The pure rotational Raman spectra of cyanogen, C2N2 and C2N2

The pure rotational Raman spectra of C₂¹⁴N₂ and C₂¹⁵N₂ have been recorded photographically using a 3-metre spectrograph with a reciprocal linear dispersion of 1.4 cm⁻¹ mm⁻¹ at 488.0 nm and analysed to give the rotational and centrifugal distortion constants for both species. Corrections were applied to compensate for the effect of molecules in excited vibrational states on the pure rotational spectra. Comparisons are made with previous infrared vibration—rotational studies on these species and with previous Raman studies on C₂¹⁴N₂. The following bond lengths were calculated: r₀(C---N) = 116 ± 1 pm; r₀(C---C) = 138 ± 2 pm.     

Equilibrium bond lengths, force constants and vibrational frequencies of MnF2, FeF2, CoF2, NiF2, and ZnF2 from least-squares analysis of gas-phase electron diffraction data

The least-squares analysis of the electron diffraction data for MnF₂, FeF₂, CoF₂, NiF₂ and ZnF₂ was carried out in terms of a cubic potential function. The obtained equilibrium bond lengths (in Å) are r_e(Mn–F)=1.797(6), r_e(Fe–F)=1.755(6), r_e(Co–F)=1.738(6), r_e(Ni–F)=1.715(7), and r_e(Zn–F)=1.729(7). The determined force constants and the corresponding vibrational frequencies are listed. The bond length r_e(Cu–F)=1.700(14) Å for CuF₂ was estimated and the variations of bond lengths for the first-row transition metal difluorides were discussed in light of their electronic structure.     

2,4-二硫代尿嘧啶的紫外吸收光谱和共振拉曼光谱

硫代嘧啶碱基是光动力疗法潜在的重要光敏剂,其最低单重激发态的光物理研究已有广泛报道。然而,其较高激发态的跃迁性质和反应动力学研究较为稀少。因此,本文采用共振拉曼光谱和密度泛函理论计算方法研究2,4-二硫代尿嘧啶的紫外光谱和几个较高单重激发态的短时结构动力学。首先,基于共振拉曼光谱强度与电子吸收带振子强度f的关系,将紫外光谱去卷积成四个吸收带,分别为358 nm(f=0.0336)中等强度吸收带(A带),338 nm(f=0.1491)、301 nm(f=0.1795)和278 nm(f=0.3532)强而宽的吸收带(B、C和D带)。这一结果既吻合密度泛函理论计算结果,又符合共振拉曼光谱强度模式对紫外光谱带的预期。据此,去卷积得到的四个吸收带被分别指认为S0→S2跃迁、S0→S6跃迁、S0→S7跃迁和S_0→S_8跃迁。同时,分别对B,C和D带共振拉曼光谱进行了详细的指认,获得了短时动力学信息。结果表明,S_8态短时动力学的显著特征是在Franck-Condon区域或附近发生了S8(ππ~*)/S(nπ~*)势能面交叉引发的、伴随超快结构扭转的非绝热过程。S7和S6态短时动力学的主要特征是反应坐标的多维性,它们分别沿C_5C_6/C_2S_8/C_4S_(10)/N_2C_3+C_4N_3H_9/N_1C_2N_3/C_2N_1C_6/C_6N_1H_7/C_5C_6H_(12)和C_5C_6/N_3C_2/C_4S_(10)/C_2S_8+C_6N_1H_7/C_5C_6H_(12)/C_5C_6N_1/C_5C_6H_(12)/C_2N_1C_6/N_1C_2N_3/C_4N_3H_9/N_1C_2N_3等内坐标演化。     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene

has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_g(S---C₂) = 1.719(2) Å, r_g(C₂=C₃) = 1.370(3) Å, r_g(C₃---C₆) = 1.497(6) Å, r_g(C₂---H) = 1.101(5) Å, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) − r(S---C₅) and r(C₂=C₃) − r(C₄=C₅) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Spectres de rotation de la molécule de chlorobenzène : II. Variétés isotopiques multisubstituées et structure géométrique précise

In order to complete the r_s structure of chlorobenzene given in a preceding paper, a variety of isotopic species of this molecule were synthesized and their microwave spectra studied. This made twenty isotopic species available, enabling the determination of the geometrical parameters by a least squares method. Fitting only differences of moments of inertia either for monosubstituted species or to multiply substituted species gave the same result. They hardly differ from the r_o values and agree with the r_s values obtained by the Kraitchman equations. The resulting error limits were reduced, however.

The following structural parameters were obtained, C₁C₂ = 1.399 Å, C₂C₃ = 1.386 Å, C₃C₄ = 1.3976 Å, C₁Cl = 1.7248 Å, C₂H₂ = 1.080 Å, C₃H₃ = 1.081 Å, C₄H₄ = 1.081 Å, C₆C₁C₂ = 120° 16, C₁C₂C₃ = 119°78, C₂C₃C₄ = 120°24, C₃C₄C₅ = 119°80, C₁C₂H₂ = 119°45, C₂C₃H₃ = 119°76.

The structure of the ring differs significantly from C₆ symmetry. The deformation can be regarded as a compression of the position C₁ while the angle of C₂H₂ bond is also changed.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_{g(S---C2) = 1.719(2) Å}, r_{g(C2=C3) = 1.370(3) Å}, r_{g(C3---C6) = 1.497(6) Å}, r_{g(C2---H) = 1.101(5) Å}, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) - r(S=C₅) and r(C₂=C₃)-r(C₄ =C₅) were fixed at the 3–21G* value of 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

C60O3的结构和电子光谱的理论研究

用INDO系列方法对C₆₀O₃的可能构型进行研究,结果表明:环氧结构邻近的6-6键易发生进一步的加成反应.其中3个氧原子加在同一个六元环的6-6边上,形成环氧结构最稳定的C₃v构型,第3个氧原子加在2个环氧结构相邻的六元环的6-6边上的C₂、C_s构型也相当稳定,C₂、C_s构型的部分¹³C NMR谱与实验吻合.C₆₀O₃可能有较好的反应活性,其电子光谱属于理论预测.     

Ab initio MRSDCI calculations of the g-tensor components of [Cu(H2O)6] complexes

The geometrical structure, electronic states and g-tensor values of the hydrated Cu²⁺ ion, [Cu(H₂O)₆]²⁺ complex, have been studied by means of ab initio MO and MRSDCI methods. The ground state potential energy surface calculated as functions of the axial and equatorial Cu---O bond distances (r_ax and r_eq) show two energy minima which correspond to elongated and compressed structures of the [Cu(H₂O)₆]²⁺ complex. For the elongated structure, the optimized geometry and ratio of the bond lengths (r_ax/r_eq) were in good agreement with the structure determined by ESR and the EXAFS experiments. On the basis of second-order perturbation theory, g-tensor components of the complexes were calculated with the natural orbitals obtained by an MRSDCI calculation. For the elongated structure, the g value is larger than g_τ (g = 2.400 and g_τ = 2.098) which is in agreement with the ESR experiment.     

The effects of fluorine and chlorine substitution on bond lengths in ethanes and disilanes: comparisons of ab initio and experimental information

Ab initio and some density functional theory calculations of bond lengths in fluoro- and chloro-ethanes and disilanes are reported with a precision of ±0.0001 Å under strictly comparable conditions. The resulting changes in MH and MX (M=C, Si; X=F, Cl) bond length are analysed for the effects of halogens substituted in geminal (), or vicinal (gauche or trans) positions. The shortening effect of halogen on an MH bond is markedly reduced or even reversed by the introduction of electron correlation at the MP2 or B3LYP level. MX bonds are little affected. gauche halogen consistently shortens both MH and MX bonds, while trans halogen has no effect on an MH bond but a small and variable effect on the MX bond.

The reality of these calculated changes in bond length is tested in two ways. MH bond lengths are plotted against experimental values of the isolated stretching frequencies ν^isMH, which themselves correlate well with experimental r₀ bond lengths. Agreement on the resulting substituent effects is generally good for the gauche and trans effects of halogen but variable for effects. Unobserved ν^isMH values are predicted from computed bond lengths in fluoroethanes, chloroethanes and chlorodisilanes.

Calculated MX and MM bond lengths are compared with experimental values, notably those from electron diffraction studies amongst the ethanes. Most calculations underestimate the changes found experimentally in CF and CCl bond lengths. CC bond length changes are underestimated in fluoroethanes and overestimated in the chloro-compounds.

The ‘offset’ value (r_e(calc)−r_e(true)) for a CH or SiH bond calculated with a given basis set and level of theory in most cases varies markedly throughout the series of compounds. The same is true for CF, CCl, CC and SiSi bonds if the corresponding offset values for the r_a lengths are constant.

The need is stressed for extended experimental work on many of the compounds, especially the disilanes. It is recommended that structures should be refined with ab initio derived constraints on the bond lengths involved and differences between spectroscopic and diffraction-based geometries reconciled through the calculation of r_z structures.     

氯化铅纳米线的胶束模板诱导合成及其机理研究

一维纳米材料由于在光学、磁学、微电子学等领域中具有广阔的应用前景而引起了科技工作者的广泛兴趣 .目前 ,研究得最多的一维纳米材料为碳纳米管 [1,2 ] ,它的某些性质已得到实际应用 .而纳米线 (纳米丝、纳米纤维 )的研究尚处于初始阶段 ,至今已合成或制备出的纳米线只有硫化钼、硫化镉、氮化镓、砷化铟、硫酸钙、碳酸钡、碳化硼、锡 -铅、金、银、铋等十余种 [3～ 16 ] ,尚未见有氯化铅纳米线的报道 .氯化铅晶体通常呈九配位三帽三方柱层状结构 ,具有方向上的电性差异 .当进入纳米尺寸时 ,可能产生奇异的理化现象 .本文用反相胶团或 W/ …     

Pyrolysis mechanism of carbon matrix precursor cyclohexane(III)—pyrolysis process of intermediate 1-hexene

The pyrolysis mechanism of important intermediate 1-hexene of carbon matrix precursor cyclohexane was studied theoretically. Possible reaction paths were designed based on the potential surface scan and electron structure of the initial C–C bond breaking reactions. Thermodynamic and kinetic parameters of the possible reaction paths were computed by UB3LYP/6-31+G* at different temperature ranges. The results show that 1-hexene pyrolyzes at 873 K. When below 1273 K, the major reaction paths are those that produce C₃H₄, and above 1273 K, the major reaction paths are those that produce C₃H₃ from the viewpoint of thermodynamics. From the viewpoint of kinetics, the major product is C₃H₃, it results from the pyrolysis reaction of 1-hexene cracking bond C₃–C₄ and generating C₃H₅ and C₃H₇ with the activation energy ΔE₀^≠θ=296.32 kJ/mol. Kinetic results also show that product C₃H₄ accompany simultaneously, which is the side reaction starting from the pyrolysis of 1-hexene forming C₄H₇ and C₂H₅ with the activation energy of 356.73 kJ/mol. When reaching 1473 K, the rate constant of the rate-determining steps of these two reaction paths do not show much difference, which means both the reaction paths exist in the pyrolysis process at the high temperature. The above results are basically in accordance with mass spectrum analysis and far more specific.     

Molecular structure of 4,4′-sulfandiyl-bis-thiophenol from electron diffraction

The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C₁₂H₁₀S₃) has been determined by gas electron diffraction. Assuming identical geometry and D_2h local symmetry for ---SC₆H₄S--- moieties, the following bond lengths (r_g) and bond angles were obtained: C---H = 1.101 ± 0.005, S---H = 1.388 ± 0.019, (C---C)_mean = 1.400 ± 0.003, (S---C)_mean = 1.778 ± 0.004 Å, C_ar---S---C_ar = 103.5 ± 1.3, C---C(S)---C = 120.4 ± 0.3, C(H)---C(H)---H = 119.1 ± 0.9 and C---S---H = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C_arSC_ar plane; ₁ = 67.8 ± 2.0°, ₂ = 4.5 ± 7.2°, and ₁ = 69.4 ± 2.0δ, ₂ = −26.6 ± 7.1°. Identical signs of ₁ and ₂ indicate that the two benzene rings are rotated in the same direction about the respective S_central---C axes.     

Molecular structure of acetyl cyanide as studied by gas electron diffraction

The structure of acetyl cyanide has been determined by making joint use of the electron diffraction intensities measured in the present study and the rotational constants reported by Krisher and Wilson. The thermal average bond distances are: r_g(C-H) = 1.116±0.011 Å, r_g(CN) = 1.167±0.010 Å, r_g(C=O) = 1.208±0.009 Å, r_g(=C-C) = 1.477±0.008 Å and r_g(C-C_methyl) = 1.518±0.009 Å. The bond angles in the zero-point average structure (r_av) are: (C_methyl-C=O) = 124.6±0.7°, (C-C-C) = 114.2±0.9°, (C-CN) = 179.2±2.2° and (H-C-H) = 109.2±0.7°. The uncertainties represent the estimated limits of experimental error. The C-C single bond placed between the double and triple bonds is longer than those in vinylacetylene, acrylonitrile and propynal. Other structural parameters are also compared with those in related molecules. The infrared and Raman spectra of this molecule have been measured, and Urey-Bradley force constants have been determined.     

Semiempirical molecular dynamics studies of C60/C70 fullerene oxides: C60O, C60O2 and C70O

The spectral analysis indicates that all isomers of C₆₀O, C₇₀O and C₆₀O₂ have an epoxide-like structure (an oxygen atom bridging across a C–C bond). According to the geometrical structure analysis, there are two isomers of fullerene monoxide C₆₀O (the 5,6 bond and the 6,6 bond), eight isomers of fullerene monoxide C₇₀O and eight isomers of fullerene dioxide C₆₀O₂. In order to simulate the real reaction conditions at 300 K, the calculation of the different isomers of C₆₀O, C₆₀O₂ and C₇₀O fullerene oxides was carried out using the semiempirical molecular dynamics method with two different approaches: (a) consideration of the geometries and thermodynamic stabilities, and (b) consideration of the ozonolysis mechanism. According to the semiempirical molecular dynamic calculation analysis, the probable product of this ozonolysis reaction is C₆₀O with oxygen bridging over the 6–6 bond (C_2v). The most probable product in this reaction contains oxygen bridging across in the upper part of C₇₀ (6–6 bond in C₇₀O-2 or C₇₀O-4) an epoxide-like structure. C₆₀O₂-1, C₆₀O₂-3 and C₆₀O₂-5 are the most probable products for the fullerene dioxides. All of these reaction products are consistent with the experimental results. It is confirmed that the calculation results with the semiempirical molecular dynamics method are close to the experimental work. The semiempirical molecular dynamics method can offer both the reaction temperature effect by molecular dynamics and electronic structure, dipole moment by quantum chemistry calculation.     

Crystal structure of the 1/ 1 molecular complex of 5,5′,12,12′-bis(triseleno)bis(naphthacene-6,11-quinone) with benzonitrile, (C18H8Se3O2)2(C6H5CN)

The structure of the (C₁₈H₈Se₃O₂)₂(C₆H₅CN) molecular complex isolated from the TSeT + HgI₂ reaction in benzonitrile has been determined. The -Se-Se-Se- fragment has been found to have Se---Se bond lengths equal to 2.348(3) and 2.350(4) Å.     

Microwave spectrum and rotational isomers of ethyl fluoroformate

The microwave spectrum of ethyl fluoroformate displays strong a-type R branch transitions from two rotameric forms. One species (extended form) has rotational constants A₀ = 9191.3(9) MHz, B₀ = 2112.61(1) MHz, C₀ = 1756.73(1) MHz which are consistent with a syn-anti (τ₁(OCOC) = 0°, r₂(cocc) = 180°) planar heavy atom structure. The second species (compact form) has rotational constants A₀ = 7760(3) MHz, B₀ = 2388.38(4) MHz, C₀ = 2102.47(3) MHz which are consistent with a syn-gauche (τ₁(ococ) = 0°, τ₂(cocc) ˜ 90°) structure. The two conformational forms have approximately equal energy (0 ± 40 cm⁻¹). Four vibrational satellites of the extended species have been analyzed yielding a torsional frequency around the O-ethyl bond of 70(10) cm⁻¹. Three vibrational satellites attributed to the O-ethyl torsion of the compact species have been analyzed yielding a vibrational frequency of 90(10) cm⁻¹. Approximate Fourier coefficients of a three term potential function for internal rotation about the O-ethyl bond have been determined. Vibrational satellites attributed to the first excited states of the O-ester torsion have been analyzed for both conformers. The torsional vibrational frequency around the O-ester bond is 110(15) cm⁻¹ for the extended conformers and 120(20) cm⁻¹ for the compact.     

多环芳烃与不饱和自由基氢提取反应类的动力学研究

对2~6个环的多环芳烃的氢提取反应类进行了系统研究, 提取氢原子的不饱和自由基包括丙炔基自由基（C₃H₃）、 烯丙基自由基（C₃H₅）、 丁二烯基自由基（nC₄H₅, iC₄H₅）、 环戊二烯基自由基（C₅H₅）以及苯基自由基（C₆H₅）. 采用M06-2X/cc-pVTZ方法得到了多环芳烃的电子结构信息, 利用过渡态理论并结合Eckart隧道校正, 计算了所有反应在500~2500 K范围内的反应速率常数.考察了多环芳烃的大小、 结构对反应速率常数的影响, 对比了不同氢提取自由基及不同氢提取反应类型的速率常数. 结果表明, 多环芳烃的大小对反应速率常数影响不大, 但是多环芳烃的环结构对反应速率常数影响较大. 将不同的氢提取反应类简化为发生在五元环上的C₅类和发生在六元环上的C₆类两类, 结果表明, C₆类的反应活性高于C₅类. 研究了nC₄H₅, iC₄H₅以及C₆H₅自由基与多环芳烃的氢提取反应, 它们的氢提取反应活性大小顺序为C₆H₅>nC₄H₅>iC₄H₅. 通过对每类典型反应的速率常数取平均值, 总结出相应类型的速率规则, 可用于构建多环芳烃和碳烟机理.     

Electronic structure and bonding in Si70

We report a detailed AM1 investigation of the geometrical and electronic structure of Si₇₀. For this purpose, bond lengths, bond orders, charges and molecular energy levels are widely analyzed, and compared with previous theoretical and experimental data on Si₆₀ and homologous carbon clusters C₇₀ and C₆₀. The predicted D_5h structure of Si₇₀ is less delocalized than that of C₇₀. Furthermore, Si₇₀ presents the lowest ionization potential (7.63eV), the highest electron affinity (3.61 eV) and the smallest HOMO-LUMO gap (4.02eV) of the four studied clusters.     

新型双苯并环己酮芳亚胺镍(Ⅱ)催化降冰片烯与甲基丙烯酸丁酯共聚合

采用自制的新型双苯并环己酮芳亚胺镍催化剂双苯并环己酮-2,6-二甲基苯亚胺镍(Ⅱ)(Ni{C₁₀H₈(O)C[2,6-C₆H₃(CH₃)₂N]CH₃}₂, C1)和双苯并环己酮-2,6-二氯苯亚胺镍(Ⅱ)(Ni{C₁₀H₈(O)C[2,6-C₆H₃Cl₂N]CH₃}₂, C2)与三五氟苯硼[B(C₆F₅)₃]结合, 在一定的反应条件下可高效催化降冰片烯(NB)与甲基丙烯酸正丁酯(n-BMA)的乙烯基加成共聚合. 提出了催化聚合时存在的可能失活机理; 研究了不同单体投料比对催化活性、 产率及产物性能的影响. 根据Kelen-Tüdõs方法分别估算出2种单体在不同催化体系下的竞聚率, 即当催化体系为C1/B(C₆F₅)₃时, 竞聚率r_n-BMA=0.02, r_NB=16.28, r_NB·r_n-BMA=0.32; 当催化体系为C2/B(C₆F₅)₃时, r_n-BMA=0.01, r_NB=64.83, r_NB·r_n-BMA=0.65. 结果表明, 2种单体在2种体系催化下均为无规共聚合.     

The molecular structure of benzene sulphonyl chloride

An electron diffraction structure analysis was carried out on benzene sulphonyl chloride, C₆H₅SO₂Cl, utilizing data from concurrent vibrational spectroscopie calculations. The following bond lengths (r_a parameters): C-H 1.14 ± 0.03 Å, C-C 1.403 ± 0.010 Å, S-O 1.417 ± 0.012 Å, C-S 1.764 ± 0.009 Å and S-Cl 2.047 ± 0.008 Å and bond angles (r parameters): C-S-C1 100.9 ± 2.0°, C-S-O 110.0 ± 2.5°, O-S-O 122.5 ± 3.6° and O-S-Cl 105.5 ± 1.8° were determined for an asymmetric model in which the benzene ring is rotated by 75.3 ± 5.0° relative to the plane containing the sulphur-chlorine bond and bisecting the O-S-O angle. The experimental data could equally well be approximated by a symmetric model with the benzene ring perpendicular to the reference plane described previously, if a particularly large amplitude of vibration was associated with the shortest rotation-dependent carbon-chlorine distance. The bond configuration around the sulphur atom in benzene sulphonyl chloride is consistent with the structural variations observed for a series of sulphone molecules.