首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 203 毫秒
1.
用密度泛函理论(DFT/BLYP)在6-31G基组水平上研究了金属原子-苯与离子-苯配合物的气相电子转移过程,得到了M(Li,Na,Mg)-C6H6和M^+-C6H6络合物以及它们之间电子转移过程的先驱络合物的最优几何构型和电子结构。同时,利用线性坐标确定了过滤态的结构,结果表明:DFT方法计算得到的单体,即原子(离子)-苯的构型,同MP2结果较为一致。先驱络合物具有C6ν对称性,给体与受体间距离  相似文献   

2.
金宏威  封继康 《结构化学》1999,18(6):451-455
用INDO系列方法对由(C59N)2和甲苯合成的衍生物C59(C6H4CH3)N进行了理论研究,得到了分子的稳定构型,表明C59(C6H4CH3)N具有Cs对称性。以优化构型为基础讨论了分子的UV-VIS光谱、NMR谱,结果瑟实验符合得很好。还计算了C59-(C6H4CH3)N的二阶非线性光学系数βμ,结果表明这种分子具有较大的二阶非线性光学系数。  相似文献   

3.
基于半经典电子转移理论,结合量子化学计算,城HF/DZP水平上,研究外电场作用下平行的苯分子-苯正离子自由基体系(C6H4)2^+的分子内电子转移问题。在给体和受体几何构型优化的基础上,用线性反应坐标确定电子转移过渡态,分别用两态变分方法和基于Koopmans定理的分子轨道跃迁能方法计算电子转移矩阵元VAB,讨论了VAB对给体和受体中心距d的指数衰减关系,取中心距为0.6nm,研究了外电场对反应热  相似文献   

4.
用INDO 系列方法对由(C59N)2和甲苯合成的衍生物C59 (C6H4CH3)N进行了理论研究,得到了分子的稳定构型,表明C59(C6H4CH3)N具有Cs对称性。以优化构型为基础讨论了分子的UV-VIS光谱、NMR谱,结果与实验符合得很好。还计算了C59-(C6H4CH3)N的二阶非线性光学系数βμ,结果表明这种分子具有较大的二阶非线性光学系数。  相似文献   

5.
测定了三核苯甲苯酸合物[Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2(OBz^-=苯甲酸根)的电子光谱,应用配体场理论和T-S图求得配体场参数10Dq-12457cm^-1,用CNDO/2方法对其简化模型进行了计算。  相似文献   

6.
CO/H2合成甲醇CuO—ZnO—ZrO2催化剂的研究   总被引:4,自引:0,他引:4  
通过活性测定,XRD、TG-DTA表征,考察了共沉淀法制备的铜锌锆合成甲醇催化剂中ZrO2对物相结构、催化活性及热稳定性的影响。结果表明,ZrO2能显著提高CO/H2合成甲醇的催化活性和热稳定性。催化剂母体、氧化态和还原态的物相并未发生变化,仍分别为:Cu2(OH)3NO3,(Cu,Zn)5(CO3)2(OH)6,(Cu,Zn)2CO3(OH)2,Zn5(CO3)2(OH)6;CuO、ZnO;Cu  相似文献   

7.
用INDO系列方法对由(C59N)2和苯甲醚合成的衍生物C59(C6H4OCH3)N进行了理论研究,得到了分子的稳定构型。结果表明,C59(C6H4OCH3)N具有Cs对称性,以优化构型为基础讨论了分子的UV-Vis光谱、NMR谱线数,结果与实验符合得很好,本文还计算了C59(C6H4OCH3)N的二阶非线性光学系数βμ,结果表明这种物质具有较大的二阶非线性光学系数。  相似文献   

8.
金属硼化物结构与稳定性的理论研究   总被引:1,自引:1,他引:1  
用HF/3-21Gabinitio法对金属硼化物MB2/MB2(M=Li,Na,Be,Mg,Al)的75个电子态结构进行能量梯度法优化,再用大基组二次且上互作用QCISD(T)/6-311G进行单点计算,得到了结构参数总能量,为了考察各原子簇的稳定性,还对24个碎片的70多个电子态,求得相应的QCISD(T)能量,在此基础上计算了原子化能、电离能、离解通道和碎片化能,得到了原子簇的稳定性规律。  相似文献   

9.
用QCISD(T)/6311+G(3df,2p)(简称QCI)计算了BH-(2Π),BF-(2Π),BH(1∑),BeH-(1∑),BeF-(1∑)和BF(1∑)的较完整的势能曲线,探讨了这些体系的稳定性和解离过程.同时用Morse函数和ER函数拟合得到势能曲线,用拟合结果计算谐性频率和非谐性频率,并与已有的实验数据(BH和BF分子)进行比较,由此考察了QCI理论方法在远离平衡构型时的可靠性.对于因单参考态近似导致的反常势能曲线进行了CASSCF计算.还比较了QCI和G2理论中标准的MP2(ful)/631平衡几何构型及其对QCI总能量的影响.  相似文献   

10.
采用键表酉群方法对C6H5F、C6H5OH和C6H5NH2中的电子离域现象进行了计算和分析,讨论了取代苯的价键描述特性,并计算了取代基的π电子离域能.结果表明离子结构成分与离域能有直接关系,即离子成分越多,电子离域能越大./6-31G基组及“分子中的原子”方法将电荷密度分区积分得到各原子上的电荷集居数,并将此结果与取代苯的反应性能进行了比较。为在价键意义上分析和理解取代基对苯环电子结构及其反应性能的影响,本文对3个典型的取代苯Ph-X(X=F,OH,NH2)进行了初步的价键计算和讨论.1计算方法及构型在键表酉群方法中[5],体系的一个共振结构可用一个价键结构函数即键表ψ(k)来描述,相应的体系总波函数Ψ可表示为M个正则键表的线性组合:式(1)便构成了键表相互作用(BTI)计算方法[6]的基础.键表对体系的结构贡献定义为:原子轨道q上的电荷集居数定义为:式中mq(k)可取0、1或2,分别对应于键表ψ(k)中原子轨道q出现0、1或2次.为简比计算,我们将取代苯的σ骨架用HF分子轨道固定[7],这样仅需考虑π电子及轨道.原子轨道积分及HF-SCF计算采用Gaussian80程序.联系人及第一作者:莫亦荣,男,29  相似文献   

11.
Despite of its fundamental importance, the mechanism of the reaction between ozone and dioxins are still lack detailed investigation so far. It is well-known that quantum chemical calculation is a well-established method for investigating chemical reactions. In this article, quantum chemical calculation was employed to investigate the mechanism of the reaction between ozone and dioxins, as exemplified by 2,3,7,8-TCDD. The theoretical study showed that, 2,3,7,8-TCDD was gradually destructed by ozone via six cleavages of the CC bonds. All the six cleavages of the CC bonds were calculated and discussed in detail based on the theoretical calculations by the UB3LYP/6-31G(d) method. At the same time, the energies of stationary points along the reaction process were calculated by the UMP2/6-311g(d,p)//UB3LYP/6-31G(d) method and the activation energy was obtained. The obtained activation energy was 12.25 kcal/mol, which was lower than that of the reaction between benzene and O3(16.64 kcal/mol). This indicated that, by comparison with benzene, 2,3,7,8-TCDD could be more efficiently destructed by O3. The reason for this result was also discussed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

12.
A density functional theory (DFT) study of the reaction of dibenzofuranyl radical with oxygen molecule has been made. The geometries, energies, and vibrational frequencies of the reactant, transition states, intermediates, and products have been calculated at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d) level of theory. The initial reaction of dibenzofuran (DBF) with molecular oxygen results in the formation of the 1-dibenzofuranylperoxy radical. The stability of this adduct toward decomposition at low to intermediate temperatures results in it undergoing several possible rearrangements. The lowest energy pathway with a barrier of 24.2 kcal/mol involves a rearrangement to the 1,1-dioxadibenzofuran radical. The next lowest energy pathway involves fission of the O-O linkage whose reaction energy was found to be 37.6 kcal/mol. Transition state theory (TST) calculations indicate that the lowest energy pathway should predominate at temperatures up to about 1200 K. Two other unimolecular reaction pathways with barriers of 45.5 and 91.1 kcal/mol have also been discovered. The latter pathway leads to the formation of a para-quinone (dibenzofuran quinone) which has been detected experimentally in the low-temperature oxidation of DBF [Marquaire, P. M.; Worner, R.; Rambaud, P.; Baronnet, F. Organohalogen Compd. 1999, 40, 519]. Our quantum calculations, however, do not support this latter pathway to quinone formation. Instead, the quinone is most probably formed as a consequence of recombination of the 1-dibenzofuranyloxy radical (produced by peroxy fission) with an O atom in the para position. Each of the unimolecular reaction pathways have been subjected to detailed quantum chemical investigation and transition states and intermediates leading to the final products (principally CO, CO2, and C2H2 with traces of benzofuran and benzene) have been identified. For certain stable intermediates, their possible reactions with molecular oxygen have been further investigated quantum chemically. The present work therefore presents a detailed quantum chemical investigation of the reaction pathways in the low-temperature oxidation mechanism of DBF. Since the dibenzofuran moiety is present in the polychlorinated DBFs, our conclusions should be generally applicable to this family of compounds.  相似文献   

13.
Collision depopulation cross sections of 13 single, highly vibrationally excited levels with 45,000 cm(-1) energy in the electronic ground state of SO(2) in collision with CO in a supersonic jet have been measured. The measurements for these single highly excited quantum states are conducted through pressure dependence of the decay of the fluorescence quantum beat resulted from their coupling with the rovibronic levels in the optically allowed transitions to the (140), (210), and (132) C(1)B(2) levels. The relaxation cross sections of these highly excited states, each with well-defined energy and symmetry, range from 27 to 187 A(2) with an average of 71 A(2). This average cross section is much larger than the hard sphere cross section of 48 A(2). The relaxation cross section is also found to be larger for the quantum states with a larger matrix element in coupling with the "bright" electronically excited level. Both observations suggest a substantial contribution from long range interactions in collision relaxation of highly excited molecules.  相似文献   

14.
Photoinitiated triplet quantum amplified isomerizations (QAI) of substituted Dewar benzene derivatives in polymeric media are reported. The quantum efficiencies and the ultimate extents of reactant-to-product conversions increase significantly with the incorporation of appropriate co-sensitizers; compounds whose triplet energies are similar to or lower than that of the sensitizer and close to that of the reactant. These co-sensitizers serve to promote chain-propagating energy transfer processes and thereby increase the action sphere of photosensitization. Isomerization quantum yields increase, as predicted, with increasing concentrations of the reactants and the co-sensitizers. Chain amplifications as large as approximately 16 and extents of conversion that approach 100% have been achieved. Mechanistic schemes are proposed to account for the dynamics of the inherent energy transfer processes and provide a predictively useful model for the design of a new class of photoresponsive polymers based on changes in the refractive index of the materials.  相似文献   

15.
Black phosphorus quantum dots (BPQDs), with an average diameter of about 6 nm and a height of about 1.1 nm, are successfully synthesized by means of a pulsed laser ablation (PLA) method in isopropyl ether (IPE) solvent. The photoluminescence PL quantum yield of the as‐prepared sample is as high as 20.7 %, which is 3 times that of BPQDs prepared by means of probe ultrasonic exfoliation (approximately 7.2 %). The stable and blue–violet PL emission of the BPQDs is observed. It can be elucidated that electrons transit from the LUMO energy level to the HOMO energy level, as well as energy levels below the HOMO (H1 and H2). In addition, BPQDs are also utilized in bioimaging in HeLa cells, showing an intense and stable PL signal and excellent biocompatibility. Hence, this work indicates that the obtained BPQDs with high quantum yield and stable PL emission have great potential for biomedical applications, including biolabeling, bioimaging, and drug delivery.  相似文献   

16.
The molecular structure, conformational stability and isomerization of nitroso, nitro substituted benzene and 1,3-cyclopentadiene in gas phase have been investigated using ab initio and density functional theory methods. The molecular geometries and energetics of possible conformers were obtained by employing MP2, B3LYP and B3PW91 levels of theory implementing 6-31G* basis set. The relative stabilities of the conformations were evaluated from the energy differences of the structure. Chemical hardness (η) and chemical potential (μ) were calculated at HF/6-31G* level of theory for all the positional and geometrical isomers to study the maximum hardness principle. Each optimized structure has been tested against the imaginary frequencies at MP2/6-31G* level of theory in order to be sure they are located at energy minimum.  相似文献   

17.
The sulfur mustard, HD, a chemical warfare agent, has been studied by ab initio quantum molecular computations (HF /6-31G * and 6-31G ) on its various forms (neutral, ethylene sulfonium, and free carbonium ions). The geometries of these molecules have been completely optimized and the minimal energy conformations determined with their associated charge distributions. We discuss these results on electrostatic properties with respect to the mechanism of DNA alkylation by HD and compare them with our previous study of the nitrogen mustard mechlorethamine.  相似文献   

18.
如何计算与测量多组元体系的活度系数,是一个重要问题。我们的工作是选取了磷酸三丁酯(TBP)与硫国酰基三氟丙酮(TTA)溶于苯的体系,进行了实验测量与理论计算,理论与实验取得了基本一致的结果。  相似文献   

19.
The silanes C6F5SiF2CH2NMe2 (1), C6F5SiF2N(SiMe3)NMe2 (2) and C6F5SiF2ONMe2 (3) with pentafluorophenyl substituents and geminal N atoms have been prepared by the reaction of C6F5SiF3 with LiCH2NMe2, LiN(SiMe3)NMe2 and LiONMe2, respectively. The compounds have been characterised by spectroscopic methods and crystal structure determination. Comparison of measured and calculated IR spectra has provided insight into the conformational composition of the vapour of . Whereas and show interactions between the geminal Si and N atoms, does not. Further analysis of the bonding situation has been undertaken by quantum chemical calculations of the rotation and bending potentials of the C6F5SiF2-X-NMe2 units.  相似文献   

20.
Fluorescence decay-tune measurements of solid benzene at very low temperature give a value of 83.8 ns which is similar, within experimental error, to the high-pressure value of benzene vapour reported in the literature. The agreement in the fluorescence quantum yield is discussed  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号