Synthesis of (4R,15R,16R,21S)- and (4R,15S,16S,21S)-rollicosin

A convergent synthesis of (4R,15R,16R,21S)-rollicosin (1) and (4R,15S,16S,21S)-rollicosin (2) was accomplished. Hydroxy lactone 6a and/or 6b were synthesized from 4-pentyn-1-ol, and α,β-unsaturated lactone 7 was synthesized from γ-lactone 8 and 5-hexen-1-ol. Inhibitory activity of these compounds was examined with bovine heart mitochondrial complex I.     

Sialylation reactions with N,N-acetyl, benzoyl-O-perbenzoyl-protected sialyl donor

A new sialyl donor, N,N-acetyl, benzoyl-O-perbenzoyl-protected p-toluenethiosialoside, was synthesized and its sialylation reaction was investigated. This reaction proceeded in dichloromethane and β anomeric selectivity was achieved when NIS-TfOH was used as promoter. This method may be employed to construct the unnatural β-linked sialosides.     

Conformational and thermodynamic studies of alkaline subhalides M2X (M = Li, Na, K, Rb; X = F, Cl, Br, I)

Alkaline subhalides M₂X (M = Li, Na, K, Rb; X = F, Cl, Br, I) were investigated using DMol software combined with thermostatistical techniques to obtain thermodynamic data for studying the stability of these subhalides. Validation of these results was checked by establishing a link with the experimental MX-M phase diagrams by a simple empirical relation.     

cis,cis,cis,cis-1,2,3,4,5-Pentakis(hydroxymethyl)cyclopentane

All-cis pentamethanolcyclopentane has been obtained in six steps by Diels–Alder condensation of maleic anhydride with (benzyloxymethyl)cyclopenta-2,4-diene, reduction of the anhydride to a diol that was protected as the acetonide. Then, ozonolysis of the double bond, followed by reduction led to a cis-diol. Then successive deprotections of the three other methanol groups gave the cis,cis,cis,cis-1,2,3,4,5-pentakis(hydroxymethyl)cyclopentane.     

Ionization gauge sensitivities of N2, O2, N2O, NO, NO2, NH3, CClF3 and CH3OH

A Bayard-Alpert (BA) gauge was used to determine apparent relative sensitivites S_rel,X for O₂, N₂O, NO, NO₂, NH₃, CClF₃ and CH₃OH from gauge calibration measurements in the range 1.3×10^–1 Pap1.3·10^–3Pa. Nitrogen was used as a calibration standard.     

多晶GeSe薄膜的制备及在太阳能电池中的应用

硒化亚锗(GeSe)由于具有原材料储量丰富、绿色无毒、组成简单、稳定以及吸光系数高等优势,很适合被用于制备薄膜太阳能电池的光吸收层。然而,目前对其研究较少,其主要难点在于如何制备高质量的多晶GeSe薄膜。本工作采用物理气相沉积法制备GeSe薄膜,之后通过硫化铵溶液及退火处理,有效地将非晶GeSe转变为多晶GeSe。将其组装成简单平面薄膜结构太阳能电池器件后,相比于未处理的非晶GeSe太阳能电池,电池的光电流有了显著提升,对应的电池效率提升了13倍左右。进一步将未封装的电池放置在空气中一个月后,发现其仍能保持原有效率,证明其具有优异的稳定性。     

Structural chemistry and magnetic behavior of ternary gallides REAuxGa4−x, RE = La, Ce, Pr, Nd, and Sm

Two new series of ternary gallides with the chemical formulas (La, Ce, Pr, Nd, Sm)Au_xGa_4−x and (La, Ce, Pr, Nd, Sm)Au_1.5Ga_2.5 were synthesized from the elements by arc melting. From X-ray powder diffraction analysis the REAu_xGa_4−x series of compounds was found to be isotypic and crystallize with BaAl₄ type of structure; the homogeneity range at 600°C of each of the REAu_xGa_4−x phases was established, revealing remarkable deviations from Vegard's rule. At 600°C the REAu_xGa_4−x phases of the BaAl₄ type were observed to be in thermodynamic equilibrium with a structure variant crystallizing at the composition REAu_1.5Ga_2.5 and with a narrow homogeneous range. In case of PrAu_1.5Ga_2.5 the structure type was refined from X-ray single-crystal counter data (CaBe₂Ge₂ type, space group P4/nmm, R_w = 0.046). Gold and gallium atoms were generally found on separate crystallographic sites; however, a statistical distribution of 51% Au + 49% Ga was derived for the 2b sites. ¹⁹⁷Au Mössbauer spectroscopy confirmed the occupational mode of the gold atoms in CeAu_1.5Ga_2.5. For the BaAl₄-type phases, X-ray powder and Mössbauer data revealed preferential occupation of the 4e sites of I4/mmm by gold atoms; practically no Au was observed on the 4d sites. Magnetic susceptibilities were determined over a temperature range extending from 2 to 1100 K. Above liquid nitrogen temperatures the paramagnetic behavior of the (Ce, Pr, Nd)Au_xGa_4−x and the (Ce, Pr, Nd)Au_1.5Ga_2.5 compounds is characterized by magnetic moments close to the ideal trivalent rare earth values. Lanthanum compounds are diamagnetic, whereas SmAu_xGa_4−x alloys are characterized by a typical Van Vleck-type paramagnetism of closely spaced multiplets. At very low temperatures onset of ferromagnetic ordering is observed for the BaAl₄-type series of compounds. No superconductivity was encountered down to 2 K.     

Synthesis, structures, physicochemical properties, and crystal-chemical systematics of M 2II AIIUO6 (MII = Pb, Ba, Sr; AII = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb) compounds

Pb₂A^IIUO₆ (A^II = Mg, Ca, Sr, Ni, Zn, Cd) compounds were synthesized by high-temperature reactions in the solid phase. For the Pb₂MgUO₆, Pb₂CaUO₆, and Pb₂CdUO₆ compounds, the crystal structures (space group P2₁/n) were refined by the Rietveld method. It was demonstrated that these structures belong to the perovskite structure type. Crystal-chemical systematics was performed for all synthesized perovskites. High-temperature X-ray diffraction and differential scanning calorimetry were used to study the thermal stability and phase transitions, determine the thermal expansion coefficients, and elucidate the effect of atoms located in octahedral and cuboctahedral positions on the heating behavior of the structure. The standard enthalpies of formation of the Pb₂A^IIUO₆ compounds were determined by reaction calorimetry.     

P(VAc-MMA)为基体的聚合物电解质研究

以醋酸乙烯酯(VAc)和甲基丙烯酸甲酯(MMA)为单体, 采用半连续种子乳液聚合法制备了无规共聚物聚(醋酸乙烯酯-甲基丙烯酸甲酯)[P(VAc-MMA)], 并以此聚合物为基体制备了聚合物电解质. 用红外光谱(FTIR)、核磁共振氢谱(¹H NMR)、扫描电镜(SEM)、差热/热重分析(DSC/TG)、X射线衍射(XRD)、机械性能测试和电化学交流阻抗等方法对聚合物和聚合物电解质的性质进行了研究. 测试结果表明: VAc和MMA聚合生成P(VAc-MMA); 聚合物膜含有大量微孔结构, 利于离子传输; 聚合物电解质膜具有优良的热稳定性和机械强度; 25 ℃下, 最高的离子电导率达到了1.27× 10^－3 S•cm^－1; 离子电导率随着温度的升高而迅速增加, 电导率-温度曲线符合Arrhenius方程.     

Archaeological wood characterisation by PY/GC/MS, GC/MS, NMR and GPC techniques

The chemical characterisation of waterlogged archaeological wood is of paramount importance in terms of understanding not only the degradation processes of wood in artistic and archaeological objects but also the development of consolidation and conservation procedures. The two different types of archaeological waterlogged wood were characterized using several analytical techniques. The analytical protocol consists in using PY/GC/MS with in situ derivatisation with hexamethyldisilazane, GC/MS of the extractives, ¹H, ¹³C and ³¹P NMR analysis, and GPC. The main results showed that one of the ancient samples was a gymnosperm wood from the Pinaceae family, whereas the other type of wood was an angiosperm. Lignin from the angiosperm was oxidised in a benzylic position of β-O-4 to give oxo functional groups, in primary alcohol moiety to give carboxylic groups. In addition, the formation of a new intermonomeric bond 5-O-4 was observed.     

Isomerization and ring-closing metathesis for the synthesis of 6-, 7- and 8-membered benzo- and pyrido-fused N,N-, N,O- and N,S-heterocycles

An isomerization-ring-closing metathesis (RCM) strategy afforded N-substituted 4H-1,4-benzoxazines from the protected N-allyl-2-(allyloxy)anilines. In addition, RCM was used to synthesize the N-substituted, 8-membered benzo-fused heterocycles from the respective diallyl compounds: 1,2,5,6-tetrahydro-1,6-benzodiazocine, 5,6-dihydro-2H-1,6-benzoxazocine, 5,6,9,10-tetrahydropyrido[2,3-b][1,4]diazocine and 5,6-dihydro-2H-1,6-benzothiazocine 1,1-dioxide. The isomerization-RCM approach also afforded the 7-membered ring system, 2,5-dihydro-1,5-benzothiazepine 1,1-dioxide, from the protected N-allyl-2-(allylsulfonyl)aniline. Furthermore, the structure of 1,6-bis[(4-methylphenyl)sulfonyl]-1,2,5,6-tetrahydro-1,6-benzodiazocine was confirmed by a single crystal X-ray determination.     

Preparation, crystal structure, and superconductive characteristics of new oxynitrides (Nb1−xMx)(N1−yOy) where M=Mg, Si, and x≈y

New niobium oxynitrides containing either magnesium or silicon were prepared at 1000 °C by ammonia nitridation of oxide precursors obtained via the citrate route. The products had rock-salt type crystal structures. Crystallinity was improved by annealing in 0.5 MPa N₂ and the final compositions were (Nb_0.95Mg_0.05)(N_0.92O_0.08) at 1500 °C and (Nb_0.87Si_0.09□_0.04)(N_0.87O_0.13) at 1200 °C. The magnesium and oxide ions partially co-substitute the niobium and nitride ions in the octahedral sites of the δ-NbN lattice, respectively. Silicon ions were also successfully doped together with oxide ions into the rock-salt type NbN lattice. The Si doped product exhibited relatively large displacement at the octahedral sites and was accompanied by a small amount of cation vacancies. Superconductivity was improved by annealing to obtain critical temperatures/volume fractions of T_c=17.6 K/100% for Mg- and T_c=16.2 K/95% for the Si-doped niobium oxynitrides.     

Synthesis of 2E,4E,6E,11Z-octadecatetraenoic acid of the Rhizobium leguminosarum biovar viciae Nod factor

2E,4E,6E,11Z-Octadecatetraenoic acid was synthesized in a good yield and in a stereospecific manner by coupling a vinylborane compound and ethyl trans-3-iodoacrylate. The trienic system (E,E,E) was obtained by successive use of metal-catalyzed coupling and hydro-metallation reactions.     

Polysiloxane xerogels with a bifunctional surface layer containing O/N, O/S, S/N, and S/S donor centers

Formation of bifunctional xerogels containing -NH₂, -SH, -P(O)(OEt)₂, and -NHP(O,S)(OEt)₂ complexing groups in the surface layer was studied using sol-gel method (fluoride ion catalyst, ethanol solvent) and three-component systems.     

(6Z,9Z,12Z)-6,9,12-Octadecatriene and (3Z,6Z,9Z,12Z)-3,6,9,12-icosatetraene, the novel sex pheromones produced by emerald moths

(6Z,9Z,12Z)-6,9,12-Octadecatriene and (3Z,6Z,9Z,12Z)-3,6,9,12-icosatetraene, hydrocarbons unsaturated more highly than usual lepidopteran Type II pheromones, were identified from geometrid females of Hemithea tritonaria and Thalassodes immissaria intaminata, respectively. The triene was synthesized by a double Wittig reaction between hexanal and an ylide derived from (Z)-1,6-diiodo-3-hexene, and the tetraene was synthesized by a coupling between (Z)-3-undecenal and an ylide derived from (3Z,6Z)-1-iodo-3,6-nonadiene. Each synthetic compound attracted males of the corresponding emerald moths in a field.     

FT-Raman Spectra of o-, m-, and p-Nitrophenol Included in Cyclodextrins

FT-Raman spectra of o-, m-, and p-nitrophenol included in -cyclodextrin (CD), -CD, hydroxypropyl (HP) -CD, andsulfated -CD were recorded. The phenyl (C=C) band of o- and p-nitrophenol in the CD inclusion complexes was shifted to higher wavenumber thanthat of pure o- and p-nitrophenol,whereas the phenyl (C=C) band of m-nitrophenol in the CD inclusion complexes was shifted to lower wavenumber than that of pure m-nitrophenol. The ring CH peak of o-nitrophenol in the CD complexes was shifted to higher wavenumber than that of pure o-nitrophenol, whereas the ring CH peak of m- and p-nitrophenol in the CD complexes was shifted to lower wavenumber than that of pure m- and p-nitrophenol.     

SiO2/TiO2-xCx/C的制备、表征及其吸附和可见光催化性能

以SiO2为成核中心,钛酸四丁酯为钛源,分别以多羟基化合物乙二醇、丙三醇、葡萄糖和聚乙烯醇为联接剂,采用水解沉淀法制备了碳掺杂和包覆的多孔SiO2/TiO2-xCx/C可见光响应型光催化剂。采用X-射线衍射(XRD)、透射电子显微镜(TEM)、X-射线光电子能谱(XPS)、傅里叶变换-红外光谱(FTIR)、比表面积(BET)和紫外-可见(UV-Vis)漫反射光谱对样品进行表征。对不同结构样品的形成机理进行了分析。以次甲基蓝(MB)溶液为模拟废水,对样品的吸附性能和可见光催化性能进行了评价。结果表明,多羟基化合物对材料的结构和性能有重要影响。碳的掺杂和包覆使材料的吸收光谱包含了整个可见光区,而多孔结构使材料的吸附性能得到提高。以聚乙烯醇为原料所得样品吸附性能最好,30 min内吸附率达到70%;而以丙三醇为原料所得样品具有最好的可见光催化性能,40 min内次甲基蓝的降解率达到95%。     

Fluorite-related phases Ln3MO7, Ln = rare earth,Y, or Sc, M = Nb,Sb, or Ta. I. Crystal chemistry

Compounds Ln₃MO₇, where Ln = La, Nd, Gd, Ho, Er, Y, or Sc, and M = Nb, Ta, or Sb have been examined by powder X-ray diffraction, electron diffraction, and electron microscopy. For large Ln cations, an orthorhombic fluorite-related superstructure is formed, of probable space group Cmcm for Ln = La and C222₁ for Ln = Nd, Gd, Ho, or Y, while for the smaller Ln cations, Er, and under some conditions, Ho and Y, the structure is defect fluorite containing microdomains of ordered, but undetermined, structure. The composition Sc₃MO₇ was not single phase under the conditions used. Compounds of the type Ln₂ScMO₇ have the pyrochlore structure.     

Preparation, thermal properties, morphology, and microstructure of phosphorus-containing epoxy/SiO2 and polyimide/SiO2 nanocomposites

A phosphorus-containing tri-ethoxysilane (dopo-icteos) reacting from the nucleophilic addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (dopo) and 3-(trieoxysilyl) isocyanate (icteos) was synthesized. The structure of dopo-icteos was confirmed by ¹H, ¹³C, ³¹P NMR and IR spectra. A triethylamine catalyzed mechanism for the dopo-icteos synthesis was proposed and verified by NMR spectra. The phosphorus-containing epoxy/SiO₂ and polyimide/SiO₂ nanocomposites were prepared from the in-situ curing of diglycidyl ether of bisphenol A (DGEBA)/4,4-diaminodiphenylmethane(DDM)/dopo-icteos, and imidization of poly(amic acid) of pyromellitic dianhydride (PMDA)/4,4′-oxydianiline (ODA)/dopo-icteos, respectively. The microstructure and morphology were investigated by ²⁹Si NMR, scanning electron microscope (SEM), EDS (Si and P mapping) analysis and atomic force microscope (AFM). The thermal properties, flame retardancy and dielectric properties of the organic-inorganic hybrids were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), limiting oxygen index (LOI), thermal gravimetric analysis (TGA) and dielectric analyzer (DEA).     

Ab Initio calculation of molecular, thermodynamic, and kinetic parameters of CF, CF2, CF3, and C2F5 radicals and CF4, CF3I, C2F4, and C2F6 molecules in gas

Enthalpies of formation of ground states of the gaseous particles CF, CF₂, C₂F₅, CF₄, CF₃I, C₂F₄, and C₂F₆ were calculated by ab initio method in the CCSD(T) approximation with extrapolation to the full basis and regard to the correlation energy. Their equilibrium geometrics, frequencies of normal vibrations, and other values were found by the B3LYP/aug-cc-pvdz method, from which thermodynamic functions within the range of 0–6000 K were calculated. Equilibrium constants were calculated from these functions, and then the information on the rate constants in the limit of high pressures was obtained.