Determination of triazine pesticides and related compounds in environmental water by liquid chromatography-mass spectrometry.

A method for the determination of 5 triazine herbicides and 12 degradation products in environmental water samples using liquid chromatography-electrospray ionization mass spectrometry (LC/ESI/MS) has been developed. The pesticides in water were extracted with two types of solid phase: a styrene-divinylbenzene copolymer and a graphitized carbon black. Desorption solvents for the extracted compounds were acetone for the styrene-divinylbenzene copolymer and methanol for the graphitized carbon black. Overall recoveries from ground water and river water ranged from 73% to 111%. The limits of detection (LODs) were 0.2 to 28 ng l(-1). This method was applied to several ground water samples.     

Thermochromic transitions in poly(di-n-hexylsilane) films

The spectra of absorption (77–398 K) and luminescence (5 K) of poly(di-n-hexylsilane) films are studied in relation to the heating of the films above the phase transition temperature. Two new absorption bands in the region of the band of the gauche conformation are found. The position and intensity of these bands depend on the annealing temperature, annealing regime, and sample thickness. These bands are assumed to be associated with the appearance of a liquid crystalline phase in the polymer, which is determined by intermolecular interactions between neighboring polymer chains. The appearance of the liquid crystalline phase in the heat-treated polymer films is confirmed by the increase in their birefringence in comparison with the birefringence of the initial films and by the observation of a stable orientation of an E 7 nematic liquid crystal applied to the surface of an annealed sample. In addition, the absorption spectra of the films cooled after the annealing exhibit many new bands in comparison with the spectra of the initial samples. These bands are associated with the appearance in the polymer of defect states and longer segments as a result of orientation of polymer chains. The appearance of longer segments is consistent with the observation of a long-wavelength band in the luminescence spectra of the annealed samples.     

Confirmation of sable QTL that modifies the effects of the Ay allele on yellow coat color on mouse chromosome 1

F₁-A^y mice between RR (aabbCC) and C57BL/6J-A^y (A^yaBBCC) have a much darker yellow coat color than do C57BL/6J-A^y. Quantitative trait locus (QTL) analysis was carried out to identify genes responsible for the darker modification of the yellow coat color (this has been traditionally termed “sable”). A significant sable QTL was identified on chromosome 1 (Dmyaq4, LOD score 15.5 for lightness, and 13.4 for color difference), in a chromosomal position similar to that of Dmyaq2, a sable QTL previously identified in C3H/HeJ. Another significant sable QTL was identified on chromosome 4 (Dmyaq5, LOD score 5.6 for lightness, and 4.3 for color difference) near the tyrosinase-related protein 1 (Tyrp1) locus. The effect of Dmyaq5 was significant only in the presence of the RR allele at Dmyaq4, suggesting that the Dmyaq4 (as well as Dmyaq2) is a novel coat color gene that may act up-stream of Tyrp1 signaling to increase eumelanin production.     

A conducting crystal based on a single-component paramagnetic molecule, [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate)

A single-component conducting molecular crystal composed of paramagnetic copper complexes, [Cu(dmdt)2]0+, was prepared. The crystal has an unprecedented three-dimensionally packed molecular arrangement and exhibits a fairly high conductivity (1 S cm-1 at room temperature). The magnetic susceptibility measurements revealed that [Cu(dmdt)2]0+ molecule keeps most of S = 1/2 spin moments. The difference of the bond lengths between [Cu(dmdt)2]0+ and [Cu(dmdt)2]2- is consistent with the result of the molecular orbital calculation.     

Two-dimensional self-organization of phthalocyanine and porphyrin: dependence on the crystallographic orientation of Au

By immersing Au substrate into a benzene solution containing both cobalt(II) phthalocyanine (CoPc) and copper(II) tetraphenyl-21H,23H-porphine (CuTPP), a two-dimensional alternate bimolecular structure was formed on the reconstructed Au(100)-(hex) surface.     

Synthesis and two-electron redox behavior of diazuleno[2,1-a:1,2-c]naphthalenes

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.     

Ion-Pair Solvent Extraction of EDTA Anions with Tetraalkylammonium Ions in Various Organic Solvents

Summary.  The ion-pair solvent extraction behavior of ethylenediaminetetraacetate (EDTA) anion by various tetraalkylammonium ions was investigated at 25.0 ± 0.1°C. The extraction of EDTA exceeded 90% from the basic aqueous solution into the organic solvents such as n-hexane and benzene derivatives containing tri-n-octylmethylammonium chloride, but EDTA was hardly extracted from acidic solution. Among the chemical species of EDTA in aqueous solution, edta ⁴⁻ is the most extractable one. On the other hand, the extraction of EDTA was less than 1% into chloroform and 1,2-dichloroethane even from the basic aqueous solution. The effect of the structure of alkylammonium ion was also examined. Tetra-n-hexylammonium and tetra-n-octylammonium ions could not extract EDTA even from the basic aqueous solution, while the use of tri-n-octylmethylammonium and di-n-lauryldimethylammonium ions enhances the extraction of EDTA. These results suggest that the steric hindrance in the ion-pair of alkylammonium and EDTA anion in the organic phase affects the extractability of EDTA containing ion-pair. The solution structure of ion-pair in the organic phase was calculated by MMFF force field and the steric effect in the ion-pair was also suggested. From the extraction constants obtained, the possibility of the extraction separation of EDTA has been shown. Present address: Chemistry Department, Heilongjiang University, Harbin, China     

Cu(I)-catalyzed direct enantioselective cross aldol-type reaction of acetonitrile

Direct catalytic enantioselective cross aldol-type reaction of an acetate surrogate was developed using Cu alkoxide-chiral phosphine complexes as catalysts. Chemoselective activation and deprotonation of the donor substrate (acetonitrile) by the soft metal alkoxide in a strongly donating solvent (HMPA) are key to success in this reaction. Useful chemical yields and promising enantioselectivities are produced using either DTBM-SEGPHOS or a tuned BIPHEP as a chiral ligand. [reaction: see text]     

Synthetic studies of proanthocyanidins. Part 3: Stereoselective 3,4-cis catechin and catechin condensation by TMSOTf-catalyzed intramolecular coupling method

TMSOTf-catalyzed intramolecular condensation for catechin and epicatechin units are described. A potential electrophile and a nucleophile were connected with diester linkers and TMSOTf-catalyzed condensation was examined. In comparison with intermolecular catechin and catechin condensation, the intramolecular condensation required high reaction temperature and reversed 3,4-cis product was obtained. The condensed product was transformed into the natural 3,4-cis (+)-catechin-(4β→8)-(+)-catechin dimer.