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Yu X.,University of Waterloo | Mailman A.,University of Waterloo | Lekin K.,University of Waterloo | Assoud A.,University of Waterloo | And 6 more authors.
Journal of the American Chemical Society | Year: 2012

Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna2 1, revealed the importance of intermolecular oxygen-to-sulfur (CO⋯SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-temperature conductivity measurements on 3a and 3a·MeCN indicated high values of θ(300 K) (>10 -3 S cm -1) with correspondingly low thermal activation energies E act, reaching 0.11 eV in the case of 3a·MeCN. Overall, the strong performance of these materials as f = 1/ 2 conductors is attributed to a combination of low U and large W. Variable-temperature magnetic susceptibility measurements were performed on both 3a and 3a·MeCN. The unsolvated material 3a orders as a spin-canted antiferromagnet at 8 K, with a canting angle φ = 0.14° and a coercive field H c = 80 Oe at 2 K. © 2012 American Chemical Society.

Dass A.,University of Mississippi | Theivendran S.,University of Mississippi | Nimmala P.R.,University of Mississippi | Kumara C.,University of Mississippi | And 7 more authors.
Journal of the American Chemical Society | Year: 2015

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the "nanostructure problem". Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au133(SPh-tBu)52, was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than in the slightly larger Au144(SCH2CH2Ph)60. Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation. © 2015 American Chemical Society.

Mebi C.A.,Arkansas Tech University | Karr D.S.,Arkansas Tech University | Noll B.C.,Bruker AXS Inc.
Polyhedron | Year: 2013

Diiron-carbonyl complexes coupled to naphthalene-2-thiolate ligands, [(μ-naphthalene-2-thiolato)2Fe2(CO)6] (1) and [(μ-naphthalene-2-thiolato)2Fe2(CO) 5PPh3] (2), have been usefully prepared and structurally characterized. As models for the active site of hydrogenase enzymes, these compounds have been examined as electrocatalysts for the reduction of proton to produce molecular hydrogen. In the presence of acetic acid, 1 and 2 catalyze the electrochemical production of molecular hydrogen with mild overpotentials of -0.54 and -0.51 V versus Fc/Fc+, respectively. The overpotential for compound 1 is 260 mV smaller than that of the analogous compound, [(μ-SPh)2Fe2(CO)6]. © 2012 Elsevier Ltd. All rights reserved.

Shaw B.J.,Amgen Inc. | Semin D.J.,Amgen Inc. | Rider M.E.,Bruker AXS Inc. | Beebe M.R.,Technos International Inc.
Journal of Pharmaceutical and Biomedical Analysis | Year: 2012

Palladium (Pd) is extensively used in pharmaceutical small molecule drug substance processes, however it must be removed prior to release of the active pharmaceutical ingredient (API). Evaluation of four TXRF instruments and configurations were compared to ICP-MS instrumentation for trace metal analysis, most importantly for Pd. Standards and six pharmaceutical drug substances, triprolidine HCl, diphenhydramine HCl, chlorpheniramine maleate, pseudoephedrine HCl, ephedrine sulfate, and scopolamine HBr, were analyzed to determine linearity, sensitivity, accuracy, and precision for Pd plus Cr, Fe, Cu, Rh, and Pt versus interferences, particularly from Cl, S, and Ar, on the various X-ray fluorescence lines. Irrespective of instrument platform, in general X-ray sources capable of accessing Pd-K lines were found to be most effective in determination of Pd in APIs. © 2012 Elsevier B.V..

Ying J.-W.,Purdue University | Liu I.P.-C.,Purdue University | Xi B.,Purdue University | Song Y.,Nanjing University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2010

(Figure Presented) Ru communicating? Butadiyn-diyl bridges link three Ru2 moieties together to give a molecular wire (see structure, red Ru, green C, blue N, purple O). Voltammetric, spectroscopic, and magnetic data all point to extensive electronic derealization across the linear trimer. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

West J.K.,University of North Dakota | Fondong G.L.,University of North Dakota | Noll B.C.,Bruker AXS Inc. | Stahl L.,University of North Dakota
Dalton Transactions | Year: 2013

Because of the increasing importance of N-heterocyclic carbenes in organometallic chemistry we investigated the ligand properties of structurally-related acyclic and cyclic heavier carbene analogues with transition metal chlorides. Acyclic {(Me3Si)2N} 2El, El = Ge and Sn, react with CuCl with transfer of one (Me 3Si)2N ligand to yield the known copper tetramer {(Me 3Si)2NCu}4. The cyclic Me2Si(μ- NtBu)2Ge, by contrast, binds copper through germanium only, furnishing a tetranuclear ladder structure with both terminal and bridging germylenes. The tin homologue, however, inserts into the CuCl bond, and the ensuing {Me2Si(μ-NtBu)2SnCl}- ions then coordinate one copper ion via their tin atoms while sandwiching the remaining three copper ions in an unprecedented κ2-N,N′ fashion. Chemically-harder Cr(ii) - created in a redox reaction of Me 2Si(μ-NtBu)2Sn with CrCl3(THF) 3 - is not coordinated by tin, but chelated by both nitrogen atoms of one {Me2Si(μ-NtBu)2SnCl}- ion and more weakly through the tin-bound chloride. This journal is © 2013 The Royal Society of Chemistry.

Nyman M.,Sandia National Laboratories | Rodriguez M.A.,Sandia National Laboratories | Campana C.F.,Bruker AXS Inc.
Inorganic Chemistry | Year: 2010

The hexavalent uranium specie, uranyl triperoxide, UO2(O 2)3 4-, has been shown recently to behave like high oxidation-state d0 transition-metals, self-assembling into polyoxometalate-like clusters that contain up to 60 uranyl cations bridged by peroxide ligands. There has been much less focus on synthesis and structural characterization of salts of the monomeric UO2(O2) 3 4- building block of these clusters. However, these could serve as water-soluble uranyl precursors for both clusters and materials, and also be used as simple models to study aqueous behavior by experiment and modeling. The countercation is of utmost importance to the assembly of these clusters, and Li+ has proven useful for the crystallization of many of the known cluster geometries to date. We present in this paper synthesis and structural characterization of two monomeric lithium uranyl-peroxide salts, Li4[UO2(O2)3] 10H2O (1) and [UO2(O2)3]12[(UO 2(OH)4)Li16(H2O)28] 3 Li6[H2O]26 (2). They were obtained from aqueous-alcohol solutions rather than the analogous aqueous solutions from which lithium uranyl-peroxide clusters are crystallized. Rapid introduction of the alcohol gives the structure of (1) whereas slow diffusion of alcohol results in crystallization of (2). (2) is an unusual structure featuring uranyl-centered alkali clusters that are linked into ring and spherical arrangements via [UO2(O2)3] anions. Furthermore, partial substitution of Rb or Cs into the synthesis results in formation of (2) with substitution of these larger alkalis into the uranyl-centered clusters. We surmise that the slow crystallization allows for direct bonding of alkali metals to the uranyl-peroxide oxygen ligands that is observed in (2), and its Rb and Cs-substituted derivatives. In contrast, the only interaction between UO2(O2)3 4- and Li+ observed in (1) is through hydrogen bonding of the lithium-bound water. These structures potentially provide some insight to understanding how alkali counterions interact with the UO2(O 2)3 4- anions during the self-assembly, crystallization and even redissolution of uranyl-peroxide polyanionic clusters. © 2010 American Chemical Society.

Wang Q.,University of Colorado at Boulder | Zhang C.,University of Colorado at Boulder | Noll B.C.,Bruker AXS Inc. | Long H.,National Renewable Energy Laboratory | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2014

Shape-persistent covalent organic polyhedrons (COPs) with ethynylene linkers are usually prepared through kinetically controlled cross-coupling reactions. The high-yielding synthesis of ethynylene-linked rigid tetrameric cages via one-step alkyne metathesis from readily accessible triyne precursors is presented. The tetrameric cage contains two macrocyclic panels and exhibits D2h symmetry. The assembly of such a COP is a thermodynamically controlled process, which involves the initial formation of macrocycles as key intermediates followed by the connection of two macrocycles with ethynylene linkages. With a large internal cavity, the cage exhibits a high binding selectivity toward C70 (K=3.9×103 Lmol-1) over C60 (no noticeable binding). Clever cages: A tetrameric cage with a D2h symmetry was prepared from a C3-symmetric triyne monomer through a one-step alkyne metathesis. The tetramer consisting of two macrocyclic panels has a large internal cavity, which can selectively host C70 over C60. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

He B.B.,Bruker AXS Inc
Materials Science Forum | Year: 2014

Stress measurement on samples with texture and large grains is always a challenge. The diffraction peak intensity varies dramatically with different sample orientation. The macroscopic elasticity becomes anisotropic due to strong preferred orientation. The large grains may results in a big error in 2θ due to poor sampling statistics. The fitting results of the conventional sin2ψ method is extremely sensitive to texture and large grains. When stress is measured with a 2D detector, most of the above adverse effects can be minimized or eliminated. The data integration helps to smooth out rough diffraction profiles due to large grain size, texture, small sample area or weak diffraction. The large angular coverage and multiple diffraction rings can minimize the effect of the macroscopic anisotropy. The weighted least squares regression and intensity threshold can further reduce the effect of poor statistics associated with texture and large grains. Multiple {hkl} rings may be used to measure the stress to improve the statistics and minimize the elastic anisotropy effect. © (2014) Trans Tech Publications, Switzerland.

Choi K.J.,University of Wisconsin - Madison | Baek S.H.,University of Wisconsin - Madison | Jang H.W.,University of Wisconsin - Madison | Belenky L.J.,University of Wisconsin - Madison | And 2 more authors.
Advanced Materials | Year: 2010

The temperature dependence of in-plane and out-of-plane lattice parameters of a compressively strained SrRuO3 thin film grown on a SrTiO3 substrate is reported. The structural transition temperature of the SrRuO3 thin film shifts by more than 200 °C toward the lower-temperature region due to compressive strain (see graph). © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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