Synthesis, structural characterization and ferrimagnetic property of MnPS3 intercalated with nickel(II) cyclopolyamine complex cations

Two new intercalation compounds were prepared by the reactions of Ni(II) cyclopolyamine complex cations with a preintercalate Mn_1−xPS₃K_2x(H₂O)_y, respectively, through “ion exchange” process. Their structures were characterized by elemental analysis, X-ray powder diffraction and infrared spectroscopy. The lattice spacing increased 0.567 and 1.093 nm with respect to the pristine MnPS₃. Ferrimagnetism of the intercalates was confirmed by SQUID experiment with T_c at 40 and 33 K, respectively.     

1,4-双(4''''-溴苯酰基)苯的合成工艺改进

以对苯二甲酰氯和溴苯为原料,无水氯化铝粉末为催化剂,合成了1,4-双(4'-溴苯酰基)苯,其结构经1H NMR,IR和DSC表征.     

钯镁基体改进剂对铅,铋,锗在石墨炉中原子化影响的研究

通过原子吸收和X-射线衍射分析证明,加入钯镁基体改进剂在预热处理后对Pb、Bi和Ge三个元素分别生成金属间化合物PbPd_3、BiPd_3、Ge_9Pd_(23)和其他化合物,从而提高了最高允许灰化温度,改变了原子化机理。在原子化阶段这些金属间化合物直接分解为金属原子,结果提高测定灵敏度。     

Thermodynamics and kinetics of the hydride-transfer cycles for 1-aryl-1,4-dihydronicotinamide and its 1,2-dihydroisomer

Five 1-(p-substituted phenyl)-1,4-dihydronicotinamides (GPNAH-1,4-H(2)) and five 1-(p-substituted phenyl)-1,2-dihydronicotinamides (GPNAH-1,2-H(2)) were synthesized, which were used to mimic NAD(P)H coenzyme and its 1,2-dihydroisomer reductions, respectively. When the 1,4-dihydropyridine (GPNAH-1,4-H(2)) and the 1,2-dihydroisomer (GPNAH-1,2-H(2)) were treated with p-trifluoromethylbenzylidenemalononitrile (S) as a hydride acceptor, both reactions gave the same products: pyridinium derivative (GPNA(+)) and carbanion SH(-) by a hydride one-step transfer. Thermodynamic analysis on the two reactions shows that the hydride transfer from the 1,2-dihydropyridine is much more favorable than the hydride transfer from the corresponding 1,4-dihydroisomer, but the kinetic examination displays that the former reaction is remarkably slower than the latter reaction, which is mainly due to much more negative activation entropy for the former reaction. When the formed pyridinium derivative (GPNA(+)) was treated with SH(-), the major reduced product was the corresponding 1,4-dihydropyridine along with a trace of the 1,2-dihydroisomer. Thermodynamic and kinetic analyses on the hydride transfer from SH(-) to GPNA(+) all suggest that the 4-position on the pyridinium ring in GPNA(+) is much easier to accept the hydride than the 2-position, which indicates that when the 1,4-dihydropyridine is used the hydride donor to react with S, the formed pyridinium derivative GPNA(+) may return to the 1,4-dihydropyridine by a hydride transfer cycle; but when the 1,2-dihydropyridine is used as the hydride donor, the formed pyridinium derivative can not return to the 1,2-dihydropyridine by the hydride reverse transfer from SH(-) to GPNA(+). These results clearly show that the hydride-transfer cycle is favorable for the 1,4-dihydronicotinamides, but unfavorable for the corresponding 1,2-dihydroisomers.     

Determination and Differentiation of Two Seemingly Identical Medicinal Herbs by Capillary Electrophoresis with Electrochemical Detection

A high-performance capillary electrophoresis with electrochemical detection (CE-ED) method has been employed for the determination of six bioactive ingredients in traditional Chinese herbs, Herba cepbalanoplosis segeti and Herba cirsii japonici. The effects of several factors such as the acidity and concentration of running buffer, the separation voltage, the applied potential and the injection time on CE-ED were investigated. Under the optimum conditions, the six analytes could be well separated within 21 min in a 75 cm length capillary at the separation voltage of 15 kV in a 50 mmol L^–1 borax running buffer (pH 8.4). A 300 m diameter carbon disk electrode was used as the working electrode positioned carefully opposite the outlet of the capillary in a wall-jet configuration at potential of +950 mV (vs. SCE). Good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits (S/N=3) ranged from 1.5×10^–7 to 6.0×10^–7 g mL^–1 for all six analytes. This proposed method has been successfully applied for the analysis of traditional Chinese herbs after a relatively simple extraction procedure, further on, for the differentiation of these above two seemingly identical herbs based on their electropherograms or characteristic electrochemical profiles.     

Self-complementary

Three [3]catenanes with cavities large enough to accommodate aromatic guests have been designed and synthesized (yields = 5-20 %) by means of kinetically controlled self-assembly processes. The X-ray structural analysis of one of three [3]catenanes confirmed the presence of a rectangular cavity (dimensions = 7 x 11 A) lined by pi-electron-rich recognition sites and hydrogen-bond acceptor groups. In spite of their apparently ideal recognition features, none of these [3]catenanes bind guests incorporating a pi-electron-deficient bipyridinium unit. However, the template-directed syntheses of the [3]catenanes also produce, in yields of 2-23%, [2]catenanes incorporating a 1,5-dioxynaphtho[38]crown-10 interlocked with a bipyridinium-based tetracationic cyclophane. The X-ray structural analyses of two of these [2]catenanes revealed that a combination of [pi...pi] and [C-H...pi] interactions is responsible for the formation of supramolecular homodimers in the solid state. 1H NMR spectroscopic investigations of the four [2]catenanes demonstrated that supramolecular homodimers are also formed (Ka= 17-31M(-1), T= 185 K) in (CD3)2CO solutions. Dynamic 1H NMR spectroscopy revealed that the 1,5-dioxynaphtho[38]crown-10 and tetracationic cyclophane components in the four [2]catenanes and in the three [3]catenanes circumrotate (deltaGc(not equal to) = 9-14 kcal mol(-1)) through each other's cavity in (CD3)2CO. Similarly, the 1,5-dioxynaphthalene and the bipyridinium ring systems rotate (deltaGc(not equal to) =10-14 kcal mol(-1)) about their [O...O] and [N...N] axes, respectively, in solution.     

Acid properties of semicrystalline zeolitic mesoporous UL-ZSM-5 materials

UL-ZSM-5 materials have been prepared by templated solid-state crystallization of zeolites starting from the amorphous mesostructured aluminosilicate Al-Meso. Microcalorimetry and FTIR have been employed to characterize their surface acidity. In good agreement with ²⁷Al MAS NMR data, UL-ZSM-5 displayed an improved density and strength of Brönsted acid sites, as compared to Al-Meso, owing to the incorporation of aluminium in a tetrahedral environment similar to that of zeolite ZSM-5. Moreover, they showed an enhanced Brönsted/Lewis relative acid ratio. However, Al-Meso showed the highest concentration of strong Lewis acid sites due to its largest amount of aluminium in extraframework positions.     

Design and fabrication of 2 kHz nematic liquid crystal variable retarder with reflection mode

ABSTRACT

This study proposes a simple method of designing a high-speed liquid crystal variable retarder (LCVR) with reflection mode. First, a series of simple formulas is provided for analysing the effects of tilt incidence and birefringence of the liquid crystal on the phase retardation and response time of the LCVR. Then, a reflective LCVR is fabricated to validate the theoretical analysis. Measured results show that the response speed can reach 2.7 kHz with a phase retardation of 1 λ. Furthermore, the theoretical curve is close to the measured curve while the incident angle is less than 10°. However, the theoretical and measured values show a considerable difference under a large incident angle. This problem is discussed, and a modified method is given. This work is helpful for the design and fabrication of high-speed LCVR.     

Determination of rare earth impurities in high purity gadolinium oxide by inductively coupled plasma mass spectrometry after 2-ethylhexylhydrogen-ethylhexy phosphonate extraction chromatographic separation

A method was developed for the determination of rare earth impurities in high purity Gd(2)O(3) by inductively coupled plasma mass spectrometry (ICP-MS). The matrix suppression effect of Gd(2)O(3) on signals of rare earth impurities was compensated for by Re internal standardization. The spectra overlap interferences from GdH, GdO, GdOH(n) (n=1-3) on Tb, Tm, Yb and Lu were eliminated by 2-thylhexylhydrogen-2-ethylhexy phosphonate (EHEHP) extraction chromatographic separation. The detection limits for REEs were 0.005-0.017 ng ml(-1) in solution and 0.002-0.05 mug g(-1) in solid. Recoveries of spiked sample for REEs were from 88 to 121% with the precision of 1.0-7.5% RSD. Determination of trace REEs in two Gd(2)O(3) samples were performed. The method can be applied to analysis of 99.99-99.9999% high purity Gd(2)O(3).     

苯、甲苯、一氯代苯对含水卵磷脂液晶结构影响的SAXS研究

苯及其衍生物甲苯,一氯代苯都是重要的有机试剂和化工原料,也是对人体有害的有机物。为了了解这些有机试剂对处于生物液晶态的生物膜毒害的机理,我们以含水卵磷脂组成的液晶体系作为人工模型用小角X射线散射(SAXS)方法探讨这些有机试剂对它们结构的影响。关于苯或其它非极性有机介质与含水卵磷脂形成液晶体系及其结构模型前人有一些报导。