Highly efficient,polymerizable, sulfur‐containing photoinitiator comprising a structure of planar N‐phenylmaleimide and benzophenone for photopolymerization

In a continuation of research on chemically bonded photoinitiators comprising a structure of planar N‐phenylmaleimide (NPMI) and benzophenone (BP), a novel, highly efficient, polymerizable, sulfur‐containing photoinitiator, 4‐[(4‐maleimido)thiophenyl]benzophenone (MTPBP), was synthesized by the introduction of an NPMI group into BP. Another chemically bonded photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), was selected to evaluate its photoefficiency. The results showed that MTPBP possessed a greatly redshifted UV maximal absorption and a very weak fluorescence emission. Electron spin resonance spectra indicated that the C? S bond in its molecule underwent photolysis reactions to generate radicals to initiate the polymerization. Three representative types of different functionality monomers—methyl methacrylate, 1,6‐hexanediol diacrylate, and trimethylolpropane triacrylate—were chosen to be initiated through dilatometry and differential scanning photocalorimetry with unsaturated tertiary amine N,N‐dimethylaminoethyl methacrylate as the coinitiator. The results showed surprisingly high efficiency of MTPBP due to the mutual influence between NPMI and BP as in their physical mixtures and photolysis reactions at the C? S bond. Both MPBP and MTPBP behaved with similar regularity toward different monomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3738–3750, 2006     

New acetophenone-functionalized thiophene monomer for conducting films on electrodes in chemical ion-sensorics: The synthesis and spectroelectrochemical study

A new acetophenone-functionalized thiophene monomer, 2-hydroxy-6-[2-(thiophene-3-yl)ethoxy]acetophenone, is synthesized by the reaction of 2.6-dihydroxyacetophenone with 2-(thiophene-3-yl)ethane-1-ol under mild conditions. The synthesis is performed in order to study its electrochemical oxidation and prepare a functionalized conducting material for ion sensors with a receptor group for divalent heavy-metal cations. The redox behavior of the functionalized thiophene is studied by simultaneous in situ ESR and Vis-NIR spectroscopy. The formation of soluble thiophene oligomeric structures during the electrochemical oxidation of the monomer is found. Direct evidence for the formation of oligomers is given by ex situ MALDI-TOF and LDI-TOF mass spectrometry. The acetophenone-functionalized monomer and 3-methylthiophene are electrochemically copolymerized and the copolymeric nature of the product is proved by MALDI-TOF mass spectrometry as well. The copolymer film at the electrode surface is characterized in its redox behavior. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 11, pp. 1302–1311. Based on the report delivered at the 8th International Frumkin Symposium “Kinetics of the Electrode Processes,” October 18–22, 2005, Moscow. The text was submitted by the authors in English.     

Decomposition of gaseous toluene on thermally-excited titanium dioxide and its ESR study under high temperatures

Decomposition of gaseous toluene on thermally-excited activated titanium dioxide (TiO₂) was investigated using a simple flow system. The decomposition of toluene on the TiO₂ bead was 92% at 400 °C. The irregular phenomena in the toluene decomposition at around 300 °C seemed to be due to the coloration of the TiO₂ bead. Electron spin resonance (ESR) measurement at high temperatures was carried out using the heating unit. Since the g-value of the signal was 1.996, the existence of Ti³⁺ in TiO₂ material was confirmed. That is, oxygen vacancy generated by thermally-excitation of TiO₂, and the reaction activity of the TiO₂ bead for gaseous toluene must be due to spins on the material.     

L波段三维ESR成像系统的研制（Ⅲ）——L波段谐振腔的研制

描述了一个用于生物样品L波段ESR成像用的谐振腔,讨论了在制作、设计过程中几个值得注意的问题，该腔为3-环2-裂缝再进入式谐振腔，可检测直径为20 mm长30 mm的H₂O样品. 空腔的共振频率为1.05 GHz. 腔的Q值是样品中水含量的函数，无载Q大于1 000. 用插入侧臂的耦合环得到谐振腔与微波桥之间的匹配，确定了耦合环直径的最佳值，对无载腔其值约为腔臂直径的1/3，而对有载腔其值约等于腔臂的直径. 用该腔检测了样品中TEMPO氮氧自由基的空间分布.     

Copolymers of phenylacetylene and para‐nitrophenylacetylene with nonlinear optical properties: Further insight on the conformational structure

Copolymers of phenylacetylene (PA) and para‐nitrophenylacetylene (pNPA), named poly(PA‐co‐pNPA), were obtained in different PA/pNPA ratios and different reaction conditions with Rh(I) catalysts. The structure of the copolymers was investigated with IR, laser Raman, ¹H NMR, electron spin resonance (ESR), and diffuse reflective ultraviolet–visible (DRUV) light spectroscopies. The pristine polymers had a cis–transoidal structure as the predominant conformation with some trans sequences. Detailed ESR studies supported by computer simulation and conformation analysis have suggested that the trans sequences were due to pNPA sequences and that the cis‐C?C bond sequences of pNPA were associated with a stabilized cis radical formed by four to five of pNPA monomers. This particular stabilization was probably the reason for the higher reactivity of pNPA as compared with PA. These cis sequences were preferentially cleaved to generate π radicals. The compression and, to a minor extent, thermal treatment of poly(PA‐co‐pNPA) samples induced a cis‐to‐trans isomerization, leading to a trans–transoidal form with a planar zigzag structure and with a conjugation length up to n = 24 repeat units, determined by DRUV and Raman experiments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2365–2376, 2004     

Free radicals formed by addition of antimalaric artemisinin (Qinghaosu,QHS) to human serum: an ESR-spin trapping investigation

The antimalaric drug artemisinin (QHS) is believed to operate through a mechanism initiated with the cleavage of its endoperoxidic bond induced by transition metal ions. An ESR investigation of the reaction of QHS with human serum in the presence of two spin trapping agents has led to the detection of spin adducts of carbon-centred radicals. Experiments carried out replacing the human serum with iron(II) salts led to the observation of the same spin adducts, thus supporting previous suggestions that alsoin vivo the drug operatesvia a radical-based mechanism. UV irradiation of QHS also led to the trapping of transient free radicals.     

Ethylene polymerization over transition‐metal supported catalysts. II. Cr on zeolite,silica, and charcoal: Characterization and activity studies

Cr catalysts supported on silica, zeolite NaY, and charcoal were prepared with two different methods. They were characterized and examined in the polymerization of ethene. Cyclic voltammetry, electron spin resonance, X‐ray photoelectron spectroscopy and silicon‐29 magic‐angle spinning nuclear magnetic resonance spectroscopy were used to characterize them, demonstrating that Cr is not in a single oxidation state, that the distribution among the various oxidation states depends on the history of the sample, and that even for a single oxidation state a variety of different environments can occur. In the polymerization of ethene, the supported Cr catalysts exhibited activity values varying from 10³ to 10⁵ gPE · molCr^?1 · [M]^?1 · h^?1, depending on the choice of the support and on the method by which the Cr is placed on it. Silica seemed to be the most efficient support for Cr for this reaction. However, the zeolite‐supported catalysts also showed reasonable activity values (A_p ? 10⁴ units) and presented the advantage of having a strong interaction between the Cr and the support, which may prevent leaching of the cation into the surrounding environment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3768–3780, 2003     

Structural features of catalytically active oligoorganometallosiloxanes

Copper- and (copper, aluminum)-containing organosiloxanes were studied by spectroscopic methods. It was found that in organometallosiloxanes (OMS) with an increased content of copper (Si/Cu=1 ∶ 1) Cu atoms are rather uniformly distributed in the siloxane matrix. All compounds under study are complexes characterized byd-d-transitions in copper ions with a constant coordination number of the metal atom. The intensity of thed-d-transition band increases as the copper content increases. ESR studies demonstrated that in the compounds under consideration, a change from mononuclear paramegnetic centers to clusters, in which copper ions are linked by strong spin-exchange interactions, occurs as the copper content increases. The catalytic activity of the above-mentioned compounds in isomerization reactions of 3,4-dichlorobutene-1 was studied. It was found that copper atoms serve as catalytic centers. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1946–1949, October, 1998.     

活体心肌缺血再灌自由基产生和清除的ESR研究

ESR和自旅捕捉技术用于研究活体动物犬心肌缺血再灌产生的自由基,PBN从冠状静脉血液中捕捉到了OH自由基,直接地证实了缺血再灌细胞膜损伤的活性氧自由基作用机制;实验还看到一种甾体皂甙药物具有保护心肌细胞,防止自由基损伤的功能.