用电子自旋共振谱研究我国一些煤的自由基

本文用电子自旋共振谱(ESR)研究了我国十种不同变质程度的煤。电子自旋共振最重要的参数是g值、自由基的浓度、线宽和线形。用这些参数与煤中的碳、氧等元素相关联,发现ESR参数与煤的变质程度有密切关系。     

三苯基硅自由基的电子自旋共振研究

有机硅自由基的电子自旋共振(ESR)的研究一直十分活跃,Bock等已做了大量工作。然而,对于三苯基硅自由基的ESR研究报道却甚少。采用X射线辐照单晶生成的三苯基硅自由基的ESR谱并未获得理想的超精细结构谱,而采用三苯基硅烷与二苯甲酮热反应仅获得Ph_2COSiPh_3自由基的ESR谱。本文报道在氯仿溶液中,用无水三氯化铝与三苯基硅醇或三苯基硅烷在室温下反应,获得三苯基硅烷正离子自由基(Ph_3Si~+)ESR的研究结果,并进行计算机模拟。     

应用煤的大分子结构理论进行煤化学实验教学

以煤的大分子结构理论为指导,设置煤化学实验的教学内容,开展实验教学。实验项目的开设以工业分析、元素分析和发热量测定为顺序。教学过程采用主、副板书结合,引导学生运用煤的大分子结构理论分析煤的组成和性质,对比讨论不同煤样的实验结果。这种教学方式突出了煤的大分子结构理论的中心地位,构建了“煤的生成-煤的结构-煤的性质”的知识体系。可循序提高学生的思维能力,即：先整体把握煤的水分、挥发分和固定碳含量随煤化程度的变化规律,再细化分析煤中C、H、O元素在不同煤化阶段的变化特点,最后综合评价煤中可燃质与不可燃质对煤热值的影响。     

γ辐照 聚全氟乙丙烯(F46)的电子自旋共振研究 I.真空中俘获自由基的定量研究

A method for determining respectively the concentration of free radicials...CF2-CF2.(RI), ...CF2-CF-CF2...(RII)and...CF2- C(CF3)-CF2...(RIII) trapped in γ-irradiated F46 in vacuum at room temperature by analysing the ESR overlapping spectra is proposed. A quantitative relation between the concentration of free readicals and the total dose of γ-irradiation has been studied. The generating rate o free radicals caused by irradiation, i.e. G-value, has been calculated; it is 2.0 for RIII, 1.2 for RI, and 0.59 for RII. the magnitude of G value of free radicals is in the reverse order of their stability. Hence, we assume that the G value of free radicals in F46 mainly depends on the escaping rate of F2 and other fluorine-containing small molecules from surface of polymer into space. Therefore the looser the molecular chain, the larger becomes the G value of free radical. From that, we consider that both unstable free radicals RIII and RI with larger G-value mainly locate in the amorphous region, and the stable free radical RII with lower G-value is in the crystalline region. Recombinations between free radicals RII and RIII, or between RII and RI are forbidden at the temperature lower than 80C. An explanation for the saturation phenomenon of concentration of free radicals is given.     

光致电子转移对Rhodamine 6G基态分子结构影响的非共振Raman光谱研究

基于非共振Raman 光谱和量子化学计算, 研究了在纯电子给体N,N-二乙基苯胺(DEA)溶剂中Rhodamine 6G (Rh6G⁺)基态分子结构的变化, 这有利于理解该体系中的光致分子间电子转移(PIET). 与PIET相耦合的所有振动模式已被确定和指认. 结果表明: 对应于氧杂蒽环且位于675 cm^-1处最主要的振动模式对PIET 有着至关重要的贡献; 通过与电荷转移复合物(Rh6G/DEA⁺)的发色团芳香族环的C―C伸展振动模式作比较, C=C伸展振动对PIET的影响更敏感. 本文的研究工作能为具有合适电子转移特性的光伏器件中分子结构或溶剂环境的设计提供新颖的观点.     

固体胆红素自由基的电子自旋共振研究

本文用电子自旋共振法(ESR)对各种来源的胆红素进行了研究,发现固体胆红素极易以稳定的自由基形式存在,并对该自由基的本质、结构特征及形成机理进行了探讨。结果表明胆红素自由基是由结合态的超氧自由基及半醌自由基构成,自由基再生动力学曲线属零级反应;微量过渡金属离子在胆红素超氧自由基形成及存在过程中起着重要作用。本文研究结果提示,胆红素的药理及毒理性质可能与其自由的性质有着密切关系,提出胆红素并非只是代谢的最终废弃物,而极可能是体内的活性氧自由基阱,是内源性细胞保护剂。     

光致电子转移对Rhodamine 6G基态分子结构影响的非共振Raman光谱研究(英文)

基于非共振Raman光谱和量子化学计算,研究了在纯电子给体N,N-二乙基苯胺(DEA)溶剂中Rhodamine 6G(Rh6G+)基态分子结构的变化,这有利于理解该体系中的光致分子间电子转移(PIET).与PIET相耦合的所有振动模式已被确定和指认.结果表明:对应于氧杂蒽环且位于675 cm-1处最主要的振动模式对PIET有着至关重要的贡献;通过与电荷转移复合物(Rh6G/DEA+)的发色团芳香族环的C―C伸展振动模式作比较,C=C伸展振动对PIET的影响更敏感.本文的研究工作能为具有合适电子转移特性的光伏器件中分子结构或溶剂环境的设计提供新颖的观点.     

环己酮抽提煤的研究

报道了环己酮在索氏抽提及回流抽提等条件下对不同煤队煤样的抽提行为，并探讨了抽提机理与特点，研究结果表明五己酮是一种良好的氢键受体，它与煤分子间相互作用同煤中羟基有密切关系。     

磷钼钨杂多酸还原态的电子自旋共振研究

合成了一个系列具有Keggin结构的磷钼钨杂多酸H~3PMo~1~2~-~nW~nO~4~0(n=0,3,6,9,11,12).用电子自旋共振(ESR)方法研究了这些杂多酸的还原性.结果表明,在还原态的杂多酸中,除了因失去桥氧产生的Mo^5^+信号A(其g~⊥^A=1.952, g~∥^A=1.852)外,钨取代后产生另一Mo^5^+信号B,其g~⊥^B=1.923,g~∥^B=1.877.该信号被认为是由于杂多酸中钼的端氧还原所致. 由此提出钨的取代影响了杂多酸的氧化还原性,即桥氧的稳定性相对增强,端氧的稳定性相对减弱     

ENDOR Spectroscopy — A Promising Technique for Investigating the Structure of Organic Radicals

The name “ENDOR” has been known since biblical times and denotes a small town close to the Sea of Galilee (ca. 1000 B.C., 1 Sam. 28 : 7 ff). The acronym “ENDOR” (Electron Nuclear DOuble Resonance) characterizes the extension of electron spin resonance to electron-nuclear double resonance spectroscopy, a method that has opened up new dimensions for the investigation of complicated paramagnetic molecules. Only ENDOR spectoscopy, which has achieved technical perfection in the last decade, overcomes the resolution limitations of EPR spectroscopy, thus allowing interesting applications in the field of biochemistry. ENDOR investigations of the primary process of photosynthesis, of the mode of action of derivatives of vitamin E and K, and of the mechanism of the enzymatic catalysis of flavoenzymes in biological redox-chains have opened up new vistas. ENDOR and its extension to the triple resonance experiment TRIPLE offer, for example, the potential for a precise determination of hyperfine coupling constants, including their signs, which are frequently especially interesting. In addition to protons, a multiple of magnetic nuclei can be studied by ENDOR, such as e.g. ²H, ¹³C, and ¹⁴N. The ENDOR techniques is not restricted to monoradicals, but can also be applied to polyradicals in spin states of higher multiplicities (triplet, quartet, or quintet state). The experimental data accessible from ENDOR yield information about spin and charge density distributions, and about the geometrics of radicals and their internal dynamics; they also provide an excellent test for the accuracy of quantum mechanical calculations.     

间氯苯胺的乳液聚合及聚合物链结构表征

聚苯胺以其良好的电化学稳定性和掺杂可逆性 ,成为一类优良的电活性聚合物 [1,2 ] ,但其溶解性差 ,限制了它的加工及应用 .用取代基对聚苯胺的结构进行修饰 ,可有效地提高其加工性能 [3,4 ] ,但有关含吸电子取代基的苯胺衍生物聚合的报道尚少 .Ranger等 [5]指出 ,含强吸电子取代基团的聚苯胺不易用化学氧化聚合方法制备 ,并提出被氧化单体中的 N7和 C4位置必须具有相近的电子自旋密度 ,才能进行“头 -尾”偶联 ,而含强吸电子取代基团的苯胺单体中这两个位置的反应能力是不等价的 ,但可采用与母体共聚的方法可制备含强吸电子取代基 (如— C…     

An ESR study of radical reactions of C60 and C70

The results of ESR spectroscopic studies of radical reactions of fullerenes are presented. Reactivities of radicals of various chemical natures with respect to C₆₀ and C₇₀, delocalization of the unpaired electron in monofullerenyl radicals, and their reactivity are considered. The examples of dynamic effects in the ESR spectra of fullerenyl radicals, associated with the hindered rotation of the attached radicals, are presented. Characteristic features of the structures of the spin adducts resulting from polyaddition of free radicals to fullerenes and of fullerenyl radicals containing ²-bonded metaIloco mplexes are discussed.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2396–2406, October, 1996.     

A Study of the Antioxidant Effect of Flavonic Compounds for Preventing Lipid Oxidation by Using Fluorescence Spectroscopy

In this paper a study of the effect of flavonic compounds in preventing and/or reducing the membrane lipid oxidation due to free radical attack was performed by using fluorescence spectroscopy techniques. Lipid peroxidation was investigated by using liposomes-artificial membrane models, which were prepared by lipid hydration method. Their oxidation was performed with a 15-W ultraviolet germicidal lamp having wavelength radiation 253.7 nm. In the first series of experiments, the protective effect of two synthetic antioxidants (quercetin and caffeic acid) against free radicals was monitored, while in the second series two 70% hydroalcoholic extracts from blueberry and blackcurrant leaves was used. It was determined that natural antioxidants have a much higher antioxidant power against free radicals than synthetic compounds but they degrade after two hours of oxidation. Liposomes are better protected when using natural antioxidants, but their degradation is completed more quickly, than in the case of synthetic antioxidants.     

r,r′-联吡啶桥联Cu,Rh配合物的合成、晶体结构和ESR谱

合成了r,r’-联吡啶为桥的异双核配合物[(H_2O)Cu(dien)(μ-r,r’-bpy)Rh(NH_3)_5](ClO_4)_5·H_2O.研究了单晶结构和ESR谱.晶体属正交晶系,空间群Pbca,晶胞参数:a=14.425(1),b=29.589(2),c=16.893(6)A,Z=8.偏离因子R=0.065.分子中Cu~(2+)和Rh~(3+)分别取五配位的四方锥和六配位的八面体构型,联吡啶桥的2个吡啶面夹角为51°.依据ESR谱计算了3配合物中Cu~(2+)的键参数并讨论了Cu~(2+)的成键性质.     

ESR spectra of paramagnetic palladium complexes

Binuclear nitrosopalladium complexes Pd₂(μ-COOR)₂(η²-CH₂C₆H₄NO)₂ (R = Me, CF₃, or Ph) were studied by ESR spectroscopy. Analysis of parameters of ESR spectra of the polycrystalline samples and their toluene solutions suggests partial izomerization of the nitroso ligands to the nitroxide form to result in the oxidation of palladium(II) to palladium(III). __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1746–1751, August, 2005.     

Characterization of Ligand Binding by Saturation Transfer Difference NMR Spectroscopy

Fast identification of binding activity directly from mixtures of potential ligands is possible with the NMR method described, which is based on saturation transfer to molecules in direct contact to a protein. In addition, the ligand's binding epitope is easily identified. High sensitivity and ease of use are the principal advantages of this method. The picture shows the normal 1D NMR spectrum of a mixture and the spectrum obtained by applying the STD method, which exclusively shows signals from molecules with binding affinity.     

UV-generated free radicals (FR) in skin: their prevention by sunscreens and their induction by self-tanning agents

In the past few years, the cellular effects of ultraviolet (UV) irradiation induced in skin have become increasingly recognized. Indeed, it is now well known that UV irradiation induces structural and cellular changes in all the compartments of skin tissue. The generation of reactive oxygen species (ROS) is the first and immediate consequence of UV exposure and therefore the quantitative determination of free radical reactions in the skin during UV radiation is of primary importance for the understanding of dermatological photodamage. The RSF method (radical sun protection factor) herein presented, based on electron spin resonance spectroscopy (ESR), enables the measurement of free radical reactions in skin biopsies directly during UV radiation. The amount of free radicals varies with UV doses and can be standardized by varying UV irradiance or exposure time. The RSF method allows the determination of the protective effect of UV filters and sunscreens as well as the radical induction capacity of self-tanning agents as dihydroxyacetone (DHA). The reaction of the reducing sugars used in self-tanning products and amino acids in the skin layer (Maillard reaction) leads to the formation of Amadori products that generate free radicals during UV irradiation. Using the RSF method three different self-tanning agents were analyzed and it was found, that in DHA-treated skin more than 180% additional radicals were generated during sun exposure with respect to untreated skin. For this reason the exposure duration in the sun must be shortened when self-tanners are used and photoaging processes are accelerated.     

用X射线研究煤中大分子的结构

煤的大分子结构可用化学方法和物理方法进行研究。在化学方法中,煤结构统计分析法占有重要地位,但其结果存在一定统计误差。本文研究了一系列不同级别煤的高角X射线散射强度,结果表明,随煤级别增高,煤大分子结构的X射线参数的变化是连续的。显然,这一工作对于研究煤中大分子的结构是很有意义的。