喹喔啉系列衍生物在乙腈体系中的激光光解研究

利用时间分辩激光诱导瞬态吸收光谱装置，以266nm激光为激发光源，两种喹喔啉衍生物为光敏剂，三种缺电子烯为猝灭剂，得到了喹喔啉衍生物激发三重态在乙腈体系中的瞬态吸收光谱，并且测定了喹喔啉衍生物的激发三重态自猝灭反应动力学常数以及缺电子烯对三重态的猝灭反应动力学常数．此外，还以2，3-二甲基萘为光敏剂作为比较，给出一系列的猝灭速率常数，阐明了猝灭反应的机理.     

电子激发态CCl2自由基被H2O猝灭的研究

对CCl4/Ar混合气体直流脉冲放电产生CCl2自由基,再用541．52nm激光将电子基态CCl2激励到激发态A1B21（0,4,0）振动态的K＝0能级上,通过检测激发态CCl2时间分辨荧光信号,测得室温下CCl2（A1B1和a^3B1)被H2O分子猝灭的实验结果,用三能级模型分析处理实验数据,获得态分辨速率常数KA和Ka值,利用UMP2（Full）／6－31G（d,p）方法计算了该反应的势能面,揭示了反应的插入和加成－消除机理。     

The v-v energy transfer of highly vibrationally excited states (I)

The relaxation of the highly vibrationally excited CO (v = 1–8) by CO₂ is studied by timeresolved Fourier transform infrared emission spectroscopy (TR FTIR). 193 nm laser photolysis of the mixture of CHBr₃ with O₂ generates the highly vibrationally excited CO(v) molecules. TR FTIR records the intense infrared emission of CO(v→v-1). The vibrational populations of each level of CO(v) have been determined by the method of spectral simulation. Based on the evolution of the time resolved populations and the differential method, 8 energy transfer rate constants of CO(v = 1–8) to CO₂ molecules areobtained: (5.7±0.1), (5.9±0.1), (5.2±0.2), (3.4±0.2), (2.4±0.3), (2.2±0.4), (2.0±0.4) and (1.8±0.6) (10¹⁴ cm³ · molecule⁻¹ · s⁻¹), respectively. A two-channel energy transfer model can explain the feature of the quenching of CO(v) by CO². For the lower vibrational states of CO, the vibrational energy transfers preferentially to the u³ mode of CO² For the higher levels, the major quenching channel changes to the vibrational energy exchange between CO(v→v-1) and the u¹ mode of CO².     

Electron transfer in N-butylpyridinium tetrafluoroborate ionic liquid by pulse radiolysis

The radiolysis behavior of neat pyridinium ionic liquids (ILs) and their aqueous solutions was investigated using nanosecond pulse radiolysis techniques. Radiolysis of the ionic liquids, such as N-butylpyridinium tetrafluoroborate (BuPyBF4 ), resulted in the formation of solvated electrons and organic radicals. Solvated electrons reacted with the pyridinium moiety to produce a pyridinyl radical, which can transfer electrons to various acceptors. The electron-transfer rate constants of the solvent-derived butylpyridinyl radicals in BuPyBF 4 and in several compounds (for example, duroquinone, 4,4′-pyridine, benzophenone, and 1,1′- dimethyl-4,4′-bypyridinium dichloride) (k of the order 10 8 L/(mol s) were lower than those measured in water and in i-PrOH but were significantly higher than the diffusion-controlled rate constants estimated based on viscosity. The electron-transfer rate constants in neat BuPyBF 4 were one order of magnitude faster than the diffusion-controlled values. This finding suggests that Bu- PyBF 4 acts not only as solvent but also as active solute, such as in solvent-mediated reactions. These reactions result in electrons reaching their final destinations via intervening pyridinium groups without requiring the diffusion of a specific radical.     

流体室温磷光法研究紫精衍生物与萘之间光诱导电子转移

在室温下以276 nm的光激发,紫精衍生物能够强烈猝灭萘的室温磷光.利用Sterner-Vohmer方程线性回归分析了实验结果,获得了不同猝灭剂紫精衍生物对萘室温磷光的猝灭常数KSV,在1.59×106~6.60×106L/mol之间.同时紫精衍生物的取代基碳链越长,其对萘室温磷光的猝灭常数越小.分析表明,导致萘室温磷光猝灭的原因是从萘到紫精衍生物的三重态电子转移过程.     

Studies on kinetics of reactions between phycobiliproteins and hydroxyl radicals by a pulse radiolytic technique

Scavenging of hydroxyl radical (· OH) by phycobiliproteins (C-phycocyanin, Allophycocyanin and R-phycoerythrin) was studied by competitive kinetics methods. Hydroxyl radicals were generated from pulse radiolysis of aqueous systems saturated with nitrous oxide (N₂O). The experimental results indicated that the three types of phycobiliproteins are all strong scavengers of · OH, the rate constants are around (2.8-5.6)×10⁹ L · mol^-1 · s^-1.     

The impact of HS radicals on the measured rate constant of H<Subscript>2</Subscript>S with OH radicals

The rate constant for the reaction of OH radicals and hydrogen sulfide (H₂S) was studied in different bath gases (including N₂, air, O₂ and He) by using relative technique at 298 K. The small difference of the measured rate constants between N₂ and those with the presence of O₂ suggested possible influence of HS self reaction. Further experiments with NO_x presence for scavenging HS demonstrated this assumption. The rate constant of (5.48±0.12) ×10^–12 cm³ molecule^–1 s^–1 obtained with 4.09 ×10^–4 mol m₃ NO presence may be accurate for estimating the atmospheric lifetime of H2S. The results provided circumstantial evidence that the rapid reaction of HS with N₂O is suspected.     

高效液相色谱法测定猝灭剂与单重态氧反应速度常数

提出用反相高效液相色谱法测定文题常数。以十八烷基键合相为固定相,以甲醇作流动相,样品经光照处理,测定时无其它干扰。测定了五种不同类型猝灭剂与单重态氧的物理猝灭速度常数和化学猝灭速度常数。结果表明,猝灭剂猝灭单重态氧的过程中,物理猝灭过程是主要的。物理猝灭速度常数和总猝灭速度常数愈大,在一定范围内,品红甲亚胺染料的防褪色效果愈好。     

Effect of CH3OOH on the atmospheric concentration of OH radicals

Methyl hydroperoxide (CH₃OOH, MHP) is known to be a significant sink and reservoir of HO_x and RO_x radicals in the atmosphere. In order to investigate the impact of MHP on the concentration of atmospheric OH radicals, two key gas-phase reactions of MHP, i.e. the reactions with OH radicals and with UV photolysis, have been simulated at temperature of 293±2 K and total pressure of 1.01×10⁵ Pa, using the long path Fourier transform infrared (LP-FTIR) spectrometry. OH radicals are generated by the photolysis of O₃ in the presence of water vapor. Combined with the relative rate method, the reaction rate constant of MHP with OH radicals is determined to be (3.99±0.15)×10^-12 cm³?molecule^-1?s^-1, and thus the atmospheric lifetime of MHP is estimated at 2.9 days. Furthermore, from detailed analysis of the UV photolysis of MHP, the yield of OH radicals is obtained to be 0.91±0.04. Based on the MHP atmospheric lifetime and the yield of OH radicals, it is concluded that MHP plays an essential role in the redistribution of OH radicals in the troposphere.     

Effect of CH3OOH on the atmospheric concentration of OH radicals

Methyl hydroperoxide (CH₃OOH, MHP) is known to be a significant sink and reservoir of HO_x and RO_x radicals in the atmosphere. In order to investigate the impact of MHP on the concentration of atmospheric OH radicals, two key gas-phase reactions of MHP, i.e. the reactions with OH radicals and with UV photolysis, have been simulated at temperature of 293±2 K and total pressure of 1.01×10⁵ Pa, using the long path Fourier transform infrared (LP-FTIR) spectrometry. OH radicals are generated by the photolysis of O₃ in the presence of water vapor. Combined with the relative rate method, the reaction rate constant of MHP with OH radicals is determined to be (3.99±0.15)×10^-12 cm³?molecule^-1?s^-1, and thus the atmospheric lifetime of MHP is estimated at 2.9 days. Furthermore, from detailed analysis of the UV photolysis of MHP, the yield of OH radicals is obtained to be 0.91±0.04. Based on the MHP atmospheric lifetime and the yield of OH radicals, it is concluded that MHP plays an essential role in the redistribution of OH radicals in the troposphere.     

The v-v energy transfer of highly vibrationally excited states (II)

The vibrational energy transfer from highly vibrationally excited CO to H₂O molecules is studied by time-resolved Fourier transform infrared emission spectroscopy (TR FTIR). Following the 193 nm laser photolysis of CHBr₃ and O₂ the secondary reactions generate CO(v). The infrared emission of CO(v → v−1) is detected by TR FTIR. The excitation of H₂O molecules is not observed. By the method of the spectral simulation and the differential technique, 8 rate constants for CO(v)/H₂O system are obtained: (1.7 ±0.1), (3.4 ±0.2), (6.2 ±0.4), (8.0 ±1.0), (9.0 ±2.0), (12 ±3), (16 ±4) and (18 ±7) (10¹³cm³ · molecule^-1· s^-1). At least two reasons lead to the efficient energy transfer. One is the contributions of the rotational energy to the vibational energy defect and the other is the result of the complex collision. With the SSH andab initio calculations, the quenching mechanism of CO(v) by H₂O is suggested.     

An explanation to the high efficiency ofm-THPC (temporfin) used in photodynamic therapy

Meso-tetrahydroxylphenyl chlorin (m-THPC) is one of the most efficient prospective sensitizers used in photodynamic therapy (PDT). ESR spectroscopy, fluorescence quenching experiments and cyclic voltammogram measurement were used to study its redox properties. The results showed that the ability of m-THPC generating superoxide radical anions was very strong, and the rate constant of m-THPC fluorescence quenching by oxygen k_q (O₂)=1.46×10¹⁰ mol^-1·s^-1. The values of fluorescence quen- ching rate constant of m-THPC by some other electron acceptors, such as methyl viologen (MV²⁺) and anthraquinone (An), were also measured. And they were k_q (MV²⁺)=5.51×10⁹ mol^-1·s^-1, k_q (An)=7.81×10⁹ mol^-1·s^-1. The oxidation potential of m-THPC was examined to be +0.62 V (vs. NHE) in acetonitrile. All these suggested that m-THPC should be a much stronger electron donor than photofrin, the currently used in clinical photodrug, and may react easily through electron transfer with biological matter to yield various radicals. So it seemed reasonable that the type Ⅰ reaction may play an important role in the high activity of m-THPC-PDT.     

Density functional theory study of the reaction paths of reactions of CH3C(O)O2 radicals with HO2 in the gas phase

A DFT study on the reactions between CH₃C(O)O₂ and HO₂ radicals has been carried out. It is suggested that both the triplet and singlet potential surfaces involve a complex mechanism with the formation of loosely bound intermediate complexes of reactants and products. The reaction prefers to occur on the triplet surface to produce peracetic acid (CH₃C(O)O₂H) and triplet O₂ molecule. The CH₃C(O)O₂H can further convert into CH₃C(O)O and HO radicals.     

Density functional theory study of the reaction paths of reactions of CH3C(O)O2 radicals with HO2 in the gas phase

A DFT study on the reactions between CH₃C(O)O₂ and HO₂ radicals has been carried out. It is suggested that both the triplet and singlet potential surfaces involve a complex mechanism with the formation of loosely bound intermediate complexes of reactants and products. The reaction prefers to occur on the triplet surface to produce peracetic acid (CH₃C(O)O₂H) and triplet O₂ molecule. The CH₃C(O)O₂H can further convert into CH₃C(O)O and HO radicals.     

金属酞菁—球烯复合物光谱行为及热力学性质

利用紫外可见光谱、荧光光谱研究锌酞菁（ＺｎＰｃ）－球烯（Ｃ６０）复合物在不同溶剂体系中的光谱性质．ＵＶ－Ｖｉｓ光谱在７１０ｎｍ附近出现新的特征吸收峰,峰位置与理论计算基本符合,这表明ＺｎＰｃ和Ｃ６０形成了分子间电荷转移复合物（ＣＴＣ）．荧光光谱中激发峰的位移和荧光猝灭低谷现象进一步证实形成了ＺｎＰｃ－Ｃ６０的ＣＴＣ．通过Ｊｏｂ′ｓ光度滴定等方法表明ＺｎＰｃ与Ｃ６０以１∶１和２∶１的复合比生成ＣＴＣ．对ＺｎＰｃ－Ｃ６０在不同温度下的生成平衡常数ＫＣ及热力学性质进行了研究．     

Photosensitized splitting of cis-syn 1,3-dimethyluracil dimer by tryptophan and its peptides

Photosensitized splitting of cis-syn 1,3-dimethyluracil dimer by tryptophan (Trp) and its peptides (Trp-Tyr and Trp-Phe) is studied by fluorescence quenching experiments and irradiation experiments.It reveals that 1,3-dimethyluracil dimer is mainly split by e?-?aq resulting from two-photon ionization of Trp and its peptides under irradiation with light (λ>290 nm).Moreover,the excited singlet state of Trp and its peptides can transfer an electron to the dimer,which splits and gives two pyrimidines.In addition,because of its lower oxidative potential,the excited triplet state of Trp-Tyr can also split the dimer via transfering an electron to the dimer.     

The concentration quenching characteristics of 5D3-7FJ and 5D4-7FJ (J=0―6) transitions of Tb3+ in YBO3:Tb3+ phosphor

The photoluminescence quenching behaviors of ^5D3-^7Fj and ^5D4-^7Fj （J = 0—6） transitions of Tb^3＋ in YBO3：Tb under 130—290 nm excitation were systematically investigated. The results revealed that the quenching concentrations of both ^5D3-^7Fj and ^5D4-^7Fj transitions of Tb^3＋ in YBO3：Tb were mainly dependent on excitation wavelength. Particularly, the quenching concentrations of ^5D4-^7Fj transitions of Tb^3＋ under 130—290 nm excitation were correlated with excitation bands of YBO3：Tb. The quenching concentrations of ^5D3-^7Fj transitions remained at low concentration （2%） under 186—290 nm excitation and then increased gradually with energy of incoming excitation photon when excited at 130—186 nm. This dependence should be involved in their excitation mechanisms and quenching pathway in particular excitation region.[第一段]     

计时电量法测定4,5-二氮芴-9-酮的扩散系数和反应速率常数

运用循环伏安法测定4,5-二氮芴-9-酮（DAFO）在DMF溶液中不同扫描速率时的循环伏安图,出现2对峰形良好的氧化还原峰;采用计时电量法通过控制阶跃电位,测得不同温度下DAFO在DMF溶液中的扩散系数和反应速率常数,293K时扩散系数为5.39×10-6cm2·s-1;当选择阶跃电位使电极过程处于扩散和电化学混合控制时,测得不同电位的反应速率常数k_f. 根据不同温度下的标准速率常数k₀,得到表观活化能E_a为10.5kJ·mol-1.      

T2分子X1Σg+,B1Σu+和C1Πu态的势能函数

 使用SAC/SAC-CI和D95++^**,6-311++g^**及cc-PVTZ基组,分别对T₂分子的基态X¹Σ_g⁺+、第2激发态B¹Σ_u⁺和第3简并激发态C¹Π_u的平衡结构和谐振频率进行优化计算.对所有计算结果进行比较,得出cc-PVTZ基组为最优基组.运用cc-PVTZ基组和SAC方法对基态X¹Σ_g⁺+,SAC-CI方法对激发态B¹Σ_u⁺和Cu 进行单点能扫描计算,并用正规方程组拟合Murrell-Sorbie函数,得到相应电子态的势能函数解析式,由得到的势能函数计算了与X¹Σ_g⁺+,B¹Σ_u⁺和C¹Π_u态相对应的光谱常数,结果与实验数据吻合.     

Resonance-enhanced multiphoton ionization spectroscopy on the B′2Σ+ and B2Π states of NS

Resonance-enhanced multiphoton ionization （REMPI） spectra of N^32S and N^34S have been recorded in the range of 35700-40200 cm^-1. The radical was generated by a pulsed dc discharge of a mixture of SF6 and N2 under a supersonic free jet condition. All the 16 observed bands of N^32S radicals have been assigned, among which 12 bands belong to three transition progressions （v′=0-4, 0）, （v′=1-4, 1） and （v′=2-4, 2） from the X^2П ground state to the B′^2∑^＋ upper state and the rest correspond to （9, 0）, （10, 0）, （11, 0） and （12, 0） bands of B^2П-X^2П transition, respectively. Analysis of the rotationally resolved spectra yields exhaustive spectroscopic constants of both the X^2П ground state and the B′^2∑^＋ excited state. The electronic transition bands of the isotopic molecule N^34S have been rotationally analyzed for the first time and the rotational constants of the ground and upper states have been determined simultaneously.