Geometric shielding corrections for calculation of electron scattering by CO2, C2H2, CHCl3, CH2Cl2, CH3Cl,CHF3, CH2F2 and CH3F at 30–5000 eV

Taking into account the changes of the geometric shielding effect in a molecule as the incident electron energy varies, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using the new additivity rule, the total cross sections of electron scattering by CO₂, C₂H₂, CHCl₃, CH₂Cl₂, CH₃Cl, CHF₃, CH₂F₂ and CH₃F are calculated at the Hartree–Fork level at 30–5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, especially above 100 eV.     

第一过渡系金属离子和CH,CH2,CH3配合物的从头算研究

利用从头算方法 ,以赝势基组 (LANL2DZ)研究了第一过渡系金属离子M (Sc 到Zn )和CH ,CH2 ,CH3 的配合物的构型和成键特征 .MCH 和MCH 2 分别为线型和共平面构型 ,并带有明显的叁键或双键特征 ,但这些多重键多是“不完整”的 .计算所得的CM ,CM ,CM 键解离能 ,多数与实验值接近 ,且从Sc到Zn均表现出类似的周期性变化趋势     

Capture and dissociation in the complex-forming CH + H2 → CH2 + H, CH + H2 reactions

The rate coefficients for the capture process CH + H(2)→ CH(3) and the reactions CH + H(2)→ CH(2) + H (abstraction), CH + H(2) (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH(3) collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems.     

Synthesis and Characterization of （CH3CH2CH2CH2NH3）2SnBr6

1 INTRODUCTION Recently, the researches on inorganic-organic hy-brid compounds represent an advanced field in mate-rial science[1]. At the molecular level, the combina-tion of two extremely different components providesan avenue to design new hybrid materials as well asthe ability to modulate properties of one or more ofthe components[2～6]. Some attractive properties, suchas efficient luminescence[2～4], ideal thermal and me-chanical stability, interesting magnetic[5], non-linearoptical[…     

反常蓝移单电子锂键Y…Li-CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]体系的结构与性质

在密度泛函理论B3LYP/6-311++G(d,p)及MP2/6-311++G(d,p)水平上研究了单电子锂键复合物Y…Li—CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]的结构与性质. 结果表明, 三种单电子锂键复合物H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III)和(H3C)3C…Li—CH3(IV)单电子锂键强度依II(-26.7 kJ·mol-1)相似文献   

连续二氧化碳激光敏化氧化CF2HCL,CF2=CF2,CF2=CFCl,CHCl3,CHCl=CCl2和CH2=CH2

本文报道了连续二氧化碳激光敏化氧化CF_2HCl,CF_2==CF_2,CF_2==CFCL,CHCl_3,CHCl==CCl_2和CH_2==CH_2的反应,讨论了某些反应的机制。结果表明,激光敏化方法可以使不能直接吸收激光的反应物分子在气相中发生反应,并有可能产生卡宾。     

The distonic ion ·CH2CH2CH+OH,keto ion CH3CH2CH=O +·, enol ion CH3CH=CHOH+·, and related C3H6O+· radical cations. Stabilities and isomerization proclivities studied by dissociation and neutralization-reionization

Metastable ion decompositions, collision-activated dissociation (CAD), and neutralization-reionization mass spectrometry are utilized to study the unimolecular chemistry of distonic ion ^·CH₂CH₂CH^?OH (2^+·) and its enol-keto tautomers CH₃CH=CHOH^?· (1 ^+·) and CH₃CH₂CH=O ^+· (3^+·). The major fragmentation of metastable 1^+·–3^+· is H^· loss to yield the propanoyl cation, CH₃CH₂C≡O⁺. This reaction remains dominant upon collisional activation, although now some isomeric CH₂=CH-CH⁺ OH is coproduced from all three precursors. The CAD and neutralization-reionization (⁺NR⁺) spectra of keto ion 3 ^+· are substantially different from those of tautomers 2^+· and 1^+·. Hence, 3^+· without sufficient energy for decomposition (i. e. , “stable” 3^+·) does not isomerize to the ther-modynamically more stable ions 2^+· or 1^+·, and the 1,4-H rearrangement H-CH₂CH₂CH=O^+·(3 ^+·) → CH₂CH₂CH⁺ O-H (2 ^+·) must require an appreciable critical energy. Although the fragment ion abundances in the ⁺ NR ⁺ (and CAD) spectra of 1 ^+· and 2 ^+· are similar, the relative and absolute intensities of the survivor ions (recovered C₃H₆O^+· ions in the ⁺NR⁺ spectra) are markedly distinct and independent of the internal energy of 1 ^+· and 2 ^+·. Furthermore, 1 ^+· and 2 ^+· show different MI spectra. Based on these data, distonic ion 2 ^+· does not spontaneously rearrange to enol ion 1 ^+· (which is the most stable C₃H₆O^+· of CCCO connectivity) and, therefore, is separated from it by an appreciable barrier. In contrast, the molecular ions of cyclopropanol (4 ^+·) and allyl alcohol (5 ^+·) isomerize readily to 2 ^+·, via ring opening and 1,2-H^? shift, respectively. The sample found to generate the purest 2 ^+· is α-hydroxy-γ-butyrolactone. Several other precursors that would yield 2 ^+· by a least-motion reaction cogenerate detectable quantities of enol ion 1 ^+·, or the enol ion of acetone (CH₂=C(CH₃)OH^+·, 6 ^+·), or methyl vinyl ether ion (CH₃OCH=CH ₂ ^+· , 7 ^+·). Ion 6 ^+· is coproduced from samples that contain the —CH₂—CH(OH)—CH₂— substructure, whereas 7 ^+· is coproduced from compounds with methoxy substituents. Compared to CAD, metastable ion characteristics combined with neutralization-reionization allow for a superior differentiation of the ions studied.     

A photoionization study of the ion-neutral complexes CH3CH +CH 3 · CH2CH3] and CH3CH2CH+CH 3 · CH3 in the gas phase: Formation,H-transfer and C—C bond formation between partners,and channeling of energy into dissociation

Photoionization mass spectrometry was used to investigate the dynamics of ion-neutral complex-mediated dissociations of the n-pentane ion (1). Reinterpretation of previous data demonstrates that a fraction of ions 1 isomerizes to the 2-methylbutane ion (2) through the complex CH₃CH⁺CH ₃ ^· CH₂CH₃ (3), but not through CH₃CH⁺CH₂CH ₃ ^· CH₃ (4). The appearance energy for C₃Hin ₇ ⁺ formation from 1 is 66 kJ mol^?1 below that expected for the formation of n-C₃H ₇ ⁺ and just above that expected for formation of i-C₃H ₇ ⁺ . This demonstrates that the H shift that isomerizes C₃H ₇ ⁺ is synchronized with bond cleavage at the threshold for dissociation to that product. It is suggested that ions that contain n-alkyl chains generally dissociate directly to more stable rearranged carbenium ions. Ethane elimination from 3 is estimated to be about seven times more frequent than is C-C bond formation between the partners in that complex to form 2, which demonstrates a substantial preference in 3 for H abstraction over C-C bond formation. In 1 → CH₃CH⁺CH₂CH₃ + CH₃ by direct cleavage of the C1–C2 bond, the fragments part rapidly enough to prevent any reaction between them. However, 1 → 2 → 4 → C4H ₈ ⁺ + CH₄ occurs in this same energy range. Thus some of the potential energy made available by the isomerization of n-C₄H₉ in 1 is specifically channeled into the coordinate for dissociation. In contrast, analogous formation of 3 by 1 → 3 is predominantly followed by reaction between the electrostatically bound partners.     

Syntheses and Characterizations of （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 and （NH3CH2CH2NH3）2Bi2I10

The title compounds have been respectively synthesized by solution process and solvothermal reaction, and their crystal structures were determined by X-ray diffraction method. For （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 1, it crystallizes in tficlinic, space group P1^- with Mr = 2049.76, a = 8.5719（1）, b = 11.7461（3）, c = 15.700（1）A, V = 1451.4（1）A^3, Z = 1, Dc = 2.345 g/cm^3, F（000） = 924, μ（MoKα） = 8.907 mm^-1, T = 293（2） K, the final R = 0.0655 and wR = 0.0804 for 2399 observed reflections with I 〉 2σ（I）. For （NH3CH2CH2NH3）2Bi2I10 2, it crystallizes in monoclinic, space group P21/n with Mr= 1811.20, a = 8.434（4）, b = 13.862（6）, c = 13.362（6）A, V = 1499.9（12）A^3, Z = 2, Dc = 4.010 g/cm^3, F（000） = 1536,μ（MoKα） = 22.007 mm^-1, T = 293（2） K, the final R = 0.0584 and wR = 0.1451 for 1798 observed reflections with I 〉 2σ（I）. The structures of 1 and 2 contain halobismuthate monomer and dimers, respectively. It is noteworthy that the dimers and their organic counters in 2 connect each other by N…I hydrogen bonds to form a layered structure, and the electrostatic interactions and crystal packing forces between layers give rise to the packing of the crystal. The optical absorption spectra of 1 and 2 reveal the appearance of sharp optical gaps of 2.13 and 2.01 eV, respectively.     

Theoretical unimolecular kinetics for CH4 + M ⇄ CH3 + H + M in eight baths, M = He, Ne, Ar, Kr, H2, N2, CO, and CH4

Ensembles of classical trajectories are used to study collisional energy transfer in highly vibrationally excited CH(4) for eight bath gases. Several simplifying assumptions for the CH(4) + M interaction potential energy surface are tested against full dimensional direct dynamics trajectory calculations for M = He, Ne, and H(2). The calculated energy transfer averages are confirmed to be sensitive to the shape of the repulsive wall of the intermolecular potential, with an exponential repulsive wall required for quantitative predictions. For the diatomic baths, the usual "separable pairwise" approximation for the interaction potential is unable to describe the orientation dependence of the interaction potential accurately, and the ambiguity in the resulting parametrizations contributes an additional uncertainty to the predicted energy transfer averages of 20-40%. On the other hand, the energy transfer averages are shown to be insensitive to the level of theory used to describe the intramolecular CH(4) potential, with a computationally efficient semiempirical tight binding potential for hydrocarbons performing equally well as an MP2 potential. The relative collisional energy transfer efficiencies of the eight bath gases are discussed and shown to be a function of temperature. The ensemble-averaged energy transferred in deactivating collisions <ΔE(d)> for each bath is used to parametrize a single-exponential-down model for collisional energy transfer in master equation calculations. The predicted decomposition rate coefficients for CH(4) agree well with available experimental rate coefficients for M = He, Ar, Kr, and CH(4). The effect of vibrational anharmonicity on the predicted rate coefficients is considered briefly.     

[ZnN(CH2CH2NH2)2(CH2CH2N=CHC6H4O)]·Pic的合成与晶体结构

在不加任何碱的条件下,三[2-(亚水杨基胺)乙基]胺与苦味酸锌[Zn(Pic)26H2O]在乙醇中反应,得到了较为少见的多胺单缩合西夫碱配体的配合物[ZnN(CH2CH2NH2)2(CH2CH2N=CH-C6H4O)]Pic。化学式为C19H23N7O8Zn,Mr=542.81,晶体属三斜晶系,空间群为P,晶胞参数为a=0.7494(3),b=1.1917(5),c=1.3142(6)nm,a=78.111(7),b=79.093(7),g=78.577(7),V=1.1121(8)nm3,Dc=1.621g/cm3,m(MoKa)=1.167mm-1,Z=2,F(000)=560,在1.602s(I)的可观测点为2433个,最终偏离因子R=0.0555,wR=0.1139。配合物中Zn(II)与配体的4个N原子和1个O原子配位形成变形的三角双锥结构,桥头N和O为锥顶,4个配位N中桥头N与金属离子的配位作用最弱。晶体通过p-p堆积和分子内、分子间的氢键作用形成二维层状超分子结构。     

(CH2)2O, (CH2)2S与双卤分子间卤键的理论研究

运用量子化学密度泛函B3LYP方法, 采用6-311＋＋G(d,p)及aug-cc-pVDZ基组, 通过CP校正的几何梯度优化对(CH2)2O和(CH2)2S与双卤分子XY (XY＝Cl2, Br2, ClF, BrF, BrCl)形成的卤键复合物的几何构型、振动频率和相互作用能等进行了研究. 利用电子密度拓扑分析理论方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, (CH2)2O和(CH2)2S与双卤分子间的卤键介于共价键与离子键之间, 偏于静电作用成分为主. 形成卤键后, 双卤分子的键长增加, 振动频率减小, 原子积分性质发生改变. 卤键键长的变化、键能的强弱、键鞍点处的电子密度值与双卤分子的电负性有关.     

Intramolecular Rearrangements of >Si(O–C·=O)(CH2–CH3) and >Si(CH2–CH·–CH3)(CH2–CH3) Radicals

Using ESR and IR spectroscopy, the structures of >Si(O–C^·=O)(CH₂–CH₃) (1) and >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) (2) radicals were deciphered. The directions and kinetic parameters of reactions of intramolecular rearrangements in these radicals were determined. The reactions of hydrogen atom abstraction in radical (1) from the CH₂ and CH₃ groups were studied. It was found that the endothermic reaction of hydrogen atom abstraction from the methyl group occurs at a higher rate than the exothermic reaction with the methylene group. The differences are determined by changes in the size of a cyclic transition state. Based on the experimental data, the strengths of separate C–H bonds in surface fragments are compared. The rearrangement >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) >Si(C^·(CH₃)₂)(CH₂–CH₃) was discovered and its mechanism was determined. One of its steps is the skeletal isomerization Si- (2)- _. (1)Si- (1)- _. (2). Experimental data are analyzed using the results of quantum-chemical calculations of model systems.     

Ab initio study of Eu3+–L (L=H2O,H2S,NH2CH3, S(CH3)2, imidazole) complexes

The ground states and binding energies of Eu³⁺–L (L=H₂O,H₂S,NH₂CH₃,S(CH₃)₂, imidazole) complexes has been determined using ab initio techniques. The binding is mostly electrostatic as expected. The empty f orbital is different for the S compounds, being a π-like orbital, while for the O and N containing ligands it is a σ-like orbital. However, the range in the binding energies for the different f holes is small.     

Torsional potentials and conformational structures in the halogen substituted molecules HOCCH2X,HOCCHX2, XOCCH2X,XOCCHX2, XH2CCOCH3, X2HCCOCH3, (XH2C)2CO, (X2HC)2CO,and (X3C)2CO (X = Cl,Br) as determined by molecular-mechanics calculations

Parameter values of the non-blonded atom⋯atom interaction Br⋯OC have been established from gas-phase data. Conformational energies, structures, torsional barrier heights and torsional force constants of the title compounds have been estimated. For BrOCCH₂Br, (Cl₃C)₂CO and (ClH₂C)₂CO the calculated results are compared with gas-phase observations. It is suggested that hexachloroacetone ought to be reinvestigated by electron diffraction.     

Synthesis,Molecular Structure,and Thermal Properties of the Supramolecular Complex [Zn{NH(CH2)4O}{S2CN(C2H5)2}2]2 · CH2N(CH2)4O}2

The supramolecular complex [Zn{NH(CH₂)₄O}{S₂CN(C₂H₅)₂}₂]₂ · CH₂N(CH₂)₄O}₂ (I) has been synthesized and studied by X-ray crystallography and thermal analysis. The noncentrosymmetric complex is composed of two structurally nonequivalent molecules of the adduct of bis(diethyldithiocarbamato)zinc with morpholine, which are linked with the outer-sphere N,N’-dimorpholinomethane molecule through two hydrogen bonds N-H?O. The major differences between the adduct molecules are related to the strength of Zn-N bonds, spatial orientation of the coordinated morpholine heterocyclic rings, and the proportion between the contributions of the trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) components to the geometry of zinc polyhedra. Calculations show that the geometry of the zinc polyhedra is almost halfway between TBP and TP. The thermal destruction of supramolecular compound I is accompanied by desorption of the outer-sphere and coordinated organic molecules. At the final stage, defragmentation of the “dithiocarbamate part” of the complex leads to the formation of ZnS.