Hydrogen-Related Paramagnetic Centers in Ge-Doped Sol-Gel Silica Induced by γ-Ray Irradiation

We have studied the generation mechanisms of H(II) paramagnetic centers in Ge-doped silica by investigating up to 10⁴ mol ppm sol-gel Ge-doped silica materials. We have considered materials with the same concentrations of Ge but that are produced by two different densification routes that give rise to different concentrations of Ge-related oxygen deficient centers (GeODC(II)). These centers are characterized by an optical absorption band at ∼5.2 eV (B_2β band) and two related emissions at ∼3.2 eV and ∼4.3 eV. The GeODC(II) content was estimated by absorption and emission measurements. The H(II) centers were induced by room temperature γ-ray irradiation and their concentration was determined by electron paramagnetic resonance measurements. The comparison between the two kinds of materials, obtained by different preparations, shows that the GeODC(II) concentration increases with the Ge content and is enhanced by vacuum densification. The comparison of irradiated samples shows that beyond the already known process of conversion of preexisting GeODC(II) into H(II) centers, another generation process of H(II) centers is effective that involves irradiation induced GeODC(II).     

Paramagnetic Centers in Irradiated Potassium Picrate

The formation of paramagnetic centers in potassium picrate in a radiation field was found using EPR spectroscopy. Stable paramagnetic centers were identified as 2,6-dinitro-para-quinone, iminoxyl, and ^– radicals. The kinetics of buildup of stable paramagnetic centers was studied over a wide dose range (0.14–5 MGy), and the temperature stability was studied at 77–550 K. It was found that the decay of paramagnetic centers in the temperature range 373–523 K obeyed the laws of polychronous kinetics. A reaction scheme for the radiation-thermal decomposition of sodium picrate with the participation of radical radiolysis products was proposed.     

石英玻璃中顺磁缺陷中心的ESR成像

用ESR成像方法探测了石英玻璃杜瓦受紫外光辐照后产生的局部晶格缺陷——F心的空间分布情况.从F心的有梯度场ESR谱和二维ESR图象可以看出,石英杜瓦中产生的F心空间分布是不均匀的,其浓度与辐照方向和辐照强度密切相关.从F心ESR散点图计算出的石英杜瓦横截面几何尺寸与实物基本相符.     

Chain Paramagnetic Processes and the Nature of Paramagnetic Centers of Polymers with Conjugated Systems

This paper is concerned with analysis of the basic regularities of the kinetics of formation of polymers with a conjugated system. The experimentally found regularities are explained in terms of the proposed chain branched polymerization mechanism. The principal role in the chain polymerization mechanism is played by paramagnetic centers which are formed from the diamagnetic macromolecules of the polymer in the process of synthesis. The formation of paramagnetic centers is also due to the chain mechanism. It has been established that the thermal effect of the reaction leads to localized overheating of the emerging heterophase of the polymer, which has important consequences for the kinetics of polymerization and the rate of formation of paramagnetic centers.     

Sol-Gel Particulate Float Process to Make Vitreous Silica Bodies

Particulate sol-gel technology uses larger particles than that of alkoxide-derived gels and provides larger pore sizes in the gelled object. This allows relatively rapid drying and fabrication of large rods or tubular shapes. However, the formation of more complex or flat shapes, which require extensive surface contact with a mold, is more difficult. The shrinkage during drying, with the significantly greater stress of surface friction due to adhesion, frequently leads to cracking.We have demonstrated a solution to this problem by floating the gel on the surface of a dense liquid. Dry silica panels up to 28 × 40 × 0.7 cm³ were prepared in this way. The use of patterning molds allowed the fabrication of more sophisticated shapes. These bodies were sintered to transparent vitreous silica articles of near net dimensions.     

Interaction of Nitromethane with Modified Paramagnetic Defects on a Thermochemically Activated Silica Surface

It was found that the interaction of the modified paramagnetic defects SiO(CH₂) _n H₂ (n = 0.1) with nitromethane on a thermochemically activated silica surface at 300 K results in the formation of the following nitroxyl radicals: SiO(CH₂) _n CH₂ON( )CH₃ and SiO(CH₂) _n CH₂N( )CH₃. It was suggested that these radicals are the products of two different reactions of the modified paramagnetic defects: the first results from a reaction with free nitromethane; the second, from a reaction with nitromethane bound as complexes with diamagnetic surface defects.     

Palladium(I) Coordination Polymers with Unsaturated Dicarboxylic Acids with Stable Paramagnetic Centers

Russian Journal of Coordination Chemistry - Palladium(I) coordination polymers with unsaturated dicarboxylic acids, {[cis-Pd(C4H2O4)(H2O)]·(H2O)}n (I) (maleic acid),...     

Phosphorus Crown-Ethers with Nitrogen-Containing Heterocycles

Abstract

Phosphorus-containing crown-ethers functionalized by heterocycle fragments have essential advantages over the usual ones. The introduction of structural units of indoles, pyrroles and indolizines to phosphorus atom of the macrocyclic chain is capable to change lipophilic, complexing, biological and other properties of the initial crown-ethers. For synthesis of such compounds we have used dihalidophosphines obtained by direct substitution of the electron-rich aromatic compounds with phosphorus (III) halides. As a result, series of highly efficient macrocyclic compounds of a nowel type have been obtained.     

Methylammonium Chlorochromate Adsorbed on Silica Gel for Regeneration of Carbonyl Compounds from their Nitrogen-Containing Derivatives Under Mild and Non-Aqueous Conditions

Oximes, p-nitrophenylhydrazones, 4-phenylsemicarbazones and semicarbazones are converted to their corresponding carbonyl compounds in good yields using methylammonium chlorochromate adsorbed on silica gel(MCC/SiO₂) under mild and non-aqueous conditions.     

Mechanism of Nitrogen-Containing Cyclic Polymerization

Abstract

The comprehensive polymerization mechanism of the nitrogen-containing cycles 1-azobicyclo (3,1,0)-hexane (ABH), conidine, quinuclidine, and triethylenediamine under the action of quaternary ammonium salts, ammonium salts, and BF₃ complex with conidine is studied. Polymerization is of the living polymers type, and the active centers of monomer polymerization are ions and ion pairs: the activity of the latter is comparable to and exceeds that of the free ions. The effects of the nature of the counterion, cation, and medium polarity on the reaction rate are investigated. The polymerization rate is found to depend on the nature of the counterion in the polymerization of ion pairs, but not to depend on the counterion in the polymerization of free ions. The reaction rate is proportional to the counterion size in the polymerization of ion pairs. In the case of conidine K₊ = 0.2, K_±(Cl^?) = 0.28, K_±(Br^?) = 0.36, K_±(I^?) = 0.51, and K_±(ClO₄ ^?) = 0.62 (liter)/(mole)(min). The heats of nitrogen-cyclic polymerization are measured and correlated with the activation energy.     

Some New Nitrogen-Containing Redox Polymers

Abstract

Synthesis of some new N-substituted aziridinyl compounds by the addition of aziridine to monovinyl- and divinyl-substituted p-quinones is described. The redox potentials of the monomers, their polymerization behavior, and the properties of redox polymers derived from them were investigated.

Different polymerizable monosubstituted and disubstituted vinyl-4,7-indazolequinones were prepared by 1,3-dipolar addition of vinyldiazomethane to 1,4-benzoquinones. By copolymerization of 5,6-dichloro-3-vinyl-indazolehydro-quinone triacetate with 5,6-dichloro-l,3-divinyl-indazole-hydroquinone diacetate as a crosslinking agent, followed by hydrolysis and sulfalkylation of the resulting copolymer with propane sultone, chemically stable redox resins were obtained.     

水相中铜催化含氮杂环化合物的N-芳基化反应

在水相中建立了一种简单实用、经济环保的实现含氮杂环化合物N-芳基化反应的催化体系.实验发现以廉价的Cu2O为催化剂,价廉、易获得的8-羟基喹啉为配体,n-Bu4NBr为相转移催化剂,在水相中100℃下含氮杂环化合物与卤代芳烃顺利反应生成C—N偶联产物,得到中等及优良的产率.     

Synthesis of Nitrogen-Containing Phenoxyacetic Acid Derivatives

Nitrogen-containing phenoxyacetic acid derivatives were synthesized by reactions of substituted phenoxyacetic acids with amines, urea, and ethyl carbamate.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 557–561.Original Russian Text Copyright © 2005 by Yamansarova, Kukovinets, Zainullin, Galin, Abdullin.     

Nitrogen-Containing Organomineral Fertilizer Based on Wood Waste

A new nitrogen-containing fertilizer was obtained by oxidative ammonolyis from wood waste. The chemical composition of the fertilizer was studied by functional chemical analysis. The fertilizer was tested in field conditions.     

Synthesis of Polyheterocyclic Nitrogen-Containing Marine Natural Products

The synthetic routes used for the preparation of marine alkaloids variolin B and lamellarins are described.     

Synthesis of Thioglycosides with Nitrogen-Containing Heterocyclic Fragments

A number of thioglycosides derived from benzoylated glucopyranose and nitrogen-containing heterocyclic thiols have been synthesized in up to 98% yield, and benzoyl protecting groups have been removed from the glycoside with a 3-phenyl-4-oxo-3,4-dihydroquinazolin-2-ylsulfanyl fragment.     

Paramagnetic organoaluminum complexes

Alkylaluminum compounds react with some aza-aromatics and alkali metals to yield persistent paramagnetic species. Depending on the solvent and the coordinating ability of the azine, radical anions, neutral radicals or radical cations are formed. ESR spectroscopy has been used to elucidate the nature of the radical species.