Physical Sciences and Mathematics Commons^™

Realization Of Random-Field Ising Ferromagnetism In A Molecular Magnet, Bo Wen, P Subedi, Lin Bo, Y Yeshurun, M P. Sarachik, A D. Kent, A J. Millis, Christos Lampropoulos, G Christou

Christos Lampropoulos

The longitudinal magnetic susceptibility of single crystals of the molecular magnet Mn12-acetate obeys a Curie-Weiss law, indicating a transition to a ferromagnetic phase at ∼0.9 K. With increasing magnetic field applied transverse to the easy axis, a marked change is observed in the temperature dependence of the susceptibility, and the suppression of ferromagnetism is considerably more rapid than predicted by mean-field theory for an ordered single crystal. Our results can instead be fit by a Hamiltonian for a random-field Ising ferromagnet in a transverse magnetic field, where the randomness derives from the intrinsic distribution of locally tilted magnetic easy axes …

Experimental Determination Of The Weiss Temperature Of Mn12-Ac And Mn12-Ac-Meoh, Christos Lampropoulos, Shiqi Li, Lin Bo, Bo Wen, M P. Sarachik, P Subedi, A D. Kent, Y Yeshurun, A J. Millis, S Mukherjee, G Christou

Christos Lampropoulos

We report measurements of the susceptibility in the temperature range from 3.5 to 6.0 K of a series of Mn12-ac and Mn12-ac-MeOH samples in the shape of rectangular prisms of length lc and square cross section of side la. The susceptibility obeys a Curie-Weiss law, χ=C/(T−θ), where θ varies systematically with sample aspect ratio. Using published demagnetization factors, we obtain θ for an infinitely long sample corresponding to intrinsic ordering temperatures Tc≈0.85 K and ≈0.74 K for Mn12-ac and Mn12-ac-MeOH, respectively. The difference in Tc for two materials that have nearly identical unit cell volumes and lattice constant ratios suggests …

Beyond The Chemistry Web, Robert A. Buchanan

Sci-Tech News

No abstract provided.

Two Different One-Dimensional Structural Motifs In The Same Coordination Polymer: A Novel Interpenetration Of Infinite Ladders By Bundles Of Infinite Chains, Badruz Zaman, Mark D. Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

A coordination polymer with a novel structural motif
consisting of stacks of infinite ladders interpenetrated by
bundles of infinite chains is described; geometrical arguments
are made for the requirements that can lead to such
interpenetration as a function of ligand dimensions.

Ligand-Directed Molecular Architectures: Self-Assembly Of Two-Dimensional Rectangular Metallocycles And Three-Dimensional Trigonal Or Tetragonal Prisms, Cheng-Yong Su, Yue-Ping Cai, Chun-Long Chen, Mark Smith, Wolfgang Kaim, Hans Conrad Zur Loye

Hans Conrad zur Loye

Three angular ditopic ligands (1,3-bis(benzimidazol-1-ylmethyl)-4,6-dimethylbenzene L1, 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene L2, and 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene L3) and one tripodal ligand 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene L4 have been prepared. Reaction of these shape-specific designed ligands with different metal salts affords a series of discrete molecular architectures: [Ag2L12](BF4)2 1, [Ag2L22](CF3SO3)2 2, [CF3SO3- Ag2L32]CF3SO3 3, [CF3SO3- Ag2L33]CF3SO3 4, [ClO4- Cu2L24](ClO4)3 5, [4H2O Ni2L24Cl4]·6H2O 6, [BF4- Ag3L42](BF4)2 7, [ClO4- Ag3L42](ClO4)2 8, and [CuI32- Cu3L42]2[Cu2I4] 9. The compounds were characterized by elemental analysis, ESI-MS, IR, and NMR spectroscopy, and X-ray crystallography. 1 is a dinuclear metallacycle with 2-fold rotational symmetry in which two syn-conformational L1ligands are connected by two linearly coordinated Ag+ ions. …

Ca4Iro6, Ca3Mgiro6 And Ca3Zniro6, Matthew J. Davis, Mark D. Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

Single crystals of tetracalcium iridium hexaoxide, Ca₄IrO₆, tricalcium magnesium iridium hexaoxide, Ca₃MgIrO₆, and tricalcium zinc iridium hexaoxide, Ca₃ZnIrO₆, were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The three compounds are isostructural and adopt the K₄CdCl₆ structure type, comprised of chains of alternating face-shared [CaO₆], [MgO₆] or [ZnO₆] trigonal prisms and [IrO₆] octahedra, surrounded by columns of Ca²⁺ ions.

Formula: Ca₄IrO₆, Ca_3.34Mg_0.66IrO₆ and …

Exceptionally Stable, Hollow Tubular Metal-Organic Architectures: Synthesis, Characterization And Solid-State Transformation Study, Cheng-Yong Su, Andrea Goforth, Mark Smith, P. Pellechia, Hans Conrad Zur Loye

Hans Conrad zur Loye

An effective solvothermal procedure has been developed to synthesize the new three-dimensional metal−organic framework, [ZnF(AmTAZ)]·solvents, using either 3-amino-1,2,4-triazole (AmTAZ) or 3-amino-1,2,4-triazole-5-carboxylic acid (AmTAZAc) and a choice of several Zn(II) salts as starting materials. The three-dimensional structure displays open-ended, hollow nanotubular channels that are formed by hexanuclear metallamacrocyclic Zn₆F₆(AmTAZ)₆ rings. The framework integrity is maintained to 350 °C, at which point most of the guest solvent molecules have been removed, as evidenced by single-crystal X-ray analyses, ¹H solid-state NMR, and TGA measurements. At higher temperatures, the framework is converted either to zinc oxide (ZnO) when …

Self-Assembled Nanotubes That Reversibly Bind Acetic Acid Guests, Linda Shimizu, Andrew Hughes, Mark Smith, Matthew Davis, B. Zhang, Hans Conrad Zur Loye

Hans Conrad zur Loye

A large bis-urea macrocycle was synthesized and assembled into columnar nanotubes containing a sizable cavity. This purely organic nanotube is held together primarily by hydrogen bonding and yet shows remarkable thermal stability up to 180 °C in the presence and absence of acetic acid guest. This enables the nanotube to be used as reusable organic zeolite.

Tris(1,10-Phenanthroline)Cobalt(Ii) Triiodide, Meredith Tershany, Andrea Goforth, Mark Smith, Leroy Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The asymmetric unit of the title compound, [Co(C₁₂H₈N₂)₃](I₃)₂, contains one [Co(1,10-phenanthroline)₃]²⁺ cation, half each of two centrosymmetric triiodide anions, and one complete triiodide anion. The title compound was synthesized solvothermally from Co(NO₃)₂, 1,10-phenanthroline, and SnI₂, where the SnI₂ reagent serves only as a source of I atoms.

Structure Determination Of Ba8Corh6O21, A New Member Of The 2h-Perovskite Related Oxides, Hans Conrad Zur Loye, M. D. Smith, K. E. Stitzer, A. El Abed, J. Darriet

Hans Conrad zur Loye

Single crystals of Ba₈CoRh₆O₂₁ were grown out of a potassium carbonate flux. The structure was solved by a general method using the superspace group approach. The superspace group employed was R3m(00γ)0s with a = 10.0431(1) Å, c₁ = 2.5946(1) Å and c₂ = 4.5405(1) Å, V = 226.60(1) ų. Ba₈CoRh₆O₂₁ represents the first example of an m = 5, n = 3 member of the A_3n+3mA'_nB_3m+nO_9m+6n family of 2H hexagonal perovskite related oxides and contains chains consisting of six …

Tris(Ethylenediamine)Cobalt(Iii) Nonaiododibismuthate, Andrea Goforth, Rachael Hipp, Mark Smith, Leroy Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The asymmetric unit of the title compound, [Co(C₂H₈N₂)₃][Bi₂I₉], crystallizes in the orthorhombic space group Cmc2₁. The asymmetric unit contains half of a [Co(en)₃]³⁺ cation (en is ethylenediamine) and half of a [Bi₂I₉]^3- anion. Both species are located on mirror planes, requiring the [Co(en)₃]³⁺ cation to be present as a statistically disordered mixture of both enantiomeric forms. Crystals were grown solvothermally from an ethanol-water solvent mixture using rac-[Co(en)₃]I₃ and bismuth triiodide …

Sr3Znpto6 And Sr3Cdpto6, Mark D. Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

The flux synthesis of single crystals of the isostructural compounds tristrontium zinc platinum hexaoxide, Sr₃ZnPtO₆, and tristrontium cadmium platinum hexaoxide, Sr₃CdPtO₆, is reported. The compounds adopt the pseudo-one-dimensional rhombohedral K₄CdCl₆ structure type, and feature chains of face-shared distorted ZnO₆ or CdO₆ trigonal prisms and PtO₆ octahedra, surrounded by columns of Sr²⁺ ions. All transition metals are located on the threefold axis of symmetry, while the Sr²⁺ cations lie on twofold axes.

Formula: Sr₃ZnPtO₆ and Sr₃CdPtO₆

High Temperature Superconductivity In Y-Ba-Cu-O: Identification Of A Copper-Rich Superconducting Phase, Angelica Stacy, John Badding, Margret Gesselbracht, William Ham, Gary Holland, Renata Hoskins, Steven Keller, Clark Millikan, Hans Conrad Zur Loye

Hans Conrad zur Loye

For the past 15 years, advances in superconductivity have come about only slowly and even a 0.5 K increase in transition temperature was noteworthy. Until April 1986, the highest transition temperatures were near 23 K. At that time, Bednorz and Muller reported superconductivity in La-Ba-Cu-0 compounds above 30K. Following this breakthrough, there were further studies of these phases and superconductivity was found also in similar solids containing Sr and Ca instead of Ba. The superconducting phase was identified as a layered perovskite A2-xBxCu04 with tetragonal symmetry, where A = La3+ and B = Ca2+, Sr2+, or Ba2+. The Sr compounds …

Tetrakis(N-Ethyl-9-Oxo-4-Azonia-5-Aza-9h-Fluorene) Tetra-Μ3-Iodo-Hexa-Μ2-Iodo-Dodecaiodohexabismuthate, Meredith Tershany, Andrea Goforth, Mark Smith, Leroy Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The new iodobismuthate compound (C13H11N2O)4[Bi6I22] has been synthesized solvothermally by reacting BiI3, Zn(NO3)2·6H2O and 4,5-diazafluoren-9-one in a water/ethanol solvent mixture. The asymmetric unit of the compound contains two independent [N-ethyl-4,5-dafo]+ cations and one-half of a centrosymmetric [Bi6I22]4- anion. The average terminal Bi-I, Bi-2-I and Bi-3-I bond lengths in the anion are 2.8923 (2), 3.1403 (2) and 3.3022 (2) Å, respectively.

Three Unique Coordination Geometries Involving 1,2-Dimethoxy-4,5-Bis(2-Pyridylethynyl)Benzene, Jeffrey E. Fiscus, Sandra Shotwell, Ralph C. Layland, Mark D. Smith, Hans Conrad Zur Loye, Uwe H. F. Bunz

Hans Conrad zur Loye

Reaction of the new ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl) benzene with different metal centers under similar reaction conditions led to three distinct structure formation processes: molecular ring closure, dimerization, and polymer formation.

Alkyne Metathesis With Simple Catalyst Systems: Efficient Synthesis Of Conjugated Polymers Containing Vinyl Groups In Main Or Side Chain, Glen Brizius, Neil Pschirer, Winfried Steffen, Katherine Stitzer, Hans Conrad Zur Loye, Uwe Bunz

Hans Conrad zur Loye

The synthesis of novel conjugated polymers by acyclic diyne metathesis (ADIMET) is reported. These polymers are hybrids between poly(p-phenylenevinylene) and poly(p-phenyleneneethynylene) (PPE). They contain phenylene, ethynylene, and vinylene groups (PhPh, PPVE). Simple in situ catalysts formed from Mo(CO)6 and 4-chlorophenol were used to metathesize the dipropynyl(tetraalkyl)stilbene monomers. The monomers are made by a combination of Horner reactions and Heck-type couplings. The PPVEs form in high yields and are structurally defined. They show degrees of polymerization (Pn) of 30−220 repeating units (i.e. 60−450 benzene rings), demonstrating that the presence of the double bonds does not interfere with alkyne metathesis. The PPVEs …

Euknatao5: Crystal Growth, Structure And Photoluminescence Property, Irina Roof, Mark Smith, Sangmoon Park, Hans Conrad Zur Loye

Hans Conrad zur Loye

The synthesis, structure determination, and intrinsic luminescent properties of a new tantalate, EuKNaTaO5, are reported. Single crystals of the title compound were grown out of a reactive KOH/NaOH eutectic melt. Luminescence in many materials is activated by doping a rare earth cation into the solid matrix; we report undoped, all-rare earth EuKNaTaO5, which exhibits bright orange room temperature photoluminescence.

Tetraquabis(5-Fluorosaccharinato)Nickel(Ii), Larnelle Peterson, Jennifer Kelley, Leroy Peterson, Mark Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

In the centrosymmetric title complex, [Ni(C7H3FNO3S)2(H2O)4], the NiII atom exhibits a slightly distorted trans-NiN2O4 octahedral coordination. The nitrogen donors are provided by two 5-fluorosaccharinate ligands and the oxygen donors are provided by four water molecules. The crystal structure features O-HO and bifurcated O-H(F,O) hydrogen bonds, the latter involving the F atom of the 5-fluorosaccharinate ligand.

Catena-Poly[[Bis(Α-Thenoyltrifluoroacetonato)Copper(Ii)]-Μ-1,4-Di-4-Pyridyl-2,3-Diazabuta-1,3-Diene], William J. Perkins, Tamara Maxwell, Mark D. Smith, Leroy Peterson Jr., Hans Conrad Zur Loye

Hans Conrad zur Loye

In the one-dimensional title polymer, [Cu(C₈H₄F₃O₂S)₂(C₁₂H₁₀N₄)]_n or [Cu(L)₂(tta)₂] [tta is -thenoyltrifluoroacetonato and L is 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene], Cu²⁺ lies on a center of inversion. It is axially coordinated by two pyridyl N atoms from two different L ligands and equatorially coordinated by four O atoms from two chelating tta ligands. The ligand L propagates the one-dimensional chain structure by serving as a bridging ligand between two Cu octahedra via Cu-N coordinate bonds.

Observation Of An Oxygen Isotope Effect In Yba2Cu3O7, Kevin Leary, Hans Conrad Zur Loye, Steven Keller, Tanya Faltens, William Ham, James Michaels, Angelica Stacy

Hans Conrad zur Loye

A small decrease in Tc of 0.3 K to 0.5 K is observed when as much as 90% of the 16O in YBa2Cu3O7 is substituted with18O. This result is consistent with our observation that there is an oxygen isotope effect in La1.85Sr0.15CuO4, but in contrast with previous reports that there is no isotope effect for YBa2Cu3O7. This new result suggests that phonons play an important role in the electron-pairing mechanism in YBa2Cu3O7.

Observation Of An Isotope Shift In The Superconducting Transition Temperature Of La1.85Sr0.15Cuo4, Tanya Faltens, William Ham, Steven Keller, Kevin Leary, James Michaels, Angelica Stacy, Hans Conrad Zur Loye, Donald Morris, T Barbee, Marvin Cohen, Cohen Hoen, A Zettl

Hans Conrad zur Loye

An oxygen isotope shift is observed in superconducting La1.85Sr0.15CuO4 when 18O is substituted partially for 16O; the superconducting transition temperature Tc is lowered by 0.3 to 1.0 K in different samples. We examine these results using conventioanl phonon-mediated BCS theory and conclude that, for La1.85Sr0.15CuO4, phonons play an important role in the pairing mechanism.

Bis[Μ-1,2-Bis(2-Pyridyl)Ethyne-K2N:N']Bis[Aquadinitratocadmium(Ii)], Badruz Zaman, Matthew Davis, Mark Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

Two twisted 1,2-bis(2-pyridyl)ethyne ligands bridge two Cd²⁺ centers in the C₂-symmetric title complex, [Cd₂(NO₃)₄(-C₁₂H₈N₂)₂(H₂O)₂]. The bridging ligands arch across one another creating a `zigzag loop' molecular geometry. Two nitrate ions and a water molecule complete the irregular seven-coordinate Cd-atom environment. The dihedral angles between the equivalent pyridyl ring planes of the two independent ligands are 67.2 (1)°. O_water-HO_nitrate hydrogen bonding creates two-dimensional layers parallel to the ab plane.

Formula: [Cd₂(NO₃)₄(C …

Crystal Growth And Structure Determination Of Novel Barium Rhodates: Stepping Stones Towards 2h-Barho3, Katherine Stitzer, Ahmed Abed, Jacques Darriet, Hans Conrad Zur Loye

Hans Conrad zur Loye

Single crystals of two new barium rhodates were grown from a molten potassium carbonate flux. The new rhodates, Ba₁₁Rh₁₀O₃₀ and Ba₃₂Rh₂₉O₈₇, are structurally related to the 2H-hexagonal perovskite structure and are characterized by pseudo one-dimensional chains of alternating face-sharing trigonal prisms and octahedra. The structures of Ba₁₁Rh₁₀O₃₀ and Ba₃₂Rh₂₉O₈₇ were solved using the 4D superspace group approach in Jana2000. Ba₁₁Rh₁₀O₃₀, with a repeat of nine RhO₆ octahedra followed by one RhO_{6 …}

Trisodium Dicalcium Bismuth Hexaoxide, Irina Puzdrjakova, Rene Macquart, Mark Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

Single crystals of the title compound, Na3Ca2BiO6, were grown from a high-temperature reactive flux solution of Na2CO3. Na3Ca2BiO6 crystallizes as an ordered rock-salt structure (space group Fddd), in which the octahedral holes in the oxide array are filled by an ordered 3:2:1 arrangement of Na+, Ca2+ and Bi5+ cations. All atoms except for one O atom lie on special positions; site symmetries are as follows: Bi 222, Ca 2, Na 222 and 2, O 2.

Sm2Nairo6, A Monoclinically Distorted Double Perovskite, Samuel J. Mugavero Iii, Irina V. Puzdrjakova, Mark D. Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

Single crystals of the lanthanide-containing iridate, disamarium sodium iridium hexaoxide, Sm₂NaIrO₆, were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁/n and is a double perovskite, consisting of a 1:1 ordered rock-salt-type lattice of corner-shared NaO₆ and IrO₆ distorted octahedra. Samarium occupies the eightfold coordination site generated by the connectivity of the octahedra.

Ca4Pto6, J. Claridge, R. Layland, Hans Conrad Zur Loye

Hans Conrad zur Loye

Calcium platinum(IV) oxide has been synthesized from a flux and structurally characterized by single-crystal X-ray diffraction. It is isostructural with Sr₄PtO₆ [Randall & Katz (1959). Acta Cryst. 12, 519-521] and Ba₄PtO₆ [Wilkinson & Cheetham (1989). Acta Cryst. C45, 1672-1674].

Diaquabis(5-Fluoro-2-Hydroxybenzoato-Κo1)Zinc(Ii), Diana Rishmawi, Jennifer Kelley, Mark D. Smith, Leroy Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The title compound, [Zn(C₇H₄FO₃)₂(H₂O)₂], is a monomeric Zn^II complex. The Zn^II atom, which lies on a twofold rotation axis, is situated in a distorted tetrahedral environment composed of two monodentate carboxlyate O atoms and two water O atoms. O-HO hydrogen bonds link these units, forming sheets that are stacked along the c axis.

Di-Μ-Iodo-Bis[Diiodo(1,10-Phenanthroline)Bismuth(Iii)], M. Tershany, A. Goforth, M. Smith, L. Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The title bismuth-iodide compound, [Bi2I6(C12H8N2)2], has been synthesized solvothermally by reacting BiI3, Mn(CH3COO)2·4H2O, and 1,10-phenanthroline in an ethanol/water solvent mixture. The compound contains two bismuth centers that are each coordinated by a phenanthroline ligand and two terminal iodide ligands, and the bismuth centers are bridged via two additional iodide ligands to form a molecular dimer. The asymmetric unit of the compound consists of one half of a single dimer molecule located on a crystallographic inversion center.

Tetraaquabis(3-Fluoropyridine-4-Carboxylato-Κn)Zinc(Ii) Dihydrate, Jonetha Fleming, Jennifer Kelley, Leroy Peterson, Mark Smith, Hans Conrad Zur Loye

Hans Conrad zur Loye

In the title compound, [Zn(C₆H₃FNO₂)₂(H₂O)₄]·2H₂O, the Zn^II atom is octahedrally coordinated in a ZnO₄N₂ environment by two 3-fluoropyridine-4-carboxylate (3-fpy4-cbx) ligands and four water molecules. The [Zn(3-fpy4-cbx)₂(H₂O)₄] molecules form a three-dimensional network through strong O-HO and weak O-HF hydrogen bonds between 3-fpy4-cbx and water molecules. The crystal used for data collection was a twin, with the twin law corresponding to a 180° rotation about the real-space [001] axis. The major twin fraction refined to 0.795 (1).

Catena-Poly[[Diaquadinitratozinc(Ii)]Bis(Μ-1,4-Di-3-Pyridyl-2,3-Diaza-1,3-Butadiene)], Shakoya Paulin, Pierre Kelly, Kenneth Williams, Andrea Goforth, Mark Smith, Leroy Peterson, Hans Conrad Zur Loye

Hans Conrad zur Loye

The polymeric title complex, [Zn(NO3)2(C24H20N8)(H2O)2]n, features distorted ZnN2O4 octahedra with each ZnII atom being located on an inversion center. Adjacent Zn ions are doubly bridged by two equivalent 1,4-di-3-pyridyl-2,3-diaza-1,3-butadiene ligands to form linear chains.