CdSe/CdS/SiO2 复合纳米球的制备及发光性能

采用两相法合成了CdSe/CdS核-壳结构的量子点, 用氨水催化水解正硅酸乙酯制得复合结构的CdSe/CdS/SiO₂发光纳米球. 通过对量子点用量、氨水用量、反应时间及溶剂比例等实验条件的调节, 得到了单分散性较好, 尺寸在23~145 nm的复合发光纳米球. 利用紫外-可见吸收光谱和荧光发射光谱对其发光性能进行了研究, 同时利用透射电镜(TEM)观察复合纳米球的形貌. 结果表明, 复合发光纳米球样品的最高荧光量子产率可达8%.     

N—O键解离焓的密度泛函理论研究

在高精度计算方法G3和G3B3的基础上,比较了密度泛函理论(DFT)十几种方法对N—O键解离焓(BDE)相对于实验值的计算精度,发现用B3P86方法计算15种化合物N—O键的BDE,均方根误差最小,仅为6.36kJ·mol-1,计算值与实验值的线性相关系数为0.991.在此基础上,用该方法分别计算了非芳香化合物及芳香化合物的N—O键BDE.通过自然键轨道分析,发现部分N—O键的BDE与N—O键的键长、原子电荷密度及键级之间存在定量关系.此外,在B3P86方法的基础上预测了几种典型的杂环芳香化合物N—O键BDE值.     

Thiophenol and thiophenol radical and their complexes with gold clusters Au5 and Au6

The longstanding controversy between experiment and theory regarding which conformer of thiophenol, planar or perpendicular, is the most stable and what is the magnitude of the corresponding rotational barrier of the S–H group is discussed. We propose a variety of rather modest high-level computational methods within the density theory, which corroborate the experimental data. These methods demonstrate that the planar structure of thiophenol is the most stable and the magnitude of the rotational barrier falls within the experimental range of 3.35±0.84 kJ mol⁻¹. However, the barrier is of the order of RT at room temperature, which might prevent to clearly identify the most stable conformer of thiophenol in experiments and leads to a large-amplitude motion of the thiolic hydrogen. On the other hand, such low value of the barrier may lead to some error in evaluating the thermodynamic properties of thiophenol within the rigid-rotor-harmonic oscillator model, in particular for the bond dissociation enthalpy. We also show the existence of a large entropy contribution to the Gibbs free energy difference between the planar and perpendicular conformers which is the order of the rotational barrier (≈4 kJ mol⁻¹). This might be of interest for experimental study. The most stable complexes of thiophenol with the gold clusters Au₅ and Au₆ are also investigated. It is shown that the sulfur atom prefers to anchor to two- and three-coordinated atoms of gold in these clusters to form a strongly directional gold–sulfur bond. The hydrogen abstraction from the S–H group of thiophenol bonded to the two-coordinated gold atom in Au₅ yields the bridging Au–S dibond and results in a spectacular reduction of the bond dissociation energy of thiophenol by nearly a factor of three.     

Preparation of Metallaiminophosphoranes and Their Reactivity

Treatment of [Cp*(CO) 2 M{P(NHPh)(OMe) 2 }]PF 6 (M = Fe and Ru) with NaNH 2 gives metallaiminophosphoranes, Cp*(CO) 2 M{P(NPh)(OMe) 2 }. The x-ray structures and reactivity of the complexes are reported.     

NEW CARBON-PHOSPHORUS BOND CONTAINING COMPOUND IN THE REACTION OF 2-ACETYLTHIOPHENE WITH PHOSPHORUS PENTACHLORIDE

Abstract

The treatment of 2-acetylthiophene with phosphorus pentachloride led, besides other products reported in previous studies, to 2-(2-thienyl)-2-chloroethenephosphonic acid in 16% yield. This compound was transformed, in the course of purification attempts, into 2-(2-thienyl)-2-oxoethanephosphonic acid. Full spectroscopic data for both compounds are provided.     

Estimation of useful yields for electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS)

Useful yield for electrospray droplet impact/secondary ion mass spectrometry was estimated. The mixtures of C₆₀/rhodamine B and C₆₀/Aerosol OT were used as the samples for the positive and negative mode of operations, respectively. By assuming that (i) the desorption efficiencies are about the same for C₆₀, rhodamine B and Aerosol OT, and (ii) desorption of ionic compounds directly gives the secondary ion signals, the useful yields (i.e. total ions generated divided by the total molecules desorbed) for C₆₀ were estimated to be ~0.1. This value should be regarded as the upper limit because the neutralization of positive and negative ions in the plume and desorption of ionic compounds as neutral species are not taken into account. Copyright © 2012 John Wiley & Sons, Ltd.     

A conjugated alkyne functional bicyclic polybenzoxazine with superior heat resistance

A difunctional benzoxazine (coPh‐apa) with a conjugated alkyne group is synthesized by the oxidative coupling reaction from a monocycle‐benzoxazine (Ph‐apa) containing an alkyne group. A model compound, 1,4‐diphenylbutadiyne (coPa), is used to study the curing reaction process of coPh‐apa by DSC, Fourier transform infrared spectroscopy, and ¹³C NMR, and the results suggest that the conjugated alkyne groups are involved in the crosslinking reaction via the trimerization reaction of the conjugated alkynyl groups and the Diels–Alder reaction. Furthermore, thermal properties of the polybenzoxazine are studied by dynamic thermomechanical analysis and thermogravimetric analysis. A glass‐transition temperature (T_gs) of as high as 412 °C and a char yield of 75.6% at 800 °C under nitrogen are obtained with the aid of the conjugated alkyne groups. Its excellent heat resistance dominates most thermosetting resins and will serve for heat shields. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1587–1592     

Summary of ISO/TC 201 Standard: ISO 22415—Surface chemical analysis—Secondary ion mass spectrometry—Method for determining yield volume in argon cluster sputter depth profiling of organic materials

The International Standard ISO 22415 provides methods to measure sputtering yield volumes of organic test materials using argon cluster ions. The test materials should consist of thin films of known thicknesses between 50 and 1000 nm. The format of the test materials, the measurement of sputtering ion dose, sputtered depth, and reporting requirements for sputtering yield volumes are described.     

氯化铜的少溶剂固态连串配位化学反应

在少量水的存在下,由于 NH₄[CuCl₃]对水不稳定,CuCl₂·2H₂O 与氯化铵的配位化学反应只能得到 1:2 产物(NH₄)₂[CuCl₄(H₂O)₂];但在无水乙醇中,无水 CuCl₂与氯化铵按 1:1或 1:2的物质的量之比混合时,能相应地得到 NH₄[CuCl₃]或(NH₄)₂[CuCl₄]。CuCl₂·2H₂O与 2,2''-联吡啶(bipy)的少溶剂固态化学反应仍能像固态化学反应一样,根据反应物的配比生成相应的唯一产物,但在物质的量之比为1:1的反应中发现1:2产物曾经形成。热力学分析说明,如果连串反应的后一步的Δ_rG^⊖大于前一步的,则上述反应现象是可能的。     

聚醚醚酮链结构与反应的模型化合物的量子化学研究

利用ＡＭ１方法对聚醚醚酮模型化合物全优化，结果为：芳环平均相互扭转角为３３．０度，桥键角１１７．０－１１８．０度，其分子结构拓扑图形表明：所有苯环（核）为平面构型，但其内角扭曲；其氢原子对苯环构型无实质性贡献，在更长链的计算中，冻结苯核与氢原子也得出满意结果，根据Ｍｕｌｌｉｋｅｎ键序与电荷讨论了醚交换与磺化反应。