CH(A^2△和B^2∑^-)和醇类分子碰撞过程动力学研究

本文报道用四倍频YAG激光(266nm)光解CHBr_3产生电子激发态CH(A,B)自由基和测量自发辐射CH(A,B→X)的时间分辨信号的方法测定了室温(290K)下 CH(A,B)被醇类分子(乙醇、异丙醇、正丁醇、异戊醇和叔戊醇)猝灭的速率常数,实验测定的CH(A)和 CH(B)猝灭速率常数K_q~A和K_q~B(单位为10~(-10)cm~3·molecule~(-1)·s~(-1))值如下(误差为线性拟合的标准偏差):此外,还从碰撞配合物模型出发,就醇分子中OH基对猝灭速率常数的影响作了讨论.     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH~3COCH~3,CD~3COCD~3,CF~3CO~2H,CF~3CO~2D,CHCl~3和CDCl~3分子猝灭电子激发态CH(A,B) 自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应. 实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数     

CH(A^2△和B^2∑^-)和醇类分子碰撞过程动力学研究

本文报道用四倍频YAG激光(266nm)光解CHBr3产生电子激发态CH(A,B)自由基和测量自发辐射CH(A,B→X)的时间分辨信号的方法测定了室温(290K)下CH(A,B)被醇类分子(乙醇、异丙醇、正丁醇、异戊醇和叔戊醇)猝灭的速率常数, 实验测定的CH(A)和CH(B)猝灭速率常数k~q^A和k~q^B(单位为10^-^1^0cm^3.molecule^-^1.s^-^1)值如下(误差为线性拟合的标准偏差):此外, 还从碰撞配合物模型出发, 就醇分子中OH基对猝灭速率常数的影响作了讨论。     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH_3COCH_3,CD_3COCD_3,CF_3CO_2H,CF_3CO_2D,CHCl_3和CDCl_3分子猝灭电子激发态CH(A,B)自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应.实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数.     

烷烃类分子对NCO(A2∑+)自由基的猝灭

采用激光光解-激光诱导荧光(LP-LIF)的方法,用266 nm激光光解CHBr3分子产生CH自由基,再与N2O继续反应作为NCO自由基的产生源,用438.6 nm激光将电子基态X2∏i(0010)的NCO激励到激发态A2∑+(00°0)上,通过检测激发态NCO时间分辨荧光信号,测得室温(298 K)下NCO(A2∑+)被烷烃类分子猝灭的实验结果,获得了A2∑+(00°0)态猝灭速率常数.实验发现,随着烷烃分子中C-H键数增加,其猝灭截面也近线性增加,但随着分子体积增大,这种增加趋缓.     

亚稳态SO(c1∑-,v''=0)的猝灭动力学

在流动余辉装置上,研究了SO(c1∑-)的猝灭动力学过程.获得了SO2,O2,CO2,N2,He,CS2,CH3OH,C2H5OH,C3H7OH,C4H9OH,CH3COCH3,C6H6 CH2Cl2,CH2Br,CHCl3,CCl4等16种分子与SO(c1∑-)发生猝灭反应的速率常数.初步分析表明:醇类分子CnH2n+1OH(n=1,2,3,4)中的C-H键的数目与其对SO(c1∑-)的猝灭速率成正比;CO2,N2等非极性无机小分子对SO(c1∑-)的猝灭作用不明显,强极性分子SO2对SO(c1∑-)的猝灭作用较强.卤代烷烃中的卤素原子的大小对SO(c1∑-)的猝灭过程发挥着较重要的作用;而氯代烷烃中氯原子的个数与猝灭速率之间的关系不明显.     

CH(A^2Δ)自由基被醇类分子猝灭动力学的温度效应研究

用266nm激光光解CHBr3产生CH自由基, 利用精密控温仪控制反应温度, 测定CH(A→X)荧光的时间分辨信号, 测量了290K至653K范围内CH(A)被乙醇、丙醇、丁醇猝灭的速率常数, 利用修正的碰撞配合物模型, 定性解释了在多极吸引势与活化势垒的双重影响下, 猝灭截面与温度间的关系。     

CH(A^2Δ)自由基被醇类分子猝灭动力学的温度效应研究

用266nm激光光解CHBr3产生CH自由基, 利用精密控温仪控制反应温度, 测定CH(A→X)荧光的时间分辨信号, 测量了290K至653K范围内CH(A)被乙醇、丙醇、丁醇猝灭的速率常数, 利用修正的碰撞配合物模型, 定性解释了在多极吸引势与活化势垒的双重影响下, 猝灭截面与温度间的关系。     

NH2(A2A1,090,423)的电子猝灭和转动态-态传能

在束 气和束 束实验条件下,详细研究了NH2(A1,090,423)自由基分别与Ar,N2,O2和NH3碰撞引起的电子态猝灭和转动态 态传能,获得了总的猝灭截面σQ (分别为≤0.17、0.26、0.30和0.48 nm2),以及相对转动态 态传能截面.利用碰撞络合物模型计算的电子猝灭截面与实验测得的截面具有基本相同的趋势,表明长程吸引势在猝灭过程中起着重要的作用.同时还发现,转动态 态传能中相对截面随着碰撞对的折合质量的减小而下降.由于NH3具有较大的偶极矩以及O2的开壳层电子结构使得猝灭截面增大,而转动态 态传能截面减小.     

电子激发态SO2(A^1A2, B^1B1)分子的碰撞猝灭动力学研究

用四倍频YAG激光(266nm)把SO2分子从电子基态X^1A1激励到电子激发态A^1A2和B^1B1的高振动耦合区, 通过检测自发辐射SO2(B^1B1→X^1A1)的时间分辨信号, 测定了室温(290K)下SO2(A^1A2, B^1B1)被He, 氯代甲烷分子和某些烷烃分子猝灭的速率常数。此外, 还从碰撞配合物模型出发, 对SO2(A^1A2, B^1B1)的猝灭机制进行了讨论。     

CCl2(A^1B1)自由基不同振动态的猝灭动力学

对CCl4/Ar混合气体直流脉冲放电产生CCl2自由基，再分别用波长为550.56nm,541.52nm,532.25nm,524.31nm,523.82nm和523.27nm的激光将电子基态CCl2激励到激发态A^1B1的(0,3,0),(0,4,0),(1,3,0),(0,6,0),(1,4,0),(2,2,0)振动态，激发态CCl2(A^1B1)的不同振动态的时间分辨荧光信号显示该信号呈双指数衰减，测得室温下CCl2(A^1B1)不同振动态被NH3,H2O,CH2Br2,NH(CH3)2,NH(C2H5)2,N(C2H5)3,n-C6H14等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，并对实验结果进行了讨论。     

Overtone spectra of aniline derivatives

Overtone spectra of 2-ethylaniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline and N,N-diethylaniline have been studied in 2500-15000 cm(-1) region. Vibrational frequency and anharmonicity constants for aryl/alkyl C-H stretch and N-H stretch vibrations have been determined. The effect of substitution of C(2)H(5) group on the ortho position in the ring and CH(3)/C(2)H(5) at the positions of the H-atom in NH(2) group has been studied in these molecules. It is noted that the aryl C-H stretching frequency and the N-H stretching frequency is appreciably increased due to the replacement of H in NH(2) group by CH(3)/C(2)H(5). These experimental observations are well supported by theoretical calculations for charge density on N-atom using molecular orbital AM(1) method.     

Reactions of CH3OCH2+ with hydrocarbons and O,N, and S compounds: applications for chemical ionization in selected ion flow tube studies

We report the results of a flowing afterglow ion source-selected ion flow tube study (FA-SIFT) of the reactions of the methoxymethyl cation, CH3OCH2+. Rate coefficients and product branching ratios are reported for twenty nine reagent molecules including those that constitute the major ingredients of air, the hydrocarbons CH4, C2H6, C3H8, n-C4H10, C2H2, C2H4, C3H4 (allene and propyne), C6H6, and the S-containing molecules H2S, CH3SH, C2H5SH, (CH3)2SH, and (C2H5)2SH. In addition, we examined the reactions with the N-containing molecules NH3, CH3NH2, (CH3)2NH, (CH3)3N, pyrrole, pyridine as well as CH3COCH3. The results can be summarized under three general reaction types: Reaction at the CH3 carbon, reaction at the CH2 carbon, and association. The results also indicate that the methoxymethyl cation can be used as a chemical ionization source for the detection of trace levels of S-containing compounds in saturated hydrocarbons.     

Synthesis and characterization of six-coordinate "3 + 2" mixed-ligand oxorhenium complexes with the o-diphenylphosphinophenolato ligand and tridentate coligands of different N and S donor atom combinations

A series of octahedral six-coordinate oxorhenium(V) mixed ligand complexes containing the common [ReO(L)]2+ fragment (L = o-OC6H4P(C6H5)2] have been synthesized and characterized. Hence, it was shown that the [ReO(L)]2+ moiety can accommodate a variety of tridentate ligands containing a central amine group amenable to deprotonation and different combinations of lateral groups, such as ethylamine, substituted ethylamine, ethylthiol, and ethylthioether arms. In particular, by reaction of equimolar amounts of the pertinent HLn ligands with the [(n-C4H9)4N][ReOCl3(L)] precursor in refluxing acetonitrile/methanol or dichloromethane/methanol mixtures, the following series of [ReO(Ln)(L)]+/0 oxorhenium(V) complexes has been generated: ReO[[N(CH2CH2NH2)2][o-OC6H4P(C6H5)2]]Cl (1); ReO[[C2H5)2NCH2CH2NCH2CH2S][o-OC6H4P5)2]] (2); ReO[[(CH2)4NCH2CH2NCH2CH2S][o-OC6H4P(C6H4P(C6H5)2]] (3); and ReO[[C2H5SCH2CH2NCH2CH2S][o-OC6H4P(C6H5)2]] (4). The complexes are closed-shell 18-electron oxorhenium species, which adopt octahedral geometries both in solution and in the solid state, as established by conventional physicochemical techniques including multinuclear NMR and single-crystal X-ray diffraction analyses.     

Temperature effect on quenching of CH(AΔ)

The quenching rate constants of CH(A²Δ) radicals by alcohol, alkane, O₂, and C₂H₄ molecules over the temperature range 297–653 K have been measured using laser photolysis of CHBr₃ at 266 nm to produce CH(A) radical and time-resolved fluorescence measurements. Under the simultaneous effects of multiple attractive potentials and repulsive barrier, the temperature dependence of the quenching process of CH(A²Δ) is discussed qualitatively based on a modified collision complex model.     

Quantum dynamics of Renner-Teller and isotopic effects in NH(a1Δ) + D(2S) reactions

A quantum dynamics study for the NH(a(1)Δ) + D((2)S) reactions using coupled channel time dependent real wavepacket formalism is presented. Moreover, the Renner-Teller (RT) interactions between two electronic states of NHD (X[combining tilde](2)A' and ?(2)A') have been taken into account by means of semiempirical RT matrix elements. The introduction of RT effects opens the possibility of studying not only the adiabatic reactions [depletion (d) to N((2)D) + HD(X(1)Σ(+)) and exchange (e) to ND(a(1)Δ) + H((2)S)] but also nonadiabatic ones [quenching (q) to NH(X(3)Σ(-)) + D((2)S) and exchange-quenching (eq) to ND(X(3)Σ(-)) + H((2)S)]. Reaction probabilities, cross sections, isotopic effects, and rate constants are presented for all the before mentioned reactions. RT results are compared with Born-Oppenheimer, quasiclassical, and experimental data. Contrasting with previous NH + H results, we point out interesting RT and isotopic effects, which depend on the D and H masses and on the tunneling of the H atom. In fact, RT effects, near-threshold cross sections, and rate constants are smaller in NH + D than in NH + H, as expected from the masses of the attacking atoms. Our rate constants and quenching branching ratio agree well with previous quasiclassical and experimental data, validating the semiempirical RT coupling we employ. Some small differences between calculated and measured rate constants might be due to the theoretical approximations and to the large experimental error bars.     

Inorganic-organic hybrid vesicles with counterion- and pH-controlled fluorescent properties

Two inorganic-organic hybrid clusters with one or two covalently linked pyrene fluorescent probes, [(n-C(4)H(9))(4)N](2)[V(6)O(13){(OCH(2))(3)C(NH(CO)CH(2)CH(2)CH(2)C(16)H(9))}{(OCH(2))(3)C-(NH(2))}] ((TBA(+))(2)1) and [(n-C(4)H(9))(4)N](2)[V(6)O(13){(OCH(2))(3)C(NH(CO)CH(2)CH(2)CH(2)C(16)H(9))}(2)] ((TBA(+))(2)2), respectively, are synthesized from Lindqvist type polyoxometalates (POMs). The incorporation of pyrene into POMs results in amphiphilic hybrid molecules and simultaneously offers a great opportunity to study the interaction between hybrid clusters and their counterions. 2D-NOESY NMR and fluorescence techniques have been used to study the role of counterions such as tetrabutyl ammonium (TBA) in the vesicle formation of the hybrid clusters. The TBA(+) ions not only screen the electrostatic repulsions between the POM head groups but also are involved in the hydrophobic region of the vesicular structure where they interrupt the formation of pyrene excimers that greatly perturbs the luminescence signal from the vesicle solution. By replacing the TBA(+) counterions with protons, the new vesicles demonstrate interesting pH-dependent fluorescence properties.