Synthesis and Characterizations of Ferrocenyl Carbonyl Chromium and Cobalt Clusters

Two novel bimetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅)–C≡C–C₆H₄–Fc] (Fc = C₅H₅FeC₅H₄] (1) and [Cr(CO)₃(η ⁶-C₆H₅)–C ≡ C–Fc–C(CH₃)₂–Fc] (3), were synthesized by the Sonogashira coupling reaction. By using of (1) and (3) as ligands to react with Co₂(CO)₈, two others novel polymetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}–C₆H₄–Fc] (2) and [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}Fc–C(CH₃)₂–Fc] (4) were obtained. Four carbonyl complexes were characterized by elemental analysis, FT-IR, NMR and MS. The molecular structures of complexes (1), (2) and (4) were determined by single crystal X-ray diffraction. The interactions among the ferrocenyl, Cr(CO)₃ and Co₂(CO)₆-η ²-μ ²-C≡C– units were investigated by cyclic voltammetry.     

Density functional theory investigation on the electronic structure of furo[3,4-b]pyridine-type heterocyclics: from monomer to polymer

The geometries and electronic properties of six polymers based on furo[3,4-b]pyridine-type heterocyclics were studied using density functional theory (DFT) at the B3LYP/6-31G(d) level. Bond lengths, bond critical point (BCP) properties, nucleus-independent chemical shift (NICS), and Wiberg bond indexes (WBIs) are analyzed and correlated with conduction properties. The changes of bond length, BCP properties, NICS, and WBIs all show that the conjugational degree is increased with main chain extension. The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. And the HOMO–LUMO energy gap (E _g) is decreased steadily upon chain elongation. The results suggest that the six polymers all have lower energy gaps (in the range of 0.39–0.58 eV), which indicate that these proposed polymers are good candidates for the conductive materials.     

具有聚集诱导发光效应的咔唑基三苯乙烯衍生物单体及聚合物

合成了一类新的咔唑基三苯乙烯衍生物单体及其聚合物.利用示差扫描量热法(DSC)、热重分析法(TGA)、紫外可见分光光度法和荧光分光光度法等对单体和聚合物的性能进行了初步的表征.实验结果表明,该单体和聚合物具有较高的玻璃化转变温度(Tg),分别为210℃和229℃;单体和聚合物均具有很高的热稳定性,热失重5%的温度分别为466℃和467℃;单体具有明显的聚集诱导发光性能(AIE),而聚合物则具有聚集诱导增强发光性能(AIEE);所合成的单体和聚合物有望在OLED器件以及化学传感器上得到应用.     

Ozone source attribution during a severe photochemical smog episode in Beijing, China

Beijing,the capital of China,frequently suffers from the high levels of ozone in summer.A 3-D regional chemical transport model,the Comprehensive Air Quality Model with extensions(CAMx),has been used to simulate a heavy O3 pollution episode in Beijing during June 26―July 2,2000.Ozone Source Apportionment Technology(OSAT) and Geographic Ozone Assessment Technology(GOAT) were applied to quantify the contributions of the precursor emissions from different regions to O3 concentrations in Beijing,to identify the...     

ENHANCED MECHANICAL PROPERTIES OF POLYPROPYLENE/SILICA NANOCOMPOSITES WITH SURFACE MODIFICATION OF NANO-SILICA VIA IN SITU COPOLYMERIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

Nano-sized silica particles were modified with methacryloxy-propyltrimethoxysilane(MPS) followed by in situ copolymerization of methyl methacrylate(MMA) and butyl acrylate(BA).These modified nanoparticles were compounded with polypropylene(PP) to prepare PP/silica nanocomposites.PMMA grafted on nano-silica enhances the dispersion of the nanoparticles and interfacial adhesion,decreases the size of PP spherulites in nanocomposites and leads to increasing the Young's modulus and toughness of PP/silica nanoc...     

Electrochemical behavior and voltammetric determination of tryptophan based on 4-aminobenzoic acid polymer film modified glassy carbon electrode

Herein, a novel electrochemical method was developed for the determination of tryptophan based on the poly(4-aminobenzoic acid) film modified glassy carbon electrode (GCE). The electrochemical behaviors of tryptophan at the modified electrode were investigated. It was found that the oxidation peak current of tryptophan at the modified GCE was greatly improved compared with that at the bare GCE. The effects of supporting electrolyte, pH value, scan rate, accumulation potential and time were examined. The oxidation peak current of tryptophan was proportional to its concentration over the range from 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol L⁻¹. The limit of detection was evaluated to be 2.0 × 10⁻⁷ mol L⁻¹. The proposed method was sensitive and simple. It was successfully employed to determine tryptophan in pharmaceutical samples.     

Theoretical study on the reaction of the Δ ground state of ZrO with CS2 in the gas phase

The mechanisms for the three products ZrS⁺, and ZrOS⁺ of the title reaction have been studied by using B3LYP/6-311+G* and CCSD(T)/SDD+6-311+G* methods. It is found that both ZrS⁺ and formations involve the same O/S exchange process via a four-center transition state TS12 to form an intermediate IM2. Exception of that IM2 can dissociate into the ZrS⁺ product, a favorable intramolecular rearrangement mechanism associated with the formation has been identified, which explains why ZrS⁺ was excluded as a precusor for the formation and why the lower efficiency of the ZrS⁺ formation was observed in experiment. For the formation of ZrOS⁺, two parallel channels (path A and B) yielding their corresponding product isomer have been identified. Path B involving an insertion–elimination mechanism with a calculated barrier underestimated by ca. 25.0 kJ/mol should be attributed to the threshold of 114.8 ± 12.5 kJ/mol assigned in the experiment. But path A should make some contributions to the formation of ZrOS⁺ at elevated energy.     

Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

环境中有机磷污染物碱性的理论研究

有机膦化合物的碱度对深入了解有机膦类污染物的降解有着重要的意义. 发展基于第一性原理的理论方法精确计算有机膦化合物的pKa值有重要意义. 本研究工作发展了精确计算有机膦阳离子化合物pKa值的方法: 用B3LYP/6- 31＋G(d)优化气相结构, PBEPBE计算单点能量, IEFPCM/Bondi (f＝1.0)计算溶剂化能. 理论值与实验值比较, 其平均偏差和均方根差分别为－0.6 pKa单位和0.7 pKa单位. 基于此方法, 我们研究了常见有机膦污染物阳离子的碱性, 定量计算其pKa值. 并进一步讨论了这类化合物的α取代效应和远程取代效应对其碱性的影响, 总结了影响杂环有机膦化合物阳离子酸性的因素.