Rare-earth chromium citrates as precursors for rare-earth chromites: lanthanum biscitrato chromium(III) dihydrate, La[Cr(C6H5O7)2]·2H

The thermal decomposition of lanthanum biscitrato chromium(III) dihydrate has been studied in static air and dynamic argon atmospheres. The complex decomposes in four steps: dehydration, decomposition of the citrate to an intermediate oxycarbonate, formation of LaCrO4(V) from oxycarbonate, and finally decomposition of LaCrO4(V) to LaCrO3. Formation of LaCrCrO4(V) requires the presence of oxygen The decomposition behaviour of a mechanical mixture of lanthanum citrate hydrate and chromium citrate hydrate was compared with that of the citrato complex. Both the starting material and the intermediates were characterized by X-ray diffraction, IR electronic and ESR spectroscopy, surface area and magnetic susceptibility measurements, as well as by chemical analysis. A scheme is proposed for the decomposition of lanthanum biscitrato chromium(III) dihydrate in air. LaCrO3 can be obtained at temperatures as low as 875 K by isothermal decomposition of the complex.

Synthesis of Diversified Thioethers,1-Aroylalkylisoquinolin-1-yl Thioethers, by Electrophilic S-Alkylation of 3-Phenyl Isoquinoline-1(2H)-thione

A mild and efficient method for the synthesis of thioethers has been developed. The 3-phenylisoquinoline-1(2H)-thione underwent S-alkylation to afford structurally diverse sulfides in high yield.

4-Azidomethyl-7-methyl-2-oxo-2H-chromene-6-sulfonyl azide

In the title compound, C11H8N6O4S, the plane of the coumarin aromatic ring is twisted by 17.2 (2)degrees with respect to the plane of the azide group bound to the methylene substituent, whereas it is twisted by 83.2 (2)degrees to the plane of the azide attached to the sulfonyl group. The crystal structure is stabilized by weak C-H center dot center dot center dot O interactions, leading to the formation of dimers with R-2(2)(12) graph-set motifs. These dimers are further linked by weak S-O center dot center dot center dot pi and pi-pi contacts centroid-centroid distance = 3.765 (2) angstrom], leading to the formation of a layered structure.

Orientational Order of Liquid-Crystalline 4-Alkyl-N-(p-cyanophenyl)piperidines by 2H and 13C NMR Spectroscopies

The orientational order of nematic 4-alkyl-N-(4-cyanophenyl) piperidines (I) has been determined from H-2 and C-13 NMR spectra. Molecular-order parameters are derived from the carbon-13 chemical shift of the cyano carbon atom in the nematic and the isotropic phases; the sign of the diamagnetic anisotropy is positive. Deuterium quadrupolar splittings from the partially deuterated piperidine ring of I are then related to various C-D bonds.

Synthesis of layered MoOPO4 center dot 2H(2)O and investigation of its intercalation chemistry

We describe in this paper the synthesis and characterization of a new layered phosphate, MoOPO4 . 2H(2)O (I), and its intercalation chemistry. The phosphate I, crystallizing in a tetragonal structure (a = 6.375(7), c = 7.80(1) Angstrom, and Z = 2) similar to that of VOPO4 . 2H(2)O, has been synthesized by the reduction of MoO2(HPO4). H2O (II) using ethylene glycol in an CH3CN medium at similar to 60 degrees C. Interestingly, I could be readily oxidized back to II using Br-2 in CH3CN at room temperature. Considering the close structural relationship existing between I and II, it is likely that the reduction and oxidation of the phosphates proceed by a topotactic mechanism. I is a novel layered host intercalating a variety of organic bases such as n-alkylamines, pyridine, and aniline, mainly through an acid-base interaction. Unlike VOPO4 . 2H(2)O, I does not exhibit reductive intercalation reactivity.

Preparation of the layered double hydroxide (LDH) LiAl2(OH)(7)center dot 2H(2)O, by gel to crystallite conversion and a hydrothermal method, and its conversion to lithium aluminates

A layered double hydroxide (LDH) with chemical composition LiAl2(OH)(7) . 2H(2)O was prepared via a wet chemical route of gel to crystallite (G-C) conversion at 80 degrees C involving the reaction of hydrated alumina gel, Al2O3.yH(2)O (80 < y < 120) with LiOH (Li2O/Al2O3 greater than or equal to 0.5) in presence of hydrophilic solvents such as ethanol under refluxing conditions. The hydrothermal synthesis was carried out using the same reactants by heating to less than or equal to 140 degrees C in a Teflon-lined autoclave under autogenerated pressure (less than or equal to 20 MPa). Transmission electron microscopy showed needle-shaped aggregates of size 0.04-0.1 mu m for the gel to crystallite conversion product, whereas the hydrothermal products consisted of individual lamellar crystallites of size 0.2-0.5 mu m with hexagonal morphology. The LDH prepared through the gel to crystallite conversion could be converted into LiAl(OH)(4) . H2O or LiAl(OH)(3)NO3 . H2O by imbibition of LiOH or LiNO3, respectively, under hydrothermal conditions. Thermal decomposition of LDH above 1400 degrees C gave rise to LiAl5O8 accompanied by the evaporation of Li2O. LiAl(OH)(4) . H2O and LiAl(OH)(3)NO3 . H2O decomposed in the temperature range 400-1000 degrees C to alpha- or beta-LiAlO2. The compositional dependence of the product, the intermediate phases formed during the heat treatment and the possible reactions involved are described in detail.

3-(2-Bromoacetyl)-6-fluoro-2H-chromen-2-one

The non-H atoms of the title compound, C(11)H(6)BrFO(3), are essentially coplanar (r.m.s. deviation for all non-H atoms = 0.074 angstrom). In the crystal, the molecules are linked by C-H center dot center dot center dot O and C-H center dot center dot center dot Br interactions.

Critical behavior at depinning of driven disordered vortex matter in 2H-NbS2

We report unusual jamming in driven ordered vortex flow in 2H-NbS2. Reinitiating movement in these jammed vortices with a higher driving force and halting it thereafter once again with a reduction in drive leads to a critical behavior centered around the depinning threshold via divergences in the lifetimes of transient states, validating the predictions of a recent simulation study Reichhardt and Olson Reichhardt, Phys. Rev. Lett. 103, 168301 (2009)] which also pointed out a correspondence between plastic depinning in vortex matter and the notion of random organization proposed Corte et al., Nat. Phys. 4, 420 (2008)] in the context of sheared colloids undergoing diffusive motion.

Optical Properties of 1P State Electron Bubbles in Liquid Helium-4

When an electron is injected into liquid helium, it forces open a cavity that is free of helium atoms (an electron bubble). If the electron is in the ground 1S state, this bubble is spherical. By optical pumping it is possible to excite a significant fraction of the electron bubbles to the 1P state; the bubbles then lose spherical symmetry. We present calculations of the energies of photons that are needed to excite these 1P bubbles to higher energy states (1D and 2S) and the matrix elements for these transitions. Measurement of these transition energies would provide detailed information about the shape of the 1P bubbles.

Rare-earth carboxylates, Ln(2)(III)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O Ln = Ce, Pr and Nd]: synthesis, structure and properties

A new series of inorganic-organic hybrid framework compounds, Ln(2)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O, (Ln = Ce, Pr and Nd), have been prepared employing a hydrothermal method. Malic acid and fumaric acid form part of the structure. The malate units connect the lanthanide centers forming Ln-O-Ln two-dimensional layers, which are cross-linked by the fumarate units forming the three-dimensional structure. Extra framework water molecules form a dimer and occupy the channels. The water molecules can be reversibly adsorbed. The dehydrated structure did not show any differences in framework structure/ connectivity. The presence of lattice water provides a pathway for proton conductivity. Optical studies suggest an up-conversion behavior involving more than one photon for a neodymium compound.

Cooperative properties of lipid bilayers : collective director fluctuations and the effects of hydrophobic mismatch in protein/lipid membrane systems

Cooperative director fluctuations in lipid bilayers have been postulated for many years. ^2H-NMR T_1^(-1), T_(1P)^(-1) , and T_2^(-1); measurements have been used identify these motions and to determine the origin of increased slow bilayer motion upon addition of unlike lipids or proteins to a pure lipid bilayer.

The contribution of cooperative director fluctuations to NMR relaxation in lipid bilayers has been expressed mathematically using the approach of Doane et al.^1 and Pace and Chan.^2 The T_2^(-1)’s of pure dimyristoyllecithin (DML) bilayers deuterated at the 2, 9 and 10, and all positions on both lipid hydrocarbon chains have been measured. Several characteristics of these measurements indicate the presence of cooperative director fluctuations. First of all, T_2^(-1) exhibits a linear dependence on S2/CD. Secondly, T_2^(-1) varies across the ^2H-NMR powder pattern as sin^2 (2, β), where , β is the angle between the average bilayer director and the external magnetic field. Furthermore, these fluctuations are restricted near the lecithin head group suggesting that the head group does not participate in these motions but, rather, anchors the hydrocarbon chains in the bilayer.

T_2^(-1)has been measured for selectively deuterated liquid crystalline DML hilayers to which a host of other lipids and proteins have been added. The T_2^(-1) of the DML bilayer is found to increase drastically when chlorophyll a (chl a) and Gramicidin A' (GA') are added to the bilayer. Both these molecules interfere with the lecithin head group spacing in the bilayer. Molecules such as myristic acid, distearoyllecithin (DSL), phytol, and cholesterol, whose hydrocarbon regions are quite different from DML but which have small,neutral polar head groups, leave cooperative fluctuations in the DML bilayer unchanged.

The effect of chl a on cooperative fluctuations in the DML bilayer has been examined in detail using ^2H-NMR T_1^(-1), T_(1P)^(-1) , and T_2^(-1); measurements. Cooperative fluctuations have been modelled using the continuum theory of the nematic state of liquid crystals. Chl a is found to decrease both the correlation length and the elastic constants in the DML bilayer.

A mismatch between the hydrophobic length of a lipid bilayer and that of an added protein has also been found to change the cooperative properties of the lecithin bilayer. Hydrophobic mismatch has been studied in a series GA' / lecithin bilayers. The dependence of 2H-NMR order parameters and relaxation rates on GA' concentration has been measured in selectively deuterated DML, dipalmitoyllecithin (DPL), and DSL systems. Order parameters, cooperative lengths, and elastic constants of the DML bilayer are most disrupted by GA', while the DSL bilayer is the least perturbed by GA'. Thus, it is concluded that the hydrophobic length of GA' best matches that of the DSL bilayer. Preliminary Raman spectroscopy and Differential Scanning Calorimetry experiments of GA' /lecithin systems support this conclusion. Accommodation of hydrophobic mismatch is used to rationalize the absence of H_(II) phase formation in GA' /DML systems and the observation of H_(II) phase in GA' /DPL and GA' /DSL systems.

1. J. W. Doane and D. L. Johnson, Chem. Phy3. Lett., 6, 291-295 (1970). 2. R. J. Pace and S. I. Chan, J. Chem. Phy3., 16, 4217-4227 (1982).

High-density comparative BAC mapping in the black muntjac (Muntiacus crinifrons): Molecular cytogenetic dissection of the origin of MCR 1p+4 in the X1X2Y1Y2Y3 sex chromosome system

The black muntjac (Muntiacus crinifrons, 2n = 8 female/9 male) is a critically endangered mammalian species that is confined to a narrow region of southeastern China. Male black muntjacs have an astonishing X1X2Y1Y2Y3 sex chromosome system, unparalleled i