Self-organization of all-inorganic dodecatungstophosphate nanocrystallites

The crystallinity and porosity of all-inorganic dodecatungstophosphate M3PW12O40 (M=Cs, NH4, Ag, denoted as MPW) particles are controlled by the changes in the synthetic temperatures and countercations. The MPW particles can be classified into three groups by the crystallinity and porosity: (i) mesoporous "disordered" aggregates, (ii) microporous "self-organized" aggregates, and (iii) nonporous single crystals. The formation and growth mechanism of MPW particles is expressed by three steps: formation of nanocrystallites, assembly of the nanocrystallites to form aggregates, and the growth of aggregates by the attachment of nanocrystallites. The time courses of the turbidity of the synthetic solution, the concentration of the nanocrystallites, and the average particle sizes of MPW particles are well reproduced by the calculation based on the mechanism.     

Mechanism of [gamma-H2SiV2W10O40](4-)-catalyzed epoxidation of alkenes with hydrogen peroxide

The mechanism of [gamma-H2SiV2W10O40]4--catalyzed epoxidation of alkenes with hydrogen peroxide in acetonitrile/tert-butyl alcohol was investigated. The negative Hammett rho+ (-0.88) for the competitive oxidation of p-substituted styrenes and the low XSO (XSO = (nucleophilic oxidation)/(total oxidation)) value of <0.01 for the [gamma-H2SiV2W10O40]4--catalyzed oxidation of thianthrene-5-oxide reveal that the strong electrophilic oxidant species is formed on [gamma-H2SiV2W10O40]4- (I). The preferable formation of trans-epoxide for the epoxidation of 3-substituted cyclohexenes shows the steric constraints of the active oxidant on I. The 51V NMR, 183W NMR, and CSI-MS spectroscopy show that the reaction of I with hydrogen peroxide leads to the reversible formation of a hydroperoxo species [gamma-HSiV2W10O39OOH]4- (II). The successive dehydration of II forms III, which possibly has an active oxygen species of a mu-eta2:eta2-peroxo group. The kinetic and spectroscopic studies show that the present epoxidation proceeds via III. The energy diagram of the epoxidation with density functional theory (DFT) supports the idea.     

Hydrodefluorinations by low-valent niobium catalyst

Catalytic hydrodefluorinations of organofluorine compounds by low-valent niobium catalyst were developed. In the presence of niobium(V) chloride (typically, 5 mol%), fluorobenzenes, α,α,α-trifluorotoluenes and (trifluoromethyl)pyridines were hydrodefluorinated with lithium aluminum hydride to give the corresponding benzenes, toluenes and methylpyridines in good yields, respectively.     

Preparation of petaloid microspheres of basic magnesium carbonate

The synthesis of basic magnesium carbonate was examined under ultrasonic irradiation and was performed by the soda ash method using magnesium sulfate and sodium carbonate as starting materials. The particulate product was evaluated using SEM observations. Ultrasonic irradiation in the preparation of basic magnesium carbonate was found to give fine petaloid microspheres of about 3 mum in primary particle size.     

Artificial DNAs based on alkynyl C-nucleosides as a superior scaffold for homo- and heteroexcimer emissions

DNA-like fluorescent oligomers composed of alkynyl beta-D-ribofuranosides bearing pyrene, perylene, and anthracene as a fluorophore were synthesized by solid-phase DNA synthesis. The fluorescent oligomers possess the defined number and order of the fluorophores. In these oligomers, the adjacent fluorophores efficiently interact with each other by hydrophobic interactions in their electronic ground states in a face-to-face fashion. The predominant excimer emissions were observed from not only the homooligomers (pyrene-pyrene and perylene-perylene systems) but also the heterooligomers (pyrene-perylene, pyrene-anthracene, and perylene-anthracene systems) in aqueous media.     

Combined application of comprehensive analysis for DNA modification and reporter gene mutation assay to evaluate kidneys of gpt delta rats given madder color or its constituents

DNA adductome analysis using liquid chromatography–tandem mass spectrometry is a promising tool to exhaustively search DNA modifications. Given that the molecular weight of chemical-specific adducts is determined by the total molecular weights of the active form and nucleotide bases, we developed a new method of comprehensive analysis for chemical-specific DNA adducts based on the principle of adductome analysis. The actual analytical mass range was 50 mass units up or down from the average molecular weight of the four DNA bases plus the molecular weight of the expected active form of the chemical. Using lucidin-3-O-primeveroside (LuP), lucidin-modified bases formed by its active form were exhaustively searched using this new method. Various DNA adducts, including Luc-N ²-dG and Luc-N ⁶-dA, were identified in the kidneys of rats given LuP. Together with measurement of 8-hydroxydeoxyguanosine (8-OHdG) levels, the combined application of this new method with a reporter gene mutation assay was performed to clarify renal carcinogenesis induced by madder color (MC) that includes LuP and alizarin (Alz) as constituent agents. A DNA adductome map derived from MC-treated rats was almost identical to that of LuP-treated rats, but not Alz-treated rats. Although 8-OHdG levels were elevated in MC- and Alz-treated rats, significant increases in gpt and Spi^? mutant frequencies were observed only in MC- and LuP-treated rats. In addition, the spectrum of gpt mutants in MC-treated rats showed almost the same pattern as those in LuP-treated rats. The overall data suggest that LuP may be responsible for MC-induced carcinogenicity and that the proposed methodology is appropriate for exploring and understanding mechanisms of chemical carcinogenesis.

Modulation of Benzene or Naphthalene Binding to Palladium Cluster Sites by the Backside‐Ligand Effect

The backside‐ligand modulation strategy to enhance the substrate binding property of Pd clusters is reported. The benzene or naphthalene binding ability of Pd₃ or Pd₄ clusters is enhanced significantly by the backside cyclooctatetraene ligand, leading to the formation of the first solution‐stable benzene‐ or naphthalene Pd clusters. The present results imply that the ligand design of the metal clusters, especially for the backside ligand of the metal cluster site, is crucial to acquire a desired reactivity of metal clusters.     

High Catalytic Activity of Heteropolynuclear Cyanide Complexes Containing Cobalt and Platinum Ions: Visible‐Light Driven Water Oxidation

A near‐stoichiometric amount of O₂ was evolved as observed in the visible‐light irradiation of an aqueous buffer (pH 8) containing [Ru^II(2,2′‐bipyridine)₃] as a photosensitizer, Na₂S₂O₈ as a sacrificial electron acceptor, and a heteropolynuclear cyanide complex as a water‐oxidation catalyst. The heteropolynuclear cyanide complexes exhibited higher catalytic activity than a polynuclear cyanide complex containing only Co^III or Pt^IV ions as C‐bound metal ions. The origin of the synergistic effect between Co and Pt ions is discussed in relation to electronic and local atomic structures of the complexes.