an important factor for the occurrence of pointing errors. PMID:8160386

  14. Supramolecular coordination and antimicrobial activities of constructed mixed ligand complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Abou-Dobara, M. I.; Seyam, H. A.

    2013-03-01

    A novel series of copper(II) and palladium(II) with 4-derivatives benzaldehyde pyrazolone (Ln) were synthesized. The mixed ligand complexes were prepared by using 1,10-phenanthroline (Phen) as second ligand. The structure of these complexes was identified and confirm by elemental analysis, molar conductivity, UV-Vis, IR and 1H NMR spectroscopy and magnetic moment measurements as well as thermal analysis. The ligand behaves as a neutral bidentate ligand through ON donor sites. ESR spectra show the simultaneous presence of a planar trans and a nearly planar cis isomers in the 1:2 ratio for all N,O complexes [Cu(Ln)2]Cl2峁2H2O. Schiff bases (Ln) were tested against bacterial species; namely two Gram positive bacteria (Staphylococcus aureus and Bacillus cereus) and two Gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) and fungal species (Aspergillus niger, Fusarium oxysporium, Penicillium italicum and Alternaria alternata). The tested compounds have antibacterial activity against S. aureus, B. cereus and K. pneumoniae.

  15. Multi-scale modelling of uranyl chloride solutions

    SciTech Connect

    Nguyen, Thanh-Nghi; Duvail, Magali Villard, Arnaud; Dufr锚che, Jean-Fran莽ois; Molina, John Jairo; Guilbaud, Philippe

    2015-01-14

    Classical molecular dynamics simulations with explicit polarization have been successfully used to determine the structural and thermodynamic properties of binary aqueous solutions of uranyl chloride (UO{sub 2}Cl{sub 2}). Concentrated aqueous solutions of uranyl chloride have been studied to determine the hydration properties and the ion-ion interactions. The bond distances and the coordination number of the hydrated uranyl are in good agreement with available experimental data. Two stable positions of chloride in the second hydration shell of uranyl have been identified. The UO{sub 2}{sup 2+}-Cl{sup 鈭拀 association constants have also been calculated using a multi-scale approach. First, the ion-ion potential averaged over the solvent configurations at infinite dilution (McMillan-Mayer potential) was calculated to establish the dissociation/association processes of UO{sub 2}{sup 2+}-Cl{sup 鈭拀 ion pairs in aqueous solution. Then, the association constant was calculated from this potential. The value we obtained for the association constant is in good agreement with the experimental result (K{sub UO{sub 2Cl{sup +}}} = 1.48 l mol{sup 鈭1}), but the resulting activity coefficient appears to be too low at molar concentration.

  16. Secondary coordination sphere effects in ruthenium(III) tetraammine complexes: role of the coordinated water molecule.

    PubMed

    Souza, Maykon L; Castellano, Eduardo E; Telser, Joshua; Franco, Douglas W

    2015-02-16

    The complexes trans-[Ru(III)(NH3)4(4-pic)(H2O)](CF3SO3)3 (1) and [Ru(III)(NH3)5(4-pic)](CF3SO3)3 (2) were isolated and studied experimentally by electron paramagnetic resonance (EPR) and UV-vis spectroscopies, cyclic voltammetry, and X-ray crystallography and theoretically by ligand-field theory (LFT) and density functional theory (DFT) calculations. Complex 1 is reported in two different crystal forms, 1a (100 K) and 1b (room temperature). EPR and UV-vis spectroscopies suggest that aqua ligand interaction in this low-spin ruthenium(III) complex changes as a function of hydrogen bonding with solvent molecules. This explicit water solvent effect was explained theoretically by DFT calculations, which demonstrated the effect of rotation of the aqua ligand about the Npic-Ru-Oaq axis. The UV-vis spectrum of 1 shows in an aqueous acid solution a broad- and low-intensity absorption band around 28,500 cm(-1) (蔚 鈮 500 M(-1) cm(-1)) that is assigned mainly to a charge-transfer (CT) transition from the equatorial ligands to the Ru 尾-4dxy orbital (尾-LUMO) using DFT calculations. The electronic reflectance spectrum of 1 shows a broad and intense absorption band around 25,500 cm(-1) that is assigned to a CT transition from 4-picoline to the Ru 尾-4dxz orbital (尾-LUMO) using DFT calculations. The t2g(5) set of orbitals had its energy splitting investigated by LFT. LFT analysis shows that a rhombic component arises from C2v symmetry by a simple 蟺-bonding ligand (H2O in our case) twisting about the trans (C2) axis. This twist was manifested in the EPR spectra, which were recorded for 1 as a function of the solvent in comparison with [Ru(NH3)5(4-pic)](3+) and [Ru(NH3)5(H2O)](3+). Only 1 shows an evident change in the g-tensor values, wherein an increased rhombic component is correlated with a higher nucleophilicity (donor) solvent feature, as parametrized by the Abraham system. PMID:25654246

  17. Synthesis and characterization of phosphorescent three-coordinate Cu(I)-NHC complexes.

    PubMed

    Krylova, Valentina A; Djurovich, Peter I; Whited, Matthew T; Thompson, Mark E

    2010-09-28

    Cationic and neutral monomeric three-coordinate phosphorescent Cu(I) complexes were synthesized and characterized by XRD analysis, electrochemistry and photophysical studies in different environments. DFT calculations have aided the assignment of the electronic structure and excited state behavior of these complexes. PMID:20714560

  18. Improving communication and coordination of complex perinatal patients.

    PubMed

    Gordon, Sara; Aydam, Joan; Hamm, Kenna; Rocha, Morgan; Northcut, Andrea; Roberson, Becky; Shook, Marilyn

    2015-01-01

    Pregnant women with complex medical problems require comprehensive communication among members of their healthcare team. Using the Magnet Hospital model, our Patient and Perinatal Interprofessional Team at Seton Medical Center Austin focused on improving communication and patient satisfaction by initiating Perinatal Patient Care Conferences. Pregnant women with medical or obstetric complications and their families became a part of care plan development prior to admission to promote consistent communication and excellent care. We report our 7-year history of proactive meetings with pregnant women and their families in a nonclinical environment to discuss diagnosis, treatment, and prognosis. A collaborative written plan of care is developed that accommodates the woman's needs and wishes and is then disseminated among the healthcare team. This process has decreased women's and caregivers' anxiety and supported a culture of safety across the continuum of care. PMID:25919209

  19. 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.

  20. Adsorption of uranyl species on hydroxylated titanium carbide nanosheet: A first-principles study.

    PubMed

    Zhang, Yu-Juan; Lan, Jian-Hui; Wang, Lin; Wu, Qun-Yan; Wang, Cong-Zhi; Bo, Tao; Chai, Zhi-Fang; Shi, Wei-Qun

    2016-05-01

    In this work, hydroxylated titanium carbide Ti3C2(OH)2, a representative of the two-dimensional transition metal carbides, has been predicted to be an effective adsorbent for uranyl ions in aqueous environments for the first time using density functional theory simulations. The calculations revealed that the uranyl ion can strongly bind with Ti3C2(OH)2 nanosheet in aqueous solution regardless of the presence of anionic ligands such as OH(-), Cl(-) and NO3(-). The bidentate coordination of uranyl to the surface is energetically more favorable than other adsorption configurations, and the uranyl ion prefers to bind with the deprotonated O adsorption site rather than the protonated one on the hydroxylated surface. During the adsorption process, the chemical adsorption as well as the formation of hydrogen bonds is the dominant factor. PMID:26859616

  1. Preorganized Peptide Scaffolds as Mimics of Phosphorylated Proteins Binding Sites with a High Affinity for Uranyl.

    PubMed

    Starck, Matthieu; Sisommay, Nathalie; Laporte, Fanny A; Oros, St閜hane; Lebrun, Colette; Delangle, Pascale

    2015-12-01

    Cyclic peptides with two phosphoserines and two glutamic acids were developed to mimic high-affinity binding sites for uranyl found in proteins such as osteopontin, which is believed to be a privileged target of this ion in vivo. These peptides adopt a ?-sheet structure that allows the coordination of the latter amino acid side chains in the equatorial plane of the dioxo uranyl cation. Complementary spectroscopic and analytical methods revealed that these cyclic peptides are efficient uranyl chelating peptides with a large contribution from the phosphorylated residues. The conditional affinity constants were measured by following fluorescence tryptophan quenching and are larger than 10(10) at physiological pH. These compounds are therefore promising models for understanding uranyl chelation by proteins, which is relevant to this actinide ion toxicity. PMID:26583259

  2. 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

  3. Spin-labelled cyclometallated palladium complexes. EPR study of dynamic processes in coordination sphere

    NASA Astrophysics Data System (ADS)

    Kozhanov, K. A.; Bubnov, M. P.; Abakumov, G. A.; Cherkasov, V. K.

    2012-12-01

    New four-, five- and six-coordinated cyclometallated o-semiquinonato palladium complexes were obtained and characterized in solution by EPR. Interaction of square-planar azaphenyl palladium semiquinonate with mono and bidentate phosphane donors leads to formation of five- and six-coordinated adducts. Typical values of HFC constants on apical and basal phosphorouses are observed for such compounds. In one case the reversible addition of tri-phenyl-phosphane was observed. The coordination mode of pincer ligand (bi- or tridentate) in o-semiquinonato pincer complexes depends on the nature of linker between coordinating group and pincer aryl ring. In the case of sbnd CH2sbnd linker five coordinated complexes are formed. The "swing" and "fan" oscillations are observed for these compounds. Complexes with sbnd Osbnd linker are the first examples of compounds with bidentate bonded phosphorous-based pincer ligand. Most of complexes are unstable and decompose during some hours. Only the application of o-semiquinones as spin labels and using the EPR technique made possible to observe and interpret their structure.

  4. 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.

  5. On, off and intermediate coordination of a bridgehead triarylamine donor in tripodal complexes: towards the tuning of coordinative bond distance.

    PubMed

    W鰎l, Stefan; Hellwinkel, Dieter; Pritzkow, Hans; Hofmann, Matthias; Kr鋗er, Roland

    2004-09-01

    A series of first row transition metal complexes of the tripodal ligand 2,2',2"-nitrilotribenzoic acid H3L has been prepared and characterised by X-ray crystallography: Mononuclear [M(L)]- species [Cu(H2O)4]3[Cu(L)(H2O)]6.25H2O (2), [Co(H2O)6][Co(L)(H2O)].8H2O (4), [Zn(H2O)6][Zn(L)(H2O)].8H2O (5) and a neutral [M(L)] complex [Fe(III)2(L)(H2O)3].5H2O (8) are formed as well as dimeric [M(L)]2 2- species (HNEt3)2[Cu(L)]2.2CH3CN (1), (HNEt3)3[Ni(L)]2(ClO4).H2O (3), (HNEt3)2[Fe(II)(L)]2.2CH3CN (6) and (HNEt3)2[Fe(III)2(L)2(mu-O)](7). The complexes display a unique variation in the M-N distance (2.09 A for Cu(II) to 3.29 A for Fe(III)) to the bridgehead triphenylamine donor and are classified into compounds with "On","Off" and "Intermediate" N-coordination. The trigonal-bipyramidal coordination polyhedron changes towards tetrahedral in the intermediate and octahedral in the Off-state. The M-N distance of individual complexes is reversibly tuned by external chemical input such as changes of metal ion oxidation state (Fe(II)/Fe(III)) or variation of the axial coligand as a consequence of solvent or pH variation. Possible reasons for the exceptional tolerance of the M-N bond to distance variations are discussed under consideration of gas phase DFT calculations of [Zn(L)]-. PMID:15514762

  6. ESEEM Analysis of Multi-Histidine Cu(II)-Coordination in Model Complexes, Peptides, and Amyloid-?

    PubMed Central

    2015-01-01

    We validate the use of ESEEM to predict the number of 14N nuclei coupled to a Cu(II) ion by the use of model complexes and two small peptides with well-known Cu(II) coordination. We apply this method to gain new insight into less explored aspects of Cu(II) coordination in amyloid-? (A?). A? has two coordination modes of Cu(II) at physiological pH. A controversy has existed regarding the number of histidine residues coordinated to the Cu(II) ion in component II, which is dominant at high pH (?8.7) values. Importantly, with an excess amount of Zn(II) ions, as is the case in brain tissues affected by Alzheimer抯 disease, component II becomes the dominant coordination mode, as Zn(II) selectively substitutes component I bound to Cu(II). We confirm that component II only contains single histidine coordination, using ESEEM and set of model complexes. The ESEEM experiments carried out on systematically 15N-labeled peptides reveal that, in component II, His 13 and His 14 are more favored as equatorial ligands compared to His 6. Revealing molecular level details of subcomponents in metal ion coordination is critical in understanding the role of metal ions in Alzheimer抯 disease etiology. PMID:25014537

  7. New water soluble heterometallic complex showing unpredicted coordination modes of EDTA

    NASA Astrophysics Data System (ADS)

    Mudsainiyan, R. K.; Jassal, A. K.; Chawla, S. K.

    2015-10-01

    A mesoporous 3D polymeric complex (I) having formula {[Zr(IV)O-?3-(EDTA)Fe(III)OH]稨2O}n has been crystallized and characterized by various techniques. Single-crystal X-ray diffraction analysis revealed that complex (I) crystallized in chiral monoclinic space group Cc (space group no. 9) with unexpected coordination modes of EDTA and mixture of two transition metal ions. In this complex, the coordination number of Zr(IV) ion is seven where four carboxylate oxygen atoms, two nitrogen atoms, one oxide atom are coordinating with Zr(IV). Fe(III) is four coordinated and its coordination environment is composed of three different carboxylic oxygen atoms from three different EDTA and one oxygen atom of -OH group. The structure consists of 4-c and 16-c (2-nodal) net with new topology and point symbol for net is (336454530)(36). TGA study and XRPD pattern showed that the coordination polymer is quite stable even after losing water molecule and -OH ion. Quenching behavior in fluorescence of ligand is observed by complexation with transition metal ions is due to n-?* transition. The SEM micrograph shows the morphology of complex (I) exhibits spherical shape with size ranging from 50 to 280 nm. The minimum N2 (SBET=8.7693 m2/g) and a maximum amount of H2 (high surface area=1044.86 m2/g (STP)) could be adsorbed at 77 K. From DLS study, zeta potential is calculated i.e. -7.94 shows the negative charges on the surface of complex. Hirshfeld surface analysis and fingerprint plots revealed influence of weak or non bonding interactions in crystal packing of complex.

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

    PubMed

    Arnold, Polly L; P閏harman, Anne-Fr閐閞ique; 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

  9. Coordination of the ankle joint complex during walking.

    PubMed

    Smith, R; Rattanaprasert, U; O'Dwyer, N

    2001-11-01

    A simple model of the joint between the leg and the rearfoot is that of two hinges each with one degree of freedom. The superior hinge at the talocrural joint caters for most of the sagittal plane motion due to its mediolateral orientation. Motion in the transverse and coronal planes is largely taken up by the subtalar joint which has an inclination of 42 degrees to the transverse plane and deviates 23 degrees to the medial side. It could be expected from the orientation of this joint that rearfoot motion in the coronal plane (inversion/eversion) would be tightly coupled to motion in the transverse plane (adduction/abduction). A simple, non-viscous mechanical hinge joint would produce an in-phase, fixed gain relationship between inversion/eversion and adduction/abduction. This relation could be adequately quantified by Pearson's product moment correlation (r(P)). In contrast, muscular control of the joint, which introduces visco-elastic elements and time-delayed control lines and feedback loops, could be characterised by more complex phase and gain relations among the frequency components of the signals. These relations can be characterised by a transfer function relation (gain and phase angle) computed using a dynamic analysis. In the present study, both Pearson's correlation and linear systems analysis were employed. For 43 normal adults, five trials of one walking stride (stance and swing phases) were videographed at 30 Hz with three markers placed on each of the leg and rearfoot. Using inversion/eversion as the input and adduction/abduction as the output, the proportion of the total variance accounted for by a dynamic relation was measured by the coherence square function, which is analogous to the correlation squared (r(P)(2)). The mean r(P)(2) was 0.26, whereas the mean overall coherence was 0.62, thus accounting for more than twice the variance. This result suggests that while there may be a degree of simple mechanical coupling between inversion/eversion and adduction/abduction during walking, the major control is via muscular and/or visco-elastic passive elements. PMID:11750672

  10. 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

  11. Synthesis, complexation, and coordination oligomerization of 1,8-pyrazine-capped 5,12-dioxocyclams.

    PubMed

    Hegedus, Louis S; Sundermann, Michael J; Dorhout, Peter K

    2003-07-14

    (Methyl)(methoxy)-5,12-dioxocyclam 1 was alkylated on the secondary amines (capped) with 2,6-bis(bromomethyl)pyrazine. The resulting macrocycle was complexed to copper(II) to produce a five-coordinate complex 5a which was fully characterized by a range of spectroscopic methods (IR, UV-vis, ESR) as well as by X-ray crystallography. The structure of this complex is similar to the previously reported pyridine complex, with the five-coordinate copper having distorted square pyramidal geometry and a Cu-Pz bond length of 2.125 A. Attempts to prepare this same complex under microwave irradiation instead produced a trinuclear complex 6a having an octahedral copper(II) center complexed to two pyrazine-cyclam copper units through the amide carbonyl oxygen and the methoxyl group oxygen of the cyclam unit. The X-ray crystal structure of the trinuclear complex showed extensive distortion in the cyclam rings. The remote nitrogen of pyrazine-cyclam complex 5a was capable of coordinating an additional metal. Treatment with RuCl(2)(DMSO)(4) or Rh(2)(OAc)(4), respectively, produced trimetallic Cu-Ru-Cu complex 7 or tetrametallic Cu-Rh-Rh-Cu complex 8. The latter was fully characterized, including an X-ray crystal structure, and had two pyrazine-cyclam complexes bridged by a Rh(2)(OAc)(4) unit through the remote pyrazine nitrogens. There was little distortion in the pyrazine-cyclam copper units as compared to complex 5a: the four metals were collinear, and the two cyclam units were eclipsed. All of the copper complexes were subjected to cyclic voltametry measurements, and no reversible redox changes were observed. Magnetic measurements of 6a and 8 showed the copper atoms to be weakly antiferromagnetically coupled. PMID:12844307

  12. Mechanics of metal-catecholate complexes: The roles of coordination state and metal types

    PubMed Central

    Xu, Zhiping

    2013-01-01

    There have been growing evidences for the critical roles of metal-coordination complexes in defining structural and mechanical properties of unmineralized biological materials, including hardness, toughness, and abrasion resistance. Their dynamic (e.g. pH-responsive, self-healable, reversible) properties inspire promising applications of synthetic materials following this concept. However, mechanics of these coordination crosslinks, which lays the ground for predictive and rational material design, has not yet been well addressed. Here we present a first-principles study of representative coordination complexes between metals and catechols. The results show that these crosslinks offer stiffness and strength near a covalent bond, which strongly depend on the coordination state and type of metals. This dependence is discussed by analyzing the nature of bonding between metals and catechols. The responsive mechanics of metal-coordination is further mapped from the single-molecule level to a networked material. The results presented here provide fundamental understanding and principles for material selection in metal-coordination-based applications. PMID:24107799

  13. Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

    PubMed

    Kim, Sang Bok; Pike, Robert D; Sweigart, Dwight A

    2013-11-19

    Quinonoid metal complexes have potential applications in surface chemistry, coordination polymers, and catalysts. Although quinonoid manganese tricarbonyl complexes have been used as secondary building units (SBUs) in the formation of novel metal-organometallic coordination networks and polymers, the potentially wider applications of these versatile linkers have not yet been recognized. In this Account, we focus on these diverse new applications of quinonoid metal complexes, and report on the variety of quinonoid metal complexes that we have synthesized. Through the use of [(?(6)-hydroquinone)Mn(CO)3](+), we are able to modify the surface of Fe3O4 and FePt nanoparticles (NPs). This process occurs either by the replacement of oleylamine with neutral [(?(5)-semiquinone)Mn(CO)3] at the NP surface, or by the binding of anionic [(?(4)-quinone)Mn(CO)3](-) upon further deprotonation of [(?(5)-semiquinone)Mn(CO)3] at the NP surface. We have demonstrated chemistry at the intersection of surface-modified NPs and coordination polymers through the growth of organometallic coordination polymers onto the surface modified Fe3O4 NPs. The resulting magnetic NP/organometallic coordination polymer hybrid material exhibited both the unique superparamagnetic behavior associated with Fe3O4 NPs and the paramagnetism attributable to the metal nodes, depending upon the magnetic range examined. By the use of functionalized [(?(5)-semiquinone)Mn(CO)3] complexes, we attained the formation of an organometallic monolayer on the surface of highly ordered pyrolitic graphite (HOPG). The resulting organometallic monolayer was not simply a random array of manganese atoms on the surface, but rather consisted of an alternating "up and down" spatial arrangement of Mn atoms extending from the HOPG surface due to hydrogen bonding of the quinonoid complexes. We also showed that the topology of metal atoms on the surface could be controlled through the use of quinonoid metal complexes. A quinonoid rhodium complex showed catalytic activity in Suzuki-Miyaura type reaction. As a result of the excellent stability of the homogeneous catalyst [(quinone)Rh(COD)](-) in water, we also successfully demonstrated catalyst recycling in 1,2- and 1,4-addition reactions. The compound [(quinone)Ir(COD)](-) showed significantly poorer catalytic activity in 1,4-addition reactions. Following upon the excellent coordination ability of the quinonoid rhodium complexes to metal centers, we synthesized organometallic coordination polymer nanocatalysts and silica gel-supported quinonoid rhodium catalysts, the latter using a surface sol-gel technique. The resulting heterogeneous catalysts showed activity in the stereospecific polymerization of phenylacetylene. PMID:23745596

  14. Coordination of Care for Complex Pediatric Patients: Perspectives from Providers and Parents

    PubMed Central

    Horsky, Jan; Morgan, Stephen J.; Ramelson, Harley Z.

    2014-01-01

    Coordinators help patients requiring complex chronic care manage frequent ambulatory visits and services received at home or from community-based agencies. EHRs directly support only a few of the required tasks as they do not allow access to all parties involved in care. Our goal was to examine how technology was used to coordinate efforts and to describe common barriers and facilitators. Insights may inform the design of tools that would effectively support identified goals. We conducted five hours of interviews with sixteen parents and six clinicians and characterized emergent themes from transcripts. Situational awareness, care and visit planning, document aggregation, abstraction and interpretation were tasks essential to coordination yet generally poorly supported by EHRs. Providers communicated primarily by email, telephone and by exchanging paper and scanned documents. A preliminary model of coordination that could be used in the planning and testing stages of a User Centered Design process is described. PMID:25954374

  15. Electrochemically fabricated polypyrrole-cobalt-oxygen coordination complex as high-performance lithium-storage materials.

    PubMed

    Guo, Bingkun; Kong, Qingyu; Zhu, Ying; Mao, Ya; Wang, Zhaoxiang; Wan, Meixiang; Chen, Liquan

    2011-12-23

    Current lithium-ion battery (LIB) technologies are all based on inorganic electrode materials, though organic materials have been used as electrodes for years. Disadvantages such as limited thermal stability and low specific capacity hinder their applications. On the other hand, the transition metal oxides that provide high lithium-storage capacity by way of electrochemical conversion reaction suffer from poor cycling stability. Here we report a novel high-performance, organic, lithium-storage material, a polypyrrole-cobalt-oxygen (PPy-Co-O) coordination complex, with high lithium-storage capacity and excellent cycling stability. Extended X-ray absorption fine structure and Raman spectroscopy and other physical and electrochemical characterizations demonstrate that this coordination complex can be electrochemically fabricated by cycling PPy-coated Co(3)O(4) between 0.0 V and 3.0 V versus Li(+)/Li. Density functional theory (DFT) calculations indicate that each cobalt atom coordinates with two nitrogen atoms within the PPy-Co coordination layer and the layers are connected with oxygen atoms between them. Coordination weakens the C-H bonds on PPy and makes the complex a novel lithium-storage material with high capacity and high cycling stability. PMID:22127820

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

    PubMed

    Huynh, Thi-Ngoc Suong; Bourgeois, Damien; Basset, Christian; Vidaud, Claude; Hag鑗e, Agn鑣

    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

  17. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

    NASA Astrophysics Data System (ADS)

    Prado, Yoann; Daff, Ni閘i; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Gren鑓he, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-Dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, J閞鬽e

    2015-12-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest--and more attractive--systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm ?-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination--without nanoparticle aggregation and without complex dissociation--of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 1.71-1.80 B.M. corresponding to one unpaired electron respectively. The formation constants and free energies were measured spectrophotometrically, at constant ionic strength 0.1 M (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.

  19. Coordination and Organometallic Complexes as Second-Order Nonlinear Optical Molecular Materials

    NASA Astrophysics Data System (ADS)

    di Bella, Santo; Dragonetti, Claudia; Pizzotti, Maddalena; Roberto, Dominique; Tessore, Francesca; Ugo, Renato

    Coordination and organometallic complexes with second-order nonlinear optical (NLO) properties have attracted increasing attention as potential molecular building block materials for optical communications, optical data processing and storage, or electrooptical devices. In particular, they can offer additional flexibility, when compared to organic chromophores, due to the presence of metal-ligand charge-transfer transitions, usually at relatively low-energy and of high intensity, tunable by virtue of the nature, oxidation state, and coordination sphere of the metal center. This chapter presents an overview of the main classes of second-order NLO coordination and organometallic complexes with various ligands such as substituted amines, pyridines, stilbazoles, chelating ligands (bipyridines, phenanthrolines, terpyridines, Schiff bases), alkynyl, vinylidene, and cyclometallated ligands, macrocyclic ligands (porphyrins and phthalocyanines), metallocene derivatives, and chromophores with two metal centers. The coverage, mainly from 2000 up to now, is focused on NLO properties measured at molecular level from solution studies, as well as on NLO properties of bulk materials.

  20. 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.

  1. Pyridinediimine Iron Complexes with Pendant Redox-Inactive Metals Located in the Secondary Coordination Sphere.

    PubMed

    Delgado, Mayra; Ziegler, Joshua M; Seda, Takele; Zakharov, Lev N; Gilbertson, John D

    2016-01-19

    A series of pyridinediimine (PDI) iron complexes that contain a pendant 15-crown-5 located in the secondary coordination sphere were synthesized and characterized. The complex Fe((15c5)PDI)(CO)2 (2) was shown in both the solid state and solution to encapsulate redox-inactive metal ions. Modest shifts in the reduction potential of the metal-ligand scaffold were observed upon encapsulation of either Na(+) or Li(+). PMID:26692111

  2. Synthesis and Base Hydrolysis of a Cobalt(III) Complex Coordinated by a Thioether Ligand

    ERIC Educational Resources Information Center

    Roecker, Lee

    2008-01-01

    A two-week laboratory experiment for students in advanced inorganic chemistry is described. Students prepare and characterize a cobalt(III) complex coordinated by a thioether ligand during the first week of the experiment and then study the kinetics of Co-S bond cleavage in basic solution during the second week. The synthetic portion of the

  3. Synthesis and Base Hydrolysis of a Cobalt(III) Complex Coordinated by a Thioether Ligand

    ERIC Educational Resources Information Center

    Roecker, Lee

    2008-01-01

    A two-week laboratory experiment for students in advanced inorganic chemistry is described. Students prepare and characterize a cobalt(III) complex coordinated by a thioether ligand during the first week of the experiment and then study the kinetics of Co-S bond cleavage in basic solution during the second week. The synthetic portion of the鈥

  4. Synthesis and Crystal Structures of Benzohydroxamate-Coordinated Vanadium(V) Oxo Complexes with Aroylhydrazone Ligands.

    PubMed

    Qian, Shao-Song; Zhao, Xinlu; Wang, Jia; You, Zhonglu

    2015-01-01

    Reaction of [VO(acac)2] (where acac = acetylacetonate), benzohydroxamic acid (Hbha), and two similar aroylhydrazone ligands in methanol produced two benzohydroxamate-coordinated mononuclear vanadium(V) oxo complexes with general formula [VOL(bha)], where L = L1 = N'-(5-bromo-2-hydroxybenzylidene)-2-fluorobenzohydrazide (H2L1), and L = L2 = N'-(3-bromo-2-hydroxybenzylidene)-2-fluorobenzohydrazide (H2L2). Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction method. All of the investigated compounds were further characterized by elemental analysis, and FT-IR and UV-Vis spectra. Single crystal X-ray structural studies indicate that the benzohydrazone ligands coordinate to the VOcores through phenolate O, imino N, and enolate O atoms, and the benzohydroxamate ligands coordinate to the VO cores through deprotonated hydroxyl O and carbonyl O atoms. The V atoms in both complexes are in octahedral coordination. Thermal stability of the complexes was studied. PMID:26680710

  5. Slow magnetic relaxation in a mononuclear eight-coordinate cobalt(II) complex.

    PubMed

    Chen, Lei; Wang, Jing; Wei, Jin-Mei; Wernsdorfer, Wolfgang; Chen, Xue-Tai; Zhang, Yi-Quan; Song, You; Xue, Zi-Ling

    2014-09-01

    The quest for the single-molecular magnets (SMMs) based on mononuclear transition-metal complexes is focused on the low-coordinate species. No transition-metal complex with a coordination number of eight has been shown to exhibit SMM properties. Here the magnetic studies have been carried out for a mononuclear, eight-coordinate cobalt(II)-12-crown-4 (12C4) complex [Co(II)(12C4)2](I3)2(12C4) (1) with a large axial zero-field splitting. Magnetic measurements show field-induced, slow magnetic relaxation under an applied field of 500 Oe at low temperature. The magnetic relaxation time ? was fitted by the Arrhenius model to afford an energy barrier of Ueff = 17.0 cm(-1) and a preexponential factor of ?0 = 1.5 10(-6) s. The work here presents the first example of the eight-coordinate, mononuclear, 3d metal complex exhibiting the slow magnetic relaxation. PMID:25119268

  6. Controlled Flexible Coordination in Tripodal Iron(II) Phosphane Complexes: Effects on Reactivity.

    PubMed

    Petuker, Anette; Merz, Klaus; Merten, Christian; Apfel, Ulf-Peter

    2016-02-01

    The possibility to alter properties of metal complexes without significant steric changes is a useful tool to tailor the reactivity of the complexes. Herein we present the synthesis of iron complexes with the tripodal phosphane ligands Triphos and Triphos(Si) and report on their different coordination properties. Whereas reaction of Triphos(Si) and FeX2 (X = Cl, Br) exclusively afforded (Triphos(Si))FeX2 with a ?(2)-coordinated ligand, the homologous C-derived Fe complexes show rapid conversion in solution to afford [(Triphos)Fe(CH3CN)3][Fe2Cl6] or [(Triphos)Fe(CH3CN)3][FeBr4], respectively. The structural conversion was found to be temperature- and solvent-dependent and was accompanied by a linear change of the overall magnetization. The different ligand influence was shown to have a significant effect on the ability of (Triphos(Si))FeCl2 and (Triphos)FeCl2 to perform the Sonogashira cross-coupling reaction of 4-iodotoluene and phenyl acetylene as well as the hydrosilylation of acetophenone. The results presented herein show the different coordination properties of two structurally homologous tripodal ligands and demonstrate the importance of geometrically controlled ligand field splitting on the stability and reactivity of metal complexes. The C/Si exchange therefore provides a simple and straightforward tool to manipulate properties and reactivity of metal complexes. PMID:26751622

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

    PubMed

    Rodr韌uez-Jeangros, Nicol醩; 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

  8. Flaviviral Replication Complex: Coordination between RNA Synthesis and 51-RNA Capping.

    PubMed

    Klema, Valerie J; Padmanabhan, Radhakrishnan; Choi, Kyung H

    2015-08-01

    Genome replication in flavivirus requires (-) strand RNA synthesis, (+) strand RNA synthesis, and 51-RNA capping and methylation. To carry out viral genome replication, flavivirus assembles a replication complex, consisting of both viral and host proteins, on the cytoplasmic side of the endoplasmic reticulum (ER) membrane. Two major components of the replication complex are the viral non-structural (NS) proteins NS3 and NS5. Together they possess all the enzymatic activities required for genome replication, yet how these activities are coordinated during genome replication is not clear. We provide an overview of the flaviviral genome replication process, the membrane-bound replication complex, and recent crystal structures of full-length NS5. We propose a model of how NS3 and NS5 coordinate their activities in the individual steps of (-) RNA synthesis, (+) RNA synthesis, and 51-RNA capping and methylation. PMID:26287232

  9. Flaviviral Replication Complex: Coordination between RNA Synthesis and 5鈥-RNA Capping

    PubMed Central

    Klema, Valerie J.; Padmanabhan, Radhakrishnan; Choi, Kyung H.

    2015-01-01

    Genome replication in flavivirus requires (鈭) strand RNA synthesis, (+) strand RNA synthesis, and 5鈥-RNA capping and methylation. To carry out viral genome replication, flavivirus assembles a replication complex, consisting of both viral and host proteins, on the cytoplasmic side of the endoplasmic reticulum (ER) membrane. Two major components of the replication complex are the viral non-structural (NS) proteins NS3 and NS5. Together they possess all the enzymatic activities required for genome replication, yet how these activities are coordinated during genome replication is not clear. We provide an overview of the flaviviral genome replication process, the membrane-bound replication complex, and recent crystal structures of full-length NS5. We propose a model of how NS3 and NS5 coordinate their activities in the individual steps of (鈭) RNA synthesis, (+) RNA synthesis, and 5鈥-RNA capping and methylation. PMID:26287232

  10. Spectroscopic and theoretical studies on axial coordination of bis(pyrrol-2-ylmethyleneamine)phenyl complexes

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Mei; Ruan, Wen-Juan; Meng, Liang; Gao, Feng; Zhu, Zhi-Ang

    2008-11-01

    Metal (M = Zn(II), Ni(II), Cu(II)) complexes with tetradentate Schiff base ligand, bis(pyrrol-2-ylmethyleneamine)phenyl, has been synthesized and characterized by elemental analyses, 1H NMR, mass spectra and UV-vis spectra. The standard association constants ( K?) and the thermodynamic parameters (?Hm?, ?Sm?, ?Gm?) for axial coordination of imidazole derivatives with these Shiff base complexes were measured with UV-vis spectrophotometric titration. The decrease of enthalpy is found to be the drive of the axial coordination. Our Schiff base complexes can incorporate two axial ligands, except 2-Et-4-MeIm with two big substituents of great steric bulk according to stoichiometry of 1:1. ZnL displays high selectively binding to imidazole due to the steric bulk effect. Supporting density functional theory (DFT) calculations have been undertaken on B3LYP/6-31G(d) level.

  11. Evolutionary dynamics of the traveler's dilemma and minimum-effort coordination games on complex networks

    NASA Astrophysics Data System (ADS)

    Iyer, Swami; Killingback, Timothy

    2014-10-01

    The traveler's dilemma game and the minimum-effort coordination game are social dilemmas that have received significant attention resulting from the fact that the predictions of classical game theory are inconsistent with the results found when the games are studied experimentally. Moreover, both the traveler's dilemma and the minimum-effort coordination games have potentially important applications in evolutionary biology. Interestingly, standard deterministic evolutionary game theory, as represented by the replicator dynamics in a well-mixed population, is also inadequate to account for the behavior observed in these games. Here we study the evolutionary dynamics of both these games in populations with interaction patterns described by a variety of complex network topologies. We investigate the evolutionary dynamics of these games through agent-based simulations on both model and empirical networks. In particular, we study the effects of network clustering and assortativity on the evolutionary dynamics of both games. In general, we show that the evolutionary behavior of the traveler's dilemma and minimum-effort coordination games on complex networks is in good agreement with that observed experimentally. Thus, formulating the traveler's dilemma and the minimum-effort coordination games on complex networks neatly resolves the paradoxical aspects of these games.

  12. Catalytic Transformation of Aldehydes with Nickel Complexes through ?(2) Coordination and Oxidative Cyclization.

    PubMed

    Hoshimoto, Yoichi; Ohashi, Masato; Ogoshi, Sensuke

    2015-06-16

    Chemists no longer doubt the importance of a methodology that could activate and utilize aldehydes in organic syntheses since many products prepared from them support our daily life. Tremendous effort has been devoted to the development of these methods using main-group elements and transition metals. Thus, many organic chemists have used an activator-(aldehyde oxygen) interaction, namely, ?(1) coordination, whereby a Lewis or Br鴑sted acid activates an aldehyde. In the field of coordination chemistry, ?(2) coordination of aldehydes to transition metals by coordination of a carbon-oxygen double bond has been well-studied; this activation mode, however, is rarely found in transition-metal catalysis. In view of the distinctive reactivity of an ?(2)-aldehyde complex, unprecedented reactions via this intermediate are a distinct possibility. In this Account, we summarize our recent results dealing with nickel(0)-catalyzed transformations of aldehydes via ?(2)-aldehyde nickel and oxanickelacycle intermediates. The combination of electron-rich nickel(0) and strong electron-donating N-heterocyclic carbene (NHC) ligands adequately form ?(2)-aldehyde complexes in which the aldehyde is highly activated by back-bonding. With Ni(0)/NHC catalysts, processes involving intramolecular hydroacylation of alkenes and homo/cross-dimerization of aldehydes (the Tishchenko reaction) have been developed, and both proceed via the simultaneous ?(2) coordination of aldehydes and other ? components (alkenes or aldehydes). The results of the mechanistic studies are consistent with a reaction pathway that proceeds via an oxanickelacycle intermediate generated by the oxidative cyclization with a nickel(0) complex. In addition, we have used the ?(2)-aldehyde nickel complex as an effective activator for an organosilane in order to generate a silicate reactant. These reactions show 100% atom efficiency, generate no wastes, and are conducted under mild conditions. PMID:25955708

  13. Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring 魏1-N1 Coordination

    PubMed Central

    Fillman, Kathlyn L.; Arman, Hadi D.; Tonzetich, Zachary J.

    2015-01-01

    Homoleptic complexes of the anion of 7-azaindole (AzaIn) have been synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]路2L (L = THF, 2-MeTHF, toluene, or benzene) have been isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated to the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]路2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. DFT calculations have been performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-魏1-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions. PMID:26378471

  14. Homoleptic transition metal complexes of the 7-azaindolide ligand featuring ?(1)-N1 coordination.

    PubMed

    Przyojski, Jacob A; Kiewit, Monica L; Fillman, Kathlyn L; Arman, Hadi D; Tonzetich, Zachary J

    2015-10-01

    Homoleptic complexes of the anion of 7-azaindole (AzaIn) were synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]2L (L = tetrahydrofuran (THF), 2-MeTHF, toluene, or benzene) were isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated with the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. Density functional theory calculations were performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-?(1)-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions. PMID:26378471

  15. Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with Diethylenetriaminepentaacetic acide: temperature effect and coordination modes

    SciTech Connect

    Guoxin Tian; Leigh R. Martin; Zhiyong Zhang; Linfeng Rao

    2011-04-01

    Stability constants of two DTPA (diethylenetriaminepentaacetic acid) complexes with lanthanides (ML2- and MHL-, where M stands for Nd and Eu and L stands for diethylenetriaminepentaacetate) at 10, 25, 40, 55, and 70 degrees C were determined by potentiometry, absorption spectrophotometry, and luminescence spectroscopy. The enthalpies of complexation at 25 degrees C were determined by microcalorimetry. Thermodynamic data show that the complexation of Nd3镁 and Eu3镁 with DTPA is weakened at higher temperatures, a 10-fold decrease in the stability constants of ML2- and MHL- as the temperature is increased from 10 to 70 degrees C. The effect of temperature is consistent with the exothermic enthalpy of complexation directly measured by microcalorimetry. Results by luminescence spectroscopy and density functional theory (DFT) calculations suggest that DTPA is octa-dentate in both the EuL2- and EuHL- complexes and, for the first time, the coordination mode in the EuHL- complex was clarified by integration of the experimental data and DFT calculations. In the EuHL- complex, the Eu is coordinated by an octa-dentate H(DTPA) ligand and a water molecule, and the protonation occurs on the oxygen of a carboxylate group.

  16. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates.

    PubMed

    Miskowiec, Andrew; Kirkegaard, Marie C; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W; Trowbridge, Lee; Rondinone, Adam; Anderson, Brian

    2015-12-10

    We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielastic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform restricted motion on a length scale commensurate with the O-H bond (r = 0.92 ). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps(-1)) than their hydrogen-bonded partners (Dr = 28.7 ps(-1)). PMID:26575434

  17. Uranyl adsorption onto hydrous ferric oxide-A re-evaluation for the diffuse layer model database.

    PubMed

    Mahoney, John J; Cadle, Sonya A; Jakubowski, Ryan T

    2009-12-15

    The diffuse layer model (DLM) database of Dzombak and Morel was developed to quantify the adsorption of dissolved species onto the hydrous ferric oxide (HFO) surface, and contained numerous surface complexation reactions, including surface complexation reactions for uranyl (UO(2)(+2)) consisting of Hfo_sOUO(2)(+) and Hfo_wOUO(2)(+). However, these constants were not based upon experimentally obtained data, but rather were derived from linear free energy relationships (LFER) using log K(MOH) values. When compared to experimental data, the LFER-derived constants for uranyl were shown to overestimate adsorption by a factor of 10 in some cases. At least 14 uranyl HFO data sets have been previously published and were used to re-estimate constants by coupling the geochemical computer code PHREEQC with UCODE_2005, an automated parameter optimization program. Five uranyl-bearing surface complexation reactions were initially evaluated; the constants were optimized by allowing UCODE to incrementally vary selected log K(x)(int) values until the best fit to the experimental data was obtained. Assumptions consistent with the original DLM were retained. Changes to the K(1)(int) and K(2)(int) constants, and addition of uranyl monocarbonate and uranyl dicarbonate surface complexes, will update and correct the uranyl sorption reactions in this widely used database. PMID:20000518

  18. 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.

  19. 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.

  20. Seven-coordination versus six-coordination in divalent first-row transition-metal complexes derived from 1,10-diaza-15-crown-5.

    PubMed

    Vaiana, Lea; Regueiro-Figueroa, Mart韓; Mato-Iglesias, Marta; Platas-Iglesias, Carlos; Esteban-G髆ez, David; de Blas, Andr閟; Rodr韌uez-Blas, Teresa

    2007-10-01

    The complexes of the heptadentate receptor N,N'-bis(benzimidazol-2-ylmethyl)-1,10-diaza-15-crown-5 (L2) with MnII, CoII, NiII, CuII, and ZnII are reported. The X-ray crystal structures of the ZnII and NiII complexes show that whereas the ZnII ion is seven-coordinated in a (distorted) pentagonal-bipyramidal coordination environment, the NiII ion is only six-coordinated in a distorted octahedral coordination environment. Theoretical calculations on the [M(L2)]2+ systems (M = Mn, Co, Ni, Cu, or Zn) performed at the density functional theory (DFT; B3LYP) level have been used to obtain information about the structure and electronic properties of these complexes, as well as to rationalize their preferences for a pentagonal-bipyramidal or an octahedral coordination. We have found that for the MnII, CoII, CuII, and ZnII complexes, geometry optimizations lead systematically to pentagonal-bipyramidal coordination environments around the metal ions. However, for the NiII complex, two minimum-energy conformations were obtained, with the metal ion being in octahedral (o-[Ni(L2)]2+) or pentagonal-bipyramidal (pb-[Ni(L2)]2+) coordination. The stabilization of the octahedral geometry in the NiII complex can be considered as the result of the Jahn-Teller effect operating in pentagonal-bipyramidal geometry, which in an extreme case leads to an octahedral coordination. Spectrophotometric titrations carried out in dimethyl sulfoxide (DMSO) and CH3CN/DMSO (9:1) solutions indicate the following stability sequence for the complexes of L2: CoII approximately NiII > ZnII > MnII. The variations in the geometry and stability of the complexes may be rationalized in terms of the different occupations of the frontier molecular orbitals along the first-row transition-metal series. Finally, a time-dependent DFT approach was used to investigate the absorption spectrum of the [Cu(L2)]2+ complex based on the optimized geometries at the B3LYP level, also confirming a pentagonal-bipyramidal coordination in solution for this compound. PMID:17764174

  1. Metal-organic frameworks based on uranyl and phosphonate ligands.

    PubMed

    Monteiro, Bernardo; Fernandes, Jos A; Pereira, Cl醬dia C L; Vilela, S閞gio M F; Tom, Jo鉶 P C; Mar鏰lo, Joaquim; Almeida Paz, Filipe A

    2014-02-01

    Three new crystalline metal-organic frameworks have been prepared from the reaction of uranyl nitrate with nitrilotris(methylphosphonic acid) [H6nmp, N(CH2PO3H2)3], 1,4-phenylenebis(methylene)diphosphonic acid [H4pmd, C6H4(PO3H2)2], and (benzene-1,3,5-triyltris(methylene))triphosphonic acid [H6bmt, C6H3(PO3H2)3]. Compound [(UO2)2F(H3nmp)(H2O)]4H2O (I) crystallizes in space group C2/c, showing two crystallographically independent uranyl centres with pentagonal bipyramidal coordination geometries. While one metal centre is composed of a {(UO2)O3(?-F)}2 dimer, the other comprises an isolated {(UO2)O5} polyhedron. Compound [(UO2)(H2pmd)] (II) crystallizes in space group P21/c, showing a centrosymmetric uranyl centre with an octahedral {(UO2)O4} coordination geometry. Compound [(UO2)3(H3bmt)2(H2O)2]14H2O (III) crystallizes in space group P\\bar 1, showing two crystallographically independent uranyl centres. One uranyl centre is a {(UO2)O5} pentagonal bipyramid similar to that in (I), while the other is a {(UO2)O4} centrosymmetric octahedron similar to that in (II). Compounds (I) and (III) contain solvent-accessible volumes accounting for ca 23.6 and 26.9% of their unit-cell volume, respectively. In (I) the cavity has a columnar shape and is occupied by disordered water molecules, while in (III) the cavity is a two-dimensional layer with more ordered water molecules. All compounds have been studied in the solid state using FT-IR spectroscopy. Topological studies show that compounds (I) and (III) are trinodal, with 3,6,6- and 4,4,6-connected networks, respectively. Compound (II) is instead a 4-connected uninodal network of the type cds. PMID:24441125

  2. 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.

  3. Anion-regulated assemblies of diverse CuII coordination complexes with a versatile tripyridyltriazole ligand

    NASA Astrophysics Data System (ADS)

    Wang, Fei-Fei; Guo, Wei; Jiang, Cheng-Hui; Guo, Ya-Mei

    2013-08-01

    In this work, a series of five CuII coordination complexes, {[Cu(L)(dca)(OAc)]?1.5H2O}n (1), [Cu(L)(dca)Br]2 (2), [Cu(L)(OAc)2]2 (3), [Cu(L)Cl2]2 (4), and [Cu(L)2(ClO4)2] (5), have been prepared with a novel tripyridyltriazole ligand 3,4-bis(2-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (L) and different CuII sources. Single-crystal X-ray diffraction analysis reveals that these complexes show diverse 1-D (for 1), dimeric (for 2-4) and monomeric (for 5) coordination motifs, in which the L ligands exhibit different coordination fashions. These results obviously demonstrate that the structural assembly of complexes 1-5 can be exclusively dominated by the counter anions of metal salts and the auxiliary dicyanamide (dca) anion. Their thermal stabilities have also been investigated and discussed.

  4. Synthesis, crystal structure, photoluminescence property and photoelectronic behavior of two uranyl-organic frameworks constructed from 1, 2, 4, 5-benzenetetracarboxylic acid as ligand.

    PubMed

    Hou, Ya-Nan; Xing, Yong-Heng; Bai, Feng-Ying; Guan, Qing-Lin; Wang, Xuan; Zhang, Rui; Shi, Zhan

    2014-04-01

    By using 1, 2, 4, 5-benzenetetracarboxylic acid as organic ligands, two uranyl coordination complexes, (UO2)2(bta)(DMA)2 (1) and [(UO2)2(bta)(?3-OH2)]2[HN(CH3)2]稨2O (2) (H4bta=1, 2, 4, 5-benzenetetracarboxylic acid, DMA=N,N-Dimethylacetamide) were synthesized. The X-ray single crystal analysis revealed that complex 1 exhibits a 3-demensional framework, while complex 2 exhibits a 2-demensional framework. In order to furthermore characterize the two complexes and extend their functional properties, spectroscopies of IR, UV-vis, photoluminescence and surface photovoltage were also studied primarily. In addition, thermogravimetric analyses and photocatalytic studies for complexes 1 and 2 were discussed in detail. PMID:24398470

  5. SIDEROPHILIN METAL COORDINATION. 1. COMPLEXATION OF THORIUM BY TRANSFERRIN: STRUCTURE-FUNCTION IMPLICATIONS

    SciTech Connect

    Harris, Wesley R.; Carrano, Carl J.; Pecoraro, Vincent L.; Raymond, Kenneth N.

    1980-08-01

    As part of a program to develop actinide-specific sequestering agents, the coordination of actinide ions by human transferrin is being investigated. Therapeutically useful synthetic ligands must be able to compete with this iron-transport protein for the bound actinide ion. As in the Fe(III) complex of the native protein, two Th(IV) ions bind at pH 7. This coordination has been monitored at several pH values by using difference ultraviolet spectroscopy. The corresponding coordination of a phenolic ligand, ethylene-bis-(o-hydroxyphenylglycine) [EHPG], has been used to determine {Delta}{epsilon} for a tyrosyl group coordinated to Th(IV), in contrast to the common practice of assuming the {Delta}{epsilon} for protons and all metal ions is the same. This in turn is used to determine, from the observed {Delta}{epsilon} upon protein coordination, the number of transferrin tyrosine residues that coordinate. Maxima in the Th(IV) + EHPG difference UV spectra occur at 292 and 238 nm, with corresponding {Delta}{epsilon} values per phenolic group of 2330 and 8680 cm{sup -1} M{sup -1}, respectively. At pH 7.2, the Th(IV) transferrin spectrum is closely similar to the TH(IV) EHPG spectrum, with maxima at 292 and 240 nm. The {Delta}{epsilon} at 240 nm reaches a maximum of 24700 cm{sup -1} M{sup -1}, which corresponds to coordination of three tyrosine residues in the dithorium-transferrin complex; the stronger binding site (揂 or C-terminal) coordinates via two tyrosines and the weaker (揃 or N-terminal) via one. There is evidence suggesting that the N-terminal site is slightly smaller than the C-terminal site; while Th(IV) easily fits into the C-terminal site, the large ionic radius of Th(IV) makes this ion of borderline size to fit into the N-terminal site. This may be an important biological difference between Th(IV) and the slightly smaller Pu(IV), which should easily fit into both sites. At pH values below 7, the complexation of Th(IV) by transferrin decreases rapidly. At pH 6 and a Th(IV)/transferrin ratio of 2, only ~0.3 Th(IV) are bound per protein ([Th] = 10{sup -5}M). The N-terminal site is more rapidly affected by lowering the pH, so that coordination is entirely at the C-terminal site at low pH. Above pH 9, the conformation at the C-terminal site (two tyrosines) changes such that only one tyrosine is bound, the same that pertains at the N-terminal site at neutral pH. In addition to the three protons released by the coordinating tyrosine residues, the complexation of two Th(IV) ions releases two more protons at pH 8.6, which are ascribed to hydrolysis, so that the metal is bound as a monohydroxo species. It is suggested that diferric transferrin undergoes a similar reaction, and the other implications of these results for the structure and function of the native ferric transferrin are discussed.

  6. Coordination Structure Conversion of Hydrazone-Palladium(II) Complexes in the Solid State and in Solution.

    PubMed

    Kitamura, Fumi; Sawaguchi, Kana; Mori, Asami; Takagi, Shoji; Suzuki, Takayoshi; Kobayashi, Atsushi; Kato, Masako; Nakajima, Kiyohiko

    2015-09-01

    We prepared hydrazone-palladium(II) complexes of [PdCl2(HL(n))] and [PdCl(L(n))] (n = 1-3) by the reaction of [PdCl2(cod)] or [PdCl2(PhCN)2] and the hydrazone ligands of HL(n) {N'-(pyridin-2-ylmethylene)picolinohydrazide (HL(1)), N'-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (HL(2)), and N'-[(6-methylpyridin-2-yl)methylene]picolinohydrazide (HL(3))}. The structures of the complexes were determined by X-ray analysis. The hydrazone ligands had 魏N(py1),魏N(imine) and 魏N(amidate),魏N(py2) bidentate coordination modes in [PdCl2(HL(n))] (1, n = 1; 2, n = 2) and in [PdCl2(HL(3))] (3), respectively. In contrast, tridentate coordination modes of 魏N(py1),魏N(imine),魏N(py2) and 魏N(py1),魏N(amidate),魏N(py2) were observed in [PdCl(L(n))] (4, n = 1; 5, n = 2) and in [PdCl(L(n))] (6, n = 1; 7, n = 2; 8, n = 3). Thermal conversion of complexes 1-3 to complexes 6-8 proceeded in acetonitrile. Complexes 4 and 5 were obtained from complexes 1 and 2, respectively, in a basic acetonitrile solution under dark conditions. Complex 4 reverted immediately to complex 1 in an acidic acetonitrile solution that included hydrochloric acid. However, under room light, in the basic acetonitrile solution that included trimethylamine, complex 4 converted photochemically to complex 6. The thermochromic or vapochromic structure conversion of these complexes also occurred in the solid state. On heating at 180 掳C, the color of the crystals of complexes 1, 2, and 3 changed from yellow to orange in the solid state. (1)H NMR and/or UV-vis absorption spectroscopy confirmed that the orange complexes 6-8 were produced. The reddish-orange crystals of complexes 4 and 5 were exposed to hydrogen chloride vapor to yield the yellow products of complexes 1 and 2, respectively. PMID:26305775

  7. Computational Study of Coordinated Ni(II) Complex with High Nitrogen Content Ligands

    PubMed Central

    Tang, Bo; Ye, Jia-Hai; Ju, Xue-Hai

    2011-01-01

    Density functional computations were performed on two tetracoordinated Ni(II) complexes as high nitrogen content energetic materials (1: dinickel bishydrazine ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazole and 2: dinickel tetraazide ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazolate). The geometrical structures, relative stabilities and sensitivities, and thermodynamic properties of the complexes were investigated. The energy gaps of frontier molecular orbital (HOMO and LUMO) and vibrational spectroscopies were also examined. There are minor Jahn-Teller distortions in both complexes 1 and 2, with two long Ni朜 bond lengths and two short ones. The enthalpies of combustion for both complexes are over 3600?kJ/mol. The N朜 bond lengths in the moieties of hydrazine and azide ligands increase in the coordination process compared to those of the isolated molecules. PMID:24052834

  8. Computational Study of Coordinated Ni(II) Complex with High Nitrogen Content Ligands.

    PubMed

    Tang, Bo; Ye, Jia-Hai; Ju, Xue-Hai

    2011-01-01

    Density functional computations were performed on two tetracoordinated Ni(II) complexes as high nitrogen content energetic materials (1: dinickel bishydrazine ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazole and 2: dinickel tetraazide ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazolate). The geometrical structures, relative stabilities and sensitivities, and thermodynamic properties of the complexes were investigated. The energy gaps of frontier molecular orbital (HOMO and LUMO) and vibrational spectroscopies were also examined. There are minor Jahn-Teller distortions in both complexes 1 and 2, with two long Ni-N bond lengths and two short ones. The enthalpies of combustion for both complexes are over 3600?kJ/mol. The N-N bond lengths in the moieties of hydrazine and azide ligands increase in the coordination process compared to those of the isolated molecules. PMID:24052834

  9. QM and QM/MM Studies of Uranyl Fluorides in the Gas and Aqueous Phases and in the Hydrophobic Cavities of Tetrabrachion

    SciTech Connect

    Odoh, Samuel O.; Walker, Sean M.; Meier, Markus; Stetefeld, Jorg; Schreckenbach, Georg

    2011-04-04

    The structural properties and electronic structures of pentacoordinated uranyl complexes belonging to the [UO鈧侳n(H鈧侽)鈧呪垝n]虏鈭掆伩 series have been studied in the gas and aqueous phases using density functionals with relativistic pseudopotentials and all-electron basis sets in the gas-phase calculations in combination with COSMO in the aqueous phase. In addition, the conformational orientation and structural and electronic properties of [UO鈧侳鈧匽鲁炉 in the hydrophobic cavities of the right-handed coiled-coil (RHCC) protein of tetrabrachion have been determined using the hybrid QM/MM method. Although there is good agreement between the available experimental geometrical parameters and the values obtained in the aqueous phase using pseudopotentials or all-electron basis sets, variation of the uranyl U鈺怬 bond with the number of fluoride ligands is only truly captured after the inclusion of five water molecules in the second coordination sphere around the molecules. The docking procedure used in this work shows that there are only two possible orientations of the uranyl group of [UO鈧侳鈧匽鲁炉 embedded in the hydrophobic cavities of the RHCC protein. The two orientations are exclusively along the axes perpendicular to the protein axial channel with no possible orientation of the uranyl group along the axial channel because of both steric effects and interaction with the alkyl chain of the isoleucine residues pointing into the axial channel. In addition, the embedded complex is always positioned nearer to the isoleucine residues at the N-terminal ends of the hydrophobic cavities. Energy analysis, however, reveals that both conformations can only be observed in cavity 2, the largest hydrophobic cavity. The structural and electronic properties of the ligand embedded in this cavity are very similar to those of the gas-phase structure. A comparable study of [Pt(CN)鈧哴虏炉 and the anticancer drug cisplatin, [PtCl鈧(NH鈧)鈧俔, in cavity 2, revealed the existence of just two orientations for the former, similar to the uranyl complex, and multiple orientations for the latter.

  10. [Thin layer chromatography of coordinated Ag+-complexes of plant diacylglycerols].

    PubMed

    Vereshchagin, A G; Pchelkin, V P

    2003-01-01

    Coordination complexes of unsaturated rac-1,2-diacylglycerols (DAGs) with silver ions were separated by adsorption and reversed-phase TLC (Ag-TLC and Ag-rpTLC, respectively). During the Ag-TLC, the silver ion complexes were shown to be formed by the DAG coordination centers of various structures and only on the adsorbent surface. Separation of the complexes proceeds according to the adsorption mechanism, and there is an inverse exponential functional relationship between the DAG mobility and their double bond number. Meanwhile, during the Ag-rpTLC, the Ag(+)-complexes are formed only with double bonds, only in solution, and at a 1:1 ratio. The complexes are fractionated by partitioning between two liquid phases, and the relationship between the mobility and unsaturation of these complexes is directly proportional. Nevertheless, despite all the differences between the two TLC methods, the polarity of DAGs with a bent configuration of their acyl chains greatly exceeds that of DAGs with the same unsaturation but with the acyl-chain conformation close to extended: it is two to three times greater in Ag-TLC and 30-40% greater in Ag-rpTLC. In addition, the relationship between the mobility and unsaturation of DAG complexes exhibits quantitative rather than qualitative differences in both versions of argentation TLC. Thus, under all conditions of argentation liquid chromatography, the mobility of complexes and, therefore, their polarity are determined not only by their composition (unsaturation), but also by the spatial structure (conformation) of their molecules. PMID:12658996

  11. Actinide immobilization in the subsurface environment by in-situ treatment with a hydrolytically unstable organophosphorus complexant: Uranyl uptake by calcium phytate

    SciTech Connect

    Nash, K.L.; Jensen, M.P.; Schmidt, M.A.

    1997-12-31

    In addition to naturally occurring uranium and thorium, actinide ions exist in the subsurface environment as a result of accidental releases and intentional disposal practices associated with nuclear weapons production. These species present a significant challenge to cost-effective remediation of contaminated environments. An attractive approach to decreasing the probability of actinide migration in the subsurface is to transform the ions into a less mobile form by remote treatment. We have under development a process which relies on a polyfunctional organophosphorus complexant to sequester the mobile metal ions by complexation/cation exchange in the near term, and to subsequently decompose, transforming the actinides into insoluble phosphate mineral forms in the long term. Studies to date include identification of a suitable organophosphorus reagent, profiling of its decomposition kinetics, verification of the formation of phosphate mineral phases upon decomposition of the reagent, and extensive comparison of the actinide uptake ability of the calcium salt of the reagent as compared with hydroxyapatite. In this report, we briefly describe the process with focus on the cation exchange behavior of the calcium salt of the organophosphorus sequestrant.

  12. Surprising coordination for low-valent actinides resembling uranyl(vi) in thorium(iv) organic hybrid layered and framework structures based on a graphene-like (6,3) sheet topology.

    PubMed

    Li, Yuxiang; Weng, Zhehui; Wang, Yanlong; Chen, Lanhua; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2016-01-01

    Three thorium(iv)-based metal-organic hybrid compounds with 2D layered and 3D framework structures exhibiting graphene-like (6,3) sheet topologies were prepared with linkers with threefold symmetry. These compounds contain rare and relatively anisotropic coordination environments for low-valent actinides that are similar to those often observed for high-valent actinide ions. PMID:26672441

  13. Structures and luminescent properties of new uranyl-based hybrid materials

    NASA Astrophysics Data System (ADS)

    Severance, Rachel C.; Vaughn, Shae Anne; Smith, Mark D.; zur Loye, Hans-Conrad

    2011-06-01

    Six uranyl coordination compounds, UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)路2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) were grown as single crystals via hydrothermal synthesis (PYCA = pyrazine-2-carboxylate, PIC = picolinate, NIC = nicotinate, INIC = isonicotinate, and PYTAC = 2-(pyridin-4-yl)thiazole-5-carboxylate) to study their optical properties. All six compounds have been identified via single crystal X-ray diffraction and fully characterized via powder X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. Three of the complexes, 1, 3, and 6, represent new structures, and their synthesis and structural characterization is detailed within. The structures of 2, 4, and 5 have previously been reported in the literature. Coordination polymer 1 crystallizes in the orthorhombic space group Pca21 ( a = 13.5476(5) 脜, b = 6.6047(2) 脜, c = 8.3458(3) 脜), and forms infinite 1-D chains of corner-sharing uranium polyhedra connected into 2-D layers by bridging ligands. Coordination polymer 3 crystallizes in the monoclinic space group Cc ( a = 8.4646(8) 脜, b = 13.0357(11) 脜, c = 11.8955(10) 脜, 尾 = 96.815(2)掳), and forms ligand-bridged 1-D chains. Complex 6 crystallizes in the triclinic space group P-1 ( a = 5.6272(7) 脜, b = 8.9568(10) 脜, c = 10.4673(12) 脜, 伪 = 90.508(2)掳, 尾 = 104.194(2)掳, 纬 = 91.891(2)掳), and consists of isolated uranyl complexes connected via hydrogen bonds. The structures and luminescent properties of UO 2(OH)(PYCA) ( 1), UO 2(PYCA) 2(H 2O)路2H 2O ( 2), UO 2(PIC) 2 ( 3), UO 2(H 2O) 2(NIC) 2 ( 4), UO 2(OH)(HINIC)(INIC) ( 5), and UO 2(PYTAC) 2(H 2O) 2 ( 6) are discussed.

  14. Influence of symmetry on the luminescence and radiative lifetime of nine-coordinate europium complexes.

    PubMed

    Shavaleev, Nail M; Eliseeva, Svetlana V; Scopelliti, Rosario; B黱zli, Jean-Claude G

    2015-09-21

    Homoleptic mononuclear nine-coordinate lanthanum(III) and europium(III) tris-complexes [Ln(N(?)N(?)O)3]穘H2O with two tridentate N-benzylbenzimidazole pyridine-2-carboxylates exhibit a rare C3-symmetry of the lanthanide coordination polyhedron in the solid state, as confirmed by luminescence spectroscopy and by X-ray crystallography (the three N(?)N(?)O ligands are arranged "up-up-up" around the lanthanide ion). The symmetry, however, is changed to the more common C1 upon dissolution of the complexes in dichloromethane, as revealed by luminescence spectroscopy (the three ligands are likely to be arranged "up-up-down"). The new europium complexes emit efficient ligand-sensitized metal-centered luminescence with excited-state lifetimes of 1.56-2.18 ms and quantum yields of 25-41% in the solid and in solution. The change of the symmetry from (a higher) C3 to (a lower) C1 alters the luminescence spectrum, shortens the radiative lifetime, and increases the luminescence efficiency of the europium complexes. PMID:26340341

  15. Coordination geometry around copper in a Schiff-base trinuclear copper complex using EXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Gaur, Abhijeet; Shrivastava, B. D.; Gaur, D. C.; Prasad, J.; Srivastava, K.; Jha, S. N.; Bhattacharyya, D.; Poswal, A.

    2012-05-01

    In the present investigation, we have studied extended X-ray absorption fine structure (EXAFS) spectra of a trinuclear Schiff-base copper complex tetraaqua-di-?3-(N-salicylidene-DL-glutamato)-tricopper(II)heptahydrate, [Cu3(C12H10NO5)2 (H2O)4]. 7H2O, in which three metal sites are present. One metal site is square-pyramidal (4+1) and other two similar metal sites are tetragonally distorted octahedral (4+2). EXAFS has been recorded at the K-edge of copper in the complex at the dispersive EXAFS beamline at 2 GeV Indus-2 synchrotron source at RRCAT, Indore, India. The analysis of EXAFS spectra of multinuclear metal complexes pose some problems due to the presence of many absorbing atoms, even when the absorbing atoms may be of the same element. Hence, using the available crystal structure of the complex, theoretical models have been generated for the different copper sites separately, which are then fitted to the experimental EXAFS data. The two coordination geometries around the copper sites have been determined. The contributions of the different copper sites to the experimental spectrum have been estimated. The structural parameters, which include bond-lengths, coordination numbers and thermal disorders, for the two types of copper sites have been reported. Further, copper has been found to be in +2 oxidation state at these metal sites.

  16. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes.

    PubMed

    Prado, Yoann; Daff茅, Ni茅li; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Gren猫che, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, J茅r么me

    2015-01-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest--and more attractive--systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5鈥塶m 纬-Fe2O3 nanoparticles with the [Co(II)(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination--without nanoparticle aggregation and without complex dissociation--of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude. PMID:26634987

  17. Kinetic and Thermodynamic Stabilization of Metal Complexes by Introverted Coordination in a Calix[6]azacryptand.

    PubMed

    Inthasot, Alex; Brunetti, Emilio; Lejeune, Manuel; Menard, Nicolas; Prang茅, Thierry; Fusaro, Luca; Bruylants, Gilles; Reinaud, Olivia; Luhmer, Michel; Jabin, Ivan; Colasson, Benoit

    2016-03-24

    The Huisgen thermal reaction between an organic azide and an acetylene was employed for the selective monofunctionalization of a X6 -azacryptand ligand bearing a tren coordinating unit [X6 stands for calix[6]arene and tren for tris(2-aminoethyl)amine]. Supramolecular assistance, originating from the formation of a host-guest inclusion complex between the reactants, greatly accelerates the reaction while self-inhibition affords a remarkable selectivity. The new ligand possesses a single amino-leg appended at the large rim of the calixarene core and the corresponding Zn(2+) complex was characterized both in solution and in the solid state. The coordination of Zn(2+) not only involves the tren cap but also the introverted amino-leg, which locks the metal ion in the cavity. Compared with the parent ligand deprived of the amino-leg, the affinity of the new monofunctionalized X6 tren ligand 6 for Zn(2+) is found to have a 10-fold increase in DMSO, which is a very competitive solvent, and with an enhancement of at least three orders of magnitude in CDCl3 /CD3 OD (1:1, v/v). In strong contrast with the fast binding kinetics, decoordination of Zn(2+) as well as transmetallation appeared to be very slow processes. The monofunctionalized X6 tren ligand 6 fully protects the metal ion from the external medium thanks to the combination of a cavity and a closed coordination sphere, leading to greater thermodynamic and kinetic stabilities. PMID:26916610

  18. Axial coordination and conformational heterogeneity of nickel(II) tetraphenylprophyrin complexes with nitrogenous bases

    SciTech Connect

    Jia, S.L.; Song, X.Z.; Ma, J.G.; Shelnutt, J.A.; Jentzen, W.; Shang, M.; Scheidt, W.R.

    1998-08-24

    Axial ligation of nickel(II) 5,10,15,20-tetraphenylporphyrin (NiTPP) with pyrrolidine or piperidine has been investigated using X-ray crystallography, UV-visible spectroscopy, resonance Raman spectroscopy, and molecular mechanics (MM) calculations. Distinct v{sub 4} Raman lines are found for the 4-, 5-, and 6-coordinate species of NiTPP. The equilibrium constants for addition of the first and second pyrrolidine axial ligands are 1.1 and 3.8 M{sup {minus}1}, respectively. The differences in the calculated energies of the conformers having different ligand rotational angles are small so they may coexist in solution. Because of the similarity in macrocyclic structural parameters of these conformers and the free rotation of the axial ligands, narrow and symmetric v{sub 2} and v{sub 8} Raman lines are observed. Nonetheless, the normal-coordinate structural-decomposition analysis of the nonplanar distortions of the calculated structures and the crystal structure of the bis(piperidine) complex reveals a relationship between the orientations of axial ligand(s) and the macrocyclic distortions. For the 5-coordinate complex with the plane of the axial ligand bisecting the Ni-N{sub pyrrole} bonds, a primarily ruffled deformation results. With the ligand plane eclipsing the Ni-N{sub pyrrole} bonds, a mainly saddled deformation occurs. With the addition of the second axial ligand, the small doming of the 5-coordinate complexes disappears, and ruffling or saddling deformations change depending on the relative orientation of the two axial ligands. The crystal structure of the NiTPP bis(piperidine) complex shows a macrocycle distortion composed of wav(x) and wav(y) symmetric deformations, but no ruffling, saddling, or doming. The difference in the calculated and observed distortions results partly from the phenyl group orientation imposed by crystal packing forces. MM calculations predict three stable conformers (ruf, sad, and planar) for 4-coordinate NiTPP, and resonance Raman evidence for these conformers was given previously.

  19. Cation朿ation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    SciTech Connect

    Balboni, Enrica; Burns, Peter C.

    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 cation朿ation 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 cation朿ation 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 癈. - Graphical abstract: Chains of uranium and tungsten polyhedra are connected into a three dimensional framework by cation朿ation 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 cation朿ation interactions. Cation exchange does not alter the structural integrity of the compounds. Cation exchange was successful at room temperature and mild hydrothermal conditions.

  20. Synthesis and reactivity of coordinatively unsaturated halocarbonyl molybdenum PNP pincer complexes.

    PubMed

    de Aguiar, Sara R M M; 謟topcu, 謟g黵; St鰃er, Berthold; Mereiter, Kurt; Veiros, Luis F; Pittenauer, Ernst; Allmaier, G黱ter; Kirchner, Karl

    2014-10-21

    In the present study a series of six-coordinate neutral 16e halocarbonyl Mo(ii) complexes of the type [Mo(PNP(Me)-iPr)(CO)X2] (X = I, Br, Cl), featuring the PNP pincer ligand N,N'-bis(diisopropylphosphino)-N,N'-dimethyl-2,6-diaminopyridine (PNP(Me)-iPr), were prepared and fully characterized. The synthesis of these complexes was accomplished by different methodologies depending on the halide ligands. For X = I and Br, [Mo(PNP(Me)-iPr)(CO)I2] and [Mo(PNP(Me)-iPr)(CO)Br2] were obtained by reacting [Mo(PNP(Me)-iPr)(CO)3] with stoichiometric amounts of I2 and Br2, respectively. In the case of X = Cl, [Mo(PNP(Me)-iPr)(CO)Cl2] was afforded by the reaction of [Mo(CO)4(?-Cl)Cl]2 with 1 equiv. of PNP(Me)-iPr. The equivalent procedure also worked for X = Br. The modification of the 2,6-diaminopyridine scaffold by introducing NMe instead of NH spacers between the aromatic pyridine ring and the phosphine moieties changed the steric properties of the PNP-iPr ligand significantly. While in the present case exclusively neutral six-coordinate complexes of the type [Mo(PNP(Me)-iPr)(CO)X2] were obtained, with the parent PNP-iPr ligand, i.e. featuring NH spacers, cationic seven-coordinate complexes of the type [Mo(PNP-iPr)(CO)3X]X were afforded. Upon treatment of [Mo(PNP(Me)-iPr)(CO)X2] (X = Br, Cl) with Ag(+) in CH3CN, the cationic complexes [Mo(PNP(Me)-iPr)(CO)(CH3CN)X](+) were formed. Halide abstraction from [Mo(PNP(Me)-iPr)(CO)Cl2] in THF-CH2Cl2 afforded [Mo(PNP(Me)-iPr)(CO)(THF)Cl](+). In keeping with the facile synthesis of monocationic complexes preliminary ESI-MS and DFT/B3LYP studies revealed that one halide ligand in complexes [Mo(PNP(Me)-iPr)(CO)X2] is labile forming cationic fragments [Mo(PNP(Me)-iPr)(CO)X](+) which react with molecular oxygen in parallel pathways to yield mono and dioxo Mo(iv) and Mo(vi) species. Structures of representative complexes were determined by X-ray single crystal analyses. PMID:25142749

  1. Complex changes in eye head coordination in progressive lens wearers during driving.

    PubMed

    Rifai, Katharina; Wahl, Siegfried

    2015-09-01

    In natural uncorrected vision in young observers, a given eccentric fixation target at any distance can be fixated by various combinations of eye and head position with an identical resulting visual input. The properties of the visual input do not depend on the rotational status of the eye. In contrast, the quality of visual input strongly depends on eye position in progressive lens wearers. A specific eye position provides clear, focused vision at a specific distance only. Thus for fixating a target with clear vision, one specific optimal combination of eye and head position exists in a progressive lens wearer. Especially in challenging visual situations a change in eye head coordination is therefore a prerequisite for successful task performance. In modern everyday life, car driving is one of the strongest visual challenges, where a large field of view is scanned permanently with coordinated eye-head-movements. Although free to move their gaze and head, car driver's fixational behavior is constantly determined by the tasks requirements. In progressive lens wearers, specific head movements might therefore be enforced during driving. In the present study, changes in head-movement behavior are shown in progressive lens wearers during driving compared to controls. Progressive lens wearers and controls performed a real-world driving task, each of them driving along the same predefined urban round course track in Stuttgart downtown. Eye head coordination of progressive lens wearers was analyzed with respect to three main parameters: head gain, temporal properties in head movements and variance in head movements. Changes in head movement behavior, specific to progressive lens wearers, were determined in all three parameters, pointing towards complex changes in eye-head-coordination induced by the modification of optical properties in a progressive lens. Therefore, the varying optical properties of a progressive lens can be interpreted as visual learning signal for eye-head-coordinated movements. Meeting abstract presented at VSS 2015. PMID:26326965

  2. Low-Coordinate First Row Early Transition Metal Complexes Stabilized by Modified Terphenyl Ligands

    NASA Astrophysics Data System (ADS)

    Boynton, Jessica Nicole

    The research in this dissertation is focused on the synthesis, structural, and magnetic characterization of two-coordinate open shell (d1-d4) transition metal complexes. Background information on this field of endeavor is provided in Chapter 1. In Chapter 2 I describe the synthesis and characterization of the mononuclear chromium (II) terphenyl substituted primary amido complexes and a Lewis base adduct. These studies suggest that the two-coordinate chromium complexes have significant spin-orbit coupling effects which lead to moments lower than the spin only value of 4.90 muB owing to the fact that lambda (the spin orbit coupling parameter) is positive. The three-coordinated complex 2.3 had a magnetic moment of 3.77 muB. The synthesis and characterization of the first stable two-coordinate vanadium complexes are described in Chapter 3. The values suggest a significant spin orbital angular momentum contribution that leads to a magnetic moment that is lower than their spin only value of 3.87 muB. DFT calculations showed that the major absorptions in their UV-Vis spectra were due to ligand to metal charge transfer transitions. The titanium synthesis and characterization of the bisamido complex along with its three-coordinate titanium(III) precursor are described in Chapter 4. Compound 4.1 was obtained via the stoichiometric reaction of LiN(H)AriPr 6 with the Ti(III) complex TiCl3 *2NMe 3 in trimethylamine. The precursor 4.1 has trigonal pyramidal coordination at the titanium atom, with bonding to two amido nitrogens and a chlorine as well as a secondary interaction to a flanking aryl ring of a terphenyl substituent. Compound 4.2 displays a very distorted four-coordinate metal environment in which the titanium atom is bound to two amido nitrogens and to two carbons from a terphenyl aryl ring. This structure is in sharp contrast to the two-coordinate linear structure that was observed in its first row metal (V-Ni) analogs. The synthesis and characterization of mononuclear chromium(II) terphenyl primary substituted thiolate complexes are described in Chapter 5. Reaction of the terphenyl primary thiolate lithium derivatives LiSAriPr4 and LiSArMe6 with CrCl2THF2 in a 2:1 ratio afforded complexes 5.1 and 5.2, which are the very rare examples of chromium(II) thiolates with quasi-two-coordination at the metal center. Both deviate from linearity and have S-Cr-S angles of 111.02(3)掳 and 107.86(3) 掳 with secondary Cr-C(aryl ring) interactions of ca. 2.115 A and 1.971 A respectively. The initial work on titanium and vanadium terphenyl thiolates is described in Appendix I and II. In Chapter 6 I show that the reaction of K2COT (COT= 1,3,5,7-cyclooctatetraene, C8H8) with an aryl chromium(II) halide gave (CrAriPr 4)2(mu2-n3:n4-COT) (6.1) in which a non-planar COT ring is complexed between two CrAriPr4 moieties -- a configuration previously unknown for chromium complexes of COT. OneCr2+ ion is bonded primarily to three COT carbons (Cr--C= 2.22-2.30 A ) as well as an ipso carbon (Cr-C= ca. 2.47 A) from a flanking aryl ring of its terphenyl substituent. The otherCr2+ ion bonds to an ipso carbon (Cr-C= ca. 2.53 A) from its terphenyl substituent as well as four COT carbons (Cr--C= 2.24-2.32 A). The COT carbon-carbon distances display an alternating pattern, consistent with the non-planarity and non-aromatic character of the ring. The magnetic properties of 6.1 indicate that theCr2+ ions have a high-spin d4 configuration with S = 2. The temperature dependence of the magnetism indicates that their behavior is due to zero-field splitting of the S = 2 state. Attempts to prepare 6.1 by the direct reaction of quintuple-bonded (CrAriPr4)2 with COT were unsuccessful. (Abstract shortened by UMI.)

  3. Complexation of Lanthanides with Glutaroimide-dioxime: Binding Strength and Coordination Modes.

    PubMed

    Ansari, Seraj A; Yang, Yanqiu; Zhang, Zhicheng; Gagnon, Kevin J; Teat, Simon J; Luo, Shunzhong; Rao, Linfeng

    2016-02-01

    The complexation of lanthanides (Nd(3+) and Eu(3+)) with glutaroimide-dioxime (H2L), a cyclic imide dioxime ligand that has been found to form stable complexes with actinides (UO2(2+) and NpO2(+)) and transition metal ions (Fe(3+), Cu(2+), etc.), was studied by potentiometry, absorption spectrophotometry, luminescence spectroscopy, and microcalorimetry. Lanthanides form three successive complexes, M(HL)(2+), M(HL)L, and M(HL)2(+) (where M stands for Nd(3+)/Eu(3+) and HL(-) stands for the singly deprotonated ligand). The enthalpies of complexation, determined by microcalorimetry, show that the formation of these complexes is exothermic. The stability constants of Ln(3+)/H2L complexes are several orders of magnitude lower than that of the corresponding Fe(3+)/H2L complexes but are comparable with that of UO2(2+)/H2L complexes. A structure of Eu(3+)/H2L complex, identified by single-crystal X-ray diffractometry, shows that the ligand coordinates to Eu(3+) in a tridentate mode, via the two oxygen atoms of the oxime group and the nitrogen atom of the imide group. The relocation of protons of the oxime groups (-CH鈺怤-OH) from the oxygen to the nitrogen atom, and the deprotonation of the imide group (-CH-NH-CH-) result in a conjugated system with delocalized electron density on the ligand (-O-N-C-N-C-N-O-) that forms strong complexes with the lanthanide ions. PMID:26765525

  4. Talking about the institutional complexity of the integrated rehabilitation system梩he 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

  5. Reversible binding of water, methanol, and ethanol to a five-coordinate ruthenium(II) complex.

    PubMed

    Ma, Erin S F; Patrick, Brian O; James, Brian R

    2013-03-28

    The known green, five-coordinate, square-pyramidal trans-RuCl(2)(P-N)(PPh(3)) complex reversibly binds water, MeOH and EtOH in the vacant coordination site in the solid state and in CH(2)Cl(2) solution to give pink adducts (P-N = o-diphenylphosphino-N,N'-dimethylaniline). The adducts are well characterized, including X-ray analysis of the aqua complex, trans-RuCl(2)(P-N)(PPh(3))(H(2)O), which crystallizes in two different benzene-solvated forms. Comparison of the structural data with those determined previously for the binding of H(2)S, thiols, and H(2), which form cis-RuX(2)(P-N)(PPh(3))L products (X = Cl, Br; L = a S-ligand or H(2)) reveals the trans-influence trend P > H(2)S ~ thiols > H(2) > Cl ~ Br > H(2)O. Thermodynamic data for the binding of water were estimated in solution by UV-Vis spectroscopy, and ?H(o) data for the aqua and alcohol adducts in the solid state were obtained by differential scanning calorimetry. Inclusion of published data for the S-ligand adducts reveals the thermal stability trend of the solid complexes as MeSH > MeOH > H(2)S > H(2)O > EtSH > EtOH. PMID:23344393

  6. Weak coordination of neutral S- and O-donor proximal ligands to a ferrous porphyrin nitrosyl. Characterization of 6-coordinate complexes at low T.

    PubMed

    Martirosyan, G G; Kurtikyan, T S; Azizyan, A S; Iretskii, A V; Ford, P C

    2013-04-01

    The interaction of the S- and O-donor ligands tetrahydrothiophen (THT) and tetrahydrofuran (THF) with the ferrous nitrosyl complex Fe(TTP)(NO) (TTP(2-) is meso-tetra-p-tolyl-porphyrinatodianion) was studied at various temperatures both in solid state and solution using electronic and infrared absorption spectroscopy. Upon addition of these ligands to a cryostat containing sublimed layers of Fe(TTP)(NO), no complex formation was detected at room temperature. However, upon lowering the temperature, spectral changes were observed that are consistent with ligand binding in axial position trans to the NO (the proximal site) and formation of the six-coordinate adducts. Analogous behavior was observed in solution. In both media, the six-coordinate adducts are stable only at low temperature and dissociate to the 5-coordinate nitrosyl complexes upon warming. The NO stretching frequencies of the six-coordinate thioether and ether complexes were recorded and binding constants for the weak bonding of proximal THF and THT ligands were determined from the spectral changes. These parameters are compared with those obtained for the N-donor ligand pyrrolidine. PMID:23376554

  7. Redox-triggered on/off coordination of a bridgehead nitrogen donor in a tripodal iron complex.

    PubMed

    W鰎l, Stefan; Hellwinkel, Dieter; Pritzkow, Hans; Kr鋗er, Roland

    2003-10-01

    We report the unprecedented redox-triggered on/off coordination of a bridgehead nitrogen donor in an iron complex of the tripodal ligand 2,2',2''-nitrilotribenzoate; the complex is an efficient redox catalyst for H2O2 oxidation of hydroquinone while complexes of related ligands are inactive. PMID:14587754

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

    SciTech Connect

    Belfiore, L.A.; McCurdie, M.P.; Ueda, E.

    1993-12-06

    d-Block transition-metal-containing polymer blends which form coordination complexes are the focus of this research. The model compounds are Co chloride hexahydrate, Ni acetate tetrahydrate, and the dimer of dichlorotricarbonylruthenium (II). The ligand is poly (4-vinylpyridine), P4VP, or copolymers that contain 4-vinylpyridine repeat units. Differential scanning calorimetry suggests that the glass transition temperature (gtt) of the polymeric ligand(s) is enhanced by these d-block metal salts in binary and ternary blends. Co and Ni salts function as transition-metal compatibilizers for two immiscible copolymers of styrene with 4-vinylpyridine and butyl methacrylate with 4-vinylpyridine. At the molecular level, FTIR of P4VP-Ru precipitates reveals that the pyridine nitrogen lone pair coordinates to the metal center and strengthens Ru-carbonyl bonds in the polymeric complex. IR absorption frequencies of the CO ligands are consistent with {pi}-backbonding between the t{sub 2g} molecular orbitals of the metal in the octahedral point group and the {pi}* antibonding orbitals of CO. High-resolution C-13 solid-state NMR spectroscopy identifies at least two, and possibly three, carbonyl signals in the undiluted pseudooctahedral Ru dimer via the Bloch-decay pulse sequence. In the polymeric complex, carbonyl C-13 magnetization unique to the Ru salt is generated via intermolecular polarization transfer from the proton spin manifold of poly(4-vinylpyridine) using a cross-polarization thermal mixing time of 2 ms. Since there are no protons in the Ru dimer, the observation of energy-conserving H-1/C-13 spin diffusion between dissimilar molecules under matched Hartmann-Hahn spin-lock conditions argues convincingly that heteronuclear dipolar distances are small enough for the proposed polymeric complex to form. Thermodynamic interpretation of ligand field stabilization energies appropriate to tetrahedral Co complexes is employed to estimate the synergistic enhancement of the gtt.

  9. Adsorption of Uranyl ions on Amine-functionalization of MIL-101(Cr) Nanoparticles by a Facile Coordination-based Post-synthetic strategy and X-ray Absorption Spectroscopy Studies

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Yong; Zhang, Na; Zhang, Linjuan; Fang, Yongzheng; Deng, Wei; Yu, Ming; Wang, Ziqiang; Li, Lina; Liu, Xiyan; Li, Jingye

    2015-09-01

    By a facile coordination-based post-synthetic strategy, the high surface area MIL-101(Cr) nanoparticles was functionallized by grafting amine group of ethylenediamine (ED) on coordinatively unsaturated Cr(III) centers, yielding a series of ED-MIL-101(Cr)-based adsorbents and their application for adsorption of U(VI) from aqueous solution were also studied. The obtained ED-functionallized samples with different ED contents were characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), FTIR, elemental analysis (EA) and N2 adsorption and desorption isothermal. Compared with the pristine MIL-101(Cr) sorbents, the ED-functionallized MIL-101(Cr) exhibits significantly higher adsorption capacity for U(VI) ions from water with maximum adsorption capacities as high as 200?mg/g (corresponding to 100% extraction rate) at pH of 4.5 with ED/Cr ratio of 0.68 and the sorbed U(VI) ions can easily be desorbed at lower pH (pH???2.0). The adsorption mode of U(VI) ions and effects of grafted ED on the MIL-101(Cr) frameworks were also been studied by X-ray absorption spectroscopy (XAS). We believe that this work establishes a simple and energy efficient route to a novel type of functional materials for U(VI) ions extraction from solution via the post-synthetic modification (PSM) strategy.

  10. Adsorption of Uranyl ions on Amine-functionalization of MIL-101(Cr) Nanoparticles by a Facile Coordination-based Post-synthetic strategy and X-ray Absorption Spectroscopy Studies

    PubMed Central

    Zhang, Jian-Yong; Zhang, Na; Zhang, Linjuan; Fang, Yongzheng; Deng, Wei; Yu, Ming; Wang, Ziqiang; Li, Lina; Liu, Xiyan; Li, Jingye

    2015-01-01

    By a facile coordination-based post-synthetic strategy, the high surface area MIL-101(Cr) nanoparticles was functionallized by grafting amine group of ethylenediamine (ED) on coordinatively unsaturated Cr(III) centers, yielding a series of ED-MIL-101(Cr)-based adsorbents and their application for adsorption of U(VI) from aqueous solution were also studied. The obtained ED-functionallized samples with different ED contents were characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), FTIR, elemental analysis (EA) and N2 adsorption and desorption isothermal. Compared with the pristine MIL-101(Cr) sorbents, the ED-functionallized MIL-101(Cr) exhibits significantly higher adsorption capacity for U(VI) ions from water with maximum adsorption capacities as high as 200鈥塵g/g (corresponding to 100% extraction rate) at pH of 4.5 with ED/Cr ratio of 0.68 and the sorbed U(VI) ions can easily be desorbed at lower pH (pH鈥夆墹鈥2.0). The adsorption mode of U(VI) ions and effects of grafted ED on the MIL-101(Cr) frameworks were also been studied by X-ray absorption spectroscopy (XAS). We believe that this work establishes a simple and energy efficient route to a novel type of functional materials for U(VI) ions extraction from solution via the post-synthetic modification (PSM) strategy. PMID:26354407

  11. Adsorption studies of divalent, dinuclear coordination complexes as molecular spacers on SWCNTs.

    PubMed

    Alston, Jeffrey R; Banks, David J; McNeill, Chauncey X; Mitchell, James B; Popov, Leonid D; Shcherbakov, Igor N; Poler, J C

    2015-11-28

    In order to enhance the electrical energy storage capabilities of nanostructured carbon materials, inter-particle spacer strategies are needed to maintain ion-accessible surface area between the nanoparticles. This paper presents a comparison between different classes of divalent, dinuclear coordination complexes which both show strong adsorption to SWCNTs and have molecular spacer properties that maintain electrochemical activity. We find that a novel, dinuclear zinc hydrazone complex binds as an ion-pair at very high loading while not inducing significant aggregation as compared to our previously studies of dinuclear ruthenium complexes. These conclusions are supported by conductivity and dispersion stability data. Moreover, since zinc is an earth abundant metal, these complexes can be used as components in sustainable energy storage materials. Binding kinetics and binding equilibrium data are presented. Modeling of the adsorption isotherm is best fit with the BET model. Kinetics data support an independent binding model. Preliminary capacitance and membrane resistance data are consistent with the complexes acting as molecular spacers between the SWCNTs in a condensed thin film. PMID:26457656

  12. Converting between the oxides of nitrogen using metal-ligand coordination complexes.

    PubMed

    Timmons, Andrew J; Symes, Mark D

    2015-10-01

    The oxides of nitrogen (chiefly NO, NO3(-), NO2(-) and N2O) are key components of the natural nitrogen cycle and are intermediates in a range of processes of enormous biological, environmental and industrial importance. Nature has evolved numerous enzymes which handle the conversion of these oxides to/from other small nitrogen-containing species and there also exist a number of heterogeneous catalysts that can mediate similar reactions. In the chemical space between these two extremes exist metal-ligand coordination complexes that are easier to interrogate than heterogeneous systems and simpler in structure than enzymes. In this Tutorial Review, we will examine catalysts for the inter-conversions of the various nitrogen oxides that are based on such complexes, looking in particular at more recent examples that take inspiration from the natural systems. PMID:26158348

  13. The crystal design of polar one-dimensional hydrogen-bonded copper coordination complexes.

    PubMed

    Takahashi, Kiyonori; Hoshino, Norihisa; Takeda, Takashi; Satomi, Koichiro; Suzuki, Yasutaka; Noro, Shin-Ichiro; Nakamura, Takayoshi; Kawamata, Jun; Akutagawa, Tomoyuki

    2016-02-16

    Polar crystals exhibiting second-order harmonic generation (SHG) were designed by adjusting the intermolecular interactions of mononuclear Cu(ii) complexes in which one H2O, two pyridines (py), and two p-substituted benzoate (p-RBA) ligands (R = F, Cl, Br, I, CH3, and OCH3) were coordinated to a Cu(ii) ion, forming a penta-coordinated asymmetric [Cu(ii)(p-RBA)2(py)2(H2O)] mononuclear structure with a permanent dipole moment along the direction of the Cu-OH2 coordination axis. Each asymmetric [Cu(ii)(p-RBA)2(py)2(H2O)] complex formed a polar one-dimensional hydrogen-bonded chain, [Cu(ii)(p-RBA)2(py)2(H2O)]?, between the non-coordinated carboxylate oxygen atom of the p-RBA ligand and the hydrogen atom of the H2O molecule. The formation of a polar crystal depended on the arrangement of polar hydrogen-bonded chains; the parallel arrangement of each polar chain resulted in a polar crystal. The chemical design of the R group in the p-RBA ligand enabled tuning of the magnitude of the interchain interactions and crystal polarity; polar crystals were obtained using p-RBA ligands with R = Cl, Br, I, and OCH3. In contrast, apolar crystals were grown from complexes containing p-RBA ligands with R = F and CH3. In all crystals, a polar two-dimensional (2D) layer constructed from the parallel polar [Cu(ii)(p-RBA)2(py)2(H2O)]? chain arrangement was formed based on weak van der Waals C-H(-)O- interactions between the hydrogen atom of py and the carboxylate oxygen atom of the p-RBA ligand. Weak interlayer halogen (X)? and multipoint C-H? interactions played important roles in forming parallel arrangements of polar 2D layers and polar crystals, but there were no effective intermolecular interactions between the polar 2D layers in apolar [Cu(ii)(p-FBA)2(py)2(H2O)] and [Cu(ii)(p-CH3BA)2(py)2(H2O)] crystals. The magnitudes of the interlayer interactions in the polar crystals were larger than those in the apolar ones because of the effective intermolecular interactions. The SHG intensities of the four polar crystals were approximately 0.7 times larger than that of sucrose. PMID:26791265

  14. Core-Shell Coating Silicon Anode Interfaces with Coordination Complex for Stable Lithium-Ion Batteries.

    PubMed

    Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Xu, Na; Zhang, Qi; Li, Qun; Yan, Chenglin

    2016-03-01

    In situ core-shell coating was used to improve the electrochemical performance of Si-based anodes with polypyrrole-Fe coordination complex. The vast functional groups in the organometallic coordination complex easily formed hydrogen bonds when in situ modifying commercial Si nanoparticles. The incorporation of polypyrrole-Fe resulted in the conformal conductive coating surrounding each Si nanoparticle, not only providing good electrical connection to the particles but also promoting the formation of a stable solid-electrolyte-interface layer on the Si electrode surface, enhancing the cycling properties. As an anode material for Li-ion batteries, modified silicon powders exhibited high reversible capacity (3567 mAh/g at 0.3 A/g), good rate property (549.12 mAh/g at 12 A/g), and excellent cycling performance (reversible capacity of 1500 mAh/g after 800 cycles at 1.2 A/g). The constructed novel concept of core-shell coating Si particles presented a promising route for facile and large-scale production of Si-based anodes for extremely durable Li-ion batteries, which provided a wide range of applications in the field of energy storage of the renewable energy derived from the solar energy, hydropower, tidal energy, and geothermal heat. PMID:26863089

  15. Normal coordinate analysis of copper complexes with 1-(2-pyridylazo)-2-naphthol

    NASA Astrophysics Data System (ADS)

    Dro?d?ewski, Piotr M.

    Two copper complexes with the title ligand have been investigated by i.r. and Raman spectroscopy: Cu(PAN)Cl and Cu(PAN) 2. Vibrational band assignments have been supported by normal coordinate analyses carried out using two models for each compound. The first model better described the ligand vibrations of the complex whereas the second one was applied for a more precise description of the coordinated metal environment. The strongly coupled character of all skeletal vibrations has been indicated. The copper-ligand stretching vibrations have been found to contribute mainly in the following i.r. active modes: ?(Cu?O) = 327, ?(Cu?N. azo) = 211 cm -1 for the Cu(PAN) 2 molecule where the pyridine nitrogen is not involved with metal chelation, and ?(Cu?O) = 337, ?(Cu?N py) = 274, ?(Cu?N azo) = 184, ?(Cu?Cl) = 298 and 236 cm -1 for the [Cu(PAN)Cl] 2 dimer with two halogen bridging atoms.

  16. Heterobimetallic coordination polymers involving 3d metal complexes and heavier transition metals cyanometallates

    NASA Astrophysics Data System (ADS)

    Peresypkina, Eugenia V.; Samsonenko, Denis G.; Vostrikova, Kira E.

    2015-04-01

    The results of the first steps in the design of coordination polymers based on penta- and heptacyanometallates of heavier d transitions metals are presented. The 2D structure of the coordination polymers: [{Mn(acacen)}2Ru(NO)(CN)5]n and two complexes composed of different cyanorhenates, [Ni(cyclam)]2[ReO(OH)(CN)4](ClO4)2(H2O)1.25 and [Cu(cyclam)]2[Re(CN)7](H2O)12, was confirmed by single crystal XRD study, the rhenium oxidation state having been proved by the magnetic measurements. An amorphism of [M(cyclam)]3[Re(CN)7]2 (M=Ni, Cu) polymers does not allow to define strictly their dimensionality and to model anisotropic magnetic behavior of the compounds. However, with high probability a honey-comb like layer structure could be expected for [M(cyclam)]3[Re(CN)7]2 complexes, studied in this work, because such an arrangement is the most common among the bimetallic assemblies of hexa- and octacyanometallates with a ratio [M(cyclam)]/[M(CN)n]=3/2. For the first time was prepared and fully characterized a precursor (n-Bu4N)2[Ru(NO)(CN)5], soluble in organic media.

  17. 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

    2015-07-01

    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 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

  18. 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 Presler抯 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

  19. Two photon absorption properties of four coordinated transition metal complexes of tetraarylazadipyrromethene compounds.

    PubMed

    Akh黶eyin, E; T黵kmen, O; K黭鰖, B; Y?lmaz, H; Karatay, A; Sevin, G; Xu, K; Hayvali, M; Yaglioglu, H G

    2016-02-01

    New tetraarylazadipyrromethene metal complexes with four coordinate metals (cobalt(ii), nickel(ii), copper(ii) and zinc(ii)) and with three moieties (4-methylphenyl,4-methoxyphenyl and 1-naphthyl) were designed and synthesized targeting applications utilizing two photon absorption. The effects of metals with filled or unfilled d orbitals and substituents with various electron donor properties on the charge transfer mechanism and two photon absorption properties of tetraarylazadipyrromethene compounds were investigated by ultrafast pump-probe spectroscopy and open aperture Z-scan experiments as well as density functional theory (DFT) calculations. Ultrafast transient absorption spectra provide evidence of an efficient photoinduced intramolecular charge transfer between the ligand and metals which is independent of filled or unfilled d orbitals of metals. Although zinc has filled d orbitals, its complexes possess an absorption maximum including a shoulder which is attributed to partial ligand to metal L(?) ? M(d*) charge transfer character (LMCT). Due to the charge transfer mechanism, metal complexes of tetraarylazadipyrromethene compounds exhibited two photon absorption properties in the femtosecond regime at 800 nm wavelength. The greatest two photon absorption cross section value was measured as 2690 GM for Zn(L(2))2 and 2374 GM for Co(L(3))2 complexes. PMID:26791958

  20. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

    PubMed Central

    Prado, Yoann; Daff茅, Ni茅li; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Gren猫che, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, J茅r么me

    2015-01-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest鈥攁nd more attractive鈥攕ystems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5鈥塶m 纬-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination鈥攚ithout nanoparticle aggregation and without complex dissociation鈥攐f the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude. PMID:26634987

  1. Adsorption of uranyl on hydroxylated 伪-SiO鈧(001): a first-principle study.

    PubMed

    Wang, Hui; Chai, Zhifang; Wang, Dongqi

    2015-01-28

    The adsorption of [UO2(H2O)5](2+) on a hydroxylated 伪-SiO2(001) surface was studied by periodic density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The effects of pH, CO2, aqua solution and anionic ligands (OH(-), NO3(-) and Cl(-)) on the adsorption geometry and stability were investigated. The results show that the adsorption of uranyl on a hydroxylated 伪-SiO2(001) surface leads to the formation of inner-sphere complexes, in which the bidentate complex at the double deprotonated site is most favored. The binding strengths of bidentate and monodentate complexes at the same site are similar, and they become weaker as the number of protons increases at the adsorption site, indicating an enhancement of the adsorption strength at higher pH values within a certain range. Strong chemical interaction plays an important role in all inner-sphere complexes. The hydrogen bonds are formed between uranyl and the hydroxylated surface in all inner- and outer-sphere complexes. The presence of CO2 weakens the adsorption of uranyl on the surface by forming uranyl carbonate (CO3(2-), HCO3(-)) complexes. The effect of the anion ligands depends on their charged state and their concentration in solutions. The explicit treatment of water environment in the models has a slight effect on the adsorption configuration. These results are consistent with the experimental observations. PMID:25437449

  2. Enhanced environmental detection of uranyl compounds based on luminescence characterization

    NASA Astrophysics Data System (ADS)

    Nelson, Jean Dennis

    Uranium (U) contamination can be introduced to the environment as a result of mining and manufacturing activities related to nuclear power, detonation of U-containing munitions (DoD), or nuclear weapons production/processing (DOE facilities). In oxidizing environments such as surface soils, U predominantly exists as U(VI), which is highly water soluble and very mobile in soils. U(VI) compounds typically contain the UO22+ group (uranyl compounds). The uniquely structured and long-lived green luminescence (fluorescence) of the uranyl ion (under UV radiation) has been studied and remained a strong topic of interest for two centuries. The presented research is distinct in its objective of improving capabilities for remotely sensing U contamination by understanding what environmental conditions are ideal for detection and need to be taken into consideration. Specific focuses include: (1) the accumulation and fluorescence enhancement of uranyl compounds at soil surfaces using distributed silica gel, and (2) environmental factors capable of influencing the luminescence response, directly or indirectly. In a complex environmental system, matrix effects co-exist from key soil parameters including moisture content (affected by evaporation, temperature and humidity), soil texture, pH, CEC, organic matter and iron content. Chapter 1 is a review of pertinent background information and provides justification for the selected key environmental parameters. Chapter 2 presents empirical investigations related to the fluorescence detection and characterization of uranyl compounds in soil and aqueous samples. An integrative experimental design was employed, testing different soils, generating steady-state fluorescence spectra, and building a comprehensive dataset which was then utilized to simultaneously test three hypotheses: The fluorescence detection of uranyl compounds is dependent upon (1) the key soil parameters, (2) the concentration of U contamination, and (3) time of analysis, specifically following the application of silica gel enhancing material. A variety of statistical approaches were employed, including the development of multiple regression models for predicting both intensity and band structure responses. These statistical models validated the first two listed hypotheses, while the third hypothesis was not supported by this dataset. The combination of inadequate moisture levels and reaction times (? 24 hrs) greatly limited the detection of varying levels of U, depending on the soil.

  3. Thermal expansion and structural complexity of Ba silicates with tetrahedrally coordinated Si atoms

    NASA Astrophysics Data System (ADS)

    Gorelova, Liudmila A.; Bubnova, Rimma S.; Krivovichev, Sergey V.; Krzhizhanovskaya, Maria G.; Filatov, Stanislav K.

    2016-03-01

    Thermal expansion of Ba silicates with tetrahedrally coordinated Si atoms in the temperature range of 25-1100 掳C had been studied by high-temperature X-ray powder diffraction. The volume thermal expansion coefficients (TECs) are in the range 41-50脳10-6 掳C-1 with an average value of <伪V > = 45 脳10-6 掳C-1. In the structures with chain and layered silicate anions, thermal expansion is anisotropic: the direction of maximal TEC is parallel to the extension of the zweier chains of silicate tetrahedra, which are strained owing to the interactions with Ba2+. The strain is released during thermal expansion due to the increasing effective size of Ba2+ induced by thermal vibrations. Information-theoretic analysis of the structural and topological complexities of Ba silicates indicates that their structural complexity is a function of the topological complexity of their silicate anions. The latter displays a non-linear behaviour with increasing SiO2 content (=the increasing degree of polymerization and increasing dimensionality): it starts from simple topologies, reaches a maximum at topologies of intermediate complexity, and ends up at simple topologies again. The specificity of the interactions of Ba2+ with the silicate anions results in higher complexity of high-temperature 伪-BaSi2O5 compared to that of low-temperature 尾-BaSi2O5. This uncommon behaviour may be explained by the vibrational advantages provided by flatter and more complex silicate layers in the 伪-phase, which overcome negative differences in configurational entropies of the two modifications apparent in the differences of their structural Shannon information.

  4. Metal carbonyl complexes of phosphaamidines. Coordinative integrity detected in C-amino(?(3),?(2))-phosphaalkene isomers coordinated through n(P) HOMO-1 donor orbitals.

    PubMed

    Masuda, Jason D; Boer, Ren T

    2016-02-01

    Metal(0) complexes L(Cr,Mo,W)(CO)5 have been prepared from 1,3-bis(2,6-diisopropylphenyl)-2-(4-methylphenyl)-3-aza-1(?(3),?(2))-phosphapropene and 1,3-bis(2,6-diisopropylphenyl)-2-(4-methoxyphenyl)-3-aza-1(?(3),?(2))-phosphapropene using standard methods. Full characterization of four products and crystal structures of these complexes as well as the methoxyphenyl-phosphapropene are reported. The ligands coordinate ?P, common for simple phosphaalkenes, despite the strongly-perturbing amino substitution at the double bond C atoms. Analyses of the NMR and vibrational spectroscopic data reveal that the complexes have very similar character to similarly-coordinated phosphaalkenes, with strong ?-donor character. The presence of some net ?-interactions (acceptor or donor) is indicated by structures in which the ligands coordinate fully eclipsed with the M-CO groups. The synthetic and structural results have been augmented by B3PW91/LANL2DZ calculations that reproduce the structures of the Cr complexes accurately. The calculated vibrational spectra are used to confirm the assignment of the ?(C[triple bond, length as m-dash]O) vibrational data. Detailed orbital interaction diagrams based on DFT calculations are reported for the title complexes as well as for the Cr(CO)5 complex of Mes-P[double bond, length as m-dash]CPh2. The electronic absorption spectra of the title complexes have intense low-energy absorptions ranging from 24?500 to 25?300 cm(-1), which can be interpreted qualitatively using the DFT results. PMID:26485276

  5. Bimetallic Complexes Supported by a Redox-Active Ligand with Fused Pincer-Type Coordination Sites.

    PubMed

    Wang, Denan; Lindeman, Sergey V; Fiedler, Adam T

    2015-09-01

    The remarkable chemistry of mononuclear complexes featuring tridentate, meridionally chelating "pincer" ligands has stimulated the development of ligand frameworks containing multiple pincer sites. Here, the coordination chemistry of a novel pentadentate ligand (L(N3O2)) that provides two closely spaced NNO pincer-type compartments fused together at a central diarylamido unit is described. The trianionic L(N3O2) chelate supports homobimetallic structures in which each M(II) ion (M = Co, Cu, Zn) is bound in a meridional fashion by the bridging diarylamido N atom and O,N-donors of the salicyaldimine arms. The metal centers are also coordinated by a mono- or bidentate auxiliary ligand (L(aux)), resulting in complexes with the general form [M2(L(N3O2))(L(aux))2](+) (where L(aux) = 1-methyl-benzimidazole (1MeBI), 2,2'-bipyridine (bpy), 4,4'-dibromo-2,2'-bipyridine (bpy(Br2)), or (S)-2-(4-isopropyl-4,5-dihydrooxazolyl)pyridine (S-(iPr)OxPy)). The fused nature of the NNO pincer sites results in short metal-metal distances ranging from 2.70 for [Co2(L(N3O2)) (bpy)2](+) to 3.28 for [Zn2(L(N3O2)) (bpy)2](+), as revealed by X-ray crystallography. The complexes possess C2 symmetry due to the twisting of the aryl rings of the ?-NAr2 core; spectroscopic studies indicate that chiral L(aux) ligands, such as S-(iPr)OxPy, are capable of controlling the helical sense of the L(N3O2) scaffold. Since the four- or five-coordinate M(II) centers are linked solely by the amido moiety, each features an open coordination site in the intermetallic region, allowing for the possibility of metal-metal cooperativity in small-molecule activation. Indeed, the dicobalt(II) complex [Co2(L(N3O2)) (bpy(Br2))2](+) reacts with O2 to yield a dicobalt(III) species with a ?-1,2-peroxo ligand. The bpy-containing complexes exhibit rich electrochemical properties due to multiple metal- and ligand-based redox events across a wide (3.0 V) potential window. Using electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT), it was determined that one-electron oxidation of [Co2(L(N3O2)) (bpy)2](+) results in formation of a S = 1/2 species with a L(N3O2)-based radical coupled to low-spin Co(II) centers. PMID:26280846

  6. Coordination Complexes of Decamethylytterbocene with4,4'-Disubstituted Bipyridines: An Experimental Study of Spin Coupling inLanthanide Complexes

    SciTech Connect

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

    2005-12-08

    The paramagnetic 1:1 coordination complexes of (C5Me5)2Ybwith a series of 4,4'-disubstituted bipyridines, bipy-X, where X is Me,tert-Bu, OMe, Ph, CO2Me, and CO2Et have been prepared. All of thecomplexes are paramagnetic and the values of the magnetic susceptibilityas a function of temperature show that these values are less thanexpected for the cation, [(C5Me5)2Yb(III)(bipy-X)]+, which have beenisolated as the cation-anion ion-pairs[(C5Me5)2Yb(III)(bipy-X)]+[(C5Me5)2YbI2]f fnfn where X is CO2Et, OMe andMe. The 1H NMR chemical shifts (293 K) for the methine resonances locatedat the 6,6' site in the bipy-X ring show a linear relationship with thevalues of chiT (300 K) for the neutral complexes which illustrates thatthe molecular behavior does not depend upon the phase with one exception,viz., (C5Me5)2Yb(bipy-Me). Single crystals of the 4,4'-dimethylbipyridinecomplex undergo an irreversible, abrupt first order phase change at 228 Kthat shatters the single crystals. The magnetic susceptibility,represented in a delta vs. T plot, on this complex, in polycrystallineform undergoes reversible abrupt changes in the temperature regime 205 -212 K, which is suggested to be due to the way the individual molec ularunits pack in the unit cell. A qualitative model is proposed thataccounts for the sub-normal magnetic moments in theseytterbocene-bipyridine complexes.

  7. Spin Isomers and Ligand Isomerization in a Three-Coordinate Cobalt(I) Carbonyl Complex.

    PubMed

    Al-Afyouni, Malik H; Suturina, Elizaveta; Pathak, Shubhrodeep; Atanasov, Mihail; Bill, Eckhard; DeRosha, Daniel E; Brennessel, William W; Neese, Frank; Holland, Patrick L

    2015-08-26

    Hemilabile ligands, which have one donor that can reversibly bind to a metal, are widely used in transition-metal catalysts to create open coordination sites. This change in coordination at the metal can also cause spin-state changes. Here, we explore a cobalt(I) system that is poised on the brink of hemilability and of a spin-state change and can rapidly interconvert between different spin states with different structures ("spin isomers"). The new cobalt(I) monocarbonyl complex L(tBu)Co(CO) (2) is a singlet ((1)2) in the solid state, with an unprecedented diketiminate binding mode where one of the C?C double bonds of an aromatic ring completes a pseudo-square-planar coordination. Dissolving the compound gives a substantial population of the triplet ((3)2), which has exceptionally large uniaxial zero-field splitting due to strong spin-orbit coupling with a low-lying excited state. The interconversion of the two spin isomers is rapid, even at low temperature, and temperature-dependent NMR and electronic absorption spectroscopy studies show the energy differences quantitatively. Spectroscopically validated computations corroborate the presence of a low minimum-energy crossing point (MECP) between the two potential energy surfaces and elucidate the detailed pathway through which the ?-diketiminate ligand "slips" between bidentate and arene-bound forms: rather than dissociation, the cobalt slides along the aromatic system in a pathway that balances strain energy and cobalt-ligand bonding. These results show that multiple spin states are easily accessible in this hemilabile system and map the thermodynamics and mechanism of the transition. PMID:26267848

  8. Cyclic Alkyl(amino) Carbene Stabilized Complexes with Low Coordinate Metals of Enduring Nature.

    PubMed

    Roy, Sudipta; Mondal, Kartik Chandra; Roesky, Herbert W

    2016-03-15

    N-Heterocyclic carbenes (NHCs) are known to stabilize some metal atoms in different oxidation states mostly by their strong 蟽-donation. After the successful syntheses of cyclic alkyl(amino) carbenes (cAACs), they have been proven to be much more effective in stabilizing electron rich species. In cAAC, one of the 蟽-withdrawing and 蟺-donating nitrogen atoms of NHC is replaced by a 蟽-donating quaternary carbon atom leading to a lower lying LUMO. This makes the acceptance of 蟺-back-donation from the element bound to the carbene carbon atom of cAAC energetically more advantageous. Further evidence suggests that the carbene carbon of cAAC can use the lone pair of electrons present on the adjacent nitrogen in a more controlled way depending on the accumulation of electron density on the bound metal. It has been found that cAAC can be utilized as excellent ligand for the stabilization of a complex with three coordinate metal center [(cAAC)2M(I)-Cl; M = Fe, Co, Cr]. Complex (cAAC)2M(II)Cl2 [M = Fe, Co, Cr] was prepared by reacting anhydrous M(II)Cl2 with two equiv of cAAC followed by treatment with one equiv of KC8 (reducing agent) to obtain (cAAC)2M(I)-Cl. The corresponding cation (cAAC)2M(+) was isolated when (cAAC)2M(I)-Cl was reacted with sodium-tetraarylborate (lithium) in toluene or fluorobenzene. The CV of cation (cAAC)2M(+) [M = Co, Fe] suggests that it can reversibly undergo one electron reduction. The cations of Co and Fe were reduced with Na(Hg) or KC8, respectively. (cAAC)2Co(I)Cl can be directly reduced to (cAAC)2Co(0) when reacted with one equiv of KC8. Analogous (cAAC路)2Zn(II) and (cAAC)2Mn complexes are prepared by reduction of (cAAC)MCl2 [M = Zn, Mn] with two equiv of KC8 in the presence of one equiv of cAAC. The square planar (cAAC)2NiCl2 complex was directly reduced by two equiv of LiN(iPr2) (KC8) to (cAAC)2Ni(0). The (cAAC)2Pd(0) and (cAAC)2Pt(0) complexes are prepared by substituting all four triphenylphosphines of (Ph3P)4M(0) [M = Pd, Pt] by two cAACs. Cation (cAAC)2M(+) [M = Cu, Au] was reduced with sodium/potassium to obtain the neutral analogue [(cAAC)2Cu, (cAAC)2Au]. Two coordinate Zn/Mn/Cu/Au are stabilized by two neutral carbene ligands possessing radical electrons on the carbene carbon atoms, while analogous complexes of Co/Fe/Ni/Pd/Pt contain metals in the zero oxidation state. The ground electronic structure of (cAAC)2M was thoroughly studied by theoretical calculations. In this Account, we summarize our developments in stabilizing metal complexes with low coordinate metal atoms in two, one, and most significantly in their zero oxidation states by utilizing cAACs as ligands. PMID:26925983

  9. 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

  10. 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鈥

  11. Syntheses and Characterization of Ruthenium(II) Tetrakis(pyridine)complexes: An Advanced Coordination Chemistry Experiment or Mini-Project

    ERIC Educational Resources Information Center

    Coe, Benjamin J.

    2004-01-01

    An experiment for third-year undergraduate a student is designed which provides synthetic experience and qualitative interpretation of the spectroscopic properties of the ruthenium complexes. It involves the syntheses and characterization of several coordination complexes of ruthenium, the element found directly beneath iron in the middle of the

  12. Syntheses and Characterization of Ruthenium(II) Tetrakis(pyridine)complexes: An Advanced Coordination Chemistry Experiment or Mini-Project

    ERIC Educational Resources Information Center

    Coe, Benjamin J.

    2004-01-01

    An experiment for third-year undergraduate a student is designed which provides synthetic experience and qualitative interpretation of the spectroscopic properties of the ruthenium complexes. It involves the syntheses and characterization of several coordination complexes of ruthenium, the element found directly beneath iron in the middle of the鈥

  13. [Complexity of social and healthcare coordination in addictions and the role of the nurse].

    PubMed

    Molina Fern醤dez, Antonio Jes鷖; Gonz醠ez Riera, Javier; Montero Bancalero, Francisco Jos; G髆ez-Salgado, Juan

    2016-01-01

    The present article discusses the psychosocial impact of basic and advanced concepts, such as social support and prevention, as well as to establish a link between theoretical models related to the social sphere on one side, and the health aspects on the other. This work is based on the context of the influence on health shared by community psychology and social psychology. Starting from the historical background of current approaches, a review is presented of those first actions focused on the care plan and they are framed in a reaction model to the drug problem, which progressed to the current healthcare network model, through the creation of Spanish National Action Plan on Drugs. The complexity of the problem is then broken down into the following key elements: Multifactorial Model of Drugs and Addictions, importance of prevention, and social support. Subsequently, a description is presented on the different levels of the healthcare network, with their different resources. This is also illustrated using a coordination protocol. Finally, it features the nursing approach to drugs, with its contributions, particularly as regards the coordination of resources, and aspects that must be developed for improvement in this area. PMID:26654277

  14. Catalytic alcohol oxidation by an unsymmetrical 5-coordinate copper complex: electronic structure and mechanism.

    PubMed

    Zueva, Ekaterina; Walton, Paul H; McGrady, John E

    2006-01-01

    Density functional theory reveals the detailed mechanism of alcohol oxidation by a model copper complex, Cu(II)L, L = cis-1-(3',5'-dimethoxy-benzylideneamino)-3,5-[2-hydroxy-(3',5'-di-tert-butyl)benzylideneimino]cyclohexane. Despite the obvious structural and functional parallels between the title compound and the enzyme galactose oxidase, the details of the catalytic pathway are fundamentally different. In the enzyme, coordination of the substrate produces an active form containing a Cu(II) centre and a tyrosyl radical, the latter being responsible for the abstraction of hydrogen from the substrate. In the model system, in marked contrast, the active form contains a Cu(II) centre, but the ligand radical character is localised on the substrate (alcoholate) oxygen, rather than the phenolate ligand. The result is a significantly higher barrier to hydrogen-atom abstraction compared to the enzyme itself. The origin of these significant differences is traced to the rigid nature of the pentadentate ligand, which resists changes in coordination number during the catalytic cycle. PMID:16357972

  15. Insights into copper coordination in the EcoRI朌NA 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 EcoRI朌NA(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

  16. Iron(III) coordination induced novel 18-metallacrown-6 complex: esterification and isolation of the ligand.

    PubMed

    Jin, Longfei; Yu, Hui; Wu, Shuxiang; Xiao, Fengping

    2009-01-01

    The trianionic heptadentate ligand, (Z)-3-(salicylhydrazinocarbonyl) propenoic acid ((Z)-H(4)shcpa) (1), has been synthesized in good yield and reacted with FeCl(3).6H(2)O, to produce the complex [Fe(III)(6) (C(12)H(9)N(2)O(5))(6)(H(2)O)(2)(CH(3)OH)(4)] x 6CH(3)OH (2). The complex has been characterized by single-crystal X-ray diffraction. In the self-assembly process the ligand was esterified and transferred into (Z)-methyl 3-(salicylhydrazinocarbonyl) propenoate ((Z)-H(3)mshcp) (3). In the structure, the neutral Fe(III) complex contains a 18-membered metallacrown ring consisting of six Fe(III) and six trianionic ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Fe(III)-N-N]. Due to the meridional coordination of the ligands to the Fe(3+) ions, the ligands enforce the stereochemistry of the Fe(3+) ions as a propeller configuration with alternating Lambda/Delta form. The metallacrown can be treated with SnCl(2) to obtain purified ester. In addition, we have also obtained reduced esterified ligand, methyl 3-(salicylhydrazinocarbonyl) propanoate (H3mshcp) (4) with another reductant Zn powder. PMID:19081989

  17. Neutral, seven-coordinate dioxime complexes of technetium(III): Synthesis and characterization

    SciTech Connect

    Linder, K.E.; Malley, M.F.; Gougoutas, J.Z.; Unger, S.E.; Nunn, A.D. )

    1990-06-27

    The tin-capped complexes {sup 99}Tc(oxime){sub 3}({mu}-OH)SnCl{sub 3} (oxime = dimethylglyoxime (DMG) or cyclohexanedione dioxime (CDO)) can be prepared by the reduction of NH{sub 4}TcO{sub 4} with 2 equiv of SnCl{sub 2} in the presence of dioxime and HCl. These tin-capped complexes can be readily converted into a new class of uncapped Tc-dioxime compounds, TcCl(oxime){sub 3}, by treatment with HCl. This reaction is reversible. Both the tin-capped and uncapped tris(dioxime) complexes can be converted to the previously reported boron-capped Tc-dioxime complexes TcCl(oxime){sub 3}BR (R = alkyl, OH) by reaction with boronic acids or with boric acid at low pH. All of these complexes (Tc(oxime){sub 3}({mu}-OH)SnCl{sub 3}, TcCl(oxime){sub 3}, and TcCl(oxime){sub 3}BR) appear to be neutral, seven-coordinate compounds of technetium(III). They have been characterized by elemental analysis, {sup 1}H NMR and UV/visible spectroscopy, conductivity, and fast atom bombardment mass spectrometry. The synthesis, characterization, and reactivity of these compounds is discussed. The x-ray crystal structure analysis of TcCl(DMG){sub 3} and an abbreviated structure report on TcCl(DMG){sub 3}MeB are described. Crystal data for TcCl(DMG){sub 3} are reported. 23 refs., 6 figs., 5 tabs.

  18. 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.

  19. 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

  20. A Molecular Artisans Guide to Supramolecular Coordination Complexes and Metal Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Wu, Xialu; Young, David J.; Hor, T. S. Andy

    2015-10-01

    As molecular synthesis advances, we are beginning to learn control of not only the chemical reactivity (and function) of molecules, but also of their interactions with other molecules. It is this basic idea that has led to the current explosion of supramolecular science and engineering. Parallel to this development, chemists have been actively pursuing the design of very large molecules using basic molecular building blocks. Herein, we review the general development of supramolecular chemistry and particularly of two new branches: supramolecular coordination complexes (SCCs) and metal organic frameworks (MOFs). These two fields are discussed in detail with typical examples to illustrate what is now possible and what challenges lie ahead for tomorrow's molecular artisans.

  1. Geometric and electronic structures of five-coordinate manganese(ii) "picket fence" porphyrin complexes.

    PubMed

    Yu, Qiang; Liu, Yanhong; Liu, Diansheng; Li, Jianfeng

    2015-05-28

    Three five-coordinate, high spin manganese(ii) "picket fence" porphyrin complexes, [Mn(TpivPP)(L)] (TpivPP = 伪,伪,伪,伪-tetrakis(o-pivalamidophenyl)porphyrinato; L = 1-MeIm (1-methylimidazole), 1-EtIm (1-ethylimidazole) and 2-MeHIm (2-methylimidazole)), are synthesized and studied by single-crystal X-ray, UV-vis and electronic paramagnetic resonance (EPR) spectroscopy. Structural parameters are investigated and compared with analogues. Low temperature (90 K), high field EPR studies of [Mn(TpivPP)(1-MeIm)] and [Mn(TpivPP)(2-MeHIm)] showed five resonances including characteristic signals at 鈭5.9 and 鈭2.0. The simulations of the EPR spectra give the zero field splitting (zfs) parameters (D, E and 位) and the hyperfine coupling constant (A). PMID:25913615

  2. 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.

  3. Photochemical reduction of uranyl nitrate

    SciTech Connect

    Duerksen, W.K.

    1993-10-20

    The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

  4. 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 癈. PMID:21879074

  5. An unusually flexible expanded hexaamine cage and its Cu(II) complexes: variable coordination modes and incomplete encapsulation.

    PubMed

    Qin, Chang-Jin; James, Lloyd; Chartres, Jy D; Alcock, Leighton J; Davis, Kimberley J; Willis, Anthony C; Sargeson, Alan M; Bernhardt, Paul V; Ralph, Stephen F

    2011-09-19

    The bicyclic hexaamine "cage" ligand Me(8)tricosaneN(6) (1,5,5,9,13,13,20,20-octamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane) is capable of encapsulating octahedral metal ions, yet its expanded cavity allows the complexed metal to adopt a variety of geometries comprising either hexadentate or pentadentate coordination of the ligand. When complexed to Cu(II) the lability of the metal results in a dynamic equilibrium in solution between hexadentate- and pentadentate-coordinated complexes of Me(8)tricosaneN(6). Both [Cu(Me(8)tricosaneN(6))](ClO(4))(2) (6-coordinate) and [Cu(Me(8)tricosaneN(6))](S(2)O(6)) (5-coordinate) have been characterized structurally. In weak acid (pH 1) a singly protonated complex [Cu(HMe(8)tricosaneN(6))](3+) has been isolated that finds the ligand binding as a pentadentate with the uncoordinated amine being protonated. vis-NIR and electron paramagnetic resonance (EPR) spectroscopy show that the predominant solution structure of [Cu(Me(8)tricosaneN(6))](2+) at neutral pH comprises a five-coordinate, square pyramidal complex. Cyclic voltammetry of the square pyramidal [Cu(Me(8)tricosaneN(6))](2+) complex reveals a reversible Cu(II/I) couple. All of these structural, spectroscopic, and electrochemical features contrast with the smaller cavity and well studied "sarcophagine" (sar, 3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) Cu(II) complexes which are invariably hexadentate coordinated in neutral solution and cannot stabilize a Cu(I) form. PMID:21806034

  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. Observation of Radiolytic Field Alteration of the Uranyl Cation in Bicarbonate Solution

    SciTech Connect

    Snow, Lanee A.; McNamara, Bruce K.; Sinkov, Sergey I.; Cho, Herman M.; Friese, Judah I.

    2006-12-01

    In previous work we demonstrated that radiolysis of uranyl tris carbonate in near neutral pH to alkaline carbonate solutions, could be followed by 13C NMR. Radiolysis of the complex produced novel uranyl peroxo carbonate solution state species, whose structures depended on the pH and radiolytic dose rate. In this work, we investigate speciation of the uranyl carbonate trimer which is predominant in bicarbonate solution near pH 5.9. We observe radiolytically derived speciation to different mixed peroxy carbonate species than seen in the higher pH solutions. Auto radiolysis of uranium (VI) carbonate solutions between pH 5.9 and 7.2 is shown to alter the uranium speciation over relatively short periods of time and was followed by 13C NMR and visible spectrophotometry, using dissolved 233(UO2)3(CO3)6 6- both as the radiolysis source (D= 14.9 Gy/hr) and as a trap for the newly formed hydrogen peroxide. Direct addition of hydrogen peroxide to solutions of the uranyl-carbonate trimer is shown to reproduce the 13 C NMR signatures of the complexe(s) formed by radiolysis, but additionally a variety of new complexes are revealed. Ratios of H2O2/trimer < 1.5 produced a uranyl peroxo carbonate adduct, that is shown to be common to the radiolytically produced species. Ratios of H2O2/ trimer >1 resulted in formation of stable higher order peroxo carbonate complexes. The 13C NMR signatures and visible spectra of these complexes are described here. Rigorous characterization of the species is an ongoing effort.

  8. The CCAAT-binding complex coordinates the oxidative stress response in eukaryotes

    PubMed Central

    Th枚n, Marcel; Al Abdallah, Qusai; Hortschansky, Peter; Scharf, Daniel H.; Eisendle, Martin; Haas, Hubertus; Brakhage, Axel A.

    2010-01-01

    The heterotrimeric CCAAT-binding complex is evolutionary conserved in eukaryotic organisms. The corresponding Aspergillus nidulans CCAAT- binding factor (AnCF) consists of the subunits HapB, HapC and HapE. All of the three subunits are necessary for DNA binding. Here, we demonstrate that AnCF senses the redox status of the cell via oxidative modification of thiol groups within the histone fold motif of HapC. Mutational and in vitro interaction analyses revealed that two of these cysteine residues are indispensable for stable HapC/HapE subcomplex formation and high-affinity DNA binding of AnCF. Oxidized HapC is unable to participate in AnCF assembly and localizes in the cytoplasm, but can be recycled by the thioredoxin system in vitro and in vivo. Furthermore, deletion of the hapC gene led to an impaired oxidative stress response. Therefore, the central transcription factor AnCF is regulated at the post-transcriptional level by the redox status of the cell serving for a coordinated activation and deactivation of antioxidative defense mechanisms including the specific transcriptional activator NapA, production of enzymes such as catalase, thioredoxin or peroxiredoxin, and maintenance of a distinct glutathione homeostasis. The underlying fine-tuned mechanism very likely represents a general feature of the CCAAT-binding complexes in eukaryotes. PMID:19965775

  9. 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.

  10. A Porphyrin Coordination Cage Assembled from Four Silver(I) Triazolyl-Pyridine Complexes.

    PubMed

    Ballester, Pablo; Claudel, Micka雔; Durot, St閜hanie; Kocher, Lucas; Schoepff, Laetitia; Heitz, Val閞ie

    2015-10-19

    The synthesis of a zinc(II) porphyrin 1 with four appended triazolyl-pyridine chelates is reported. Complexation of the porphyrin peripheral ligands with Ag(I) ions in a 1:2 binding stoichiometry afforded quantitatively the coordination cage [Ag4 (1)2 ](4+) . The assembly and disassembly processes of the cage were investigated in solution using UV/Vis spectroscopy. The mathematical analysis of the data obtained in the UV/Vis titration of 1 with Ag(I) confirmed the assembly in CH2 Cl2 /MeOH (90:10) solution of a species having a 1:2 porphyrin/silver stoichiometry and assigned to it an overall stability constant of 5.010(26) ?M(-5) . The use of a model system allowed an independent assessment of a microscopic binding constant value (Km ) for the interaction between the triazolyl-pyridine ligand and Ag(I) . The coincidence that existed between the Km values extracted from the model system and the titration of 1 provided an indication of the quality and fit of the data analysis. It also allowed the calculation of the average effective molarity (EM) value for the three intramolecular processes that led to the cage assembly as 2.6?mM. Simulated speciation profiles supported the conclusion that at millimolar concentration and working under strict stoichiometric control of the silver/porphyrin ratio, the cage [Ag4 (1)2 ](4+) was the species exclusively assembled in solution. On the other hand, when the concentration of added Ag(I) was approximately 2.6?mM, 50?% of the coordination cage disassembled into open aggregates. PMID:26338089

  11. Six-coordinate nitrosyl and nitro complexes of meso-tetratolylporphyrinatocobalt with trans sulfur-donor ligands.

    PubMed

    Kurtikyan, Tigran S; Gulyan, Gurgen M; Dalaloyan, Arina M; Kidd, Bryce E; Goodwin, John A

    2010-09-01

    By Fourier transform infrared and optical spectroscopy, it has been observed that interactions of dimethyl sulfide and tetrahydrothiophene with nitrosyl and nitro complexes of meso-tetra-p-tolylporphyrinatocobalt [Co(TTP)] lead to the formation of previously unknown six-coordinate species. Nitrosyl complexes of the general formula (S-donor)Co(TTP)(NO) are thermally unstable and can be seen only at low temperatures both in the solid state and in solution. The nitro complexes (S-donor)Co(TTP)(NO(2)) are fairly stable at room temperature in the solid state but partly decompose upon dissolution. The binding constants for these complexation reactions were determined. In contrast to the solid-state iron nitritoporphyrin complexes, oxo-transfer reactions from the coordinated nitro group of Co(TTP)(NO(2)) to the S donors, resulting in oxidation of these sulfides and the formation of Co(TTP)(NO), were not observed. PMID:20681627

  12. Elucidation of selectivity for uranyl ions with an ICT organosilane-modified fluorescent receptor.

    PubMed

    Karag鰖, Fehmi; G黱ey, Orhan

    2014-05-01

    A fluorescent receptor, isocyanatopropyl trimethoxysilane grafted 9-amino acridine (AcI), was synthesized and characterized by elemental analysis, FTIR and NMR spectroscopy. Photophysical properties and pH-dependent fluorescence behavior of AcI were investigated and its complex stoichiometry with uranyl ion was elucidated. Change in fluorescence emission of AcI with pH of the solution was observed and pKa value was determined by using integrated emission intensity versus pH. It was found that AcI exhibited fluorescence enhancement, which can be attributed to an internal charge transfer (ICT) mechanism, upon titration with uranyl ions in mixture of ethanol-buffer solution while the fluorescence emission of AcI was not affected by addition of other divalent transition metal ions except mercury (II) ions. On the other hand, the both fluorescence and UV-vis titration measurements revealed unique selectivity for uranyl ions over the interfering mercury (II) ions. The spectrofluorometric titration clarified that uranyl interacted with AcI to form AcI 2(UO2(2 +))3 (2:3) complex structure with an apparent association constant of K = 7.41 10(6) M(-2/3). The interference effect of some cations on fluorescence enhancement exhibited by complex was also tested. PMID:24407892

  13. Self-assembly of three new coordination complexes: Formation of 2-D square grid, 1-D chain and tape structures

    NASA Astrophysics Data System (ADS)

    Indrani, Murugan; Ramasubramanian, Ramasamy; Fronczek, Frank R.; Vasanthacharya, N. Y.; Kumaresan, Sudalaiandi

    2009-08-01

    Three distinct coordination complexes, viz., [Co(imi) 2(tmb) 2] ( 1) [where imi = imidazole], {[Ni(tmb) 2(H 2O) 3]2H 2O} n ( 2) and [Cu 2(?-tmb) 4(CH 3OH) 2] ( 3), have been synthesized hydrothermally by the reactions of metal acetates, 2,4,6-trimethylbenzoic acid (Htmb) and with or without appropriate amine. The Ni analogue of 1 and the Co analogue of 2 have also been synthesized. X-ray single-crystal diffraction suggests that complex 1 represents discrete mononuclear species and complex 2 represents a 1D chain coordination polymer in which the Ni(II) ions are connected by the bridging water molecules. Complex 3 represents a neutral dinuclear complex. In 1, the central metal ions are associated by the carboxylate moiety and imidazole ligands, whereas the central metal atom is coordinated to the carboxylate moiety and the respective solvent molecules in 2 and 3. In 3, the four 2,4,6-trimethylbenzoate moieties act as a bridge connecting two copper (II) ions and the O atoms of methanol coordinate in an anti arrangement to form a square pyramidal geometry, with the methanol molecule at the apical position. In all the three structures the central metal atom sits on a crystallographic inversion centre. In all the cases, the coordination entities are further organized via hydrogen bonding interactions to generate multifarious supramolecular networks. Complexes 1, 2 and 3 have also been characterized by spectroscopic (UV/Vis and IR) and thermal analysis (TGA). In addition, the complexes were found to exhibit antimicrobial activity.The magnetic susceptibility measurements, measured from 8 to 300 K, revealed antiferromagnetic interactions between the Co(II) ions in compound 1 and the Ni(II) ions in 1a, respectively.

  14. First-row transition metal complexes of ENENES ligands: the ability of the thioether donor to impact the coordination chemistry.

    PubMed

    Dub, Pavel A; Scott, Brian L; Gordon, John C

    2016-01-19

    The reactions of two variants of ENENES ligands, E(CH2)2NH(CH)2SR, where E = 4-morpholinyl, R = Ph (), Bn () with MCl2 (M = Mn, Fe, Co, Ni and Cu) in coordinating solvents (MeCN, EtOH) affords isolable complexes, whose magnetic susceptibility measurements suggest paramagnetism and a high-spin formulation. X-Ray diffraction studies of available crystals show that the ligand coordinates to the metal in either a bidentate ?(2)[N,N'] or tridentate ?(3)[N,N',S] fashion, depending on the nature of ligand and/or identity of the metal atom. In the case of a less basic SPh moiety, a bidentate coordination mode was identified for harder metals (Mn, Fe), whereas a tridentate coordination mode was identified in the case of a more basic SBn moiety with softer metals (Ni, Cu). In the intermediate case of Co, ligands and coordinate via ?(2)[N,N'] and ?(3)[N,N',S] coordination modes, which can be conveniently predicted by DFT calculations. For the softest metal (Cu), ligand coordinates in a ?(3)[N,N',S] fashion. PMID:26688119

  15. XPS spectra of uranyl minerals and synthetic uranyl compounds. I: The U 4f spectrum

    NASA Astrophysics Data System (ADS)

    Schindler, M.; Hawthorne, F. C.; Freund, M. S.; Burns, P. C.

    2009-05-01

    The occurrence and binding energies of the U 6+, U 5+ and U 4+ bands in the U 4f 7/2 peak of 19 uranyl minerals of different composition and structure were measured by XPS. The results suggest that these minerals can be divided into the following four groups: (1) Uranyl-hydroxy-hydrate compounds with no or monovalent interstitial cations; (2) Uranyl-hydroxy-hydrate minerals with divalent interstitial cations; (3) Uranyl-oxysalt minerals with ( TO n) groups ( T = Si, P, and C) in which all equatorial O-atoms of the uranyl-polyhedra are shared with ( TO n) groups; (4) Uranyl-oxysalt minerals with ( TO n) groups ( T = S and Se), in which some equatorial O-atoms are shared only between uranyl polyhedra. The average binding energies of the U 6+and U 4+ bands shift to lower values with (1) incorporation of divalent cations and (2) increase in the Lewis basicity of the anion group bonded to U. The first observation is a consequence of an increase in the bond-valence transfer from the interstitial species (cations, H 2O) groups to the O-atoms of the uranyl-groups, which results in an electron transfer from O to U 6+. The second trend correlates with an increase in the covalency of the U sbnd O bonds with increase in Lewis basicity of the anion group, which results in a shift of the electron density from O to U. The presence of U 4+ on the surface of uranyl minerals can be detected by the shape of the U 4f 7/2 peak, and the occurrence of the U 5f peak and satellite peaks belonging to the U 4f 5/2 peak. The presence of U 4+ in some of the uranyl minerals and synthetics examined may be related to the conditions during their formation. A charge-balance mechanism is proposed for the incorporation of lower-valence U in the structure of uranyl minerals. Exposure of a Na-substituted metaschoepite crystal in air and to Ultra-High Vacuum results in dehydration of its surface structure associated with a shift of the U 6+ bands to higher binding energies. The latter observation indicates a shift in electron density from U to O, which must be related to structural changes inside the upper surface layers of Na-substituted metaschoepite.

  16. Neodymium uranyl peroxide synthesis by ion exchange on ammonium uranyl peroxide nanoclusters.

    PubMed

    Blanchard, F; Ellart, M; Rivenet, M; Vigier, N; Hablot, I; Morel, B; Grandjean, S; Abraham, F

    2016-03-11

    This study demonstrates the ability of ammonium uranyl peroxide nanoclusters U32R-NH4 to undergo exchange in between NH4(+) and trivalent (Nd(3+)) or tetravalent (Th(4+)) cations in the solid state. It paves the way for new promising routes for the synthesis of mixed uranyl peroxides. The exchange ability may also be considered for solution decontamination and synthesis of new mixed actinide-oxide precursors. Both of these applications could be used in the nuclear industry. PMID:26879486

  17. Theoretical study of the Pb(II)-catechol system in dilute aqueous solution: Complex structure and metal coordination sphere determination

    NASA Astrophysics Data System (ADS)

    Lapouge, Christine; Cornard, Jean-Paul

    2010-04-01

    We investigated the unknown interaction of Pb(II) with catechol ligand in diluted aqueous solution by electronic spectroscopies combined with quantum chemical calculations. The aim of this work is the determination of the complete structure of the complex formed and particularly the metal coordination sphere. Three successive steps have been necessary to reach this goal: (i) the comparison of the experimental electronic absorption spectrum with theoretical spectra calculated from various hypothetical structures, (ii) complexation reaction pathways calculations in vacuum and with taking into account the solvent effects and finally (iii) the fluorescence emission wavelength calculations. All these investigations led to identify a monodentate complex with the monodeprotonated ligand, in which the Pb atom presents a coordination number of five. The formula of the complex is [Pb(Hcat)(HO)4]mono+.

  18. Multicell Coordinated Beamforming With Rate Outage Constraint桺art I: Complexity Analysis

    NASA Astrophysics Data System (ADS)

    Li, Wei-Chiang; Chang, Tsung-Hui; Chi, Chong-Yung

    2015-06-01

    This paper studies the coordinated beamforming (CoBF) design in the multiple-input single-output interference channel, assuming only channel distribution information given a priori at the transmitters. The CoBF design is formulated as an optimization problem that maximizes a predefined system utility, e.g., the weighted sum rate or the weighted max-min-fairness (MMF) rate, subject to constraints on the individual probability of rate outage and power budget. While the problem is non-convex and appears difficult to handle due to the intricate outage probability constraints, so far it is still unknown if this outage constrained problem is computationally tractable. To answer this, we conduct computational complexity analysis of the outage constrained CoBF problem. Specifically, we show that the outage constrained CoBF problem with the weighted sum rate utility is intrinsically difficult, i.e., NP-hard. Moreover, the outage constrained CoBF problem with the weighted MMF rate utility is also NP-hard except the case when all the transmitters are equipped with single antenna. The presented analysis results confirm that efficient approximation methods are indispensable to the outage constrained CoBF problem.

  19. The MAP kinase pathway coordinates crossover designation with disassembly of synaptonemal complex proteins during meiosis

    PubMed Central

    Nadarajan, Saravanapriah; Mohideen, Firaz; Tzur, Yonatan B; Ferrandiz, Nuria; Crawley, Oliver; Montoya, Alex; Faull, Peter; Snijders, Ambrosius P; Cutillas, Pedro R; Jambhekar, Ashwini; Blower, Michael D; Martinez-Perez, Enrique; Harper, J Wade; Colaiacovo, Monica P

    2016-01-01

    Asymmetric disassembly of the synaptonemal complex (SC) is crucial for proper meiotic chromosome segregation. However, the signaling mechanisms that directly regulate this process are poorly understood. Here we show that the mammalian Rho GEF homolog, ECT-2, functions through the conserved RAS/ERK MAP kinase signaling pathway in the C. elegans germline to regulate the disassembly of SC proteins. We find that SYP-2, a SC central region component, is a potential target for MPK-1-mediated phosphorylation and that constitutively phosphorylated SYP-2 impairs the disassembly of SC proteins from chromosomal domains referred to as the long arms of the bivalents. Inactivation of MAP kinase at late pachytene is critical for timely disassembly of the SC proteins from the long arms, and is dependent on the crossover (CO) promoting factors ZHP-3/RNF212/Zip3 and COSA-1/CNTD1. We propose that the conserved MAP kinase pathway coordinates CO designation with the disassembly of SC proteins to ensure accurate chromosome segregation. DOI: http://dx.doi.org/10.7554/eLife.12039.001 PMID:26920220

  20. Broken dynamical symmetry condition to control a chemical reaction by the complex coordinate ( t, t') method

    NASA Astrophysics Data System (ADS)

    Alon, Ofir E.; Moiseyev, Nimrod

    1995-07-01

    Using the ( t, t') formalism [J. Chem. Phys. 99 (1993) 4590] combined with the complex coordinate method, exact (i.e. not perturbative) condition for control of a model chemical reaction is derived regardless of the field intensity and whether the electromagnetic field is time-periodic or not. We prove that upon breaking the dynamical symmetry H( p, x, t) = H(- p, - x, + T/2), the dissociation channel of the A + BA ? ABA ? AB + A reaction can be controlled. It is shown that when the molecular/field interaction is given by p?zf(t) , where f( t) represents the electromagnetic field, the dissociation channel of the A + BC ? ABC ? AB + C reaction can be controlled by breaking the dynamical symmetry property, f( t) = - f( t + T/2). For time-periodic fields T is the time period (i.e. one optical cycle) where for pulsed lasers it is the duration of the pulse. Numerical examples are given for symmetric and asymmetric model Hamiltonians subjected to two cw lasers. These numerical examples illustrate the role of the phase difference between the cw lasers, regardless of the laser intensity, in the coherent control procedure which was first proposed by Brumer and Shapiro [Chem. Phys. Letters 126 (1986) 54].

  1. The MAP kinase pathway coordinates crossover designation with disassembly of synaptonemal complex proteins during meiosis.

    PubMed

    Nadarajan, Saravanapriah; Mohideen, Firaz; Tzur, Yonatan B; Ferrandiz, Nuria; Crawley, Oliver; Montoya, Alex; Faull, Peter; Snijders, Ambrosius P; Cutillas, Pedro R; Jambhekar, Ashwini; Blower, Michael D; Martinez-Perez, Enrique; Harper, J Wade; Colaiacovo, Monica P

    2016-01-01

    Asymmetric disassembly of the synaptonemal complex (SC) is crucial for proper meiotic chromosome segregation. However, the signaling mechanisms that directly regulate this process are poorly understood. Here we show that the mammalian Rho GEF homolog, ECT-2, functions through the conserved RAS/ERK MAP kinase signaling pathway in the C. elegans germline to regulate the disassembly of SC proteins. We find that SYP-2, a SC central region component, is a potential target for MPK-1-mediated phosphorylation and that constitutively phosphorylated SYP-2 impairs the disassembly of SC proteins from chromosomal domains referred to as the long arms of the bivalents. Inactivation of MAP kinase at late pachytene is critical for timely disassembly of the SC proteins from the long arms, and is dependent on the crossover (CO) promoting factors ZHP-3/RNF212/Zip3 and COSA-1/CNTD1. We propose that the conserved MAP kinase pathway coordinates CO designation with the disassembly of SC proteins to ensure accurate chromosome segregation. PMID:26920220

  2. 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.

  3. Homoleptic Two-Coordinate Silylamido Complexes of Chromium(I), Manganese(I), and Cobalt(I).

    PubMed

    Werncke, C Gunnar; Suturina, Elizaveta; Bunting, Philip C; Vendier, Laure; Long, Jeffrey R; Atanasov, Mihail; Neese, Frank; Sabo-Etienne, Sylviane; Bontemps, S閎astien

    2016-01-01

    Anionic two-coordinate complexes of first-row transition-metal(I) centres are rare molecules that are expected to reveal new magnetic properties and reactivity. Recently, we demonstrated that a N(SiMe3 )2 (-) ligand set, which is unable to prevent dimerisation or extraneous ligand coordination at the +2 oxidation state of iron, was nonetheless able to stabilise anionic two-coordinate Fe(I) complexes even in the presence of a Lewis base. We now report analogous Cr(I) and Co(I) complexes with exclusively this amido ligand and the isolation of a [Mn(I) {N(SiMe3 )2 }2 ]2 (2-) dimer that features a Mn-Mn bond. Additionally, by increasing the steric hindrance of the ligand set, the two-coordinate complex [Mn(I) {N(Dipp)(SiMe3 )}2 ](-) was isolated (Dipp=2,6-iPr2 -C6 H3 ). Characterisation of these compounds by using X-ray crystallography, NMR spectroscopy, and magnetic susceptibility measurements is provided along with ligand-field analysis based on CASSCF/NEVPT2 ab initio calculations. PMID:26682930

  4. 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)

  5. Identification of Copper(II) Complexes in Aqueous Solution by Electron Spin Resonance: An Undergraduate Coordination Chemistry Experiment.

    ERIC Educational Resources Information Center

    Micera, G.; And Others

    1984-01-01

    Background, procedures, and results are provided for an experiment which examines, through electron spin resonance spectroscopy, complex species formed by cupric and 2,6-dihydroxybenzoate ions in aqueous solutions. The experiment is illustrative of several aspects of inorganic and coordination chemistry, including the identification of species

  6. Structural diversity in mercury(II) coordination complexes with asymmetrical hydrazone-based ligands derived from pyridine

    NASA Astrophysics Data System (ADS)

    Masoumi, Asad; Servati Gargari, Masoumeh; Mahmoudi, Ghodrat; Miroslaw, Barbara; Therrien, Bruno; Abedi, Marjan; Hazendonk, Paul

    2015-05-01

    Three novel Hg(II) complexes 1-3 of asymmetrical hydrazone-pyridine based ligands, L1-L3, with distinct coordination structures have been prepared and characterized by a single crystal X-ray diffraction, elemental and thermal analysis, and IR spectroscopy. The complexes form either discrete units with one (1) or two (2) organic ligands, or one-dimensional polymers (3). Hence the ligands can be regarded as chelating (1), mono-dentate (2) or bridging (3) agents. The mercury center is essentially neutralized in each complex by two iodide anions. The coordination in complexes 2 and 3 adopts deformed tetrahedral shapes. In contrast the Hg(II) cation in complex 1 binds three coplanar ligating atoms (O,N,N) and, as with pincer ligands, its coordination polyhedron is supplemented with two I- anions in apical positions. The structural diversity in these complexes is strongly influenced by the position of N atom in pyridine derived moieties. The crystal structure is stabilized by N/O-H⋯N/O/I hydrogen bonds and ?⋯? interactions.

  7. Revealing and tuning the core, structure, properties and function of polymer micelles with lanthanide-coordination complexes.

    PubMed

    Wang, Junyou; Groeneveld, Andrea; Oikonomou, Maria; Prusova, Alena; Van As, Henk; van Lent, Jan W M; Velders, Aldrik H

    2015-12-16

    Controlling self-assembly processes is of great interest in various fields where multifunctional and tunable materials are designed. We here present the versatility of lanthanide-complex-based micelles (Ln-C3Ms) with tunable coordination structures and corresponding functions (e.g. luminescence and magnetic relaxation enhancement). Micelles are prepared by charge-driven self-assembly of a polycationic-neutral diblock copolymer and anionic coordination complexes formed by Ln(iii) ions and the bis-ligand L2EO4, which contains two dipicolinic acid (DPA) ligand groups (L) connected by a tetra-ethylene oxide spacer (EO4). By varying the DPA/Ln ratio, micelles are obtained with similar size but with different stability, different aggregation numbers and different oligomeric and polymeric lanthanide(iii) coordination structures in the core. Electron microscopy, light scattering, luminescence spectroscopy and magnetic resonance relaxation experiments provide an unprecedented detailed insight into the core structures of such micelles. Concomitantly, the self-assembly is controlled such that tunable luminescence or magnetic relaxation with Eu-C3Ms, respectively, Gd-C3Ms is achieved, showing potential for applications, e.g. as contrast agents in (pre)clinical imaging. Considering the various lanthanide(iii) ions have unique electron configurations with specific physical chemical properties, yet very similar coordination chemistry, the generality of the current coordination-structure based micellar design shows great promise for development of new materials such as, e.g., hypermodal agents. PMID:26444312

  8. 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.

  9. 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, J黵gen; 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

  10. Synthesis, crystal structure and spectroscopic properties of a supramolecular zinc(II) complex with N2O2 coordination sphere.

    PubMed

    Dong, Wen-Kui; Zhang, Li-Sha; Sun, Yin-Xia; Zhao, Meng-Meng; Li, Gang; Dong, Xiu-Yan

    2014-01-01

    A new hexa-coordinated zinc(II) complex, namely [ZnL(H2O)2]n, with N2O2 coordination sphere (H2L=4,4'-dibromo-6,6'-dichloro-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and structurally characterized by elemental analyses, IR, UV-vis spectra and TG-DTA analyses, etc. Crystallographic data are monoclinic, space group P2(1)/c, a=24.634(2)脜, b=10.144(1)脜, c=7.9351(6)脜, 尾=91.371(2)掳, V=1982.4(3)脜(3), Dc=2.099 g/cm(3), Z=4. The zinc(II) complex exhibits a slightly distorted octahedral geometry with halogen-substituted Salen-type bisoxime forming the basal N2O2 coordination sphere and two oxygen atoms from two coordinated water molecules in the axial position. The hydrogen-bonding and 蟺-蟺 stacking interactions have stabilized the zinc(II) complex molecules to form a self-assembling infinite dual metal-water chain-like structure with the nearest Zn鈰痁n distance of 4.954(4)脜. PMID:24263129

  11. Oxa1-ribosome complexes coordinate the assembly of cytochrome C oxidase in mitochondria.

    PubMed

    Keil, Melanie; Bareth, Bettina; Woellhaf, Michael W; Peleh, Valentina; Prestele, Martin; Rehling, Peter; Herrmann, Johannes M

    2012-10-01

    The terminal enzyme of the respiratory chain, cytochrome c oxidase, consists of a hydrophobic reaction center formed by three mitochondrially encoded subunits with which 9-10 nuclear encoded subunits are associated. The three core subunits are synthesized on mitochondrial ribosomes and inserted into the inner membrane in a co-translational reaction facilitated by the Oxa1 insertase. Oxa1 consists of an N-terminal insertase domain and a C-terminal ribosome-binding region. Mutants lacking the C-terminal region show specific defects in co-translational insertion, suggesting that the close contact of the ribosome with the insertase promotes co-translational insertion of nascent chains. In this study, we inserted flexible linkers of 100 or 200 amino acid residues between the insertase domain and ribosome-binding region of Oxa1 of Saccharomyces cerevisiae. In the absence of the ribosome receptor Mba1, these linkers caused a length-dependent decrease in mitochondrial respiratory activity caused by diminished levels of cytochrome c oxidase. Interestingly, considerable amounts of mitochondrial translation products were still integrated into the inner membrane in these linker mutants. However, they showed severe defects in later stages of the biogenesis process, presumably during assembly into functional complexes. Our observations suggest that the close proximity of Oxa1 to ribosomes is not only used to improve membrane insertion but is also critical for the productive assembly of the subunits of the cytochrome c oxidase. This points to a role for Oxa1 in the spatial coordination of the ribosome with assembly factors that are critical for enzyme biogenesis. PMID:22904327

  12. Trinuclear complexes and coordination polymers of redox-active guanidino-functionalized aromatic (GFA) compounds with a triphenylene core.

    PubMed

    Lebk點her, Anna; Wagner, Christoph; H黚ner, Olaf; Kaifer, Elisabeth; Himmel, Hans-J鰎g

    2014-09-15

    Herein, we report on the synthesis, redox activity, and coordination chemistry of 2,3,6,7,10,11-hexakis(tetramethylguanidino)triphenylene. CV measurements indicated that the new compound could be oxidized in three separate reversible two-electron oxidation events. The HOMO and LUMO energies were estimated from the oxidation wave and the onset of absorption in the UV/vis spectrum. Our discussion also includes the related new compound 2,3,6,7,10,11-hexakis(N,N'-dimethylethyleneguanidino)triphenylene. Then trinuclear Cu(I) and Cu(II) complexes of the new triphenylene ligands were characterized, and their electronic properties are discussed. In contrast to previously studied redox-active GFA ligands, oxidation of trinuclear copper(I) iodide complexes with I2 leads to copper instead of ligand oxidation. In the tetra-coordinated Cu(II) complexes, the coordination mode is intermediate between tetrahedral and square planar. The optical properties of the complexes were studied, and low-energy electronic transitions were assigned to ligand-to-metal charge-transfer (LMCT) excitations. We then extended our analysis to trinuclear Ni(II) and Co(II) complexes. The magnetic coupling mediated through the triphenylene ligand in the trinuclear Cu(II) and Co(II) complexes was studied by SQUID magnetometry, revealing ferromagnetic coupling of the spin centers and different degrees of spin delocalization into the guanidino groups. Finally, we show that the GFA ligands could be linked to one- or two-dimensional coordination polymers and porous materials with a layer structure by reaction with silver halides. PMID:25188743

  13. Uranyl acetate causes DNA single strand breaks in vitro in the presence of ascorbate (vitamin C).

    PubMed

    Yazzie, Monica; Gamble, Shania L; Civitello, Edgar R; Stearns, Diane M

    2003-04-01

    Uranium is a radioactive heavy metal with isotopes that decay on the geological time scale. People are exposed to uranium through uranium mining, processing, the resulting mine tailings, and the use of depleted uranium in the military. Acute exposures to uranium are chemically toxic to the kidney; however, little is known about chronic exposures, for example, if there is a direct chemical genotoxicity of uranium. The hypothesis that is being tested in the current work is that hexavalent uranium, as uranyl ion, may have a chemical genotoxicity similar to that of hexavalent chromium. In the current study, reactions of uranyl acetate (UA) and ascorbate (vitamin C) were observed to produce plasmid relaxation in pBluescript DNA. DNA strand breaks increased with increasing concentrations of a 1:1 reaction of UA and ascorbate but were not affected by increasing the ratio of ascorbate. Plasmid relaxation was inhibited by coincubation of reactions with catalase but not by coincubation with the radical scavengers mannitol, sodium azide, or 5,5-dimethyl-1-pyrroline-N-oxide. Reactions of UA and ascorbate monitored by (1)H NMR spectroscopy showed formation of a uranyl ascorbate complex, with no evidence of a dehydroascorbate product. A previous study inferred that hydroxyl radical formation was responsible for oxidative DNA damage in the presence of reactions of uranyl ion, hydrogen peroxide, and ascorbate [Miller et al. (2002) J. Bioinorg. Chem. 91, 246-252]. Current results, in the absence of added hydrogen peroxide, were not completely consistent with the interpretation that strand breaks were produced by a Fenton type generation of reactive oxygen species. Data were also consistent with the interpretation that a uranyl ascorbate complex was catalyzing hydrolysis of the DNA-phosphate backbone, in a manner similar to that known for the lanthanides. These data suggest that uranium may be directly genotoxic and may, like chromium, react with DNA by more than one pathway. PMID:12703969

  14. A Highly Reactive Seven-Coordinate Osmium(V) Oxo Complex: [Os(V) (O)(qpy)(pic)Cl](2.).

    PubMed

    Liu, Yingying; Ng, Siu-Mui; Lam, William W Y; Yiu, Shek-Man; Lau, Tai-Chu

    2016-01-01

    Seven-coordinate ruthenium oxo species have been proposed as active intermediates in catalytic water oxidation by a number of highly active ruthenium catalysts, however such species have yet to be isolated. Reported herein is the first example of a seven-coordinate group?8 metal-oxo species, [Os(V) (O)(qpy)(pic)Cl](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine, pic=4-picoline). The X-ray crystal structure of this complex shows that it has a distorted pentagonal bipyramidal geometry with an Os?O distance of 1.7375?. This oxo species undergoes facile O-atom and H-atom-transfer reactions with various organic substrates. Notably it can abstract H atoms from alkylaromatics with C?H bond dissociation energy as high as 90?kcal?mol(-1) . This work suggests that highly active oxidants may be designed based on group?8 seven-coordinate metal oxo species. PMID:26554748

  15. Reaction of the uranyl(VI) ion (UO(2)(2+)) with a triamidoamine ligand: preparation and structural characterization of a mixed-valent uranium(V/VI) oxo-imido dimer.

    PubMed

    Duval, P B; Burns, C J; Buschmann, W E; Clark, D L; Morris, D E; Scott, B L

    2001-10-22

    The synthesis and structural characterization of a mixed-valent uranium(V/VI) oxo-imido complex are reported. Reaction of the uranyl chloride complex [K(18-crown-6)](2)[UO(2)Cl(4)] (1) with the triamidoamine ligand Li(3)[N(CH(2)CH(2)NSiBu(t)Me(2))(3)] yields oxo-imido [K(18-crown-6)(Et(2)O)][UO(mu(2)-NuCH(2)CH(2)N(CH(2)CH(2)NSiBu(t)Me(2))(2))](2) (2) as the major isolated uranium product in moderate yield. The reaction that forms 2 involves activation of both the triamidoamine ligand and the uranyl dioxo unit of 1. An X-ray crystal structure determination of 2 reveals a dimeric complex in which the coordination geometry at each uranium center is that of a capped trigonal bipyramid. The multidentate triamidoamine ligand coordinates to uranium through the capping amine and two of the three pendant amido ligands, while the third pendant amido donor has been activated to generate a bridging imido ligand by loss of the silyl substituent. One of the uranyl oxo groups is retained as a terminal ligand to complete the coordination sphere for each uranium center. The oxo and imido nitrogen may be regarded as the axial ligands of the trigonal bipyramid, while the two amido ligands and the other imido donor occupy equatorial coordination sites. The central amine of the tripodal set serves as the capping ligand. Distortion of the axial O-U-N angle from 180 degrees emanates from the proximity of the capping amine and the bridging interaction to the other uranium center. The structure and bonding in 2 are assessed in the context of metal-ligand multiple bonding in high-valent actinide complexes. The possibility of valence averaging [5.5/5.5 vs 5.0/6.0] via delocalization or rapid intramolecular electron-transfer dynamics of the unpaired electron is also discussed in the context of crystallographic, spectroscopic (NMR, IR, Raman, and EPR), and electrochemical data. Crystal data for 2: triclinic space group P1 macro, a = 12.1144(6) A, b = 12.6084(6) A, c = 14.5072(7) A, alpha = 101.374(1) degrees, beta = 103.757(1) degrees, gamma = 109.340(1) degrees, z = 1, R1 = 0.0523, wR2 = 0.1359. PMID:11599946

  16. Effect of Geometrical Distortion on the Electronic Structure: Synthesis and Characterization of Monoradical-Coordinated Mononuclear Cu(II) Complexes.

    PubMed

    Ghorai, Samir; Sarmah, Amrit; Roy, Ram Kinkar; Tiwari, Archana; Mukherjee, Chandan

    2016-02-15

    Ligand H3Sami(Mixed(tBu)) was composed of two different compartments, a redox-active 2-aminophenol and a salen salicylidene. Both compartments were linked via a benzyl linker. The ligand reacted with CuCl2路2H2O under air in the presence of Et3N and provided the corresponding monoradical-coordinated mononuclear Cu(II) complex (1). Complex 1, in solution, reacted with air and provided complex 2 via ligand-centered oxygenation at the benzyl-CH2 position. Both complexes were characterized via IR, mass spectrometry, X-ray single-crystal diffraction, variable-temperature magnetic susceptibility, cyclic voltammograms (CVs), and UV-vis/NIR spectroscopic techniques. X-ray crystallographic analyses clearly showed almost equally distorted square planar geometry around the Cu(II) atom in both complexes. However, the bending of the radical-containing C6 ring compared to the N1-Cu1-O1 plane was different in both complexes. While complex 1 was paramagnetic and showed a ferromagnetic coupling between the dx(2)-y(2) magnetic orbital of Cu(II) ion and the pz orbital of coordinated 蟺-radical, complex 2 was diamagnetic by experiencing a strong antiferromagnetic coupling between the two magnetic orbitals. UV-vis/NIR spectra of the complexes were dominated by charge-transfer transitions. CVs of the complexes showed two reversible one-electron oxidations and one reversible one-electron reduction. E1/2(ox2) and E1/2(red1) potentials were different in both complexes, while E1/2(ox1) values were almost the same and the process corresponded to the formation of phenoxyl radical. Theoretical studies were also performed to understand the magnetic coupling phenomena, and TD-DFT calculations were employed for the assignment of charge-transfer absorption bands. PMID:26812584

  17. 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

  18. Observation of Radiolytic Field Alteration of the Uranyl Cation in Bicarbonate Solution

    SciTech Connect

    Snow, Lanee; McNamara, Bruce; Sinkov, Sergei; Cho, Herman; Friese, Judah

    2007-07-01

    Auto radiolysis of uranium (VI) carbonate solutions between pH 5.9 and 7.2 is shown to alter the uranium speciation over relatively short periods of time and was followed by {sup 13}C NMR and visible spectrophotometry, using dissolved [({sup 233}UO{sub 2}){sub 3}(CO{sub 3}){sub 6}]{sup 6-} both as the radiolysis source (D 14.9 Gy/hr) and as a trap for the newly formed hydrogen peroxide. The speciation is different than the uranyl mixed peroxy carbonate species that have been reported for higher pH carbonate solutions. Direct addition of hydrogen peroxide to solutions of the uranyl-carbonate trimer is shown to reproduce the {sup 13}C, {sup 17}O NMR signatures of the complex(es) formed by radiolysis, but additionally a variety of new complexes are revealed. Ratios of H{sub 2}O{sub 2}/trimer <1.5 produced uranyl peroxo carbonate adducts that are shown to be common to the radiolytically produced species. Ratios of H{sub 2}O{sub 2}/trimer >1.5 resulted in formation of stable higher order peroxo carbonate complexes. The {sup 13}C, {sup 17}O NMR signatures and visible spectra of these complexes are described here. Rigorous characterization of the species is an ongoing effort. (authors)

  19. Correlated coordination and redox activity of a hemilabile noninnocent ligand in nickel complexes.

    PubMed

    Paretzki, Alexa; Bubrin, Martina; Fiedler, Jan; Z醠i, Stanislav; Kaim, Wolfgang

    2014-04-25

    The compound [Ni(QM)2], QM = 4,6-di-tert-butyl-N-(2-methylthiomethylphenyl)-o-iminobenzoquinone, is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom and without any Ni-S bonding interaction. One-electron oxidation results in additional twofold Ni-S coordination (dNi-S ?2.38?) to produce a complex cation of [Ni(QM)2](PF6) with hexacoordinate Ni(II) and two distinctly different mer-configurated tridentate ligands. The O,O'-trans arrangement in the neutral precursor is changed to an O,O'-cis configuration in the cation. The EPR signal of [Ni(QM)2](PF6) has a very large g anisotropy and the magnetic measurements indicate an S = 3/2 state. The dication was structurally characterized as [Ni(QM)2](ClO4)2 to exhibit a similar NiN2O2S2 framework as the monocation. However, the two tridentate (O,N,S) ligands are now equivalent according to the formulation [Ni(II)(QM(0))2](2+). Cyclic voltammetry reflects the qualitative structure change on the first, but not on the second oxidation of [Ni(QM)2], and spectroelectrochemistry reveals a pronounced dependence of the 800-900?nm absorption on the solvent and counterion. Reduction of the neutral form occurs in an electrochemically reversible step to yield an anion with an intense near-infrared absorption at 1345?nm (? = 10,400?M(-1) ?cm(-1)) and a conventional g factor splitting for a largely metal-based spin (S = 1/2), suggesting a [(QM(-))Ni(II)(QM(2-))](-) configuration with a tetracoordinate metal atom with antiferromagnetic Ni(II)-(QM(-)) interactions and symmetry-allowed ligand-to-ligand intervalence charge transfer (LLIVCT). Calculations are used to understand the Ni-S binding activity as induced by remote electron transfer at the iminobenzoquinone redox system. PMID:24665084

  20. GRAPHITE PRODUCTION UTILIZING URANYL NITRATE HEXAHYDRATE CATALYST

    DOEpatents

    Sheinberg, H.; Armstrong, J.R.; Schell, D.H.

    1964-03-10

    ABS>The graphitizing of a mixture composed of furfuryl alcohol binder and uranyl nitrate hexahydrate hardener and the subsequent curing, baking, and graphitizing with pressure being initially applied prior to curing are described. The pressure step may be carried out by extrusion, methyl cellulose being added to the mixture before the completion of extrusion. Uranium oxide may be added to the graphitizable mixture prior to the heating and pressure steps. The graphitizable mixture may consist of discrete layers of different compositions. (AEC)

  1. Cyanex based uranyl sensitive polymeric membrane electrodes.

    PubMed

    Badr, Ibrahim H A; Zidan, W I; Akl, Z F

    2014-01-01

    Novel uranyl selective polymeric membrane electrodes were prepared using three different low-cost and commercially available Cyanex extractants namely, bis(2,4,4-trimethylpentyl) phosphinic acid [L1], bis(2,4,4-trimethylpentyl) monothiophosphinic acid [L2] and bis(2,4,4-trimethylpentyl) dithiophosphinic acid [L3]. Optimization and performance characteristics of the developed Cyanex based polymer membrane electrodes were determined. The influence of membrane composition (e.g., amount and type of ionic sites, as well as type of plasticizer) on potentiometric responses of the prepared membrane electrodes was studied. Optimized Cyanex-based membrane electrodes exhibited Nernstian responses for UO?(2+) ion over wide concentration ranges with fast response times. The optimized membrane electrodes based on L1, L2 and L3 exhibited Nernstian responses towards uranyl ion with slopes of 29.4, 28.0 and 29.3 mV decade(-1), respectively. The optimized membrane electrodes based on L1-L3 showed detection limits of 8.3 10(-5), 3.0 10(-5) and 3.3 10(-6) mol L(-1), respectively. The selectivity studies showed that the optimized membrane electrodes exhibited high selectivity towards UO?(2+) ion over large number of other cations. Membrane electrodes based on L3 exhibited superior potentiometric response characteristics compared to those based on L1 and L2 (e.g., widest linear range and lowest detection limit). The analytical utility of uranyl membrane electrodes formulated with Cyanex extractant L3 was demonstrated by the analysis of uranyl ion in different real samples for nuclear safeguards verification purposes. The results obtained using direct potentiometry and flow-injection methods were compared with those measured using the standard UV-visible and inductively coupled plasma spectroscopic methods. PMID:24274282

  2. Nonrelativistic Compton scattering in Furry's picture. III. Kramers-Heisenberg transition amplitude by means of the complex-coordinate method

    NASA Astrophysics Data System (ADS)

    Froelich, Piotr; Weyrich, Wolf

    1986-08-01

    The procedure for calculating the general Kramers-Heisenberg transition amplitude for scattering of light is presented. The procedure is based on L2 atomic structure calculations implemented within the framework of the complex-coordinate method, gives the transition amplitudes without explicit calculation of the final states, and includes the contribution from ? 2 terms, p? terms to second order, and interference terms between these scattering contributions.

  3. Structural Insights into Complete Metal Ion Coordination from Ternary Complexes of B Family RB69 DNA Polymerase

    SciTech Connect

    Xia, Shuangluo; Wang, Mina; Blaha, Gregor; Konigsberg, William H.; Wang, Jimin

    2011-10-20

    We have captured a preinsertion ternary complex of RB69 DNA polymerase (RB69pol) containing the 3' hydroxyl group at the terminus of an extendable primer (ptO3') and a nonhydrolyzable 2'-deoxyuridine 5'-{alpha},{beta}-substituted triphosphate, dUpXpp, where X is either NH or CH{sub 2}, opposite a complementary templating dA nucleotide residue. Here we report four structures of these complexes formed by three different RB69pol variants with catalytically inert Ca{sup 2+} and four other structures with catalytically competent Mn{sup 2+} or Mg{sup 2+}. These structures provide new insights into why the complete divalent metal-ion coordination complexes at the A and B sites are required for nucleotidyl transfer. They show that the metal ion in the A site brings ptO3' close to the {alpha}-phosphorus atom (P{alpha}) of the incoming dNTP to enable phosphodiester bond formation through simultaneous coordination of both ptO3' and the nonbridging Sp oxygen of the dNTP's {alpha}-phosphate. The coordination bond length of metal ion A as well as its ionic radius determines how close ptO3' can approach P{alpha}. These variables are expected to affect the rate of bond formation. The metal ion in the B site brings the pyrophosphate product close enough to P{alpha} to enable pyrophosphorolysis and assist in the departure of the pyrophosphate. In these dUpXpp-containing complexes, ptO3' occupies the vertex of a distorted metal ion A coordination octahedron. When ptO3' is placed at the vertex of an undistorted, idealized metal ion A octahedron, it is within bond formation distance to P{alpha}. This geometric relationship appears to be conserved among DNA polymerases of known structure.

  4. A series of mononuclear quasi-two-coordinate copper(I) complexes employing a sterically demanding thiolate ligand.

    PubMed

    Groysman, Stanislav; Holm, R H

    2009-01-19

    A series of two-coordinate thiolate complexes [Cu(SAr*)L] was synthesized as possible reactants in forming analogues of the active site of Mo/Cu-containing carbon monoxide dehydrogenase. Complexes with L = PPh(3) (1), 2,6-lutidine (2), and the N-heterocyclic carbene Pr(i)(2)NHCMe(2) (3) have been prepared by the reaction of [CuCl(PPh(3))(3)] (1) or [CuBr(SMe(2))] (2, 3) with ligand L and the exceptionally sterically encumbered ligand Ar*S = 2,6-bis(2,4,6-triisopropylphenyl)benzenethiolate(1-). The reaction of [CuBr(SMe(2))] with the thiolate in the absence of added L afforded trinuclear [Cu(3)(SAr*)(2)Br] (7). The carbene complex (3) undergoes Cu-C bond insertion with sulfur to form the thiourea complex [Cu(SAr*)(Pr(i)(2)Me(2)ImS)] (4). The complexes [Cu(Ar*)L] with L = tetrahydrothiophene (5) and 2,6-lutidine (6) were obtained by reaction of Ar*Li(OEt(2)) with CuBr/L. These species did not undergo clean Cu-C bond insertion with sulfur transfer agents; the disulfide Ar*SSCH(2)Ph (9) was isolated from the reaction of 6 with (PhCH(2)S)(2)S. The structures of all complexes and 9 were determined. Whereas 5 and 6 are strictly two-coordinate with linear C-Cu-L angles, 1-4 are quasi-two-coordinate because of weak 3d-C(ppi) interactions with a phenyl group, leading to nonlinear structures (S-Cu-L = 135-164 degrees). PMID:19138143

  5. Coordination and insertion of alkenes and alkynes in Au(III) complexes: nature of the intermediates from a computational perspective.

    PubMed

    Balcells, David; Eisenstein, Odile; Tilset, Mats; Nova, Ainara

    2016-04-01

    The contribution of Au(III) species to catalysis is still debated due to the limited number of characterized intermediates with this oxidation state. In particular, the coordination of alkenes and alkynes to Au(III) followed by insertion into Au(III)-X bonds has been suggested but rarely proven experimentally. Here, these reactions are explored by means of DFT and CCSD(T) calculations considering [AuX3(L)] and [AuX2(L)2](+) complexes. In these complexes, L = ethylene and acetylene have been chosen as substrates of high interest and representative of any unsaturated organic substrate, whereas X is Cl, Me or H, as found in metal salts and as model for intermediates involved in catalysis. Isoelectronic Pt(II) complexes are also considered for comparison. Ethylene coordination occurs preferentially perpendicular for all X except H, whereas for acetylene, coordination takes place in-plane for all X except Cl. These coordination isomers can represent either minima (intermediates) or saddle points (transition states) on the potential energy surface, depending on X. NBO analysis shows how this variety of structures results from the combination of electronic (M-L donation and back-donation) and steric (cis L-X repulsion) effects. With the sole exception of [AuMe2(ethylene)2](+), rotation of the unsaturated ligand and insertion into a cis Au-X bond involve low to moderate energy barriers, 螖G(鈥) = 2.5 to 23.5 kcal mol(-1), and are thermodynamically feasible, 螖G = 4.3 to -47.2 kcal mol(-1). The paucity of experimental observations for such reactions should thus be caused by other factors, like the participation of the intermediates and products in competitive side reactions including the reductive elimination of XCHnCHnX (n = 1 or 2). PMID:26905649

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

    SciTech Connect

    Karadag, E.; Saraydin, D.; Gueven, O.

    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.

  7. Three-coordinate nickel(II) and nickel(I) thiolate complexes based on the ?-diketiminate ligand system.

    PubMed

    Horn, Bettina; Limberg, Christian; Herwig, Christian; Braun, Beatrice

    2014-07-01

    Mononuclear nickel(II) thiolate complexes [L(tBu)Ni(SEt)] (1) and [L(tBu)Ni(aet)] (2, aet = (-)S(CH2)2NH2) (L(tBu) = [HC(C((t)Bu)NC6H3((i)Pr)2)2](-)), supported by a bulky nacnac ligand, were synthesized by treatment of the nickel(II) bromide precursor [L(tBu)Ni(Br)] (I) with the potassium salts of ethanethiol and cysteamine, respectively. The nickel atom in 1 features a planar T-shaped environment, while the Ni ion within 2 shows a distorted square planar coordination geometry, as the aminoethanethiolate (aet) is coordinated as a chelating ligand. In 2 the ?-diketiminate ligand binds in a rarely observed ?(2)C,N coordination mode. Reduction of complex 1 or its benzenethiolate analogue [L(tBu)Ni(SPh)] (II) by KC8 resulted in the formation of dinuclear Ni(I) thiolates (K稯Et2)(K)[L(tBu)Ni(SEt)]2 (3) and (K稯Et2)2[L(tBu)Ni(SPh)]2 (4), respectively. In these compounds [L(tBu)Ni(SR)](-) units are held together by potassium cations produced in the reduction process. All compounds mentioned were structurally characterized by single-crystal X-ray crystallography. PMID:24914615

  8. Heteroscorpionate-based Co2+, Zn2+, and Cu2+ complexes: coordination behavior, aerobic oxidation, and hydrogen sulfide detection.

    PubMed

    Strianese, Maria; Milione, Stefano; Bertolasi, Valerio; Pellecchia, Claudio; Grassi, Alfonso

    2011-02-01

    The coordination behavior and reactivity of the phenol-substituted bis(pyrazolyl)methane ligands, (3,5-(t)Bu(2)-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L1-H) and 2-phenol-bis(3,5-Me(2)-pyrazol-1-yl)methane (L2-H) have been investigated in the metal complexes (L1-H)CoCl(2) (1), (L1-H)ZnCl(2) (2), (L3)CuCl(2) (3), (L2)(2)Co(2)Cl(2) (4) (L2-H)ZnCl(2) (5), and (L2-H)CuCl(2)稨(2)O (6). The mononuclear tetrahedral cobalt complex 1 was isolated and fully characterized by X-ray single crystal diffraction and (1)H NMR spectroscopy and relaxometry. The neutral L1-H is ?(2)-coordinated to the metal center whereas the not coordinated hydroxy-phenyl group is involved in extended intermolecular hydrogen bonds. Aerobic oxidation of L1-H was observed in the reaction of this ligand with CuCl(2) to yield the para-quinone derivative L3 (L3 = 2-(t)Bu-6-(bis(3,5-Me(2)-pyrazol-1-yl)methyl)cyclohexa-2,5-diene-1,4-dione). Upon oxidation L3 resulted ?(2)-coordinated to the tetrahedral Cu(II) metal center, affording 3. The reaction of L2-H with CoCl(2)6H(2)O produced the elimination of 1 equiv of hydrochloric acid and the formation of the binuclear complex 4 in which one cobalt is in an octahedral environment featuring two ?(3)-coordinated deprotonated ligands whereas the second cobalt center is detected in tetrahedral coordination geometry, bound to the octahedral cobalt via two phenoxo bridging moieties. Interestingly L2-H, (3-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L4-H), or (5-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L5-H) were not oxidized in the reaction with CuCl(2). The reaction of the ligand L2-H with ZnCl(2) and CuCl(2)2H(2)O yielded the ?(2)-coordinated tetrahedral complex 5 and the square planar complex 6, respectively. The application of the cobalt complex 1 as molecular dosimeter for H(2)S was explored and compared to that of the zinc analogue 2. Density functional theory (DFT) calculations and NMR experiments to assess the possible mechanisms of H(2)S detection by both 1 and 2 are also described. PMID:21214208

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

    SciTech Connect

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

    2003-04-01

    The complexation of uranium(VI) and samarium(III) with oxydiacetate in 1.05 mol kg{sup -1} NaClO{sub 4} is studied at variable temperatures (25-70 C). Three U(VI)/O DA complexes (UO{sub 2}L, UO{sub 2}L{sub 2}{sup 2-}, and UO{sub 2}HL{sub 2}{sup -}) and three Sm(III)/ODA complexes (SmL{sub j}{sup (3-2j)+} 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{sub p}{sup o} in J K{sup -1} mol{sup -1}) are 95 {+-} 6, 297 {+-} 14, and 162 {+-} 19 for UO{sub 2}L, UO{sub 2}L{sub 2}{sup 2-}, and UO{sub 2}HL{sub 2}{sup -}, and 142 {+-} 6, 198 {+-} 14 and 157 {+-} 19 for SmL{sup +}, SmL{sub 2}{sup -}, and SmL{sub 3}{sup 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.

  10. Syntheses and structures of uranyl ethylenediphosphonates: from layers to elliptical nanochannels.

    PubMed

    Tian, Tao; Yang, Weiting; Wang, Hao; Dang, Song; Pan, Qing-Jiang; Sun, Zhong-Ming

    2013-06-17

    A family of uranium diphosphonates have been hydrothermally synthesized through the reaction of ethylenediphosphonic acid (EDP, H4L) and uranyl nitrate/zinc uranyl acetate in the presence of organic templates, such as tetraethyl ammonium (NEt4(+)), 4,4'-bipyridine (bipy), and 1,10-phenanthroline (phen). The UO2(2+) in UO2(H2O)(H2L)(EDP-U1) is equatorially five-coordinated by four phosphonate groups and one aqua ligand, forming a pentagonal bipyramid. Each EDP ligand is doubly protonated and chelates three UO2(2+), resulting in a layered structure. Compounds (NEt4)2(UO2)3(HL)2(H2L)4H2O (EDP-U2) and (H2bipy)UO2L (EDP-U3) have the same layered structure in which NEt4(+) and protonated bipy fill in the uranyl-phosphonate interlayers, respectively, and play a role to balance the negative charges. Different from that in EDP-U1, the UO2(2+) exists in the form of a UO6 tetragonal bipyramid and is surrounded by four different EDP ligands in EDP-U2 and EDP-U3. (Hphen)2(UO2)2(H2L)3 (EDP-U4) features a three-dimensional framework structure with large elliptical channels along the c axis (1.3 1.1 nm(2)). Monoprotonated phen molecules fill in these channels and hold together through strong ?贩? interactions. All of the four compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations. The ion-exchange study indicates that [Co(en)3](3+) could partially replace the protonated phen molecules. PMID:23701415

  11. Dance choreography is coordinated with song repertoire in a complex avian display.

    PubMed

    Dalziell, Anastasia H; Peters, Richard A; Cockburn, Andrew; Dorland, Alexandra D; Maisey, Alex C; Magrath, Robert D

    2013-06-17

    All human cultures have music and dance, and the two activities are so closely integrated that many languages use just one word to describe both. Recent research points to a deep cognitive connection between music and dance-like movements in humans, fueling speculation that music and dance have coevolved and prompting the need for studies of audiovisual displays in other animals. However, little is known about how nonhuman animals integrate acoustic and movement display components. One striking property of human displays is that performers coordinate dance with music by matching types of dance movements with types of music, as when dancers waltz to waltz music. Here, we show that a bird also temporally coordinates a repertoire of song types with a repertoire of dance-like movements. During displays, male superb lyrebirds (Menura novaehollandiae) sing four different song types, matching each with a unique set of movements and delivering song and dance types in a predictable sequence. Crucially, display movements are both unnecessary for the production of sound and voluntary, because males sometimes sing without dancing. Thus, the coordination of independently produced repertoires of acoustic and movement signals is not a uniquely human trait. PMID:23746637

  12. Making oxidation potentials predictable: coordination of additives applied to the electronic fine tuning of an iron(II) complex.

    PubMed

    Haslinger, Stefan; K點k, Jens W; Hahn, Eva M; Cokoja, Mirza; P鰐hig, Alexander; Basset, Jean-Marie; K黨n, Fritz E

    2014-11-01

    This work examines the impact of axially coordinating additives on the electronic structure of a bioinspired octahedral low-spin iron(II) N-heterocyclic carbene (Fe-NHC) complex. Bearing two labile trans-acetonitrile ligands, the Fe-NHC complex, which is also an excellent oxidation catalyst, is prone to axial ligand exchange. Phosphine- and pyridine-based additives are used for substitution of the acetonitrile ligands. On the basis of the resulting defined complexes, predictability of the oxidation potentials is demonstrated, based on a correlation between cyclic voltammetry experiments and density functional theory calculated molecular orbital energies. Fundamental insights into changes of the electronic properties upon axial ligand exchange and the impact on related attributes will finally lead to target-oriented manipulation of the electronic properties and consequently to the effective tuning of the reactivity of bioinspired systems. PMID:25333790

  13. Photoinduced single-molecule magnet properties in a four-coordinate iron(II) spin crossover complex.

    PubMed

    Mathoni鑢e, Corine; Lin, Hsiu-Jung; Siretanu, Diana; Cl閞ac, Rodolphe; Smith, Jeremy M

    2013-12-26

    The four-coordinate Fe(II) complex, PhB(MesIm)3Fe-N?PPh3 (1) has been previously reported to undergo a thermal spin-crossover (SCO) between high-spin (HS, S = 2) and low-spin (LS, S = 0) states. This complex is photoactive below 20 K, undergoing a photoinduced LS to HS spin state change, as determined by optical reflectivity and photomagnetic measurements. With continuous white light irradiation, 1 displays slow relaxation of the magnetization, i.e. single-molecule magnet (SMM) properties, at temperatures below 5 K. This complex provides a structural template for the design of new photoinduced mononuclear SMMs based on the SCO phenomenon. PMID:24313622

  14. Synthesis, characterization, and DFT studies of thione and selone Cu(I) complexes with variable coordination geometries.

    PubMed

    Kimani, Martin M; Bayse, Craig A; Brumaghim, Julia L

    2011-04-14

    Coordination of Cu(I) halides with N,N'-dimethylimidazole selone (dmise) and thione (dmit) ligands was examined by treating CuX (X = Cl, Br, I) with one or two equivalents of dmise or dmit. The reaction of CuI and CuBr with one molar equivalent of dmise results in unusual selenium-bridged tetrameric Cu(4)(?-dmise)(4)(?-X)(2)X(2) copper complexes with average Cu-Se bond lengths of 2.42 and a Cu(2)(?-X)(2) core (X = I (1) or Br (6)) that's in a rhomboidal structure. The reaction of CuX (X = Cl, Br, and I) with two equivalents of dmit or dmise results in trigonal planar Cu(I) complexes of two different conformations with the formula Cu(dmit)(2)X (3a, 3b, 4, and 7) or Cu(dmise)(2)X (2, 5, and 8) with average Cu-S and Cu-Se bond lengths of 2.23 and 2.34 , respectively. The coordination geometry around the copper center in complexes 1 to 8 is determined by the type of halide and chalcogenone ligand used, intramolecular ?-? interactions, and short contact interactions between X-H (X = I, Br, Cl, Se or S). The theoretical DFT calculations are in good agreement with experimental X-ray structural data and indicate that dmise ligands are required for formation of the tetrameric complexes 1 and 6. Electrochemical studies show that the trigonal copper selone complexes have more negative potentials relative to analogous copper thione complexes by an average of 108 mV. PMID:21384035

  15. 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 in爒itro. 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

  16. Pillared and open-framework uranyl diphosphonates

    SciTech Connect

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

    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.

  17. Phosphate coordination and movement of DNA in the Tn5 synaptic complex: role of the (R)YREK motif

    SciTech Connect

    Klenchin, Vadim A.; Czyz, Agata; Goryshin, Igor Y.; Gradman, Richard; Lovell, Scott; Rayment, Ivan; Reznikoff, William S.

    2009-01-15

    Bacterial DNA transposition is an important model system for studying DNA recombination events such as HIV-1 DNA integration and RAG-1-mediated V(D)J recombination. This communication focuses on the role of protein-phosphate contacts in manipulating DNA structure as a requirement for transposition catalysis. In particular, the participation of the nontransferred strand (NTS) 5' phosphate in Tn5 transposition strand transfer is analyzed. The 5' phosphate plays no direct catalytic role, nonetheless its presence stimulates strand transfer {approx}30-fold. X-ray crystallography indicates that transposase-DNA complexes formed with NTS 5' phosphorylated DNA have two properties that contrast with structures formed with complexes lacking the 5' phosphate or complexes generated from in-crystal hairpin cleavage. Transposase residues R210, Y319 and R322 of the (R)YREK motif coordinate the 5' phosphate rather than the subterminal NTS phosphate, and the 5' NTS end is moved away from the 3' transferred strand end. Mutation R210A impairs the 5' phosphate stimulation. It is posited that DNA phosphate coordination by R210, Y319 and R322 results in movement of the 5' NTS DNA away from the 3'-end thus allowing efficient target DNA binding. It is likely that this role for the newly identified RYR triad is utilized by other transposase-related proteins.

  18. Insight into magnesium coordination environments in benzoate and salicylate complexes through 25Mg solid-state NMR spectroscopy.

    PubMed

    Burgess, Kevin M N; Xu, Yang; Leclerc, Matthew C; Bryce, David L

    2013-08-01

    We report on the (25)Mg solid-state nuclear magnetic resonance (NMR) characterization of a series of magnesium complexes featuring Mg(2+) ions in organic coordination environments. Six compounds have been synthesized with benzoate and salicylate ligands, which are typically used as linkers in metal organic frameworks (MOFs). The use of ultrahigh-field solid-state NMR has revealed a relatively large range of values for the (25)Mg quadrupolar coupling constant, CQ((25)Mg), in these compounds. In contrast to some previously studied inorganic Mg(2+) complexes, the values of CQ((25)Mg) in organic Mg(2+) complexes are well rationalized by the degree of octahedral strain of the "MgO6" coordination polyhedra. (13)C and (25)Mg isotropic chemical shifts were also found to be sensitive to the binding mode of the carboxylate ligands. The experimental findings are corroborated by gauge-including projector-augmented-wave (GIPAW) density functional theory (DFT) computations, and these have allowed for an interpretation of the experimentally observed trend in the CQ((25)Mg) values and for the visualization of the EFG tensor principal components with respect to the molecular structure. These new insights may prove to be valuable for the understanding and interpretation of (25)Mg NMR data for Mg(2+) ions in organic binding environments such as those found in MOFs and protein-divalent metal binding sites. PMID:23834478

  19. Formation and crystallographic elucidation of stable [4 + 2]-coordinate nickel(II) N,S-heterocyclic carbene (NSHC) complexes.

    PubMed

    Ding, Nini; Zhang, Jun; Hor, T S Andy

    2009-03-14

    A series of square-planar N,S-heterocyclic carbene (NSHC) complexes trans-[NiX(2)(N-RBzTh)(2)] (BzTh = benzothiazolin-2-ylidene) (R/X = Bz/Br; Me/I; Et/I; Pr(i)/I; Bu(i)/I) have been synthesized and characterized by X-ray single-crystal diffraction analysis. These are the first crystallographically established NSHC complexes of nickel in the literature. The N,S-heterocyclic carbene (NSHC) rings invariably twist away from co-planarity with the metal coordination plane such that the N-substituent moves on top and below the metal to facilitate electrostatic gamma-hydride interaction, thus giving an essentially [4 + 2] coordination at the Ni(ii) center. These compounds are active toward reductive Ullmann-type coupling reactions in Bu(4)NBr showing higher activities towards bromoanisole or bromotoluene than bromobenzene. The complex trans-[NiI(2)(N-Pr(i)BzTh)(2)] with the shortest NiH anagostic separation and a near-ideal orthogonal orientation between the carbene and metal planes gives the highest yields. PMID:19240921

  20. Effect of High Pressure on Uranyl Nanocages

    NASA Astrophysics Data System (ADS)

    Turner, K. M.; Zhang, F.; Pellegrini, K.; McGrail, B. T.; Burns, P. C.; Ewing, R. C.

    2013-12-01

    Uranyl nanocages U24Py12, U60, and U24 were studied in situ at high pressure in order to understand the response of these structures to pressure. Single crystals of the nanocage structures were analyzed by in situ Raman spectroscopy, synchrotron X-ray diffraction and small angle X-Ray scattering in diamond anvil cells, as well as electrospray ionization mass spectrometry. At ambient pressure conditions, U24Py12 is tetragonal (P42/mnm: a = 22.746(2) , c = 30.426(4) ), U60 is isometric (Fm-3: a=37.884(2) ), and U24 is triclinic (P1-: a=19.2111(11), b=31.003(2), c=32.252(2), ?=102.404(4), ?=99.506(4) , ?=95.362(4) ). Pressures ranged from ambient to 50 GPa; single crystals less than 200 microns in diameter were used. Two symmetric stretch modes of the uranyl ion are evident in the Raman spectra of all three nanocages with Raman shifts of 810 and 830 cm-1. The modes are clearly evident at pressures ranging from ambient to 4-8 GPa. At pressures higher than this range, the uranyl ion vibrational mode broadens further and shifts to higher stretching frequencies. The signal for U60 is irreversibly lost at 17 GPa, but for U24 and U24Py12, the signal persists and continues to broaden at pressures up to 50 GPa. After pressure quenching, there was still no signal from the U60, but U24 and U24Py12 both show one broad Raman mode at 840 cm-1. High pressure synchrotron X-ray diffraction measurements were completed at Argonne National Laboratory to quantify structural unit cell changes over the pressure ranges investigated. U24Py12 undergoes a phase transition to higher symmetry at approximately 5 GPa, and eventually partially amorphizes at 17 GPa, irreversibly. U60 undergoes a phase transition from isometric to tetragonal at 4.4 GPa, and amorphizes irreversibly at 10 GPa. Small angle X-ray scattering measurements show that the cluster topology is maintained even after amorphization of U24Py12 and U60. Mass spectrometry data indicate that these clusters remain intact at high pressures, despite the loss of long-range periodicity. These experiments provide insight into the stability of different types of uranyl nanocages, as well the relation between cluster topology and stability with increasing pressure.

  1. Metallochain cluster complexes and metallomacrocyclic triangles based on coordination bonds between palladium or platinum and diphosphinoacetylene ligands.

    PubMed

    Baumgartner, Thomas; Huynh, Keith; Schleidt, Silvia; Lough, Alan J; Manners, Ian

    2002-10-18

    To explore the potential of the coordination chemistry of Pd and Pt halides with phosphinoacetylene ligands for the generation of novel, highly metallated organometallic coordination polymers, investigations on model compounds [MX2(PPh2 C identical to CPh)2] that exhibit trans-configured Pd centers and cis-configured Pt centers have been performed. The molecular structure of the trans-Pd complexes 2 (M = Pd, X = Br) and 5 (M = Pd, X = I) appeared suitable for the generation of linear materials, whereas the cis-Pt complex 6 (M = Pt, X = I) suggested the prospective formation of ring systems. The presence of acetylene moieties allowed for further increase of metal concentration by cluster formation with [Co2(CO)8]. Two novel bimetal cluster complexes 7 and 8 were obtained from 5 and 6, respectively, and these exhibit a bridging iodine ligand as an interesting structural motif leading to heterocyclic systems with M-I-Co-C-P skeletons (M = Pd or Pt). A similar approach with [Fe2(CO)9] led to the formation of several products, including an unusual Pd-Fe cluster-containing compound 10. The extension of the coordination strategy to rigid bis(phosphinoacetylene) ligands gave rise to strained ring systems. Surprisingly, for the cis-configured PtCl2 center, a rarely observed triangular structure 12 was obtained exclusively. The corresponding PtI2 analog, 13a rearranged over time to form a "ring-fused" system 13b with an extended BINAP-like ligand. PMID:12362399

  2. Copper(II) Complexes of Cyclams Containing Nitrophenyl Substituents: Push-Pull Behavior and Scorpionate Coordination of the Nitro Group.

    PubMed

    Boiocchi, Massimo; Ciarrocchi, Carlo; Fabbrizzi, Luigi; Licchelli, Maurizio; Mangano, Carlo; Poggi, Antonio; V醶quez L髉ez, Miguel

    2015-11-01

    The three nitrophenyl-cyclam derivatives (nitrocyclams): 1-(4-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (2), 1-(2-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (3), and 1-(2,4-dinitrophenyl)-1,4,8,11-tetraazacyclotetradecane (4), in an MeCN solution, specifically incorporate the Cu(II) ion according to an irreversible process signaled by disappearance of the yellow color for a concentration c < 1 10(-4) M and by a yellow-to-red color change for c ? 1 10(-3), and must be considered efficient and specific dosimeters of copper(II) salts. When present in the ortho position of the nitrophenyl substituent, the -NO2 group coordinates the Cu(II) according to a scorpionate mode, while the metallocyclam system exhibits a trans-I configuration. In an MeCN solution the red trans-I-[Cu(II)(3)](2+) and trans-I-[Cu(II)(4)](2+) scorpionate complexes slowly convert into the violet trans-III scorpionate complexes. Kinetic aspects of the trans-I-to-trans-III configurational rearrangement were investigated in detail for the [Cu(II)(4)](2+) system. In particular, the conversion is spectacularly accelerated by catalytic amounts of Cl(-), NCO(-), and F(-). While for Cl(-) and NCO(-) the effect can be associated with the capability of the anion to stabilize through coordination a possible dissociative intermediate, the amazingly powerful effect of F(-) must be related to the preliminary deprotonation of one N-H fragment of the macrocycle, driven by the formation of the HF2(-) ion. Most of the metal complex species studied in solution were isolated in a crystalline form, and their molecular structures were elucidated through X-ray diffraction studies. This study documents the first examples of effective metal coordination by the nitro group. PMID:26468764

  3. The survivin/Aurora B complex: its role in coordinating tension and attachment.

    PubMed

    Lens, Susanne M A; Medema, Ren H

    2003-01-01

    Proper chromosome segregation relies on the action of the spindle checkpoint. Recent data have shown that the chromosomal passenger proteins survivin and Aurora B play an important auxiliary role in spindle checkpoint surveillance. Knock-down experiments in human cells indicate that the function of the survivin/Aurora B complex is required to correct improper microtubule-kinetochore interactions. Combined data of four different groups show that the survivin/Aurora B complex is not an integral component of the spindle checkpoint, but it enables the cell to communicate lack of tension back to the attached microtubules. Moreover, they show that the affinity of BubR1 for kinetochores is directly influenced by the absence or presence of the survivin/Aurora B complex. These functions of the survivin/Aurora B complex are essential for chromosome biorientation, a prerequisite for proper chromosome segregation. As such, this complex plays an important role in the maintenance of a stable genome. PMID:14504461

  4. 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, ultraviolet杤isible 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

  5. 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.

  6. Resolution of P-stereogenic P-heterocycles via the formation of diastereomeric molecular and coordination complexes (a review).

    PubMed

    Bagi, P閠er; Ujj, Vikt髍ia; Czugler, M醫y醩; Fogassy, Elem閞; Keglevich, Gy鰎gy

    2016-02-01

    TADDOL derivatives and the Ca(2+)-salts of tartaric acid derivatives were found to be versatile and generally applicable resolving agents for the preparation of the enantiomers of P-stereogenic heterocyclic phosphine oxides and phosphinates via the formation of the corresponding diastereomeric molecular and coordination complexes. A few of the diastereomeric intermediates were characterized by single crystal X-ray crystallography to gain insights into the binding mode of the corresponding heterocyclic phosphine oxide ("guest") and the resolving agent ("host") and to study the underlying phenomenon of enantiomeric recognition. PMID:26564410

  7. Unexpectedly strong magnetic anisotropy in a mononuclear eight-coordinate cobalt(II) complex: a theoretical exploration.

    PubMed

    Wei, Jin-Mei; Zhang, Yi-Quan

    2015-02-16

    Ab initio methods have been used to explore the unexpectedly strong magnetic anisotropy and the magnetostructural correlations in mononuclear eight-coordinate complex [Co(II)(12-crown-4)2](2+). Our calculations showed that both decreasing ? and increasing ? may enhance its magnetic anisotropy, which was rationalized by the qualitative theory proposed by Long and co-workers. Moreover, we deduced that the |D| value of [Co(II)(12-crown-4)2](2+) with ? = 52 and ? = 43 is the largest one. PMID:25614998

  8. Precursor-directed assembly of complex oxide nanobeads: the role of strongly coordinated inorganic anions.

    PubMed

    Nikonova, Olesya A; Nedelec, Jean-Marie; Kessler, Vadim G; Seisenbaeva, Gulaim A

    2011-09-20

    The use of an inorganic perrhenate ligand in the structure of early-transition-metal alkoxide precursors permits to achieve uniform self-assembly of the primary nanoparticles produced by their hydrolysis. The latter has been carried out in a hydrocarbon reaction medium by the addition of water with vigorous stirring, either in the pure form or in solutions in parent alcohols. The self-assembly is guided by the surface charge enhanced by the presence of strongly coordinated anions as determined by zeta potential measurements. The aggregation process has been followed in real time by nanoparticle tracking analysis (NanoSight technique). The reaction products are spherical aggregates with a size that can be efficiently controlled through the polarity of the reaction medium. The produced nanobeads have been characterized by TEM, SEM-EDS, DLS, nitrogen adsorption, and FTIR. The coordination of metal centers has been investigated using EXAFS spectroscopy. The aggregates remain amorphous on thermal treatment of up to 700 癈 (24 h treatment) but crystallize when treated at 1000 癈. This latter process is associated with the total loss of rhenium content and offers early-transition-metal oxides as products. PMID:21830800

  9. Dynamic Resectorization and Coordination Technology: An Evaluation of Air Traffic Control Complexity

    NASA Technical Reports Server (NTRS)

    Brinton, Christopher R.

    1996-01-01

    The work described in this report is done under contract with the National Aeronautics and Space Administration (NASA) to support the Advanced Air Transportation Technology (AATR) program. The goal of this program is to contribute to and accelerate progress in Advanced Air Transportation Technologies. Wyndemere Incorporated is supporting this goal by studying the complexity of the Air Traffic Specialist's role in maintaining the safety of the Air Transportation system. It is envisioned that the implementation of Free Flight may significantly increase the complexity and difficulty of maintaining this safety. Wyndemere Incorporated is researching potential methods to reduce this complexity. This is the final report for the contract.

  10. 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.

  11. Kinetics of triscarbonato uranyl reduction by aqueous ferrous iron: a theoretical study.

    PubMed

    Wander, Matthew C F; Kerisit, Sebastien; Rosso, Kevin M; Schoonen, Martin A A

    2006-08-10

    Uranium is a pollutant whose mobility is strongly dependent on its oxidation state. While U(VI) in the form of the uranyl cation is readily reduced by a range of natural reductants, by contrast complexation of uranyl by carbonate greatly reduces its reduction potential and imposes increased electron transfer (ET) distances. Very little is known about the elementary processes involved in uranium reduction from U(VI) to U(V) to U(IV) in general. In this study, we examine the theoretical kinetics of ET from ferrous iron to triscarbonato uranyl in aqueous solution. A combination of molecular dynamics (MD) simulations and density functional theory (DFT) electronic structure calculations is employed to compute the parameters that enter into Marcus' ET model, including the thermodynamic driving forces, reorganization energies, and electronic coupling matrix elements. MD simulations predict that two ferrous iron atoms will bind in an inner-sphere fashion to the three-membered carbonate ring of triscarbonato uranyl, forming the charge-neutral ternary Fe(2)UO(2)(CO(3))(3)(H(2)O)(8) complex. Through a sequential proton-coupled electron-transfer mechanism (PCET), the first ET step converting U(VI) to U(V) is predicted by DFT to occur with an electronic barrier that corresponds to a rate on the order of approximately 1 s(-1). The second ET step converting U(V) to U(IV) is predicted to be significantly endergonic. Therefore, U(V) is a stabilized end product in this ET system, in agreement with experiment. PMID:16884201

  12. 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.

  13. Regulation of CTnDOT Conjugative Transfer Is a Complex and Highly Coordinated Series of Events

    PubMed Central

    Waters, Jillian L.; Salyers, Abigail A.

    2013-01-01

    ABSTRACT CTnDOT is a 65-kb conjugative transposon that is found in Bacteroides spp., which are one of the more abundant members within the lower human gastrointestinal tract. CTnDOT encodes resistance to the antibiotics erythromycin and tetracycline (Tc). An interesting feature of CTnDOT is that exposure to low levels of Tc induces a cascade of events that ultimately results in CTnDOT conjugative transfer. However, Tc is apparently not a switch that activates transfer but rather a signal that appears to override a series of negative regulators that inhibit premature excision and transfer of CTnDOT. In this minireview, we summarize over 20爕ears of research that focused on elucidating the highly coordinated regulation of excision, mobilization, and transfer of CTnDOT. PMID:24169574

  14. Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions.

    PubMed

    Brulfert, Florian; Safi, Samir; Jeanson, Aur茅lie; Martinez-Baez, Ernesto; Roques, J茅r么me; Berthomieu, Catherine; Solari, Pier-Lorenzo; Sauge-Merle, Sandrine; Simoni, 脡ric

    2016-03-21

    Because of their presence in the nuclear fuel cycle, neptunium and uranium are two actinides of main interest in case of internal contamination. Complexation of U(VI) and Np(V) by the target protein calmodulin (CaMWT) was therefore studied herein. Both actinides have two axial oxygen atoms, which, charge aside, makes them very similar structurally wise. This work combines spectroscopy and theoretical density functional theory (DFT) calculations. Structural characterization was performed by extended X-ray absorption fine structure (EXAFS) at the LIII-edge for each studied actinide. Models for the binding site of the protein were developed and then refined by using DFT to fit the obtained experimental EXAFS data. The effect of hydrolysis was also considered for both actinides (the uranyl experiment was performed at pH 3 and 6, while the neptunyl experiment was conducted at pH 7 and 9). The effect of the pH variation was apparent on the coordination sphere of the uranyl complexes, while the neptunyl complex characteristics remained stable under both studied conditions. The DFT calculations showed that at near physiological pH the complex formed by CaMWT with the neptunium ion is more stable than the one formed with uranyl. PMID:26954703

  15. CORVET and HOPS tethering complexes - coordinators of endosome and lysosome fusion.

    PubMed

    Balderhaar, Henning J kleine; Ungermann, Christian

    2013-03-15

    Protein and lipid transport along the endolysosomal system of eukaryotic cells depends on multiple fusion and fission events. Over the past few years, the molecular constituents of both fission and fusion machineries have been identified. Here, we focus on the mechanism of membrane fusion at endosomes, vacuoles and lysosomes, and in particular on the role of the two homologous tethering complexes called CORVET and HOPS. Both complexes are heterohexamers; they share four subunits, interact with Rab GTPases and soluble NSF attachment protein receptors (SNAREs) and can tether membranes. Owing to the presence of specific subunits, CORVET is a Rab5 effector complex, whereas HOPS can bind efficiently to late endosomes and lysosomes through Rab7. Based on the recently described overall structure of the HOPS complex and a number of in vivo and in vitro analyses, important insights into their function have been obtained. Here, we discuss the general function of both complexes in yeast and in metazoan cells in the context of endosomal biogenesis and maturation. PMID:23645161

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

    PubMed Central

    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

  17. Structural analysis of nine-coordinate lanthanide complexes: steric control of the metal-water distance across the series.

    PubMed

    Parker, David; Puschmann, Horst; Batsanov, Andrei S; Senanayake, Kanthi

    2003-12-29

    The structures of 10 isomorphous lanthanide (Ln) complexes of a chiral DOTA tetra-amide ligand (L(1)), [LnL(1)(H(2)O)](CF(3)SO(3))(3).3H(2)O, crystallizing in space group P2(1), have been studied by single-crystal X-ray diffraction. The Ln coordination is a O(4)N(4) square antiprism, the O(4) base of which is capped by an aqua ligand. The sterically demanding position of the latter results in the lengthening of the Ln-OH(2) distance along the Pr to Lu series by 0.06 A (after allowing for the lanthanide contraction). In parallel, the distance between the bound water oxygen and the second-sphere water oxygen is reduced from 3.17 A (Pr) to 3.04 A (Lu), consistent with the enhanced hydrogen bond acceptor ability of the coordinated water oxygen across the series. A Cambridge Structural Database survey of [Ln(H(2)O)(9)](CF(3)SO(3))(3) salts (space group P6(3)/m) and of six reported isostructural complexes of DOTA [L(2)] revealed a similar trend. The implications of the resultant destabilization of the ground state structure for the water interchange process are discussed. PMID:14686841

  18. Dihydrogen complexes as prototypes for the coordination chemistry of saturated molecules

    PubMed Central

    Kubas, Gregory J.

    2007-01-01

    The binding of a dihydrogen molecule (H2) to a transition metal center in an organometallic complex was a major discovery because it changed the way chemists think about the reactivity of molecules with chemically 搃nert strong bonds such as HH and CH. Before the seminal finding of side-on bonded H2 in W(CO)3(PR3)2(H2), it was generally believed that H2 could not bind to another atom in stable fashion and would split into two separate H atoms to form a metal dihydride before undergoing chemical reaction. Metal-bound saturated molecules such as H2, silanes, and alkanes (?-complexes) have a chemistry of their own, with surprisingly varied structures, bonding, and dynamics. H2 complexes are of increased relevance for H2 production and storage in the hydrogen economy of the future. PMID:17442752

  19. Eight-coordinate stereochemistries of U(IV) catecholate and aquo complexes

    SciTech Connect

    Hay, Benjamin P.; Uddin, Jamal; Firman, Timothy K.

    2004-01-01

    An extended MM3 model has been used to identify all low energy configurations for U(IV) complexes with catecholate and aquo ligands. Both stochastic and systematic conformational analyses of[U(cat)n(OH2)8-n]4-2n complexes, n= 1 - 4, establish that 20 of the 67 possible stereochemistries are minima on the MM3 potential surface. The stable stereochemistries are reported for each stoichiometry and, where possible, the results are compared with experimental data and with the predictions from prior repulsion energy calculations.

  20. 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.

  1. 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鈥

  2. 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

  3. pH-Dependent Assembly and Conversions of Six Cadmium(II)-Based Coordination Complexes

    SciTech Connect

    Fang, Hua-Cai; Zhu, Ji-Qin; Zhou, Li-Jiang; Jia, Hong-Yang; Li, Shan-Shan; Gong, Xue; Li, Shu-Bin; Cai, Yue-Peng; Thallapally, Praveen K.; Liu, Jun; Exarhos, Gregory J.

    2010-05-20

    Six cadmium(II) complexes containing N2O2 donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L52Cl4)2]鈥H3OH鈥2O (1), [Cd(L5)Cl]2鈥H3OH (2), [Cd2(HL5)Cl4]n (3), {[Cd3(H2L5)2Cl8]鈥2H2O}n (4), [(H2L5)2]2+鈥CdCl4]2-鈥2O (5), and [(H2L5)2]2+鈥CdCl4]2- (6), have been synthesized using cadmium(II) chloride and asymmetrical Schiff base ligand HL5 under different pH conditions at room temperature. The diverse structures show the marked sensitivity of the structural chemistry of the tetradentate asymmetrical Schiff base ligand HL5. Complex 1 formed at pH = 10 exhibits a rare zero- dimensional structure of trinuclear cadmium (II). At pH = 8-9, a dinuclear cadmium (II) complex 2 is formed. The reaction at pH = 5-7 leads to two one-dimensional structures of 3 and 4. A further decrease of the pH to 3-5 results in a zero-dimensional structure 5. Owing to the departure of lattice water molecules in the crystal, complex 5 at room temperature can gradually undergo single-crystal-to-single-crystal transformation to result complex 6. The results further show that conversions of complex 1 to 5 can also be achieved by adjusting the pH value of the reaction solution, 1飩2pH=8飩5pH=3 and 3飩4pH=5. Comparing these experimental results, it is clear that the pH plays a crucial role in the formation of the resulting structures, which simultaneously provide very effective strategies for constructing the CdII compounds with N2O2 donor tetradentate asymmetrical Schiff base ligand. The strong fluorescent emissions of the six compounds (1-6) make them potentially useful photoactive materials. Furthermore, six Schiff base cadmium complexes (1鈥6), with DPPH (2,2-dipheny1-1-picrylhydrazy1) as a co-oxidant exhibited the stronger scavenging activity.

  4. Molecular orbital study of some eight-coordinate sulfur chelate complexes of molybdenum

    SciTech Connect

    Perkins, P.G.; Schultz, F.A.

    1983-03-30

    A number of molybdenum complexes involving the formal oxidation states Mo(IV) and Mo(V) have been studied by a self-consistent-field molecular orbital technique. All the complexes were of dodecahedral geometry and had eight sulfurs chelated to the central metal atom. In all, a series of five tetrakis complexes was studied, including the ligands dithiocarbamate (dtc), thioxanthate (txn), 1,1-dicyano-2,2-ethylenedithiolate (i-mnt), 1-cyano-1-carbethoxy-2,2-ethylenedithiolate (ced), and 1,1-dicarbethoxy-2,2-ethylenedithiolate (ded). The 4d orbitals were included on molybdenum, and the empty 3d levels on all sulfur atoms. The results show that the highest occupied molecular orbital in each case has over 90% metal d/sub xy/ character. Further, the energy of this orbital is linearly related to the reversible half-wave potentials for Mo(IV) ..-->.. Mo(V) and Mo(V) ..-->.. Mo(VI) oxidations of the complexes. A further irreversible oxidation observed experimentally also is closely related to the calculated energy levels. Relationships between the calculated results and Mo 3d/sub 5///sub 2/ X-ray photoelectron binding energies, EPR parameters, and charge-transfer absorption energies are discussed. Electrochemical and spectroscopic properties of these MoS/sub 8/ complexes can be understood in terms of a manifold of orbital energies that retain approximately constant spacings between one another and that move up or down in absolute energy in response to the charge donated or withdrawn by the ligands.

  5. Incorporation of neptunium(VI) into a uranyl selenite.

    PubMed

    Meredith, Nathan A; Polinski, Matthew J; Lin, Jian; Simonetti, Antonio; Albrecht-Schmitt, Thomas E

    2012-10-15

    The incorporation of neptunium(VI) into the layered uranyl selenite Cs[(UO(2))(HSeO(3))(SeO(3))] has yielded the highest level of neptunium uptake in a uranyl compound to date with an average of 12(卤3)% substitution of Np(VI) for U(VI). Furthermore, this is the first case in nearly 2 decades of dedicated incorporation studies in which the oxidation state of neptunium has been determined spectroscopically in a doped uranyl compound and also the first time in which neptunium incorporation has resulted in a structural transformation. PMID:23030830

  6. Coordination modes, spectral, thermal and biological evaluation of hetero-metal copper containing 2-thiouracil complexes.

    PubMed

    Masoud, Mamdouh S; Soayed, Amina A; El-Husseiny, Amel F

    2012-12-01

    Mononuclear copper complex [CuL(NH(3))(4)]Cl(2)0.5H(2)O and three new hetero-metallic complexes: [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2)6H(2)O] 2H(2)O(,) [Cu(3)Co(L)(4)8H2O]Cl4()5H(2)O, and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)3H(2)O]4H(2)O where L is 2-thiouracil, were prepared and characterized by elemental analyses, molar conductance, room-temperature magnetic susceptibility, spectral (IR, UV-Vis and ESR) studies and thermal analyses techniques (TG, DTG and DTA). The molar conductance data revealed that [CuL(NH(3))(4)]Cl(2)0.5H(2)O and [Cu(3)Co(L)(4)8H2O]Cl4.5H(2)O are electrolytes, while, [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2)6H(2)O]2H(2)O and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)3H(2)O]4H(2)O are non-electrolytes. IR spectra showed, that 2-thiouracil ligand behaves as a bidentate or tetradentate ligand. The geometry around the metal atoms is octahedral in all the prepared complexes except in [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)3H(2)O]4H(2)O complex where square planar environment around Co(II), Ni(II) and Cu(II) were suggested. Thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analyses under N(2) atmosphere. The decomposition course and steps were analyzed. The order of chemical reactions (n) was calculated via the peak symmetry method and the activation parameters of the non- isothermal decomposition were computed from the thermal decomposition data. The negative values of ?S(?) deduced the ordered structures of the prepared complexes compared to their starting reactants. The antimicrobial activity of the prepared complexes were screened in vitro against a Gram positive, a Gram negative bacteria, a filamentous fungi and a yeast. The antimicrobial screening data showed that the studied compounds exhibited a good level of activity against Escherichia coli, Staphylococcus aureus and Candida albicans but have no efficacy against Aspergillus flavus. It was observed that [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)3H(2)O]4H(2)O complex showed the most intensive activity against the tested microorganisms. Trials to prepare single crystals from complexes were failed. PMID:23026345

  7. Coordination modes, spectral, thermal and biological evaluation of hetero-metal copper containing 2-thiouracil complexes

    NASA Astrophysics Data System (ADS)

    Masoud, Mamdouh S.; Soayed, Amina A.; El-Husseiny, Amel F.

    2012-12-01

    Mononuclear copper complex [CuL(NH3)4]Cl20.5H2O and three new hetero-metallic complexes: [Cu2Ni(L)2(NH3)2Cl26H2O] 2H2O, [Cu3Co(L)48H2O]Cl򉕙H2O, and [Cu4Co2Ni(L)3(OH)4(NH3)Cl43H2O]4H2O where L is 2-thiouracil, were prepared and characterized by elemental analyses, molar conductance, room-temperature magnetic susceptibility, spectral (IR, UV-Vis and ESR) studies and thermal analyses techniques (TG, DTG and DTA). The molar conductance data revealed that [CuL(NH3)4]Cl20.5H2O and [Cu3Co(L)48H2O]Cl4.5H2O are electrolytes, while, [Cu2Ni(L)2(NH3)2Cl26H2O]2H2O and [Cu4Co2Ni(L)3(OH)4(NH3)Cl43H2O]4H2O are non-electrolytes. IR spectra showed, that 2-thiouracil ligand behaves as a bidentate or tetradentate ligand. The geometry around the metal atoms is octahedral in all the prepared complexes except in [Cu4Co2Ni(L)3(OH)4(NH3)Cl43H2O]4H2O complex where square planar environment around Co(II), Ni(II) and Cu(II) were suggested. Thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analyses under N2 atmosphere. The decomposition course and steps were analyzed. The order of chemical reactions (n) was calculated via the peak symmetry method and the activation parameters of the non- isothermal decomposition were computed from the thermal decomposition data. The negative values of ?S? deduced the ordered structures of the prepared complexes compared to their starting reactants. The antimicrobial activity of the prepared complexes were screened in vitro against a Gram positive, a Gram negative bacteria, a filamentous fungi and a yeast. The antimicrobial screening data showed that the studied compounds exhibited a good level of activity against Escherichia coli, Staphylococcus aureus and Candida albicans but have no efficacy against Aspergillus flavus. It was observed that [Cu4Co2Ni(L)3(OH)4(NH3)Cl43H2O]4H2O complex showed the most intensive activity against the tested microorganisms. Trials to prepare single crystals from complexes were failed.

  8. Controllable assemblies of Cd(II) supramolecular coordination complexes based on a versatile tripyridyltriazole ligand and halide/pseduohalide anions

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Guo, Wei; Guo, Ya-Mei

    2015-09-01

    Three Cd(II) complexes [Cd(L)(H2O)Cl2]n (1), [Cd(L)(H2O)Br2]n (2), and [Cd(L)I2]2 (3) have been assembled from CdX2 (1, X = Cl; 2, X = Br; 3, X = I) and a tripyridyltriazole ligand 3-(2-pyridyl)-4-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (L). Complexes 1 and 2 are isostructural and exhibit 1-D loop-like chain, while complex 3 has a distinct dimeric macrocyclic motif. Interestingly, another 1-D chain [Cd(L)I(SCN)]n (4) can be achieved when NH4SCN is introduced into the assembled system of 3. Structural analysis of 1-4 illustrates that the halide and thiocyanate anions in these coordination complexes behave as not only the counteranions, but also the structure directing agents. The fluorescent and thermal properties of 1-4 have also been investigated.

  9. Synthesis, Structure, and Photophysical Properties of Two Four-Coordinate Cu(I)-NHC Complexes with Efficient Delayed Fluorescence.

    PubMed

    Wang, Zhiqiang; Zheng, Caijun; Wang, Weizhou; Xu, Chen; Ji, Baoming; Zhang, Xiaohong

    2016-03-01

    Two luminescent cationic heteroleptic four-coordinate Cu(I) complexes supported by N-heterocyclic carbene ligand and diphosphine ligand were successfully prepared and characterized. These complexes adopt typical distorted tetrahedral configuration and have high stability in solid state. Quantum chemical calculations show carbene units have contributions to both highest occupied molecular orbitals and lowest unoccupied molecular orbitals of these Cu(I)-NHC complexes, the lowest-lying singlet and triplet excitations (S0 鈫 S1 and S0 鈫 T1) of [Cu(Pyim)(POP)](PF6) are dominated by metal-to-ligand charge transfer (MLCT) transition, while the S0 鈫 S1 and S0 鈫 T1 excitations of [Cu(Qbim)(POP)](PF6) are mainly MLCT and ligand-centered transitions, respectively. These Cu(I)-NHC complexes show efficient long-lifetime emissions (位em = 520 nm, 蟿 = 79.8 渭s, 桅 = 0.56 for [Cu(Pyim)(POP)](PF6), 位em = 570 nm, 蟿 = 31.97 渭s (78.99%) and 252.2 渭s (21.01%), 桅 = 0.35 for [Cu(Qbim)(POP)](PF6)) in solid state at room temperature, which are confirmed as delayed fluorescence by investigating the emissions at 77 K. PMID:26907724

  10. Novel tailoring reaction for two adjacent coordinated nitriles giving platinum 1,3,5-triazapentadiene complexes.

    PubMed

    Gushchin, Pavel V; Tyan, Marina R; Bokach, Nadezhda A; Revenco, Mikhail D; Haukka, Matti; Wang, Meng-Jiy; Lai, Cheng-Hsuan; Chou, Pi-Tai; Kukushkin, Vadim Yu

    2008-12-15

    The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl(2)(RCN)(2)] (R = Me, Et, CH(2)Ph, Ph) and [Pt(tmeda)(EtCN)(2)][SO(3)CF(3)](2) (8.(OTf)(2); tmeda = N,N,N',N'-tetramethylethylenediamine) upon their interplay with N,N'-diphenylguanidine (DPG; NH=C(NHPh)(2)), in a 1:2 molar ratio gives the 1,3,5-triazapentadiene complexes [PtCl(2){NHC(R)NHC(R)=NH}] (1-4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO(3)CF(3)](2) (10.(OTf)(2)), respectively. In contrast to the reaction of 8.(OTf)(2) with NH=C(NHPh)(2), interaction of 8.(OTf)(2) with excess gaseous NH(3) leads to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NH=C(NH(2))Et}(2)][SO(3)CF(3)](2) (9.(OTf)(2)). Treatment of trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) with 2 equiv of NH=C(NHPh)(2) in EtCN (R = Et) and CH(2)Cl(2) (R = CH(2)Ph, Ph) solutions at 20-25 degrees C leads to [PtCl{NH=C(R)NC(NHPh)=NPh}(RCN)] (11-13). When any of the trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG at prolonged reaction time (75 degrees C, 1-2 days), complexes containing two bidentate 1,3,5-triazapentadiene ligands, i.e. [Pt{NH=C(R)NC(NHPh)=NPh}(2)] (14-16), are formed. Complexes 14-16 exhibit strong phosphorescence in the solid state, with quantum yields (peak wavelengths) of 0.39 (530 nm), 0.61 (460 nm), and 0.74 (530 nm), respectively. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, in agreement with FAB-MS, ESI-MS, IR, and (1)H and (13)C{(1)H} NMR spectra. The structures of 1, 2, 4, 11, 13, 14, 9.(picrate)(2), and 10.(picrate)(2) were determined by single-crystal X-ray diffraction. PMID:18376821

  11. Chelate-Thiolate-Coordinate Ligands Modulating the Configuration and Electrochemical Property of Dinitrosyliron Complexes (DNICs).

    PubMed

    Yeh, Shih-Wey; Lin, Chih-Wei; Liu, Bai-Heng; Tsou, Chih-Chin; Tsai, Ming-Li; Liaw, Wen-Feng

    2015-11-01

    As opposed to the reversible redox reaction ({Fe(NO)2 }(10) reduced-form DNIC [(NO)2 Fe(S(CH2 )3 S)](2-) (1)?{Fe(NO)2 }(9) oxidized-form [(NO)2 Fe(S(CH2 )3 S)](-) ), the chemical oxidation of the {Fe(NO)2 }(10) DNIC [(NO)2 Fe(S(CH2 )2 S)](2-) (2) generates the dinuclear {Fe(NO)2 }(9) -{Fe(NO)2 }(9) complex [(NO)2 Fe(?-SC2 H4 S)2 Fe(NO)2 ](2-) (3) bridged by two terminal [SC2 H4 S](2-) ligands. On the basis of the Fe K-edge pre-edge energy and S K-edge XAS, the oxidation of complex 1 yielding [(NO)2 Fe(S(CH2 )3 S)](-) is predominantly a metal-based oxidation. The smaller S1-Fe1-S2 bond angle of 94.1(1) observed in complex 1 (S1-Fe1-S2 88.6(1) in complex 2), compared to the bigger bond angle of 100.9(1) in the {Fe(NO)2 }(9) DNIC [(NO)2 Fe(S(CH2 )3 S)](-) , may be ascribed to the electron-rich {Fe(NO)2 }(10) DNIC preferring a restricted bite angle to alleviate the electronic donation of the chelating thiolate to the electron-rich {Fe(NO)2 }(10) core. The extended transition state and natural orbitals for chemical valence (ETS-NOCV) analysis on the edt-/pdt-chelated {Fe(NO)2 }(9) and {Fe(NO)2 }(10) DNICs demonstrates how two key bonding interactions, that is, a Fe?S covalent ? bond and thiolate to the Fe d?z?2 charge donation, between the chelating thiolate ligand and the {Fe(NO)2 }(9/10) core could be modulated by the backbone lengths of the chelating thiolate ligands to tune the electrochemical redox potential (E1/2 =-1.64?V for complex 1 and E1/2 =-1.33?V for complex 2) and to dictate structural rearrangement/chemical transformations (S-Fe-S bite angle and monomeric vs. dimeric DNICs). PMID:26403796

  12. 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 卤 9.69, -3072.27 卤 4.76, and -6138.95 卤 12.24 kJ mol-1 for CaUP, HUP, and UP, respectively), and calorimetry data to calculate standard state enthalpies of formation of -3223.22 卤 4.00 and -7001.01 卤 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 卤 10.48 and -2893.12 卤 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.

  13. Fibre optic system for detection of uranyl ions in the solution phase

    NASA Astrophysics Data System (ADS)

    Hayes, Neil W.; Tremlett, Clare J.; Melfi, Patricia J.; Sessler, Jonathan D.; Shaw, Andrew M.

    2007-10-01

    Detection of radiological hazards in the solution phase using conventional means is considerably more difficult than in the gas phase. A new approach is required to provide a reliable, specific and low cost method of protecting sensitive national assets, such as water supplies, from a terrorist dirty bomb attack. Fibre optic sensors provide the required speed of response, the optical platforms are mature and of relatively low cost with proven reliability in the field. This paper describes the combination of a low cost sensor platform and smart sensor molecule (Isoamethyrin) for the selective determination of uranyl and other actinide species in water at sub ppm levels. Isoamethyrin is a synthetic porphyrin which has been demonstrated to show high selectivity for uranyl ions with an associated colour change on complexation. Fibre optic sensors are created by revealing an evanescent wave in a section of the fibre and covalently bonding the isoamethyrin to the fibre surface in this region. Colour changes occurring as a result of interaction between isoamethyrin and uranyl ions are monitored over 3 wavelength ranges covering the red, green and blue regions of the visible spectrum. Sensors created in this manner were found to be fast responding (<5s), sensitive (detection threshold <500ppb), specific (response restricted to certain actinides and lanthanides) and low cost.

  14. Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering

    USGS Publications Warehouse

    Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

    2006-01-01

    Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

  15. 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.; Rogers, R.D.

    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.

  16. An affinity-structure database of helix-turn-helix: DNA complexes with a universal coordinate system

    DOE PAGESBeta

    AlQuraishi, Mohammed; Tang, Shengdong; Xia, Xide

    2015-11-19

    Molecular interactions between proteins and DNA molecules underlie many cellular processes, including transcriptional regulation, chromosome replication, and nucleosome positioning. Computational analyses of protein-DNA interactions rely on experimental data characterizing known protein-DNA interactions structurally and biochemically. While many databases exist that contain either structural or biochemical data, few integrate these two data sources in a unified fashion. Such integration is becoming increasingly critical with the rapid growth of structural and biochemical data, and the emergence of algorithms that rely on the synthesis of multiple data types to derive computational models of molecular interactions. We have developed an integrated affinity-structure database inmore聽禄 which the experimental and quantitative DNA binding affinities of helix-turn-helix proteins are mapped onto the crystal structures of the corresponding protein-DNA complexes. This database provides access to: (i) protein-DNA structures, (ii) quantitative summaries of protein-DNA binding affinities using position weight matrices, and (iii) raw experimental data of protein-DNA binding instances. Critically, this database establishes a correspondence between experimental structural data and quantitative binding affinity data at the single basepair level. Furthermore, we present a novel alignment algorithm that structurally aligns the protein-DNA complexes in the database and creates a unified residue-level coordinate system for comparing the physico-chemical environments at the interface between complexes. Using this unified coordinate system, we compute the statistics of atomic interactions at the protein-DNA interface of helix-turn-helix proteins. We provide an interactive website for visualization, querying, and analyzing this database, and a downloadable version to facilitate programmatic analysis. Lastly, this database will facilitate the analysis of protein-DNA interactions and the development of programmatic computational methods that capitalize on integration of structural and biochemical datasets. The database can be accessed at http://ProteinDNA.hms.harvard.edu.芦聽less

  17. An affinity-structure database of helix-turn-helix: DNA complexes with a universal coordinate system

    SciTech Connect

    AlQuraishi, Mohammed; Tang, Shengdong; Xia, Xide

    2015-11-19

    Molecular interactions between proteins and DNA molecules underlie many cellular processes, including transcriptional regulation, chromosome replication, and nucleosome positioning. Computational analyses of protein-DNA interactions rely on experimental data characterizing known protein-DNA interactions structurally and biochemically. While many databases exist that contain either structural or biochemical data, few integrate these two data sources in a unified fashion. Such integration is becoming increasingly critical with the rapid growth of structural and biochemical data, and the emergence of algorithms that rely on the synthesis of multiple data types to derive computational models of molecular interactions. We have developed an integrated affinity-structure database in which the experimental and quantitative DNA binding affinities of helix-turn-helix proteins are mapped onto the crystal structures of the corresponding protein-DNA complexes. This database provides access to: (i) protein-DNA structures, (ii) quantitative summaries of protein-DNA binding affinities using position weight matrices, and (iii) raw experimental data of protein-DNA binding instances. Critically, this database establishes a correspondence between experimental structural data and quantitative binding affinity data at the single basepair level. Furthermore, we present a novel alignment algorithm that structurally aligns the protein-DNA complexes in the database and creates a unified residue-level coordinate system for comparing the physico-chemical environments at the interface between complexes. Using this unified coordinate system, we compute the statistics of atomic interactions at the protein-DNA interface of helix-turn-helix proteins. We provide an interactive website for visualization, querying, and analyzing this database, and a downloadable version to facilitate programmatic analysis. Lastly, this database will facilitate the analysis of protein-DNA interactions and the development of programmatic computational methods that capitalize on integration of structural and biochemical datasets. The database can be accessed at http://ProteinDNA.hms.harvard.edu.

  18. Cationic terminal gallylene complexes by halide abstraction: coordination chemistry of a valence isoelectronic analogue of CO and N2.

    PubMed

    Coombs, Natalie D; Vidovic, Dragoslav; Day, Joanna K; Thompson, Amber L; Le Pevelen, Delphine D; Stasch, Andreas; Clegg, William; Russo, Luca; Male, Louise; Hursthouse, Michael B; Willock, David J; Aldridge, Simon

    2008-11-26

    While N(2) and CO have played central roles in developing models of electronic structure, and their interactions with transition metals have been widely investigated, the valence isoelectronic diatomic molecules EX (E = group 13 element, X = group 17 element) have yet to be isolated under ambient conditions, either as the "free" molecule or as a ligand in a simple metal complex. As part of a program designed to address this deficiency, together with wider issues of the chemistry of cationic systems [L(n)M(ER)](+) (E = B, Al, Ga; R = aryl, amido, halide), we have targeted complexes of the type [L(n)M(GaX)](+). Halide abstraction is shown to be a viable method for the generation of mononuclear cationic complexes containing gallium donor ligands. The ability to isolate tractable two-coordinate products, however, is strongly dependent on the steric and electronic properties of the metal/ligand fragment. In the case of complexes containing ancillary pi-acceptor ligands such as CO, cationic complexes can only be isolated as base-trapped adducts, even with bulky aryl substituents at gallium. Base-free gallylene species such as [Cp*Fe(CO)(2)(GaMes)](+) can be identified only in the vapor phase by electrospray mass spectrometry experiments. With bis(phosphine) donor sets at the metal, the more favorable steric/electronic environment allows for the isolation of two-coordinate ligand systems, even with halide substituents at gallium. Thus, [Cp*Fe(dppe)(GaI)](+)[BAr(f)(4)](-) (9) can be synthesized and shown crystallographically to feature a terminally bound GaI ligand; 9 represents the first experimental realization of a complex containing a valence isoelectronic group 13/group 17 analogue of CO and N(2). DFT calculations reveal a relatively weakly bound GaI ligand, which is confirmed experimentally by the reaction of 9 with CO to give [Cp*Fe(dppe)(CO)](+)[BAr(f)(4)](-). In the absence of such reagents, 9 is stable for weeks in fluorobenzene solution, presumably reflecting (i) effective steric shielding of the gallium center by the ancillary phosphine and Cp* ligands; (ii) a net cationic charge which retards the tendency toward dimerization found for putative charge neutral systems; and (iii) (albeit relatively minor) population of the LUMOs of the GaI molecule through pi overlap with the HOMO and HOMO-2 of the [Cp*Fe(dppe)](+) fragment. PMID:18975947

  19. Coordinated aqua vs methanol substitution kinetics in fac-Re(I) tricarbonyl tropolonato complexes.

    PubMed

    Schutte, Marietjie; Roodt, Andreas; Visser, Hendrik G

    2012-11-01

    Water-soluble fac-[Re(CO)(3)(L,L'-Bid)(X)] (L,L'-Bid = tropolonato, X = H(2)O, methanol) complexes have been synthesized, and the aqua and methanol substitution reactions were investigated in water (pH range 6.3-10.0) and methanol, respectively, and compared. Thiocyanate ions were used as monodentate entering ligand. The complexes were characterized by UV-vis, IR, and NMR spectroscopy. The crystal structures of the complexes [NEt(4)] fac-[Re(Trop)(CO)(3)(H(2)O)].NO(3).H(2)O (reactant) and fac-[Re(CO)(3)(Trop)(Py)], a substitution product, are reported. Overall it was found that the aqua substitution of fac-[Re(CO)(3)(Trop)(H(2)O)] is about 10 times faster than the methanol substitution reaction for fac-[Re(CO)(3)(Trop)(MeOH)], with forward and reverse rate and stability constants [k(1) (M(-1) s(-1)), k(-1) (s(-1)), K(1), (M(-1))] for thiocyanate as monodentate entering ligand as follows: fac-[Re(CO)(3)(Trop)(H(2)O)] = 2.54 0.03, 0.0077 0.0005, 330 22/207 14 and fac-[Re(CO)(3)(Trop)(MeOH)] = 0.268 0.002, 0.0044 0.0002, (61 3)/(52 4). The activation parameters [?H()(k1) (kJ mol(-1)), ?S()(k1) (J K(-1) mol(-1))] for the aqua and methanol complex respectively are 56.1 0.7, -49 2 and 64 1, -43 5. PMID:23088314

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

    NASA Astrophysics Data System (ADS)

    Li, Xing; Zhao, Xiuhua; Bing, Yue; Zha, Meiqin; Xie, Hongzhen; Guo, Zhiyong

    2013-01-01

    Assembly reactions of 9,9-diethylfluorene-2,7-dicarboxylic acid (H2DFDC) and Mn(CH3COO)2路4H2O or MnCl2路4H2O by tuning of various secondary ligands such as 2,2'-bipyridine (2,2'-bpy), 4,4'-bipyridine (4,4'-bpy) or 1,3-bis(4-pyridyl)propane) (bpp), gave rise to four complexes {[Mn2(DFDC)2(DMF)2]路H2O}n (1), [Mn(DFDC)(2,2'-bpy)]n (2), {[Mn2(DFDC)2(4,4'-bpy)2]路2CH3OH}n (3), and {[Mn4(DFDC)4(bpp)2(CH3OH)3 (H2O)3]路3(CH3OH)路3(H2O)}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 H2DFDC ligands. Thermogravimetric analysis show that the complexes have remarkably high thermal stability. Magnetic susceptibility measurements have been finished and discussed for the complexes.

  1. Uranyl Solvation by a Three-Dimensional Reference Interaction Site Model.

    PubMed

    Matveev, Alexei; Li, Bo; R鰏ch, Notker

    2015-08-13

    We report an implementation of the three-dimensional reference interaction site model (3D RISM) that in particular addresses the treatment of the long-range Coulomb field of charged species, represented by point charges and/or a distributed charge density. A comparison of 1D and 3D results for atomic ions demonstrates a reasonable accuracy, even for a moderate size of the unit cell and a moderate grid resolution. In an application to uranyl complexes with 4-6 explicit aqua ligands and an implicit bulk solvent modeled by RISM, we show that the 3D technique is not susceptible to the deficiencies of the 1D technique exposed in our previous work [Li, Matveev, Kr黦er, R鰏ch, Comp. Theor. Chem. 2015, 1051, 151]. The 3D method eliminates the artificial superposition of explicit aqua ligands and the RISM medium and predicts essentially the same values for uranyl and uranyl-water bond lengths as a state-of-the-art polarizable continuum model. With the first solvation shell treated explicitly, the observables are nearly independent of the order of the closure relationship used when solving the set of integral equations for the various distribution functions. Furthermore, we calculated the activation barrier of water exchange with a hybrid approach that combines the 3D RISM model for the bulk aqueous solvent and a quantum mechanical description (at the level of electronic density functional theory) of uranyl interacting with explicitly represented water molecules. The calculated result agrees very well with experiment and the best theoretical estimates. PMID:26167741

  2. Spontaneous Partitioning of Californium from Curium: Curious Cases from the Crystallization of Curium Coordination Complexes

    SciTech Connect

    Cary, Samantha K.; Silver, Mark A.; Liu, Guokui; Wang, Jamie C.; Bogart, Justin A.; Stritzinger, Jared T.; Arico, Alexandra A.; Hanson, Kenneth; Schelter, Eric J.; Albrecht-Schmitt, Thomas E.

    2015-12-07

    The reaction of 248CmCl3 with excess 2,6-pyridinedicarboxylic acid (DPA) under mild solvothermal conditions results in crystallization of the tris-chelate complex Cm(HDPA)3路H2O. Approximately half of the curium remains in solution at the end of this process, and evaporation of the mother liquor results in crystallization of the bis-chelate complex [Cm(HDPA)- (H2DPA)(H2O)2Cl]Cl路2H2O. 248Cm is the daughter of the 伪 decay of 252Cf and is extracted in high purity from this parent. However, trace amounts of 249,250,251Cf are still present in all samples of 248Cm. During the crystallization of Cm(HDPA)3路H2O and [Cm(HDPA)(H2DPA)(H2O)2Cl]Cl路2H2O, californium(III) spontaneously separates itself from the curium complexes and is found doped within crystals of DPA in the form of Cf(HDPA)3. These results add to the growing body of evidence that the chemistry of californium is fundamentally different from that of earlier actinides.

  3. Spontaneous Partitioning of Californium from Curium: Curious Cases from the Crystallization of Curium Coordination Complexes.

    PubMed

    Cary, Samantha K; Silver, Mark A; Liu, Guokui; Wang, Jamie C; Bogart, Justin A; Stritzinger, Jared T; Arico, Alexandra A; Hanson, Kenneth; Schelter, Eric J; Albrecht-Schmitt, Thomas E

    2015-12-01

    The reaction of (248)CmCl3 with excess 2,6-pyridinedicarboxylic acid (DPA) under mild solvothermal conditions results in crystallization of the tris-chelate complex Cm(HDPA)3稨2O. Approximately half of the curium remains in solution at the end of this process, and evaporation of the mother liquor results in crystallization of the bis-chelate complex [Cm(HDPA)(H2DPA)(H2O)2Cl]Cl2H2O. (248)Cm is the daughter of the ? decay of (252)Cf and is extracted in high purity from this parent. However, trace amounts of (249,250,251)Cf are still present in all samples of (248)Cm. During the crystallization of Cm(HDPA)3稨2O and [Cm(HDPA)(H2DPA)(H2O)2Cl]Cl2H2O, californium(III) spontaneously separates itself from the curium complexes and is found doped within crystals of DPA in the form of Cf(HDPA)3. These results add to the growing body of evidence that the chemistry of californium is fundamentally different from that of earlier actinides. PMID:26562586

  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. Physical Interactions and Functional Coordination between the Core Subunits of Set1/Mll Complexes and the Reprogramming Factors

    PubMed Central

    Yang, Zhenhua; Augustin, Jonathan; Hu, Jing; Jiang, Hao

    2015-01-01

    Differentiated cells can be reprogrammed to the pluripotent state by overexpression of defined factors, and this process is profoundly influenced by epigenetic mechanisms including dynamic histone modifications. Changes in H3K4 methylation have been shown to be the predominant activating response in the early stage of cellular reprogramming. Mechanisms underlying such epigenetic priming, however, are not well understood. Here we show that the expression of the reprogramming factors (Yamanaka factors, Oct4, Sox2, Klf4 and Myc), especially Myc, directly promotes the expression of certain core subunits of the Set1/Mll family of H3K4 methyltransferase complexes. A dynamic recruitment of the Set1/Mll complexes largely, though not sufficiently in its own, explains the dynamics of the H3K4 methylation during cellular reprogramming. We then demonstrate that the core subunits of the Set1/Mll complexes physically interact with mainly Sox2 and Myc among the Yamanaka factors. We further show that Sox2 directly binds the Ash2l subunit in the Set1/Mll complexes and this binding is mediated by the HMG domain of Sox2. Functionally, we show that the Set1/Mll complex core subunits are required for efficient cellular reprogramming. We also show that Dpy30, one of the core subunits in the complexes, is required for the efficient target binding of the reprogramming factors. Interestingly, such requirement is not necessarily dependent on locus-specific H3K4 methylation. Our work provides a better understanding of how the reprogramming factors physically interact and functionally coordinate with a key group of epigenetic modulators to mediate transitions of the chromatin state involved in cellular reprogramming. PMID:26691508

  6. Solvent effect on the optical property of uranyl acetylacetonate monohydrate

    NASA Astrophysics Data System (ADS)

    Pradhan, Mukul; Basu, Mrinmoyee; Sarkar, Sougata; Sinha, Arun Kumar; Pal, Tarasankar

    2011-01-01

    The lability of the [UO 2(acac) 2H 2O] complex has been exploited to decipher solvent composition of a medium. Successive blue shift of the ?-?* band ( ?max = 282 nm) is observed due to alcohol substitution of increasing chain length in place of water. This observation helps to quantify the chain lengths of normal alcohol. The result has been accounted theoretically. However, in non-coordinating solvent, irregular red shift of the ?-?* band is observed because of the molecular complexity. Again, charge transfer (CT) band at 211 nm has been identified employing polar-polar and polar coordinating-non-coordinating solvent systems.

  7. Solvent effect on the optical property of uranyl acetylacetonate monohydrate.

    PubMed

    Pradhan, Mukul; Basu, Mrinmoyee; Sarkar, Sougata; Sinha, Arun Kumar; Pal, Tarasankar

    2011-01-01

    The lability of the [UO2(acac)2H2O] complex has been exploited to decipher solvent composition of a medium. Successive blue shift of the ?-?* band (?max=282 nm) is observed due to alcohol substitution of increasing chain length in place of water. This observation helps to quantify the chain lengths of normal alcohol. The result has been accounted theoretically. However, in non-coordinating solvent, irregular red shift of the ?-?* band is observed because of the molecular complexity. Again, charge transfer (CT) band at 211 nm has been identified employing polar-polar and polar coordinating-non-coordinating solvent systems. PMID:21030297

  8. Roles of Arabidopsis PARC6 in Coordination of the Chloroplast Division Complex and Negative Regulation of FtsZ Assembly.

    PubMed

    Zhang, Min; Chen, Cheng; Froehlich, John E; TerBush, Allan D; Osteryoung, Katherine W

    2016-01-01

    Chloroplast division is driven by the simultaneous constriction of the inner FtsZ ring (Z ring) and the outer DRP5B ring. The assembly and constriction of these rings in Arabidopsis (Arabidopsis thaliana) are coordinated partly through the inner envelope membrane protein ACCUMULATION AND REPLICATION OF CHLOROPLASTS6 (ARC6). Previously, we showed that PARC6 (PARALOG OF ARC6), also in the inner envelope membrane, negatively regulates FtsZ assembly and acts downstream of ARC6 to position the outer envelope membrane protein PLASTID DIVISION1 (PDV1), which functions together with its paralog PDV2 to recruit DYNAMIN-RELATED PROTEIN 5B (DRP5B) from a cytosolic pool to the outer envelope membrane. However, whether PARC6, like ARC6, also functions in coordination of the chloroplast division contractile complexes was unknown. Here, we report a detailed topological analysis of Arabidopsis PARC6, which shows that PARC6 has a single transmembrane domain and a topology resembling that of ARC6. The newly identified stromal region of PARC6 interacts not only with ARC3, a direct inhibitor of Z-ring assembly, but also with the Z-ring protein FtsZ2. Overexpression of PARC6 inhibits FtsZ assembly in Arabidopsis but not in a heterologous yeast system (Schizosaccharomyces pombe), suggesting that the negative regulation of FtsZ assembly by PARC6 is a consequence of its interaction with ARC3. A conserved carboxyl-terminal peptide in FtsZ2 mediates FtsZ2 interaction with both PARC6 and ARC6. Consistent with its role in the positioning of PDV1, the intermembrane space regions of PARC6 and PDV1 interact. These findings provide new insights into the functions of PARC6 and suggest that PARC6 coordinates the inner Z ring and outer DRP5B ring through interaction with FtsZ2 and PDV1 during chloroplast division. PMID:26527658

  9. Complexity in object manipulation by Japanese macaques (Macaca fuscata): a cross-sectional analysis of manual coordination in stone handling patterns.

    PubMed

    Leca, Jean-Baptiste; Gunst, No雔le; Huffman, Michael

    2011-02-01

    Defined as a spontaneous stone-directed noninstrumental manipulative behavior, and comprised of multiple one-handed and (a)symmetrical/(un)coordinated two-handed patterns, stone handling (SH) is a good candidate for the study of complexity in object manipulation. We present a cross-sectional developmental analysis of SH complexity in Japanese macaques (Macaca fuscata), through the combined investigation of bimanuality, coordination, and symmetry in hand use. Bimanual SH patterns were more frequent than unimanual patterns. Among bimanual patterns, coordinated actions were more frequent than uncoordinated ones. We recorded five asymmetrical coordinated SH patterns with manual role differentiation, a form of hand use reminiscent of complex actions involving the use of tools in monkeys and apes. Bimanuality in SH was affected by body posture. Aging individuals performed less bimanual and less coordinated SH patterns than younger individuals. Our result on senescent males performing less bimanual patterns than senescent females was consistent with sex differences found in the late deterioration of complex manual movements in other species. Although some SH patterns represent a high degree of behavioral complexity, our results suggest that SH behavior is not as complex as tool-use or tool-manufacture in other nonhuman primates and hominids. PMID:21244141

  10. 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.

  11. Cobalt Complexes Containing Pendant Amines in the Second Coordination Sphere as Electrocatalysts for H2 Production

    SciTech Connect

    Fang, Ming; Wiedner, Eric S.; Dougherty, William G.; Kassel, W. S.; Liu, Tianbiao L.; DuBois, Daniel L.; Bullock, R. Morris

    2014-10-27

    A series of heteroleptic 17e- cobalt complexes, [CpCoII(PtBu2NPh2)](BF4), [CpC6F5CoII(PtBu2NPh2)](BF4), [CpC5F4NCoII(PtBu2NPh2)](BF4), [where P2tBuN2Ph = 1,5-diphenyl-3,7-di(tert-butyl)-1,5-diaza-3,7-diphosphacyclooctane, CpC6F5 = C5H4(C6F5), and CpC5F4N = C5H4(C5F4N)] were synthesized, and structures of all three were determined by X-ray crystallography. Electrochemical studies showed that the CoIII/II couple of [CpC5F4NCoII(PtBu2NPh2)]+ appears 250 mV positive of the CoIII/II couple of [CpCoII(PtBu2NPh2)] as a result of the strongly electron-withdrawing perfluorpyridyl substituent on the Cp ring. Reduction of these paramagnetic CoII complexes by KC8 led to the diamagnetic 18e- complexes CpICo(PtBu2NPh2), CpC6F5CoI(PtBu2NPh2), CpC5F4NCoI(PtBu2NPh2), which were also characterized by crystallography. Protonation of these neutral CoI complexes led to the cobalt hydrides [CpCoIII(PtBu2NPh2)H](BF4), [CpC6F5CoIII(PtBu2NPh2)H](BF4), and [CpC5F4NCoIII(PtBu2NPh2)H](BF4). The cobalt hydride with the most electron-withdrawing Cp ligand, [CpC5F4NCoIII(PtBu2NPh2)H]+ is an electrocatalyst for production of H2 using 4-MeOC6H4NH3BF4 (pKaMeCN = 11.86) with a turnover frequency of 350 s-1 and an overpotential of 0.75 V. Experimental measurement of thermochemical data provided further insights into the thermodynamics of H2 elimination. 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.

  12. Trivalent scandium, yttrium and lanthanide complexes with thia-oxa and selena-oxa macrocycles and crown ether coordination.

    PubMed

    Champion, Martin J D; Farina, Paolo; Levason, William; Reid, Gillian

    2013-09-28

    Complexes of the oxa-thia macrocycles [18]aneO4S2, [15]aneO3S2 and the oxa-selena macrocycle [18]aneO4Se2 (L) of types [MCl2(L)]FeCl4 (M = Sc or Y) were prepared from [ScCl3(thf)3] or [YCl2(THF)5][YCl4(THF)2] and the ligand in anhydrous MeCN, using FeCl3 as a chloride abstractor. The [MI2(L)]I, [LaI3(L)] and [LuI2(L)]I have been prepared from the ligands and the appropriate anhydrous metal triiodide in MeCN. Complexes of type [LaI3(crown)] and [LuI2(crown)]I (crown = 18-crown-6, 15-crown-5) were made for comparison. Use of the metal iodide results in complexes with high solubility compared to the corresponding chlorides, although also with increased sensitivity to moisture. All complexes were characterised by microanalysis, IR, (1)H, (45)Sc and (77)Se NMR spectroscopy as appropriate. X-ray crystal structures are reported for [ScCl2([18]aneO4S2)][FeCl4], [ScI2([18]aneO4S2)]I, [YCl2(18-crown-6)]3[Y2Cl9], [YCl2([18]aneO4S2)][FeCl4], [LaI3(15-crown-5)], [LaI2(18-crown-6)(MeCN)]I, [LuI(18-crown-6)(MeCN)2]I2, [Lu(15-crown-5)(MeCN)2(OH2)]I3, [LaI3([18]aneO4S2)], [LaI([18]aneO4S2)(OH2)]I2, [LaI3([18]aneO4Se2)] and [LuI2([18]aneO4Se2)]I. In each complex all the neutral donor atoms of the macrocycles are coordinated to the metal centre, showing very rare examples of these oxophilic metal centres coordinated to thioether groups, and the first examples of coordinated selenoether donors. In some cases MeCN or adventitious water displaces halide ligands, but not the S/Se donors from La or Lu complexes. A complex of the oxa-tellura macrocycle [18]aneO4Te2, [ScCl2([18]aneO4Te2)][FeCl4] was isolated, but is unstable in MeCN solution, depositing elemental Te. YCl3 and 18-crown-6 produced [YCl2(18-crown-6)]3[Y2Cl9], the asymmetric unit of which contains two cations with a trans-YCl2 arrangement and a third with a cis-YCl2 group. PMID:23881475

  13. Synthesis of iridium and ruthenium complexes with (N,N), (N,O) and (O,O) coordinating bidentate ligands as potential anti-cancer agents.

    PubMed

    Lucas, Stephanie J; Lord, Rianne M; Wilson, Rachel L; Phillips, Roger M; Sridharan, Visuvanathar; McGowan, Patrick C

    2012-12-01

    Several Ru-arene and Ir-Cp* complexes have been prepared incorporating (N,N), (N,O) and (O,O) coordinating bidentate ligands and have been found to be active against both HT-29 and MCF-7 cell lines. By incorporating a biologically active ligand into a metal complex the anti-cancer activity is increased. PMID:23015068

  14. Uranyl phthalocyanines show promise in the treatment of brain tumors

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.

    1967-01-01

    Processes synthesize sulfonated and nonsulfonated uranyl phthalocyanines for application in neutron therapy of brain tumors. Tests indicate that the compounds are advantageous over the previously used boron and lithium compounds.

  15. Complex Coordination of Cell Plasticity by a PGC-1伪-controlled Transcriptional Network in Skeletal Muscle

    PubMed Central

    Kupr, Barbara; Handschin, Christoph

    2015-01-01

    Skeletal muscle cells exhibit an enormous plastic capacity in order to adapt to external stimuli. Even though our overall understanding of the molecular mechanisms that underlie phenotypic changes in skeletal muscle cells remains poor, several factors involved in the regulation and coordination of relevant transcriptional programs have been identified in recent years. For example, the peroxisome proliferator-activated receptor 纬 coactivator-1伪 (PGC-1伪) is a central regulatory nexus in the adaptation of muscle to endurance training. Intriguingly, PGC-1伪 integrates numerous signaling pathways and translates their activity into various transcriptional programs. This selectivity is in part controlled by differential expression of PGC-1伪 variants and post-translational modifications of the PGC-1伪 protein. PGC-1伪-controlled activation of transcriptional networks subsequently enables a spatio-temporal specification and hence allows a complex coordination of changes in metabolic and contractile properties, protein synthesis and degradation rates and other features of trained muscle. In this review, we discuss recent advances in our understanding of PGC-1伪-regulated skeletal muscle cell plasticity in health and disease. PMID:26617528

  16. 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, Jo鉶 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.

  17. Investigating CN- cleavage by three-coordinate M[N(R)Ar]3 complexes.

    PubMed

    Christian, Gemma; Stranger, Robert; Yates, Brian F; Cummins, Christopher C

    2008-01-21

    Three-coordinate Mo[N((t)Bu)Ar]3 binds cyanide to form the intermediate [Ar((t)Bu)N]3Mo-CN-Mo[N((t)Bu)Ar]3 but, unlike its N2 analogue which spontaneously cleaves dinitrogen, the C-N bond remains intact. DFT calculations on the model [NH2]3Mo/CN- system show that while the overall reaction is significantly exothermic, the final cleavage step is endothermic by at least 90 kJ mol(-1), accounting for why C-N bond cleavage is not observed experimentally. The situation is improved for the [H2N]3W/CN- system where the intermediate and products are closer in energy but not enough for CN- cleavage to be facile at room temperature. Additional calculations were undertaken on the mixed-metal [H2N]3Re+/CN- /W[NH2]3 and [H2N]3Re+/CN-/Ta[NH2]3 systems in which the metals ions were chosen to maximise the stability of the products on the basis of an earlier bond energy study. Although the reaction energetics for the [H2N]3Re+/CN /W[NH2]3 system are more favourable than those for the [H2N]3W/CN- system, the final C-N cleavage step is still endothermic by 32 kJ mol(-1) when symmetry constraints are relaxed. The resistance of these systems to C-N cleavage was examined by a bond decomposition analysis of [H2N]M-L1[triple bond]L2-M[NH2]3 intermediates for L1[triple bond]L2 = N2, CO and CN which showed that backbonding from the metal into the L1[triple bond]L2 pi* orbitals is significantly less for CN than for N2 or CO due to the negative charge on CN- which results in a large energy gap between the metal d(pi), and the pi* orbitals of CN-. This, combined with the very strong M-CN- interaction which stabilises the CN intermediate, makes C-N bond cleavage in these systems unfavourable even though the C[triple bond]N triple bond is not as strong as the bond in N2 or CO. PMID:18411843

  18. Metal Complexes of Pyridylphenylisocyanides and Pyridylethynylphenylisocyanides as Building Blocks for Coordination Polymers and Supramolecular Assemblies.

    PubMed

    Mayr, Andreas; Guo, Jianhua

    1999-03-01

    The isocyanides 3-(4-pyridylethynyl)phenylisocyanide, 3, 4-(4-pyridylethynyl)phenylisocyanide, 6, 2,6-diisopropyl-4-(4-pyridylethynyl)phenylisocyanide, 9, and 2,6-diisopropyl-4-(4-pyridyl)phenylisocyanide, 11, were prepared. With PdI(2) and PtI(2), these isocyanides form the complexes trans-[MI(2)(CNR)(2)], 12-19 (M = Pd, Pt; CNR = 3, 6, 9, 11). The previously prepared complex trans-[PdI(2)(CNC(5)H(4)N-3)(2)] and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)], 16, combine with copper bis(trifluoroacetylacetonate) in the ratio of 1:2 to form the adducts trans-[PdI(2)(CNC(5)H(4)N-3)(2)].2[Cu(tfacac)(2)].2CH(2)Cl(2), 20, and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)].2[Cu(tfacac)(2)], 21, respectively. The complexes trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)], 19 (M = Pd) and 20 (M = Pt), react with [Pd(SO(3)CF(3))(2)(dppp)] (dppp = bisdiphenylphosphinopropane) to form the molecular squares [Pd(dppp)(trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)](4)(SO(3)CF(3))(8), 22 (M = Pd) and 23 (M = Pt). The crystal structure of 20 has been determined by X-ray crystallography. 20: C(34)H(28)Cl(4)Cu(2)F(12)I(2)N(4)O(8)Pd, monoclinic space group, P2(1)/n (No. 14), a = 10.899(3) 脜, b = 13.903(1) 脜, c = 17.827(6) 脜, beta = 105.50(2) degrees, Z = 2, 2618 unique reflections, R = 0.093, R(w) = 0.091. PMID:11670864

  19. C and N Hybrid Coordination Derived Co-C-N Complex as a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction.

    PubMed

    Wang, Zhong-Li; Hao, Xian-Feng; Jiang, Zheng; Sun, Xue-Ping; Xu, Dan; Wang, Jun; Zhong, Hai-Xia; Meng, Fan-Lu; Zhang, Xin-Bo

    2015-12-01

    Development of an efficient hydrogen evolution reaction (HER) catalyst composed of earth-abundant elements is scientifically and technologically important for the water splitting associated with the conversion and storage of renewable energy. Herein we report a new class of Co-C-N complex bonded carbon (only 0.22 at% Co) for HER with a self-supported and three-dimensional porous structure that shows an unexpected catalytic activity with low overpotential (212 mV at 100 mA cm(-2)) and long-term stability, better than that of most traditional-metal catalysts. Experimental observations in combination with density functional theory calculations reveal that C and N hybrid coordination optimizes the charge distribution and enhances the electron transfer, which synergistically promotes the proton adsorption and reduction kinetics. PMID:26555852

  20. Low coordinate germanium(II) and tin(II) hydride complexes: efficient catalysts for the hydroboration of carbonyl compounds.

    PubMed

    Hadlington, Terrance J; Hermann, Markus; Frenking, Gernot; Jones, Cameron

    2014-02-26

    This study details the first use of well-defined low-valent p-block metal hydrides as catalysts in organic synthesis. That is, the bulky, two-coordinate germanium(II) and tin(II) hydride complexes, L()(H)M: (M = Ge or Sn, L() = -N(Ar())(SiPr(i)3), Ar() = C6H2{C(H)Ph2}2Pr(i)-2,6,4), are shown to act as efficient catalysts for the hydroboration (with HBpin, pin = pinacolato) of a variety of unactivated, and sometimes very bulky, carbonyl compounds. Catalyst loadings as low as 0.05 mol % are required to achieve quantitative conversions, with turnover frequencies in excess of 13?300 h(-1) in some cases. This activity rivals that of currently available catalysts used for such reactions. PMID:24524219

  1. Intriguing assembled structure and properties of a novel dinuclear nickel(II) complex with an axially coordinated azide and methanol

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryuta; Fuyuhiro, Akira; Hayami, Shinya; Inoue, Katsuya; Kawata, Satoshi

    2008-12-01

    A novel dinickel (II) complex [{Ni(N 3)(MeOH)} 2(?-bpypz) 2]2MeOH consisting of doubly bridged anionic 3,5-bis(2-pyridyl)pyrazolate (bpypz -) and axially coordinated azido ions and methanol molecules was prepared and structurally characterized by single crystal X-ray diffraction, IR, Raman, and UV-Vis spectroscopies. The crystal structure reveals that an interesting feature is the formation of a two-dimensional supramolecular network through the ?⋯? stacking and the hydrogen bonding interactions. Variable-temperature magnetic susceptibility measurement by using SQUID shows antiferromagnetic interaction between Ni(II) ions ( HHDVV = -2 JSNi1 SNi2, J = -22.6 cm -1, g = 2.20).

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

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

    PubMed

    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 Ru(II)(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

  4. 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

  5. Care Coordination for Children with Complex Special Health Care Needs: The Value of the Advanced Practice Nurse抯 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 nurse抯 (APN抯) 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

  6. Coordination of alkenes and alkynes to a cationic d(0) zirconocene alkoxide complex.

    PubMed

    Stoebenau, Edward J; Jordan, Richard F

    2003-03-19

    This paper describes the synthesis of base-free (C5R5)2Zr(OtBu)+ cations, the direct observation of nonchelated alkene and alkyne adducts of these cations, and studies of the thermodynamic and dynamic properties of these novel species. Reaction of %@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%ZrMe%@sb@%2%@sbx@%%@mx@% (Cp' = C5H4Me) with tert-butyl alcohol followed by [Ph3C][B(C6F5)4] in benzene yields [%@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%Zr%@/hd@%%@fn;(;vis;full;auto@%O%@ital@%%@ex@%t%@rsf@%%@exx@%%@/hd@%Bu%@fnx;);vis;full@%%@/hd@%%@mx@% ][B(C6F5)4] (1), which exists as %@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%Zr%@/hd@%%@fn;(;vis;full;auto@%O%@ital@%%@ex@%t%@rsf@%%@exx@%%@/hd@%Bu%@fnx;);vis;full@%%@/hd@%%@fn;(;vis;full;auto@%ClR%@fnx;);vis;full@%%@ex@%+%@exx@%%@mx@% solvent adducts in C6D5Cl and CD2Cl2 solutions. Addition of ligands L (L = ethylene, propylene, propyne, 2-butyne, CO, phenylacetylene, allene, 1-hexene, cis-2-butene) to 1 in CD2Cl2 at -89 degrees C results in reversible formation of %@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%Zr%@/hd@%%@fn;(;vis;full;auto@%O%@ital@%%@ex@%t%@rsf@%%@exx@%%@/hd@%Bu%@fnx;);vis;full@%%@/hd@%%@fn;(;vis;full;auto@%L%@fnx;);vis;full@%%@ex@%+%@exx@%%@mx@% adducts. NMR data for %@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%Zr%@/hd@%%@fn;(;vis;full;auto@%O%@ital@%%@ex@%t%@rsf@%%@exx@%%@/hd@%Bu%@fnx;);vis;full@%%@/hd@%%@fn;(;vis;full;auto@%H%@sb@%2%@sbx@%C=%@/bd@%CHMe%@fnx;);vis;full@%%@ex@%+%@exx@%%@mx@% (4) indicate that the propylene coordinates unsymmetrically and is polarized with positive charge buildup at Cint. Equilibrium constants, defined by Keq = [Zr-L][1]-1[L]-1, vary in the order CO > propyne > 2-butyne > phenylacetylene > ethylene > allene > propylene > 1-hexene > cis-2-butene > vinyl chloride. Loss of L from %@mt;sys@%Cp%@/xs;55;%lnwidth@%'%@/xs;63;(%lnwidth-x55)@%%@mh;-x63@%%@sb@%2%@sbx@%%@/hd@%Zr%@/hd@%%@fn;(;vis;full;auto@%O%@ital@%%@ex@%t%@rsf@%%@exx@%%@/hd@%Bu%@fnx;);vis;full@%%@/hd@%%@fn;(;vis;full;auto@%L%@fnx;);vis;full@%%@ex@%+%@exx@%%@mx@% to give 1 appears to proceed via associative displacement by CD2Cl2 in most cases. PMID:12630871

  7. The effect of uranyl nitrate on intestinal transfer of hexoses

    PubMed Central

    Newey, H.; Sanford, P. A.; Smyth, D. H.

    1966-01-01

    1. Uranyl nitrate in a concentration of 3 脳 10-4 M caused reduction in mucosal transfer of glucose but not of galactose nor 3-O-methyl-glucose by sacs of rat everted intestine. At this concentration uranyl nitrate had little effect on glucose metabolism (measured by glucose disappearance). 2. Uranyl nitrate in a concentration of 3 脳 10-3 M caused reduction in transfer of glucose, galactose, 3-O-methyl-glucose and fluid, and inhibited glucose metabolism. 3. Uranyl nitrate did not inhibit entry of glucose into the intestine under anaerobic conditions. 4. Glucose was found to inhibit or stimulate galactose transfer depending on the conditions. The inhibitory action is presumably by competition for a common carrier, whereas stimulation indicates that glucose metabolism can supply energy for galactose transfer. 5. It is suggested that there are two different routes for glucose in the cell, one of which is uranyl sensitive and not used by galactose, and the other is uranyl insensitive and shared by both hexoses. The implications of this are discussed in relation to transport and metabolism. PMID:5972151

  8. 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

  9. 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 d(xy)鈮 d(x(2)-y(2)) < d(xz) 鈮 d(yz) < d(z(2)), and the iron(II) complexes in this ligand field have the (d(xy), d(x(2)-y(2)))(3)(d(xz), d(yz))(2)(d(z(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(-)鈮 PMe3 < CH3(-) < Cl(-)鈮 C(SiMe3)3(-) < CN(-)鈮 SAr(Pr(i)6-) < Ar(Pr(i)4-) < Ar(Me6-)鈮 N3(-) < NCS(-)鈮 NCSe(-)鈮 NCBH3(-)鈮 MeCN 鈮 H2O 鈮 NH3 < NO3(-)鈮 THF 鈮 CO 鈮 N(SiMe2Ph)2(-)鈮 N(SiMePh2)2(-) < F(-)鈮 N(H)Ar(Pr(i)6-)鈮 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 蠂MT with the isotropic Heisenberg Hamiltonian, 膜 = -2J艤1路艤2 yields an antiferromagnetic exchange coupling constant, J, of -131(2) cm(-1). PMID:26006177

  10. Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS.

    PubMed

    Carrera, Flora; Marcos, Enrique S谩nchez; Merkling, Patrick J; Chaboy, Jes煤s; Mu帽oz-P谩ez, Adela

    2004-10-18

    Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring. PMID:15476367

  11. Yttrium and lanthanide complexes having a chiral phosphanylamide in the coordination sphere.

    PubMed

    Panda, Tarun K; Gamer, Michael T; Roesky, Peter W

    2006-01-23

    The chiral phosphanylamides {N(R-CHMePh)(PPh(2))}(-) and {N(S-CHMePh)(PPh(2))}(-) were introduced into rare earth chemistry. Transmetalation of the enantiomeric pure lithium compounds Li{N(R-CHMePh)(PPh(2))} (1a) and Li{N(S-CHMePh)(PPh(2))} (1b) with lanthanide bis(phosphinimino)methanide dichloride [{CH(PPh(2)NSiMe(3))(2)}LnCl(2)](2) in a 2:1 molar ratio in THF afforded the enantiomeric pure complexes [{CH(PPh(2)NSiMe(3))(2)}Ln(Cl){eta(2)-N(R-CHMePh)(PPh(2))}] (Ln = Er (2a), Yb (3a), Lu (4a)) and [{CH(PPh(2)NSiMe(3))(2)}Ln(Cl){eta(2)-N(S-CHMePh)(PPh(2))}] (Ln = Er (2b), Yb (3b), Lu (4b)). The solid-state structures of 2a and 3a,b were established by single-crystal X-ray diffraction. Attempts to synthesize compounds 3 in a one-pot reaction starting from K{CH(PPh(2)NSiMe(3))(2)}, YbCl(3), and 1 resulted in the lithium chloride incorporated complex [{(Me(3)SiNPPh(2))(2)CH}Yb(mu-Cl)(2)LiCl(THF)(2)] (5). In an alternative approach to give chiral rare earth compounds in a one-pot reaction 1a or 1b was reacted with LnCl(3) and K(2)C(8)H(8) to give the enantiomeric pure cyclooctatetraene compounds [{eta(2)-N(R-CHMePh)(PPh(2))}Ln(eta(8)-C(8)H(8))] (Ln = Y (6a), Er (7a), Yb (8)) and [{eta(2)-N(S-CHMePh)(PPh(2))}Ln(eta(8)-C(8)H(8))] (Ln = Y (6b), Er (7b)). The structures of 6a,b, 7a, and 8 were confirmed by single-crystal X-ray diffraction in the solid state. PMID:16411730

  12. Two mechanisms coordinate replication termination by the Escherichia coli Tus鈥揟er complex

    PubMed Central

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

    2015-01-01

    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鈥揟er complex. The T7 replisome was arrested at the non-permissive end of Tus鈥揟er 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鈥揟er 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

  13. 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

  14. Controlling Magnetism by Light in Nanoscaled Heterostructures of Cyanometallate Coordination Networks: the role of increased complexity

    NASA Astrophysics Data System (ADS)

    Meisel, Mark W.

    2013-03-01

    Nanometer-sized heterostructures of the Prussian blue analogues AjCok[Fe(CN)6]l . n H2O (Co-Fe PBA, with A = K, Rb) and RbaNib[Cr(CN)6]c . m H2O (Ni-Cr PBA) have been investigated, and new phenomena, not observed for the constituent bulk phases, have been observed.[2,3,4,5] A crucial aspect of the ability to photocontrol the persistent magnetism up to 70 K is the role of the strain coupling present at the interfaces between the nanoscaled regions of the constituents. Increasing the morphological complexity of the samples has the potential to provide materials possessing novel combinations of properties. In parallel, the interplay between long-range magnetic order and structural coherence is an important consideration in our attempts to design new systems. Open, unresolved issues will be discussed, and potential future paths will be sketched. Presentation is coauthored with Daniel R. Talham, UF Chemistry, and supported by NSF via DMR-1005581 (DRT), DMR-1202033 (MWM), and DMR-0654118 (NHMFL), by the UF Division of Sponsored Research, and by a Fulbright Scholar Research Award (MWM).

  15. Freeze-drying synthesis of an amorphous Zn(2+) complex and its transformation to a 2-D coordination framework in the solid state.

    PubMed

    Itakura, T; Horike, S; Inukai, M; Kitagawa, S

    2016-03-01

    An amorphous and metastable precursor for a Zn two-dimensional coordination framework was synthesised via freeze drying. The precursor comprises randomly packed discrete clusters of a Zn complex. The amorphous-to-crystalline framework transformation, which was triggered by the gentle application of heat or pressure, was accompanied by a change in the coordination geometry of the Zn(2+) ions from tetrahedral to octahedral symmetry. PMID:26523996

  16. Aqueous uranium(VI) complexes with acetic and succinic acid: speciation and structure revisited.

    PubMed

    Lucks, Christian; Rossberg, Andr茅; Tsushima, Satoru; Foerstendorf, Harald; Scheinost, Andreas C; Bernhard, Gert

    2012-11-19

    We employed density functional theory (DFT) calculations, and ultraviolet-visible (UV-vis), extended X-ray absorption fine-structure (EXAFS), and attenuated total reflection Fourier-transform infrared (IR) spectroscopy analyzed with iterative transformation factor analysis (ITFA) to determine the structures and the pH-speciation of aqueous acetate (ac) and succinate (suc) U(VI) complexes. In the acetate system, all spectroscopies confirm the thermodynamically predicted pH-speciation by Ahrland (1951), with the hydrated uranyl ion and a 1:1, a 1:2 and a 1:3 U(VI)-ac complex. In the succinate system, we identified a new 1:3 U(VI)-suc complex, in addition to the previously known 1:1 and 1:2 U(VI)-suc complexes, and determined the pH-speciation for all complexes. The IR spectra show absorption bands of the antisymmetric stretching mode of the uranyl mojety (蠀3(UO2)) at 949, 939, 924 cm(-1) and at 950, 938, 925 cm(-1) for the 1:1, 1:2 and 1:3 U(VI)-ac and U(VI)-suc complexes, respectively. IR absorption bands at 1535 and 1534 cm(-1) and at 1465 and 1462 cm(-1) are assigned to the antisymmetric 蠀3,as(COO) and symmetric 蠀3,s(COO) stretching mode of bidentately coordinated carboxylic groups in the U(VI)-ac and U(VI)-suc complexes. The assignment of the three IR bands (蠀3(UO2), 蠀3,as(COO), 蠀3,s(COO)) and the stoichiometry of the complexes is supported by DFT calculations. The UV-vis spectra of the equivalent U(VI)-ac and U(VI)-suc complexes are similar suggesting common structural features. Consistent with IR spectroscopy and DFT calculations, EXAFS showed a bidentate coordination of the carboxylic groups to the equatorial plane of the uranyl moiety for all uranyl ligand complexes except for the newly detected 1:3 U(VI)-suc complex, where two carboxylic groups coordinate bidentately and one carboxylic group coordinates monodentately. All 1:1 and 1:2 complexes have a U-Owater distance of 鈭2.36 脜, which is shorter than the U-Owater distance of 鈭2.40 脜 of the hydrated uranyl ion. For all complexes the U-Ocarboxyl distance of the bidentately coordinated carboxylic group is 鈭2.47 脜, while the monodentately coordinated carboxylic group of the 1:3 U(VI)-suc complex has a U-Ocarboxyl distance of 鈭2.36 脜, that is, similar to the short U-Owater distance in the 1:1 and 1:2 complexes. PMID:23110741

  17. Complexation of mercury(II) in soil organic matter: EXAFS evidence for linear two-coordination with reduced sulfur groups.

    PubMed

    Skyllberg, Ulf; Bloom, Paul R; Qian, Jin; Lin, Chung-Min; Bleam, William F

    2006-07-01

    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 that reduced organic sulfur (S) and oxygen/ nitrogen (O/N) groups are involved in the complexation of Hg(II) to humic substances extracted from organic soils. In this work, covering intact organic soils and extending to much lower concentrations of Hg than before, we show that Hg is complexed by two reduced organic S groups (likely thiols) at a distance of 2.33 A in a linear configuration. Furthermore, a third reduced S (likely an organic sulfide) was indicated to contribute with a weaker second shell attraction at a distance of 2.92-3.08 A. When all high-affinity S sites, corresponding to 20-30% of total reduced organic S, were saturated, a structure involving one carbonyl-O or amino-N at 2.07 A and one carboxyl-O at 2.84 A in the first shell, and two second shell C atoms at an average distance of 3.14 A, gave the best fit to data. Similar results were obtained for humic acid extracted from an organic wetland soil. We conclude that models that are in current use to describe the biogeochemistry of mercury and to calculate thermodynamic processes need to include a two-coordinated complexation of Hg(II) to reduced organic sulfur groups in NOM in soils and waters. PMID:16856732

  18. 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.

  19. Stereoselective formation of seven-coordinate titanium(IV) monomer and dimer complexes of ethylenebis(o-hydroxyphenyl)glycine.

    PubMed

    Guo, M; Sun, H; Bihari, S; Parkinson, J A; Gould, R O; Parsons, S; Sadler, P J

    2000-01-24

    Reactions between the antitumor agent titanocene dichloride (Cp2TiCl2) and the hexadentate ligand N,N'-ethylenebis-(o-hydroxyphenylglycine) (H4ehpg) have been investigated in aqueous solution and the solid state. The racemic ligands give crystals of the monomer [Ti(ehpg)(H2O)] x (11/3)H2O (1), while the meso ligand gives the oxo-bridged dimer [[Ti(Hehpg)(H2O)]2O] x 13H2O (2). Complex 1 crystallizes in the monoclinic space group C2/c with a = 24.149(4) A, b = 14.143(3) A, c = 19.487(3) A, beta = 105.371(13) degrees, V = 6417.7(19) A3, Z = 12, and R(F) = 0.0499 for 4,428 independent reflections having I > 2sigma(I), and contains seven-coordinate pentagonal-bipyramidal TiIV with two axial phenolate ligands (Ti-O, 1.869(2) A). The pentagonal plane contains the two N-atoms at 2.210(2) A, two carboxylate O-atoms at 2.061(2) A, and a water molecule (Ti-OH2, 2.091(3) A). Complex 2 crystallizes as an oxygen-bridged dimer in the triclinic space group P-1 with a = 12.521(6) A, b = 14.085(7) A, c = 16.635(8) A, alpha = 80.93(2) degrees beta = 69.23(2) degrees, gamma = 64.33(2) degrees , V = 2472(2) A3, Z = 4, and R(F) = 0.0580 for 5956 independent reflections having I > 2sigma(I). Each seven-coordinate, pentagonal-bipyramidal TiIV has a bridging oxide and a phenolate as axial ligands. The pentagonal plane donors are H2O, two carboxylate O-atoms, and two NH groups, which form H-bonds to O-atoms both in the same half-molecule (O...N, 2.93-3.13 A) and in the other half-molecule (O...N, 2.73-2.75 A); the second phenoxyl group of each Hehpg ligand is protonated and not coordinated to TiIV, but H-bonds to a nearby amine proton (O...N, 2.73-2.75 A) from the same ligand and to a nearby H2O (O...O, 2.68 A). In contrast to all previously reported crystalline metal-EHPG complexes containing racemic ligands, in which the N(S,S)C(R,R) or N(R,R)C(S,S) form is present, complex 1 unexpectedly contains the N(S,S)C(S,S) and N(R,R)C(R,R) forms. This is attributed to the presence of ring strain in seven-coordinate TiIV complexes. Moreover, the rac ligands selectively form crystals of monomeric 1, while the meso ligand selectively forms crystals of the dimer 2 (N(R,R)C(R,S) or N(S,S)C(S,R)). Complexes 1 and 2 exhibit phenolate-to-TiIV charge-transfer bands near 387 nm, and 2D NMR studies indicate that the structures of 1 and 2 in solution are similar to those in the solid state. Complex 1 is stable over the pH range 1.0-7.0, while 2 is stable only between pH 2.5 and pH 5.5. Cp2TiCl2 reacts with EHPG at pH* 7.0 to give complex 1 with a t 1/2 of ca. 50 min (298 K), but complex 2 was not formed at this pH* value. At pH* 3.7, the reaction is very slow: 1 forms with a half-life of ca. 2.5 d, and 2 after ca. 1 week at ambient temperature. The relevance of these data to the possible role of serum transferrin as a mediator for the delivery of TiIV to tumor cells is discussed. PMID:11272527

  20. Novel Mn(II)Mn(III)Mn(II) trinuclear complexes with carbohydrate bridges derived from seven-coordinate manganese(II) complexes with N-glycoside.

    PubMed

    Tanase, T; Tamakoshi, S; Doi, M; Mikuriya, M; Sakurai, H; Yano, S

    2000-02-21

    Reactions of MnX2.nH2O with tris(N-(D-mannosyl)-2-aminoethyl)amine ((D-Man)3-tren), which was formed from D-mannose and tris(2-aminoethyl)amine (tren) in situ, afforded colorless crystals of [Mn((D-Man)3-tren)]X2 (3a, X = Cl; 3b, X = Br; 3c, X = NO3; 3d, X = 1/2SO4). The similar reaction of MnSO4.5H2O with tris(N-(L-rhamnosyl)-2-aminoethyl)amine ((L-Rha)3-tren) gave [Mn((L-Rha)3-tren)]SO4 (4d), where L-rhamnose is 6-deoxy-L-mannose. The structures of 3b and 4d were determined by X-ray crystallography to have a seven-coordinate Mn(II) center ligated by the N-glycoside ligand, (aldose)3-tren, with a C3 helical structure. Three D-mannosyl residues of 3b are arranged in a delta(ob3) configuration around the metal, leading to formation of a cage-type sugar domain in which a water molecule is trapped. In 4d, three L-rhamnosyl moieties are in a delta(lel3) configuration to form a facially opened sugar domain on which a sulfate anion is capping through hydrogen bonding. These structures demonstrated that a configurational switch around the seven-coordinate manganese(II) center occurs depending on its counteranion. Reactions of 3a, 3b, and 4d with 0.5 equiv of Mn(II) salt in the presence of triethylamine yielded reddish orange crystals formulated as [[Mn((aldose)3-tren)]2Mn(H2O)X3.nH2O (5a, aldose = D-Man, X = Cl; 5b, aldose = D-Man, X = Br; 6d, aldose = L-Rha, X = 1/2SO4). The analogous trinuclear complexes 6a (aldose = L-Rha, X = Cl), 6b (aldose = L-Rha, X = Br), and 6c (aldose = L-Rha, X = NO3) were prepared by the one-pot reaction of Mn(II) salts with (L-Rha)3-tren without isolation of the intermediate Mn(II) complexes. X-ray crystallographic studies revealed that 5a, 5b, 6c, and 6d have a linearly ordered trimanganese core, Mn(II)Mn(III)Mn(II), bridged by two carbohydrate residues with Mn-Mn separations of 3.845(2)-3.919(4) A and Mn-Mn-Mn angles of 170.7(1)-173.81(7) degrees. The terminal Mn(II) atoms are seven-coordinate with a distorted mono-face-capped octahedral geometry ligated by the (aldose)3-tren ligand through three oxygen atoms of C-2 hydroxyl groups, three N-glycosidic nitrogen atoms, and a tertiary amino group. The central Mn(III) atoms are five-coordinate ligated by four oxygen atoms of carbohydrate residues in the (aldose)3-tren ligands and one water molecule, resulting in a square-pyramidal geometry. In the bridging part, a beta-aldopyranosyl unit with a chair conformation bridges the two Mn(II)Mn(III) ions with the C-2 mu-alkoxo group and with the C-1 N-glycosidic amino and the C-3 alkoxo groups coordinating to each metal center. These structures could be very useful information in relation to xylose isomerases which promote aldose-ketose isomerization by using divalent dimetal centers such as Mn2+, Mg2+, and Co2+. PMID:11272563

  1. Molecular dynamics simulations of the structure and thermodynamics of carrier-assisted uranyl ion extraction.

    PubMed

    Jayasinghe, Manori; Beck, Thomas L

    2009-08-27

    We present molecular dynamics simulations of interfaces relevant to the selective chemical extraction of uranyl ions from aqueous solution. These molecular-level simulations model ion transfer in the PUREX process and in synthetic, selective membranes. We first present simulations of water/oil interfaces modified by incorporation of tributyl phosphate (TBP) into the oil phase (hexane). A range of concentrations is examined, from a single TBP molecule to values close to those utilized in the PUREX process. The TBP molecules exhibit strong interfacial activity, and the interface broadens relative to the water/oil case with increasing TBP concentrations. Additional structural features, including radial distribution functions and orientational distributions, are examined to elucidate the molecular ordering at the interface; the interface structure changes substantially with increasing TBP concentration. Finally, free-energy profiles are computed for (1) a single TBP molecule and a single uranyl nitrate complex [UO2(NO3)2] across the water/oil interface and (2) a UO2(NO3)2.TBP2 complex across both water/oil and water/(oil+TBP) interfaces. The UO2(NO3)2 complex is strongly repelled from the water/oil interface, while the UO2(NO3)2.TBP2 complex exhibits interfacial activity that decreases with increasing TBP concentration. The UO2(NO3)2.TBP2 complex displays a net free-energy driving force for partitioning into the oil phase that increases with increasing TBP concentration. PMID:19845396

  2. Dinitrogen cleavage by three-coordinate molybdenum(III) complexes: Mechanistic and structural data

    SciTech Connect

    Laplaza, C.E.; Johnson, M.J.A.; Peters, J.C.; Odom, A.L.; Kim, E.; Cummins, C.C.; George, G.N.; Pickering, I.J.

    1996-09-11

    The synthesis and characterization of the complexes Mo[N(R)Ar]{sub 3} (R = C(CD{sub 3}){sub 2}CH{sub 3}, Ar = 3.5-C{sub 6}H{sub 3}Me{sub 2}), ({mu}-N{sub 2})[C@Mo[N(R)Ar]{sub 3}]C{sub 2}, ({mu}-{sup 15}N{sub 2})[C@Mo[N(R)Ar]{sub 3}]C{sub 2}, NMo[N(R)Ar]{sub 3}, {sup 15}NMo[N(R)Ar]{sub 3}, Mo[N(t-Bu)Ph]{sub 3}, ({mu}-N{sub 2})[C@Mo[N(t-Bu)Ph]{sub 3}]C{sub 2}, and NMo[N(t-Bu)Ph]{sub 3} are described. Temperature-dependent magnetic susceptibility data indicate a quartet ground state for Mo[N(R)Ar]{sub 3}. Single-crystal X-ray diffraction studies for Mo[N(R)Ar]{sub 3} and NMo[N(t-Bu)Ph]{sub 3} are described. Extended X-ray absorption fine structure (EXAFS) structural studies for Mo[N(R)Ar]{sub 3}({mu}-N{sub 2})[C@Mo[N(R)Ar]{sub 3}] RTBC{sub 2}, and NMo[N(R)Ar]{sub 3} are reported. Temperature-dependent kinetic data are given for the unimolecular fragmentation of ({mu}-N{sub 2})[C@Mo[N(R)Ar]{sub 3}]{sub 2} to 2 equiv of NMo[N(R)Ar]{sub 3} and for the fragmentation of ({mu}-{sup 15}N{sub 2})[C@Mo[N(R)Ar]{sub 3}]{sub 2} to 2 equiv of {sup 15}NMo[N(R)Ar]{sub 3}. The temperature dependence of the {sup 15}N{sub 2} isotope effect for the latter N{sub 2} cleavage process was fitted to a simple harmonic model, leading to a prediction for the difference in NN stretching frequencies for the two isotopomers. 35 refs., 14 figs., 2 tabs.

  3. Cdk1 coordinates timely activation of MKlp2 kinesin with relocation of the chromosome passenger complex for cytokinesis.

    PubMed

    Kitagawa, Mayumi; Fung, Suet Yin Sarah; Hameed, Umar Farook Shahul; Goto, Hidemasa; Inagaki, Masaki; Lee, Sang Hyun

    2014-04-10

    The chromosome passenger complex (CPC) must relocate from anaphase chromosomes to the cell equator for successful cytokinesis. Although this landmark event requires the mitotic kinesin MKlp2, the spatiotemporal mechanistic basis remains elusive. Here, we show that phosphoregulation of MKlp2 by the mitotic kinase Cdk1/cyclin B1 coordinates proper mitotic transition with CPC relocation. We identified multiple Cdk1/cyclin B1 phosphorylation sites within the stalk and C-terminal tail that inhibit microtubule binding and bundling, oligomerization/clustering, and chromosome targeting of MKlp2. Specifically, inhibition of these abilities by Cdk1/cyclin B1 phosphorylation is essential for proper early mitotic progression. Upon anaphase onset, however, reversal of Cdk1/cyclin B1 phosphorylation promotes MKlp2-CPC complex formation and relocates the CPC from anaphase chromosomes for successful cytokinesis. Thus, we propose that phosphoregulation of MKlp2 by Cdk1/cyclin B1 ensures that activation of MKlp2 kinesin and relocation of the CPC occur at the appropriate time and space for proper mitotic progression and genomic stability. PMID:24656812

  4. Adenomatous polyposis coli plays a key role, in vivo , in coordinating assembly of the neuronal nicotinic postsynaptic complex

    PubMed Central

    Rosenberg, Madelaine M.; Yang, Fang; Giovanni, Monica; Mohn, Jesse L.; Temburni, Murali K.; Jacob, Michele H.

    2008-01-01

    The neuronal nicotinic synapse plays a central role in normal cognitive and autonomic function. Molecular mechanisms that direct the assembly of this synapse remain poorly defined, however. We show here that adenomatous polyposis coli (APC) organizes a multi-molecular complex that is essential for targeting 伪3*nAChRs to synapses. APC interaction with microtubule plus-end binding protein EB1 is required for 伪3*nAChR surface membrane insertion and stabilization. APC brings together EB1, the key cytoskeletal regulators macrophin and IQGAP1, and 14-3-3 adapter protein at nicotinic synapses. 14-3-3, in turn, links the 伪3-subunit to APC. This multi-molecular APC complex stabilizes the local microtubule and F-actin cytoskeleton and links postsynaptic components to the cytoskeleton鈥攅ssential functions for controlling the molecular composition and stability of synapses. This work identifies macrophin, IQGAP1 and 14-3-3 as novel nicotinic synapse components and defines a new role for APC as an in vivo coordinator of nicotinic postsynaptic assembly in vertebrate neurons. PMID:18407517

  5. Analysis of unsaturated compounds by Ag+ coordination ionspray mass spectrometry: studies of the formation of the Ag+/lipid complex.

    PubMed

    Seal, Jennifer R; Havrilla, Christine M; Porter, Ned A; Hachey, David L

    2003-08-01

    Coordination ionspray mass spectrometry (CIS-MS) is a useful tool in the detection and identification of cholesterol ester and phospholipid hydroperoxides and diacyl peroxides. Extensive studies of a series of cholesterol esters using CIS-MS revealed the following: (1) Cholesterol esters with equal number of double bonds as the internal standard showed a linear relative response in the mass spectrometer while compounds with non-equal numbers of double bonds gave a nonlinear relative response. (2) Complex adducts containing cholesterol ester, silver ion, AgF, AgBF(4), and 2-propanoxide form when silver is in molar excess of cholesterol esters, reducing the [M + Ag](+) signal. (3) In a mixture of cholesterol esters where silver is limiting, Ch22:6 and Ch20:4 bind to silver at the expense of Ch18:2 and have a higher signal in the mass spectrometer. (4) In a mixture of cholesterol esters where silver concentration is twofold greater than total cholesterol ester concentration, Ch22:6 and Ch20:4 form large complex adducts more frequently than Ch18:2 and have a lower signal in the mass spectrometer. PMID:12892911

  6. Radical generating coordination complexes as tools for rapid and effective fragmentation and fluorescent labeling of nucleic acids for microchip hybridization.

    SciTech Connect

    Kelly, J. J.; Chernov, B. N.; Mirzabekov, A. D.; Bavykin, S. G.; Biochip Technology Center; Northwestern Univ.; Engelhardt Inst. of Molecular Biology

    2002-01-01

    DNA microchip technology is a rapid, high-throughput method for nucleic acid hybridization reactions. This technology requires random fragmentation and fluorescent labeling of target nucleic acids prior to hybridization. Radical-generating coordination complexes, such as 1,10-phenanthroline-Cu(II) (OP-Cu) and Fe(II)-EDTA (Fe-EDTA), have been commonly used as sequence nonspecific 'chemical nucleases' to introduce single-strand breaks in nucleic acids. Here we describe a new method based on these radical-generating complexes for random fragmentation and labeling of both single- and double-stranded forms of RNA and DNA. Nucleic acids labeled with the OP-Cu and the Fe-EDTA protocols revealed high hybridization specificity in hybridization with DNA microchips containing oligonucleotide probes selected for identification of 16S rRNA sequences of the Bacillus group microorganisms.We also demonstrated cDNA- and cRNA-labeling and fragmentation with this method. Both the OP-Cu and Fe-EDTA fragmentation and labeling procedures are quick and inexpensive compared to other commonly used methods. A column-based version of the described method does not require centrifugation and therefore is promising for the automation of sample preparations in DNA microchip technology as well as in other nucleic acid hybridization studies.

  7. Limited coordination number and competitive coordination in ammonia-water mixed-ligand complexes of monopositive metal ions as studied by the laser-ablation-molecular beam method: Experiment and simulation

    NASA Astrophysics Data System (ADS)

    Sato, Hiroyasu; Matsuzaki, Akiyoshi; Nishio, Satoru; Ito, Osamu; Furukawa, Koji; Kawasaki, Takashi

    1998-03-01

    Ammonia-water mixed-ligand complexes of monopositive metal ions M+ (M=Mg, Al, Mn, and Co) were prepared in the gas phase by reactions of metal ions laser-ablated from a metal substrate in vacuum with ammonia-water binary clusters in a molecular beam injected nearby [the laser-ablation-molecular beam (LAMB) method]. Relative abundances of M+(NH3)m(H2O)n are characterized by intensity gaps which indicate limited (typically 2 or 3) coordination (solvation) numbers in the first coordination (solvation) sphere. Three patterns of competitive coordination (solvation), i.e., selective, nonselective, and magic-number-like, are observed. The patterns are metal-specific and relatively independent of stagnation ratios of two component gases. The coordination numbers as judged from the intensity gaps remain the same throughout the stagnation ratios studied. A model simulation of the dynamic processes involved was made under simple-minded assumptions: (1) the ensemble of metal complex ions starting from the reaction region is characterized with a temperature Tstart (its value being taken as an adjustable parameter), (2) only evaporation of component ligands one by one occurs after metal complex ions start from the reaction region into the quadrupole, (3) activation energy of each evaporation step is determined by binding energy of the leaving ligand, and (4) temperature drop rate of complex ions per one microsecond is constant (its value being taken as an adjustable parameter). Such a simulation procedure is found successful in reproducing the positions of intensity gaps, together with the qualitative features of the metal-specific coordination (solvation) patterns observed.

  8. Magnetic anisotropy in Ni(II)-Y(III) binuclear complexes: on the importance of both the first coordination sphere of the Ni(II) ion and the Y(III) ion belonging to the second coordination sphere.

    PubMed

    Maurice, R閙i; Vendier, Laure; Costes, Jean-Pierre

    2011-11-01

    The synthesis of a new Ni(II)-Y(III) binuclear complex with a marked elongation axis in the first coordination sphere of the Ni(II) ion is presented. Its zero-field splitting (ZFS) is studied by means of magnetic data and state-of-the-art ab initio calculations. A good agreement between the experimental and theoretical ZFS parameter values is encountered, validating the whole approach. The magnetic anisotropy axes are extracted from the ab initio calculations, showing that the elongation axis around the Ni(II) ion corresponds to the hard axis of magnetization and that the sign of the axial D parameter is imposed by this axis. The Ni-Y axis is found to be an easy axis of magnetization, which is, however, not significant according to the sign of D. The already reported [(H(2)O)Ni(ovan)(2)(?-NO(3))Y(ovan)(NO(3))]稨(2)O (ovan = o-vanillin) complex is then revisited. In this case, the elongation axis in the Ni(II) coordination sphere is less marked and the ZFS is dominated by the effect of the Y(III) ion belonging to the second coordination sphere. As a consequence, the D parameter is negative and the low-temperature behavior is dominated by the Ni-Y easy axis of magnetization. A competition between the first coordination sphere of the Ni(II) ion and the electrostatic effect of the Y(III) ion belonging to the second coordination sphere is then evidenced in both complexes, and the positive and negative D parameters are then linked to the relative importance of both effects in each complex. PMID:21972822

  9. An eight-coordinate vanadium thiolate complex with charge delocalization between V(V)-thiolate and V(IV)-thiyl radical forms.

    PubMed

    Chang, Ya-Ho; Su, Chia-Ling; Wu, Ru-Rong; Liao, Ju-Hsiou; Liu, Yi-Hung; Hsu, Hua-Fen

    2011-04-20

    A six-coordinate oxovanadium(V) thiolate complex and an eight-coordinate non-oxovanadium thiolate complex, [PPh(4)][VO(PS3'')(OCH(3))] (1) and [NEt(4)][V(PS3'')(2)] (2) (PS3'' = P(C(6)H(3)-3-Me(3)Si-2-S)(3)(3-)), respectively, have been isolated and structurally characterized. The former belongs to a limited collection of oxovanadium(V) thiolate complexes. The latter has an unusual coordination number of eight. More importantly, its consensus electronic structure derived from its spectroscopic data should be considered as the resonance forms of V(V)-thiolate and V(IV)-thiyl radical species. This implies that V(IV)-thiyl radical can maintain a stable presence in biological systems. PMID:21438583

  10. Two-coordinate iron(I) complex [Fe{N(SiMe3)2}2](-) : synthesis, properties, and redox activity.

    PubMed

    Werncke, C Gunnar; Bunting, Philip C; Duhayon, Carine; Long, Jeffrey R; Bontemps, S閎astien; Sabo-Etienne, Sylviane

    2015-01-01

    First-row two-coordinate complexes are attracting much interest. Herein, we report the high-yield isolation of the linear two-coordinate iron(I) complex salt [K(L)][Fe{N(SiMe3 )2 }2 ] (L=18-crown-6 or crypt-222) through the reduction of either [Fe{N(SiMe3 )2 }2 ] or its three-coordinate phosphine adduct [Fe{N(SiMe3 )2 }2 (PCy3 )]. Detailed characterization is gained through X-ray diffraction, variable-temperature NMR spectroscopy, and magnetic susceptibility studies. One- and two-electron oxidation through reaction with I2 is further found to afford the corresponding iodo iron(II) and diiodo iron(III) complexes. PMID:25370700

  11. Coordination of uranium(VI) with N,N'-diethyl-N,N'-ditolyldipicolinamide

    NASA Astrophysics Data System (ADS)

    Lapka, J. L.; Paulenova, A.; Zakharov, L. N.; Alyapyshev, M. Yu; Babain, V. A.

    2010-03-01

    Structural analyses of uranyl complexes with isomers of N,N'-diethyl-N,N'-ditolyl-dipicolinamide were carried out using IR spectroscopy and single crystal x-ray diffraction. From these analyses it was determined that complexation takes place through coordination with the carbonyl and pyridine nitrogen moieties. The uranium-oxygen and uranium-nitrogen bond distances for Et(p)TDPA are U(1)-O(1): 2.394(3), U(1)-O(2): 2.460(3), U(1)-N(1): 2.661(3) and for Et(o)TDPA U(1)-O(1): 2.415(5), U(1)-O(2): 2.432(4), and U(1)-N(1): 2.647(5).

  12. The energy landscape of uranyl-peroxide species.

    PubMed

    Tiferet, Eitan; Gil, Adri脿; Bo, Carles; Shvareva, Tatiana Y; Nyman, May; Navrotsky, Alexandra

    2014-03-24

    Nanoscale uranyl peroxide clusters containing UO2(2+) groups bonded through peroxide bridges to form polynuclear molecular species (polyoxometalates) exist both in solution and in the solid state. There is an extensive family of clusters containing 28鈥卽ranium atoms (U28 clusters), with an encapsulated anion in the center, for example, [UO2(O2)(3-x)(OH)(x)(4-)], [Nb(O2)4(3-)], or [Ta(O2)4(3-)]. The negative charge of these clusters is balanced by alkali ions, both encapsulated, and located exterior to the cluster. The present study reports measurement of enthalpy of formation for two such U28 compounds, one of which is uranyl centered and the other is peroxotantalate centered. The [(Ta(O2)4]-centered U28 capsule is energetically more stable than the [(UO2)(O2)3]-centered capsule. These data, along with our prior studies on other uranyl-peroxide solids, are used to explore the energy landscape and define thermochemical trends in alkali-uranyl-peroxide systems. It was suggested that the energetic role of charge-balancing alkali ions and their electrostatic interactions with the negatively charged uranyl-peroxide species is the dominant factor in defining energetic stability. These experimental data were supported by DFT calculations, which agree that the [(Ta(O2)4]-centered U28 capsule is more stable than the uranyl-centered capsule. Moreover, the relative stability is controlled by the interactions of the encapsulated alkalis with the encapsulated anion. Thus, the role of alkali-anion interactions was shown to be important at all length scales of uranyl-peroxide species: in both comparing clusters to clusters; and clusters to monomers or extended solids. PMID:24604754

  13. Six, Seven or Eight Coordinate Fe(II) , Co(II) or Ni(II) Complexes of Amide-Appended Tetraazamacrocycles for ParaCEST Thermometry.

    PubMed

    Olatunde, Abiola O; Bond, Christopher J; Dorazio, Sarina J; Cox, Jordan M; Benedict, Jason B; Daddario, Michael D; Spernyak, Joseph A; Morrow, Janet R

    2015-12-01

    Fe(II) , Co(II) and Ni(II) complexes of two tetraazamacrocycles (1,4,8,11-tetrakis(carbamoylmethyl)-1,4,8,11-tetraazacyclotetradecane (L1) and 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (L2) show promise as paraCEST agents for registration of temperature (paraCEST=paramagnetic chemical exchange saturation transfer). The Fe(II) , Co(II) and Ni(II) complexes of L1 show up to four CEST peaks shifted ?112?ppm, whereas analogous complexes of L2 show only a single CEST peak at ?69?ppm. Comparison of the temperature coefficients (CT ) of the CEST peaks of [Co(L2)](2+) , [Fe(L2)](2+) , [Ni(L1)](2+) and [Co(L1)](2+) showed that a CEST peak of [Co(L1)](2+) gave the largest CT (-0.66?ppm?(o) C(-1) at 4.7?T). NMR spectral and CEST properties of these complexes correspond to coordination complex symmetry as shown by structural data. The [Ni(L1)](2+) and [Co(L1)](2+) complexes have a six-coordinate metal ion bound to the 1-, 4-amide oxygen atoms and four nitrogen atoms of the tetraazamacrocycle. The [Fe(L2)](2+) complex has an unusual eight-coordinate Fe(II) bound to four amide oxygen atoms and four macrocyclic nitrogen atoms. For [Co(L2)](2+) , one structure has seven-coordinate Co(II) with three bound amide pendents and a second structure has a six-coordinate Co(II) with two bound amide pendents. PMID:26494320

  14. Capped-tetrahedrally coordinated Fe(II) and Co(II) complexes using a "Click"-derived tripodal ligand: geometric and electronic structures.

    PubMed

    Schweinfurth, David; Demeshko, Serhiy; Khusniyarov, Marat M; Dechert, Sebastian; Gurram, Venkatanarayana; Buchmeiser, Michael R; Meyer, Franc; Sarkar, Biprajit

    2012-07-16

    The 'Click'-derived tripodal ligand tris[(1-benzyl-1H-1,2,3-triazole-4-yl)methyl]amine, tbta, was used to synthesize the complexes [Fe(tbta)Cl]BF(4), 1, and [Co(tbta)Cl]BF(4), 2. Both complexes were characterized by (1)H NMR spectroscopy and elemental analysis. Single-crystal X-ray structural determination of 2 shows a 4 + 1 coordination around the cobalt(II) center with a rather long bond between Co(II) and the central amine nitrogen atom of tbta. Such a coordination geometry is best described as capped tetrahedral. 1 and 2 are thus the first examples of pseudotetrahedral coordinated Fe(II) and Co(II) complexes with tbta. A combination of SQUID susceptometry, EPR spectroscopy, M鰏sbauer spectroscopy, and DFT calculations was used to elucidate the electronic structures of these complexes and determine the spin state of the metal center. Comparisons are made between the complexes presented here with related complexes of other ligands such as tris(2-pyridylmethyl)amine, tmpa, hydrotris(pyrazolyl) borate, Tp, and tris(2-(1-pyrazolyl)methyl)amine, amtp. 1 and 2 were tested as precatalysts for the homopolymerization of ethylene, and both complexes delivered distinctly different products in this reaction. Blind catalyst runs were carried out with the metal salts to prove the importance of the tripodal ligand for product formation. PMID:22731779

  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)昅eCN (3), [MnII(SMe2N4(2-QuinoPN))](PF6)昅eCN旹t2O (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)2旹t2O (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. Stable Four-Coordinate Guanidinatosilicon(IV) Complexes with SiN3El Skeletons (El = S, Se, Te) and Si=El Double Bonds.

    PubMed

    M點k, Felix M; Klo, Dorit; Baus, Johannes A; Burschka, Christian; Bertermann, R黡iger; Poater, Jordi; Fonseca Guerra, C閘ia; Bickelhaupt, F Matthias; Tacke, Reinhold

    2015-09-28

    To get information about the reactivity profile of the donor-stabilized guanidinatosilicon(II) complexes 2 and 3, a series of oxidative addition reactions was studied. Treatment of 2 and 3 with S8, Se, or Te afforded the respective four-coordinate silicon(IV) complexes 8-10 and 12-14, which contain an SiN3 El skeleton (El = S, Se, Te) with an Si=El double bond. Treatment of 2 with N2O yielded the dinuclear four-coordinate silicon(IV) complex 11 with an SiN3O skeleton and a central four-membered Si2O2 ring. Compounds 8-14 exist both in the solid state and in solution. They were characterized by elemental analyses, NMR spectroscopic studies in the solid state and in solution, and crystal structure analyses. The reactivity profile of 2 was compared with that of the structurally related bis[N,N'-diisopropylbenzamidinato(-)]silicon(II) (1), which is three-coordinate in the solid state and four-coordinate in solution (1'). In contrast, as shown by state-of-the-art relativistic DFT analyses and experimental studies, silylene 2 is three-coordinate both in the solid state and solution. The three-coordinate species 2 is 9.3?kcal?mol(-1) more stable in benzene than the four-coordinate isomer 2'. The reason for this was studied by bonding analyses of 2 and 2', which were compared with those of 1 and 1'. The gas-phase proton affinities of the relevant species in solution (1' and 2) amount to 288.8 and 273.8?kcal?mol(-1), respectively. PMID:26284318

  17. Two new copper(II) complexes with the shortest (N N) diazine based rigid ligand: Example of unusual tridentate coordination mode

    NASA Astrophysics Data System (ADS)

    Karmakar, Ruma; Choudhury, Chirantan Roy; Batten, Stuart R.; Mitra, Samiran

    2007-01-01

    Two new five coordinated Cu(II) complexes, Cu(L)Cl 2,CH 3OH ( 1) and Cu(L)Br 2 ( 2) derived from the flexidentate ligand (L), 2-pyridinealdazine, have been synthesised and characterised by spectroscopic and electrochemical studies. Single crystal structures of the complexes were determined. Crystal structures of both the complexes contain monomeric entities of five coordinated copper(II) ions where the Schiff base ligand, 2-pyridinealdazine, acts in a tridentate fashion. The central part of the ligand in complex 2 is disordered over two positions: N8 sbnd N9 make up the major position and N8A sbnd N9A make up the minor position.

  18. Crystal structures of copper(II) complexes of 2-formylpyridine substituted thiosemicarbazones; the first example of a coordinated thiosemicarbazone with a thiol function

    NASA Astrophysics Data System (ADS)

    West, D. X.; Swearingen, J. K.; Romack, T. J.; Billeh, I. S.; Jasinski, J. P.; Li, Y.; Staples, R. J.

    2001-08-01

    The crystal structures of two 5-coordinate copper(II) complexes containing neutral, tridentate 2-formylpyridine N(4)-substituted thiosemicarbazones have been determined. 2-Formylpyridine N(4)-cyclohexylthiosemicarbazone, HFo4CHex coordinates via the pyridine nitrogen, imine nitrogen and thione sulfur with two chloro ligands to produce [Cu(HFo4CHex)Cl 2]. Similarly, 2-formylpyridine 3-(4-methylpiperazine)thiosemicarbazone, HFoppz4M, produces [Cu(HFoppz4M)Cl 2] with one major difference; rather than the expected thione form of the thiosemicarbazone moiety, it coordinates as the thiol isomer. Both complexes are close to a square pyramid structure with axial and equatorial chloro ligands and the thiosemicarbazone moieties of both ligands nearly planar. Also included is the crystal structure of N-cyclohexylthiosemicarbazide, CHextsc.

  19. Photochemical Reduction of Low Concentrations of CO2 in a Porous Coordination Polymer with a Ruthenium(II)-CO Complex.

    PubMed

    Kajiwara, Takashi; Fujii, Machiko; Tsujimoto, Masahiko; Kobayashi, Katsuaki; Higuchi, Masakazu; Tanaka, Koji; Kitagawa, Susumu

    2016-02-01

    Direct use of low pressures of CO2 as a C1 source without concentration from gas mixtures is of great interest from an energy-saving viewpoint. Porous heterogeneous catalysts containing both adsorption and catalytically active sites are promising candidates for such applications. Here, we report a porous coordination polymer (PCP)-based catalyst, PCP-Ru(II) composite, bearing a Ru(II) -CO complex active for CO2 reduction. The PCP-Ru(II) composite showed improved CO2 adsorption behavior at ambient temperature. In the photochemical reduction of CO2 the PCP-Ru(II) composite produced CO, HCOOH, and H2 . Catalytic activity was comparable with the corresponding homogeneous Ru(II) catalyst and ranks among the highest of known PCP-based catalysts. Furthermore, catalytic activity was maintained even under a 5鈥% CO2 /Ar gas mixture, revealing a synergistic effect between the adsorption and catalytically active sites within the PCP-Ru(II) composite. PMID:26800222

  20. Tetrapositive plutonium, neptunium, uranium, and thorium coordination complexes: chemistry revealed by electron transfer and collision induced dissociation.

    PubMed

    Gong, Yu; Tian, Guoxin; Rao, Linfeng; Gibson, John K

    2014-04-17

    The Pu(4+), Np(4+), and U(4+) ions, which have large electron affinities of 鈭34.6, 鈭33.6, and 鈭32.6 eV, respectively, were stabilized from solution to the gas phase upon coordination by three neutral tetramethyl-3-oxa-glutaramide ligands (TMOGA). Both collision induced dissociation (CID) and electron transfer dissociation (ETD) of Pu(TMOGA)3(4+) reveal the propensity for reduction of Pu(IV) to Pu(III), by loss of TMOGA(+) in CID and by simple electron transfer in ETD. The reduction of Pu(IV) is in distinct contrast to retention of Th(IV) in both CID and ETD of Th(TMOGA)3(4+), where only the C-Oether bond cleavage product was observed. U(TMOGA)3(4+) behaves similarly to Th(TMOGA)3(4+) upon CID and ETD, while the fragmentation patterns of Np(TMOGA)3(4+) lie between those of Pu(TMOGA)3(4+) and U(TMOGA)3(4+). It is notable that the gas-phase fragmentation behaviors of these exceptional tetrapositive complexes parallel fundamental differences in condensed phase chemistry within the actinide series, specifically the tendency for reduction from the IV to III oxidation states. PMID:24660979

  1. Complexity and coordination of root growth at low water potentials: recent advances from transcriptomic and proteomic analyses.

    PubMed

    Yamaguchi, Mineo; Sharp, Robert E

    2010-04-01

    Progress in understanding root growth regulation and adaptation under water-stressed conditions is reviewed, with emphasis on recent advances from transcriptomic and proteomic analyses of maize and soybean primary roots. In both systems, kinematic characterization of the spatial patterns of cell expansion within the root elongation zone showed that at low water potentials, elongation rates are preferentially maintained towards the root apex but are progressively inhibited at more basal locations resulting in a shortened growth zone. This characterization provided an essential foundation for extensive research into the physiological mechanisms of growth regulation in the maize primary root at low water potentials. Recently, these studies were expanded to include transcriptomic and cell wall proteomic analyses of the maize primary root, and a proteomic analysis of total soluble proteins in the soybean primary root. This review focuses on findings related to protection from oxidative damage, the potential roles of increased apoplastic reactive oxygen species in regulation of wall extension properties and other processes, region-specific phenylpropanoid metabolism as related to accumulation of (iso)flavonoids and wall phenolics and amino acid metabolism. The results provide novel insights into the complexity and coordination of the processes involved in root growth at low water potentials. PMID:19895398

  2. Metal coordination study at Ag and Cd sites in crown thioether complexes through DFT calculations and hyperfine parameters.

    PubMed

    do Nascimento, Rafael R; Lima, Filipe C D A; Gon鏰lves, Marcos B; Errico, Leonardo A; Renter韆, Mario; Petrilli, Helena M

    2015-04-01

    Structural and electronic properties of [C12H24S6X], [C13H26S6OX], and [C14H28S6OX] (X: Ag(+), Cd(2+)) crown thioether complexes were investigated within the framework of the density functional theory (DFT) using the projector augmented wave (PAW) method. The theoretical results were compared with time-differential perturbed ?-? angular correlations (TDPAC) experiments reported in the literature using the (111)Ag?(111)Cd probe. In the case of X=Ag(+), a refinement of the structure was performed and the predicted equilibrium structures compared with available X-ray diffraction experimental data. Structural distortions induced by replacing Ag(+) with Cd(2+) were investigated as well as the electric-field gradient (EFG) tensor at the Cd(2+) sites. Our results suggest that the EFG at Cd(2+) sites corresponds to the Ag(+) coordination sphere structure, i.e., before the structural relaxations of the molecule with X=Cd(2+) are completed. The results are discussed in terms of the characteristics of the TDPAC (111)Ag?(111)Cd probe and the time window of the measurement, and provide an interesting tool with which to probe molecular relaxations. PMID:25814377

  3. The intra-annular acylamide chelate-coordinated compound: The keto-tautomer of metal (II) milrinone complex

    NASA Astrophysics Data System (ADS)

    Gong, Yun; Liu, Jinzhi; Tang, Wang; Hu, Changwen

    2008-03-01

    In the presence of N, N'-dimethyllformamide (DMF), two isostructural metal (II)-milrinone complexes formulated as M(C 12H 8N 3O) 2 (M = Co 1 and Ni 2) have been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. The two compounds crystallize in the tetragonal system, chiral space group P4 32 12. They exhibit similar two dimensional (2D) square grid-like framework, in which milrinone acts as a ditopic ligand with its terminal pyridine and intra-annular acylamide groups covalently bridging different metal centers. The intra-annular acylamide ligand shows a chelate-coordinated mode. Compounds 1 and 2 are stable under 200 癈. Compound 3 formulated as (C 12H 9N 3O) 4稨 2O was obtained in the presence of water, the water molecule in the structure leads to the racemization of compound 3 and it crystallizes in the monoclinic system, non-chiral space group P2 1/ c. Milrinone exhibits a keto-form in the three compounds and compounds 1- 3 exhibit different photoluminescence properties.

  4. Coordinated control of senescence by lncRNA and a novel T-box3 co-repressor complex

    PubMed Central

    Kumar P, Pavan; Emechebe, Uchenna; Smith, Richard; Franklin, Sarah; Moore, Barry; Yandell, Mark; Lessnick, Stephen L; Moon, Anne M

    2014-01-01

    Cellular senescence is a crucial tumor suppressor mechanism. We discovered a CAPER?/TBX3 repressor complex required to prevent senescence in primary cells and mouse embryos. Critical, previously unknown roles for CAPER? in controlling cell proliferation are manifest in an obligatory interaction with TBX3 to regulate chromatin structure and repress transcription of CDKN2A-p16INK and the RB pathway. The IncRNA UCA1 is a direct target of CAPER?/TBX3 repression whose overexpression is sufficient to induce senescence. In proliferating cells, we found that hnRNPA1 binds and destabilizes CDKN2A-p16INK mRNA whereas during senescence, UCA1 sequesters hnRNPA1 and thus stabilizes CDKN2A-p16INK. Thus CAPER?/TBX3 and UCA1 constitute a coordinated, reinforcing mechanism to regulate both CDKN2A-p16INK transcription and mRNA stability. Dissociation of the CAPER?/TBX3 co-repressor during oncogenic stress activates UCA1, revealing a novel mechanism for oncogene-induced senescence. Our elucidation of CAPER? and UCA1 functions in vivo provides new insights into senescence induction, and the oncogenic and developmental properties of TBX3. DOI: http://dx.doi.org/10.7554/eLife.02805.001 PMID:24876127

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

    SciTech Connect

    Murphy, William M.

    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)

  6. 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.

  7. Protic Ruthenium Tris(pyrazol-3-ylmethyl)amine Complexes Featuring a Hydrogen-Bonding Network in the Second Coordination Sphere.

    PubMed

    Yamagishi, Hiroaki; Nabeya, Shohei; Ikariya, Takao; Kuwata, Shigeki

    2015-12-21

    We synthesized ruthenium complexes bearing a tris(pyrazol-3-ylmethyl)amine ligand LH3 and revealed that this tripodal ligand allows predictable accumulation of three proton-delivering NH groups around a coordination site. The Br鴑sted acidity of the NH groups in LH3 led to the formation of multiple hydrogen bonds with the substrate ligand and deprotonation. The chlorido complex ligated by LH3 catalyzed disproportionation of 1,2-diphenylhydrazine. PMID:26619341

  8. Synthesis and crystal structures of two coordination polymers and a binuclear cadmium(II) complex containing 3- and 4-aminobenzoate ligands.

    PubMed

    Zhou, Dong-Mei; Zhao, Xiao-Lan; Liu, Feng-Yi; Kou, Jun-Feng

    2015-08-01

    Due to their wide range of coordination modes and versatile conformations when binding to metal atoms, multicarboxylate ligands are of interest in the design of metal-organic frameworks (MOFs). Three Cd(II) complexes, namely catena-poly[diammonium [[chloridocadmium(II)]-di-?-chlorido-[chloridocadmium(II)]-bis(?-3-aminobenzoato)-?(3)N:O,O';?(3)O,O':N

  9. ESI-MS and theoretical study on the coordination structures and reaction modes of the diperoxovanadate complexes containing histidine-like ligands

    NASA Astrophysics Data System (ADS)

    Yu, Xian-Yong; Xu, Xin; Chen, Zhong

    2008-01-01

    In order to study the coordination structures and the reaction modes of diperoxovanadate complexes in the gas phase, the interaction between K3[OV(O2)2(C2O4)]路H2O and a series of histidine-like ligands has been investigated by the combination of the electrospray ionization-mass spectrometry (ESI-MS) and the density functional theory (DFT) calculations. The experimental results proved the formation of both [OV(O2)2L]- (L = all histidine-like ligands) and [OV(O2)2L'2]- (L' = histidine and carnosine only) species. DFT calculations at the level of B3LYP/6-31+G* showed that [OV(O2)2L'2]- is a hexa-coordinated complex, instead of a hepta-coordinated complex as proposed before. The unique coordination mode in the gas phase is for one ligand to bind to the oxygen atoms via hydrogen binding, rather than both ligands to the metal center. The L'2 dimer formation and the maintenance of the hydrogen bonding within the dimer during the complex formation are two important factors that enhance the abundance of the [OV(O2)2L'2]- species. The calculated bonding enthalpy and free energy changes provided an explanation on the reaction modes of the interaction systems, in agreement with the observations of the ESI-MS experiments.

  10. Solvothermal synthesis of uranium(VI) phases with aromatic carboxylate ligands: A dinuclear complex with 4-hydroxybenzoic acid and a 3D framework with terephthalic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Yingjie; Karatchevtseva, Inna; Bhadbhade, Mohan; Tran, Toan Trong; Aharonovich, Igor; Fanna, Daniel J.; Shepherd, Nicholas D.; Lu, Kim; Li, Feng; Lumpkin, Gregory R.

    2016-02-01

    With the coordination of dimethylformamide (DMF), two new uranium(VI) complexes with either 4-hydroxybenzoic acid (H2phb) or terephthalic acid (H2tph) have been synthesized under solvothermal conditions and structurally characterized. [(UO2)2(Hphb)2(phb)(DMF)(H2O)3]路4H2O (1) has a dinuclear structure constructed with both pentagonal and hexagonal bipyramidal uranium polyhedra linked through a 渭2-bridging ligand via both chelating carboxylate arm and alcohol oxygen bonding, first observation of such a coordination mode of 4-hydroxybenzoate for 5 f ions. [(UO2)(tph)(DMF)] (2) has a three-dimensional (3D) framework built with pentagonal bipyramidal uranium polyhedra linked with 渭4-terephthalate ligands. The 3D channeled structure is facilitated by the unique carboxylate bonding with nearly linear C-O-U angles and the coordination of DMF molecules. The presence of phb ligands in different coordination modes, uranyl ions in diverse environments and DMF in complex 1, and tph ligand, DMF and uranyl ion in complex 2 has been confirmed by Raman spectroscopy. In addition, their thermal stability and photoluminescence properties have been investigated.

  11. 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鈥

  12. 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

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

    SciTech Connect

    Sigmon, Ginger E.; Burns, Peter C.

    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 脜, 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.

  14. Uranyl peroxide enhanced nuclear fuel corrosion in seawater

    PubMed Central

    Armstrong, Christopher R.; Nyman, May; Shvareva, Tatiana; Sigmon, Ginger E.; Burns, Peter C.; Navrotsky, Alexandra

    2012-01-01

    The Fukushima-Daiichi nuclear accident brought together compromised irradiated fuel and large amounts of seawater in a high radiation field. Based on newly acquired thermochemical data for a series of uranyl peroxide compounds containing charge-balancing alkali cations, here we show that nanoscale cage clusters containing as many as 60 uranyl ions, bonded through peroxide and hydroxide bridges, are likely to form in solution or as precipitates under such conditions. These species will enhance the corrosion of the damaged fuel and, being thermodynamically stable and kinetically persistent in the absence of peroxide, they can potentially transport uranium over long distances. PMID:22308442

  15. First examples of ternary lanthanide 5-aminoisophthalate complexes: Hydrothermal syntheses and structures of lanthanide coordination polymers with 5-aminoisophthalate and oxalate

    NASA Astrophysics Data System (ADS)

    Liu, Chong-Bo; Wen, Hui-Liang; Tan, Sheng-Shui; Yi, Xiu-Guang

    2008-05-01

    Two new lanthanide coordination polymers with mixed-carboxylates, [Ln(OX)(HAPA)(H 2O)] n[Ln = Eu ( 1), Ho ( 2); H 2APA = 5-aminoisophthalic acid; OX = oxalate] were obtained by hydrothermal reactions, and characterized by single crystal X-ray diffraction, elemental analysis and IR spectra. Complexes 1 and 2 are both 3-D supramolecular structure, in which lanthanide ions are bridged by oxalate and 5-aminoisophthalate ligands forming 2-D metal-organic framework, and 2-D networks are further architectured to form 3-D supramolecular structures by hydrogen bonds. The two carboxylate groups of H 2APA ligand are all deprotonated and exhibit chelating and bridging bidentate coordination modes, respectively, and the amino group in HAPA presents - NH3+ in the titled complexes. The thermogravimetric analysis was carried out to examine the thermal stability of the titled complexes. And the photoluminescence property of 1 was investigated.

  16. The investigation of the solvent effect on coordination of nicotinato ligand with cobalt(II) complex containing tris(2-benzimidazolylmethyl)amine: A computational study

    NASA Astrophysics Data System (ADS)

    Sayin, Koray; Karaka艧, Duran

    2014-11-01

    The electronic structure of [Co(ntb)(nic)]+ complex ion are optimized by using density functional theory (DFT) method with mix basis set. Where (ntb) represents tris(2-benzimidazolylmethyl)amine ligand and (nic) is the anion of nicotinic acids. Six different fields, vacuum, chloroform, butanonitrile, methanol, water and formamide solvents are used in these calculations. The calculated structural parameters indicate that (nic) ligand coordinates to cobalt(II) containing (ntb) ligand with one oxygen atom in butanonitrile, methanol, water and formamide solvents but coordinates with two oxygen atoms in vacuum. These results are supported with IR, UV and 1H NMR spectra. According to the calculated results, the geometry of [Co(ntb)(nic)]+ complex ion is distorted octahedral in vacuum while the geometry is distorted square pyramidal in the all other solvents. Distorted octahedral [Co(ntb)(nic)]+ complex ion have not been synthesized as experimentally and it is predicted with computational chemistry methods.

  17. Exploration of various electronic properties along the reaction coordinate for hydration of Pt(II) and Ru(II) complexes; the CCSD, MPx, and DFT computational study.

    PubMed

    Burda, Jaroslav V; Futera, Zden?k; Chval, Zden?k

    2013-12-01

    In the study behavior of molecular electrostatic potential, averaged local ionization energy, and reaction electronic flux along the reaction coordinate of hydration process of three representative Ru(II) and Pt(II) complexes were explored using both post-HF and DFT quantum chemical approximations. Previously determined reaction mechanisms were explored by more detailed insight into changes of electronic properties using ?B97XD functional and MP2 method with 6-311++G(2df,2pd) basis set and CCSD/6-31(+)G(d,p) approach. The dependences of all examined properties on reaction coordinate give more detailed understanding of the hydration process. PMID:24126826

  18. Molecular tectonics: homochiral coordination networks based on combinations of a chiral neutral tecton with Hg(II), Cu(II) or Ni(II) neutral complexes as metallatectons.

    PubMed

    Larpent, Patrick; Jouaiti, Abdelaziz; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2014-02-01

    The use of compound 1 as an enantiomerically pure neutral and rigid organic linear tecton bearing two divergently oriented monodentate coordinating sites appended with two chiral centres of the same (S) configuration leads, in the presence of neutral metal complexes behaving either as a linear (Cu(hfac)2, Cu(OAc)2) or a V-shaped (HgCl2) 2-connecting node or a 4-connecting square node (NiCl2), to the formation of four homochiral 1- and 2-D coordination polymers. PMID:24276523

  19. 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.

  20. Adsorption of Uranyl on Gibbsite: A Time-Resolved Laser-Induced Fluorescence Spectroscopy Study

    SciTech Connect

    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 E, and half-width of the vibronic lines W. 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, while species C was hypothesized to correspond to electrostatically bound uranyl complexes (predominantly [UO2(OH)3]-).

  1. Dissimilar alterations of sodium-coupled uptake by platinum-coordination complexes in renal proximal tubular cells in primary culture.

    PubMed

    Courjault-Gautier, F; Hoet, D; Leroy, D; Toutain, H J

    1994-09-01

    The potent anticancer drug cis-diamminedichloroplatinum (II) (CDDP) interferes early with electrolyte transport by the renal proximal tubule. To study the early effects of platinum coordination complexes on apical Na(+)-coupled transport systems, we examined the effect of increasing concentrations of CDDP, trans-diamminedichloroplatinum (II) (TDDP) and cis-diammine-1,1-cyclobutane-dicarboxylate platinum (II) (CBDCA) on Na(+)-coupled uptake of P(i), methyl-alpha-D-glucopyranoside (MGP) and L-alanine by rabbit proximal tubule cells in primary culture. At 17 microM CDDP and 540 microM CBDCA, 1) cell viability (lactate dehydrogenase release) and ATP content were unaffected, 2) Na(+)-K(+)-ATPase activity was reduced by 40%, 3) Na(+)-coupled uptake of MGP and P(i) was reduced, whereas 4) Na(+)-coupled uptake of alanine rose to twice the control value. Alterations of Na(+)-coupled uptake of P(i), MGP and alanine were due to changes in Km, with no significant change in Vmax. At 333 microM TDDP, Na(+)-dependent P(i) and MGP uptake decreased, whereas Na(+)-independent uptake increased markedly and was associated with a decline in cell viability and ATP content. We conclude that 1) the TDDP-induced decrease in Na+/P(i) and Na+/glucose cotransport was associated with reduced cell viability, 2) both CDDP and CBDCA had different effects on Na+/P(i), Na+/glucose and Na+/alanine cotransport, arguing against an alteration of the Na+ gradient due to reduced Na(+)-K(+)-ATPase activity and 3) CBDCA induced alterations of Na(+)-coupled uptake similar to those of CDDP at concentrations 20 to 30 times higher.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7932157

  2. Long-term safety evaluation of a novel oxygen-coordinated niacin-bound chromium (III) complex.

    PubMed

    Shara, Michael; Kincaid, Anthony E; Limpach, Aimee L; Sandstrom, Robert; Barrett, Laura; Norton, Neil; Bramble, J D; Yasmin, Taharat; Tran, Janet; Chatterjee, Archana; Bagchi, Manashi; Bagchi, Debasis

    2007-07-01

    Chromium (III) is an essential micronutrient required for normal protein, fat and carbohydrate metabolism, as well as helps insulin metabolize fat, turn protein into muscle and convert sugar into energy. A broad spectrum of research investigations including in vitro, in vivo and clinical studies demonstrated the beneficial effects of novel oxygen- coordinated niacin-bound chromium (III) complex (NBC) in promoting glucose-insulin sensitivity, lipid profile, cardioprotective ability and lean body mass. This study examined the long-term safety of NBC by orally administering either 0 or 25 ppm or the human equivalency dose of 1000 microg elemental chromium (III) as NBC per day for 52 consecutive weeks to male and female Sprague-Dawley rats. Animals of each group and each gender were sacrificed on 26, 39, or 52 weeks of treatment. Body weight, physical and ocular health, feed and water intake, selected organ weights as such and as a percentage of liver and brain weight, hepatic lipid peroxidation and DNA fragmentation, hematology and clinical chemistry, and histopathological evaluations were conducted. At 26, 39, or 52 weeks of treatment, body weight gain was significantly reduced by 7.7%, 8.1% and 14.9% in male rats, and 5.5%, 11.4% and 9.6% in female rats, respectively, in the NBC treatment groups. No significant changes were observed in hepatic lipid peroxidation and DNA fragmentation, hematology and clinical chemistry, and histopathological evaluation between control and NBC groups at these time points. These findings, thus far, are in agreement with the subchronic studies in terms of the safety of NBC. PMID:17555823

  3. On-line coordination in complex goal-directed movements: a matter of interactions between several loops.

    PubMed

    Fautrelle, Lilian; Bonnetblanc, Fran鏾is

    2012-10-01

    Motor flexibility is the ability to rapidly modify behavior when unexpected perturbations occur. In goal directed movements, this process may be involved during the motor execution itself, by using on-line motor corrections, or off-line, on a trial-by-trial basis. A consensus has emerged to describe and unify these two dependant processes within the framework of the internal models theory in which the cerebellum is involved in error processing. However, this general framework may be incomplete to describe on-line motor corrections when complex motor coordination is involved in the task. In particular, interaction torques existing between different effectors limit the independence between different controllers that could be considered to control various body parts. In addition, recent findings suggest that different (sub)-cortical loops may be involved during orienting responses to visual stimuli but also during on-line motor corrections following visual perturbations. The way these different loops with different dynamics interact but achieve the same motor goal is an important problem in motor control. The simplest organization may be sequential, as in the well-known stretch reflex. This implies that during on-line corrections, the nervous system may be involved in a distributed fashion and that motor plans and synergies depend both on anatomical and temporal constraints. More particularly, motor plans and synergies may be stored and may differ according to the (sub)-cortical loops involved during the whole on-line correction process. Finally, questions concerning the independence (or not) of these loops remain unanswered. The case of strict independence would mean that between the various corrective loops, (i) error processing and (ii) motor plans/synergies would be different. By contrast, in a situation of dependency, it would probably mean that interactions would link lower (and faster) to upper (and longer) loops by informing these latter of the motor corrections sent by the former, similarly to an efference copy. PMID:22814096

  4. Yttrium and lanthanide complexes with various P,N ligands in the coordination sphere: synthesis, structure, and polymerization studies.

    PubMed

    Gamer, Michael T; Rast鋞ter, Marcus; Roesky, Peter W; Steffens, Alexandra; Glanz, Mario

    2005-05-01

    Yttrium and lanthanide complexes with different P,N ligands in the coordination sphere have been synthesized. First the chloride complexes [{CH(PPh2NSiMe3)2}Ln{(Ph2P)2N}Cl] (Ln = Y (1 a), La (1 b), Nd (1 c), Yb (1 d)) having the bulky [CH(PPh2NSiMe3)2]- and the flexible [(Ph2P)2N]- ligands in the same molecule were prepared by three different synthetic pathways. Compounds 1 a-d can be obtained by reaction of [{[CH(PPh2NSiMe3)2]LnCl2}2] with [K(thf)nN(PPh2)2] (n = 1.25, 1.5) or by treatment of [{(Ph2P)2N}LnCl2(thf)3] with K[CH(PPh2NSiMe3)2]. Furthermore, a one-pot reaction of K[CH(PPh2NSiMe3)2] with LnCl3 and [K(thf)nN(PPh2)2] leads to the same products. Single-crystal X-ray structures of 1 a-d show that the conformation of the six-membered metallacycle (N1-P1-C1-P2-N2-Ln) which is formed by chelation of the [CH(PPh2NSiMe3)2]- ligand to the lanthanide atom is influenced by the ionic radius of the central metal atom. In solution dynamic behavior of the [(Ph2P)2N]- ligand is observed, which is caused by rapid exchange of the two different phosphorus atoms. Further reaction of 1 b with KNPh2 resulted in [{(Me3SiNPPh2)2CH}La{N(PPh2)2}(NPh2)] (2). Compounds 1 a-d and 2 are active in the ring-opening polymerization of epsilon-caprolactone and the polymerization of methyl methacrylate. In some cases high molecular weight polymers with good conversions and narrow polydispersities were obtained. In both polymerizations the catalytic activity depends on the ionic radius of the metal center. PMID:15779014

  5. The metal complexes of amino acids and their N-substituted derivatives鈥擵I. The physical properties, i.r. spectra and normal coordinate analysis of bivalent metal complexes with DL-threonine

    NASA Astrophysics Data System (ADS)

    Inomata, Yoshie; Takeuchi, Toshio; Moriwaki, Takao

    Complexes of five bivalent metals with DL-threonine have been prepared and characterized by means of i.r. absorption, powder diffuse reflection, and electronic spectra, X-ray diffraction and magnetic susceptibility. The complexes appear to be of three distinct types. The first type includes ML 2路 nH 2O (M = Ni, Cu, Zn; L = DL-threoninato anion), in which the ligand chelates metal ions through the nitrogen atom and the oxygen atom of the carboxylato group. Three species of copper(II) complexes have been prepared. They seem to be two trans forms and one cis form. MnCl 2(HL) 4路H 2O is a second type in which the metal is coordinated through the oxygen atom of the carboxyl group and chloride ions, but is not coordinated through the nitrogen atom. 2CdCl 2路HL路HCl路2H 2O is a third type, in which the metal is coordinated through only chloride ions. In order to assign the observed frequencies of i.r. absorption spectra in detail, a normal coordinate analysis has been accomplished for the complexes of the first type as a 33-body problem. Copper(II) and zinc(II) complexes with L-threonine have been prepared for comparison.

  6. Higher coordinate gold(I) complexes with the weak Lewis base tri(4-fluorophenyl) phosphine. Synthesis, structural, luminescence, and DFT studies

    NASA Astrophysics Data System (ADS)

    Agbeworvi, George; Assefa, Zerihun; Sykora, Richard E.; Taylor, Jared; Crawford, Carlos

    2016-03-01

    The structures and spectroscopic properties of two high coordinate gold(I) phosphine complexes with the TFFPP=tri(4-fluorophenyl)phosphine ligand are reported. Synthesis in a 1:3 metal to ligand ratio provided the compound [AuCl(TFFPP)3] (2) that crystallize in the P 1 bar space group, where the asymmetric unit consists of three independent molecules. In all three sites, two sets of bond angles display distinctly different ranges. The three P-Au-P angles have average values of 117.92掳, 117.57掳, and 114.78掳 for sites A, B, and C, with the corresponding P-Au-Cl angles of 98.31掳, 99.05掳, and 103.38掳, respectively. The chloride ion coordinates as the fourth ligand, at the corresponding Au-Cl distance of 2.7337, 2.6825, and 2.6951聽脜 for the three sites. This distance is longer by 0.40-0.45聽脜 than the Au-Cl distance found in the mono TFFPP complex 1 (2.285聽脜) indicating a weakening of the Au-Cl interaction as the coordination number increases. In compound 3, [Au(TFFPP)3]Cl路陆CH2Cl2路H2O, the structure consists of three phosphine ligands bound to the gold(I) atom, but the Cl- exists as uncoordinated counter anion. The structural differences observed in the two complexes are attributable to crystal-packing effects caused by the introduction of H-bonding as well as enhanced intra and inter-molecular 蟺-interaction in 3. The photoluminescence of the complexes compared with that of the ligand show ligand centered emission perturbed by the metal coordination. Theoretical DFT studies conducted on these complexes supports assignments of the electronic transitions observed in these systems.

  7. Uranyl tungstate and zirconium tungstate in salt melts

    SciTech Connect

    Kryukova, A.I.; Bragina, R.A.; Kazantsev, G.N.; Korshunov, I.A.

    1988-05-01

    The article discusses the preparation, properties, and behavior of uranyl tungstate and zirconium tungstate in salt melts. Procedures for their preparation are presented. The radiographic and IR spectroscopic characteristics, the thermal stability, and solubility and stability in chloride-tungstate melts of different composition have been studied.

  8. Structure and dynamics of aqueous solution of uranyl ions

    SciTech Connect

    Chopra, Manish; Choudhury, Niharendu

    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.

  9. Substrate binding preferences and pKa determinations of a nitrile hydratase model complex: Variable solvent coordination to [(bmmp-TASN)Fe]OTf

    PubMed Central

    O扵oole, Martin G.; Bennett, Brian; Mashuta, Mark S.; Grapperhaus, Craig A.

    2009-01-01

    The five-coordinate iron-dithiolate complex (N,N?-4,7-bis-(2?-methyl-2?-mercatopropyl)-1-thia-4,7-diazacyclononane)iron(III), [LFe]+, has been isolated as the triflate salt from reaction of the previously reported LFeCl with thallium triflate. Spectroscopic characterization confirms an S = 1/2 ground state in non-coordinating solvents with room temperature 礶ff = 1.78 礏 and EPR derived g-values of g1 = 2.06, g2 = 2.03 and g3 = 2.02. [LFe]+ binds a variety of coordinating solvents resulting in six-coordinate complexes [LFe-solvent]+. In acetonitrile the low-spin [LFe-NCMe]+ (g1 = 2.27, g2 = 2.18 and g3 = 1.98) is in equilibrium with [LFe]+ with a binding constant of Keq = 4.03 at room temperature. Binding of H2O, DMF, methanol, DMSO and pyridine to [LFe]+ yields high-spin six-coordinate complexes with EPR spectra that display significant strain in the rhombic zero-field splitting term E/D. Addition of one equivalent of triflic acid to the previously reported diiron species (LFe)2O results in the formation of [(LFe)2OH]OTf, which has been characterized by x-ray crystallography. The aqueous chemistry of [LFe]+ reveals three distinct species as a function of pH: [LFe-OH2]+, [(LFe)2OH]OTf, and (LFe)2O. The pKa values for [LFe-OH2]+ and [(LFe)2OH]OTf are 5.4 .1 and 6.52 .05 respectively. PMID:19166306

  10. (51)V solid-state NMR and density functional theory studies of eight-coordinate non-oxo vanadium complexes: oxidized amavadin.

    PubMed

    Ooms, Kristopher J; Bolte, Stephanie E; Baruah, Bharat; Choudhary, Muhammad Aziz; Crans, Debbie C; Polenova, Tatyana

    2009-05-01

    Using (51)V magic angle spinning solid-state NMR spectroscopy and density functional theory calculations we have characterized the chemical shift and quadrupolar coupling parameters for two eight-coordinate vanadium complexes, [PPh(4)][V(v)(HIDPA)(2)] and [PPh(4)][V(v)(HIDA)(2)]; HIDPA = 2,2'-(hydroxyimino)dipropionate and HIDA = 2,2'-(hydroxyimino)diacetate. The coordination geometry under examination is the less common non-oxo eight coordinate distorted dodecahedral geometry that has not been previously investigated by solid-state NMR spectroscopy. Both complexes were isolated by oxidizing their reduced forms: [V(iv)(HIDPA)(2)](2-) and [V(iv)(HIDA)(2)](2-). V(iv)(HIDPA)(2)(2-) is also known as amavadin, a vanadium-containing natural product present in the Amanita muscaria mushroom and is responsible for vanadium accumulation in nature. The quadrupolar coupling constants, C(Q), are found to be moderate, 5.0-6.4 MHz while the chemical shift anisotropies are relatively small for vanadium complexes, -420 and -360 ppm. The isotropic chemical shifts in the solid state are -220 and -228 ppm for the two compounds, and near the chemical shifts observed in solution. Presumably this is a consequence of the combined effects of the increased coordination number and the absence of oxo groups. Density functional theory calculations of the electric field gradient parameters are in good agreement with the NMR results while the chemical shift parameters show some deviation from the experimental values. Future work on this unusual coordination geometry and a combined analysis by solid-state NMR and density functional theory should provide a better understanding of the correlations between experimental NMR parameters and the local structure of the vanadium centers. PMID:19421628

  11. 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. )

    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.

  12. A redox-active porous coordination network film based on a Ru complex as a building block on an ITO electrode.

    PubMed

    Shinomiya, Takuya; Ozawa, Hiroaki; Mutoh, Yuichiro; Haga, Masa-Aki

    2013-12-01

    The combination of self-assembled monolayer (SAM) and layer-by-layer (LbL) growth methods for the construction of a surface porous film has the potential to incorporate a wide range of chemical functionalities on a solid surface. A novel redox-active Ru complex with 2,6-bis(N-pyridylbenzimidazolyl)-pyridine ligands (Ru complex 1), in which four peripheral pyridine groups act as coordination sites, was used as a building block for a porous coordination network film. By using (4-pyridyl)phenylphosphonic acid as a SAM primer layer on an ITO surface, the Ru complex 1 was immobilized by the successive reaction of PdCl2 on the ITO electrode in the LbL growth method. Multilayer growth was monitored by UV-vis spectra and cyclic voltammetry, in which the linear increases of both absorbance and the peak current were observed. This result indicated that the regular accumulation of Ru complex 1 onto the ITO surface took place. The permselectivity of the present porous coordination network structure was examined using redox-active molecular probes with different sizes and charges such as ferrocene, trimethylaminomethylferrocene, the Os bis(2,6-bis(N-methylbenzimidazolyl)-pyridine) complex, and tetrathiofulvarene (TTF). With the Os complex and cationic ferrocene, only the catalytic peak was observed as a prewave of the adsorbed Ru(II/III) peak at +0.73 V. On the other hand, the oxidation peak of ferrocene was observed around 0 V vs. Fc(+)/Fc even for nine-layered films in addition to the adsorbed Ru(II/III) peak. From these results, not only molecular size but also electrostatic interaction plays an important role in the permeation into the Ru complex 1 porous network film. PMID:24030849

  13. 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)]稨2O}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.

  14. Synthesis, spectroscopic studies, thermal analyses, biological activity of tridentate coordinated transition metal complexes of bi(pyridyl-2-ylmethyl)amine]ligand

    NASA Astrophysics Data System (ADS)

    Abd El-Halim, Hanan F.; Mohamed, Gehad G.

    2016-01-01

    A new tridentate acyclic pincer ligand, [bi(pyridin-2-methyl)amine] (bpma, HL), was synthesized and reacted to form complexes with copper(II), nickel(II), iron(II), cobalt(II) and zinc(II) ions. Both the ligand and its complexes were characterized using elemental analysis, molar conductance, infrared, 1H-NMR-spectroscopy, mass and thermal analyses. According to the spectroscopic data, all of the complexes share the same coordination environment around the metal atoms, consisting two nitrogen-pyridine entities, one nitrogen-methylamine entity, one/two water molecules and/or one/two chloride or bromide ions. Complexes also showed molar conductivity according to the presence of two halide anions outer the coordination sphere except Co(II) and Zn(II) complexes are non electrolytes. Analysis indicates that the metal ions have trigonal bipyramidal structure. Cu(II), Ni(II), Fe(II), Co(II), and Zn(II) metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (G+) and Escherichia coli, and Pseudomonas aeruginosa (G-) bacteria. They showed remarkable antimicrobial activity.

  15. Facile oxidation-based synthesis of sterically encumbered four-coordinate bis(2,9-di-tert-butyl-1,10-phenanthroline)copper(I) and related three-coordinate copper(I) complexes.

    PubMed

    Gandhi, Bhavesh A; Green, Omar; Burstyn, Judith N

    2007-05-14

    A new oxidation-based synthetic route was developed for synthesis of Cu(I) complexes with weakly coordinating ligands, leading to the synthesis of the elusive [Cu(dtbp)2]+ (dtbp, 2,9-di-tert-butyl-1,10-phenanthroline) complex that may be useful as a sensor or as a dye for dye-sensitized solar cells. An acetone solution of either 1 or 2 equiv of dtbp was added to excess Cu(0) and 1 equiv of AgY (Y is O3SCF3-, BF4-, SbF6-, or B(C6F5)4-) in a nitrogen-filled glove box. Following filtration and evaporation under vacuum, crystallization from CH2Cl2 and hexanes results in X-ray quality crystals of Cu(dtbp)(O3SCF3) (1), Cu(dtbp)(BF4) (2), [Cu(dtbp)(acetone)][SbF6] (3), [Cu(dtbp)2][B(C6F5)4].CH2Cl2 (4.CH2Cl2), [Cu(dtbp)2][BF4].CH2Cl2 (5.CH2Cl2), and [Cu(dtbp)2][SbF6].CH2Cl2 (6.CH2Cl2). Complexes 1-6 were characterized by X-ray crystallography and NMR. The Cu atom in complexes 1-3 exhibited distorted trigonal coordination geometries, reflecting the steric effect of the bulky tert-butyl substituents. The structures of the pseudotetrahedral complexes 4, 4.CH2Cl2, 5.CH2Cl2, and 6.CH2Cl2 revealed the longest average Cu-N distances (2.11 A, 2.11 A, 2.10 A, and 2.11 A, respectively) in this class of compounds-longer by more than three standard deviations from the average. PMID:17298052

  16. Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite-selenates

    NASA Astrophysics Data System (ADS)

    Gurzhiy, Vladislav V.; Kovrugin, Vadim M.; Tyumentseva, Olga S.; Mikhaylenko, Pavel A.; Krivovichev, Sergey V.; Tananaev, Ivan G.

    2015-09-01

    Single crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C2H8N]2[(UO2)(SeO4)2(H2O)] (I), [C2H8N]2[(UO2)2(SeO4)3(H2O)] (II), [C4H15N3][H3O]0.5[(UO2)2(SeO4)2.93(SeO3)0.07(H2O)](NO3)0.5 (III), [C2H8N]3[H5O2][(UO2)2(SeO4)3(H2O)2]2(H2O)5 (IV), [C2H8N]2[H3O][(UO2)3(SeO4)4(HSeO3)(H2O)](H2SeO3)0.2 (V), [C4H12N]3[H3O][(UO2)3(SeO4)5(H2O)] (VI), and [C2H8N]3(C2H7N)[(UO2)3(SeO4)4(HSeO3)(H2O)] (VII) have been prepared by isothermal evaporation from aqueous solutions. Their crystal structures have been solved by direct methods and their uranyl selenate and selenite-selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U-Obr-Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers.

  17. Six-coordinate nitro complexes of iron(III) porphyrins with trans S-donor ligands. Oxo-transfer reactivity in the solid state.

    PubMed

    Kurtikyan, Tigran S; Hovhannisyan, Astghik A; Iretskii, Alexei V; Ford, Peter C

    2009-12-01

    Spectroscopic studies demonstrate that the 5-coordinate O-nitrito complexes Fe(Por)(eta(1)-ONO) (Por--meso-tetraphenyl- or meso-tetra-p-tolyl-porphyrinato dianions) react with the thioethers (R(2)S) dimethylsulfide and tetrahydrothiophene to give the 6-coordinate N-nitrito complexes Fe(Por)(R(2)S)(NO(2)). These reactions were conducted in low-temperature porous layered solids formed in a cryostat; however, with excess R(2)S in the atmosphere, the same species are moderately stable at room temperature. Six-coordinate O-nitrito isomers were not observed with the R(2)S proximal ligands, even though DFT calculations for the Fe(P)(DMS)(eta(1)-ONO) and Fe(P)(DMS)(NO(2)) models (P = porphinato dianion, DMS = dimethyl sulfide) show the latter to be only modestly lower energy (approximately 8 kJ/mol) than the former. Leaving this system at room temperature in the presence of excess R(2)S leads eventually to the appearance in the FTIR spectra of the nu(NO) band characteristic of the ferrous nitrosyl Fe(Por)(NO). Concomitantly, the mass spectrum of the gas phase demonstrated the molecular peaks of the sulfoxides R(2)SO, indicating oxygen atom transfer reactivity for the ferric porphryinato complexes of nitrite. PMID:19886653

  18. 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]穤H2O 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.

  19. Novel Ni(II) and Zn(II) complexes coordinated by 2-arylaminomethyl-1H-benzimidazole: molecular structures, spectral, DFT studies and evaluation of biological activity.

    PubMed

    Abdel-Ghani, Nour T; Abo El-Ghar, Maha F; Mansour, Ahmed M

    2013-03-01

    [NiL(1,2)Cl(2)(OH(2))(3)]穤H(2)O and [ZnL(1,2)(CH(3)CO(2))(2)] (L(1)=(1H-benzimidazol-2-ylmethyl)-N-phenyl amine, z=0 and L(2)=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 (N(py)) 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 (NH(sec)), N(py) 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 NiL(2) complexes decreases by the introduction of COOCH(3) group in the ortho-position of the aniline moiety. PMID:23266686

  20. Bulky N-Phosphino-Functionalized N-Heterocyclic Carbene Ligands: Synthesis, Ruthenium Coordination Chemistry, and Ruthenium Alkylidene Complexes for Olefin Metathesis.

    PubMed

    Brown, Christopher C; Rominger, Frank; Limbach, Michael; Hofmann, Peter

    2015-11-01

    Ruthenium chemistry and applications in catalytic olefin metathesis based on N-phosphino-functionalized N-heterocyclic carbene ligands (NHCPs) are presented. Alkyl NHCP Ru coordination chemistry is described, and access to several potential synthetic precursors for ruthenium alkylidene complexes is outlined, incorporating both trimethylsilyl and phenyl alkylidenes. The Ru alkylidene complexes are evaluated as potential olefin metathesis catalysts and were shown to behave in a latent fashion. They displayed catalytic activity at elevated temperatures for both ring closing metathesis and ring opening metathesis polymerization. PMID:26479425

  1. A New Family of Anionic Fe(III) Spin Crossover Complexes Featuring a Weak-Field N2 O4 Coordination Octahedron.

    PubMed

    Takahashi, Kazuyuki; Kawamukai, Kiko; Okai, Mitsunobu; Mochida, Tomoyuki; Sakurai, Takahiro; Ohta, Hitoshi; Yamamoto, Takashi; Einaga, Yasuaki; Shiota, Yoshihito; Yoshizawa, Kazunari

    2016-01-01

    Unprecedented anionic Fe(III) spin crossover (SCO) complexes involving a weak-field O,N,O-tridentate ligand were discovered. The SCO transition was evidenced by the temperature variations in magnetic susceptibility, M枚ssbauer spectrum, and coordination structure. The DFT calculations suggested that larger coefficients on the azo group in the HOMO-1 of a ligand might contribute to the enhancement of a ligand-field splitting energy. The present anionic SCO complex also exhibited the light- induced excited-spin-state trapping effect. PMID:26642040

  2. 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

  3. 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.

  4. 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.

  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. 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(蟽-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M 2(渭 2-NO)]; (c) threefold nitrosyl bridges, [M 3(渭 3-NO)]; (d) 蟽/蟺-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 脜/1.60-1.90 脜/180-160掳 and for bent nitrosyls are 1.16-1.22 脜/1.80-2.00 脜/140-110掳. The [M 2(渭 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 脜/1.18-1.22 脜/1.80-2.00 脜/90-70掳, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 脜/1.20-1.24 脜/1.90-2.10 脜/130-110掳. 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 脜/1.80-1.90 脜, 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 谓(NO)-values. The wide wavenumber range found for the 谓(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 畏 5-C 5H 5 [-60 cm -1]; 畏 5-C 5H 4Me [-70 cm -1]; 畏 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' 谓(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 (鈥4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (鈥5s4d5p): [1730 Mo(NO)]; [鈥, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (鈥6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [鈥, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solutions or in the crystalline state, can cause 谓(NO)* variations (mostly reductions) of up to ca. 30 cm -1. Three spectroscopic criteria are used to distinguish between linear and bent NO groups. These are: (i) the values of 谓( 14NO) themselves, and (ii) the isotopic band shift - (IBS) - parameter which is defined as [谓( 14NO)-谓( 15NO)], and, (iii) the isotopic band ratio - (IBR) - given by [谓( 15NO/谓 14NO)]. The former is illustrated with the 谓( 14NO)-data from trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) structures of [M(NO(L) 4] complexes (where M = Fe, Co, Ru, Rh, Os, Ir and L = ligand). These values indicate that linear (180-170掳) and strongly bent (130-120掳) NO groups in these compounds absorb over the 1862-1690 cm -1 and 1720-1525 cm -1-regions, respectively. As was explicitly demonstrated for the linear nitrosyls, these extensive regions reflect the presence in different complexes of a very wide range of co-ligands or ionic charges associated with the metal atom of the nitrosyl group. A plot of the IBS parameter against M-N-O bond-angle for compounds with general formulae [M(NO)(L) y] ( y = 4, 5, 6) reveals that the IBS-values are clustered between 45 and 30 cm -1 or between 37 and 25 cm -1 for linear or bent NO groups, respectively. A plot of IBR shows a less well defined pattern. Overall it is suggested that bent nitrosyls absorb ca. 60-100 cm -1 below, and have smaller co-ligand band-shifts, than their linear counterparts. Spectroscopic 谓(NO) data of the bridging or other types of NO ligands are comparatively few and therefore it has not been possible to give other than general ranges for 'neutral co-ligand' values. Moreover the bridging species data often depend on corrections for the effects of electronically-active co-ligands such as cyclopentadienyl-like groups. The derived neutral co-ligand estimates, 谓(NO)*, are: (a) twofold bridged nitrosyls with a metal-metal bond order of one, or greater than one, absorb at ca. 1610-1490 cm -1; (b) twofold bridged nitrosyl ligands with a longer non-bonding M⋯M distance, ca. 1520-1490 cm -1; (c) threefold bridged nitrosyls, ca. 1470-1410 cm -1; (d) 蟽/蟺 dihaptonitrosyl, [M(畏 2-NO)], where M = Cr, Mn and Ni; ca. 1490-1440 cm -1. Isonitrosyls, from few examples, appear to absorb below ca. 1100 cm -1. To be published DFT calculations of the infrared and Raman spectra of complexes with formulae [M(NO) 4- n(CO) n] (M = Cr, Mn, Fe, Co, Ni, and n = 0, 1, 2, 3, 4, respectively) are used as models for the assignments of the 谓(MN) and 未(MNO) bands from more complex metal nitrosyls.

  7. The metal complexes of amino acids and their N-substituted derivatives鈥擵II. 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路 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) 2路2H 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 伪-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.

  8. A new coordination mode of (E)-3-(3-hydroxyl-phenyl)-acrylic acid in copper complex: Crystal structure and magnetic properties

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Zhou, Pei; Zheng, Chunying; Li, Hui

    2015-05-01

    A copper complex {[Cu(py)2(L)2]2CH3OH}n (HL=(E)-3-(3-hydroxyl-phenyl)-acrylic acid) (1) with acrylic acid ligand was synthesized and structurally analyzed by IR, elemental analysis, TGA and the single-crystal X-ray diffraction methods. It is the first time to find that phenolic hydroxyl of L coordinates to Cu(II). Complex 1 exhibits 1D chain by a double-bridge of ligands, and the 3D supramolecular framework in complex 1 is constructed by ?-? stacking interactions and van der Waals Contacts among the 1D chains. The magnetic properties of complex 1 have been studied.

  9. 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

  10. Uranyl and/or rare-earth mellitates in extended organic-inorganic networks: a unique case of heterometallic cation-cation interaction with U(VI)?O-Ln(III) bonding (Ln = Ce, Nd).

    PubMed

    Volkringer, Christophe; Henry, Natacha; Grandjean, St閜hane; Loiseau, Thierry

    2012-01-18

    A series of uranyl and lanthanide (trivalent Ce, Nd) mellitates (mel) has been hydrothermally synthesized in aqueous solvent. Mixtures of these 4f and 5f elements also revealed the formation of a rare case of lanthanide-uranyl coordination polymers. Their structures, determined by XRD single-crystal analysis, exhibit three distinct architectures. The pure lanthanide mellitate Ln(2)(H(2)O)(6)(mel) possesses a 3D framework built up from the connection of isolated LnO(6)(H(2)O)(3) polyhedra (tricapped trigonal prism) through the mellitate ligand. The structure of the uranyl mellitate (UO(2))(3)(H(2)O)(6)(mel)11.5H(2)O is lamellar and consists of 8-fold coordinated uranium atoms linked to each other through the organic ligand giving rise to the formation of a 2D 3(6) net. The third structural type, (UO(2))(2)Ln(OH)(H(2)O)(3)(mel)2.5H(2)O, involves direct oxygen bondings between the lanthanide and uranyl centers, with the isolation of a heterometallic dinuclear motif. The 9-fold coordinated Ln cation, LnO(5)(OH)(H(2)O)(3), is linked to the 7-fold coordinated uranyl (UO(2))O(4)(OH) (pentagonal bipyramid) via one ?(2)-hydroxo group and one ?(2)-oxo group. The latter is shared between the uranyl bonding (U?O = 1.777(4)/1.779(6) ) and a long Ln-O bonding (Ce-O = 2.822(4) ; Nd-O = 2.792(6) ). This unusual linkage is a unique illustration of the so-called cation-cation interaction associating 4f and 5f metals. The dinuclear motif is then further connected through the mellitate ligand, and this generates organic-inorganic layers that are linked to each other via discrete uranyl (UO(2))O(4) units (square bipyramid), which ensure the three-dimensional cohesion of the structure. The mixed U-Ln carboxylate is thermally decomposed from 260 to 280 癈 and then transformed into the basic uranium oxide (U(3)O(8)) together with U-Ln oxide with the fluorite structural type ("(Ln,U)O(2)"). At 1400 癈, only fluorite type "(Ln,U)O(2)" is formed with the measured stoichiometry of U(0.63)Ce(0.37)O(2) and U(0.60)Nd(0.40)O(2-?). PMID:22206304

  11. U(VI) uranyl cation-cation interactions in framework germanates.

    PubMed

    Morrison, Jessica M; Moore-Shay, Laura J; Burns, Peter C

    2011-03-21

    The isomorphous compounds NH(4)[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (1), K[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (2), Li(3)O[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (3), and Ba[(UO(6))(2)(UO(2))(9)(GeO(4))(2)] (4) were synthesized by hydrothermal reaction at 220 癈. The structures were determined using single crystal X-ray diffraction and refined to R(1) = 0.0349 (1), 0.0232 (2), 0.0236 (3), 0.0267 (4). Each are trigonal, P(3)1c. 1: a = 10.2525(5), c = 17.3972(13), V = 1583.69(16) (3), Z = 2; 2: a = 10.226(4), c = 17.150(9), V = 1553.1(12) (3), Z = 2; 3: a = 10.2668(5), c = 17.0558(11), V = 1556.94(15) (3), Z = 2; 4: a = 10.2012(5), c = 17.1570(12), V = 1546.23(15) (3), Z = 2. There are three symmetrically independent U sites in each structure, two of which correspond to typical (UO(2))(2+) uranyl ions and the other of which is octahedrally coordinated by six O atoms. One of the uranyl ions donates a cation-cation interaction, and accepts a different cation-cation interaction. The linkages between the U-centered polyhedra result in a relatively dense three-dimensional framework. Ge and low-valence sites are located within cavities in the framework of U-polyhedra. Chemical, thermal, and spectroscopic characterizations are provided. PMID:21291192

  12. Exploring the coordinative adaptation and molecular shapes of trinuclear CuM(II) (M = Zn/Cd) complexes derived from salen type Schiff bases: structural and theoretical studies.

    PubMed

    Hazari, Alokesh; Das, Lakshmi Kanta; Bauz谩, Antonio; Frontera, Antonio; Ghosh, Ashutosh

    2016-04-01

    Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (1), [(CuL(R))2Zn(NCS)(渭1,1-NCS)] (2) and [(CuL(R))2Cd(渭1,3-NCS)2] (4) have been synthesized using [CuL] and [CuL(R)] as "metalloligands" (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and H2L(R) = N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligands" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex 2, the two terminal "metalloligands" [CuL(R)] are square pyramidal, as one of the SCN(-) ions makes an unusual 渭1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a usual fashion making its geometry also square pyramidal. For 4 which possesses an angular trinuclear structure, in addition to double phenoxido bridges from two terminal [CuL(R)], both the SCN(-) ions are S-bonded to Cd(ii) and form a bridge (cis-渭1,3-SCN) between Cd(ii) and each of the terminal Cu(ii) ions. This structure is different from its unreduced analogue in which NCS(-) was N-terminal coordinated to Cd(ii) (3/3'). All the structures have been optimized using density functional theory (DFT) calculations. It has been found that for H2L, optimized structures like 1 and 2 differ only by 0.4 kcal mol(-1) but the H2L(R) structure 2 is more stable by 5.5 kcal mol(-1) than the structure resembling 1. For Cd(ii) complexes also, H2L optimized structures such as 3 and 4 do not differ significantly in energy (1.0 kcal mol(-1)) but the H2L(R) structure 4 is more stable than that of 3 by 4.6 kcal mol(-1). In fact, structure 4 has been found to be the most stable one among the other possible isomers of H2L(R). PMID:26931060

  13. Versatile structures of group 13 metal halide complexes with 4,4'-bipy: from 1D coordination polymers to 2D and 3D metal-organic frameworks.

    PubMed

    Sevastianova, Tatiana N; Bodensteiner, Michael; Maulieva, Albina F; Davydova, Elena I; Virovets, Alexander V; Peresypkina, Eugenia V; Bal醶s, G醔or; Gra遧, Christian; Seidl, Michael; Scheer, Manfred; Frenking, Gernot; Berezovskaya, Ekaterina A; Kazakov, Igor V; Khoroshilova, Olesya V; Timoshkin, Alexey Y

    2015-12-21

    A systematic structural study of complexes formed by aluminium and gallium trihalides with 4,4'-bipyridine (bipy) in 2?:?1, 1?:?1, and 1?:?2 stoichiometric ratios has been performed. Molecular structures of 11 complexes in the solid state have been determined for the first time. Complexes of 2?:?1 composition are molecular, while complexes of 1?:?1 composition form metal-organic frameworks of different kinds: an ionic 3D network (three interpenetrated lvt nets for AlCl3bipy), an ionic 2D network for AlBr3bipy and GaBr3bipy and a 1D coordination polymer in the case of GaCl3bipy. Thus, the nature of the Lewis acid plays a critical role in the structural type of the complex in the solid state. Incorporation of excess bipy molecules into (GaCl3bipy)? (formation of crystallosolvate) leads to an unprecedented change of the molecular structure from a non-ionic 1D coordination polymer to an ionic 2D metal organic framework [GaCl2bipy2](+)[GaCl4](-)2bipy. As indicated by the temperature-dependent XRD study, removal of bipy by heating in a vacuum restores the non-ionic 1D structure. Quantum chemical computations for simple cluster model systems (up to eight Al and Ga atoms) reveal that ionic forms are slightly favourable, although the energy differences between the ionic and non-ionic structures are not large. These theoretical predictions are in good agreement with experimental findings. Thus, even relatively simple cluster models may be used to indicate the structural preferences in the solid state. Both experimental and computational IR frequency shifts of the in-plane ring bending mode of bipy upon complexation correlate well with the M-N bond distances in the complexes. PMID:26564471

  14. Mixed-valence copper(i,ii) complexes with 4-(1H-pyrazol-1-yl)-6-R-pyrimidines: from ionic structures to coordination polymers.

    PubMed

    Vinogradova, Katerina A; Krivopalov, Viktor P; Nikolaenkova, Elena B; Pervukhina, Natalia V; Naumov, Dmitrii Yu; Boguslavsky, Evgenii G; Bushuev, Mark B

    2015-12-22

    Two pyrimidine-based ligands, 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(morpholino)pyrimidine () and 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-phenoxypyrimidine (), and a series of mixed-valence copper(i,ii) halide complexes, [Cu(L(2))2Br]2[Cu2Br4] (), [Cu(L(2))2Cl][CuCl2] (), and [Cu2L(3)Br3]n (), have been synthesized. The complex [Cu(L(2))2Br]2[Cu2Br4] was prepared by the reaction of with CuBr2 in a 1?:?1 molar ratio in MeCN. Its chlorido-analogue, the complex [Cu(L(2))2Cl][CuCl2], was synthesized by the reaction between , CuCl2 and CuCl in a 2?:?1?:?1 molar ratio in MeCN. The ligand acts as a chelating one. In the structures of the complexes [Cu(L(2))2Br]2[Cu2Br4] and [Cu(L(2))2Cl][CuCl2] the Cu(2+) ion is in the cationic part of the complex whereas the Cu(+) ion is located in the anionic part. The best way to synthesize the mixed-valence 1D coordination polymer [Cu2L(3)Br3]n is to react CuBr2 with in a 2?:?1 molar ratio in the MeCN/CHCl3 mixture on heating. In the structure of [Cu2L(3)Br3]n the ligand shows chelating/bridging tridentate coordination. This is the first example of the tridentate coordination of 4-(1H-pyrazol-1-yl)-6-R-pyrimidines. The striking difference between the coordination behavior of and (chelating bidentate vs. chelating/bridging coordination) is related with the possibility of rotation of the 6-phenoxy group around the C-O bond which makes the N(1) pyrimidine atom less sterically hindered, enabling it to participate in metal ion binding. Importantly, all copper ions in [Cu2L(3)Br3]n show similar tetrahedral environments, CuNBr3 and CuN2Br2, which is extremely rare for mixed-valence copper(i,ii) compounds. The ligands and show blue emission which is quenched upon their coordination to copper ions. The 1D coordination polymer [Cu2L(3)Br3]n shows high thermal stability and unusual solvent-occlusion properties. The role of the substituents favoring the formation of the mixed-valence copper(i,ii) complexes with 4-(1H-pyrazol-1-yl)-6-R-pyrimidines is discussed. PMID:26600314

  15. ESR distance measures show that Cu^2+ coordinates to Histidine 114 in the EcoRI-DNA complex

    NASA Astrophysics Data System (ADS)

    Yang, Zhongyu

    2009-03-01

    Metal coordination of EcoRI is intimately connected to its function of cleaving viral DNA. In order to gain insight into this process pulsed ESR distance measurement methodology was extended to the case of copper-copper and copper-nitroxide in proteins. This talk will discuss the first results on Cu^2+-Cu^2+ and Cu^2+-nitroxide distances measured in proteins by pulsed ESR. A triangulation procedure that involved the measurement of several long range distances (2-4 nm) demonstrates that copper ions bind to histidines 114 in EcoRI. The combination of ESR distance measurement and molecular dynamics simulations show distinct differences in the coordination of Cu^2+ versus the natural cofactor Mg^2+. This difference translates into the differences in roles of the metal ions - Mg^2+ catalyzes cleavage while Cu^2+ binding without cleavage of DNA.

  16. 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 損roof 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

  17. tBu3P-Coordinated 2-Phenylaniline-Based Palladacycle Complex As Precatalyst for Pd-Catalyzed Coupling Reactions of Aryl Halides with Polyfluoroarenes via C-H Activation Strategy

    PubMed Central

    Zhang, Hong-Hai; Dong, Jie; Hu, Qiao-Sheng

    2014-01-01

    tBu3P-Coordinated 2-phenylaniline-based palladacycle complex was demonstrated to be an efficient precatalyst for Pd-catalyzed coupling reactions of aryl halides with polyfluoroarenes via C-H activation strategy. The readily accessibility and easy handling nature of tBu3P- coordinated 2-aminobiphenyl-based palladacycle complex and the high yields of the reaction makes tBu3P-coordinated 2-aminobiphenyl-based palladacycle complex an attractive precatalyst for the cross-coupling reaction of aryl halides with polyfluoroarenes. PMID:24778575

  18. 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.

  19. Square-antiprismatic eight-coordinate complexes of divalent first-row transition metal cations: a density functional theory exploration of the electronic-structural landscape.

    PubMed

    Conradie, Jeanet; Patra, Ashis K; Harrop, Todd C; Ghosh, Abhik

    2015-02-16

    Density functional theory (in the form of the PW91, BP86, OLYP, and B3LYP exchange-correlation functionals) has been used to map out the low-energy states of a series of eight-coordinate square-antiprismatic (D2d) first-row transition metal complexes, involving Mn(II), Fe(II), Co(II), Ni(II), and Cu(II), along with a pair of tetradentate N4 ligands. Of the five complexes, the Mn(II) and Fe(II) complexes have been synthesized and characterized structurally and spectroscopically, whereas the other three are as yet unknown. Each N4 ligand consists of a pair of terminal imidazole units linked by an o-phenylenediimine unit. The imidazole units are the strongest ligands in these complexes and dictate the spatial disposition of the metal three-dimensional orbitals. Thus, the dx(2)-y(2) orbital, whose lobes point directly at the coordinating imidazole nitrogens, has the highest orbital energy among the five d orbitals, whereas the dxy orbital has the lowest orbital energy. In general, the following orbital ordering (in order of increasing orbital energy) was found to be operative: dxy < dxz = dyz ? dz(2) < dx(2)-y(2). The square-antiprism geometry does not lead to large energy gaps between the d orbitals, which leads to an S = 2 ground state for the Fe(II) complex. Nevertheless, the dxy orbital has significantly lower energy relative to that of the dxz and dyz orbitals. Accordingly, the ground state of the Fe(II) complex corresponds unambiguously to a dxy(2)dxz(1)dyz(1)dz(2)(1)dx(2)-y(2)(1) electronic configuration. Unsurprisingly, the Mn(II) complex has an S = 5/2 ground state and no low-energy d-d excited states within 1.0 eV of the ground state. The Co(II) complex, on the other hand, has both a low-lying S = 1/2 state and multiple low-energy S = 3/2 states. Very long metal-nitrogen bonds are predicted for the Ni(II) and Cu(II) complexes; these bonds may be too fragile to survive in solution or in the solid state, and the complexes may therefore not be isolable. Overall, the different exchange-correlation functionals provided a qualitatively consistent and plausible picture of the low-energy d-d excited states of the complexes. PMID:25574575

  20. Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex.

    PubMed

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

    2014-06-23

    We report the uranium(VI) carbene imido oxo complex [U(BIPM(TMS))(NMes)(O)(DMAP)2] (5, BIPM(TMS) = C(PPh2 NSiMe3)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(BIPM(TMS))(O)2(DMAP)2] (6). PMID:24842784

  1. 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

  2. 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 <