Sol-gel deposited Sb-doped tin oxide films

The structural, electrical and optical properties of single sol-gel derived antimony-doped tin oxide (ATO) films sintered at 550°C have been measured. The reproducibility of both the preparation and the characterization procedures have been tested by a round-robin test involving eight laboratories within a Concerted European Action (CEA) project. The resistivity measured as a function of Sb content has been obtained by electric and reflectance and transmission measurements. Their differences are discussed in terms of structural and grain boundary effects. An increase of Sb content results in a decrease of the crystallite size (7.0 to 5.4 nm) and a greater influence of the grain boundary

Investigation of the Photophysical Properties of a Eu3+ Coordination Polymer Bearing an α-Nitrile Substituted β-Diketonate Ligand via Emission and Ultrafast Transient Absorption Spectroscopy

Reaction of the β-diketone ligand, 2-cyano-1,3-phenyl-1,3-propandione (LH), with hydrated EuCl3 in the presence of 1,10-phenanthroline (Phen), results in the crystallisation of a one-dimensional Eu3+ coordination polymer of formulation [Eu(Phen)(L)3]∞, formed by coordination of the nitrile group of an O,O′-bound ligand to a neighbouring metal centre. An investigation of the metal-centred emission of the polymer, both in the solid state and solution, revealed red emission characterised by relatively long-lived excited state lifetimes and high intrinsic quantum yields. However, analysis of the overall quantum yield and sensitisation efficiency reveals that ultrafast processes in the ligand potentially inhibit Eu3+ sensitisation. Further investigations into these processes using transient absorption spectroscopy suggest that substitution at the α-C position may significantly decrease sensitisation via the antenna effect

Niobium tetrahalide complexes with neutral diphosphine ligands

The reactions of NbCl4 with diphosphine ligands o-C6H4(PMe2)2, Me2PCH2CH2PMe2 or Et2PCH2CH2PEt2 in a 1:2 molar ratio in MeCN solution produced eight-coordinate [NbCl4(diphosphine)2]. [NbBr4(diphosphine)2] (diphosphine = o-C6H4(PMe2)2 or Me2PCH2CH2PMe2) were made similarly from NbBr4. X-ray crystal structures show that [NbCl4{o-C6H4(PMe2)2)2}] has a dodecahedral geometry but the complexes with dimethylene backboned diphosphines are distorted square antiprisms. The Nb-P and <P-Nb-P angles are very similar in the two types, but Nb-Cl distances are ~ 0.1Å longer in the square antiprismatic complexes. These paramagnetic (d1) complexes were also characterised by microanalysis, magnetic measurements, IR and UV-visible spectroscopy. Using a 1:1 molar ratio of NbCl4 : diphosphine (diphosphine = Me2PCH2CH2PMe2, Et2PCH2CH2PEt2, Cy2PCH2CH2PCy2 and Ph2PCH2CH2CH2PPh2) afforded [NbCl4(diphosphine)] and [NbBr4(Me2PCH2CH2PMe2)] was obtained similarly. These 1 : 1 complexes are unstable in solution, preventing X-ray crystallographic study, but based upon their diamagnetism, IR, UV-visible and 31P{1H} NMR spectra they are formulated as halide-bridged dimers [(diphosphine)X2Nb(μ-X)4NbX2(diphosphine)] with single Nb-Nb bonds and chelating diphosphines. The Nb(IV) complexes are prone to hydrolysis and oxidation in solution and the structures of the Nb(V) complexes [NbBr4(Me2PCH2CH2PMe2)2][NbOBr4(MeCN)] with a dodecahedral cation, and [{NbOCl3{Et2P(CH2)2PEt2}}2{μ-Et2P(CH2)2PEt2}] which contains seven-coordinate Nb(V) centres with a symmetrical diphosphine bridge are reported. The structure of niobium tetrabromide, conveniently made from NbCl4 and BBr3, is a chain polymer with edge-linked NbBr6 octahedra and alternating long and short Nb-Nb distances, the latter ascribed to Nb-Nb bonds

Lanthanoid “Bottlebrush” Clusters: Remarkably Elongated Metal-Oxo Core Structures with Controllable Lengths

Large metal-oxo clusters consistently assume spherical or regular polyhedral morphologies rather than high-aspect-ratio structures. Access to elongated core structures has now been achieved by the reaction of lanthanoid salts with a tetrazole-functionalized calixarene in the presence of a simple carboxylate coligand.The resulting Ln19 and Ln12 clusters are constructed from apex-fused Ln5O6 trigonal bipyramids and are formed consistently under a range of reaction conditions and reagent ratios. Altering the carboxylate coligandstructure reliably controls the cluster length, giving access to a new class of rod-like clusters of variable length

Étude par RMN de la solvatation du pentaméthoxyniobium et de ses complexes

RMN à basse température, de la molécule dimère [Nb(OCH3)5]2 et de ses complexes Nb(OCH3)5-L dans une large variété de solvants, nous a permis de mettre en évidence une variation significative et reproductible des déplacements chimiques des divers groupes méthoxy non-équivalents présents dans ces molécules. Des effets parallèles ont été observés pour les constantes d’équilibre Dimère [math] Complexes. Les caractéristiques essentielles de ces effets (amplitude des variations des différences de déplacements chimiques pour des sites non-équivalents, nombre de molécules de solvant polaire nécessaire pour atteindre un effet maximum, « retards » éventuels dans ces variations) sont principalement fonction de la taille du solvant et du rapport ε — 1 /ε + 1. L’analyse de ces résultats expérimentaux nous conduit à attribuer les effets observés à un facteur prédominant : le champ de réaction entre soluté et solvant, c’est-à-dire à la solvatation des espèces dissoutes. Le nombre de molécules de solvant polaire présent dans la première sphère de solvatation est estimé. La solvatation préférentielle de certains des sites est discutée en fonction surtout de la taille de la molécule de solvant. Enfin l’attribution des signaux correspondant aux protons terminaux du dimère est tentée

Metal 2-ethylhexanoates and related compounds as useful precursors in materials science

International audienceThis critical review discusses the chemistry and applications of metal 2-ethylhexanoates and related medium chain (C5 to C12) metal alkanoates. These compounds are rapidly emerging as attractive precursors for the preparation of nano-materials and are amongst the most promising catalysts for the ring opening polymerization of lactones and lactides

Hydrolysis of a (2-Propanol)yttrium Triiodide Complex in the Presence of Glymes: Synthesis and X-ray Structures of Hydroxo-Bridged Dinuclear Yttrium Complexes and Their Applications in Materials Science

International audienceThe reactions of (2-propanol)yttrium triiodide, Y(iPrOH)4I3, with stoichiometric amounts of water in the presence of di-, tri-, and tetraglyme yield a facile synthetic route to hydroxo-bridged, centrosymmetric dimeric yttrium complexes. These ionic derivatives, [Y2L2(-OH)2(H2O)x(ROH)y]I4 [1: L = triglyme, x = 2, y = 2, R = iPr; 2: L = tetraglyme, x = 2, y = 0; 3·2EtOH: L = diglyme, x = 2, y = 4, R = Et; 4·2EtOH: L = triglyme, x = 4, y = 0; 5: L = tetraglyme, x = 2, y = 2, R = Et] have been characterized by elemental analysis, IR and 1H NMR spectroscopy, as well as by single-crystal X-ray diffraction for 3, 4, and 5. Preliminary results on the utility of these ionic derivatives as potential sources of yttrium oxide in high Tc superconductors are also presented

Rare example of a polynuclear heterometallic yttrium(III)-copper(I) iodide cluster with a Y-6(mu(6)-O)(mu(3)-OH)(8) (8+) core structure showing single crystal-to-single crystal transformation

Mishra, Shashank Jeanneau, Erwann Daniele, Stephane Hubert-Pfalzgraf, Liliane G.A colorless polynuclear heterometallic yttrium(III)-copper(I) iodide cluster [Y-6(mu(6)-O)(mu(3)-OH)(8)(DMSO)(16)(H2O)(2)](8+) [Cu2I4](2-) 6[I](-) (1), isolated in a moderate yield from the hydrolytic reaction of [Y(DMSO)(6)(DMF)(2)][CuI3][I] in acetonitrile, undergoes unique crystal-to-crystal transformation to give reddish-yellow cluster [Y-6(mu(6)-O)(mu(3)-OH)(8)(DMSO)(14)(H2O)(4)](8+) 2[CuI3](2-) 3[I](-) [I-3](-) (2)

Hexakis{mu2-4-[2-(diisopropylamino)ethylamino]pent-3-en-2-onato-3N,O:O}tricalcium(II) hexane solvate

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