Impact of α-, γ-, and δ-tocopherol on the radiation induced oxidation of rapeseed oil triacylglycerols

Gamma-irradiation (doses: 2, 4, 7, and 10 kGy) was used as oxidation tool to study the antioxidant effects of α-, γ-, and δ-tocopherol (enrichments 500–5000 ppm) in purified rapeseed oil triacylglycerols (RSOTG). Fatty acid composition, tocopherol degradation, primary (conjugated dienes (CD) and peroxide value (POV)) and secondary (p-anisidine value) oxidation products were chosen as test parameters. Fatty acid composition did not change. While secondary oxidation products could not be found in the irradiated samples, the POVs and CDs showed a significant, dose-dependent increase. α-Tocopherol did not inhibit the formation of peroxides, whereas γ- and δ-tocopherol reduced the POVs by more than 30%. No uniform effect of the different tocopherol concentrations at the particular doses could be established. The influence of the individual tocopherols on the CD formation was not pronounced. The degradation of the tocopherols decreased with increasing concentration. None of the tocopherols showed a prooxidant effect.     

A New Scheme to Prepare Polyoxovanadate-Polymer Hybrid Materials

Journal of Cluster Science - Polyoxovanadates (POVs) have aroused increasing attentions in recent years because of their excellent catalytic properties and unique biochemical activities. The...     

Host-Guest Complexation Between Cyclodextrins and Hybrid Hexavanadates: What are the Driving Forces?

Host-guest complexes between native cyclodextrins (α-, β- and γ-CD) and hybrid Lindqvist-type polyoxovanadates (POVs) [V₆O₁₃((OCH₂)₃C−R)₂]^2– with R = CH₂CH₃, NO₂, CH₂OH and NH(BOC) (BOC = N-tert-butoxycarbonyl) were studied in aqueous solution. Six crystal structures determined by single-crystal X-ray diffraction analysis revealed the nature of the functional R group strongly influences the host–guest conformation and also the crystal packing. In all systems isolated in the solid-state, the organic groups R are embedded within the cyclodextrin cavities, involving only a few weak supramolecular contacts. The interaction between hybrid POVs and the macrocyclic organic hosts have been deeply studied in solution using ITC, cyclic voltammetry and NMR methods (1D ¹H NMR, and 2D DOSY, and ROESY). This set of complementary techniques provides clear insights about the strength of interactions and the binding host-guest modes occurring in aqueous solution, highlighting a dramatic influence of the functional group R on the supramolecular properties of the hexavanadate polyoxoanions (association constant K_1:1 vary from 0 to 2 000 M⁻¹) while isolated functional organic groups exhibit only very weak intrinsic affinity with CDs. Electrochemical and calorimetric investigations suggest that the driving force of the host-guest association involving larger CDs (β- and γ-CD) is mainly related to the chaotropic effect. In contrast, the hydrophobic effect supported by weak attractive forces appears as the main contributor for the formation of α-CD-containing host-guest complexes. In any cases, the origin of driving forces is clearly related to the ability of the macrocyclic host to desolvate the exposed moieties of the hybrid POVs.     

Syntheses,structures, and magnetism of {V15M6O42(OH)6(Cl)} (M = Si,Ge)

Two [V₁₅M₆(OH)₆O₄₂(Cl)]^7? (M = Si for 1, Ge for 2) cluster anions with protonated amines as counterions have been synthesized under hydrothermal conditions and characterized by FT-IR, energy dispersive spectroscopy, XPS, powder X-ray diffraction, thermogravimetric analysis (TGA), elemental analysis, and single-crystal X-ray analyses. Both compounds consist of {V₁₅M₆O₄₂(OH)₆(Cl)} (M = Si for 1, Ge for 2), which are derived from {V₁₈O₄₂} by substitution of three {VO₅} square pyramids with three {Si₂O₅(OH)₂/Ge₂O₅(OH)₂} units. It represents the first example of cage-like polyoxovanadates (POVs) containing three (Si/Ge)₂O₅(OH)₂ units. There are extensive hydrogen bonding interactions between POVs and organoamines in 1 and 2. Compound 1 presents a close-packed layer aggregate, while 2 exhibits the packing of six-membered rings with a 1-D channel. Magnetism measurements demonstrate the presence of strong antiferromagnetic interaction between V^IV centers in 1.     

Composition-driven archetype dynamics in polyoxovanadates

Molecular metal oxides often adopt common structural frameworks (i.e. archetypes), many of them boasting impressive structural robustness and stability. However, the ability to adapt and to undergo transformations between different structural archetypes is a desirable material design feature offering applicability in different environments. Using systems thinking approach that integrates synthetic, analytical and computational techniques, we explore the transformations governing the chemistry of polyoxovanadates (POVs) constructed of arsenate and vanadate building units. The water-soluble salt of the low nuclearity polyanion [V₆As₈O₂₆]⁴⁻ can be effectively used for the synthesis of the larger spherical (i.e. kegginoidal) mixed-valent [V₁₂As₈O₄₀]⁴⁻ precipitate, while the novel [V₁₀As₁₂O₄₀]⁸⁻ POVs having tubular cyclic structures are another, well soluble product. Surprisingly, in contrast to the common observation that high-nuclearity polyoxometalate (POM) clusters are fragmented to form smaller moieties in solution, the low nuclearity [V₆As₈O₂₆]⁴⁻ anion is in situ transformed into the higher nuclearity cluster anions. The obtained products support a conceptually new model that is outlined in this article and that describes a continuous evolution between spherical and cyclic POV assemblies. This new model represents a milestone on the way to rational and designable POV self-assemblies.

Systems-based elucidation of the polyoxovanadate speciation reveals that heterogroup substitution can transform spherical kegginoids into tubular architectures in a programmable manner.     

A Lacunary Polyoxovanadate Precursor and Transition-Metal-Sandwiched Derivatives for Catalytic Oxidation of Sulfides

A SeO₃-centered lacunary Keggin-type heteropolyoxovanadate (hetero-POV) K₆H₂[SeV₁₀O₂₈(SeO₃)₃] ⋅ 14 H₂O ( 1 ) was isolated by one-pot reaction of KVO₃ and SeO₂ under acidic conditions. X-ray studies revealed that it comprised a single {VO₅}-capped trivacant B-α-type Keggin ion [SeV₉O₃₃(VO)]¹⁴⁻ with its lacunary sites decorated by three {SeO₃} pyramids. Interestingly, this new basic hetero-POV building block was further used as a precursor to assemble with different transition-metal (TM) ions, yielding a series of TM-sandwiched POVs K₆H₈[(SeV₁₀O₂₈(SeO₃)₃)₂(M(H₂O)₄)] ⋅ 24 H₂O (M²⁺=Mn²⁺ ( 2 ), Co²⁺ ( 3 ), Zn²⁺ ( 4 )). All four compounds were characterized by single-crystal X-ray structure analysis, IR, X-ray photoelectron spectroscopy (XPS), EPR, and ⁵¹V NMR spectroscopy. Importantly, three TM-sandwiched derivatives exhibited effective catalytic activity for the heterogeneous oxidative desulfurization of sulfides at room temperature.     

A Novel Expansion Mode of Polyoxovanadate Clusters: Synthesis,Crystal Structure and Properties of {[Cu(H2O)(C5H14N2)2]2[V16O38(Cl)]}·4(C5H16N2)

The new polyoxovanadate (POV) compound {[Cu(H₂O)(C₅H₁₄N₂)₂]₂[V₁₆O₃₈(Cl)]} · 4(C₅H₁₆N₂) was synthesized under solvothermal conditions and crystallizes in the tetragonal space group I4₁/amd with a = 13.8679(6), c = 45.558(2) Å, V = 8761.7(7) ų. The central structural motif is a {V₁₆O₃₈(Cl)} cluster constructed by condensation of 16 square‐pyramidal VO₅ polyhedra. The cluster hosts a central Cl^– anion. According to valence bond sum calculations, chemical analysis and magnetic properties the cluster anion may be formulated as [V₁₅^IVV^VO₃₈(Cl)]^12–, i.e., only one vanadium atom is not reduced. To the best of our knowledge this is the first reported {V₁₆O₃₈(X)} cluster in this V^IV:V^V ratio. The presence of the two different vanadium oxidation states is clearly seen in the IR spectrum. An unusual and hitherto never observed structural feature is the binding mode between the [Cu(H₂O)(C₅H₁₄N₂)₂]²⁺ complexes and the [V₁₅^IVV^VO₃₈(Cl)]^12– anion. The Cu²⁺ ion binds to a μ₂‐O atom of the cluster anion whereas in all other transition metal complex‐augmented POVs bonding between the transition metal cation and the anion occurs through terminal oxygen atoms of the POV. The magnetic properties are dominated by strong antiferromagnetic exchange interactions between the V⁴⁺ d¹ centers, whereas the Cu²⁺ d⁹ cations are magnetically decoupled from the cluster anion. Upon heating, the title compound decomposes in a complex fashion.     

High Nuclearity Antimonato‐Polyoxovanadate Cluster {V15Sb6O42} as a Synthon for the Solvothermal in situ Generation of α‐ and β‐{V14Sb8O42} Isomers

New heteroatom polyoxovanadates (POVs) were synthesized by applying a water‐soluble high‐nuclearity cluster as new synthon. The [V₁₅Sb₆O₄₂]^6? cluster shell exhibiting D₃ symmetry was in situ transformed into completely different cluster shells, namely, the α‐[V₁₄Sb₈O₄₂]^4? isomer with D_2d and the β‐[V₁₄Sb₈O₄₂]^4? isomer with D_2h symmetry. The solvothermal reaction of {Ni(en)₃}₃[V₁₅Sb₆O₄₂(H₂O)_x] ? 15 H₂O (x=0 or 1; en=ethylenediamine) in water led to the crystallization of [{Ni(en)₂}₂V₁₄Sb₈O₄₂] ? 5.5 H₂O containing the β‐isomer. The addition of [Ni(phen)₃](ClO₄)₂ ? 0.5 H₂O (phen=1,10‐phenanthroline) to the reaction slurry gave the new compound {Ni(phen)₃}₂[V₁₄Sb₈O₄₂] ? phen ? 12 H₂O with the α‐isomer. Both transformation reactions are complex due the change of symmetry, the chemical composition, and rearrangement of the VO₅ square pyramids and Sb₂O₅ handle‐like moieties.     

Solvent induced different morphologies of bis(propyl)triethoxysilane substituted perylenediimide and their optical properties

Nano/micro-structure of bis(propyl)triethoxysilane substituted perylenediimide (1) with nanoparticle and twisted microrod morphologies were obtained by reprecipitation method induced by water and petroleum ether, respectively. It is believed that the different nucleation and growth processes involved are responsible for the formation of the nano/micro-structure with different morphologies of 1. UV-vis absorption and photoluminescence measurements show that their UV-vis absorption and photoluminescence properties are different from each other as well as their monomer and bulk materials due to the different effects on the charge transfer (CT) transition energy levels caused by their different aggregation behaviors.     

NiCoB超细非晶合金的化学制备和热稳定性研究

用化学还原法制备了Ni－B、Co－B及不同含量的Ni－Co－B超细非晶态微粒．电感耦合等离子光谱（ICP）测定合金的组成表明：微粒中Ni与Co的含量可通过调节反应溶液中Ni与Co离子浓度来控制．X衍射（XRD）、透射电镜（TEM）及电子衍射证实合金是粒径约为20nm的非晶相球状颗粒．用示差量热法（DSC）考察了制备条件对非晶态合金热稳定性的影响．发现相同组成不同含量及不同条件下制得的样品其热稳定性均有差异．初步解释了引起这种差别的原因．从而揭示了非晶态合金结构的复杂性．     

超支化聚合物的光物理行为及其压力效应

在溶液中观察到超支化聚合物2-甲氧基-5-（2’-乙基已氧基）-对-苯乙烯/3 ，5-二乙烯基苯共聚体（MEH-PPV-HS_1）具有很强的荧光发射，并且在紫外区有两 个明显的相邻吸收带。分别激发这两个吸收带得到相同的荧光发射。在压力作用下 ，这两个吸收带表现出不同的压力效应，并且在不同的压力下分别激发这两个吸收 带时，所得到的荧光发射效率随压力的变化趋势表现出明显的不同。结果表明，这 两个相邻的吸收带分别来自于超支化聚合物分子中具有不同长短的有效共轭结构。 不同的共轭结构受光激发后到达不同的激发态。然后经过不同的松弛途径到达相同 的发光激发态而发出荧光。     

Preparation of hydroxyapatite nanoparticles: Comparison between hydrothermal and Solvo-Treatment processes and colloidal stability of produced nanoparticles in a dilute experimental dental adhesive

The main purpose of this study is to investigate the colloidal stability of hydroxyapatite (HAp) nanoparticles prepared by different methods. Nano-sized hydroxyapatite particles are synthesized by two different methods including hydrothermal and solvo-treatment processes. In hydrothermal process nanoparticles are synthesized at high temperature, while in solvo-treatment method nanoparticles are synthesized at room temperature by the use of surfactants and organic solvent. The samples are characterized by powder X-ray diffraction (XRD), fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray analysis detector (SEM + EDXA), and phase separation analyzer. The produced nanoparticles are different in size, stoichiometric ratio, morphology, crystallinity and colloidal stability in a dilute dental adhesive. The results show that the nanoparticles synthesized by these two methods are quite dissimilar and particles prepared by hydrothermal method have a smaller size and higher colloidal stability.     

农作物秸秆红外指纹图谱双指标序列分析

采用傅立叶红外光谱技术研究了不同地区、不同种类农作物秸秆的红外指纹图谱,对其谱带归属进行了判别分析;并利用共有峰率和变异峰率双指标序列法对农作物秸秆样品进行分析鉴别。结果表明:同种农作物秸秆化学成分相似,不同农作物秸秆化学成分差异较大,其中花生秆与其他农作物秸秆化学成分差异最大。     

Positive-ion mass spectra and collision-induced dissociation of some 2,3-didehydro amino acids

The positive-ion mass spectra of a number of didehydro amino acids, ionized by electron impact and/or thermospray, and collision-induced dissociation spectra taken at collision energies of a few electron volts and keV have been performed on multiple quadrupole and reversed geometry sector instruments. Observed differences in the mass spectra and in the fragmentation patterns are explained in terms of different isomeric structures, different internal excitation energies and different ion transit times between the ion source and the collision cell. Molecular ions of unhydrated amino acids are efficiently formed both by electron impact and thermospray, whilst molecular ions of the hydrated compounds are formed more efficiently by the latter technique. The present investigation demonstrates that the use of different ionization techniques combined with mass spectrometry/mass spectrometry measurements at different collision energies yields a wealth of information relevant to structural characterization of this important class of molecules.     

Efficient synthesis of chromenopyridine and chromene via MCRs

MCRs for preparation of chromenopyridines under reflux conditions and chromenes at room temperature conditions from different salicylaldehydes,malononitrile and different thiols（mol ratio- 1：2：1） were established.Mechanistic investigation suggests that the MCRs undergo different pathways at different temperatures and catalyzed by different organic bases.The structure of chromenopyridine and chromene are confirmed by crystal X-ray crystallography.     

非晶氧化锆水合物红外研究

用红外吸收光谱（IR）结合X射线衍射（XRD）、差热（DTA）和热失重分析（TG）详细研究了氧化锆前驱物（溶胶凝胶法制得的非晶态氧化锆水合物）的结构。实验结果表明在非晶态氧化锆水合物中有三种不同的近程结构。它表现为不同条件下制得的非晶氧化锆水合物的红外吸收谱在1700～1200cm-1水和羟基的弯曲振动吸收区出现1633、1551、1400和1340cm-1四个不同的羟基吸收峰。这表明样品中有三种不同近邻结构的羟基。根据实验结果我们提出了相应的非晶氧化锆水合物的近邻结构模型。造成这种结构差异的原因是制备过程中溶胶-凝胶反应的羟基浓度的不同。非晶态氧化锆水合物晶化后生成具有不同晶体结构的纳米氧化锆的主要原因是由于它们的不同近邻结构。     

Effect of annealing conditions on the structure of drawn nylon 66 yarns

Differences in structural parameters, shrinkage, and retractive forces have been compared for nylon 66 tire yarns annealed at several temperatures in silicone oil and in air. It is found that significantly different structural changes occur for oil-annealing and air-annealing. Retractive forces measured in hot oil are characterized by a high initial force, followed by a rapid decay and a second, more gradual, increase which is also followed by a decay at sufficiently high temperatures. In heated air, the first, short-term, retractive force is absent. It is postulated that these differences are due to the different rates of heat transfer at gas–solid and at liquid–solid interfaces, and that rapid heat transfer (as in the case of oil-annealing) promotes two mechanisms of molecular change which are characterized by different degrees of structural parameter change, and by different amounts of shrinkage.     

New Possibilities of the Acetosulfation of Cellulose

Regioselectively substituted cellulose sulfates in C2/3-, C2/6-, or C6-position of the anhydroglucose unit are accessible by certain synthesis routes. Thereby, products with different properties and various application areas are resulted. Important characteristics of cellulose sulfates regarding their applications are solubility (e.g. in water), rheological behavior, different interaction with low or high molecular cations, thermo reversible gel formation, enzymatic degradability, anticoagulant and antiviral activity. In C6-position substituted cellulose sulfates can be synthesized in principle by acetosulfation. The acetosulfation is a quasi-homogeneous synthesis proceeding under gradually dissolution of the cellulose by using different reactivity of the primary and secondary OH-groups as soon as converting cellulose acetate sulfates. After precipitation of the polymer the acetyl groups are cleaved in alkaline solution. The focus of our study was firstly the investigation of the acetosulfation in different polar aprotic solvents by various sulfating and acetylating agents. In general it should be investigated if C6 substituted cellulose sulfates can be obtained by acetosulfation with different solvents and agents. The products were characterized by ¹³C-NMR and Raman spectroscopy.     

Spectroelectrochemical processes in polyaniline films prepared by different methods

Basic in situ spectroelectrochemical methods of the studying of the polyaniline electrosynthesis processes and doping-dedoping of the polyaniline films prepared by different procedures are overviewed. The advantages of the combining of different spectroelectrochemical methods in a single experiment are discussed and the extra information on the processes of electrosynthesis and electrochemical doping-dedoping of polyaniline prepared by the combinations of methods is analyzed. Components of the polyaniline electronic absorption spectra are analyzed and spectroelectrochemical properties of polyaniline films prepared by vacuum evaporation are studied by a complex of methods; the results of the studies are presented.