Titanium(III) chloride and electrochemical reduction of pyrazine,quinoxaline and triazine derivatives and of their salts

The reduction of pyrazine, quinoxaline and triazine derivatives by titanium(III) chloride leads to di- or tetrahydrogenated compounds. High yields of tetrahydro compounds are also obtained through the reduction of quinoxalinium salts. These results are compared with those obtained by electrochemical reduction.     

Comparison of ferroelectric domain delineation in triglycine sulphate by the etching technique and the pyroelectric laser technique. Application to the study of polarization reversal

It is shown that the well-known etch technique and the newly developed pyroelectric laser technique can reveal similar domains. However the latter technique is so fast that it appears as the best one to study problems such as nucleation and domain wall motion.

In the case of an alanine doped TGS crystal it is shown that domain wall motions started at a given nucleation field E₁ stop at some characteristic boundary lines in the crystal. To carry on the polarization reversal, we have to increase the electric field up to some higher value E₂ which is the minimum value of the nucleation field in the next area. Then a new domain is growing very rapidly by wall motions until the characteristic boundary lines of this area are reached. These lines are probably dislocation lines. It is shown that a direct side observation of domains is possible. Conical and cylindrical domains are clearly visible.     

Analyse du titane et de ses alliages par spectrométrie d'émission dans l'ultraviolet-vide

The large ultraviolet spectrograph for analysis in vacuum (VUV spectrograph) developed by ONERA and described in a previous article, has been used for multielements quantitative analysis: in pure titanium, concentrations of oxygen, nitrogen, hydrogen and carbon have been determined as well as silicon and iron impurities; in titanium-based alloys, addition metals at high concentration, Al, V, Mo, Zr, Si, have also been determined simultaneously with the gaseous elements and impurities. The analytical lines located between 200 and 2600 Å and corresponding to highly ionized atoms (II to VI) have been selected. The stability of the equipment has been tested and the repeatability of results has been investigated. This new analytical technique allows the study of various surface phenomena such as the variations in oxygen, nitrogen and carbon concentrations with a resolution in depth of a few microns. The method allows it to envisage the quantitative analysis of surface phenomena on metal films with a thickness below one micron.     

Grenzen für die Bildung lamellarer Metall‐di(arensulfonyl)amide: Drei Lithium‐Komplexe und ein Cadmium‐Komplex

Structures of Ionic Di(arenesulfonyl)amides. 6. Limits to the Formation of Lamellar Metal Di(arenesulfonyl)amides: Three Lithium Complexes and One Cadmium Complex According to low‐temperature X‐ray studies, the new compounds LiN(SO₂C₆H₄‐4‐X)₂ · 2 H₂O, where X = COOH ( 1 ) or COOMe ( 2 ), LiN(SO₂C₆H₄‐4‐CONH₂)₂ · 4 H₂O ( 3 ), and Cd[N(SO₂C₆H₄‐4‐COOH)₂]₂ · 8 H₂O ( 4 ) crystallize in the triclinic space group P1 ( 1 – 3 : Z′ = 1; 4 : Z′ = 1/2, Cd²⁺ on an inversion centre) and display almost perfectly folded anions approximating to mirror symmetry. The lithium ions in 1 – 3 have distorted tetrahedral environments respectively set up by two O=S groups drawn from different anions and two water molecules, two O=S groups of a chelating anion and two water molecules, or one O=C group and three water ligands, whereas the cation of 4 is fully hydrated to form an octahedral [Cd(H₂O)₆]²⁺ complex. The structure refinements for 3 and 4 were marred by positional disorder of the non‐coordinating N(SO₂)₂ moieties. Compounds 1 and 4 extend a previously described series of lamellar metal di(arenesulfonyl)amides where the two‐dimensional inorganic component is comprised of cations, N(SO₂)₂ groups and water molecules and the outer regions are formed by the 4‐substituted phenyl rings. Both crystal packings are governed by self‐assembly of parallel layers through exhaustive hydrogen bonding between carboxylic groups, and there is good evidence that the labile inorganic networks, generated via Li–O and hydrogen bonds in 1 or solely hydrogen bonds in 4 , are efficiently stabilized by the strong cyclic (COOH)₂ motifs within the interlayer regions. In the absence of these, the lamellar architecture is seen to collapse in 2 and 3 , where the carboxyl groups are replaced by methoxycarbonyl or carbamoyl functions and the inorganic components are segregated in parallel tunnels pervading the anion lattices.     

Zweidimensionale Polymere mit hydrophober Umhüllung: Kristallstrukturen der isostrukturellen Metallkomplexe [M{C6H4(SO2)2N}(H2O)] (M = K,Rb) und des strukturverwandten Ammoniumsalzes [(NH4){C6H4(SO2)2N}(H2O)]

Metal Salts of Benzene‐1,2‐di(sulfonyl)amine. 4. Hydrophobically Wrapped Two‐Dimensional Polymers: Crystal Structures of the Isostructural Metal Complexes [M{C₆H₄(SO₂)₂N}(H₂O)] (M = K, Rb) and of the Structurally Related Ammonium Salt [(NH₄){C₆H₄(SO₂)₂N}(H₂O)] The previously unreported compounds KZ · H₂O ( 1 ), RbZ · H₂O ( 2 ) and NH₄Z · H₂O ( 3 ), where Z^– is Ndeprotonated ortho‐benzenedisulfonimide, are examples of layered inorgano‐organic solids, in which the inorganic component is comprised of metal or ammonium cations, N(SO₂)₂ groups and water molecules and the outer regions are formed by the planar benzo rings of the anions. The metal complexes 1 and 2 were found to be strictly isostructural, whereas 3 is structurally related to them by a non‐crystallographic mirror plane ( 1 – 3 : monoclinic, space group P2₁/c, Z = 4; single crystal X‐ray diffraction at low temperatures). In each structure, the five‐membered 1,3,2‐dithiazolide heterocycle possesses an envelope conformation, the N atom lying about 40 pm outside the mean plane of the S–C–C–S moiety. The metal complexes feature two‐dimensional coordination networks interwoven with O–H…O hydrogen bonds originating from the water molecules. The metal centres adopt an irregular nonacoordination formed by five sulfonyl O atoms, two N atoms and two μ₂‐bridging water molecules; each M⁺ is connected to four different anions. When NH₄⁺ is substituted for M⁺, the metal–ligand bonds are replaced by N⁺–H…O hydrogen bonds, but the general topology of the lamella is not affected. In the three structures, the lipophilic benzo groups protrude obliquely from the surfaces of the polar lamellae and display marked interlocking between adjacent layers.     

Ein lamellarer Schichtverband auf der Grundlage von Wasserstoffbrücken und π‐Stapelung: Kristallstruktur des Lithiumkomplexes [Li{C6H4(SO2)2N}(H2O)3] und ein Vergleich mit anderen Metall(I)‐benzol‐1, 2‐di(sulfonyl)amiden

The title complex, obtained by treating ortho‐benzenedisulfonimide (HZ) with LiOH in aqueous solution, has been characterized by low‐temperature X‐ray diffraction (triclinic, space group P&1macr;, Z' = 1). The lithium cation is bonded to one sulfonyl oxygen atom and three water molecules in a distorted tetrahedral configuration [Li‐O 189.3(3)‐201.2(3) pm, O‐Li‐O 98.5(2)‐123.2(2)?]. The zero‐dimensional [Li(Z)(H₂O)₃] complexes, which display an intramolecular O(W)‐H···O hydrogen bond, are cross‐linked via five O(W)‐H···O/N/O(W) interactions and a remarkably short C‐H···O bond (H···O 217 pm, C‐H···O 170?) to form a two‐dimensional assembly comprising an internal polar lamella of metal cations, (SO₂)₂N groups and water molecules, and hydrophobic peripheral regions consisting of protruding benzo groups. In the packing, alternate carbocycles drawn from adjacent layers set up a π‐stacking array of parallel aromatic rings (intercentroid distances 349 and 369 pm, cycle spacings 331 and 336 pm). In a short survey, the currently known crystal packings of seven M^IZ · n H₂O (n ≥ 0) complexes are examined and compared.     

Phase-oriented surface segregation in an aluminium casting alloy

There have been many reports of the surface segregation of minor elements, especially Mg, into surface layers and oxide films on the surface of Al alloys. LM6 casting alloy (Al-12%Si) represents a challenging system to examine such segregation as the alloy features a particularly inhomogeneous phase structure. The very low but mobile Mg content (approximately 0.001 wt.%), and the surface segregation of modifiers such as Na, mean the surface composition responds in a complex manner to thermal treatment conditions. X-ray photoelectron spectroscopy (XPS) has been used to determine the distribution of these elements within the oxide film. Further investigation by dynamic secondary ion mass spectrometry (DSIMS) confirmed a strong alignment of segregated Na and Mg into distinct phases of the structure.     

Photocatalytic properties of Ta-doped TiO2

Ionics - This work reports the effect of tantalum (0.1–1 at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673 K in air. It was shown that addition of...     

Novel pseudo-delocalized anions for lithium battery electrolytes

A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn ? Li(+) + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research.