Cooperative magnetic behavior in the coordination polymers [Cu-3(TMA)(2)L-3] (L=H2O, pyridine)

The temperature and magnetic field dependent magnetization of the polymeric solids [Cu-3(TMA)(2)L-3], where TMA=benzene-1,3-5-tricarboxylate and L=H2O or pyridine have been measured up to 5 T. These polymers contain dimeric [Cu-2(O2CR)(4)] units. Discrete dimers in molecules such as cupric acetate have strong antiferromagnetic coupling between their two Cu d(9) centers and at low T their susceptibility diminishes to nearly zero. While at higher T (300-100 K) the magnetism of the [Cu-3(TMA)(2)L-3] polymers resembles that of individual the [Cu-2] dimer molecules, at low T a new cooperative behavior is found, with a sharp increase in chi seen at temperature below 75 K. In the case of L=pyridine a plot of 1/chi vs T shows linearity from 65 to 20 K and fits the Curie-Weiss law chi=C/(T - Theta ). Theta is found to be +4.7 K, indicative of a weak ferromagnetic coupling between dimers. This interaction may be facilitated by the planar aromatic bridges between the [Cu-2] units. (C) 2000 American Institute of Physics. [S0021-8979(00)17708-4]

Barium terephthalate, a three-dimensional coordination polymer with 7 : 7 cation-anion connectivity

Barium terephthalate, [Ba{1,4-C6H4(COO)(2)}](n), forms a three-dimensional coordination network polymer with 7:7 connectivity between the barium cations and terephthalate dianions. Each Ba atom is eight-coordinate and uses all eight oxygen lone pairs of the ligand

Structure determination of homoleptic AuI, AgI, and CuI aryl/alkylethynyl coordination polymers by X-ray powder diffraction

This article describes the structure determination of five homoleptic d10 metal-aryl/alkylacetylides [RC≡CM] (M = Cu, R = tBu 1, nPr 2, Ph 3; R = Ph, M = Ag 4; Au 5) by using X-ray single-crystal and powder diffraction. Complex 1·C6H6 reveals an unusual Cu20 catenane cluster structure that has various types of tBuC≡C→Cu coordination modes. By using this single-crystal structure as a starting model for subsequent Rietveld refinement of X-ray powder diffraction data, the structure of the powder synthesized from CuI and tBuC≡CH was found to have the same structure as 1. Complex 2 has an extended sheet structure consisting of discrete zig-zag Cu4 subunits connected through bridging nPrC≡C groups. Complex 3 forms an infinite chain structure with extended Cu-Cu ladders (Cu-Cu = 2.49(4)-2.83(2) Å). The silver(I) congener 4 is iso-structural to 3 (average Ag-Ag distance 3.11 Å), whereas the gold(I) analogue 5 forms a Au⋯Au honeycomb network with PhC≡C pillars (Au-Au = 2.98(1)-3.26(1) Å). Solid-state properties including photoluminescence, v(C≡C) stretching frequencies and thermal stability of these polymeric systems are discussed in the context of the determined structures. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.link_to_subscribed_fulltex

Thermotropic liquid crystals based on extended 2,5-disubstituted-1,3,4- oxadiazoles: Structure-property relationships, variable-temperature powder X-ray diffraction, and small-angle X-ray scattering studies

A class of extended 2,5-disubstituted-1,3,4-oxadiazoles R 1-C 6H 4-{OC 2N 2}-C 6H 4-R 2 (R 1 = R 2 = C 10H 21O 1a, P-C 10H 21O-C 6H 4-C≡C 3a, p-CH 3O-C 6H 4-C≡C 3b; R 1=C 10H 21O, R 2 = CH 3O 1b, (CH 3) 2N 1c; F 1d; R 1 = C 10H 21O-C 6H 4- C≡C, R 2 = C 10H 21O 2a, CH 3O 2b, (CH 3) 2N 2c, F 2d) were prepared, and their liquid-crystalline properties were examined. In CH 2Cl 2 solution, these compounds displayed a room-temperature emission with λ max at 340-471 nm and quantum yields of 0.73-0.97. Compounds 1d, 2a-2d, and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized-light optical microscopy and differential scanning calorimetry. Structure determination by a direct-space approach using simulated annealing or parallel tempering of the powder X-ray diffraction data revealed distinctive crystal-packing arrangements for mesogenic molecules 2b and 3 a, leading to different nematic mesophase behavior, with 2b being monotropic and 3 a enantiotropic in the narrow temperature range of 200-210°C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable-temperature X-ray diffractometry. Nondestructive phase transitions (crystal-to-crystal, crystal-to-mesophase, mesophase-to-liquid) were observed in the diffracto-grams of 1b, 1d, 2b, 2d, and 3a measured at 25-200°C. Powder X-ray diffraction and small-angle X-ray scattering data revealed that the structure of the annealed solid residue 2b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure-property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.link_to_subscribed_fulltex

Sodium copper(II) trimesate, [NaCu{C6H3(COO)(3)}(H2O)(4)]center dot 2H(2)O, a double-sheet coordination polymer with bridging aqua ligands

The title compound, poly[[[mu-aqua-diaquasodium(I)copper(II)]-mu-aqua-mu-trimesate(3-) ] dihydrate], contains one-dimensional zigzag polymer strands of trimesate and Cu2+ ions, which are connected into a two-dimensional double-sheet network via sodium ions and bridging aqua ligands

Structures, photoluminescence, and reversible vapoluminescence properties of neutral platinum(II) complexes containing extended π-conjugated cyclometalated ligands

Reacting K2PtCl4 with the tridentate R-C^N^C-H 2 ligands 2,6-di-(2′-naphthyl)-4-R-pyridine (R = H, 1a; Ph, 1b; 4-BrC6H4, 1c; 3,5-F2C6H 3, 1d) in glacial acetic acid, followed by heating in dimethyl sulfoxide (DMSO), gave complexes [(R-C^N^C)Pt(DMSO)] (2a-d). In the crystal structures of 2a-c, the molecules are paired in a head-to-tail orientation with Pt⋯Pt separations >6.3 Å, and there are extensive close C-H⋯π (d = 2.656-2.891 Å), π⋯π (d = 3.322-3.399 Å), and C-H⋯O=S (d = 2.265-2.643 Å) contacts. [(Ph-C^N^C)Pt(PPh3)] (3) was prepared by reacting 2b with PPh 3. Reactions of 2a-d with bis(diphenylphosphino)-methane (dppm) gave [(R-C^N^C)2Pt2(μ-dppm)] (4a-d). Both head-to-head (syn) and head-to-tail (anti) conformations were found for 4a·6CHCl 3·C5H12, whereas only one conformation was observed for 4b· 2CHCl3 (syn), 4c·3CH 2Cl2 (syn), and 4d·2CHCl3 (anti). In the crystal structures of 4a-d, there are close intramolecular Pt⋯Pt contacts of 3.272-3.441 Å in the syn conformers, and long intramolecular Pt⋯Pt separations of 5.681-5.714 Å in the anti conformers. There are weak C-H⋯X (d = 2.497-3.134 Å) and X⋯X (X = Cl or Br; d = 2.973-3.655 Å) interactions between molecules 4a-d and occluded CHCl3/CH2Cl2 molecules, and their solvent channels are of varying diameters (∼9-28 Å). Complexes 2a-d, 3, and 4a-d are photoluminescent in the solid state, with emission maxima at 602-643 nm. Upon exposure to volatile organic compounds, 4a shows a fast and reversible vapoluminescent response, which is most intense with volatile halogenated solvents (except CCl4). Powder X-ray diffraction analysis of desolvated 4a revealed a more condensed molecular packing of syn and anti complexes than crystal 4a·6CHCl3· C5H 12. © 2006 American Chemical Society.link_to_subscribed_fulltex

Copper stabilization via spinel formation during the sintering of simulated copper-laden sludge with aluminum-rich ceramic precursors

The feasibility of incorporating copper-laden sludge into low-cost ceramic products, such as construction ceramics, was investigated by sintering simulated copper-laden sludge with four aluminum-rich ceramic precursors. The results indicated that all of these precursors (γ-Al2O3, corundum, kaolinite, mullite) could crystallochemically stabilize the hazardous copper in the more durable copper aluminate spinel (CuAl2O 4) structure. To simulate the process of copper transformation into a spinel structure, CuO was mixed with the four aluminum-rich precursors, and fired at 650-1150 °C for 3 h. The products were examined using powder X-ray diffraction (XRD) and scanning electron microscopic techniques. The efficiency of copper transformation among crystalline phases was quantitatively determined through Rietveld refinement analysis of the XRD data. The sintering experiment revealed that the optimal sintering temperature for CuAl2O 4 formation was around 1000 °C and that the efficiency of copper incorporation into the crystalline CuAl2O4 structure after 3 h of sintering ranged from 40 to 95%, depending on the type of aluminum precursor used. Prolonged leaching tests were carried out by using acetic acid with an initial pH value of 2.9 to leach CuO and CuAl2O4 samples for 22 d. The sample leachability analysis revealed that the CuAl 2O4 spinel structure was more superior to stabilize copper, and suggested a promising and reliable technique for incorporating copper-laden sludge or its incineration ash into usable ceramic products. Such results also demonstrated the potential of a waste-to-resource strategy by using waste materials as part of the raw materials with the attainable temperature range used in the production of ceramics. © 2011 American Chemical Society.link_to_subscribed_fulltex

A chemically functionalizable nanoporous material [Cu-3(TMA)(2)(H2O)(3)](n)

Although zeolites and related materials combine nanoporosity with high thermal stability, they are difficult to modify or derivatize in a systematic way. A highly porous metal coordination polymer [Cu-3(TMA)(2)(H2O)(3)](n) (where TMA is benzene-1,3,5-tricarboxylate) was formed in 80 percent yield. It has interconnected [Cu-2(O2CR)(4)] units (where R is an aromatic ring), which create a three-dimensional system of channels with a pore size of 1 nanometer and an accessible porosity of about 40 percent in the solid. Unlike zeolites, the channel Linings can be chemically functionalized; for example, the aqua ligands can be replaced by pyridines. Thermal gravimetric analysis and high-temperature single-crystal diffractometry indicate that the framework is stable up to 240 degrees C

Homoleptic ruthenium(III) chalcogenolates: A single precursor to metal chalcogenide nanoparticles catalyst

Eight homoleptic metal(III) arylchalcogenolate polymers [M(EPh-p-X) 3] n (M = Ru, Cr, and Mo) were characterized by PXRD. Structural solution of [Ru(SPh-p-tBu) 3] n1 was achieved by Rietveld refinement of the PXRD data. Pyrolysis of [Ru(SePh) 3] n4 produced nanostructured RuSe 2, which selectively catalyzed the reduction of nitro compounds in the presence of other functionalities. © 2011 The Royal Society of Chemistry.link_to_subscribed_fulltex