光解苯半醌和2-羟基-2-丙基自由基的CIDEP谱

用高时间分辨ＥＳＲ波谱仪测量了光解苯半醌和２－羟基－２－丙基自由基的ＣＩＤＥＰ谱,苯半醌自由基的ＣＩＤＥＰ属ＴＭ机理,实验研究了微波功率,溶液浓度对苯半醌自由基的ＣＩＤＥＰ谱时间演化的影响,２－羟基－２－丙基自由基的ＣＩＤＥＰ属ＲＰＭ机理,实验研究了自旋极化的生成环境。     

TX-100胶束中光解萘醌自由基的电子自旋极化研究

利用高时间分辨的电子自旋共振波谱仪(TRESR),研究了含有不同表面活性剂溶液中光解萘醌自由基CIDEP。在乙二醇溶剂中,在308nm的紫外激光照射下得到三重态机理极化的中性萘半醌自由基和以碳为中心的自由基R^.(OH)~2的信号,在表面活性剂TX-100的胶束中,得到萘醌阴离子自由基信号,并用萘醌分子与TX-100胶束间的电子转移进行解释。     

表面活性剂TX-100与SDBS胶束中光解苯甲醛自由基的化学诱导动态电子极化

利用时间分辨ESR波谱仪，研究了苯甲醛在乙二醇和表面活性剂SDBS，TX-100 的胶束溶液中的激光光解化学诱导动态电子极化（CIDEP）现象。苯甲醛在激光照 射下可以从体系和自身中得到氢生成α-羟基苄自由基和苯酰自由基，在SDBS胶束 中是自由基对机理RPM极化，而在TX-100胶束中是三重态机理TM极化。计算机模拟 谱图进一步证实了自由基的产生和极化机理。     

胶束微环境下光解苯半醌负离子基的CIDEP研究

用高时间分辨电子自旋共振(TRESR)波谱仪, 研究对苯醌(PBQ)在不同的介质中光解苯半醌自由基的化学诱导动态电子自旋极化(CIDEP)。实验结果指出, 在乙二醇溶液中得到苯半醌自由基(PBQH)和以碳为中心的自由基R(OH)2。在乙二醇/水溶液中, 得到以PBQH的六条峰为主的谱线图, 然后在该体系中随着加入表面活性剂TX-100, AOT的浓度增加, 苯半醌负离子基(PBQ^-)的谱线强度增加, 而PBQH的谱线减弱直至消失。本文从自由基所处微环境性质出发, 讨论其极化传递机理和有关物理化学性质。     

有机锡化合物光解活泼自由基的ESR研究

本文用自旋捕捉技术与ESR相结合的方法,研究了六种有机锡化合物的光解反应历程。结果表明:有机锡化合物紫外光照时,碳-锡键发生均裂,产生碳中心和锡中心自由基。其中碳中心自由基易被捕捉剂α-苯基-N-特丁基氮氧化物(PBN)或2,3,5,6-四甲基亚硝基苯(ND)所捕获;而锡中心自由基可与菲醌形成稳定的环状加合物。由于环状加合物中配体的不同,产生的空间效应也不同,从而导致加合物中的未偶电子云密度发生变化,给出相异的ESR信号。     

富勒烯瞬态粒子的脉冲辐解和激光光解研究

C_60和C_7激发三重态产生于激光的直接激发,或经由溶剂激发分子向C_60和C_70的能量转移.C_60阳离子自由基既产生于CCl_4阳离子自由基向C_6.的空穴转移,又产生于C_60激发三重态向CCl_4的电子转移.C_60和C_70经由2种不同机理与三氯甲基或二氯甲基自由基生成加成自由基     

具有快速动力学特征的苯醌衍生物电极材料在水系质子电池中的设计和研究

含氧化还原活性基团的苯醌衍生物,在水系质子电池里是一种比容量高、资源丰富的理想电极材料,然而其高溶解性和低的工作电压不利于质子电池的循环稳定性和能量密度的提升,引入吸电子基团不仅可以降低其LUMO能量来提升其反应电位,还可以一定程度上抑制其溶解来提升稳定性。因此,通过电化学研究并对比了3种不同的苯醌化合物作为质子电池的电极材料,研究了不同氯取代情况造成的影响。其中四氯取代的四氯苯醌（4ClBQ）反应电位最高（0.51 V vs. Ag/AgCl）,多电子氧化还原反应机制使其在水系质子电池里具有158 mAh/g的出色容量和高的倍率性能,并且氯取代有效抑制了溶解,在1 A/g的电流密度下也能稳定循环超过1200圈,显示出优异的性能。最后通过探究了电荷的快速反应动力学特征解释了出色的倍率性能。该研究表明,通过引入-Cl基团改进的4Cl-BQ,能进一步提升其在电池里综合性能,是一种极具发展潜力的水系质子电池材料。     

取代苯肼及其冠醚络合物光解行为的研究

冠醚金属离子络合物中，金属离子与配体间的静电作用是早已熟知的．后来发现一些中性分子如硝基苯胁、苯胺等亦能与冠醚形成络合物．硝基苯胁作为谈基试剂广泛用于有机化学研究，但由于其在有机溶剂中低的溶解度，一些苯晚的形成常常必须在高极性溶剂和高温下进行，从而导致一些不利的副反应．苯防与冠醚形成络合物后则可大大提高其在有机溶剂中的溶解度，并且还明显地改变其稳定性．由于这些络合物，主体与客体间的作用与生物体系中受体一基质络合物相似，其成键本质及络合物中客体性质的变化引起人们极大兴趣·1980年首次报导了苯时及取代…     

激光光解CHBr3+O2体系的FTIR-TRS研究

紫外光解CHBr_3被认为是产生有着重要意义的CH 自由基的主要途径,Lin首先用闪光光解法研究了CHBr_3+O_2体系的真空紫外光解.我们用自行设计的分子光解时间分辨富里叶红外发射谱仪(FTIR-TRS),重新研究了这一体系在193nm 的光解反应,得出了一些与前人不同的结果.我们仪器的工作原理已做过详细的描述,这里在光解室里注入了混合的约5Pa 的CHBr_3(Baker 公司试剂,未进一步纯化)和230Pa 的O_2(北京氧气厂电子级高纯氧),用35mJ     

在光动力光疗中类卟啉稀土配合物光敏作用原初反应的特征: 产生自由基I型机制的ESR研究

本文用ESR方法研究了类卟啉稀土配合物[(CO_2H-APPC)Gd]Cl_2的光敏反应.用4-hydro-tetramethylpiperidine-N-oxide radical(4-hydro-TEMPO)作探针,通过对其消自旋的作用,证实[(CO_2H-APPC)Gd]Cl_2光敏反应中有阳离子自由基[(CO_2H-APPC)Gd]~(+)产生,加入还原剂可促使[(CO_2H-APPCGd]~+生成.经由5,5-Dimethyl-1-pyrroline N-oxide(DMPO)对超氧阴离子(O_2~-)和羟基自由基(·OH)的自旋捕捉及对该自旋加合物[DMPO-O_2~-]和[DMPO-OH]的ESR测定,证实有O_2~-和·OH产生,并用SOD清除O_2~-和甲酸钠清除·OH的实验,进一步证实O_2~-和·OH的产生.上述结果说明[(CO_2H-APPC)Gd]Cl_2光敏反应存在着产生[(CO_2H-APPC)Gd]~+和活性氧自由基的Ⅰ型机制.     

Initial Radical Separation after Photolysis of 2,2′‐Azobis(isobutyronitrile) (AIBN) in Solution: Modeling the Primary Cage Effect for Polar Radicals

There is a contradiction as to the initial spatial separation r_i of the two transient 2‐cyanoprop‐2‐yl radicals (Me₂ ? CN) formed by flash photolysis of 2,2′‐azobis(isobutyronitrile) (AIBN) in solvents of various viscosities. The cage effect, expressed in terms of the in‐cage termination probability of the resulting radicals, is predicted correctly by classical Langevin models assuming a decrease of r_i with increasing viscosity. However, the electron‐spin polarization of the radicals escaping the primary cage clearly indicates that the initial separation distance r_i is independent of the solution viscosity. This obvious discrepancy can be reconciled by accounting for the strong electric dipole moments of these radicals and the resulting inter‐radical dipole? dipole interaction potential. We propose a primary‐caging model for polar radicals in solution based on an attractive inter‐radical mean‐force potential. The model is applied to the flash photolysis of AIBN and shown to describe properly the viscosity dependence of both the in‐cage termination probability (cage effect) and the electron‐spin polarization of the escaping 2‐cyanoprop‐2‐yl radicals.     

Hanns Fischer: Radical Pioneer

For four decades, Hanns Fischer played a major and highly innovative role in the development of free radical chemistry. The present article describes the science in several of Fischer's papers. These papers were chosen for analysis because they nicely illustrate Fischer's originality, passion for exactitude, and impact on chemistry, and because they are well‐read favorites of the present authors.     

Photochemical Reactions and Photoinduced Electron‐Transfer Processes in Liquids,Frozen Solutions,and Proteins as Studied by Multifrequency Time‐Resolved EPR Spectroscopy

In this overview, modern multifrequency EPR spectroscopy, in particular at high magnetic fields, is shown to provide detailed information about structure, motional dynamics, and spin chemistry of transient radicals and radical pairs occurring in photochemical reactions. Examples discussed comprise photochemical reactions in liquid solution and light‐initiated electron transfer processes both in biomimetic donor–acceptor model systems in frozen solution or liquid crystals and in natural photosynthetic‐reaction‐center protein complexes. The transient paramagnetic states exhibit characteristic electron polarization (CIDEP) effects. They contain valuable information about structure and dynamics of the transient reaction intermediates. Moreover, they are exploited for signal enhancement. Continuous‐wave (cw) and pulsed versions of time‐resolved high‐field EPR spectroscopy, such as cw‐transient‐EPR (TREPR) and pulsed‐electron‐spin‐echo (ESE) experiments, are compared with respect to their advantages and limitations for the specific system under study. For example, W‐band (95‐GHz) TREPR spectroscopy in conjunction with a continuous‐flow system for light‐generated short‐lived transient spin‐polarized radicals of organic photoinitiators in solution was performed with a time resolution of 10 ns. The increased Boltzmann polarization at high fields even allows detection of transient radicals without CIDEP effects. This enables one to determine initial radical polarization contributions as well as radical‐addition reaction constants. Another example of the power of combined X‐band and W‐band TREPR spectroscopy is given for the complex electron‐transfer and spin dynamics of covalently linked porphyrin–quinone as well as Watson–Crick base‐paired porphyrin–dinitrobenzene donor–acceptor biomimetic model systems. Furthermore, W‐band ESE experiments on the spin‐correlated coupled radical pair in reaction centers of the purple photosynthetic bacterium Rb. sphaeroides reveal details of distance and orientation of the pair partners in their charge‐separated transient state. The results are compared with those of the ground‐state P₈₆₅Q_A. The high orientation selectivity of high‐field EPR provides single‐crystal‐like information even from disordered frozen‐solution samples. The examples given demonstrate that high‐field EPR adds substantially to the capability of ‘classical’ spectroscopic and diffraction techniques for determining structure–dynamics–function relations of biochemical systems, since transient intermediates can be observed in real time in their working states on biologically relevant time scales.     

原子转移自由基聚合法制备侧链型磺化聚醚醚酮阳离子交换膜

以二氟二苯甲酮、双酚A和邻甲基氢醌为单体先经缩聚反应生成聚醚醚酮(PEEK),PEEK经修饰合成含有溴异丙基侧基的聚醚醚酮,以此为原子转移自由基聚合(ATRP)大分子引发剂,通过ATRP法聚合,在PEEK主链上接枝引入聚苯乙烯磺酸钠侧链,得到侧链型PEEK接枝聚合物(PEEK-g-StSO3Na)。 用傅里叶变换红外(FTIR) 光谱、核磁共振氢谱(1H NMR)、热重分析(TG)和扫描电子显微镜(SEM)等技术手段对PEEK-g-StSO3Na的结构进行表征。 结果表明,苯乙烯磺酸钠成功的被接枝到聚醚醚酮主链上,PEEK-g-StSO3Na膜具有明显的亲水疏水微相分离结构,磺酸基团相互聚集形成离子通道,离子交换容量为2.034 mmol/g的PEEK-g-StSO3Na膜的电导率为8.34×10-2 S/cm,膜的尺寸稳定性优于Nafion 117。     

侧链磺化型含氟聚芳醚质子交换膜的制备及性能

在含氟聚芳醚侧链引入磺化萘酚基团,制备了一类侧链磺化型含氟聚芳醚(s SPFAE),采用溶液浇铸法制膜并对膜进行了表征和分析.制备的膜材料离子交换容量达到1.42~2.03 mmol/g,均透明柔韧,杨氏模量高于1.0 GPa,拉伸应变达到66%~105%.吸水性及膨胀性测试结果表明该系列膜具有较低的吸水率和良好的尺寸稳定性,在测试温度范围内(30~90℃)吸水率为21%~51%,尺寸变化率低于7%.s SPFAE膜具有良好的热稳定性及氧化稳定性,TGA测试中320~360℃时的重量损失低于5%,在Fenton溶液中80℃处理1 h后的失重率小于2%.同时,该系列膜表现出较高的电导率水平,如SPFAE-0.8膜(IEC=2.03 mmol/g)在80℃时电导率达到217 m S/cm.     

Search for highly resolved electron spin resonance spectra of the transient radical in radical polymerization

The detection of highly resolved spectra in electron spin resonance (ESR) measurements of radical polymerization is presented. Well‐resolved ESR spectra of the propagating radical were detected in the radical polymerization of several vinyl monomers with a specially designed cavity and cell. More highly resolved ESR spectra of the propagating radicals of vinyl and diene compounds were observed with aconventional spectrometer without the specially designed cavity and cell. On the basis of the ESR spectra, propagation rate constants and dynamic behavior of propagating radicals are discussed. Moreover, the application of time‐resolved ESR spectroscopy to research on the initiation process in radical polymerization is shown. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 269–285, 2002     

Environmental application of elemental speciation analysis based on liquid or gas chromatography hyphenated to inductively coupled plasma mass spectrometry—A review

In recent years the number of environmental applications of elemental speciation analysis using inductively coupled plasma mass spectrometry (ICP-MS) as detector has increased significantly. The analytical characteristics, such as extremely low detection limits (LOD) for almost all elements, the wide linear range, the possibility for multi-elemental analysis and the possibility to apply isotope dilution mass spectrometry (IDMS) make ICP-MS an attractive tool for elemental speciation analysis. Two methodological approaches, i.e. the combination of ICP-MS with high performance liquid chromatography (HPLC) and gas chromatography (GC), dominate the field. Besides the investigation of metals and metalloids and their species (e.g. Sn, Hg, As), representing “classic” elements in environmental science, more recently other elements (e.g. P, S, Br, I) amenable to ICP-MS determination were addressed. In addition, the introduction of isotope dilution analysis and the development of isotopically labeled species-specific standards have contributed to the success of ICP-MS in the field. The aim of this review is to summarize these developments and to highlight recent trends in the environmental application of ICP-MS coupled to GC and HPLC.