Solvation of uranyl(II) and europium(III) cations and their chloro complexes in a room-temperature ionic liquid. A theoretical study of the effect of solvent "humidity"

We report a molecular dynamics study of the solvation of the UO2(2+) and Eu3+ cations and their chloro complexes in the [BMI][PF6][H2O] "humid" room-temperature ionic liquid (IL) composed of 1-butyl-3-methylimidazolium+ and PF6- ions and H2O in a 1:1:1 ratio. When compared to the results obtained in dry [BMI][PF6], the present results reveal the importance of water. The "naked" cations form UO2(H2O)5(2+) and Eu(H2O)9(3+) complexes, embedded in a shell of 7 and 8 PF6- anions, respectively. All studied UO2Cln(2-n) and EuCln(3-n) chloro complexes remain stable during the dynamics and coordinate additional H2O molecules in their first shell. UO2Cl4(2-) and EuCl6(3-) are surrounded by an "unsaturated" water shell, followed by a shell of BMI+ cations. According to an energy component analysis, the UO2Cl4(2-) and EuCl6(3-) species, intrinsically unstable toward dissociation, are more stable than their less halogenated analogues in the IL solution, due to the solvation forces. The different chloro species also interact better with the humid than with the dry IL, which hints at the importance of solvent humidity to improve their solubility. Humidity markedly modifies the local ion environment, with major consequences as far as their spectroscopic properties are concerned. We finally compare the aqueous interface of [BMI][PF6] and [OMI][PF6] ionic liquids, demonstrating the importance of imidazolium substituents (N-butyl versus N-octyl) to the nature of the interface and miscibility with water.     

Peering into the self-assembly of surfactant templated thin-film silica mesophases

It is now recognized that self-assembly is a powerful synthetic approach to the fabrication of nanostructures with feature sizes smaller than achievable with state of the art lithography and with a complexity approaching that of biological systems. For example, recent research has shown that silica/surfactant self-assembly combined with evaporation (so-called evaporation induced self-assembly EISA) can direct the formation of porous and composite thin-film mesostructures characterized by precise periodic arrangements of inorganic and organic constituents on the 1-50-nm scale. Despite the potential utility of these films for a diverse range of applications such as sensors, membranes, catalysts, waveguides, lasers, nano-fluidic systems, and low dielectric constant (so-called low k) insulators, the mechanism of EISA is not yet completely understood. Here, using time-resolved grazing incidence small-angle X-ray scattering (GISAXS) combined with gravimetric analysis and infrared spectroscopy, we structurally and compositionally characterize in situ the evaporation induced self-assembly of a homogeneous silica/surfactant/solvent solution into a highly ordered surfactant-templated mesostructure. Using CTAB (cetyltrimethylammonium bromide) as the structure-directing surfactant, a two-dimensional (2-D) hexagonal thin-film mesophase (p6mm) with cylinder axes oriented parallel to the substrate surface forms from an incipient lamellar mesophase through a correlated micellar intermediate. Comparison with the corresponding CTAB/water/alcohol system (prepared without silica) shows that, for acidic conditions in which the siloxane condensation rate is minimized, the hydrophilic and nonvolatile silicic acid components replace water maintaining a fluidlike state that avoids kinetic barriers to self-assembly.     

Synthèse d'homologues de la (–)--(1R,2S)-norephedrine

Synthesis of (–)-(1R,2S)-Norephedrine Homologues The amino function of esters of some simple natural amino acids I is blocked in the form of a cyanoenamine by means of 2-oxocyclopentanecarbonitrile, so that the corresponding cyanoenamino esters II are obtained. The reaction of a disubstituted lithium amide with II leeds to the cyanoenamino-amides VI . The amide function present in VI is then transformed into an aromatic ketone by means of phenyllithium, to give the (benzoylalkyl)aminocyclopentenecarbonitriles VII . Reduction of Compounds VII with NaBH₄ in EtOH ?80° affects only the keto function and leads to the [(α-hydroxybenzyl)alkyl]amino-cyclopentenecarbonitriles VIII . The amino function is then deprotected by acid hydrolysis to give the amino-alcohols IX with yields close to 50%; in every amino-alcohol IX , the erythro isomer, homologous to natural (–)-(1R,2S)-norephedrine is the more abundant or the single product. All the polyfunctional compounds prepared conserve optical activity; it has been demonstrated that the amino-alcohols IX are pure enantiomers and that no racemisation lakes place at any step of their synthesis.     

Asymmetric Total Synthesis of (11R, 12S, 13S, 9Z, 15Z)-9, 12, 13-Trihydroxyoctadeca-9, 15-dienoic Acid,a self-defensive agent against rice-blast disease

The Diels-Alder adduct of furan and 1-cyanovinyl (1′R)-camphanate was converted into methyl [(tert-butyl)-dimethylsilyl 5-deoxy-2, 3-O-isopropylidene-β-L -ribo-hexofuranosid] uronate ((+)- 4 ). Reduction with diisobutyl-aluminium hydride gave the corresponding aldehyde which was condensed with the ylide derived from triphenyl-(propyl)phosphonium bromide to give (1R, 2S, 3S, 4S)-1-[(tert-butyl)dimethylsilyloxy]tetrahedro-2, 3-(isopropyl-idenedioxy)-4-[(Z)-pent-2′ -enyl]furan ((+)- 7 ). Removal of the silyl protective group gave a mixture of the corresponding furanose that underwent Wittig reaction with the ylide derived from [8-(methoxycarbonyl)-octyl]triphenylphosphonium bromide to yield methyl (11R, 12S, 13S, 9Z, 15Z)-13-hydroxy-11, 12-(isopropylidene-dioxy)octadeca-9, 15-dienoate ((?)- 9 ). Acidic hydrolysis, then saponification afforded (11R, 12S, 13S, 9Z, 15Z)-11, 12, 13-trihydroxyoctadeca-9, 15-dienoic acid ( 1 ).     

Crystal structure of the 1 : 1 : 6 complex between 18-crown-6, hydroquinone and water

Hydroquinone forms a 1 : 1 : 6 complex with 18-crown-6 and water. Crystals of this complex are monoclinic, space groupP2₁/a witha = 14.289(1),b = 7.972(1),c = 11.596(1) Å, = 97.72(1)°,Z = 2,D _c = 1.22 g cm^–3. The hydroquinone and crown ether molecules lie on centres of symmetry with the crown in theD _3d conformation. The water molecules act as a bridge between hydroquinone and the crown ether. The structure consists of molecules linked by a 3-dimensional network of hydrogen bonds: the hydroquinone and two water molecules lie roughly in the (001) plane; the crown ether and four water molecules form bipyramidal structures which are stacked in layers alternating with the previous planes.     

An opened route to 1,3-dimethylenecyclobutanes via sequential ruthenium-catalyzed [2 + 2] cycloaddition of allenyl boronate and palladium Suzuki coupling

The regioselective head-to-head [2 + 2] cyclodimerization of allenyl boronate catalyzed by the ruthenium catalyst [Cp*RuCl(COD)] leads to a novel diboronated 1,3-dimethylenecyclobutane. Consecutive palladium-catalyzed C-C couplings open a route to novel disubstituted 1,3-dimethylenecyclobutane species. The X-ray crystalline structure of the phenyl-substituted 1,3-dimethylenecyclobutane is provided.     

Efficient mutation detection in MEN1 gene using a combination of single-strand conformation polymorphism (MDGA) and heteroduplex analysis

For facilitated genotypic analysis of multiple endocrine neoplasia type 1 (MEN1), a familial syndrome associated with tumors of the parathyroid and neuroendocrine tissues, we developed two screening methods, heteroduplex mutation assay (HMA) and mutation detection gel analysis (MDGA), both based on electrophoretic discrimination of polymerase chain reaction (PCR) products, to detect the mutations. Forty-three genomic DNA samples were used for the evaluation of these techniques. The whole coding region of MEN1 was PCR-amplified with fluorescent primers and then denatured/renatured before electrophoresis on an automated sequencer. 100% of the mutations were detected, subsequently confirmed and identified by sequencing. "Negative" samples were used to evaluate the specificity and reproducibility of the two techniques. The combination of the two methods allows high throughput cost-effective mutation screening which is less laborious than systematic sequencing of the whole coding region of MEN1. Together, these methods provide an efficient screen for MEN1 mutations.     

Structural characterization of 2-aminobenzamide-derivatized oligosaccharides using a matrix-assisted laser desorption/ionization two-stage time-of-flight tandem mass spectrometer

Oligosaccharides were derivatized by reductive amination using 2-aminobenzamide (2-AB) and analyzed by matrix-assisted laser desorption/ionization two-stage time-of-flight (MALDI-TOF/TOF) tandem mass spectrometry (MS/MS) in the positive ion mode. The major signals were obtained under these conditions from the [M+Na]+ ions for all 2-AB-derivatized oligosaccharides. A systematic study was conducted on a series of 2-AB-derivatized oligosaccharides to allow rationalization of the fragmentation processes. The MALDI-TOF/TOF-MS/MS spectra of the [M+Na]+ ions of 2-AB-derivatized oligosaccharides were dominated by glycosidic cleavages. These fragments originating both from the reducing and the non-reducing ends of the oligosaccharide yield information on sequence and branching. Moreover, the MALDI-TOF/TOF-MS/MS spectra were also characterized by abundant cross-ring fragments which are very informative on the linkages of the monosaccharide residues constituting these oligosaccharides. MALDI-TOF/TOF-MS/MS analysis of 2-AB-derivatized oligosaccharides, by providing structural information at the low-picomole level, appears to be a powerful tool for carbohydrate structural analysis.     

Growth and Characteristics of Nd^3＋：GdAl3（BO3）4 Crystal

Nd^3 :GdAl3(BO3)4(NGAB) crystal with the size of 30 mm was grown from the solvent system of K2O-Gd2O3-MoO3-B2O3 by combining accelerated seed rotation technology with medium seeded solution growth (MSSG) method,and its crystal structure has been determined by X-ray powder diffraction.It crystallizes in the trigonal system,space group R32 with a=9.2743(2),c=7.2438(1)A,V=538A^3,Z=3and Dc=4.379g/cm^3,The absorption and emission spectra of NGAB in the function of σ and π polarizations at room temperature have been measured.UV generation tuneable in 378-382nm,green(531nm) generation and blue generation tuneable in 436-443 nm as well as red(669)nm generation by self-frequency changing were obtained with the oupput of 105, 119.5,445and 19μJ/pulse,respectively,when the crystal was pumped by a dye laser.