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PubMed1977

Some antagonists of dantrolene sodium on the isolated diaphragm muscle of the rat.

The effects of a number of potential antagonists of dantrolene sodium have been studied on twitches of the isolated hemidiaphragm preparation of the rat stimulated directly at a frequency of 0-1 Hz, after complete neuromuscular block produced by tubocurarine or erabutoxin a. The substances selected as possible dantrolene antagonists were uranyl ions, thiocyanate ions, adrenaline, caffeine, quazodine, quinine, 4-aminopyridine and the calcium ionophore a23187, all of which facilitate excitation-contraction coupling in one way or another. Contracture was the main feature of the response to A23187, the increase in the tension of the dantrolene-depressed twitches being very slight. All the remaining compounds increased the amplitude of the twitches, but only 4-aminopyridine, quinine, quazodine and caffeine were capable of restoring to the control amplitude twitches that had been maximally depressed by dantrolene. OF these, 4-aminopyridine and quinine were the most potent on a molar basis.

Animals↗
PubMed1982

Glucose transport system in a facultative iron-oxidizing bacterium, Thiobacillus ferrooxidans.

Properties of a heat-labile glucose transport system in Thiobacillus ferrooxidans strain AP-44 were investigated with iron-grown cells. [14C]glucose was incorporated into cell fractions, and the cells metabolized [14C]glucose to 14CO2. Amytal, rotenone, cyanide, azide, 2,4-dinitrophenol, and dicyclohexylcarbodiimide strongly inhibited [14C]glucose uptake activity, suggesting the presence of an energy-dependent glucose transport system in T. ferrooxidans. Heavy metals, such as mercury, silver, uranium, and molybdate, markedly inhibited the transport activity at 1 mM. When grown on mixotrophic medium, the bacteria preferentially utilized ferrous iron as an energy source. When iron was exhausted, the cells used glucose if the concentration of ferrous sulfate in the medium was higher than 3% (wt/vol). However, when ferrous sulfate was lower than 1%, both of the energy sources were consumed simultaneously.

Biological Transport, Active↗
PubMed1990

Metal toxicity and the respiratory tract.

The type of lung disease caused by metal compounds depends on the nature of the offending agent, its physicochemical form, the dose, exposure conditions and host factors. The fumes or gaseous forms of several metals, e.g. cadmium (Cd), manganese (Mn), mercury (Hg), nickel carbonyl (Nl(CO)4, zinc chloride (ZnCl2), vanadium pentoxide (V2O5), may lead to acute chemical pneumonitis and pulmonary oedema or to acute tracheobronchitis. Metal fume fever, which may follow the inhalation of metal fumes e.g. zinc (Zn), copper (Cu) and many others, is a poorly understood influenza-like reaction, accompanied by an acute self-limiting neutrophil alveolitis. Chronic obstructive lung disease may result from occupational exposure to mineral dusts, including probably some metallic dusts, or from jobs involving the working of metal compounds, such as welding. Exposure to cadmium may lead to emphysema. Bronchial asthma may be caused by complex platinum salts, nickel, chromium or cobalt, presumably on the basis of allergic sensitization. The cause of asthma in aluminium workers is unknown. It is remarkable that asthma induced by nickel (Ni) or chromium (Cr) is apparently infrequent, considering their potency and frequent involvement as dermal sensitizers. Metallic dusts deposited in the lung may give rise to pulmonary fibrosis and functional impairment, depending on the fibrogenic potential of the agent and on poorly understood host factors. Inhalation of iron compounds causes siderosis, a pneumoconiosis with little or no fibrosis. Hard metal lung disease is a fibrosis characterized by desquamative and giant cell interstitial pneumonitis and is probably caused by cobalt, since a similar disease has been observed in workers exposed to cobalt in the absence of tungsten carbide. Chronic beryllium disease is a fibrosis with sarcoid-like epitheloid granulomas and is presumably due to a cell-mediated immune response to beryllium. Such a mechanism may be responsible for the pulmonary fibrosis occasionally found in subjects exposed to other metals e.g. aluminium (Al), titanium (Ti), rare earths. The proportion of lung cancer attributable to occupation is around 15%, with exposure to metals being frequently incriminated. Underground mining of e.g. uranium or iron is associated with a high incidence of lung cancer, as a result of exposure to radon. At least some forms of arsenic, chromium and nickel are well established lung carcinogens in humans. There is also evidence for increased lung cancer mortality in cadmium workers and in iron or steel workers.

Asthma↗
PubMed1997

Influence of the Nature of the Ligands on the Electronic Ground State of Organouranium(V) Compounds, Studied by Electron Paramagnetic Resonance.

Organouranium(V) amide compounds were studied by electron paramagnetic resonance in frozen solution. Their g-tensors were quantitatively interpreted by assuming that dialkylamide, C(8)H(8), C(5)H(5), C(5)Me(5), and THF ligands interact only weakly with 5f orbitals of the central U(V) atom, so that the total angular momentum J = 5/2 remains a good quantum number for the description of the electronic ground state of these complexes (weak-field approximation). In the absence of THF ligands, the ground state is predominantly made of |M(J)()| = (1)/(2) states, with a significant admixture of |M(J)()| = (5)/(2) states independent of the symmetry of the complex. Thus 5f orbitals are essentially nonbonding, and the metal ligand bonding should involve mainly uranium 6d orbitals. A THF ligand induces a significant admixture of |M(J)()| = (3)/(2) states. Substitution of amide ligands by alkoxide ligands is characterized by strong U(V)(5f)-OR interactions, which breaks the weak-field approximation. This sensitivity to oxygen ligands indicates that 5f orbitals contribute to the U(V)-oxygen bonding.

Journal Article↗
PubMed2000

Isolation of U(VI) reduction-deficient mutants of Shewanella putrefaciens.

A U(VI) reduction-deficient mutant (Urr) screening technique was developed and combined with chemical mutagenesis procedures to identify a Urr mutant of Shewanella putrefaciens strain 200. The Urr mutant lacked the ability to grow anaerobically on U(VI) and NO(2)(-), yet retained the ability to grow anaerobically on eight other compounds as terminal electron acceptor. All 11 members of previously isolated sets of Fe(III) and Mn(IV) reduction-deficient mutants of S. putrefaciens 200 displayed Urr-positive phenotypes with the Urr screen and were capable of anaerobic growth on U(VI). This is the first reported isolation of a respiratory mutant that is unable to grow anaerobically on U(VI) as terminal electron acceptor.

Anaerobiosis↗
PubMed2006

Structural polarity induced by cooperative hydrogen bonding and lone-pair alignment in the molecular uranyl iodate Na2[UO2(IO3)4(H2O)].

Na2[UO2(IO3)4(H2O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na+ cations and [UO2(IO3)4(H2O)](2-) anions. The [UO2(IO3)4(H2O)](2-) anions are formed from the coordination of a nearly linear uranyl, UO2(2+), cation by four monodentate IO(3-) anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO2(IO3)4(H2O)](2-) anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na2[UO2(IO3)4(H2O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a = 11.3810(12) A, b = 8.0547(8) A, c = 7.6515(8) A, beta = 90.102(2) degrees , Z = 2, T = 193 K) found for this compound is consistent with the structure. Second-harmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16x alpha-SiO2.

Journal Article↗
PubMed2004

Expanding dinitrogen reduction chemistry to trivalent lanthanides via the LnZ3/alkali metal reduction system: evaluation of the generality of forming Ln2(mu-eta2:eta2-N2) complexes via LnZ3/K.

The Ln[N(SiMe(3))(2)](3)/K dinitrogen reduction system, which mimicks the reactions of the highly reducing divalent ions Tm(II), Dy(II), and Nd(II), has been explored with the entire lanthanide series and uranium to examine its generality and to correlate the observed reactivity with accessibility of divalent oxidation states. The Ln[N(SiMe(3))(2)](3)/K reduction of dinitrogen provides access from readily available starting materials to the formerly rare class of M(2)(mu-eta(2):eta(2)-N(2)) complexes, [[(Me(3)Si)(2)N](2)(THF)Ln](2)(mu-eta(2):eta(2)-N(2)), 1, that had previously been made only from TmI(2), DyI(2), and NdI(2) in the presence of KN(SiMe(3))(2). This LnZ(3)/alkali metal reduction system provides crystallographically characterizable examples of 1 for Nd, Gd, Tb, Dy, Ho, Er, Y, Tm, and Lu. Sodium can be used as the alkali metal as well as potassium. These compounds have NN distances in the 1.258(3) to 1.318(5) A range consistent with formation of an (N=N)(2)(-) moiety. Isolation of 1 with this selection of metals demonstrates that the Ln[N(SiMe(3))(2)](3)/alkali metal reaction can mimic divalent lanthanide reduction chemistry with metals that have calculated Ln(III)/Ln(II) reduction potentials ranging from -2.3 to -3.9 V vs NHE. In the case of Ln = Sm, which has an analogous Ln(III)/Ln(II) potential of -1.55 V, reduction to the stable divalent tris(amide) complex, K[Sm[N(SiMe(3))(2)](3)], is observed instead of dinitrogen reduction. When the metal is La, Ce, Pr, or U, the first crystallographically characterized examples of the tetrakis[bis(trimethylsilyl)amide] anions, [M[N(SiMe(3))(2)](4)](-), are isolated as THF-solvated potassium or sodium salts. The implications of the LnZ(3)/alkali metal reduction chemistry on the mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.

Journal Article↗
PubMed2004

Reduction of arsenic content in a complex galena concentrate by Acidithiobacillus ferrooxidans.

BACKGROUND: Bioleaching is a process that has been used in the past in mineral pretreatment of refractory sulfides, mainly in the gold, copper and uranium benefit. This technology has been proved to be cheaper, more efficient and environmentally friendly than roasting and high pressure moisture heating processes. So far the most studied microorganism in bioleaching is Acidithiobacillus ferrooxidans. There are a few studies about the benefit of metals of low value through bioleaching. From all of these, there are almost no studies dealing with complex minerals containing arsenopyrite (FeAsS). Reduction and/or elimination of arsenic in these ores increase their value and allows the exploitation of a vast variety of minerals that today are being underexploited. RESULTS: Arsenopyrite was totally oxidized. The sum of arsenic remaining in solution and removed by sampling represents from 22 to 33% in weight (yield) of the original content in the mineral. The rest of the biooxidized arsenic form amorphous compounds that precipitate. Galena (PbS) was totally oxidized too, anglesite (PbSO4) formed is virtually insoluble and remains in the solids. The influence of seven factors in a batch process was studied. The maximum rate of arsenic dissolution in the concentrate was found using the following levels of factors: small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. It was also found that ferric chloride and carbon dioxide decreased the arsenic dissolution rate. Bioleaching kinetic data of arsenic solubilization were used to estimate the dilution rate for a continuous culture. Calculated dilution rates were relatively small (0.088-0.103 day(-1)). CONCLUSION: Proper conditions of solubilization of arsenic during bioleaching are key features to improve the percentage (22 to 33% in weight) of arsenic removal. Further studies are needed to determine other factors that influence specifically the solubilization of arsenic in the bioleaching system such as: pH, dissolved oxygen concentration, redox potentials, nature of concentrate and temperature among others. At. ferrooxidans was able to completely oxidize the minerals present during the arsenic bioleaching. Other elements present originally in the concentrate such as Zn, Sb, and Cu were also solubilized. The process of bioleaching is expected to be influenced by mechanisms that still need to be established due to the diversity of the minerals involved and by the presence of traces of metals in the concentrate. The increase in pulp density generates a decrease in the dissolved arsenic concentration. This decrease is greater in runs where air was not injected to the system. The maximum rate of arsenic dissolution in the concentrate was found using; small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. The effect of addition of ferric chloride during the arsenic bioleaching resulted in a decrease of the solubilized arsenic in the system. The presence of CO2 is associated to the decrease in arsenic dissolution.

Acidithiobacillus↗
PubMedDate not supplied

[Quantitative assessment of inhalation exposure to various transuranium radionuclide compounds by integral nonstochastic criteria].

The comparison of the danger from inhalation of radionuclide transuranium compounds differently transferred within the body was made by the results of an examination of 169 mongrel dogs and 2000 Wistar rats. Effective and ineffective levels of the radionuclide inhaled were determined by integral nonstochastic criteria, that is, 50 per cent death rate, shortening and increase of the average life and reduction of body mass.

Administration, Inhalation↗
PubMed2002

Syntheses, X-ray crystal structures, and magnetic properties of novel linear M2[II]U[IV] complexes (M=Co, Ni, Cu, Zn).

Attempts to prepare heterobimetallic complexes in which 3d and uranium magnetic ions are associated by means of the Schiff bases H(2)L(i) derived from 2-hydroxybenzaldehyde or 2-hydroxy-3-methoxybenzaldehyde were unsuccessful because of ligand transfer reactions between [ML(i)] (M=Co, Ni, Cu) and UCl(4) that led to the mononuclear Schiff base complexes of uranium [UL(i)Cl(2)]. The crystal structure of [UL(3)Cl(2)(py)(2)] [L(3)=N,N'-bis(3-methoxysalicylidene)-ethylenediamine; py=pyridine] was determined. The hexadentate Schiff base ligand N,N'-bis(3-hydroxysalicylidene)-2,2-dimethyl-1,3-propanediamine (L) was useful for the synthesis of novel trinuclear complexes of the general formula [[ML(py)](2)U] (M=Co, Ni, Zn) or [[CuL(py)]M'[CuL]] (M'=U, Th, Zr) by reaction of [M(H(2)L)] with [M'(acac)(4)] (acac=MeCOCHCOMe). The crystal structures of the Co(2)U, Ni(2)U, Zn(2)U, Cu(2)U, and Cu(2)Th complexes show that the two ML fragments are orthogonal, being linked to the central actinide ion by the two pairs of oxygen atoms of the Schiff base ligand. In each compound, the UO(8) core exhibits the same dodecahedral geometry, and the three metals are linear. The magnetic study indicated that the two Cu(2+) ions are not coupled in the Cu(2)Zr and Cu(2)Th compounds. The magnetic behavior of the Co(2)U, Ni(2)U, and Cu(2)U complexes was compared with that of the Zn(2)U derivative, in which the paramagnetic 3d ion was replaced with the diamagnetic Zn(2+) ion. A weak antiferromagnetic coupling was observed between the Ni(2+) and the U(4+) ions, while a ferromagnetic interaction was revealed between the Cu(2+) and U(4+) ions.

Journal Article↗
PubMed2003

Mineralogical characterization of arsenic in uranium mine tailings precipitated from iron-rich hydrometallurgical solutions.

Arsenic-rich uranium mine tailings from the Rabbit Lake in-pit tailings management facility (RLITMF) in northern Saskatchewan, Canada, were investigated to determine the mineralogy and long-term stability of secondary arsenic precipitates formed from iron-rich hydrometallurgical solutions. Total arsenic and iron concentrations in six iron-rich samples of the mine tailings ranged from 56 to 6,000 microg/g and from 12 600 to 30 200 microg/g, respectively (Fe/As molar ratios of 5.3-303). On the basis of stability field diagrams generated from pH, Eh, and temperature measurements on tailings samples (mean values of 9.79, +162 mV, and 2.8 degrees C, respectively), it was concluded that arsenic and iron in the tailings were stable as As5+ and Fe3+. Synchrotron-based X-ray absorption spectroscopic studies of tailings samples, fresh mill precipitates, and reference compounds showed that the arsenic in iron-rich areas of the tailings existed as the stable As5+ and was adsorbed to 2-line ferrihydrite through inner-sphere bidentate linkages. Furthermore, under the conditions in the RLITMF, the 2-line ferrihydrite did not undergo any measurable conversion to more crystalline goethite or hematite, even in tailings discharged to the RLITMF 10 yr prior to sampling.

Arsenic↗
PubMed1977

Factors involved in heavy metal poisoning.

The heavy metals include at least 40 elements but cadmium, lead, and mercury have been most extensively studied. The biological properties of heavy metals are discussed in terms of three important characteristics: the ability to form, irreversibly, complexes and chelates with organic ligands; the properties to form organic-metallic bonds; and the potential to undergo oxidation-reduction reactions. The formation of complexes and chelates within the body is shown to influence greatly the dynamics of transport, distribution, and excretion of several important metal cations. The excretion of uranium is influenced by acid-base balance in the body because uranium forms complexes with bicarbonate anions that are filtered by the kidneys. The biliary excretion of methylmercury depends on the formation of small molecular weight complexes with sulfur-containing amiono acids and the peptides in the liver. The degree of enterohepatic recirculation of a variety of heavy metals appears to depend on the chemical nature of the bilary complexes. The oxidation of elemental to divalent ionic mercury is the crurial step in the retention and tissue deposition of inhaled mercury vapor. That the oxidation process is, at least in part, catalyzed by the enzyme, catalase, explains the effects of ethanol, aminotriazole and the state of acatalasemia on the metabolism of inhaled vapor in man and animals. The formation of covalent bonds between metal cations and the carbon atom usually greatly modifies the biological properties of the metal. Methylarsenic and methylmercury compounds both differ from the inorganic forms in accumulation in animals.

Animals↗
PubMed2006

Synthesis and reactivity of the imido analogues of the uranyl ion.

Addition of 1.5 equiv of I2 to a THF solution of UI3(THF)4, containing either 6 equiv of tBuNH2 or 2 equiv of RNH2 (R = Ph, 3,5-(CF3)2C6H3, 2,6-(iPr)2C6H3) and 4 equiv of NEt3, generates orange solutions containing U(NtBu)2I2(THF)2 (1) or U(NAr)2I2(THF)3 (Ar = Ph, 2; 3,5-(CF3)2C6H3, 3; 2,6-(iPr)2C6H3, 4), respectively, all of which can be isolated in good yields. Alternatively, 1 can be prepared by reaction of uranium metal with 3 equiv of I2 and 6 equiv of tBuNH2, also in good yield. Complexes 1-4 have been characterized by X-ray crystallography, and each of these complexes exhibits linear N-U-N linkages and short U-N bonds. Using density functional theory simulations of complexes 1 and 2, two triple bonds between the metal center and the nitrogen ligands were identified. Complexes 1 and 2 readily react with neutral Lewis bases such as pyridine or Ph3PO to form U(NR)2I2(L)2 (R = tBu, L = py, 5; Ph3PO, 7; R = Ph, L = py, 6; Ph3PO, 8), and with PMe3 to form U(NR)2I2(THF)(PMe3)2 (R = tBu, 9; Ph, 10). The solid-state molecular structures of 5, 7, and 9 have been determined by X-ray crystallography, and these complexes, like their parent compounds, exhibit linear N-U-N angles and short U-N bonds. Complexes 1 and 2 also react with AgOTf in CH2Cl2, forming U(NR)2(OTf)2(THF)3 (R = tBu, 11; Ph, 12) after recrystallization from THF. Crystals of 12 grown from CH2Cl2 were found to contain a dimer, [U(NPh)2(OTf)2(THF)2]2, a complex possessing bridging triflate groups.

Journal Article↗
PubMed2005

Uncertainties in electron-absorbed fractions and lung doses from inhaled beta-emitters.

The computer code LUDUC (Lung Dose Uncertainty Code), developed at the University of Florida, was originally used to investigate the range of potential doses from the inhalation of either plutonium or uranium oxides. The code employs the ICRP Publication 66 Human Respiratory Tract model; however, rather than using simple point estimates for each of the model parameters associated with particle deposition, clearance, and lung-tissue dosimetry, probability density functions are ascribed to these parameters based upon detailed literature review. These distributions are subsequently sampled within LUDUC using Latin hypercube sampling techniques to generate multiple (e.g., approximately 1,000) sets of input vectors (i.e., trials), each yielding a unique estimate of lung dose. In the present study, the dosimetry component of the ICRP-66 model within LUDUC has been extended to explicitly consider variations in the beta particle absorbed fraction due to corresponding uncertainties and biological variabilities in both source and target tissue depths and thicknesses within the bronchi and bronchioles of the thoracic airways. Example dose distributions are given for the inhalation of absorption Type S compounds of 90Sr (Tmax = 546 keV) and 90Y (Tmax = 2,284 keV) as a function of particle size. Over the particle size range of 0.001 to 1 microm, estimates of total lung dose vary by a factor of 10 for 90Sr particles and by a factor of 4 to 10 for 90Y particles. As the particle size increases to 10 microm, dose uncertainties reach a factor of 100 for both radionuclides. In comparisons to identical exposures scenarios run by the LUDEP 2.0 code, Reference Man doses for inhaled beta-emitters were shown to provide slightly conservative estimates of lung dose compared to those in this study where uncertainties in lung airway histology are considered.

Administration, Inhalation↗
PubMed1988

Presynaptic action of uranyl nitrate on the phrenic nerve-diaphragm preparation of the mouse.

The contraction of the diaphragm of the mouse, induced by nerve stimulation, can be potentiated by uranyl nitrate [UO2(NO3)2, 0.2-0.8 mM]. At concentrations greater than 0.8 mM, uranyl nitrate also directly enhanced the contractions induced by electrical stimulation of muscle. The effects of uranyl nitrate in potentiating the twitch were augmented by low calcium (0.25-0.5 mM) and antagonized by high levels of calcium (5-10 mM). Electrophysiological studies on the effects of uranyl nitrate on the diaphragm in the mouse have revealed that the frequency of miniature end-plate potentials (MEPP) but not the amplitude was increased; the amplitude and quantal content of end-plate potential (EPPs) were also markedly increased by uranyl nitrate. The most peculiar phenomenon induced by uranyl nitrate was that repetitive end-plate potentials, as well as repetitive action potentials, of the diaphragm of the mouse were triggered by single nerve stimulation in the presence of uranyl nitrate. The duration of muscle action potentials was significantly prolonged. Recordings of the evoked compound action potentials from nerve axons showed that uranyl nitrate not only prolonged the duration of the axonal compound action potentials but also induced antidromic activity with a single stimulation. This latter effect of uranyl nitrate was blocked by d-tubocurarine. All of these findings suggest that uranyl nitrate potentiated the contractions of the diaphragm of the mouse, possibly through the activation of stimulus-activated repetitive discharges which resulted in the repetitive end-plate potentials and muscle action potentials.

Action Potentials↗
PubMed2004

Synthesis and crystal structure of tetra- and hexanuclear uranium(IV) complexes with hexadentate compartmental Schiff-base ligands.

Treatment of UCl4 with the hexadentate Schiff bases H2Li in thf gave the expected [ULiCl2(thf)] complexes [H2Li=N,N'-bis(3-methoxysalicylidene)-R and R = 2,2-dimethyl-1,3-propanediamine (i= 1), R = 1,3-propanediamine (i= 2), R = 2-amino-benzylamine (i= 3), R = 2-methyl-1,2-propanediamine (i= 4), R = 1,2-phenylenediamine (i= 5)]. The crystal structure of [UL4Cl2(thf)] (4) shows the metal in a quite perfect pentagonal bipyramidal configuration, with the two Cl atoms in apical positions. Reaction of UCl4 with H4Li in pyridine did not afford the mononuclear products [U(H2Li)Cl2(py)x] but gave instead polynuclear complexes [H4Li=N,N'-bis(3-hydroxysalicylidene)-R and R = 1,3-propanediamine (i= 6), R = 2-amino-benzylamine (i= 7) or R = 2-methyl-1,2-propanediamine (i= 8)]. In the presence of H4L6 and H4L7 in pyridine, UCl4 was transformed in a serendipitous and reproducible manner into the tetranuclear U(iv) complexes [Hpy]2[U4(L6)2(H2L6)2Cl6] (6a) and [Hpy]2[U4(L7)2(H2L7)2Cl6][U4(L7)2(H2L7)2Cl4(py)2] (7), respectively. Treatment of UCl4 with [Zn(H2L6)] led to the formation of the neutral compound [U4(L6)2(H2L6)2Cl4(py)2] (6b). The hexanuclear complex [Hpy]2[U6(L8)4Cl10(py)4] (8) was obtained by reaction of UCl4 and H4L8. The centrosymmetric crystal structures of 6a.2HpyCl.2py, 6b.6py, 7.16py and 8.6py illustrate the potential of Schiff bases as associating ligands for the design of polynuclear assemblies.

Journal Article↗
PubMed2002

Synthesis and characterization of uranyl compounds with iminodiacetate and oxydiacetate displaying variable denticity.

Eight uranyl compounds containing the dicarboxylate ligands iminodiacetate (IDA) or oxydiacetate (ODA) have been characterized in the solid state. The published polymeric structures for [UO(2)(C(4)H(6)NO(4))(2)] and [UO(2)(C(4)H(4)O(5))](n) have been confirmed, while Ba[UO(2)(C(4)H(5)NO(4))(2)] x 3H(2)O, [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)][UO(2)(C(4)H(4)O(5))(2)] [orthorhombic space group Pnma, a = 10.996(5) A, b = 21.42(1) A, c = 8.700(3) A, Z = 4], and [C(2)H(5)NH(2)(CH(2))(2)NH(2)C(2)H(5)][UO(2)(C(4)H(4)O(5))(2)] [monoclinic space group P2(1)/n, a = 6.857(3) A, b = 9.209(5) A, c = 16.410(7) A, beta = 91.69(3), Z = 2] contain monomeric anions. The distance from the uranium atom to the central heteroatom (O or N) in the ligand varies. Crystallographic study shows that U-heteroatom (O/N) distances fall into two groups, one 2.6-2.7 A in length and one 3.1-3.2 A, the latter implying no bonding interaction. By contrast, EXAFS analysis of bulk samples suggests that either a long U-heteroatom (O/N) distance (2.9 A) or a range of distances may be present. Three possible structural types, two symmetric and one asymmetric, are identified on the basis of these results and on solid-state (13)C NMR spectroscopy. The two ligands in the complex can be 1,4,7-tridentate, giving five-membered rings, or 1,7-bidentate, to form an eight-membered ring. (C(4)H(12)N(2))[(UO(2))(2)(C(4)H(5)NO(4))(2)(OH)(2)] x 8H(2)O [monoclinic space group P2(1)/a, a = 7.955(9) A, b = 24.050(8) A, c = 8.223(6) A, beta = 112.24(6), Z = 2], (C(2)H(10)N(2))[(UO(2))(2)(C(4)H(5)NO(4))(2)(OH)(2)] x 4H(2)O, and (C(6)H(13)N(4))(2)[(UO(2))(2)(C(4)H(4)O(5))(2)(OH)(2)] x 2H(2)O [monoclinic space group C2/m, a = 19.024(9) A, b = 7.462(4) A, c = 2.467(6) A, beta = 107.75(4), Z = 4] have a dimeric structure with two capping tridentate ligands and two mu(2)-hydroxo bridges, giving edge-sharing pentagonal bipyramids.

Journal Article↗
PubMed2006

U(IV) chalcogenolates synthesized via oxidation of uranium metal by dichalcogenides.

Treatment of uranium metal with dichalcogenides in the presence of a catalytic amount of iodine in pyridine affords molecular U(IV) chalcogenolates that do not require stabilizing ancillary ligands. Oxidation of U(0) by PhEEPh yields monomeric seven-coordinate U(EPh)4(py)3 (E = S(1), Se(2)). The dimeric eight-coordinate complexes [U(EPh)2(mu2-EPh)2(CH3CN)2]2 (E = S(3), Se(4)) are obtained by crystallization from solutions of 1 and 2 dissolved in acetonitrile. Oxidation of U(0) by pySSpy and crystallization from thf yields nine-coordinate U(Spy)4(thf) (5). Incorporation of elemental selenium into the oxidation of U(0) by PhSeSePh results in the isolation of [U(py)2(SePh)(mu3-Se)(mu2-SePh)]4.4py (6), a tetrameric cluster in which each U(IV) ion is eight-coordinate and the U4Se4 core forms a distorted cube. The compounds were analyzed spectroscopically and the single-crystal X-ray structures of 1 and 3-6 were determined. The isolation of 1-6 represents six new examples of actinide chalcogenolates and allows insight into the nature of "hard" actinide ion-"soft" chalcogen donor interactions.

Journal Article↗