Multiply Charged Anions,Maximum Charge Acceptance,and Higher Electron Affinities of Molecules,Superatoms,and ClustersSCI北大核心CSCD

The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs X^Q-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E(N, v_ex), is a continuous function of the average electron number, N, and the external potential, v_ex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E(N, v_ex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Q_max, and the higher electron affinities, A_Q, as simple functions of the first electron affinity, A₁, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Q_{max, calc} = 1 + 12A₁/7(I -A₁). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Q_{max, GS} = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A₁/(I -A₁). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF₃), super-alkali species (OLi₃), and neutral or charged transition-metal complexes, AB_mL_n^0/+/-. The calculated second electron affinity A_{2, calc} = A₁-(7/12)(I -A₁) is linearly correlated to the literature references A_{2, lit} with a correlation coefficient R = 0.998. A₂ or A₃ values are predicted for further 24 species. The appearance sizes, n_ap^3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature.     

Fukui函数和局域软度应用于亲电加成反应的区位选择性的研究

Fukui函数、局域软度、广义Fukui函数以及广义软度通常被称为反应描述符。使用它们研究和探讨了HCl与不对称烯烃以及溴苯硒与不对称苯乙烯的亲电加成反应的区位选择性。在MP2/6-311++G(d, p)理论水平下,采用有限差分方法计算这些反应描述符,同时也使用ABEEMσπ方法进行了计算。ABEEMσπ模型下的局域软度和广义局域软度,分别结合局域硬-软酸碱(HSAB)原理,得出亲电试剂氯化氢与溴苯硒,更容易进攻不对称乙烯和苯乙烯中的马氏碳原子,符合马氏规则。而有限差分方法不能完全地解释该系列反应的区位选择性。此外,主要产物所对应的马氏碳原子的广义局域软度值,就能够预测出此类反应的活性序列,所得结果与速率常数有很好的关联。     

Structural characteristics of pyrocarbon-fumed silica

Two series of pyrocarbon/fumed silica (CS) samples at different carbon concentrations C_C=0.5–64 wt.% (first series, CSI) and 2.6–53 wt.% (second series, CSII) synthesised by means of pyrolysis of CH₂Cl₂ at fumed silica substrate (S_BET=297 (CSI) and 232 (CSII) m² g⁻¹) under slightly different conditions were studied by using TEM, FTIR-PAS, DTG, and nitrogen adsorption–desorption methods. On methylene chloride carbonisation, disordered carbon deposits can form mainly in the inter-particle volume of secondary particles (aggregates of primary particles and agglomerates of aggregates) covering the surfaces of primary silica particles; therefore, marked reduction of the pore (gaps between primary particles) volume and the specific surface area is observed with increasing C_C. Estimation of distributions of the pore f_SCD(R_p) and particle f(a) sizes using a self-consistent method with binary regularisation with respect to both f_SCD(R_p) and f(a) shows that the average size of particles increases (silica particles are covered by pyrocarbon) and individual pyrocarbon particles (up to 50 nm according to TEM) also appear. Structural parameters of carbosils are characterised by nonlinear changes with increasing carbonisation time. Surface functionalities on CS samples correspond to aromatic and twinned CC bonds with contribution of oxygen-containing groups.     

自然轨道福井函数和成键活性描述符应用于解释苯硫醌和1, 3-二烯的[2+4]和[4+2]环加成反应中的成键机理

苯硫醌与脂肪族烯烃可以发生[2+4]和[4+2]环加成反应。为了解释这些环加成反应中的成键过程,本文使用了自然轨道福井函数(NOFF)与成键活性描述符。自然轨道福井函数揭示了苯硫醌和脂肪族烯烃的键或轨道的亲电性,表明电子供体的成键轨道和电子受体的反键/成键轨道之间发生了电子转移,然后成环,在这一过程中有两个共价键形成,得到了环状产物。成键活性描述符表明共价键比较容易在一个分子中具有较大f_k1⁺值的k1原子与另一个分子中具有较大f_k2^-值的k2原子之间形成。自然轨道福井函数与成键活性描述符都可以有效解释苯硫醌与1, 3-二烯之间的[2+4]与[4+2]环加成反应的机理。     

The molecular structure and pseudorotational motion of 1,1-difluorosilacyclopetane as determined by gas-phase electron diffraction

The structure of 1,1-difluorosilacyclopentane has been studied by gas-phase electron diffraction. The molecule is found to have a barrier of pseudorotion of 2.25(90) kcal mol⁻¹. The potential function has minimum at the twist form (C₂) symmetry and maxima at the envelope forms. The major bond distances (itr)_g) and valence angles obtained from the least-squares refinements with error estimates are as follow: r(C---H) = 1.128(7) A, r(C---C)_av = 1.553(15) A, r(Si---F) = 1.582(6) A, r(Si---C) = 1.853(3) A, (CSiF) = 113.4′(3), CCC = 106°(1), and Tau(C1C2C3C4) = 56.0°(32).     

白光LED用Ce∶YAG单晶的光学性能与掺杂浓度分析

采用提拉法生长Ce∶YAG单晶, 通过X射线衍射和激发发射光谱对其晶相结构和光谱特性进行了表征, 研究了Ce∶YAG单晶封装白光LED的最佳掺杂浓度. 在455 nm蓝光激发下, Ce∶YAG单晶的发射光谱可由中心波长526 nm(5d¹²E_gГ_8g→4f ¹²F_7/2Г_8u)的宽发射带(500~650 nm)组成; 激发光谱由343 nm(4f ¹²F_5/2Г_7u→5d^{1 2}E_gГ_7g)和466 nm(4f ¹²F_5/2Г_7u→5d^{1 2}E_gГ_8g)2个激发峰组成; Stokes位移为2448 cm^-1, Huang-Rhys因子为6.12. 研究结果表明, Ce∶YAG单晶中Ce离子掺杂浓度与封装的白光LED之间有对应关系, 在650 nm红粉调节下Ce离子最佳掺杂浓度范围为0.034~0.066.     

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.     

1-乙基-3-甲基咪唑丙氨酸离子液体热力学性质的研究

用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸([C₂mim][Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01) K-(308.15±0.01) K温度范围内每隔5 K,测定不同质量摩尔浓度离子液体在水中的溶解焓(Δ_solH_m^θ).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(Δ_sol),并计算了其相对表观摩尔溶解焓(^ΦL).在298.15 K下,根据Glasser经验方法得到了格子能U_POT = 566 kJ·mol^-1,并计算了其阴阳离子水化焓值(ΔH⁺ + ΔH^-) = -620 kJ·mol^-1及阴离子水化焓ΔH^-([Ala]^-) = -387 kJ·mol^-1.此外,估算了[C₂mim][Ala]水溶液的热容(C_p(sol))和表观摩尔热容(^ΦC_p).     

Vibrational spectra and normal coordinate analysis of CF3 compounds Part XLVII. Vibrational spectra, normal coordinate analysis and electron diffraction investigation of CF3SiH3 and its deuterated varieties

The molecular structure of CF₃SiH₃ in the gas phase has been determined by electron diffraction analysis. Combined with a B₀ value derived from high resolution infrared spectra, this yielded r(SiC), 1.923(3) Å, r(SiH) 1.482(5) Å, r(CF) 1.348(1) Å, FCF 106.7(5)° and HSiH 110.3(10)° (r° values). The gas phase infrared and liquid phase Raman spectra of CF₃SiH₃, CF₃SiH₂D, CF₃SiD₃ have been measured and assigned, and force constants have been calculated by means of a normal coordinate analysis based on 52 experimental frequencies. The weakness of the SiC bond is confirmed by the low f(SiC) value of 2.54 N cm⁻¹. Infrared spectra recorded with a resolution of 0.04 cm⁻¹ at 240 K revealed rotational structure of vibrational bands. Rotational analyses of most parallel and a few perpendicular bands of CF₃SiH₃ and CF₃SiD₃ have been performed. Ground and excited state vibrational parameters have been obtained and used as supplementary data for the determination of the harmonic force field. Strong blending of all bands due to hot band cascades was noted.     

具有螺旋结构的金属镍有机-无机配位聚合物的合成及表征

在水热体系中合成了3个中心金属为镍离子, 以六配位扭曲八面体构型形成的具有螺旋结构的配位聚合物{[Ni₂L₂(bib)₂·2H₂O]·5H₂O}_n(1), [Ni₂L₂(bpy)]_n(2)和{[Ni₂L₂(bibpip)₂·2H₂O]·6H₂O}_n(3)[H₂L=4,4'-三苯胺二甲酸; bib=1,3-二(咪唑基)苯; bpy=4,4-联吡啶; bibpip=1,4-二(4-咪唑苄基)哌嗪]. 通过单晶及粉末X射线衍射、 红外光谱、 元素分析和热重分析对这3种化合物进行了表征. 结果表明, 化合物1属于单斜晶系, C2/c空间群, 其骨架为具有{4²·6⁵·8}拓扑结构的二维层结构; 化合物2属于斜方晶系, Fdd2空间群, 其骨架为具有{4⁸·5⁴·6³}拓扑结构的三维超分子网络; 化合物3属于三斜晶系, P\begin{array}{c}\bar{1}\end{array}空间群, 为1个五重穿插的三维超分子网络, 其骨架具有{4⁴·6²}拓扑结构.     

Cu2-MnO_x高效催化1,2,3,4-四氢喹啉氧化脱氢芳构化

采用新型无模板草酸盐路线制备了系列不同Cu含量的MnO_x催化剂(MnO_x、Cu1-MnO_x、Cu2-MnO_x、Cu3-MnO_x、Cu4-MnO_x、Cu2-450及Cu2-550),并应用于1,2,3,4-四氢喹啉(THQL)氧化脱氢芳构化。通过热重和热流分析(TG-DSC)、X射线衍射(XRD)、N2物理吸附-脱附、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能谱(EDS)、X射线光电子能谱(XPS)、H2程序升温还原(H2-TPR)、原子吸收光谱(AAS)手段对催化剂进行表征。结果显示在这七种锰氧化物中,Cu2-MnO_x具有高比表面积、增大的介孔平均孔径、较低的还原温度、最高的Mn~(3+)含量和吸附氧含量,最高的Mn~(3+)/Mn~(4+)。Cu2-MnO_x在温和的反应条件下,以廉价的空气为氧化剂、无碱添加剂的情况下对THQL芳构化转化率和喹啉(QL)选择性分别达99.1%、97.2%。催化剂套用五次后转化率还可达95.8%,选择性随着套用次数增加略有降低,这可能是Cu元素的流失所致。催化剂无定型结构、Mn~(3+)和吸附氧含量,Mn~(3+)/Mn~(4+)、晶格氧的流动性及CuO和MnO_x的协同作用是高催化活性的关键因素。     

高倍率性能纳微结构锂离子电池正极材料0.6Li2MnO3-0.4LiNi0.5Mn0.5O2的简易制备

采用快速共沉淀法合成了立方体的层状无钴富锂固溶体正极材料0.6Li₂MnO₃-0.4LiNi_0.5Mn_0.5O₂.通过X射线衍射(XRD), X射线光电子能谱(XPS),电感耦合等离子体(ICP),扫描电子显微镜(SEM),透射电子显微镜(TEM)及电性能测试等手段对材料进行了表征.结果表明,材料具有典型的α-NaFeO₂六方层状晶体结构且具有与目标材料相似的化学组成. SEM和TEM结果表明,材料由粒径为40-200 nm的纳米颗粒组装成立方体结构.在文中给出了一个立方团聚体可能的形成机理.电化学性能测试(2.0-4.8 V电压范围内(vs Li/Li⁺))显示该材料具有优异的倍率性能, 0.1C和10C倍率下的放电比容量分别是243和143 mAh·g^-1.此外,该材料具有良好的循环稳定性,即使在大倍率测试后, 0.5C倍率下循环72次仍显示出90.7%的高容量保持率.这种具有简易操作步骤和优异结果的共沉淀方法是一种经济的能够促进锂离子电池正极材料大规模应用的技术手段.     

基于共价有机框架复合材料的锂硒电池应用

本文利用溶剂热反应方法,在多壁碳纳米管(MWCNTs)管壁上生长了共价有机框架(TpPa-COF)材料,并将这种核壳多壁碳纳米管/共价有机框架纳米复合材料(MWCNTs@TpPa-COF)成功应用在锂硒电池上。利用场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)和傅里叶变换红外光谱(FT-IR)等手段对材料结构进行表征,结果表明多壁碳纳米管和共价有机框架材料成功复合。电化学测试结果表明,该材料在电流密度3C(1C=675mA·g~(-1))下的质量比容量为463.5 mAh·g~(-1),500次循环后能保持99%的库仑效率,表明锂硒电池具有优异的循环稳定性和较长的循环寿命。     

间歇电沉积法制备纳米MnOx/Ti膜电极及其催化氧化环己烷性能

高选择性氧化环己烷（CHA）制备环己酮和环己醇（KA油）具有重要的工业价值和应用前景. 本文提出采用间歇电沉积法制备纳米MnO_x催化剂负载多孔管式钛膜,构建电催化膜反应器（ECMR）催化氧化环己烷制备环己醇和环己酮. 利用场发射扫描电子显微镜（FESEM）、X射线衍射仪（XRD）和电化学工作站等表征手段对催化剂的结构与性能进行表征. 结果表明,间歇电沉积法制备的催化剂为纳米花球状γ-MnO₂. 与基体钛膜相比,MnO_x/Ti膜电极具有更优的电化学性能和传质性能. 此外,以MnO_x/Ti电催化膜为阳极,不锈钢网为阴极构建ECMR. 当环己烷初始浓度30 mmol·L^-1、反应温度30^oC、停留时间34.3 min、电流密度2.3 mA·cm^-2等条件下,ECMR环己烷转化率达25.6%,KA油总选择性高于99%. 同时,ECMR重复使用8次后表现较高催化稳定性.     

Pitzer方程应用于离子液体[Cnmim][H2PO4](n= 3, 4, 5, 6)溶解焓研究

在298.15 K下,利用等温环境溶解反应热量计,测定了离子液体[C_nmim][H₂PO₄] (n= 3, 4, 5, 6) (1-烷基-3-甲基咪唑磷酸盐)在水中不同浓度的摩尔溶解热(Δ_solH_m),根据Pitzer电解质溶液理论计算得到了标准摩尔溶解焓(Δ_solH_m⁰)和Pitzer焓参数：β_MX^(0)L, β_MX^(1)L,和C^ϕL,并计算了表观相对摩尔焓。通过推导讨论,得到了离子液体[C_nmim][H₂PO₄](n= 3, 4, 5, 6)同系物每摩尔亚甲基对标准摩尔溶解焓的贡献。     

Temperature dependence of the rate constant for reactions of hydrated electrons with H, OH and H2O2

The temperature dependence of the rate constants, for the reactions of hydrated electrons with H atoms, OH radicals and H₂O₂ has been determined. The reaction with H atoms, studied in the temperature range 20–250°C gives k(20°C) = 2.4 × 10¹⁰M^-1s¹ and the activation energy E_A = 14.0 kJ mol^-1 (3.3 kcal mol^-1). For reaction with OH radicals the corresponding values are, k(20°C) = 3.1 × 10¹⁰M^-1s^-1 and E_A = 14.7 kJ mol^-1 (3.5 kcal mol^-1) determined in the temperature range 5–175°C. For reaction with H₂O₂ the values are, k(20°C) = 1.2 × 10¹⁰M^-1s^-1 and E_A = 15.6 kJ mol^-1 (3.7 kcal mol^-1) measured from 5–150°C. Thus, the activation energy for all three fast reactions is close to that expected for diffusion controlled reactions. As phosphates were used as buffer system, the rate constant and activation energy for the reaction of hydrated electron with H₂PO₄^- was determined to k(20°C) = 1.5 × 10⁷M^-1s^-1 and E_A = 7.4 kJ mol^-1 (1.8 kcal mol^-1) in the temperature range 20–200°C.     

Influence of Isotope Effects on Product Polarizations of N(2D)+D2, N(2D)+H2 and N(2D)+HD Reactive Systems

To figure out the influence of isotope effect on product polarizations of the N(²D)+D₂ reactive system and its isotope variants, quasi-classical trajectory(QCT) calculation was performed on Ho’s potential energy surface(PES) of ²A″ state. Product polarizations such as product distributions of P(θ_r), P(φ_r) and P(θ_r,φ_r), as well as the generalized polarization-dependent differential cross sections(PDDCSs) were discussed and compared in detail among the four product channels of the title reactions. Both the intermolecular and intramolecular isotope effects were proved to be influential on product polarizations.     

纤锌矿型β-CuGa1-xZnxO2的Zn2+取代Ga3+不等价掺杂对其结构及光催化性质的影响

采用离子交换法制备了Zn²⁺在Ga-位不等价掺杂的功能陶瓷材料（β-CuGa_1-xZn_xO₂）. 通过X射线衍射（XRD）和透射电子显微镜（TEM）对材料的晶体结构进行表征, 通过原位高温X射线衍射（HT-XRD）和同步热分析仪（TG-DSC）对材料的热稳定性进行表征, 通过紫外-可见漫散射光谱（UV-Vis DRS）以及第一性原理计算对材料的光学性质进行研究, 并通过甲基橙（MO）的降解反应评价了Zn²⁺在Ga-位的引入对该功能陶瓷光催化性能的影响. 结果显示, Zn²⁺的引入引起带隙变宽, 吸光范围变窄, 自发极化变小, 进而导致单位时间内生成的高活性物质减少, 不利于降解反应. 通过光致发光光谱（PL）对降解机理进行了初步探究. 根据实验结果提出了改进β-CuGaO₂性质的可能方法.     

醋酸铅作为铅源合成CH3NH3PbBr3-xClx纳米晶体颗粒

Lead acetate, which is highly soluble in dimethylformamide, was used to synthesize mixed halide perovskite CH₃NH₃PbBr_3-xCl_x (MA = CH₃NH₃, 0 ≤ x ≤ 3) nanocrystals (NCs). This method provides an approach to address the low solubility of lead halides, especially lead chloride. Different Br/Cl ratios in MAPbBr_3-xCl_x lead to various optical properties. The photoluminescence emission peak can be tuned from 399 to 527 nm. Their full-widths at half-maxima (FWHM) are about 20 nm. MAPbBr_3-xCl_x NCs have an average diameter of ~(11 ± 3) nm and have uniform dispersion in toluene. The MAPbBr₃ NCs have a long average recombination lifetime (τ_ave = 97.4 ns) and a photoluminescence quantum yield (PLQY) of up to 73%.