Reduction of the photoexcited uranyl ion by water

Photooxidation of water by the uranyl ion was studied. Solutions of uranyl in 0.01–4.0M H₂SO₄, HClO₄, or 0.1–1.0M Na₂SO₄ and NaClO₄ containing “lacunary” heteropolytungstate (HPT) K₁₀P₂W₁₇O₆₁ or K₈SiW₁₁O₃₉ were irradiated with a nitrogen laser, a mercury or xenon lamp, or visible light. Spectrophotometric analysis showed that the irradiation results in the accumulation of U^IV. Simultaneously the formation of H₂O₂ proceeds. The quantum yield Φ of the reaction increases as the concentration of the acid or salt increases. For aerated solutions of 1M H₂SO₄ or 1M HClO₄, irradiation by light with λ=337.1 Φ is close to (1.5–2)·10⁻³. The irradiation of solutions with pH −4 for many days leads to an almost quantitative transformation of UO₂ ²⁺ into U^IV. When the irradiation was carried out in the absence of HPA, U^IV was not detected, although hydrogen peroxide was observed in the solution. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 2, pp. 282–287, February, 2000.     

Synthesis and Structure of New Aminouracilindolones

Russian Journal of General Chemistry - New derivatives of aminouracilindolone have been prepared and their structure has been studied. The reaction of 2-chloro-1H-indole-3-carbaldehyde and its...     

Synthesis and Crystal Structure of 2D Coordination Polymer {[Cu(dps)2(DMSO)2](ClO4)2}n Based on 4,4′-Dipyridyl Sulfide

A new coordination polymer {[Cu(dps)₂(DMSO)₂](ClO₄)2}_n has been synthesized basing on 4,4′- dipyridyl sulfide. The structure of the obtained complex has been studied by single-crystal X-ray diffraction analysis.

     

Synthesis and structure of 2,6-diazidotrichloropyridine <Emphasis Type="Italic">N</Emphasis>-oxide

Pentachloropyridine N-oxide readily reacted with sodium azide in aqueous acetone at room temperature to produce 2,6-diazidotrichloropyridine N-oxide in high yield. The molecular and crystalline structures of the product were studied in detail by X-ray analysis and quantum-chemical calculations. Unusual geometric parameters of the azido groups and reactivity of the diazide were rationalized by the presence of strong intramolecular contacts N … O with an energy of ∼6.1 kcal/mol.     

Benzene adsorption and protonation in perfluorosulfonic membrane

Benzene adsorption in a perfluorosulfonic membrane was performed through deep dehydration of the latter over the phosphoric anhydride. The subsequent UV irradiation is accompanied by a gradual transition of the benzene ??-complexes in the protonated form C₆H ₇ ⁺ that allows us to consider the perfluorosulfonic membrane as a solid superacids. The photoexcitation on the absorption band of adsorbed carbonium ion causes its fluorescence in the region of 450?C600 nm.     

The optical limitation effect and features of luminescence kinetics in hybrid nanosystems with CdSe/ZnS quantum dots and organic agents

The optical limitation effect in three-component systems formed in colloidal solutions of semiconductor CdSe/ZnS quantum dots with participation of fullerene C₆₀ and perylene, has been experimentally investigated. The first and second harmonics of a YAG:Nd³⁺ laser operating in the single-shot mode with a pulse duration of 7 ns and laser pulses subjected to stimulated Brillouin scattering (SBS)-stimulated Raman scattering (SRS) compression with a duration of about 20 ps near 560 nm have been used as radiation sources. It is shown that the optical limitation efficiency in the systems studied is determined by electron transfer. This is confirmed by the analysis of luminescence quenching.     

Metal alloys and carbon nanomaterials as potential hydrogen storage materials

Comparative analysis of metals (as well as their alloys and intermetallic compounds) and various carbon nanomaterials as working substances for hydrogen storage and transportation systems has been performed. It has been shown that, because of the fundamental difference in the nature of interaction with hydrogen of these two large classes of compounds, the fields of their application (as well as their performance) are certainly different. Some theoretical calculations and concepts concerning the hydrogen capacity of the materials under consideration have been critically surveyed.     

3-Ethoxy-2,2-bis(methoxy-<Emphasis Type="Italic">NNO</Emphasis>-azoxy)propan-1-ol. Synthesis and X-ray diffraction analysis

Reaction of bis(methoxy-NNO-azoxy)methane with formaldehyde in ethanol gives 3-ethoxy-2,2-bis(methoxy-NNO-azoxy)propan-1-ol as a minor product along with target 2,2-bis(methoxy-NNO-azoxy)ethanol. The structure of the former was confirmed by the counter synthesis and X-ray diffraction analysis.     

Simulation of thermodynamic properties of borosilicate melts containing alkaline-earth metal oxides

The possibility for simulation of thermodynamic parameters of MO-B₂O₃-SiO₂ melts (M = Ca, Sr, Ba) in terms of the UNIQUAC associated solution theory was demonstrated using the experimental data obtained previously by high-temperature mass spectrometry (1650–1800 K). The calculated numbers of different bonds formed in the examined melts were found to correlate with the deviations of their thermodynamic parameters from ideality.     

Thermodynamic properties of the system MgO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> melts

Vaporization processes of melts of the system MgO-B₂O₃ at 1640 K were studied by high-temperature mass spectrometry, and thermodynamic properties (activity, chemical potentials of MgO and B₂O₃, and also the corresponding excess values) were determined. Considerable negative deviations from the ideal behavior in the melts of the studied system are observed. The termodynamic properties of the system MgO-B₂O₃ can be calculated within the framework of the lattice theory of associated solutions.