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Metal Core (metal + core)
Selected AbstractsSynthesis, Upconversion Luminescence and Magnetic Properties of New Lanthanide,Organic Frameworks with (43)2(46,66,83) TopologyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2007Danfeng Weng Abstract The synthesis and crystal structures of three new lanthanide,organic frameworks [Ln(pza)(OH)(H2O)]n (Ln = Y(1), Er(2), Yb(3); H2pza = 2,3-pyrazinedicarboxylic acid) with helical chains and novel 2D (43)2(46,66,83) topology are reported. The topology is obtained by simplifying the dinuclear metal core as a six-connected node and the ligand as a three-connected linker. The upconversion property measurement gives green and red emissions coming from two-photon excitation of Y: Er, Yb codoped coordination polymer and arising from ErIII transitions of 4S3/2/2H11/2,4I15/2 and 4F9/2,4I15/2. The magnetic properties of complexes 2 and 3 are also studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Hydrophilic Sparse Ionic Monolayer-Protected Metal Nanoparticles: Highly Concentrated Nano-Au and Nano-Ag "Inks" that can be Sintered to Near-Bulk Conductivity at 150,°CADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Bibin T. Anto Here, monolayer-protected gold and silver nanoparticles with extremely high solvent dispersibility (over 200,mg mL,1 in water and glycols) and low coalescence temperature (approximately 150,°C, measured by the percolation transition temperature Tp) are developed, to reach conductivities better than 1,×,105,S cm,1. These materials are suitable for inkjet and other forms of printing on substrates that may be solvent- and/or temperature-sensitive, such as for plastic electronics, and as bus lines for solar and lighting panels. This is achieved using a new concept of the sparse ionic protection monolayer. The metal nanoparticles are initially protected by a two-component mixed ligand shell comprising an ,-functionalized ionic ligand and a labile ligand. These are selectively desorbed to give a sparse shell of the ,-ionic ligands of ca. 25% coverage. Through a systematic study of different monolayer-protected Au nanoparticles using FTIR spectroscopy, supported by XPS and DSC, it is shown that Tp is not determined by thermodynamic size melting or by surface area effects, as previously thought, but by the temperature when ca. 80% of the dense monolayer is eliminated. Therefore, Tp depends on the thermal stability and packing density of the shell, rather than the size of the metal core, while the solubility characteristics depend strongly on the exposed terminal group. [source] Experimental study and analysis of the application of ice-storage capsules in an air conditioning systemHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2002Shuiquan Ye Abstract Ice-storage capsules are used in an energy-efficient air conditioning system. Experiments and numerical simulations were conducted to investigate the effects of different structural configurations of the capsules on the freezing and melting processes of the refrigerant solution sealed inside the capsules. The predictions of the numerical simulation are in good agreement with the test results. The results show that the freezing speed of the capsules equipped with a metal core is 30% to 50% faster than for capsules without the metal core. In addition, it was found that the special refrigerant solution used in the experiment had a lower freezing point and a higher freezing speed than water. The effects of the size of the metal core, and the coolant temperatures are also investigated. © 2001 Scripta Technica, Heat Trans Asian Res, 31(1): 21,27, 2002 [source] Synthesis of Schiff Base-Ruthenium Complexes and Their Applications in Catalytic ProcessesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005Renata Drozdzak Abstract The synthesis of various Schiff base mononuclear and binuclear ruthenium complexes, whose additional ligands around the metal core have been selected from an array of motifs, is described. These types of ruthenium complexes, conveniently prepared from commonly available ruthenium sources, are rather stable, display good tolerance towards diverse organic functionalities and also to air and moisture. Remarkably, they exhibit a high activity and chemoselectivity in a variety of catalytic processes such as ring-closing metathesis (RCM), Kharasch addition, alkyne dimerization, enol ester synthesis, ring-opening metathesis polymerization (ROMP) and atom-transfer radical polymerization (ATRP). This review covers both homogeneous and heterogeneous hybrid Schiff base-ruthenium complexes. [source] Construction of a Novel Topological Frustrated System: A Frustrated Metal Cluster in a Helical SpaceCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2010Ryuta Ishikawa Abstract A novel topologically frustrated pentanuclear cluster helicate [{CuII(,-L)3}2CuII3(,3 -OH)]3+ (L,=3,5-bis(2-pyridyl)pyrazolate) has been synthesized and characterized. This cluster has a helical arrangement of ligands around the central metal core. Dzyaloshinsky,Moriya interactions are essential components to observe a gradual magnetization and forbidden transitions of high-field/multi-frequency (HF/MF)-ESR. The origin of the magnetic anisotropy of this compound is influenced by its helical spin structure, and consequently, the Cu5 -cluster helicate introduces a unique magnetic anisotropy. This observation is a direct evidence of the topological part of the new spin phase in a magnetic system. [source] Theoretical Exploration of the Oxidative Properties of a [(trenMe1)CuO2]+ Adduct Relevant to Copper Monooxygenase Enzymes: Insights into Competitive Dehydrogenation versus Hydroxylation Reaction PathwaysCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2008Aurélien de, Lande Dr. Abstract Singlet and triplet H-transfer reaction paths from CH and NH bonds were examined by means of DFT and spin-flip TD-DFT computations on the [(trenMe1)CuO2]+ adduct. The singlet energy surfaces allow its evolution towards H2O2 and an imine species. Whereas NH cleavage appears to be a radical process, CH rupture results in a carbocation intermediate stabilized by an adjacent N atom and an electrostatic interaction with the [CuIOOH] metal core. Upon injection of an additional electron, the latter species straightforwardly forms a hydroxylated product. Based on these computational results, a new mechanistic description of the reactivity of copper monooxygenases is proposed. [source] Redox Modification of EMACs Through the Tuning of Ligands: Heptametal(II) Complexes of Pyrazine-Modulated Oligo-,-pyridylamido LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2009Rayyat Huseyn Ismayilov Abstract Using pyrazine-modulated oligo-,-pyridylamido ligands N2 -(pyrazin-2-yl)- N6 -[6-(pyrazin-2-ylamino)pyridin-2-yl]pyridine-2,6-diamine (H3pzpz) and N2 -(pyrazin-2-yl)- N6 -[6-(pyridin-2-ylamino)pyridin-2-yl]pyridine-2,6-diamine (H3tpz), linear heptametal(II) extended metal atom chains (EMACs) [M7(,7 -L)4X2] [L = pzpz3,, M = NiII, X = Cl, (1), NCS, (2); M = CrII, X = Cl, (3), NCS, (4); L = tpz3,, M = CrII, X = Cl, (5), NCS, (6)] were synthesized and structurally characterized. Electrochemical studies showed that heptanickel(II) complexes can undergo one reversible oxidation at +0.46 V for 1 and +0.52 V for 2. Chromium(II) species 3 exhibited two reversible, one-electron oxidation peaks at +0.61 and +0.88 V, and 5 exhibited three reversible, one-electron oxidation peaks at +0.40, +0.68 and +1.07 V. The redox peaks shifted positively when axial ligands changed from chloride to thiocyanate anions, at +0.67 and +0.92 V for 4 and +0.44, +0.73 and +1.11 V for 6. The introduction of electron-withdrawing pyrazine rings to the spacer ligand retarded oxidation of the heptametal EMACs and stabilized the complexes. In nickel(II) species 1 and 2, both terminal nickel atoms exist in spin state S = 1 whereas all the inner nickel atoms exist in spin state S = 0. Temperature-dependent magnetic research revealed an antiferromagnetic interaction between the two terminal atoms through a superexchange pathway along metal cores with a parameter of about,4 cm,1. Chromium(II) species 3,6 showed a localized structure consisting of three quadruple Cr,Cr bonds and a single terminal CrII atom. Magnetic study revealed a quintet ground state resulting from the isolated, high-spin CrII atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Orientation and Arrangement of Octaruthenium Supramolecules with Alkyl Chains on GraphiteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2007Dong-Lin Shieh Abstract The self-assemblies of octaruthenium grid-type supramolecules, {[Ru2(CO)4(NH2C16H33)2](,-O2CCO2)}4, on highly oriented pyrolytic graphite (HOPG) in air and in 1-phenyloctane were studied by scanning tunneling microscopy (STM). The surface supramolecules are arranged into rows in which the metal cores are linearly packed and the alkyl chains are parallel to the surface. With the aid of theoretical calculations in the framework of density functional theory, the electronic origin of the tunneling in the measured STM images is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Micrometeorites from the northern ice cap of the Novaya Zemlya archipelago, Russia: The first occurrenceMETEORITICS & PLANETARY SCIENCE, Issue 3 2003Dmitry D. BADJUKOV The 1 Kyr old glacier has decreased in volume and coverage during the last 40 years, leaving the spherules contained in the ice at the margins of the glacier where they can be easily collected. The spherules are similar in their appearance, texture, and mineralogy to cosmic spherules found in deep-sea sediments in Greenland and Antarctica. Silicate spherules have typical bar-like textures (75%) or porphyritic textures (15%), while other spherules are glassy (7%). The spherules from Novaya Zemlya are altered only slightly. There are spherules consisting of iron oxides, metal cores with iron oxide rims, a continuous network of iron oxide dendrites in a glass matrix, and particles rich in chromite (3%). Some spherules contain metal droplets and relict forsterite and low-Ca pyroxene. Silicate spherule compositions match compositions of other cosmic spherules. Both Nova Zemlya and other cosmic spherules are close to carbonaceous chondrite matrices in patterns of variations for Ca, Mg, Si, and Al, which might suggest that their predecessor was similar to carbonaceous chondrite matrices. Unmelted micrometeorites are generally depleted in Ca and Mg and enriched in Al relative to cosmic spherules. The depletion of the micrometeorites in Ca and Mg can be connected with their terrestrial alteration (Kurat et al. 1994), while the Al enrichment seems to be primary. [source] Bonding abutments to cast metal post/cores: comparison of pre-treatment effectsJOURNAL OF ORAL REHABILITATION, Issue 2 2003H. Kajihara summary, Bond strengths were evaluated for (1) metal primer systems when the metal was contaminated by a dentin conditioner and (2) a dentin adhesive system when dentin was contaminated by metal primers. Disc specimens were cast in a silver,palladium,copper,gold (Ag,Pd,Cu,Au) alloy and dentin specimens were prepared by grinding the labial surface of bovine teeth. Specimens were treated with (1) metal primer alone, (2) dentin conditioner alone, (3) metal primer followed by dentin conditioner and (4) dentin conditioner followed by metal primer. A resin cement was poured into a mould over a restricted bonding area and allowed to set. Metal specimens were shear stressed to failure after thermocycling (4,60 °C; 20 000 cycles). Dentin specimens were stressed in the same manner after 24 h of immersion in 37 °C water. The results were compiled and analysed by anova. Data for dentin specimens treated with dentin conditioner only or with the combination of dentin conditioner and metal primer were not significantly different, statistically. Post-thermocycled groups indicated that bond strengths to the alloy significantly decreased (P < 0·05) when the primed metal surface was contaminated with dentin conditioner regardless of the timing of its application. [source] | ||||||||||