Search results for "BIM"
showing 10 items of 365 documents
Structure and Deformations of Pd−Ni Core−Shell Nanoparticles
2005
International audience; Homogeneous collections of Pd−Ni core−shell nanoparticles have been prepared by decomposition of metal−organic compounds and studied by several electron microscopy techniques: transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), energy-filtered microscopy (EFTEM), and by X-ray photoelectron spectroscopy (XPS). The physical and chemical properties of the Pd shell are supposed to depend on its electronic properties, which are influenced by the presence of the Ni core and by the deformation in the Pd lattice. Here, the interfacial structure of Pd/Ni and the lattice deformations in t…
Novel Bimetallic-Dicyanamide Extended Two- and Three-Dimensional Networks through [Cu(rac-CTH)]2+ Cation Templation
2009
Reaction of [Cu(rac-CTH)]2+ with dicyanamide and Mn2+ or Fe2+ produces three bimetallic extended structures. Complexes 1 and 2, both obtained in the same reaction pot, consist of two different (4,4) two-dimensional (2D) layers, with the [Cu(rac-CTH)(dca)]+ cations noncoordinated and coordinated to the Mn(μ1,5-dca) network for 1 and 2, respectively (rac-CTH = racemic-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). Complex 2 shows an unusual monodentate coordination mode through the central amide nitrogen of the dca ligand which is first reported for a polynuclear complex. The structure of 3 consists of a three-dimensional network which can be described as a stacking of layers m…
[Ni(cyclam)(μ1,3-dca)2Cu(μ1,5-dca)2]: A Genuine 3D Bimetallic Coordination Polymer Containing Both μ1,3- and μ1,5-Bidentate Dicyanamide Bridges and …
2005
The structure of [Ni(cyclam)(μ 1 , 3 -dca) 2 Cu(μ 1 , 5 -dca) 2 ], a genuine 3D dicyanamide-bridged bimetallic coordination polymer, is made up of 2D [Cu(μ- 1 , 5 dca) 2 ] n layers connected by [Ni(cyclam)(μ 1 , 3 -dca) 2 ] bridging moieties; it exhibits a ferromagnetic exchange interaction between copper(ll) and nickel(ll) ions through the μ 1 , 3 -bidentate dicyanamide bridges.
Design of single chain magnets through cyanide-bearing six-coordinate complexes
2005
Abstract The design and preparation of stable cyanide-bearing six-coordinate complexes of formula [MIII(L)(CN)x](x + l − m)− (M = trivalent transition metal ion and L = polydentate blocking ligand) are summarized here. Their use as ligands towards either fully hydrated metal ions or coordinatively unsaturated preformed species, to afford a wide variety of low-dimensional metal assemblies whose nuclearity, dimensionality and magnetic properties can be tuned, is also reviewed. Special emphasis is put on the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors. Among the different new spin topologies obtain…
Synthesis, crystal structure and magnetic properties of the malonato-bridged bimetallic chain [Mn(II)Cu(II)(mal)2(H2O)4]·2H2O
2000
Abstract The first malonato-bridged bimetallic chain of formula [MnCu(mal)2(H2O)4]·2H2O (1) (H2mal=malonic acid) was prepared and its structure determined by X-ray diffraction methods. Each copper atom in 1 is in a square planar environment formed by four malonate-oxygens from two malonate ligands. The manganese atom is six-coordinated with four water molecules and two cis-coordinated malonate-oxygens from two malonate groups building a distorted octahedral surrounding. The malonate group acts simultaneously as bidentate and monodentate ligand towards copper and manganese atoms respectively, leading to a bimetallic chain. Two structurally different carboxylato-bridges exhibiting an anti–syn…
High proton conduction in a chiral ferromagnetic metal-organic quartz-like framework.
2011
A complex-as-ligand strategy to get a multifunctional molecular material led to a metal-organic framework with the formula (NH(4))(4)[MnCr(2)(ox)(6)]·4H(2)O. Single-crystal X-ray diffraction revealed that the anionic bimetallic coordination network adopts a chiral three-dimensional quartz-like architecture. It hosts ammonium cations and water molecules in functionalized channels. In addition to ferromagnetic ordering below T(C) = 3.0 K related to the host network, the material exhibits a very high proton conductivity of 1.1 × 10(-3) S cm(-1) at room temperature due to the guest molecules.
Density Functional Theory Investigation on the Nucleation of Homo- and Heteronuclear Metal Clusters on Defective Graphene
2016
Nucleation of homo- (Ni, Pd, Re, Pt) and heterometallic (Ni–Pd, Re–Pt) clusters on monovacancy sites of a graphene sheet has been investigated by means of periodic density functional theory calculations. It is shown that a vacant site in graphene is an effective nucleation center for both the monometallic and bimetallic clusters, whose characteristics are described in terms of structural distortions, nucleation energetics, affinities between different metal atoms, metal–carbon interactions, and ease of diffusion of metal atoms on graphene.
Ti–Ru bimetallic complexes: catalysts for ring-closing metathesis
2002
The reaction of the titanocene monophosphanes ( 1 – 4 ) with the dimer [( p -cymene)RuCl 2 ] 2 gives the heterobimetallic compounds ( p -cymene)[(η 5 -C 5 H 5 )(μ-η 5 :η 1 -C 5 H 4 (CR 2 ) n PR′ 2 )TiCl 2 ]RuCl 2 ( 5 – 8 ). The structure of 8 , determined by X-ray diffraction, is reported here. A preliminary assessment of the performance of these complexes in ring-closing metathesis (RCM) revealed an excellent Ti–Ru–allenylidene pre-catalyst 12 .
Effects of Silver Doping on the Geometric and Electronic Structure and Optical Absorption Spectra of the Au_{25-n}Ag_{n}(SH)_{18}^{-} (n = 1, 2, 4, 6…
2012
The effect of silver doping of the Au25(SH)18– nanoparticle is studied by investigating Au25–nAgn(SH)18– (n = 1, 2, 4, 6, 8, 10, 12) systems using DFT. For n = 1, doping of the icosahedral shell of the metal core is energetically more favorable than doping of the metal–thiolate units or the center of the core. For n ≥ 2, only doping of the core surface is considered, and arrangements where the silver dopants are in close proximity tend to be slightly less favorable. However, energy differences are small, and all conformations are accessible under experimental conditions. Boltzmann-averaged excitation spectra for these systems show similar features to the undoped Au25(SH)18–. The main differ…
Ultrastructural changes of the oenocytes of Gryllus bimaculatus DEG (Saltatoria, Insecta) during the moulting cycle
1974
1. The oenocytes of Gryllus bimaculatus are characterized by an abundant smooth-surfaced ER (ATER). In spite of the great cell size the plasma membrane never shows extensive infoldings during the moulting cycle. In addition to mitochondria there are very large numbers of microbodies containing peroxidase but apparently not uricase. Within the second part of the instar the microbodies lie along the clefts which run through the whole cell. 2. The following changes are observed in the course of a moulting cycle: Immediately after hatching the ATER is scarcely developed, some liposomes are located within areas of ATER disappearing some hours later. 20 hours after emergence glycogen deposits app…