PuO3和PuO+3的分子结构与分子光谱

用相对论有效原子实势RECP和密度泛函(B3LYP, BHANDHLYP)、HF方法对PuO3的分子结构与分子光谱进行了研究.计算比较了C2v, D3h, C3v等构型以及计算方法等对PuO3分子能量和平衡结构的影响,结果表明中性的PuO3能够稳定存在,基态结构为C2v,状态为7B1 (B3LYP R1＝0.19143 nm, R2(＝R3)＝0.22057 nm, ∠OPuO＝102.2108°),比较而言PuO3分子还可能存在D3h结构的亚稳态7A2″,不存在稳定的C3v结构的PuO3分子.计算还同时首次给出了不同多重性的PuO3分子及其一价正离子PuO+3完整的能量、平衡几何结构、光谱数据、电荷布居、自旋密度、极化率与电偶极矩等系列数据.     

Structural characterization of the first hydrothermally synthesized plutonium compound,PuO2(IO3)2 x H2O

Single crystals of PuO2(IO3)2 x H2O were synthesized under hydrothermal conditions (180 degrees C) representing the first structurally characterized transuranium iodate.     

ChemInform Abstract: Ab Initio Quantum Chemical Calculations on Uranyl UO2+ 2, Plutonyl PuO2+ 2, and Their Nitrates and Sulfates.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Complexometric determination of thorium in ThO2−PuO2

A method based on the complexometric titration of thorium using ethylene diaminetetra-acetic acid (EDTA) as complexant has been developed for the determination of thorium in thorium-plutonium solution without resorting to prior separation of plutonium. Plutonium in the form of Pu(VI) does not affect the thorium determination when present up to 10% in thorium—plutonium solution. For oxidation of plutonium to Pu(VI), HClO₄ or AgO was used. HClO₄ is preferred. The thorium values obtained without prior separation of plutonium are compared with those obtained after separating plutonium by anion exchange technique. A precision of ±0.5% has been obtained for 5–10 mg of thorium in the aliquot.     

The heat of formation of gaseous PuO(2)2+ from relativistic density functional calculations

Using a set of model reactions, we estimated the heat of formation of gaseous PuO2(2+) from quantum-chemical reaction enthalpies and experimental heats of formation of reference species. To this end, we carried out relativistic density functional calculations on the molecules PuO(2)2+, PuO2, PuF6, and PuF4. We used a revised variant (PBEN) of the Perdew-Burke-Ernzerhof gradient-corrected exchange-correlation functional, and we accounted for spin-orbit interaction in a self-consistent fashion. As open-shell Pu species with two or more unpaired 5f electrons are involved, spin-orbit interaction significantly affects the energies of the model reactions. Our theoretical estimate for the heat of formation DeltafH degree 0(PuO2(2+),g), 418+/-15 kcal mol-1, evaluated using plutonium fluorides as references, is in good agreement with a recent experimental result, 413+/-16 kcal mol-1. The theoretical value connected to the experimental heat of formation of PuO2(g) has a notably higher uncertainty and therefore was not included in the final result.     

Theoretical sstudy on the Co2+OH2+/Co3+OH2+ electron transfer reactivity

This paper presents a contact distance dependence analysis scheme and an abinitio calculation application for the electron transfer (ET) reactivity of Co²⁺OH₂/Co³⁺OH² reacting pair. The applicability of these schemes and the corresponding models has been discussed. The contact distance (R _CoCo) dependence of the relevant quantities has been analyzed. The results indicate that the activation energy from the accurate PES method agrees well with that from the anharmonic potential method, and they are obviously better than that from the harmonic potential method. The pair distribution function varies from 10^?2 to 10^?5 along withR _CoCo changing from 1.20 to 0.35 nm. The coupling matrix element exponentially decays along with the increase ofR _CoCo, and the effective electronic coupling requiresR _CoCo smaller than 0.75 nm. In the range from 0.50 to 0.75 nm forR _CoCo, the corresponding electronic transmission coefficient falls within 1.0—10^?6. The local ET rate also exponentially decays along with the increase ofR _CoCo due to the electronic factor. Since the contribution from the pair distribution function to the total ET rate is an inverse measure of that from the electronic factor, the variation of the spherically averaged local ET rate along withR _CoCo exhibits a parabola with a maximum at 0.50 nm ofR _CoCo. This maximum is close to the overall observed ET rate value. For this mono-hydrated transition metal ionic system, the ET rate generally is about 10⁶ L·mol^?1·s^?1 in gaseous process. Further, since it is impossible to experimentally determine the structures and their PESs of these hydrated systems, especially for the unstable intermediate species,ab initio calculations can play an effective auxiliary role in discussing the ET reactivities of these kinds of reacting systems.     

In vitro lung dissolutions rates for PuO2

Summary The lung dissolution rates for PuO₂ were determined using a 100 day in vitro experiment. A very small amount of the PuO₂ rapidly dissolved with a half-time of approximately 10 days, while the majority of the material (>99%) dissolved with a half-time of approximately 5 ^. 10⁵ days. This dissolution half time is significantly longer than what is recommended by the ICRP, and would result in higher calculated doses for inhalation intakes of PuO₂ than those currently estimated by the ICRP 66 human respiratory tract model for radiological protection.     

Thermal reactivity and1H NMR spectroscopy of Sr1−x H2x V6O16 · aq

The results of study of the thermal reactivity and¹H NMR spectroscopy of solid polyvanadates of general formula Sr_1?x H_2x V₆O₁₆ · aq are presented. Compounds withx=0 (a),x ∈ (0.3–0.6) (b) andx=1 (c) were studied. The protons are bonded in V - OH (b, c) and V - O ... H (a, b, c) groups, in H₂O molecules (a, b, c) and in H₂O ... H₂O systems (a, b, c). Dehydration of the studied compounds proceeds stepwise. Total dehydration causes decomposition of the original structures and Sr(VO₃)₂, SrV₁₂O₃₀ and V₂O₅ are formed. The results confirm the role of crystal water in stabilizing the structures of the studied compounds.     

Baylis-Hillman adducts in rhodium-catalyzed 1,4-additions: unusual reactivity

In the presence of a rhodium catalyst, unactivated Baylis-Hillman adducts reacted with arylboronic acids to afford trisubstituted alkenes with good yields. This highly efficient reaction (aerobic conditions, low temperature) is believed to proceeds via an unexpected mechanism involving 1,4-addition/beta-hydroxy elimination steps and not pi-allyl type rhodium intermediates.     

Intermolecular proton binding in the presence of a large electric dipole: Ar-tagged vibrational predissociation spectroscopy of the CH3CN x H+ x OH2 and CH3CN x D+ x OD2 complexes

We report Ar-predissociation vibrational spectra of the binary proton-bound hydrates of acetonitrile (AN), AN x H(+) x OH(2) and AN x D(+) x OD(2), in the 600-3800 cm(-1) energy range. This complex was specifically chosen to explore the nature of the intermolecular proton bond when there is a large difference between the electric dipole moments of the two tethered molecules. Sharp, isotope-dependent bands in the vicinity of 1000 cm(-1) are traced to AN x H(+) x OH(2) vibrations involving the parallel displacement of the shared proton along the heavy atom axis, nu(sp)(parallel). These transitions lie much lower in energy than anticipated by a recently reported empirical trend which found the nu(sp)(parallel) fundamentals to be strongly correlated with the difference in proton affinities (DeltaPA) between the two tethered molecules (Roscioli et al., Science, 2007, 316, 249). The different behavior of the AN x H(+) x OH(2) complex is discussed in the context of the recent theoretical prediction (Fridgen, J. Phys. Chem A., 2006, 110, 6122) that a large disparity in dipole moments would lead to such a deviation from the reported (DeltaPA) trend.     

RNA GG x UU motif binds K+ but not Mg2+

A hairpin model of the group I intron P5b loop was synthesized with [8-13C-7-15N]-guanosine in the GG.UU metal binding site, [7-15N]-guanosine at a nonbinding site, and [3-15N]-uridine. 15N NMR showed specific binding for Co(NH3)63+ and K+, but not for Zn2+, Cd2+, or Mg2+.     

Theoretical investigations of the N2H2+ cation and of its reactivity

Accurate ab initio calculations have been performed in order to investigate both the stable isomers and the reactivity of the N(2)H(2)(+) cation. In addition to the trans-HNNH(+) isomer already observed in the photoelectron studies, a formaldehyde type (isodiazene cation) and H(2)O(2)-like isomers are found. At the coupled cluster level of theory, the isodiazene cation is calculated to be as stable as trans-HNNH(+). We have also studied the reactivity of N(2)H(2)(+) and its implication on the reactive processes involving N(2)/N(2)(+) and H(2)(+)/H(2), H/H(+) and HN(2)(+)/HN(2), and HN and HN(+) by performing suitable one-dimensional cuts of the six-dimensional potential energy functions of the lowest electronic states of H(2)N(2)(+). We have pointed out the crucial role of this tetratomic intermediate cation and the importance of the short range internuclear distances during these processes. In the case of N(2)/N(2)(+) and H(2)(+)/H(2) reactions, we have shown that the initial orientation of the reactants may influence the N(2)H(2)(+) tetratomic intermediate: One can expect to form the trans isomer preferentially if the internuclear axes of the H(2)/H(2)(+) and the N(2)(+)/N(2) molecules are parallel to each other when these diatoms are colliding and after intramolecular isomerization process. However, if the internuclear axes of the diatomics are perpendicular to each other, the isodiazene cation is formed preferentially. Different branching ratios are expected for each collision scheme. These reactive processes are found to involve vibronic, Renner-Teller and spin-orbit couplings between the electronic states of N(2)H(2)(+). These interactions mix these electronic states, leading to the formation of atomic, diatomic, and triatomic species via the decomposition of the N(2)H(2)(+) intermediate complex.     

Ca2-3xLa8+2x□x(SiO4)6O2的合成及其导电性能的研究

The silicate oxyapatites Ca_2-3xLa_8+2x□_x(SiO₄)₆O₂(x=0, 0.17, 0.33, 0.50, 0.67) was synthesized via a sol-gel method at low temperature. The apatite phases have been characterised by X-ray diffraction (XRD), conducting properties was studied by electrical chemistry impedance spectroscopy (EIS). The conductivity of La_9.33□_0.67(SiO₄)₆O₂ is 1.58×10^-3 S·cm^-1 at 700 ℃, it is higher about 4 270 times than that of Ca₂La₈(SiO₄)₆O₂, the activation energy is decreasing from 1.37 eV to 0.84 eV. With cation vacancies increasing,the conducting mechanism is gradually translation from a direct linear pathway free oxygen ion conduction to a curve pathway interstitial oxygen ion conduction. The electrical conductivities is almost independent of the oxygen partial pressure, this suggests that the oxyapatites exhibited almost pure O^2- ion conduction over a wide range of oxygen partial pressure.     

Study on Metronidazole Acid-Base Behavior and Speciation with Ca2+ for Potential Applications in Natural Waters

Metronidazole (MNZ) is an antibiotic widely used for the treatment of various infectious diseases and as an effective pesticide agent for the cultivation of chickens and fish. Its high resistance to purification processes and biological activity has led to the classification of MNZ as an emerging contaminant. A speciation study, aimed to define the acid-base properties of MNZ and its interaction with Ca²⁺, commonly present in natural waters, is reported. The protonation constants of MNZ, as well as the formation constant value of Ca²⁺-MNZ species, were obtained by potentiometric titrations in an aqueous solution, using NaCl as background salt at different ionic strengths (0.15, 0.5, 1 mol L⁻¹) and temperature (15, 25 and 37 °C) conditions. The acid-base behavior and the complexation with Ca²⁺ were also investigated by ¹H NMR and UV-Vis titrations, with results in very good agreement with the potentiometric ones. The dependence of the formation constants on the ionic strength and temperature was also determined. The sequestering ability of MNZ towards Ca²⁺ was defined by the empirical parameter pL_0.5 at different pH and temperature values. The speciation of MNZ simulating sea water conditions was calculated.     

Thermodynamic and Structural Trends in Hexavalent Actinyl Cations: Complexation of Dipicolinic Acid with NpO22+ and PuO22+ in Comparison with UO22+

The complexation of NpO₂²⁺ and PuO₂²⁺ with dipicolinic acid (DPA) has been investigated in 0.1 M NaClO₄ by spectrophotometry, microcalorimetry, and single crystal diffractometry. Formation of 1:1 and 1:2 (metal/ligand molar ratio) complexes of DPA with NpO₂²⁺ and PuO₂²⁺ were identified and the thermodynamic parameters were determined and compared with those of UO₂²⁺. All three hexavalent actinyl cations form strong 1:1 DPA complexes with slightly decreasing but comparable stability constants from UO₂²⁺ to PuO₂²⁺, whereas the stability constants of the 1:2 complexes (log β₂) decrease substantially along the series (16.3 for UO₂L₂^2?, 15.17 for NpO₂L₂^2?, and 14.17 for PuO₂L₂^2? at 25 °C). The enthalpies of complexation for the 1:2 complexes become less exothermic from UO₂L₂^2? (?28.9 kJ mol^?1), through NpO₂L₂^2? (?27.2 kJ mol^?1), and to PuO₂L₂^2? (?22.7 kJ mol^?1). The trends in the thermodynamic parameters are discussed in terms of the effective charge of the cations and the steric constraints in the structures of the complexes. In addition, the features of the absorption spectra, including the wavelength and intensity of the absorption bands, are related to the perturbation of the ligand field and the symmetry of the actinyl complexes.