Search results for "stoichiometry"
showing 10 items of 270 documents
The stoichiometry of blue vanadium doped zircon obtained by sol-gel methods
1992
Abstract In this study, Sol-Gel processes in aqueous solution were used to investigate the stoichiometry of the V/1bZrSiO 4 solid solutions achieved by this method. Compositions with a formal stoichiometric defect in: (a) ZrO 2 ([ZrO 2 ] 1−2x [SiO 2 ] [V 2 O 5 ] x ), and (b) in SiO 2 ([ZrO 2 ] [SiO 2 ] 1−2x [V 2 O 5 ] x ), x=0.02, 0.04, 0.05 and 0.10 have been prepared. X Ray Diffraction analyses in fired samples (1200°/3 days) showed that cristobalite and monoclinic zirconia appear as residual crystalline phase in (a) and (b) compositions respectively, except in sample (a) with x=0.02 in which no residual phase was detected and therefore is considered stoichiometric. This sample and sample…
Structural and hydrogenation study on the ball milled TiH2–Mg–Ni
2015
International audience; With the aim of further understanding for TieNieMg alloys and their hydrogenation behavior, powders of TiH2, Mg and Ni with the molar ratio of 3:1:2 have been mechanically milled for 10 h, 20 h, 30 h, 40 h according to the stoichiometry (TiH2)1.5Mg0.5Ni. Microstructures of the milled sample were analyzed and their hydrogenation properties as negative electrodes for Ni-MH batteries were studied. Phase change with milling time revealed the fast formation of the Ti-Mg-H FCC phase. The alloying priority among Ti, Mg and Ni was demonstrated by comparing phase compositions in different milling time. Hydrogen capacities evaluated by both solidegas reaction and electrochemic…
Coordination Chemistry of a Bis(Tetrazine) Tweezer: A Case of Host-Guest Behavior with Silver Salts
2021
The carbon-carbon cross-coupling of phenyl s-tetrazine (Tz) units at their ortho-phenyl positions allows the formation of constrained bis(tetrazines) with original tweezer structures. In these compounds, the face-to-face positioning of the central tetrazine cores is reinforced by π-stacking of the electron-poor nitrogen-containing heteroaromatic moieties. The resulting tetra-aromatic structure can be used as a weak coordinating ligand with cationic silver. This coordination generates a set of bis(tetrazine)-silver(I) coordination complexes tolerating a large variety of counter anions of various geometries, namely, PF6−, BF4−, SbF6−, ClO4−, NTf2−, and OTf−. These compounds were characterized…
Homo- and Heterobinuclear Cu2+ and Zn2+ Complexes of Ditopic Aza Scorpiand Ligands as Superoxide Dismutase Mimics
2017
Two polytopic aza-scorpiand-like ligands, 6-[7-(diaminoethyl)-3,7-diazaheptyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L1) and 6-[6′-[3,6,9-triaza-1-(2,6-pyridina)cyclodecaphan-6-yl]-3-azahexyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L2), have been synthesized. The acid–base behavior and Cu2+, Zn2+, and Cu2+/Zn2+ mixed coordination have been analyzed by potentiometry, cyclic voltammetry, and UV–vis spectroscopy. The resolution of the crystal structures of [Cu2L2Cl2](ClO4)2·1.67H2O (1), [Cu2HL2Br2](ClO4)3·1.5H2O (2), and [CuZnL2Cl2](ClO4)2·1.64H2O (3) shows, in agreement with the solution data, the formation of homobinuclear Cu2+/Cu2+ and heterobinuclear Cu2+/Zn2+ complexes. The m…
Developmental speed affects ecological stoichiometry and adult fat reserves in Drosophila melanogaster
2020
Abstract The elemental composition of organisms belongs to a suite of functional traits that change during development in response to environmental conditions. However, associations between adaptive variations in developmental speed and elemental body composition are not well understood. We compared body mass, elemental body composition, food uptake and fat metabolism of Drosophila melanogaster male fruit flies in relation to their larval development speed. Slowly developing flies had higher body carbon concentration than rapidly developing and intermediate flies. Rapidly developing flies had the highest body nitrogen concentration, while slowly developing flies had higher body nitrogen lev…
Palladium-catalyzed heteroaryl thioethers synthesis overcoming palladium dithiolate resting states inertness: Practical road to sulfones and NH-sulfo…
2018
International audience; We provide efficient synthetic access to heteroaryl sulfones in two-steps using a simple palladium-1,1'-bis [(diphenyl)phosphanyl]ferrocene catalyst to form in high yields variously functionalized heteroaromatic thioethers. Pyridinyl-containing substrates can be subsequently selectively oxidized into sulfones and NH-sulfoximines by using very mild oxidation conditions with a high functional group tolerance. In the palladium catalyzed C-S coupling of heteroaromatic thiols, reactivity limitation is attached with electron-deficient thiols. We show that this limitation can be resolved by the successful use of 2-bromoheteroarenes in the C-S coupling. We established herein…
Reaction of LiArMe6 (ArMe6= C6H3-2,6-(C6H2-2,4,6-Me3)2) with indium(I)chloride yields three m-terphenyl stabilized mixed-valent organoindium subhalid…
2016
Abstract Indium(I)chloride reacts with LiAr Me 6 ( Ar Me 6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) in THF to give three new mixed-valent organoindium subhalides. While the 1:1 reaction of InCl with LiAr Me 6 yields the known metal-rich cluster In8( Ar Me 6 )4 (1), the use of freshly prepared LiAr Me 6 led to incorporation of iodide, derived from the synthesis of LiAr Me 6 , into the structures, to afford In4( Ar Me 6 )4I2 (2) along with minor amounts of In3( Ar Me 6 )3I2 (3). When the same reaction was performed in 4:3 stoichiometry, the mixed-halide compound In3( Ar Me 6 )3ClI (4) was obtained. Further increasing the chloride:aryl ligand ratio resulted in the formation of the known mixed-halide spe…
Influence of structural elements on iron(III) chelating properties in a new series of amino acid-derived monohydroxamates
2018
Abstract A series of amino acid-derived monohydroxamate compounds A1 – A7 was synthesized and characterized for their coordination properties of Fe(III). The series varies in their skeletal lengths and compositions; some compounds lack external substituents, others are substituted with external functional amino or carboxylic groups, or alternatively inert methyl. Undertaken investigations allowed the determination of stoichiometry, stability constants and spectroscopic parameters of formed ferric complexes. Incorporation of an external functional group with a dissociable proton affects the coordination behavior; the presence of carboxylic or amino groups hampers the formation of mono-, di- …
A New Synthetic Method and Solution Equilibria for the Chlorotitanate( IV ) Anions − Evidence for the Existence of a New Species: [Ti 2 Cl 11 ] 3−
2004
TiCl3 is oxidized by SOCl2 in the presence of the appropriate amount of [NEt3Bz]Cl or [PPN]Cl [Bz = benzyl; PPN = bis(triphenylphosphanyl)iminium] to afford the corresponding salts of [Ti2Cl9]−, [Ti2Cl10]2− or [TiCl6]2−. The results of cyclic voltammetric and solution IR studies in the Ti−Cl stretching region are interpreted in terms of a rapid chloride-redistribution equilibrium between [Ti2Cl10]2− on one side and a mixture of [Ti2Cl9]− and a previously unreported [Ti2Cl11]3− species on the other side. In the solid state, however, a compound with the [PPN]3[Ti2Cl11] stoichiometry exists as a mixture of [PPN]2[Ti2Cl10] and [PPN]2[TiCl6]. The PPN salt of [Ti2Cl9]− has been structurally chara…
Bringing a Molecular Plus One: Synergistic Binding Creates Guest-Mediated Three-Component Complexes
2020
Cethyl-2-methylresorcinarene (A), pyridine (B), and a set of 10 carboxylic acids (Cn) associate to form A·B·Cn ternary assemblies with 1:1:1 stoichiometry, representing a useful class of ternary systems where the guest mediates complex formation between the host and a third component. Although individually weak in solution, the combined strength of the multiple noncovalent interactions organizes the complexes even in a highly hydrogen-bond competing methanol solution, as explored by both experimental and computational methods. The interactions between A·B and Cn are dependent on the pKa values of carboxylic acids. The weak interactions between A and C further reinforce the interactions betw…