Enantioselective total synthesis of (-)-heliannuol A

An efficient and enantiocontrolled total synthesis of (-)-heliannuol A has been accomplished by employing ring closing metathesis and sequential diastereoselective epoxidation and regioselective reductive cleavage of the epoxide ring.     

Molecular structures of propene and 3,3,3-trifluoropropene determined by gas electron diffraction

The structures of propene and 3,3,3-trifluoropropene have been studied by electron diffraction intensities measured in the present study and rotational constants reported in the literature. The following average structures have been determined: For propene, r_g(CC) = 1.342 ± 0.002 Å, r_g(C-C) = 1.506 ± 0.003 Å, r_g(C-H)_vinyl = 1.104 ± 0.010 Å, r_g(C-H)_methyl = 1.117 ± 0.008 Å, ∠(C-CC) = 124.3 ± 0.4°, ∠(CC-H) = 121.3 ± 1.4°, and ∠(C-C-H) = 110.7 ± 0.9°; for trifluoropropene, r_g(CC) = 1.318 ± 0.008 Å, r_g(C-C) = 1.495 ± 0.006 Å, r_g(C-H)= 1.100 ± 0.018 Å, r_g(C-F) = 1.347 ± 0.003 Å, ∠(C-CC) = 125.8 + 1.1°, ∠(C-C-F) = 112.0 ± 0.2°, where the valence angles refer to the r_av structure, and the uncertainties represent estimated limits of experimental error. A simple set of quadratic force constants for each molecule has been estimated. Regular trends have been observed in the CC and C-C bond distances and the C-CC angles in these and related molecules. Significant differences between the CC, C-C and C-F distances and the C-C-F angle in trifluoropropene and in hexafluoroisobutene reported by Hilderbrandt et al. have been indicated.     

Molecular rotor of Cs2([18]crown-6)3 in the solid state coupled with the magnetism of [Ni(dmit)2

Nanoscale molecular rotors that can be driven in the solid state have been realized in Cs2([18]crown-6)3[Ni(dmit)2]2 crystals. To provide interactions between the molecular motion of the rotor and the electronic system, [Ni(dmit)2]- ions, which bear one S=1/2 spin on each molecule, were introduced into the crystal. Rotation of the [18]crown-6 molecules within a Cs2([18]crown-6)3 supramolecule above 220 K was confirmed using X-ray diffraction, NMR, and specific heat measurements. Strong correlations were observed between the magnetic behavior of the [Ni(dmit)2]- ions and molecular rotation. Furthermore, braking of the molecular rotation within the crystal was achieved by the application of hydrostatic pressure.     

Identification of oxidation states of metal oxides by MALDI-TOF MS

For the detection of inorganic species, we have developed chemical reaction laser desorption ionization mass spectrometry, and applied it to the analysis of metal oxides in different oxidation states. Metal oxide species insoluble in common organic solvents were finely grounded in a mortar and suspended in a solvent. The turbid suspension was placed on a sample holder on which a suitable chelating reagent had been previously spotted in a similar manner for sample preparation employed in the matrix-assisted laser desorption mass spectrometry (MALDI-MS). By using this method, the mass spectra of manganese (II and IV) oxides (MnO and MnO₂), cobalt (II and III) oxides (CoO and Co₂O₃), and chromium (III and VI) oxides (Cr₂O₃ and CrO₃) were successfully obtained. By adjusting the experimental conditions, such as ionization modes and chelating reagents, the non-identical mass spectra were obtained for the elements in the different oxidation state. Thus, the oxidation states could be identified clearly.     

Detection of inorganic species by chemical reaction laser desorption ionization mass spectrometry

The oxidation numbers of metals in inorganic compounds were identified by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) by using their acetylacetonates, which are soluble in acetone. For the MALDI analysis of inorganic species insoluble in common solvents used for matrices, such as acetone, methanol, water, etc., a suspension method of sample preparation was developed. Turbid suspensions of inorganic species in the solvent were spotted on the sample holder with chelating reagents, as in the conventional sample preparation for MALDI-MS. Chemical reaction between the inorganic species and the chelating reagents occurred in the plume after irradiation by laser light. Metal oxides were also analyzed by this method, and samples with different oxidation numbers gave different mass spectra. These results suggest that many other metal oxides with different oxidation numbers could be identified if suitable chelating reagents are chosen for sample preparation for MALDI-MS.     

Ion conductivity of poly(ethylene oxide)-based polyurethane networks containing alkali metal salts

Ion conductivity of poly(ethylene oxide) (PEO)-based polyurethane networks containing alkali metal salts has been investigated. Consequently, it has been revealed that the conductivity is dependent on the following parameters: lattice energy of the alkali metal salt, concentration of alkali metal salt, and the cross-linking density of the network polymer (which is a function both of the amount of cross-linking agent and the molecular weight of PEO). Under optimal conditions, the conductivity at ambient temperature corresponded to 2.51 × 10^?5 Scm^?1, which is greater than that of a typical alkali metal-PEO system by a factor of about 10² to 10³. Moreover, from the standpoint of the application to electrochromic displays (ECD), tensile bond strength between the polymer electrolytes and tungsten trioxide (WO₃), which is the most promising electrochromic material, has been evaluated. The bonding strength of the bond of WO₃ with the present electrolyte has been found to be much larger than that of the alkali metal-PEO system.     

Effects of Cyclodextrins on Deodoration of ``Aging Odor'

Hexenal, octenal and nonenal are known causes of unpleasant body odor and are present at markedly increased levels in the middle-aged and elderly. The odor of such unsaturated aldehydes is therefore called ``aging odor'. The present study investigated the effects of cyclodextrins (CDs) on deodoration of crotonaldehyde, pentenal, hexenal, heptenal, octenal, nonenal, decenal, undecenal and dodecenal. -, - and -CD formed inclusion complexes with the majority of unsaturated aldehydes in aqueous solution. The -CD inclusion complex contained the highest amount of guest molecule. One molecule of -CD was estimated to include 1 molecule of short chain aldehyde and 2 molecules of long chain aldehyde. Deodorant testing was conducted by headspace gas analysis using sealed vials. All CDs decreased the concentrations of unsaturated aldehyde. With nonenal, the deodorant power of parent CDs was -CD > -CD > -CD, and that of chemically modified CD was Me-CD > HP-CD > G2-CD > MCT-CD. CDs were demonstrated to reduce ``aging odor'. Me-CD was the most effective type of CD for the deodoration of ``aging odor'.     

Topological symmetry control in spin density distribution: spin chemistry of phenalenyl-based neutral monoradical systems

[structure: see text] Topological symmetry-based extensions of a pi-conjugation network in an odd alternant phenalenyl radical have enabled us to control the spin density distribution systematically. ESR/ENDOR and NICS studies on the topological isomers of oxophenalenoxyl have revealed that the unpaired electron tends to localize in the antiaromatic ring systems.     

ZrO2酸碱性质的TPD表征 I. 单组分吸附研究

以NH_3、吡啶、Et_3N、CO_2和苯酚为探针，用TPD-MS方法对ZrO_2催化剂的酸碱性质进行了表征．ZrO_2上碱性探针（NH_3、吡啶和Et_3N）的脱附温度远低于在强酸性SiO_2－Al_2O_3上；而酸性探针CO_2的脱附温度远低于在强碱性MgO上的结果．为ZrO_2的弱酸弱碱性质提供了证明．NH_3吸附IR结果表明ZrO_2表面配位不饱合Zr~(4＋)为酸（Lewis酸）中心．NH_3、吡啶和Et_3N与这些酸中心作用的方式和能量分布相似．NH_3和CO_2的TPD谱图均存在三个脱附峰，且相应脱附峰的温度范围相近．表明ZrO_2的酸中心和碱中心具有匹配相当的酸、碱强度，ZrO_2为典型的酸－碱双功能催化剂，在苯酚的TPD过程中，ZrO_2的特征表现为对苯酚的强吸附和对苯酚分解的高活性．文中结合IR结果，对与NH_3和CO_2的脱附相联系的表面吸附物种分别进行了讨论.     

Growth of multicrystalline Si with controlled grain boundary configuration by the floating zone technique

The floating zone technique was employed to grow multicrystalline Si with controlled grain boundary configuration. Purposely designed bi-crystals were utilized as seed crystals to investigate the effect of the tilt angle from the perfect twin boundary on the growth behavior. When the growth was initiated from a bi-crystal with a Σ3 twin boundary, no particular change took place on the grain boundary configuration during growth. On the other hand, the decrease of the tilt angle during growth was observed when the growth was initiated from a bi-crystal with a tilted boundary from Σ3. This was accompanied by the appearance of new crystal grains. The reduction of the total interface energy would be a possible driving mechanism for this phenomenon.