Study on the electronic effect on coordinating donors in heptacoordinate trichlorogermanes

Trichloro[tris(2,5-dimethoxyphenyl)methyl]germane (1a), trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]germane (1b), and trichloro[tris(2-methoxy-5-trifluoromethylphenyl)methyl]germane (1c) were synthesized. X-ray crystallographic analyses of 1a-c revealed their heptacoordinate geometries around the germanium atoms. The interatomic distances between the oxygen atoms and the central germanium atoms in the crystalline state were not significantly affected by change of functional groups on the benzene rings, while the optimized structures by theoretical calculations and Atoms in Molecules (AIM) analysis indicated linear relationship between the donating ability of functional groups and the O?Ge interatomic interactions.     

Indium-catalyzed 2-alkenylation of 1,3-dicarbonyl compounds with unactivated alkynes

1,3-Dicarbonyl compounds add to unactivated alkynes in the presence of a catalytic amount of indium(III) trifluoromethanesulfonate in high to excellent yield to give 2-alkenylated 1,3-dicarbonyl compounds with exclusive regioselectivity as to the position of C-C bond formation on the acetylene moiety. In most of the cases, the reaction requires less than 1-mol % loading of the catalyst and does not require solvent. The reaction tolerates a wide variety of functional groups including ester, ether, allylic halide, furan, thiophene, and protected amine. Experimental and theoretical studies suggested that the reaction proceeds via a concerted carbometalation reaction of an indium(III) enolate with the acetylene, where indium-acetylene interaction is important.     

A method for measuring semi- and non-volatile organic halogens by combustion ion chromatography

Recent studies have shown that various semi- and non-volatile organohalogen compounds are ubiquitous in the environment: these include halogenated dioxins including chlorinated dioxins, other persistent organic pollutants (POPs), brominated flame retardants (BFRs), and perfluorooctane sulfonate (PFOS). However, monitoring and assessment of these compounds by the analyses of individual compounds and their isomers is onerous because of their low environmental concentrations and large number of compounds. In this study, we have developed a new method that is capable of screening and monitoring an array of organohalogen compounds efficiently by combustion ion chromatography (CIC) - the new analyzer that serially connects combustion furnace and ion chromatograph. Analyzer performance was evaluated in terms of its applicability, reproducibility, and sensitivity as limit of detection (LOD). Recoveries of organochlorine, organobromine, and organoiodine compounds by the CIC were between 97 and 105%; those of organofluorine compounds were from 86 to 91%. In all cases, the relative standard deviation of five analyses was 4% or smaller. The analyzer would exhibit good sensitivity for various environmental matrices (e.g., 2.8-31ng-X/g-soil, 1.4-16ng-X/L-water, and 9.2-100ng-X/m3N-gas). The method is fast and can provide information regarding the occurrence of organohalogen compounds within 1 or 2 days after sampling. Applicability of the new method for the assessment of contamination in flue gas and fly ash was also demonstrated. Our results show that the method is efficient to investigate emission sources and areas contaminated by organohalogen compounds.     

High-throughput solid-phase extraction of metal ions using an iminodiacetate chelating porous disk prepared by graft polymerization

A chelating porous sheet for use in solid-phase extraction was prepared by radiation-induced graft polymerization and subsequent chemical modifications. An epoxy-group-containing vinyl monomer was graft-polymerized onto a porous sheet made of polyethylene. The produced epoxy group of the graft chain was converted into an iminodiacetate group. The chelating porous sheet with a density of the iminodiacetate group of 2.1 mol/kg was cut into disks 13 mm in diameter to fit an empty cylindrical cartridge with a capacity of 6 mL. Breakthrough curves using the chelating-porous-disk-packed cartridge overlapped irrespective of the flow rate of the solution ranging up to 1500 mL/h because of negligible diffusional mass-transfer resistance of the copper ions to the iminodiacetate group of the graft chain.     

Functionalization of silicon surfaces with catalytically active Pd complexes and application to the aerobic oxidation of benzylic alcohols

A single-crystal silicon surface was modified with a bisoxazoline-Pd molecular layer and utilized as a highly efficient (catalyst turnover number up to 780,000, 110 degrees C, 72 h) and recyclable catalyst in the aerobic oxidation of benzylic alcohols.     

Reconstitution of bacterial photosynthetic unit in a lipid bilayer studied by single-molecule spectroscopy at 5 K

As a model of photosynthetic unit (PSU), self-assembled aggregates of pigment-protein complexes from photosynthetic bacteria were prepared in a lipid bilayer by reconstitution of the light-harvesting 2 (LH2) complex and light-harvesting 1-reaction center (LH1-RC) complex through detergent removal of their micelles in the presence of lipids. By performing polarization-controlled fluorescence and fluorescence-excitation spectroscopy on single aggregates at a temperature of 5 K, the composition of individual aggregates was determined and excitation energy transfer (EET) between constituent complexes was observed. LH2 and LH1-RC from a bacterium, Rhodobacter (Rb.) sphaeroides, were found to form a trimeric aggregate in which EET takes place from one LH2 to two LH1-RCs. In contrast, a heterodimer of LH2 and LH1-RC in which EET works was found to assemble from a combination of complexes of different bacterial species, that is, LH2 from Rb. sphaeroides and LH1-RC from Rhodopseudomonas (Rps.) palustris.     

Dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of a quadruple bonded Mo2 core

We developed dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of the Mo(2) core. A 2,4,6-triisopropylbenzoate-supported Mo(2) complex acts as a catalyst for radical addition reactions of polyhaloalkanes to 1-alkenes and cyclopentene, while amidinate- and guanidinate-supported Mo(2) clusters are effective catalysts for the radical polymerization reaction of methyl methacrylate.