Subwatt threshold cw Raman fiber-gas laser based on H2-filled hollow-core photonic crystal fiber

We report on what is, to our knowledge, the first cw pumped Raman fiber-gas laser based on a hollow-core photonic crystal fiber filled with hydrogen. The high efficiency of the gas-laser interaction inside the fiber allows operation in a single-pass configuration. The transmitted spectrum exhibits 99.99% of the output light at the Stokes wavelength and a pump power threshold as low as 2.25 W. The study of the Stokes emission evolution with pressure shows that highly efficient Raman amplification is still possible even at atmospheric pressure. The addition of fiber Bragg gratings to the system, creating a cavity at the Stokes wavelength, reduces the Raman threshold power below 600 mW.     

Capacity Titration Technique for Determining the Solid Diffusion Coefficient of Intercalary Species within Insertion-host Materials

Investigation on the solid diffusion process of intercalary species within insertion-host materials plays an important role in the energy storage and output of secondary batteries1. To determine the solid diffusion coefficient, several electrochemical techniques have been developed such as galvanostatic intermittent titration (GITT)2,3, electrochemical impedance spectroscopy (EIS)4,5, potential intermittent titration technique (PITT)6, and potential step chronoamperometry (PSCA)7, potenti…     

Carboxylate complexation by 1,1'-(1,2-phenylene)bis(3-phenylurea) in solution and the solid state

A simple bis-urea containing anion receptor, synthesised from ortho-phenylenediamine, has been shown to have excellent selectivity for carboxylates in solution, with a crystal structure elucidation of the benzoate complex showing four hydrogen bonds between the receptor and anion in the solid state.     

Synthesis, structure and characterization of the trinuclear copper (Ⅰ) complex [Cu_3(μ_3Br)_2(dppm)_3]Br

The novel trinuelear copper(I) complex [Cu3(μ3-Br)2(dppm)3]Br has been obtained by reaction of bis(diphenyl-phosphino)methane (dppm) with cupric bromide. The title complex was characterized by single-crystal X-ray analysis, elemental analysis, molecular weight determination, 31P NMR and its conductivity was also measured. The [Cu3(dppm)3Br2] cation consists of a triangular array of copper atoms, with dppm ligands (Ph2PCH2PPh2) bridging each edge of the triangle and two triply bridging Br groups bound to the two faces of the Cu3 unit. Crystallographic data: monoclinic, space group P21/c, a = 1.4739(4) , b = 1.7708(5), c = 2.8395(8) nm, β= 97.16(3)°, V = 7.353nm3, Z = 4,F(000)= 3296, Dcalc = 1.472 g/cm3, μ= 26.478 cm-1, R = 0.06, Rw = 0.08, 4654 reflections observed with I > 3σ(I).     

2-amidopyrroles and 2,5-diamidopyrroles as simple anion binding agents.

Four new 2-amidopyrroles and 2,5-diamidopyrroles have been synthesized and their anion complexation properties investigated. The crystal structures of these receptors have been elucidated and reveal hydrogen bonding in the solid state leading to dimer and network formation. Selectivity for oxo-anions has been demonstrated by (1)H NMR titration techniques.     

Dimeric supramolecular motifs of two carboxylate–guanidinium compounds

The structures of N‐benzyl‐N′‐{6‐[(4‐carboxylatobenzyl)aminocarbonyl]‐2‐pyridylmethyl}guanidinium, C₂₃H₂₃N₅O₃, (I), and N‐[2‐(benzylaminocarbonyl)ethyl]‐N′‐{6‐[(4‐carboxylatobenzyl)aminocarbonyl]‐2‐pyridylmethyl}guanidinium monohydrate, C₂₆H₂₈N₆O₄·H₂O, (II), both form three‐dimensional supramolecular hydrogen‐bonded networks based on a dimeric primary synthon involving carboxylate–guanidinium linkages. The differences in the geometries and hydrogen‐bonding connectivities are driven by the additional methylpropionamide group and water of crystallization of (II).     

A new flavone glycoside from Cancrinia discoidea(Ledeb.) Poljak

<正>A new flavone glucoside,selagin-7-O-(6″-O-acetyl-)-β-D-glycoside,has been isolated from Cancrinia discoidea(Ledeb.) Poljak.Its structure was identified by spectroscopic methods,2D NMR and MS.Compounds exhibited activity of anti-inflammatory in vitro.     

Study on the Methyl Migration of 10-Methoxy-5,10-dihydrophenophosphazine 10-oxide

The title compound (1) was treated with NaH at room temperature in anhydrous DMF to give a sodium salt (containing nitrogen anion)which could shift the methyl group from oxygen to nitrogen atom to form N-methyl phosphinic acid as the reaction temperature was increased to 120 ℃.Three nitro derivatives containing 5,10-dihydrophenophosphazine ring system were prepared for the investigation on the above reaction mechanism which would be possible regarded as a special inter-molecular substitution.viz.,the nucleophilic nitrogen anion from one molecule of 1 attacked the cabon atom of the O-methyl of another 1.In addition,the chemical structures of seven compounds containing 5,10-dihydrophenophosphazine ring system involved in the experiment were confirmed by IR,^1 H NMR,^31P NMR and mass spectroscopy.     

Transformations of lignans. Part 11: Oxidation of diphyllin with hypervalent iodine reagents and reductive reactions of a resulting 1-methoxy-1-aryl-4-oxonaphthalene lactone

Treatment of diphyllin 4 with phenyliodonium diacetate (PIDA) in methanol affords a 1-methoxy-1-aryl-4-oxonaphthalene lactone 6. Reduction of 6 with lithium aluminium hydride yields, inter alia, 3,4-dihydrodiphyllin 13, while reaction with sodium in ethanol yields 8 as a major product. These reactions illustrate that selective oxidation followed by reduction provides a facile route for the conversion of a 1-arylnaphthalene lactone to novel functionalised naphthalene and dihydronaphthalene derivatives. Of particular interest is that the oxidation indirectly activates the methylene position (C-10) of the γ-lactone, which may then potentially be substituted to give a new series of lignans. Reaction of 6 with hydroxylamine and benzyloxyamine also proceeds by way of initial attack at C-10.     

Highly-functionalised difluorinated (hydroxymethyl)conduritol analogues via the Diels-Alder reactions of a difluorinated dienophile

A difluorodienophile, synthesised using a Stille coupling reaction underwent tin(iv)-catalysed cycloaddition with three furans to afford oxa[2.2.1]bicycloheptenes in good yield. Reduction of ester and carbamate carbonyl groups and diol protection as the acetonide set the stage for palladium-catalysed hydrostannylation in two cases. Treatment of the stannanes with methyllithium triggered ring-opening to afford highly-functionalised difluorinated cyclohexenols which could be deprotected to afford (hydroxymethyl)conduritol analogues.