Cation exchange induced tunable properties of a nanoporous octanuclear Cu(II) wheel with double-helical structure

A double-helical octanuclear Cu(II) wheel 1 with 2.88 nm diameter was prepared through the reaction of a clinical medicine, telmisartan, with copper sulfate. Central copper ions can be partially replaced by bivalent zinc and cobalt ions and fully exchanged by trivalent iron ions. The properties of central metal ion-exchanged variants are much different from those of 1. Central metal ion exchange might be regarded as a powerful and effective method to modify properties from one crystalline material to another only by varying central metal ions under moderate conditions.     

Lewis Acid-Assisted Molybdenum(VI) Complexes with S,N-bidentate Ligands to Reduce Nitrate

Two readily-accessible molybdenum complexes with low sterically hindered S, N-bidentate ligands were designed for the reduction of nitrate to nitrite. The Lewis acid Sc(III) acted as a significant co-catalyst to enhance the catalytic efficiency by activating the N−O bond of nitrate. This study indicates that molybdenum complexes in cooperation with a Lewis acid offer functional Mo-catalyst systems, which present functional artificial models of the natural molybdenum enzymes.     

Effects of ethanol extract from Saururus chinensis (Bour.) Baill on lipid and antioxidant metabolisms in rats fed a high-fat diet

This study was performed to investigate the effect of ethanol extract from Saururus chinensis (Lour.) Baill on liver function, plasma lipid composition and antioxidant system with high-fat diet for 4 weeks. Rats were divided into the following five groups; untreated control group (normal), treated with 0.5% SE (normal + 0.5% SE), high-fat group (high-fat), high-fat group treated with 0.1% SE (high-fat + 0.1% SE), or 0.5% SE (high-fat + 0.5% SE). Weight gains showed a tendency to decrease in rat with high-fat + SE. Plasma total cholesterol showed a tendency to decrease with ethanol extract from S. chinensis (Lour.) Baill. LDL-cholesterol contents were lower in ethanol extract group than that of control group. Aspartate amino transferase and alanine amino transferase activities were increased by high-fat diet, and were decreased by 0.5% SE. Lipid peroxide level showed a tendency to increase in high-fat diet group than that of normal group. In ethanol extract from S. chinensis (Lour.) Baill groups, lipid peroxide level decreased significantly and SOD activity was also decreased progressively. These results demonstrated that the ethanol extract of S. chinensis (Lour.) Baill lowered serum cholesterol levels, tissue lipid contents and accumulation of cholesterol in the rat.     

Size characterization of drug-loaded polymeric core/shell nanoparticles using asymmetrical flow field-flow fractionation

Asymmetrical flow field-flow fractionation (AsFlFFF) was used to determine the size distribution of drug-loaded core/shell nanoparticles which have a lipid core of lecithin and a polymeric shell of a Pluronic. AsFlFFF provided separation of the drug-loaded core/shell nanoparticles from smaller coreless polymeric micelles, thus allowing accurate size analysis of the drug-loaded nanoparticles without interference by the coreless micelles. It was found from AsFlFFF that the drug-loaded nanoparticles have broad size distributions ranging from 100 to 600 nm in diameter. It was also found that, after the nanoparticles had been stored for 70 days, they disappeared as a result of self-degradation. Being a separation technique, AsFlFFF seems to be more useful than transmission electron microscopy or dynamic light scattering for size analysis of core/shell nanoparticles, which have broad and bimodal size distributions. Figure Separation by AsFlFFF     

Multihollow structured poly(methyl methacrylate)/silver nanocomposite microspheres prepared by suspension polymerization in the presence of dual dispersion agents

Poly(methyl methacrylate) (PMMA)/silver nanocomposite microspheres with unique multihollow structures were prepared by suspension polymerization in the presence of dual dispersion agents. The addition of a lipophilic emulsifier, polyethylene glycol (30EO) dipolyhydroxystearate (Arlacel P135), not only stabilized water-in-oil (W/O) emulsion, but also converted silver nanoparticles from hydrophilic to lipophilic. When a suspension polymerization dispersion agent, poly(vinyl alcohol), was added to the above W/O emulsion system, a water-in-oil-in-water suspension was formed with silver nanoparticles dispersed in the oil phase. The suspension polymerization was carried out at low temperature with 2,2’-azobis(2,4-dimethylvaleronitrile) as the initiator. When modified silver nanoparticles were added, the rate of polymerization increased slightly. High monomer conversion (about 85%) was obtained in spite of low polymerization temperature of 30 °C. Under controlled conditions, PMMA/silver microspheres with various hollow structures were synthesized. The PMMA/silver microspheres with multihollow structure showed high antibacterial ability.     

Polymeric zinc ferrocenyl sulfonate as a molecular aspirator for the removal of toxic metal ions

A porous bilayered open coordination polymer [Zn(4,4'-bpy)(2)(FcphSO(3))(2)](n) (1; FcphSO(3)Na=m-ferrocenyl benzenesulfonate), has been assembled from Zn(NO(3))(2), m-ferrocenyl benzenesulfonate, and the bridging ligand 4,4'-bipyridine (4,4'-bpy). Ion-exchange induced products [Cd(0.6)Zn(0.4)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (2), [Zn(0.75)Pb(0.25)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (3), and [Cu(0.5)Zn(0.5)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (4) could be obtained directly by suspending a big single crystal of 1 into concentrated solutions of Cd(NO(3))(2), Pb(NO(3))(2), and Cu(NO(3))(2), respectively. Most importantly, the big single crystal of 1 could be partly regenerated after immersion into concentrated aqueous solutions of Zn(NO(3))(2). On the other hand, powdered 1 could also be used as a metal ion adsorbent because of the well-defined pore size and pore shape. Ion exchange takes place along with the process of ion sorption. The big single crystal of 1 removes harmful metal ions by means of ion exchange, whereas powdered 1 removes toxic metal ions mainly through ion sorption. Also, compound 1 could be employed as a multi-ion analysis fluorescent probe to detect dangerous metal ions, such as Pb(2+), Cd(2+), Ag(+), and Cu(2+). The compounds described in this study may have potential applications in the design of new molecular devices.     

Identification of five hepatotoxic pyrrolizidine alkaloids in a commonly used traditional Chinese medicinal herb, Herba Senecionis scandentis (Qianliguang)

Senecio scandens Buch.-Ham is a plant source for a commonly used traditional Chinese medicinal (TCM) herb Qianliguang. A TCM herbal proprietary product containing Qianliguang as the major herb for the treatment of sinusitis has been used in China for several decades, and has also been exported to other regions and countries worldwide. In the present study, the aqueous extract of S. scandens collected in the Shanxi Province of China was determined, for the first time, to contain hepatotoxic and tumorigenic pyrrolizidine alkaloids (PAs) by using high-performance liquid chromatography/mass spectrometric (HPLC/MS) analysis in various scanning modes. A total of nine toxic and two non-toxic PAs were detected in the aqueous extract of S. scandens, of which six PAs, namely neoplatyphylline, senecionine, senecionine N-oxide, seneciphylline, seneciphylline N-oxide and senkirkine, were unequivocally characterized, while other PAs were tentatively assigned as jacobine, jacozine N-oxide (or erucifoline N-oxide), 7-tigloylplatynecine, usaramine and an isomer of yamataimine. The estimated total content of toxic PAs in S. scandens was 10.82 microg/g herb, which was significantly higher than that (> or =1 microg/g herb) recommended by Belgium and Germany not to be used clinically. Among the PAs definitively identified, senecionine, seneciphylline, and senkirkine are known tumorigens capable of inducing liver tumors in experimental animals, while seneciphylline N-oxide and senecionine N-oxide are probably tumorigenic due to their potential conversion into seneciphylline and senecionine via metabolic reduction in the body. Thus, the current finding of the presence of toxic/tumorigenic PAs in S. scandens challenges the safety of using this TCM herb and its proprietary products.     

Syntheses and characterization of elpasolite-type ammonium alkali metal hexafluorometallates(III)

Crystal structures of three fluorides (NH₄)₂NaFeF₆, (Fe), (NH₄)₂NaGaF₆, (Ga), and (NH₄)₂NaCrF₆, (Cr), as well as a substituted compound [(NH₄)_1−xK_x]₂KAlF₆ (x≈0.17), (Al), have been refined using single-crystal and powder X-ray diffraction techniques. All these four ammonium hexafluorides have a cubic elpasolite-type structure and crystallize in the space group Fm3¯m with lattice constants a=8.483(3), 8.450 (3), 8.4472(2) and 8.724(3) Å for compounds (Fe), (Ga), (Cr) and (Al), respectively. The effective ionic radius of the ammonium ion calculated from those compounds has a mean value of R=1.729 Å for CN=12. An ultraviolet-visible absorption spectrum of (NH₄)₂NaCrF₆, measured at room temperature, gives a crystal field (Dq=1575 cm⁻¹) and Racah parameters (B=758 cm⁻¹ and C=3374 cm⁻¹). Abnormal anisotropic thermal parameters of fluorine atoms have been observed in the compound (Al), and interpreted to arise from four strong hydrogen bonds (F…H-N) that are distributed in a square form around each fluorine atom.     

Determination of impurities in illicit methamphetamine seized in Korea and Japan

Impurities produced during synthesis of methamphetamine (MA) show different patterns under various synthetic conditions. Valuable information on the origins and smuggling routes can be obtained by using impurities as chemical fingerprints. We have detected more than 100 compounds from 436 MA samples seized in Korea by gas chromatography-flame ionization detector and gas chromatography-mass spectrometer, among which 31 impurities and three additives were identified. Twenty-six impurity peaks including unknowns were selected as the indicators of similarity, and were used as variables for cluster analysis. Cluster analysis result showed that part of the MA samples seized in Japan might have the same origin as those seized in Korea. It means that broad-based cooperation is necessary for efficient regulation of MA. Synthetic trends of the MA seizures of Korea were monitored by cluster analysis with 16 MA samples synthesized by three different methods in the previous work. We could find comparable changes of synthetic trends, which might have been influenced by domestic regulations and international situations.     

CO removal by two-stage methanation for polymer electrolyte fuel cell

In order to remove CO to achieve lower CO content of below 10 ppm in the CO removal step of reformer for polymer electrolyte fuel cell （PEFC） co-generation systems, CO preferential methanation under various conditions were studied in this paper. Results showed that, with a single kind of catalyst, it was difficult to reach both CO removal depth and CO2 conversion ratio of below 5%. Thus, a two-stage methanation process applying two kinds of catalysts is proposed in this study, that is, one kind of catalyst with relatively low activity and high selectivity for the first stage at higher temperature, and another kind of catalyst with relatively high activity and high selectivity for the second stage at lower temperature. Experimental results showed that at the first stage CO content was decreased from 1% to below 0.1% at 250-300 ℃, and at the second stage to below 10 ppm at 150-185 ℃. CO2 conversion was kept less than 5%, At the same time, influence of inlet CO content and GHSV on CO removal depth was also discussed in this paper.