355 nm光照下大气液相中HNO2与C6H5Cl的反应机理

利用瞬态吸收光谱技术进行了有氧、无氧条件下氯苯与亚硝酸水溶液的交叉反应机理研究，初步考察了这些瞬态物种的生长与衰减等行为, 并对其光解产物进行了GC/MS分析.研究表明，HNO₂在355 nm紫外光的照射下可产生•OH自由基, •OH和氯苯反应生成C₆H₅Cl•••OH，反应速率常数为（6.6～7.0）×10⁹ L•mol^-1•s^-1; 在有氧条件下C₆H₅Cl•••OH可氧化为C₆H₅Cl•••OHO2, 反应速率常数为(1.6 ± 0.2)×109 L•mol^-1•s^-1,然后进一步分解; C₆H₅Cl•••OH衰减或与亚硝酸等作用可形成多种含硝基的化合物或醌类物质.     

NdCl3-CdCl2-HCl-H2O的相平衡及其固相化合物的研究

测定了四元系NdCl₃-CdCl₂-HCl-H₂O(298. 15 K) 的相平衡溶度数据, 绘制了相应的溶度图. 该四元系是由4个固相区CdCl₂•H₂O(原始盐)、9CdCl₂•NdCl₃•20H₂O、5CdCl₂•NdCl₃•13H₂O、NdCl₃•6H₂O(原始盐)组成的复杂体系. 用X射线粉末衍射及TG-DTG和荧光光谱对9CdCl₂•NdCl₃•20H₂O 和5CdCl₂•NdCl₃•13H₂O进行了研究. 荧光研究表明, 化合物9CdCl₂•NdCl₃•20H₂O具有微弱的荧光强度, 5CdCl₂•NdCl₃•13H₂O的荧光强度则相对大于9CdCl₂•NdCl₃•20H₂O的. 对X射线粉末衍射进行了指标化.     

266 nm光照下水溶液中氯苯与H2O2的反应机理研究

利用瞬态吸收光谱技术研究了不同条件下C₆H₅Cl与H₂O₂水溶液的激光闪光光解情况, 初步考察了其瞬态物种的生长和衰减等行为. 研究表明, •OH自由基和C₆H₅Cl反应生成C₆H₅Cl-OH adduct, 其反应速率常数在近中性、酸性条件下约为(5.89±0.65)×10⁹和(7.07±0.61)×10⁹ L•mol^－1•s^－1; 其衰减则符合双分子二级反应, 速率常数2k/εl＝1.1×10⁶ s^－1, 而在碱性时则为(4.34±0.51)×10⁹ L•mol^－1•s^－1, 衰减呈准一级反应, 速率常数为2.11×10⁵ s^－1. 在有氧条件下, O₂与C₆H₅Cl-OH adduct反应生成C₆H₅Cl-OHO₂ adduct, 其反应速率常数为6.8×10⁸ L•mol^－1•s^－1.     

液相OH•, NO3•和SO4•-与二甲基硫反应机理

利用激光闪光光解技术研究了液相二甲基硫(DMS)与OH^•, NO₃^•和SO₄^•-自由基的微观反应机理. 实验结果表明: 在pH 5～9时, OH^•氧化DMS生成DMSOH^•, DMSOH^•会与DMS反应生成(DMS)₂⁺; 而NO₃^•和SO₄^•-;会直接氧化DMS生成DMS^＋, 生成的DMS^＋会与DMS反应生成(DMS)₂⁺.(DMS)₂⁺与氧气的反应很慢, 它的衰减受pH影响较大.     

266 nm光照下水溶液中氯苯与H2O2的反应机理研究

利用瞬态吸收光谱技术研究了不同条件下C₆H₅Cl与H₂O₂水溶液的激光闪光光解情况, 初步考察了其瞬态物种的生长和衰减等行为. 研究表明, •OH自由基和C₆H₅Cl反应生成C₆H₅Cl-OH adduct, 其反应速率常数在近中性、酸性条件下约为(5.89±0.65)×10⁹和(7.07±0.61)×10⁹ L•mol^－1•s^－1; 其衰减则符合双分子二级反应, 速率常数2k/εl＝1.1×10⁶ s^－1, 而在碱性时则为(4.34±0.51)×10⁹ L•mol^－1•s^－1, 衰减呈准一级反应, 速率常数为2.11×10⁵ s^－1. 在有氧条件下, O₂与C₆H₅Cl-OH adduct反应生成C₆H₅Cl-OHO₂ adduct, 其反应速率常数为6.8×10⁸ L•mol^－1•s^－1.     

[Me3NC2H4OH]Zn2Cl5水溶液的激光光解研究

利用时间分辨激光光解技术研究了季铵盐型离子液体[Me₃NC₂H₄OH]Zn₂Cl₅(简写R-Zn₂Cl₅)的光解行为, 研究发现离子液体能被266 nm激光单光子电离, 生成阳离子自由基、[Zn₂Cl₅]^•中性自由基和水合电子, 观察到胆碱激发三线态的存在, 并测定了离子液体光电离的量子产额为0.04. 利用266 nm激光对离子液体、胆碱、氯化锌、氯化钠的光解行为比较, 发现胆碱阳离子的贡献很小, [Zn₂Cl₅]^－阴离子起主要作用. 采用氧化性自由基SO₄^•－引发离子自由基, 揭示其光电离机理, 测定离子液体的动力学反应速率常数, SO₄^•－ 460 nm的衰减速率常数为1.3×10⁹ L•mol^－1•s^－1, 320 nm离子自由基瞬态产物的生成速率常数为1.5×10⁹ L•mol^－1•s^－1, 两者很接近, 说明SO₄^•－自由基的衰减与瞬态自由基的生成是同步的.     

一种含吲哚咪唑基Ru(II)配合物的酸碱性质和与DNA相互作用的研究

合成了一个新的Ru(II)配合物[Ru(bpy)₂(H₂iip)](ClO₄)₂•5H₂O [bpy＝2,2'-联吡啶, H₂iip＝2-吲哚基-咪唑并[4,5-ƒ][1,10]-邻菲罗啉]. 通过酸碱滴定发射光谱测定了该配合物的表观电离常数; 用紫外可见光谱、荧光光谱、稳态荧光淬灭、溴化乙锭竞争键合、粘度测量和DNA裂解实验研究了配合物与DNA的相互作用性质. 结果表明配合物以经典的插入模式与DNA键合, 键合常数K_b＝(5.97±0.27)×10⁵ mol^－1•L (50 mmol/L NaCl).     

Criegee自由基CH2O2与H2O反应机理及动力学的理论研究

在6-311＋G(2d,2p)水平下, 采用密度泛函理论(DFT)的B3LYP方法, 研究了Criegee 自由基CH₂O₂与H₂O的反应. 结果表明反应存在三个通道: CH₂O₂＋H₂O®HOCH₂OOH (R1); CH₂O₂＋H₂O®HCO＋OH＋H₂O (R2); CH₂O₂＋H₂O®HCHO＋H₂O₂ (R3), 各通道的势垒高度分别为43.35, 85.30和125.85 kJ/mol. 298 K下主反应通道(R1)的经典过渡态理论(TST)与变分过渡态理论(CVT)的速率常数k^TST与k^CVT均为2.47×10^－17 cm³•molecule^－1•s^－1, 而经小曲率隧道效应模型(SCT)校正后的速率常数k^CVT/SCT为 5.22×10^－17 cm³•molecule^－1•s^－1. 另外, 还给出了200～2000 K 温度范围内拟合得到的速率常数随温度变化的三参数Arrhenius方程.     

•OH对聚二甲基硅氧烷乳液辐射效应的影响

通过凝胶和溶胶分析与分子量测定的方法，研究了不同体系下，^•OH对PDMS乳液γ辐射效应的影响. 结果表明，^•OH不仅可引发聚二甲基硅氧烷的分子间交联，也能促进其降解. 对于纯PDMS乳液，在所研究的剂量范围内，^•OH对其辐射交联行为影响较小. 但若体系中加入H2O2、KIO4 和 N2O这些提高^•OH生成产额的添加剂时，^•OH对PDMS的促降解作用会随着吸收剂量增加而表现更明显，导致凝胶含量与纯乳液辐照情况相比下降较多. 即使加入交联剂-三羟甲基丙烷三甲基丙烯酸酯（TMPTMA），在过量的^•OH存在下，当吸收剂量大于40 kGy以上时，TMPTMA不仅没有提高交联度，反而会与^•OH协同，使PDMS的凝胶含量下降更显著，同时产生更多的小分子聚合物，并使PDMS的平均分子量分布变窄. 这可能是由于交联剂首先与^•OH作用，形成的产物会加快PDMS的降解.     

香草醛缩多胺Schiff碱Co(II)配合物固相合成及氧合性能研究

采用固相反应合成了三个新的席夫碱钴(II)配合物, 在室温下, 将其与O₂作用, 1 mol配合物吸收2 mol O₂, 得到三种固态氧合配合物[Co•(L₁)₂•(O₂)₂](NO₃)₂•2H₂O [L₁＝N,N-二(4-羟基-3-甲氧基苯亚甲基)二乙烯三胺], [Co•(L₂)₂•(O₂)₂](NO₃)₂•2H₂O [L₂＝N,N-二(4-羟基-3-甲氧基苯亚甲基)三乙烯四胺]和[Co•(L₃)₂•(O₂)₂](NO₃)₂•2H₂O (L₃＝N,N-二(4-羟基-3-甲氧基苯亚甲基)四乙烯五胺]. 通过元素分析、红外光谱、核磁共振氢谱(¹H NMR), TG/DTA、摩尔电导率、紫外等测试手段确定了氧合配合物的组成. 采用失重法测定了氧合配合物中的配位氧, 确定1 mol钴配合物吸收2 mol O₂, 其中1 mol O₂用来和钴离子配位形成超氧配合物.     

Kinetics of the ?OH-radical initiated reactions of acetic acid and its deuterated isomers

Kinetics of the ^•OH-initiated reactions of acetic acid and its deuterated isomers have been investigated performing simulation chamber experiments at T = 300 ± 2 K. The following rate constant values have been obtained (± 1σ, in cm³ molecule⁻¹ s⁻¹): k ₁(CH₃C(O)OH + ^•OH) = (6.3 ± 0.9) × 10⁻¹³, k ₂(CH₃C(O)OD + ^•OH) = (1.5 ± 0.3) × 10⁻¹³, k ₃(CD₃C(O)OH + ^•OH) = (6.3 ± 0.9) × 10⁻¹³, and k ₄(CD₃C(O)OD + ^•OH) = (0.90 ± 0.1) × 10⁻¹³. This study presents the first data on k ₂(CH₃C(O)OD + ^•OH). Glyoxylic acid has been detected among the products confirming the fate of the ^•CH₂C(O)OH radical as suggested by recent theoretical studies.     

Effect of electron-withdrawing power of the substituted group on?OH radical reaction with substituted aryl sulphides: A pulse radiolysis study

In neutral aqueous solution of (phenylthio)acetic acid, hydroxyl radical is observed to react with a bimolecular rate constant of 7.2 × 10^-1 dm³ mol⁻s⁻ and the transient absorption bands are assigned to^•OH radical addition to benzene and sulphur with a rough estimated values of 50 and 40% respectively. The reaction of the^•OH radical with diphenyl sulphide (k = 4.3 × 10⁸ dm³ mol⁻¹ s⁻¹) is observed to take place with formation of solute radical cation, OH-adduct at sulphur and benzene with estimated values of about 12, 28 and 60% respectively. The transient absorption bands observed on reaction of^•OH radical, in neutral aqueous solution of 4-(methylthio)phenyl acetic acid, are assigned to solute radical cation (λ_max = 550 and 730 nm), OH-adduct at sulphur (λ_max = 360 nm) and addition at benzene ring (λ_max = 320 nm). The fraction of^•OH radical reacting to form solute radical cation is observed to depend on the electron-withdrawing power of substituted group. In acidic solutions, depending on the concentration of acid and electron-withdrawing power, solute radical cation is the only transient species formed on reaction of^•OH radical with the sulphides studied.     

Reaction of hydroxyl radicals with S-nitrosothiols: Formation of thiyl radical (RS?) as the intermediate

The decomposition studies of S-nitrosothiols (RSNO) are important due to their potential role in vivo in connection with the storage and transport of nitric oxide (^•NO) within the body. Reactions of hydroxyl radicals (^•OH) with a number of RSNOs (S-nitroso derivatives of N-acetyl-dl-penicillamine, l-cysteinemethylester, N-acetylcysteamine, and dl-penicillamine) in aqueous medium at neutral and acidic pH have been reported in the present study. Radiation chemical technique (steady state and pulse radiolysis) has been utilized for the determination of the reaction rate constants, the end product analyses, and the transient intermediate species. The rate constants for the reaction of ^•OH with the selected RSNOs were determined using a competition kinetic method with 2′-deoxy-d-ribose as the competitor. All the rate constants were found to be of the order of diffusion controlled (10¹⁰ M⁻¹ s⁻¹). The degradation yield of RSNOs was found to be quantitative (i.e., G(–RSNO) ≈ G(^•OH)) at neutral and acidic pH. The major products of decomposition were the respective disulfide (RSSR) and nitrite (NO₂ ⁻). A good material balance is also obtained between the degradation yield and the formation of the products (i.e., G(–RSNO) ≈ G(RSSR) + G(NO₂ ⁻)). The major transient intermediate was the thiyl radical (RS^•). Its intermediacy was confirmed by making use of the electron transfer reaction of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS²⁻) to RS^•, which results in the formation of ABTS^•− having a transient absorption spectrum with λ_max at 410 nm. Based on these results, a generalized reaction mechanism is deduced for the reaction of ^•OH with RSNO.     

Oxidation reactions of 1,3-diphenylpropane-1,3-dione

The free radical scavenging properties and possible antioxidant activity of 1,3-diphenylpropane-1,3-dione (1) are reported. Pulse radiolysis technique was employed to study the one-electron oxidation of 1 with various radicals viz. CCl₃O₂ ^•, N₃ ^• and^•OH in homogeneous aqueous solution. All these radicals reacted with 1 under ambient conditions at almost diffusion controlled rates producing transient species with an absorption maximum around 420 nm that decayed at first order rates. The transient absorption peak was shifted in the case of CCl₃OO^• radical reaction with 1 due to change in the polarity of the medium. Formation of a stable product with a broad absorption band starting from 400 nm and cut off at 230 nm was observed in the oxidation of 1 with^•OH and^•N₃ radicals. In a biological system also, 1 showed significant inhibitory activity against Fe²⁺-mediatedlipidperoxidation. Based on these observations, a suitable mechanism for the oxidation of 1 has been proposed.     

Killing Effects of Hydroxyl Radical on Algae and Bacteria in Ship’s Ballast Water and on Their Cell Morphology

So far there is no an effective method for fast killing of algae and bacteria in the course of conveying ship’s ballast water. With a physical method of strong electric-field discharge, O₂ in air and H₂O in seawater are ionized and dissociated and then dissolved into seawater to generate •OH radicals. In the experimental system of 10 t/h, the algae and bacteria are rapidly killed using •OH radicals with the low •OH concentration of 0.7 mg/L within only 6 s, and D-2 ballast water discharge standard of IMO is realized. Under fluorescence microscope, cell morphological changes such as the disruption of cell membrane, sometimes to the point of cell lysis, has taken place when cells are exposed to a killing dose of •OH.     

Study of Cluster Anions Generated by Laser Ablation of Titanium Oxides: A High Resolution Approach Based on Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Laser ablation of titanium oxides at 355 nm and ion–molecule reactions between [(TiO₂)_x]^–• cluster anions and H₂O or O₂ were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO₂)_x(H₂O)_yOH]^– and [(TiO₂)_x(H₂O)_yO₂]^–• oxy-hydroxide species with x = 1 to 25 and y = 1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO₂)_x]^–• cluster anions as was previously reported, and (2) ion–molecule reactions during ion storage. Reactions of some [(TiO₂)_x]^–• cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O₂ loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data.     

Formation of excited uranyl in oxidation of tetravalent uranium with oxygen in HClO<Subscript>4</Subscript> aqueous solutions: IV. Enhancement of the chemiluminescent reaction in the presence of Fe<Superscript>2+</Superscript>

Experimental data that support the hypothesis on the determining role of ^•OH radicals in the emergence of luminescence during the oxidation of U(IV) with atmospheric oxygen in aqueous HClO₄ solutions have been obtained using the H₂O₂-FeSO₄ system as a source of OH radicals. It has been found that brighter chemiluminescence (CL) is observed in the presence of 10⁻⁵ mol/l Fe²⁺ in a 5 × 10⁻⁴ mol/l U(IV) solution in 0.1 mol/l HClO₄ compared with the FeSO₄-free solution. The CL yield in the presence of Fe²⁺ (η_CL = 3.9 × 10⁻⁸) is 2.8 times that in the solution without iron (η_CL = 1.4 × 10⁻⁸). These results can be regarded as a further piece of evidence for the idea that the elementary event of the formation of a CL emitter—electronically excited uranyl ion *(UO₂²⁺)—in radical chain U(IV) oxidation reactions is electron transfer from the uranoyl ion (UO₂⁺) to the oxidant, the ^•OH radical. Thus, one of the main prerequisites for light emission during U(IV) oxidation reactions is a high generation efficiency of ^•OH radicals and their easy access to the uranoyl UO₂⁺ ion.     

Anti- and pro-oxidant properties of sodium 2-mercaptoethane sulphonate (Mesna)

The ^•OH and the NO₂ ^• radicals generated pulse radiolytically in N₂O-saturated aqueous solution at pH 8–8.5 oxidize Mesna to form the corresponding thiyl radicals which on reaction with thiolate ions form an RSSR^{• −} type of transient with λ_max = 420 nm. The rate constants for the formation of these transients were determined. In the absence of O₂ at pH=6, the RS^• radicals formed show an absorption maximum at 360 nm and an ε=200±50 dm³ mol⁻¹ cm⁻¹. The rate constant k (^•OH+RSH) was 6×10⁹ dm³ mol⁻¹ s⁻¹ as determined from competition kinetics. In the presence of O₂ the Mesna thiyl radical was seen to rapidly add oxygen to form an RSOO^• type of species with λ_max = 535 nm, ε=700±50 dm³ mol⁻¹ cm⁻¹ and k (RS^•+O₂)=1.3×10⁸ dm³ mol⁻¹ s⁻¹. Both the RS^• and the RSOO^• radicals formed by the oxidation of Mesna were able to abstract H-atoms from ascorbate ions and k(RS^• +AH⁻)=~k(RSOO^•+AH⁻)=~6−7×10⁸ dm³ mol⁻¹ s^−1-. Moderately strong oxidants like CCl₃OO^• and the (CH₃)₃CO^• radicals, having a reduction potential of +1.4−1.6 V vs NHE were unable to oxidize Mesna. The results thus reflect on the pro- and anti-oxidant properties of Mesna.     

Gas-phase proton-transport self-catalysed isomerisation of glutamine radical cation: The important role of the side-chain

The gas-phase isomerisation reaction of glutamine radical cation from [NH₂CH (CH₂CH₂CONH₂) COOH ]^+• to [ NH₂C (CH₂CH₂CONH₂) C (OH)₂]^+• has been studied theoretically using the MPWB1K functional approach. The [ NH₂ C (CH₂CH₂CONH₂) C (OH)₂]^+• diol species has been found to be the most stable isomer for glutamine radical cation. Moreover, it has been observed that glutamine has a long enough side-chain with basic groups that acts as a solvent molecule favouring the proton-transfer from C _α to COOH group. This fact reduces dramatically the isomerisation energy barriers compared to the same process for glycine radical cation in gas phase. Thus, this reaction can be considered as an example of gas-phase proton-transport catalysed reaction in which the proton-transport is carried out by the reactant molecule itself instead of any solvent. Contribution to the Serafin Fraga Memorial Issue.     

Reactions of reducing radicals with 2- and 3-nitroanilines in aqueous solutions: a pulse radiolysis study

Reactions of 2- and 3-nitro anilines (2- and 3-NA) with e_aq⁻, H-atoms and one-electron reductants have been studied using pulse radiolysis in aqueous solutions. Reactions of e_aq⁻ were found to be quite fast with both 2-NA and 3-NA resulting in their corresponding semi-reduced species which are reducing in nature. Reduction potentials for 2-NA/2-Na^•′ have been estimated to be approx. −0.56 Vvs. NHE and that for 3-NA/3-NA^•− was found to be between −0.185 V and −0.45 Vvs. NHE. Semi-reduced 2-NA has main absorption peak at 300 nm with a shoulder in the 350 nm region and a broad weak band in the 470–500 nm region, whereas semi-reduced 3-NA possesses an absorption peak at 520 nm. Reducing radicals such as (CH₃)₂ C^•OH and CO₂^•− reacted with 2-NA, producing semi-reduced species, whereas reactions of these radicals with 3-NA produced their corresponding radical-adduct species.