Finding of remarkable synergistic effect on the aroxyl-radical-scavenging rates under the coexistence of α-tocopherol and catechins

Measurements of aroxyl radical (ArO^•)-scavenging rate constants () of antioxidants (AOHs) (α-tocopherol (α-TocH) and three catechins (CatHs) (ie, epicatechin (EC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) were performed in ethanol solution, using stopped-flow spectrophotometry. values were measured not only for each AOH, but also for the mixtures of two AOHs (α-TocH and CatH). A notable synergistic effect that the value of α-TocH increases 1.29, 1.84, and 1.65 times under the coexistence of constant concentrations of EC, EGC, and EGCG, respectively, was observed for the solutions including α-TocH and CatH. Similarly, values of CatHs (EC, EGC, and EGCG) increased 1.72, 2.25, and 2.34 times under the coexistence of constant concentrations of α-TocH, respectively. UV-Vis absorption of α-tocopheroxyl radical (α-Toc^•) (λ_max = 428 nm), which had been produced by reaction of α-TocH with ArO^•, decreased remarkably under the coexistence of α-TocH and CatHs due to the fast α-TocH-regeneration reaction by CatHs. The result suggests that the prooxidant reaction due to α-Toc^• is suppressed by the coexistence of CatHs. By analyzing the formation and decay curves of α-Toc^•, it has been ascertained that one molecule of EGCG having three OH groups at B-ring may rapidly regenerate three molecules of α-Toc^• to α-TocH.     

Nitrogen atom insertion into Ir-S and C-S bonds initiated by photolysis of iridium(III)-azido-dithiocarbamato complexes

Photolysis of acetonitrile solutions of Cp*Ir(R2dtc)(N3) [Cp* = eta5-C5Me5, R2dtc = S2CNR2; R = Me (1) or Et (1')] at temperatures below 0 degrees C afford five-coordinate complexes Cp*Ir{NSC(NR2)S} (2 or 2'), where a nitrogen atom has been inserted into one of the Ir-S bonds. In solution, complex 2 thermally convert to the azaethene-1,2-dithiolate complex, Cp*Ir[SN=C(NMe2)S] (3), which could be crystallized as the corresponding dimer, {Cp*Ir[mu-SN=C(NMe2)S-kappa3S:S,S']}2 (4). As a result, a nitrogen atom that originated in the azide ligand is transferred into a C-S bond of the dithiocarbamate.     

Atomic absorption spectrometry of traces of tri- and hexavalent chromium

Summary Atomic absorption spectrometry combined with extraction is described for the determination of tri- and hexavalent chromium. The chromium diethyldithiocarbamate chelate was used for chromium (VI), whereas hydroxyquinolate or thenoyltrifluoroacetonate chelate for chromium(III). The method is rapid and precise.

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Zusammenfassung Extraktion und darauffolgende Messung der Atomarabsorption wurden zur Bestimmung von drei- und sechswertigem Chrom verwendet. Die Chelatverbindung mit Diäthyldithiocarbamat wurde für Chrom(VI), der Chelatkomplex mit Hydroxychinolin oder Thenoyltrifluoraceton für Chrom(III) verwendet. Das Verfahren ist rasch und genau.

     

Structure and dioxygen-reactivity of copper(I) complexes supported by bis(6-methylpyridin-2-ylmethyl)amine tridentate ligands

The structure and dioxygen-reactivity of copper(I) complexes R supported by N,N-bis(6-methylpyridin-2-ylmethyl)amine tridentate ligands L2R[R (N-alkyl substituent)=-CH2Ph (Bn), -CH2CH2Ph (Phe) and -CH2CHPh2(PhePh)] have been examined and compared with those of copper(I) complex (Phe) of N,N-bis[2-(pyridin-2-yl)ethyl]amine tridentate ligand L1(Phe) and copper(I) complex (Phe) of N,N-bis(pyridin-2-ylmethyl)amine tridentate ligand L3(Phe). Copper(I) complexes (Phe) and (PhePh) exhibited a distorted trigonal pyramidal structure involving a d-pi interaction with an eta1-binding mode between the metal ion and one of the ortho-carbon atoms of the phenyl group of the N-alkyl substituent [-CH2CH2Ph (Phe) and -CH2CHPh2(PhePh)]. The strength of the d-pi interaction in (Phe) and (PhePh) was weaker than that of the d-pi interaction with an eta2-binding mode in (Phe) but stronger than that of the eta1 d-pi interaction in (Phe). Existence of a weak d-pi interaction in (Bn) in solution was also explored, but its binding mode was not clear. Redox potentials of the copper(I) complexes (E1/2) were also affected by the supporting ligand; the order of E1/2 was Phe>R>Phe. Thus, the order of electron-donor ability of the ligand is L1Phe相似文献   

Cobalt(III) complexes of monodentate N9-bound adeninate (ade-), [Co(ade-kappaN9)Cl(en)2]+ (en = 1,2-diaminoethane): syntheses, crystal structures, and protonation behaviors of the geometrical isomers

In acidic aqueous solution, a cobalt(III) complex containing monodentate N(9)-bound adeninate (ade(-)), cis-[Co(ade-kappaN(9))Cl(en)(2)]Cl (cis-[1]Cl), underwent protonation to the adeninate moiety without geometrical isomerization or decomposition of the Co(III) coordination sphere, and complexes of cis-[CoCl(Hade)(en)(2)]Cl(2) (cis-[2]Cl(2)) and cis-[Co(H(2)ade)Cl(en)(2)]Cl(3) (cis-[3]Cl(3)) could be isolated. The pK(a) values of the Hade and H(2)ade(+) complexes are 6.03(1) and 2.53(12), respectively, at 20 degrees C in 0.1 M aqueous NaCl. The single-crystal X-ray analyses of cis-[2]Cl(2).0.5H(2)O and cis-[3]Cl(2)(BF(4)).H(2)O revealed that protonation took place first at the adeninate N(7) and then at the N(1) atoms to form adenine tautomer (7H-Hade-kappaN(9)) and cationic adeninium (1H,7H-H(2)ade(+)-kappaN(9)) complexes, respectively. On the other hand, addition of NaOH to an aqueous solution of cis-[1]Cl afforded a mixture of geometrical isomers of the hydroxo-adeninato complex, cis- and trans-[Co(ade-kappaN(9))(OH)(en)(2)](+). The trans-isomer of chloro-adeninato complex trans-[Co(ade-kappaN(9))Cl(en)(2)]BF(4) (trans-[1]BF(4)) was synthesized by a reaction of cis-[2](BF(4))(2) and sodium methoxide in methanol. This isomer in acidic aqueous solution was also stable toward isomerization, affording the corresponding adenine tautomer and adeninium complexes (pK(a) = 5.21(1) and 2.48(9), respectively, at 20 degrees C in 0.1 M aqueous NaCl). The protonated product of trans-[Co(7H-Hade-kappaN(9))Cl(en)(2)](BF(4))(2).H(2)O (trans-[2](BF(4))(2).H(2)O) could also be characterized by X-ray analysis. Furthermore, the hydrogen-bonding interactions of the adeninate/adenine tautomer complexes cis-[1]BF(4), cis-[2](BF(4))(2), and trans-[2](BF(4))(2) with 1-cyclohexyluracil in acetonitrile-d(3) were investigated by (1)H NMR spectroscopy. The crystal structure of trans-[Co(ade)(H(2)O)(en)(2)]HPO(4).3H(2)O, which was obtained by a reaction of trans-[Co(ade)(OH)(en)(2)]BF(4) and NaH(2)PO(4), was also determined.     

Photocatalytic Reduction of NO with C2H6 on a Hollandite-Type Catalyst

The photocatalytic reduction of nitrogen monoxide (NO) with ethane on the hollandite type catalyst (K₂Ga₂Sn₆O₁₆KGSO) was investigated. Using a closed-gas circulating system equipped with a Q-MASS detector and in-situ diffuse reflectance FT-IR spectroscopy. The reactant gases of NO and ¹³C₂H₆ decreased with the increasing irradiation time. In contrast, the N₂ yield increased proportionally to the conversion of ¹³C₂H₆. Nitrogen oxides such as N₂O did not reach their detectable levels. The NO adsorbed on KGSO was found to change to its activated species by UV irradiation. The oxidized products of C₂H₆ such as CH₃CHO increased in proportion to the reaction time. The present results strongly suggest that KGSO has remarkable photocatalytic activity for the reduction of NO with C₂H₆.     

Analysis of conjugated linoleic acids as 9-anthrylmethyl esters by reversed-phase high-performance liquid chromatography with fluorescence detection

A simple and highly sensitive method for determining the fatty acid composition of food lipids containing conjugated linoleic acid (CLA) is described. The method is based on the separation of the 9-anthrylmethyl ester derivatives of saturated and unsaturated (conjugated and non-conjugated) fatty acids by reversed-phase high-performance liquid chromatography with fluorescence detection. Just like the other fatty acids, CLA reacts readily with 9-anthryldiazomethane at room temperature to produce 9-anthrylmethyl esters without isomerization and decomposition of the conjugated double bonds. Clear resolution of the individual fatty acids as their 9-anthrylmethyl esters is achieved on a highly efficient octadecylsilylated silica column (150- x 3-mm i.d., 3-microm particle size) using a stepwise gradient elution with methanol-water. The method is standardized with commercially available CLA isomers (cis-9, trans-11 and trans-10, cis-12-octadecadienoic acids, and their cis,cis and trans,trans isomers) and applied for determination of the fatty acid compositions of milk and sdairy products.     

Synthesis of carbazole,acridine, phenazine, 4H‐benzo[def]carbazole and their derivatives by thermal cyclization reaction of aromatic amines

A variety of nitrogen‐containing heterocycles were synthesized by passing vapors of aromatic amines over calcium oxide at 450–650 °C under nitrogen carrier gas. Reaction of 2‐aminobiphenyl 3a at 560 °C gave carbazole 4 in 80% yield. Reaction of 2, 2′‐diaminobiphenyl 3b afforded a mixture of carbazole 4 and 4‐aminocarbozole 6b. In the case of 2‐amino‐2′‐nitrobiphenyl 3c, benzo[c]cinnoline 7 was obtained along with carbazole 4. Reaction of 2‐amino‐2′‐methoxybiphenyl 3d gave four products of carbazole 4,4‐hydroxycarbazole 6e, phenanthridine 8 and dibenzofuran 9. Reaction of 2‐aminodiphenylmethane 5a afforded acridine 10. In the case of 2‐aminobenzophenone 5b, acridone 11 was obtained as a major product. Reaction of 2‐aminobenzhydrol 5c gave acridine 10. When 2‐aminodiphenylamine 5d was reacted, phenazine 12 was obtained in good yield. In contrast, reaction of 2‐aminodiphenyl ether 5e produced only 2‐hydroxydiphenylamine 13. Reaction of 4‐aminophenanthrene 14 produced 4H‐benzo[def]carbazole 15 in 61% yield.     

Acylation of heteroaromatic amines . Perbenzoylation of diaminopyridazines

Some diaminopyridazines such as 4,7-diaminoimidazo[4,5-d]pyridazine, 1-methyl-4,7-diaminoimidazo[4,5-d]pyridazine, 5,8-diaminopyrazino[2,3-d]pyridazine, 2,3-dimethyl-5,8-diaminopyrazino[2,3-d]pyridazine and 1,4-diaminophthalazine, all of which were prepared by the reaction of hydrazine with the respective vic-dicyanide as starting material, were reacted with benzoyl chloride in the presence of triethylamine, giving novel perbenzoylated derivatives in good yield. A dibenzoylation mechanism of the amino group has been proposed.