Theoretical investigation on the optical absorption spectra and local lattice structure of α-Al2O3:Yb crystals

In this paper, the optical absorption spectra of Yb³⁺ in the α-Al₂O₃ crystal are reasonably explained by using the superposition model and local lattice structure analysis. Based on these studies, we find that the local geometrical structure around the Yb³⁺ ions possesses an elongated trigonal distortion above the O²⁻-triangle and a compressed trigonal distortion in the lower one.     

PuO2和α-Pu2O3光学性质的经验势模拟

用GULP程序拟合出α-Pu₂O₃的Pu-O作用BMH经验势参数.结合氧离子壳模型势,运用分子静力学和动力学计算出PuO₂和α-Pu₂O₃理想晶体的结构参数和光学性质.结果显示：它们的空间群、晶胞参数、密度和熵等,与文献报道值接近,相对误差均小于1.2%;并计算出PuO₂和α-Pu₂O₃的高频和静态介电张量、红外介电函数谱、晶格振动 关键词： 2')" href="#">PuO₂ 2O₃')" href="#">α-Pu₂O₃ 光学性质     

5-烷氧基-3,4-二卤-2(5H)-呋喃酮与α,ω-二胺的串联反应

在三乙胺作用下, 亲核试剂α,ω-二胺与5-烷氧基-3,4-二卤-2(5H)-呋喃酮在室温下发生串联的迈克尔加成-消除反应, 合成了16个新化合物. 通过旋光度, UV-Vis, IR, 1H NMR, 13C NMR, MS, 元素分析和X射线单晶衍射等表征方法, 确定了目标化合物的化学结构和绝对构型.     

Stereoselective Synthesis and Crystal Structure Analysis of N-Naphthyl-2-deoxy-α-D-ribopyranosylamine

A new compound N-naphthyl-2-deoxy-α-D-ribopyranosylamine was synthesized and structurally determined. It crystallizes in the orthorhombic system, space group P212121 with a = 8.361（2）, b = 12.432（3）, c = 12.791（4） A^°, Z= 4, V= 1329.6（6） A^°^3, Dc= 1.295 g/cm^3, F（000） = 552, Cl5H17NO3 and Mr= 259.30. All the active hydrogen atoms are involved in the formation of hydrogen bonds in the molecule.     

First-principles study of the electronic structures of α-rhombohedral boron codoped with lithium and oxygen

α-Rhombohedral (α-rh) boron, which is the most stable of boron's polymorphs at low temperatures, has p-type semiconductive properties. There have been some attempts to dope the interstitial sites with alkali atoms to create metallic or n-type semiconductive α-rh boron, but this has yet to be achieved. In a previous work, we proposed the codoping of α-rh boron with Li and P or As, and revealed from first principles calculations that B₁₂PLi and B₁₂AsLi could be synthesized and become narrow-gap semiconductors. The band structure suggested that the mobility of electrons might be greater than that of holes. In this paper, based on these prospective results, we selected a new combination of dopants, Li and O, and theoretically studied such compounds as B₁₂OLi and B₁₂O₂Li. The results showed that both of these materials are metallic, while the reaction energies of the Li insertion into B₁₂O and B₁₂O₂ are lower (more unstable) than with B₁₂PLi and B₁₂AsLi. It was proved that the differences in the electronic structures are caused by the dangling bonds of the dopant atoms, O, P and As.     

A twofold interpenetrating framework based on the α-metatungstates

A new compound based on polyoxometalates, [Cu(bbi)]₅H[H₂W₁₂O₄₀] (1) (bbi=1,1′-(1,4-butanediyl)bis(imidazole)), has been hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and single X-ray diffraction. Compound 1 shows a twofold 3D+3D topology, and it represents the first interpenetrating network based on the isopolytungstate. The electrochemical property of compound 1 modified carbon paste electrode (1−CPE) was investigated in 1 M H₂SO₄ solution, and the results indicate that 1−CPE exhibits the electrocatalytic activity toward the reduction of bromate and nitrite. Further, the non-isothermal kinetics of the thermal decomposition of compound 1 provides the dynamic parameters E (activation energy) and A (pre-exponential factor) for the pyrolytic reaction of the organic ligands.     

α-Trifluoromethyl-β-aryl enamines in the synthesis of trifluoromethylated heterocycles by the Fischer and the Pictet-Spengler reactions

α-Trifluoromethyl-β-aryl enamines were successfully used as synthetic equivalents of benzyltrifluoromethyl ketones in both the Fischer indole synthesis and the Pictet-Spengler reaction. Accordingly, 2-trifluoromethyl indoles and a variety of trifluoromethylated 4,5,6,7-terahydro-1H-pyridines including carbolines were synthesized in moderate to good yields.     

Reaction of 1-substituted 3-aminoquinoline-2,4-diones with isothiocyanates. An easy pathway to generate novel 2-thioxo-1′H-spiro[imidazoline-5,3′-indole]-2,2′-diones

3-Butyl-3-amino-1H,3H-quinoline-2,4-diones react with isothiocyanates to give novel 3a-butyl-9b-hydroxy-2-thioxo-1,2,3,3a,5,9b-hexahydro-imidazo[4,5-c]quinolin-2-ones in high yields. These compounds rearrange in boiling acetic acid or concd hydrochloric acid to give (E)- and/or (Z)-4-butylidene-2-thioxo-1′H-spiro[imidazoline-5,3′-indole]-2,2′-diones. All compounds were characterized by their ¹H, ¹³C, IR and MS spectra, and some of them also by ¹⁵N NMR. The structure of one compound was investigated by single-crystal X-ray diffraction.     

Stereoselective synthesis of N-heterocycles: application of the asymmetric Cu-catalyzed addition of Et2Zn to functionalized alkyl and aryl imines

The preparation of N-heterocycles from alkyl- and aryl-substituted imines is described. The key step involves a copper-catalyzed addition of diethylzinc to functionalized alkyl-substituted imines that were generated in situ from the sulfinic acid adducts. The nucleophilic addition products were then converted to 2-substituted pyrrolidines and piperidines. Aryl-substituted imines were transformed into enantioenriched 1- and 1,4-substituted tetrahydroisoquinolines.     

Spectrofluorimetric method for measuring the activity of the enzyme α-l-fucosidase using the ion associate of 2-chloro-4-nitro phenol-rhodamine-B

A low cost and accurate method for the detection and analytical determination of the activity of the enzyme α-l-fucosidase (AFU) was developed. The method was based upon measuring the fluorescence intensity of the complex ion associate of the ion associate of rhodamine-B and the compound 2-chloro-4-nitrophenol (RB⁺ CNP⁻) at 580 nm in phosphate buffer (pH 5) against the reagent blank. The influence of the different parameters, e.g. pH, incubation time, temperature, 2-chloro-4-nitrophenol concentration, foreign ions and surfactants that control the fluorescence intensity of the produced ion associate was critically investigated. The correlation between the fluorescence activity of the enzyme AFU by the developed procedures and the standard method was positive and highly significant in patients and controls (r² = 0.99, p < 0.001). The developed method is simple and proceeds without practical artifacts compared to the standard method.