Synthesis and ligand-based mixed valency of cis- and trans-Cr(III)(X(4)SQ)(X(4)Cat)(L)(n) (X = Cl and Br,n = 1 or 2) complexes: effects of solvent media on intramolecular charge distribution and ligand dissociation of Cr(III)(X(4)SQ)(3)

The treatment of Cr(III)(X(4)SQ)(3) (SQ = o-semiquinonate; X = Cl and Br) with acetonitrile affords trans-Cr(III)(X(4)SQ)(X(4)Cat)(CH(3)CN)(2) (X = Cl (1) and Br (2)). In the presence of 2,2'-bipyridine (bpy) or 3,4,7,8-tetramethyl-1,10-phenanthrene (tmphen), the reaction affords Cr(III)(X(4)SQ)(X(4)Cat)(bpy).nCH(3)CN (X = Cl, n = 1 (3); X = Br, n = 0.5 (4)) or Cr(III)(X(4)SQ)(X(4)Cat)(tmphen) (X = Cl (5) and Br (6)), respectively. All of the complexes show a ligand-based mixed-valence (LBMV) state with SQ and Cat ligands. The LBMV state was confirmed by the presence of the interligand intervalence charge-transfer band. Spectroscopic studies in several solvent media demonstrate that the ligand dissociation included in the conversion of Cr(III)(X(4)SQ)(3) to 1-6 occurs only in solvents with relatively high polarity. On the basis of these results, the effects of solvent media were examined and an equilibrium, Cr(III)(X(4)SQ)(3) <--> Cr(III)(X(4)BQ)(X(4)SQ)(X(4)Cat) (BQ = o-benzoquinone), is proposed by assuming an interligand electron transfer induced by solvent polarity.     

New possibility for an organic semiconductor: a smectic liquid crystalline semiconductor having a long conjugated core and two long alkyl chains

We report a new possibility for liquid crystalline organic semiconductors. These materials exhibit smectic liquid crystalline phases, in which the molecules assume a smectic molecular order by self-assembly. Because of the strong dispersion force among long alkyl chains, on cooling, smectic molecular order was retained at room temperature. A charge transport ability was also retained. The conductivity of a device having smectic liquid crystalline order is about 5×10⁷ that of a device with no smectic order. The current - voltage characteristic of the device has a very sharp increase at low threshold voltage (5 V). A high carrier mobility of 1.8×10^-2 was observed in the smectic phase of one of the compounds studied (e).     

Mössbauer characterization of calcium–ferrite oxides prepared by calcining Fe2O3 and CaO

Calcium ferrite oxides were prepared by calcining a mixture powder of iron- and calcium oxide. The ⁵⁷Fe-Mössbauer spectra of the calcium ferrites oxides were measured, revealing that the products should be Ca₂Fe₂O₅ and CaFe₂O₄, the ratio of which was dependent of the Fe/Ca atomic ratio of the mixture powder.     

Signal enhancement in ESR spin-trapping for hydroxyl radicals.

In an ESR spin-trapping measurement of hydroxyl radicals formed in a Fenton reaction, the trapping efficiency with DMPO increased by about 300 times in a sodium trifluoroacetate solution, whereas it was little changed in a phosphate buffer.     

A new approach to benzofuran synthesis: Lewis acid mediated cycloaddition of benzoquinones with stilbene oxides

We report a BF₃-mediated novel dehydrative cycloaddition reaction of benzoquinones with stilbene oxides to afford 2,3-diaryl-5-hydroxybenzofurans and 2,3-diaryl-5-hydroxydihydrobenzofurans in good combined yields. No change in the products or the yield is observed when using diphenylacetaldehyde and cis-stilbene oxide instead of trans-stilbene oxides. When stilbene oxide is reacted with hydroquinone instead of the corresponding benzoquinone under the same conditions, dihydrobenzofuran is isolated in high yield. On the basis of these results, we propose the following possible reaction mechanism: stilbene oxide is converted to a phenonium ion (the key intermediate), which undergoes nucleophilic attack by benzoquinone or the simultaneously generated hydroquinone and subsequent dehydrative intramolecular cyclization to afford benzofuran or dihydrobenzofuran, respectively.     

The interfacial effect on ionic conduction of AgI–anatase TiO2 composites

AgI–anatase TiO₂ nanoparticle composites, (x)AgI–(1 ? x)anatase, with different porosities were fabricated over a wide range of 0–1 of AgI content. The electrical conductivity was measured at room temperature as function of AgI content (x) and porosity (p). The conductivity varies considerably with both x and p. In the vicinity of x = 0.4 and p = 0.31, the conductivity attains a maximum (2.5 × 10^? 3 S/cm). The conductivity is enhanced by three orders of magnitude in comparison with that of pristine AgI. The mechanism of the observed conductivity enhancement is discussed in the light of the scanning electron microscope images and X-ray diffraction patterns of the different (x)AgI–(1 ? x)anatase composites.     

Quantitative estimation of thermal contact conductance of a real front‐end component at SPring‐8 front‐ends

The thermal contact conductance (TCC) of a real front‐end component at SPring‐8 has been quantitatively estimated by comparing the results of experiments with those of finite‐element analyses. In this paper one of the methods of predicting the TCC of a real instrument is presented. A metal filter assembly, which is an indirect‐cooling instrument, was selected for the estimation of the TCC. The temperature of the metal filter assembly for the maximum heat load of synchrotron radiation was calculated from the TCC that is expected under normal conditions. This study contributes towards the ongoing research program being conducted to investigate the real thermal limitation of all front‐end high‐heat‐load components.     

Improvement of vacuum nebulizing interface for direct coupling micro-liquid chromatograph with mass spectrometer and some applications to polar natural organic compounds

Summary A vacuum nebulizing interface for direct coupling a micro-liquid chromatograph (LC) with a mass spectrometer (MS) was improved by incorporating a small water cooling jacket and a bubble saturator for the nebulizing gas. By this improvement the applicability of the micro-LC-MS system was remarkably extended to various non-volatile polar organic compounds such as adenosine, tryptophane, glycyl-glycyl-glycine, mono- and di-saccharides, etc. The desirable temperature profile around the nebulizing tip was also discussed.

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Verbesserung eines Vakuumzerstäubers als Zwischenstück zur direkten Kopplung von Mikro-Flüssig-Chromatograph und Massenspektrometer. Anwendung auf polare organische Verbindungen

Zusammenfassung Ein Vakuumzerstäuber wurde durch Einführung eines Wasser-Kühlmantels und einer Sättigungsvorrichtung für das Zerstäubergas verbessert. Dadurch konnte die Anwendbarkeit des Systems auf verschiedenartige nichtflüchtige polare organische Verbindungen (u. a. Adenosin, Tryptophan, Glycyl-glycyl-glycin, Mono- und Disaccharide) ausgedehnt werden. Das optimale Temperaturprofil und die Zerstäuberspitze wurde ebenfalls untersucht.