双氟取代苯和联苯类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法,通过能量梯度全优化计算,给出了对一系列环上双氟取代苯、联苯液晶化合物的稳定几何构型、电子结构和分子基本性质(生成热、偶极矩、前沿分子轨道能级等)。联系有机结构理论进行了分析和讨论。初步阐明了其分子结构与介电各向异性之间的关系,为设计和开发新型液晶分子研究提供了有较大价值的线索。     

高精度保偏光纤偏振测试系统的设计

介绍了保偏光纤的偏振串音和h参数以及它们的相互关系。给出了高精度起偏系统和检偏系统的光路结构。对影响测试精度的各种因素进行了详细分析,并使用自制的测试系统对国内几个单位生产的保偏光纤进行了测试,得到了理想的测试结果。其中,2m长的保偏光纤的偏振串音达到了-50dB以下,其测试精度达到了国际先进水平。     

Quantum Chemical Investigation of Monostanna[n]cyclacenes

Semiempirical molecular orbital treatment at the level of PM3 type calculations has been performed on the Hückel-type monostannacyclacenes having tin atom at the fusion and periposition of arenoid rings. The effect of tin substitution is found to be moderately destabilizing, but it becomes less pronounced in larger systems. The heats of formation values of fusion- and peri-type monostannacyclacenes, in some cases, are more endothermic and, in some cases, less endothermic as compared to the cyclacenes having the same n (the number of arenoid rings) value. The frontier molecular orbital energies, cryptoannulenic effects, geometries, and dipole moments of these structures have also been examined.     

静磁场伴随有静电场存在

阐述检测物体是否产生了电场的方法；通过实际检测证实立方体永磁体既产生了负静电场，也产生了正静电场，并测定了具体的场强．     

Quantum-Chemical Investigation of the Mechanism of Fluorocyclization of Norbornenecarboxylic Acids by the Action of F-TEDA-BF4

Possible paths for the reaction of norbornenecarboxylic acids with model F-TEDA-BF₄ were studied by the semiempirical PM3 method. The activation energies of the main transformations in the initial reagents and intermediates were determined. Conclusions were reached about the effect of their reaction mechanisms on the distribution of the products.     

Crystal structure of a butyllithium 1,2-dipiperidinoethane dimer complex

The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane as a centrosymmetric dimer in the monoclinic space group P2₁/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6 has a planar central Li₂C₂ core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified three structural motifs that affect Li₂C₂ dimer ring planarity.     

Application of receptor models to airborne particulate matter

The human activities in their various aspects cause a change in the natural air quality. This change results more marked in very populated and in high industrialized areas. Some pollutants emitted are typical of a particular activity. Each source of pollution is identified by its profile in the composition of the emissions in the environment. Multivariate receptor models can be used in order to apportion pollutants to the different sources assessing the contribution of each source to the total pollution.This paper deals with the application of Absolute Principal Component Scores (APCS) receptor model to data obtained from the automatic network of air quality monitoring in the city of Bari (South Italy). The parameters monitored by automatic networks, as bihourly values, are PM₁₀, NO_x, CO, Benzene, Toluene, Xilene. The data shown in this paper concerning 1 month almost of sampling in different monitoring stations of Bari Municipality during the period of time from January 2005 to April 2006. Moreover preliminary results obtained applying the APCS model to daily PM_2.5 samples collected during SITECOS PRIN project are shown. The results concerning data collected in corso Cavour (Bari) during the month of October 2005.The results obtained by APCS receptor model seem to suggest a poor contribution of the “vehicular traffic source” and a relevant contribution of the “secondary particulate source” to particulate matter concentrations.     

A Chain Structure Based on Homodinuclear Scandium Units: [Sc(μ-OH)(2,5-pydc)(H2O)]n

The reaction of pyridine-2,5-dicarboxylic acid with Sc2O3 under hydrothermal con-dition yields a new complex [Sc(μ-OH)(2,5-pydc)(H2P)]n 1 which has a chain structure based on homodinuclear scandium units. Crystal data for 1: space group P1, a = 6.7192(13), b = 7.6131(13),c= 8.9313(14) A, α = 95.976(6), β = 101.663(6),γ,= 108.151(5)°, V = 418.26(13) A3, Z = 2, Dc =1.946 g/cm3,μ = 0.889 mm-1, F(000) = 248, C7H6NO6Sc, M, = 245.09, the final R = 0.0429 and wR = 0.1086.