氨及其氟取代物与氟化氢形成氢键络合物的系列理论研究

采用ａｂ ｉｎｉｔｉｏ方法，在６－３１Ｇ水平上，对ＮＨ３…ＮＦ、ＮＨ２Ｆ…ＨＦ、ＮＦ３…ＨＦ４种氢键络合物的５组构型进行了一系列能量梯度法的构型优化和能量计算，取得到关于这些分子络合物的结构特征，氢键键能与键级，单体电荷迁移量等信息，分析，比较得出了在每种构型下各体系的重要物理量随氟基数的递变规律，并探讨了氟基的诱导效应对上述体系氢键作用的影响。     

Solubility of vinylidene fluoride polymers in supercritical CO2 and halogenated solvents

The cloud‐point behaviors of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐co‐22 mol % hexafluoropropylene) (VDF–HFP₂₂) are reported at temperatures up to 250 °C and pressures up to 3000 bar in supercritical CO₂, CHF₃, CH₂F₂, CHClF₂, CClF₃, CH₃CHF₂, CH₂FCF₃, CHF₂CF₃, and CH₃CClF₂. The molecular weight of PVDF has a smaller effect on the cloud point than the solvent quality. Cloud‐point pressures for both fluoropolymers decrease as the solvent polarizability, polar moment per molar volume, and density increases. However, it is extremely difficult to dissolve either fluoropolymer in CClF₃, which has a large polarizability and a small dipole moment. CO₂ is an effective solvent because it complexes with the C F dipole at low temperatures where energetic interactions fix the phase behavior. In addition, polymer architecture has a strong impact on the cloud‐point pressure. VDF–HFP₂₂ has lower cloud‐point pressures than PVDF in all solvents because it has a larger free volume that promotes facile interactions between the solvent and the polymer segments. Cloud‐point data are also reported for amorphous poly(tetrafluoroethylene‐co‐x mol % 2,2‐bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole) (TFE–PDD_x ; x = 65 and 85) in CO₂. These data provide an interesting comparison to the PVDF–CO₂ and VDF–HFP₂₂–CO₂ systems because TFE–PDD₆₅ and TFE–PDD₈₇ have very high glass‐transition temperatures of 160 and 240 °C, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2832–2840, 2000     

A New Cu, Al Fluoride Disilicate CuAl2F2(Si2O7) and its Relations to Topaz

CuAl₂F₂(Si₂O₇) has been prepared by hydrothermal synthesis and its crystal structure was determined by single crystal X‐ray diffraction: space group Pnma, a = 8.8697(9), b = 14.084(2), c = 4.7553(5) Å, wR₂ = 0.056, R = 0.022. Cu²⁺ shows elongated square pyramidal coordination. Edge‐ and corner‐sharing [AlO₄F₂] octahedra with fluorine atoms in cis position form layers parallel to the ac plane. Along b these layers are linked by Si₂O₇ groups to form a three‐dimensional framework [Al₂F₂(Si₂O₇]^2–. In addition, the [CuO₅] pyramides connect two Al octahedra of neighbouring layers. The crystal structure is discussed as a derivative from topaz structure. The modular (or polysomatic) approach is used for this purpose, and for modelling hypothetical related compounds.     

Pyrolytic synthesis and Eu→Eu reduction process of blue-emitting perovskite-type BaLiF3:Eu thin films

Perovskite-type barium lithium fluoride (BaLiF₃) was synthesized by pyrolysis of metal trifluoroacetates. The reaction temperature necessary for producing a single-phase material was found to be 600°C, which was lower than that for a conventional solid-state reaction or a melting method. Eu-doped BaLiF₃ was also prepared and characterized to examine the suitability of trifluoroacetates for precursors in synthesizing homogeneous complex metal fluoride materials. It was demonstrated that trivalent Eu³⁺, which was used as acetate for a starting material, was reduced to divalent Eu²⁺ in the pyrolysis process of BaLiF₃, as indicated by a broad blue emission due to an allowed 4f⁶5d→4f⁷ transition at 408 nm with a ultraviolet excitation at 254 nm. The concentration quenching of the blue emission occurred at 5 at% of Eu in BaLiF₃, indicating that Eu was homogeneously dispersed in the BaLiF₃ host lattice. Mechanisms of the formation and reduction process of BaLiF₃ were discussed based on pertinent chemical reactions.     

Microcalorimetric studies on the non-competitive inhibition of bovine liver arginase

Two methods, e.g. initial rate method and thermokinetic reduced extent method were presented for studies on non-competitive inhibition. Arginase-catalyzed the hydrolysis of L-arginine toL-ornithine and urea and the inhibition of this reaction by sodium fluoride were studied in the absence and presence of exogenous of Mn²⁺at 37°C in 40 mM sodium barbiturate-hydrochloric acid buffer solution (pH 7.4). Both methods were successively used to determine the values of K₁. The advances and disadvantages of each method were compared in this paper. Exogenous Mn²⁺ could result in more sensitivity of arginase to F^-1. Since the inhibition of arginase by F^-1 depends on the pH values of the reaction system and behave as a non-competitive inhibition, it probably due to its small volume and high electronic density allow it access to the activity site of the enzyme and replaces of μ-OH₂ (or μ-OH) as the bridge ligand with Mn(II, II) cluster. However, further studies are necessary to determine the modes of interaction of F^-1 with bovine liver arginase. This revised version was published online in August 2006 with corrections to the Cover Date.     

PREPARATION AND CHARACTERIZATION OF ION EXCHANGE MEMBRANES BASED ON POLYVINYLIDENE FLUORIDE

 A new ion exchange membrane based on polyvinylidene fluoride (PVDF) and sulfonated poly(styrene- divinylbenzene) was prepared by in-situ polymerization. The incorporation of sulfonic groups into the polyvinylidene fluoride composite membrane was confirmed by infrared spectroscopy (IR), ion exchange capacity (IEC) and energy dispersive X-ray analysis (EDAX). Area resistance, IEC and water uptake of the treated membrane were evaluated. When 20% of the crosslinked membrane was sulfonated at 80°C for 22 h, the PVDF ion exchange membrane can attain 0.8 Ω·cm²area resistance in NaCl aqueous solution at 25℃, IEC is as high as 2.43 millimoles per gram of the wet membrane. The hydrophilicity of PVDF membrane is also significantly improved after treatment. When 60% of crosslinked membrane was sulfonated at 80 ℃ for 6 h, water uptake of the treated membrane can attain 64.7%.     

Direct anodic oxidation ofp-methoxytoluene in methanol. The effect of electrolysis conditions

The effect of anions of the supporting electrolyte (F^–, dialkylphosphate, TsO^–, and BF ₄ ^– and other electrolysis conditions (anode material, temperature, substrate concentration) on the selectivity of the direct anodic oxidation ofp-methoxytoluene in methanol into 4-methoxybenzaldehyde dimethylacetal was studied. The highest selectivity was obtained in the presence of fluoride anion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 524–527, March, 1995.This work was financially supported by the Ministry of Science, High School and Technical Policy of the Russian Federation within the scope of the State scientific-technical program Ecologically harmless processes of chemistry and chemical technology (project No. 1.140 Low-tonnage chemical products) and by the International Science Foundation (Grant Ch-2-1246-0923).     

Ba7Fe6F32 · 2H2O: Original isolated trimers [Fe3F16]7− in a new defective jarlite-type compound

Ba₇Fe₆F₃₂ · 2H₂O was prepared from HF aqueous solution in a teflon bomb (Berghof) at 180°C. A partial exchange F^?/OH^? can be realized in more diluted HF medium and leads to Ba₇Fe₆F_32–x(OH)_x · 2H₂O. The compounds crystallize in the monoclinic system, space group C2/m (Z = 2) with a = 17.023(1) Å, b = 11.482(1) Å, c = 7.624(1) Å, β = 101.13(1)° for x = 0 and a = 17.036(2) Å, b = 11.489(1) Å, c = 7.620(2) Å, β = 101.48(1)° for x ≈? 5.3. The structures were determined from 2 256 and 1 343 independent reflections for x = 0 and x ≈? 5.3 respectively, collected with a Siemens AED2 four-circle diffractometer with the MoKα radiation (R = 0.0235 and R_w = 0.0240 for x = 0 and R = 0.0324 and R_w = 0.0335 for x ≈? 5.3). The structure, closely related to that of the Jarlite-type, is built up from isolated octahedra trimers [Fe₃F₁₆]^7?, connected together by Ba²⁺-cations. The location of anions and water molecules is discussed from bond valence calculations. Magnetic and Mössbauer studies are reported and discussed.     

The Crystal Structure of Pb8FeIIFeF24: an ordered Fluorite-like Compound

Pb₈Fe^IIFeF₂₄ is triclinic: a = 20.118(3) Å, b = 5.597(1) Å, c = 9.440(2) Å, α = 89.75(2)°, β = 105.79(2)°, α = 89.38(2)°, Z = 2. The structure is solved in the unconventional space group C1 , from X-ray single crystal data using 1 641 independent reflections (R = 0.048, R_w = 0.051). It is built up from the stacking of two subnetworks along the a axis: fluorite-like [Pb₈F₁₀]_n⁶ⁿ⁺ layers and infinite dimetallic [Fe^IIFeF₁₄]_n^6n? double-chains of corner-sharing octahedra running along the b axis.