Tuning of electronic structures of quasi-one-dimensional bromo-bridged Ni(III) complexes with strong electron-correlation by doping of Co(III) ions, [Ni(1-x)Co(x)(Chxn)(2)Br]Br(2)

We have succeeded in synthesizing the Ni(III) complexes doped by Co(III) ions, [Ni(1-x)Co(x)(chxn)(2)Br]Br(2) (x = 0, 0.043, 0.093, and 0.118) by using an electrochemical oxidation method. The single-crystal reflectance spectrum of x = 0.118 shows an intense CT band about 0.5 eV, which is lower than that of [Ni(chxn)(2)Br]Br(2) (1.3 eV). The single-crystal electrical conductivities at room temperature of these compounds increase with increase of the amounts of doping of Co(III) ions. In the ESR spectra, peak-to-peak line widths DeltaH(pp) at room temperature change about 600 G in [Ni(chxn)(2)Br]Br(2) to 200 G in x = 0.118. Such a large x dependence of DeltaH(pp) seems to be ascribed to the increasing contribution from the increasing Curie spins which have smaller line width. Therefore, we have tuned the electronic structures of quasi-one-dimensional bromo-bridged Ni(III) complexes with strong electron correlations by doping of Co(III) ions.     

Solvent effect on distribution ratio of Pd(II) in supercritical carbon dioxide extraction and solvent extraction using 2-methyl-8-quinolinol

The distribution ratio (D_M) of Pd(II) by the extraction with 2-methyl-8-quinolinol (HMQ) was determined using the supercritical carbon dioxide medium (SF-CO₂) and organic solvent media such as perfluoro-methylcyclohexane, heptane, cyclohexane, carbon tetrachloride and benzene. From experimental results of the slopes of log D_M versus pH plot and log D_M versus HMQ concentration plot, the extracted species both in the SF-CO₂ extraction (SFE) and the solvent extraction (SE) were determined to be Pd(MQ)₂. The distribution constant of HMQ (K_D,HMQ) in the SFE and SE systems were determined from the dependence of the distribution ratio of HMQ (D_HMQ) on the pH. A linear relationship was observed between log K_D,HMQ and the solubility parameter (δ) of the extraction medium based on the regular solution theory in both the SFE using SF-CO₂ at the pressure of 8.5–40 MPa and the SE systems. The difference in the slope of the log K_D,HMQ versus δ plot between the SFE and the SE systems is attributable to the extent of the specific interaction of the solute HMQ with the solvent molecules, i.e. CO₂ molecules and the organic solvent molecules. The D_M versus δ plot obtained under a given extraction condition using SF-CO₂ (11–40 MPa) and organic solvents showed clear linearity. The D_M obtained using SF-CO₂ at relatively low pressure range from 8.5 to 11 MPa was independent of the pressure and the δ of SF-CO₂, which coincides with the experimental fact that the solubility of Pd(MQ)₂ in the SF-CO₂ at 8.5–11 MPa was practically constant.     

Yield of fullerenes generated by contact arc method under He and Ar: dependence on gas pressure

The yields of toluene-soluble material from carbon soot depend on the buffer gas as well as the pressure. Helium was more effective for yielding fullerenes than argon, and the optimum pressure was 20 Torr, under which a maximum yield of about 13 wt% was obtained. C₆₀ showed a maximum abundance at 20 Torr, while C₇₀ and higher fullerenes (C₇₆, C₇₈ and C₈₄) at a slightly higher pressure between 20 and 50 Torr. Raw soot was also studied by electron microscopy. The pressure dependence of the fullerene yield is discussed in terms of the cooling rate and diffusion of carbon vapor around the evaporation source.     

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Three kinds of Ru/CeO₂ catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO₂, and TPR experiment showed that the reaction, RuO₂ + 2H₂ Ru + 2H₂O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.     

Application of shielded column liquid chromatography for determination of sulfamonomethoxine, sulfadimethoxine, and their N4-acetyl metabolites in milk

A hazardous-chemical free method for simultaneous determination of sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and their N4-acetyl metabolites in raw milk using shielded column liquid chromatography is developed. The target analytes are extracted by mixing with ethanol-acetic acid (97:3, v/v) followed by centrifugation. The procedure uses a Hisep shielded hydrophobic phase (SHP) column, isocratic elution with 0.1% acetic acid solution (pH 3.1, in water)-ethanol (75:25, v/v), and a photo-diode array detector. Average recoveries from samples spiked at 25-500 ng/ml for each drug were >81% with relative standard deviations within 5%. The limits of quantitation were <25 ng/ml.     

Synthesis of a capillarisin sulfur-analogue possessing aldose reductase inhibitory activity by selective isopropylation

We describe the synthesis of 2-[(4-hydroxyphenyl)thio]-7-isopropoxy-5,6-dimethoxy-4H-chromen-4-one 2 from 3,4,5-trimethoxyphenol 6 via the key intermediate, 3-iodo-7-isopropoxy-5,6-dimethoxy-4H-chromen-4-one 3. An important feature of this synthetic scheme involves selective alkylation, which can be achieved by two different routes. One route involves the selective isopropylation of a triacetate derivative 4 under basic conditions. The second route employs the selective demethylation of a trimethoxy derivative 5 under acidic conditions followed by isopropylation. The product of these alternative routes, compound 3, is then converted to a capillarisin sulfur analogue 2 in a one-pot reaction via the imidazolyl intermediate 22.     

Regio- and stereoselective reactions of gem-difluorinated vinyloxiranes with heteronucleophiles

[Reaction: see text]. Regio- and stereoselectivity in reactions of gem-difluorinated vinyloxiranes with heteronucleophiles were successfully controlled. Halogen atoms were introduced regioselectively at the allylic epoxide carbon with an inversion in stereochemistry using MgBr2*Et2O or Li2CuCl4 to produce anti-vic-halohydrine. The other diastereomers were obtained selectively using LiBr/AcOH or BCl3, and SN2' type products were formed selectively with excellent E preference by changing the reaction temperature. Moreover, a further investigation led us to find that a regio- and stereoselective SN2' addition of several Brnsted acids was dependent on the pKa values of the acids. Under strong acidic conditions, we exclusively obtained E allylic alcohols.     

Synthesis and Structure of Ba8Cu3In4N5 with Nitridocuprate Groups and One-Dimensional Infinite Indium Clusters

Single crystals of the quaternary compound Ba₈Cu₃In₄N₅ were prepared by heating Ba, Cu, and In in a Na flux at 1023 K under 7 MPa of N₂, and by slow cooling from this temperature. The crystal structure was analyzed by single-crystal X-ray diffraction. It crystallizes in an orthorhombic cell (space group Immm (No. 71), Z=2) with a=4.0781(6), b=12.588(2), and c=19.804(3) Å at 298 K. The structural formula is expressed as Ba₈[CuN₂]₂ [CuN]In₄. Nitridocuprates of one-dimensional chains ¹_∞[CuN_2/2] and isolated units ⁰[CuN₂], and one-dimensional indium clusters ¹_∞[In₂In_4/2] are contained in the structure. A split-site model applied for the arrangement of ¹_∞[CuN_2/2] chains suggested that there is a short-bond, long-bond alternation of the Cu-N bondings. The electrical resistivity of Ba₈Cu₃In₄N₅ was 3.44 mΩ·cm at 298 K. A metallic temperature dependence of the resistivity was observed down to 10 K.