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1.
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.  相似文献   

2.
Rate coefficients, k, for the gas-phase reactions of Cl atoms and NO(3) radicals with 2,3,3,3-tetrafluoropropene, CF(3)CF═CH(2) (HFO-1234yf), and 1,2,3,3,3-pentafluoropropene, (Z)-CF(3)CF═CHF (HFO-1225ye), are reported. Cl-atom rate coefficients were measured in the fall-off region as a function of temperature (220-380 K) and pressure (50-630 Torr; N(2), O(2), and synthetic air) using a relative rate method. The measured rate coefficients are well represented by the fall-off parameters k(0)(T) = 6.5 × 10(-28) (T/300)(-6.9) cm(6) molecule(-2) s(-1) and k(∞)(T) = 7.7 × 10(-11) (T/300)(-0.65) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and k(0)(T) = 3 × 10(-27) (T/300)(-6.5) cm(6) molecule(-2) s(-1) and k(∞)(T) = 4.15 × 10(-11) (T/300)(-0.5) cm(3) molecule(-1) s(-1) for (Z)-CF(3)C═CHF with F(c) = 0.6. Reaction product yields were measured in the presence of O(2) to be (98 ± 7)% for CF(3)C(O)F and (61 ± 4)% for HC(O)Cl in the CF(3)CF═CH(2) reaction and (108 ± 8)% for CF(3)C(O)F and (112 ± 8)% for HC(O)F in the (Z)-CF(3)CF═CHF reaction, where the quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. NO(3) reaction rate coefficients were determined using absolute and relative rate methods. Absolute measurements yielded upper limits for both reactions between 233 and 353 K, while the relative rate measurements yielded k(3)(295 K) = (2.6 ± 0.25) × 10(-17) cm(3) molecule(-1) s(-1) and k(4)(295 K) = (4.2 ± 0.5) × 10(-18) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF, respectively. The Cl-atom reaction with CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF leads to decreases in their atmospheric lifetimes and global warming potentials and formation of a chlorine-containing product, HC(O)Cl, for CF(3)CF═CH(2). The NO(3) reaction has been shown to have a negligible impact on the atmospheric lifetimes of CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF. The energetics for the reaction of Cl, NO(3), and OH with CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF in the presence of O(2) were investigated using density functional theory (DFT).  相似文献   

3.
4.
5.
The chlorination of singly and multiply charged C60 cations has been investigated with the selected-ion flow tube technique. Observations are reported for the reactions of C60·+, C602+ and C60·3+ with Cl2, CCl4, CDCl3, CH2Cl2 and CH3Cl at room temperature (295 ± 2 K) in helium at a total pressure of 0.35 ± 0.02 Torr. C60·+ and C602+ were observed not to chlorinate, or react in any other way, with these five molecules. Chlorine also did not react with C60·3+, but bimolecular chloride transfer and electron transfer reactions, reactions that result in charge reduction/charge separation, were observed to occur with CCl4, CDCl3, CH2Cl2 and CH3Cl. Chloride transfer was the predominant channel seen with CCl4, CDCl3 and CH2Cl2 while electron transfer dominates the reaction with CH3Cl. These results are consistent with trends in chloride affinity and ionization energy. The reluctant chlorination of the first two charge states of C60 is attributed to the energy required to distort the carbon cage upon bond formation, while the observed chloride transfer to C60·3+ is attributed to the greater electrostatic interactions with this ion.  相似文献   

6.
本文用自洽场组态相互作用方法(SCF-CI)精确计算了次氯酸分子HOCl的振动激发态的能级以及次氯酸分子中的H和Cl分别被D和^3^7Cl取代后的HO^3^7Cl,DO^3^5Cl和DO^3^7Cl的同位素效应, 这些理论计算值与已有的实验结果吻合较好, 还预测了一些尚未观测到的谱线频率及同位素效应。  相似文献   

7.
Quaternary reciprocal systems of alkali metal fluorides, chlorides, and bromides were partitioned into simplexes by a geometric method and a graph method. Phase transformations and chemical reactions in the bordering ternary reciprocal systems were described. Conversion lines were experimentally studied, and information on crystallizing phases within the composition prisms of the M1,M2‖F,Cl,Br systems (M1 and M2 are group 1 s-block elements) was obtained.  相似文献   

8.
For the d(0) complex [{Zr(CpSiMe(2)H)Cl(3)}(2)] which contains a linear Si-H···Zr interaction across the dimer, DFT calculations are in good agreement with X-ray structures. The BP86 functional shows a slightly stronger interaction than B3LYP but for qualitative purposes either functional is sufficient. QTAIM analysis shows a bond critical point (bcp) for the interaction, a small negative value for the total energy density [H((r))] and the H atomic basin decreases in energy, E(H), and atomic volume compared to the free ligand. NBO analysis showed E(2) for Si-H σ to Zr(dz(2)) donation at 42.8 kcal mol(-1) and a 34% spatial overlap for the interaction consistent with an inverse hydrogen bond. The Wiberg bond index for the interaction is 0.1735 (0.7205 for the Si-H bond), ν((Si-H)) and (1)J((Si-H)) at 2060 cm(-1) and 145.4 Hz compared to 2183 cm(-1) and 172.1 Hz in the free ligand. Using a "synthesis by computation" approach to forming like complexes, similar features were found for [{Hf(CpSiMe(2)H)Cl(3)}(2)]. The titanium complex [{Ti(CpSiMe(2)H)Cl(3)}(2)] does not contain any Si-H···Ti interaction as rotation about the C-Si bond of the ligand occurs to place the Si-H bond hydrogen closer to a terminal chloro ligand across the dimer. An increase in electron density on the metal in the d(2) complex [{Mo(CpSiMe(2)H)Cl(3)}(2)] results in a stronger interaction with a distinct QTAIM analysis bcp [ρ((r)) 0.0448 a.u.], a small negative value for H((r)) and a much reduced H atomic volume. NBO analysis shows E(2) for Si-H σ to Mo(dz(2)) donation at 143.1 kcal mol(-1) and a 29% spatial overlap. Mo(dz(2)) to Si-H σ* donation (back donation) is minimal [E(2) 1.3 kcal mol(-1), ~1% spatial overlap]. The Wiberg bond index is 0.3114 (0.5667 for the Si-H bond), ν((Si-H)) 2015 cm(-1) and (1)J((Si-H)) 120.6 Hz.  相似文献   

9.
《Fluid Phase Equilibria》1999,154(2):261-284
Comprehensive phase diagrams of methanol/CHF3 and methanol/H2O/CHF3 mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO2 for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF3 and methanol/H2O/CHF3 was compared to that of methanol/CO2 and methanol/H2O/CHF3. Fluoroform is markedly more miscible with methanol or methanol/H2O than is CO2. Data for methanol/CHF3 binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.  相似文献   

10.
The geometries of the ClNH3, ClH2O, FNH3 and FH2O clusters are optimized using the coupled cluster method. The four lowest ionization potentials are then calculated, leading to the ground and low excited states of the neutral species. The first three IPs describe ionization from the externalp state of the halogen atom, whereas the fourth corresponds to ionization from the NH3 or H2O moiety, leading to charge transfer complexes. These complexes were recently observed in the photoelectron spectrum of ClNH3, in full accord with our calculations.Supported in part by the U.S.-Israel Binational Science Foundation  相似文献   

11.
XU Xuan  PENG Qi  XIE Mei-Xiang 《结构化学》2012,31(9):1287-1294
The structures of complexes [MⅡ2Cl4L2] and [MⅢ2Cl7L]- (M = Mo, Re; L = Ph2Ppy, (Ph2P)2py) were calculated by using density functional theory (DFT) PBE0 method. Based on the optimized geometries, the natural bond orbital (NBO) analyses were carried out to study the nature of Re-Re and Mo-Mo bonds. The conclusions are as follows: the M-M distances in two-Ph2Ppy or (Ph2P)2py complexes [MⅡ2Cl4L2] are shorter than those in mono-Ph2Ppy or (Ph2P)2py complexes [MⅢ2Cl7L]- due to the double bridged N-C-P interactions. For singlet of all complexes, there is ReⅢ-ReⅢ or MoⅡ-MoⅡ quadruply bond in complex [Re2Cl7L]- or [Mo2Cl4L2], while only ReⅡ-ReⅡ or MoⅢ-MoⅢ triply bond in complex [Re2Cl4L2] or [Mo2Cl7L]-. The most stable spin state of 2 and 6, triplet, only contains triple ReⅢ-ReⅢ bond. Because the LPCl → BD*Re-Re delocalizations weaken the Re-Re bond, the distance of ReⅢ-ReⅢ quadruple bonds in [Re2Cl7L]- is slightly longer than that of ReⅡ-ReⅡ triple bonds in [Re2Cl4L2]. Moreover, due to the delocalizations from the lone pair electrons of the remaining P' atom to the M-M antibonding orbitals, the M-M distance in (Ph2P)2py complexes is slightly longer than that in Ph2Ppy complexes.  相似文献   

12.
采用密度泛函方法(B3LYP)优化了MX2(AsH3)2[M=Pd;X=Cl(1),Br(2),I(3)和M=Pt;X=Cl(4),Br(5),I(6)]的基态结构,得到的几何参数与实验结果符合.以基态几何为基础,将TD-DFT方法用于计算标题配合物的电子吸收光谱.研究结果表明,金属的dx2-y2与配体所组成的反键轨道为LUMO轨道,从而该类配合物具有d-d跃迁属性的吸收带;在多数跃迁过程中,配体也有较大的贡献.  相似文献   

13.
在B3LYP/6-31G(d,p)水平上优化了Cl原子与CH3COCH2Cl反应的各驻点的几何构型,并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态的结构和反应物、产物的连接性进行了验证。采用高精确模型G3MP2方法进行单点能计算,构建了反应的势能剖面。计算结果表明,标题反应有抽氢反应、加成-消除反应、取代反应3种反应机理6条反应通道。利用经典过渡态理论(TST)和正则变分过渡态理论(CVT)计算了各反应通道在200~2000 K温度范围内的速率常数,并用小区率隧道效应模型(SCT)对抽氢反应进行校正。计算结果显示,反应有一定的变分效应,计算的总反应速率常数与文献报道的实验值符合得较好,速率常数的三参数表达式为k=2.33×10-19T2.54exp(567.07/T)cm3·mol-1·s-1。  相似文献   

14.
《Polyhedron》2002,21(12-13):1163-1175
The results of density functional theory (DFT) calculations on a set of binuclear nonachloride complexes M′M″Cl9 4− (M′=V, Nb, Ta; M″=Cr, Mo, W) and M′M″Cl9 2− (M′=Cr, Mo, W; M″=Mn, Tc, Re), in which each metal possesses a nominal d3 valence electronic configuration, are reported. When compared with previous studies on same-group dimers (typified by the M′M″Cl9 3− complexes of the chromium triad), the present results display an increased tendency for electron donation from M′ to M″. Structural trends evident for the M′M″Cl9 4− and M′M″Cl9 2− series of dimers are remarkably consistent: weak ferromagnetic coupling between M′ and M″ is the most favorable intermetallic interaction when M″ is a first-row transition metal, antiferromagnetic coupling dominates when M′ is first-row but M″ is second- or third-row, and metalmetal triple bond formation generally yields the lowest-energy structure when neither metal is first-row. These structural trends, and other characteristics of the dimers described here, can be satisfactorily rationalized in terms of the tendency for electron transfer from M′ to M″, coupled with effects due to spin polarization and ligand field splitting of the valence d orbitals on M′ and M″.  相似文献   

15.
黄燕  黄晓  许旋 《物理化学学报》2013,29(6):1225-1232
应用密度泛函理论PBE0 方法研究具有分子导线潜在应用的金属串配合物M3(dpa)4Cl2 (1: M=Co, 2: M=Rh, 3: M=Ir; dpa=dipyridylamide)在电场作用下的几何和电子结构. 结果表明: 配合物基态均是二重态. 1和2的M36+金属链形成三中心三电子σ键, 3 中M36+形成三中心四电子σ键且存在弱的δ键. 随金属原子周期数增大其M―M键增强、LUMO与HOMO能隙减小、金属原子的反铁磁耦合减弱以至消失且自旋密度向配体的离域增强. 在Cl4→Cl5 电场作用下, 低电势端的M3-Cl5 键缩短, 高电势端的M2―Cl4 键增长, M―M平均键长略为缩短, M―M键增强, 有利于分子线的电子传递; 分子能量降低, 偶极矩线性增大. 低电势端Cl5的负电荷向高电势端Cl4 转移, 且3 中金属原子的正电荷由高电势端向低电势端的转移较明显, 自旋电子由低电势端向高电势端金属原子移动, 但桥联配体dpa-与M和Cl 所在的分子轴间没有电荷转移. 电场使LUMO与HOMO能隙减小, 有利于分子的电子输运. 随金属原子周期数增大, 电场作用下M―M平均键长变化减小, LUMO、HOMO的能级交错现象减少.  相似文献   

16.
The complex Re2Cl6(P-n-Bu3)2 prepared in situ reacts with CH3CN to form a blue-green solution. Addition of the chelating phosphine bis(diphenylphosphino)methane (dppm) results in the formation of the complex [Re2Cl3(-dppm)2(NCCH3)2][Cl] (1) upon heating. The two acetonitrile molecules adopt a trans geometry on the rhenium center with the axially coordinated chlorine. The analogous trans benzonitrile species [Re2Cl3(-dppm)2(NCC6H5)2][Cl]·2CH2Cl2 (2) is synthesized under the same reaction conditions. The coupling constants of the AABB 31P{1H} NMR spectra of the compounds were elucidated from 31P–31P homonuclear J-resolved NMR experiments. Additional characterization methods include 31P{1H} NMR spectroscopy, UV-vis spectroscopy, and X-ray crystallography.  相似文献   

17.
The complexes [Et4N][(Ph3P)2{MS2 MS2Fe}Cl2] (M=Mo,M=Ag;M=W,M=Cu, Ag) have been obtained by reaction of [Et4N]2[S2 MS2FeCl2] (M=Mo, W) with Cu(PPh3)3Cl or Ag(PPh3)3NO3 in MeCN/CH2Cl2, respectively. Crystal data for [Et4N][(PPh3)2 {AgS2MoS2Fe}Cl2] (I): triclinic, P (No. 2),Z=2,a=13.41(1)Å,b=15.54(1)Å,c=12.30(1)Å, =105.24(6)°, =94.63(7)°, =101.38(6)°, andV=2399(4)Å3. The bond lengths of Mo-Fe bond and the Mo-Ag distance are 2.756(2)Å and 3.033(2)Å, respectively. Crystal data for [Et4N][(PPh3)2 {AgS2WS2Fe}Cl2] (II): triclinic, P (No. 2),Z=2,a=13.457(5))Å,b=15.601(6)Å,c=12.338(4)Å, =105.20(3)°, =94.61(4)°, =101.43(4)°, andV=2426(2)Å3. The bond length of W-Fe bond and the W-Ag distance are 2.786(2)Å and 3.076(1)Å, respectively. Crystal data for [Et4N][(PPh3)2 {CuS2WS2Fe}Cl2] (III): triclinic, P (No. 2),Z=2,a=13.498(5)Å,b=15.372(4)Å,c=12.340(4)Å, =105.54(2)°, =93.32(3)°, =101.40(3)°, andV=2401(1)Å3. The bond lengths of W-Fe bond and the W-Cu bond are 2.800(1)Å and 2.851(1)Å, respectively.  相似文献   

18.
严宣申 《化学教育》2004,25(6):63-64
和强酸制弱酸,HCl NaCH3COO=NaCl CH3COOH,难溶物转化为更难溶物,AgCl NaI=NaCl AgI相同,氧化还原反应,如Cl2 2NaBr=2NaCl Br2,被氧化产物(Br2)的氧化性弱于使用的氧化剂(Cl2),被还原产物(NaCl)的还原性弱于原先的还原剂(NaBr)。显然,酸(碱)性强度、难溶的难溶程度、氧化性(还原性)倾向相差越大,以上诸反应越完全。  相似文献   

19.
Treatment of platinum(II) diamine [Pt(N,N-DimeTm)Cl2] (I) with pyridine gave tetramine [Pt(N,N-DimeTm)Py2]Cl2 (II); by oxidation with chlorine this was converted to Pt(IV) triamine, [Pt“(N,N-DimeTm(Py)Cl3]Cl (III) with a six-membered chelate ring. According to X-ray diffraction data, the reaction of complex II with chlorine is accompanied by removal of the pyridine molecule from the trans-position to the NH2 group of N,N-dimethyltrimethylenediamine. The reaction of complex III with chlorine at 20°C afforded a mixture of compounds (IV) and the complex [Pt“(CH3)2N(CH2)2C(O)NH”(Py)Cl3] (V) with an amidate six-membered metal ring, dimethylpropioamide, which was also isolated upon refluxing a mixture of IV in an aqueous solution. The UV/Vis and IR spectra of the obtained complexes were studied, and X-ray diffraction analysis of I, III, and V was performed. The crystals of I are triclinic, space group P $ \bar 1 $ ; a = 7.6526(4) Å, b = 11.5571(6) Å, c = 12.4432(7) Å, α = 113.85(1)°, β = 96.54(2)°, γ = 106.78(2)°; Z = 4; R hkl = 0.051. The crystals of III are monoclinic, space group C2/c; a = 36.715(2) Å, b = 7.8179(4) Å, c = 29.721(16) Å, β = 127.80(1)°; Z = 16; R hkl = 0.036. The crystals of V are monoclinic, space group P21/n; a = 7.0398(6) Å, b = 27.458(2) Å, c = 7.687(6) Å, β = 106.270(1)°; Z = 4; R hkl = 0.052.  相似文献   

20.
利用精密自动绝热热量计测定了Nd(Gly)2Cl3·3H2O在80-357K和Pr(Ala)3Cl3·3H2O在80-374K温区的热容. 根据两个化合物的热容计算出了相对于参考温度298.15K的热力学函数(HT?H298.15)和(ST?S298.15). 根据热重(TG)分析结果, 提出了这两个稀土化合物可能的热分解机理. 利用溶解-反应恒温热量计测定相关化合物的溶解焓并设计盖斯热化学循环, 计算出了两个化合物的标准摩尔生成焓.  相似文献   

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