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1.
A dramatic difference in the ability of the reducing An III center in AnCp 3 (An=U, Np, Pu; Cp=C 5H 5) to oxo‐bind and reduce the uranyl(VI) dication in the complex [(UO 2)(THF)(H 2L)] (L=“Pacman” Schiff‐base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At‐first contradictory electronic structural data are explained by combining theory and experiment. Complete one‐electron transfer from Cp 3U forms the U IV‐uranyl(V) compound that behaves as a U V‐localized single molecule magnet below 4 K. The extent of reduction by the Cp 3Np group upon oxo‐coordination is much less, with a Np III‐uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest Np IVU V but single‐crystal X‐ray diffraction and SQUID magnetometry suggest a Np III‐U VI assignment. DFT‐calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The Pu III–U VI interaction is too weak to be observed in THF solvent, in agreement with calculated predictions. 相似文献
2.
A dramatic difference in the ability of the reducing An III center in AnCp 3 (An=U, Np, Pu; Cp=C 5H 5) to oxo‐bind and reduce the uranyl(VI) dication in the complex [(UO 2)(THF)(H 2L)] (L=“Pacman” Schiff‐base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At‐first contradictory electronic structural data are explained by combining theory and experiment. Complete one‐electron transfer from Cp 3U forms the U IV‐uranyl(V) compound that behaves as a U V‐localized single molecule magnet below 4 K. The extent of reduction by the Cp 3Np group upon oxo‐coordination is much less, with a Np III‐uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest Np IVU V but single‐crystal X‐ray diffraction and SQUID magnetometry suggest a Np III‐U VI assignment. DFT‐calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The Pu III–U VI interaction is too weak to be observed in THF solvent, in agreement with calculated predictions. 相似文献
3.
The reduction of U VI uranyl halides or amides with simple Ln II or U III salts forms highly symmetric, linear, oxo‐bridged trinuclear U V/Ln III/U V, Ln III/U IV/Ln III, and U IV/U IV/U IV complexes or linear Ln III/U V polymers depending on the stoichiometry and solvent. The reactions can be tuned to give the products of one‐ or two‐electron uranyl reduction. The reactivity and magnetism of these compounds are discussed in the context of using a series of strongly oxo‐coupled homo‐ and heterometallic poly(f‐block) chains to better understand fundamental electronic structure in the f‐block. 相似文献
4.
A new organic–inorganic hybrid (H 2en) 2[[Cu(en) 2]As IIIAs VMo VI9O 34]·6H 2O ( 1), containing a 1-D helical chain based on the trivacant monocapped Keggin arsenomolybdate and the copper complex linker {[Cu(en) 2][As IIIAs VMo VI9O 34]} n4n? (en = ethylenediamine), has been synthesized and characterized by IR spectra, TG analyses, single-crystal X-ray diffraction, and high-resolution electrospray ionization mass spectrometry (ESI-MS). Large voids are observed and a 1-D chain containing repeated (H 2O) 8 water units from lattice water molecules is formed along the a axis in the crystal structure. The high-resolution ESI-MS shows that the intact framework [Cu(en) 2][As IIIAs VMo VI9O 34] 4? exists in solution. 相似文献
5.
Summary The polarography of hexavalent uranium in sulphuric acid solutions of different concentrations and solutions containing sodium sulphate is studied. In 0.01 M H 2SO 4 three waves are obtained corresponding to the successive reduction of U VI to U V, U V to U IV and U IV to U III. The second and third waves intermingle by increasing the H 2SO 4 concentration up to 0.055 M or by adding Na 2SO 4 or sulphosalicylic acid. In 0.25 M H 2SO 4 or in the presence of EDTA the second wave shifts to less negative potentials and intermingles with the first wave, forming a single wave along which reduction of U VI gives a mixture of U V and U IV. The diffusion current of this wave increases up to 1 M H 2SO 4 and then decreases above this acidity. The diffusion current measured at –0.6 V is proportional to the U VI concentration in the presence of 0.25–0.6 M H 2SO 4. This is not the case in the presence of EDTA. The proportionality is better at lower than at higher acidity.Part I: See Z. analyt. Chem. 174, 4 (1960). 相似文献
6.
Summary Solvent extraction of uranium-sodium diethyldithiocarbamate with ethylmethyl ketone and separation from titanium, zirconium, thorium, lanthanum and cerium has been described. It has been found that 11.75 to 47.00 mg of uranium can be extracted from a binary mixture containing 4.78 to 19.04 mg of titanium, 9.12 to 36.48 mg of zirconium, 116.0 to 460.0 mg of thorium, 6.95 to 27.8 mg of lanthanum or 7.06 to 28.24 mg of cerium at pH 3.0. The pH range between which the separations may be carried out successfully is 2.0 to 3.5. The following cations interfere in the separations: Cu II, Fe III, Co II, Bi III, Ni II, Cr VI, Te IV, Se IV, Ag I, Hg II, As III, Sn IV, Pb IV, Cd II, Mo VI, Mn II, V V, Zn II, In III, Tl I, W VI, Os VIII and Nb V.
Zusammenfassung Uran kann durch Extraktion als Diäthyldithiocarbamidat mit Methyläthylketon von Ti, Zr, Th, La oder Ce getrennt werden. Der günstigste pH-Bereich liegt zwischen 2,0 und 3,5. Die Trennungen wurden mit folgenden Mengen durchgeführt: U (11,75–47,00 mg); Ti (4,78 bis 19,04 mg), Zr (9,12–36,48 mg) Th (116,0–460,0 mg), La (6,95–27,8 mg), Ce (7,06–28,24 mg). Folgende Ionen verursachen Störungen: CuII, FeIII, CoII, BiIII, NiII, CrVI, TeIV, SeIV, AgI, HgII, AsIII, SnIV, PbIV, CdII, MoVI, MnII, VVI, ZnII, InIII, TlI, WVI, OsVIII sowie NbV. 相似文献
7.
Reduction of uranyl(VI) to U V and to U IV is important in uranium environmental migration and remediation processes. The anaerobic reduction of a uranyl U VI complex supported by a picolinate ligand in both organic and aqueous media is presented. The [U VIO 2(dpaea)] complex is readily converted into the cis-boroxide U IV species via diborane-mediated reductive functionalization in organic media. Remarkably, in aqueous media the uranyl(VI) complex is rapidly converted, by Na 2S 2O 4, a reductant relevant for chemical remediation processes, into the stable uranyl(V) analogue, which is then slowly reduced to yield a water-insoluble trinuclear U IV oxo-hydroxo cluster. This report provides the first example of direct conversion of a uranyl(VI) compound into a well-defined molecular U IV species in aqueous conditions. 相似文献
8.
Herein we present a new approach for the complete removal of Cr VI species, through reduction of Cr VI to Cr III, followed by adsorption of Cr III. Reduction of chromium from water is an important challenge, as Cr IV is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO 2 membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSf < PSf/TiO 2 < PSf/TiO 2/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr VI to Cr III through electrons and protons donated from OH and NH 2 groups of the CS layer; the reduced Cr III species are adsorbed onto the CS layer via complexation to give chromium-free water. 相似文献
9.
Reduction of uranyl(VI) to U V and to U IV is important in uranium environmental migration and remediation processes. The anaerobic reduction of a uranyl U VI complex supported by a picolinate ligand in both organic and aqueous media is presented. The [U VIO 2(dpaea)] complex is readily converted into the cis‐boroxide U IV species via diborane‐mediated reductive functionalization in organic media. Remarkably, in aqueous media the uranyl(VI) complex is rapidly converted, by Na 2S 2O 4, a reductant relevant for chemical remediation processes, into the stable uranyl(V) analogue, which is then slowly reduced to yield a water‐insoluble trinuclear U IV oxo‐hydroxo cluster. This report provides the first example of direct conversion of a uranyl(VI) compound into a well‐defined molecular U IV species in aqueous conditions. 相似文献
10.
Xe compounds, XeF 2, Na 4XeO 6, and XeO 3, were used to oxidize Am III in carbonate and bicarbonate aqueous solutions. XeF 2 and XeO 3 may be used to obtain Am IV in solutions, whereas Na 4XeO 6 oxidizes Am III into Am IV+An V+Am VI or into Am VI if present in excess. XeO 3 reacts with Am III to give Am IV only under UV irradiation.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 953–954, May, 1994. 相似文献
11.
The complex formation with CH 3O ? of As III, Sb III, Ge IV, Nb IV, Se IV, Te IV, Ti IV, Sn IV and Mo V has been investigated in absolute methanolic solutions containing (CH 3) 4NCl, LiCl, or Lithiumtosylate (μ = 1; 20.0°) by means of pH-titrations. The relations between the stoichiometry of the reactions and the shape of the buffer regions, as well as the concentration-dependance of these buffer regions are discussed. 相似文献
12.
Selective oxidation of galacturonic residues of oligo and polyuronic acids by Cr VI affords CO 2/HCO 2H, oxidized uronic acid, and Cr III as final redox products. Kinetic studies show that the redox reaction proceeds through a mechanism combining Cr VI → Cr IV → Cr II and Cr VI → Cr IV → Cr III pathways. The mechanism is supported by the observation of free radicals, CrO 22+ and Cr V as reaction intermediates. The EPR spectra show that five- and six coordinated oxo-Cr V intermediates are formed. Penta-coordinated oxo-Cr V species are present at any [H +], whereas hexa-coordinated ones are only observed at pH <1. At low pH Cr V predominating species are coordinated by carboxylate groups and O ring ( giso = 1.9783/5). At pH 7.5, the predominating ones are those coordinated by alcoholate groups of the ligand ( giso = 1.9800). Polygal can reduce Cr VI and efficiently trap Cr III. This behaviour represents an interesting model for the study of biomaterials, which possess a high proportion of polygal, in order to remove chromium from polluted waters. 相似文献
13.
Study on the stoichiometry and affinity of the arsenicals bound to HSA is an important step toward a better understanding of arsenic toxic effects. After incubation of As III or As V with HSA at the physiological conditions (pH 7.43 and 37 °C), the free arsenicals and arsenic-HSA complexes were separated and detected by the combined techniques of microdialysis and liquid chromatography with hydride generation atomic fluorescence spectroscopy (MD–LC–HGAFS). The decrease of As III peak response rather than As V indicated that HSA reacted with As III but not As V. The binding plots indicated that the binding between HSA and As III was in Scatchard pattern when the concentration ratios of As III to HSA were ≤1:1. The strong binding sites ( n 1) were 1.6 and the stability constant ( K 1) was 1.54 × 10 6 M ?1. When the concentration ratios of As III to HSA were >1:1, the binding was in Plasvento pattern with the stability constant K 2 ? 0 and no specific binding of As III with HSA. On the contrary, As V did not show binding with HSA. The results showed that As III reacted with HSA more readily than As V, which provides a chemical basis for arsenic toxicity. 相似文献
14.
It is shown that U VO 2+ ions can reside at U VIO 22+ lattice sites during mild reduction and crystallization process under solvothermal conditions, yielding a complicated and rare mixed‐valent uranium phosphonate compound that simultaneously contains U IV, U V, and U VI. The presence of uranium with three oxidation states was confirmed by various characterization techniques, including X‐ray crystallography, X‐ray photoelectron, electron paramagnetic resonance, FTIR, UV/Vis‐NIR absorption, and synchrotron radiation X‐ray absorption spectroscopy, and magnetism measurements. 相似文献
15.
Photocatalytic Systems. XLIV. On the Intervalence Charge Transfer Behaviour of Ion Pairs of Octacyanomolybdate [Mo(CN) 8] 4? ions are forming coloured ion pairs with Fe III, Cu II, U VIO 2, and V IVO, the long-wavelength absorption band of which could be assigned to an intervalence charge-transfer transition. From the solvent dependence of the IT band, interionic distances could be estimated. 相似文献
16.
An anion exchange HPLC-ICP-MS procedure allowing the simultaneous multielemental speciation analysis of arsenic, selenium, antimony and tellurium has been developed. Four arsenic species (As III, As V, monomethylarsonic acid and dimethylarsinic acid), two selenium species (Se IV and Se VI) may be determined in a single run as well as one antimony (Sb V) and one tellurium species (Te VI). Alternatively Sb and/or Te may be used as internal standards for As and Se speciation studies. Optimisation of ICP-MS conditions led to satisfactory relative (0.01 (Sb V) to 1.8 (Se VI) ng ml −1) and absolute detection limits (1–180 pg). Reproducibility ranged from 3.1 to 5.6% and the linearity was verified in the 0–200 ng ml −1 range. 相似文献
17.
Study on the stoichiometry and affinity of the arsenicals bound to HSA is an important step toward a better understanding of arsenic toxic effects. After incubation of AsIII or AsV with HSA at the physiological conditions (pH 7.43 and 37 °C), the free arsenicals and arsenic-HSA complexes were separated and detected by the combined techniques of microdialysis and liquid chromatography with hydride generation atomic fluorescence spectroscopy (MD–LC–HGAFS). The decrease of AsIII peak response rather than AsV indicated that HSA reacted with AsIII but not AsV. The binding plots indicated that the binding between HSA and AsIII was in Scatchard pattern when the concentration ratios of AsIII to HSA were ≤1:1. The strong binding sites (n
1) were 1.6 and the stability constant (K
1) was 1.54 × 106 M−1. When the concentration ratios of AsIII to HSA were >1:1, the binding was in Plasvento pattern with the stability constant K
2 ≅ 0 and no specific binding of AsIII with HSA. On the contrary, AsV did not show binding with HSA. The results showed that AsIII reacted with HSA more readily than AsV, which provides a chemical basis for arsenic toxicity. 相似文献
18.
Electrochemiluminescence (ECL) accompanying the reduction of uranyl ions on a platinum cathode in sulfuric solutions in the
presence of XeO 3 was observed and studied. At early stages of the electrolysis (at 0.34<φ<0.62 V), the chemiluminescence reaction U V+XeO 3 contributes mainly to the luminescence intensity, whereas at φ<0.32 V, the contribution of the reaction U IV+XeO 3 predominates. The transfer coefficient for the primary electrochemical stage, formation of U V, was estimated: α=0.46−0.54. The high sensitivity of ECL to the state of the electrode surface is explained by the fact that
the reduction of U VI occurs on the most active sites only. the background chemiluminescence reactions, among which U V+O 2 and U V+H 2O 2 can be distinguished, were considered, and their contributions to ECL were determined.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1928–1934, October, 1999. 相似文献
19.
Actinoid tetroxide molecules AnO 4 (An = Ac – Cm) are investigated with the ab initio density matrix renormalization group (DMRG) approach. Natural orbital shapes are used to read out the oxidation state (OS) of the f-elements, and the atomic orbital energies and radii are used to explain the trends. The highest OSs reveal a “volcano”-type variation: For An = Ac – Np, the OSs are equal to the number of available valence electrons, that is, Ac III, Th IV, Pa V, U VI, and Np VII. Starting with plutonium as the turning point, the highest OSs in the most stable AnO 4 isomers then decrease as Pu V, Am V, and Cm III, indicating that the 5f-electrons are hard to be fully oxidized off from Pu onward. The variations are related to the actinoid contraction and to the 5f-covalency characteristics. Combined with previous work on OSs, we review their general trends throughout the periodic table, providing fundamental understanding of OS-relevant phenomena. 相似文献
20.
The 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) aqueous complex of U IV with H 2O, OH −, and F − as axial ligands was studied by using UV/Vis spectrophotometry, ESI-MS, NMR spectroscopy, X-ray crystallography, and electrochemistry. The U IV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The U IV/U III redox couple was found to be quasi-reversible for the complex with both axially bonded H 2O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride renders the irreversible one-electron U V/U IV oxidation of the [U IV(DOTA)(H 2O)] complex quasi-reversible, which suggests the formation of the short-lived pentavalent form of the complex, an aqueous non-uranyl chelated U V cation. 相似文献
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