Study of the organic carbon content of silica gel carbonised by pyrolysis of alcohols

Silica gel partially carbonised by pyrolysis of a mixture of C₇ aliphatic and aromatic alcohols at 773 K for 6 h was studied by means of transmission electron microscopy, temperature-programmed desorption (TPD), reaction gas chromatography, and quantum chemical methods. Pyrolysis of n-heptanol and benzyl alcohol at the silica gel surface results in formation of the carbon deposit (globules of 100–500 nm on the outer surfaces of silica gel and smaller carbon particles distributes on the external and internal surfaces of the oxide matrix) and grafted different organic compounds, which begin to desorb at relatively low temperatures (350–500 K) and activation energies of ≈70–120 kJ mol⁻¹. These compounds are not entirely removed from the surface on washing in solvents and subsequent drying at 470 K, as they can be packed in the pyrocarbon deposit between graphene sheets or in silica gel pores partially filled or blocked by pyrocarbon. Some of these compounds have also the second high-temperature TPD maximum at T close to the temperature of alcohol pyrolysis.     

微小型矩形槽道平板热管传热性能的数值模拟

在充分考虑槽道内汽-液界面剪切摩擦力下,建立了微小型矩形槽道平板热管的数学模型,通过迭代计算得出工质质量流量、流体和蒸汽平均流速、汽一液界面弯月面半径及蒸汽和液体压力沿轴向分布规律,最后对热管外壁面温度值的计算结果和实验结果进行了比较,两者数值基本一致,证明了所建数学模型与实际相符,对热管的理论分析具有指导意义。     

Microwave spectra, molecular structure and theoretical calculation of two isotopic species of acetyl isocyanate CD3C(O)NCO and CH3C(O)NCO

The microwave spectra of two isotopic species of acetyl isocyanate, ¹³CH₃C(O)NCO and CD₃C(O)NCO, were observed in order to determine the r_o structure and confirmation of the molecular conformation. These isotopic species were prepared by reacting acetyl-2-¹³C-chloride or acetyl-d₃ chloride with sliver cyanate. The rotational spectra of A-level in 26.5-60.0 GHz region have been observed by Stark-modulated microwave spectrometer. Some absorption lines in E-level were observed in ¹³CH₃C(O)NCO. The rotational constants in the ground vibrational state were determined to be A = 10654.8(18), B = 2177.32(2), and C = 1827.65(2) MHz for ¹³CH₃C(O)NCO, and A = 9713.90(6), B = 2042.04(2), and C = 1722.78(2) MHz for CD₃C(O)NCO, respectively. The values of ΔI (= I_c − I_a − I_b) of the ¹³C species (−3.024(13) uŲ) and the d₃ species (−6.163(3) uŲ) indicate that the molecule has C_s symmetry. The r_s coordinates of the carbon atom in the methyl group were determined to be |a| = 2.183(3), |b| = 0.706(9), and |c| = 0.080(87) Å. The determined coordinates were in agreement with those calculated for the cis form, in which the carbonyl group is eclipsed by the NCO group. The six structural parameters of the cis form were adjusted by fitting to the observed rotational constants. The observed rotational constants of the cis form were in better agreement with those calculated using the QCISD/6-31G (d, p) level rather than those calculated using the MP2/6-31G (d, p) level. The barrier of internal rotation of the methyl group was determined as 4.283(16) kJ mol⁻¹ in ¹³CH₃C(O)NCO. The structural tendencies and the relationship between ∠RNC and ¹⁴N quadrupole coupling constants (χ_cc) were discussed.     

海藻酸钙凝胶微球粒径的理论计算与实验

通过静电液滴发生器制备海藻酸钙凝胶微球,通过理论推导得到了微球粒径的计算公式.理论计算的结果表明,凝胶微球粒径的大小取决于静电压、电极距离、针头内径大小、注射器流速、海藻酸钠粘度和表面张力以及凝胶化体积收缩系数.理论计算结果与实验结果吻合得相当好.     

Theoretical study of the potential-energy surface of C2NP

 The B3LYP/6-311G(d) and CCSD(T)/6-311G(2df) (single-point) methods have been used to investigate the singlet potential energy surface of C₂NP, in which seven stationary isomers and seventeen interconversion transition states are involved. At the final CCSD(T)/6-311G(2df)//B3LYP6-311G(d) level with zero-point vibrational energy correction the lowest-lying isomer is a linear NCCP followed by two linear CNCP isomers at 23.9  and CCNP at 65.8 kcal mol⁻¹, respectively. The three isomers are kinetically very stable towards both isomerization and dissociation, and CCNP is even more kinetically stable than CNCP – by 14.3 kcal mol⁻¹ despite its high energy. Further comparative calculations were performed at the QCISD and QCISD(T) levels with the 6-311G(d) and 6-311G(2d) basis sets to obtain more reliable structures and spectroscopy for the three isomers. The calculated bond lengths, rotational constant, and dipole moment for NCCP were in close agreement with the experimentally determined values. Finally, similarities and discrepancies between the potential energy surface of C₂NP and those of the analogous species C₂N₂ and C₂P₂ were compared. The results presented in this paper might be helpful for future identification of the two still unknown yet kinetically very stable isomers CNCP and CCNP, both in the laboratory and in interstellar space. Received: 3 January 2001 / Accepted: 6 June 2001 / Published online: 30 October 2001     

Design,synthesis and photoelectrical properties of diphenylamine-containing triphenylamine-based D-D-π-A-type fluorescence dyes

Available online A series of diphenylamine (DPA)-containing triarylamine-based D-D-π-A organic fluorescence dyes were designed under the guidance of theoretical calculations and then synthesized (cyanoacrylic acid, methylene malononitrile or isophorone served as the electron acceptor while ethylene served as the π-bridge). The results of theoretical calculations, electrochemical properties and optical properties tests indicated that the new dyes possessed high thermal stability, desirable HOMO levels and intramolecular charge transfer property. Some of them possessed high fluorescence quantum yields and performed very well as luminescent material as expected..     

两个查尔酮衍生物的合成及超快三阶非线性光学响应

合成了两个二茂铁基查尔酮衍生物:1-二茂铁基-3-(4,5-苯并噻吩-3-基)丙烯酮(FBTAK)和1-二茂铁基-3-(5-苯基噻吩-2-基)丙烯酮(FPTAK),经核磁共振氢谱、碳谱和高分辨质谱对其结构进行表征。采用Z-扫描技术测定了化合物的三阶非线性光学吸收系数(β)、折射系数(n2)和分子超极化率(γ),采用密度泛函理论方法计算了它们的几何结构、分子轨道电子云图和相关能量,同时也测定了其紫外-可见吸收光谱和DSC曲线。FPTAK的分子超极化率(γ)分别是FBTAK、1-二茂铁基-3-(4-叔丁基苯基)丙烯酮(a)和1-二茂铁基-3-联苯基丙烯酮(b)的6. 04倍、4. 3倍和3. 7倍。从构效关系看,苯联噻吩基比苯并噻吩基和联苯基的贡献大,也就是噻吩环比苯环的贡献大。结果表明,电荷转移可以在分子内发生,表现出超快三阶非线性光学响应。     

可充锂电池醌类化合物电极材料

醌类化合物电极材料具有理论比容量高、结构可设计、成本低廉和绿色可持续等优点,被认为是可充锂电池理想的电极材料。本文介绍了醌类化合物电极材料的分类及其结构特点、电化学工作原理及其电化学性能,对醌类化合物的发展、面临的问题等方面进行了概括,探讨了提高该类电极材料电化学性能的方法,并对醌类化合物电极材料的发展方向进行了展望。     

咪唑类化合物在乙腈溶液中负氢解离焓的理论研究

在与实验对照的基础上优化出一套计算咪唑类化合物在乙腈溶液中负氢解离焓的理论方法, 即MP2/6-311++G(d,p)//B3LYP/6-31+G(d)结合IEF-PCM溶剂模型及UA0孔穴计算法. 在此基础上, 有目的地设计了14种咪唑类负氢给体, 并计算了其在乙腈溶液中的负氢解离焓, 系统分析了影响其负氢解离焓的各种因素. 结果表明, 取代基的电子效应、体系释放负氢后的芳构化能力、咪唑环2位的苯基对前线分子轨道的贡献程度、体系电荷的分布情况及溶剂化效应等多种因素均能影响咪唑负氢给体在乙腈溶液中的负氢解离焓.     

Theoretical Study of Rg·NO (Rg=He,Ne, Ar and Kr) Complexes

Rg·NO (Rg=He, Ne, Ar and Kr) complexes were studied using ab initio calculations. The neutral Rg·NO complex geometry and vibrational frequencies were calculated with the cc-pVDZ basis set at the CCSD(T) level of theory. The calculations show that the geometry of the Rg·NO complexes is a skewed T-shape with the Rg atom on the oxygen side of the NO molecule, and that the RgNO bond angle increases with mass. The dissociation energies (DE) and ionization energies (IE) of the neutral Rg·NO complexes, and the dissociation energies of Rg·NO+ ionic complexes were calculated using Gaussian-2 (G2) methods and a high accuracy energy model. The ionization energies of the neutral Rg·NO complexes range from 9.265 eV for He·NO to 9.132 eV for Kr·NO and the dissociation energies of Rg·NO+ range from 0.017 eV for He·NO+ to 0.156 eV for Kr·NO+, in line with the expectation based on the increasing polarizability of the Rg atom.