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  • International Union of Crystallography (IUC)  (18)
  • Oxford University Press  (10)
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  • 1
    Publication Date: 2013-10-03
    Description: In the binuclear title compound, [Ag2(C11H11N3)2](ClO4)2·2C2H6SO, the complex cation is centrosymmetric, with the unique AgI cation coordinated by two pyridine N atoms from two symmetry-related N-(pyridine-2-ylmethyl)pyridine-3-amine ligands in a geometry slightly distorted from linear [N—Ag—N = 170.78 (9)°], resulting in the formation of a 16-membered cyclic dimer. The two pyridine rings coordinating to the AgI atom are almost perpendicular to each other [dihedral angle = 87.73 (10)°]. Intermolecular Ag...O interactions [3.149 (3) and 2.686 (3) Å], N—H...O and C—H...O hydrogen bonds and C—H...π interactions between the cyclic dimers and the anions or the solvent molecules lead to the formation of a three-dimensional supramolecular network.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 2
    Publication Date: 2016-06-18
    Description: In the title compound, {[Ag(C29H25N3)2]NO3·CH3OH·H2O}n, the AgI cation is four-coordinated by two pyridine N atoms and two imidazole N atoms from four individual 4-(1-(5′-isopropyl-[1,1′:3′,1′′-terphenyl]-2′-yl)-1H-imidazol-2-yl)pyridine (i-pro-pyim) ligands. This gives rise to a highly distorted tetrahedral geometry with bond angles falling in the range 100.33 (19)–122.76 (19)°. Two crystallographically independent i-pro-pyim ligands (A and B) adopt very similar conformations to one another, such that the dihedral angles between the pyridyl and imidazolyl rings in the two ligands are 40.7 (3) and 42.2 (3)°, respectively. Each i-pro-pyim ligand binds two symmetry-related Ag+ cations, leading to the formation of 14-membered cyclic dimers, in which the AgI atoms are separated by 6.963 (2) Å for the Ag–A2–Ag dimer and 7.020 (2) Å for Ag–B2–Ag. These cyclic dimers are alternately connected to each other by sharing AgI atoms, resulting in the formation of a looped-chain structure extending along the [100] direction. Moreover, adjacent looped chains are connected by intermolecular π–π interactions [centroid-to-centroid distance = 3.689 (4) Å], giving rise to the formation of a two-dimensional supramolecular network propagating parallel to (110). Several intermolecular C—H...O and O—H...O hydrogen bonds further contribute to the stabilization of the crystal structure.
    Keywords: crystal structuresilver(I)pyridylimidazol ligandlooped-chain coordination polymer
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 3
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    International Union of Crystallography (IUC)
    Publication Date: 2011-05-08
    Description: The title compound, C11H11N3, crystallizes with two molecules (A and B) in the asymmetric unit. The geometries of both molecules are very similar, with the exception of the torsion angles of the inter-ring chains; the values for C—N—C—C are 67.4 (5) and −69.3 (5)° for molecules A and B, respectively. The dihedral angles between the pyridyl ring planes are 84.0 (2) and 83.2 (2)° for molecules A and B, respectively. In the crystal, weak intermolecular N—H...N hydrogen bonds and C—H...π interactions contribute to the stabilization of the packing.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 4
    Publication Date: 2012-02-02
    Description: Java embedded systems often include Java middleware classes installed on the client device. For higher performance, they can be compiled into machine code before runtime using an ahead-of-time compiler (AOTC). There are many approaches to AOTC, yet a bytecode-to-C (b-to-C) AOTC which translates the bytecode into the C code and then compiles it using an existing optimizing compiler such as gcc would be the most straightforward one. This paper explores a few important design and optimization issues of a b-to-C AOTC, including the compilation form for the translated C code, the call interfaces among translated and interpreted Java methods, and Java-specific optimizations by the AOTC that can complement the gcc optimizations. We evaluate these issues with our b-to-C AOTC implemented on the MIPS platform for the Sun's CDC VM to understand their performance impact.
    Print ISSN: 0010-4620
    Electronic ISSN: 1460-2067
    Topics: Computer Science
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  • 5
    Publication Date: 2013-01-19
    Description: Levels of gene expression show considerable variation in eukaryotes, but no fine-scale maps have been made of the fitness consequences of such variation in controlled genetic backgrounds and environments. To address this, we assayed fitness at many levels of up- and down-regulated expression of a single essential gene, LCB2 , involved in sphingolipid synthesis in budding yeast Saccharomyces cerevisiae . Reduced LCB2 expression rapidly decreases cellular fitness, yet increased expression has little effect. The wild-type expression level is therefore perched on the edge of a nonlinear fitness cliff. LCB2 is upregulated when cells are exposed to osmotic stress; consistent with this, the entire fitness curve is shifted upward to higher expression under osmotic stress, illustrating the selective force behind gene regulation. Expression levels of LCB2 are lower in wild yeast strains than in the experimental lab strain, suggesting that higher levels in the lab strain may be idiosyncratic. Reports indicate that the effect sizes of alleles contributing to variation in complex phenotypes differ among environments and genetic backgrounds; our results suggest that such differences may be explained as simple shifts in the position of nonlinear fitness curves.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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  • 6
    Publication Date: 2012-07-05
    Description: The title 1:1 co-crystal, C6H12N2·C6H6O4, the dicarboxylic acid molecule is close to planar [r.m.s. deviation from the mean plane = 0.07 (1) Å]. In the crystal, the two molecules are arranged alternately and are linked by O—H...N hydrogen bonds, leading to the formation of a chain along the [20\overline 1] direction. The chains are assembled into a two-dimensional framework parallel to the (102) plane through weak C—H...O hydrogen bonds between the two types of molecules.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 7
    Publication Date: 2011-11-17
    Description: In the binuclear title compound, [Ag2(C11H11N3)2](CF3O3S)2, the complex cation is centrosymmetric, with the unique Ag+ cation coordinated by two pyridine N atoms from two symmetry-related N-(pyridin-2-ylmethyl)pyridin-2-amine ligands in a geometry slightly distorted from linear [N—Ag—N 161.02 (7)°]. This set-up leads to the formation of a 14-membered cyclic dimer. The two pyridine rings coordinated to the Ag+ cation are tilted by 80.19 (7)° with respect to each other. Intermolecular N—H...O hydrogen-bonding interactions between the cyclic dimer and the anion exist. A two-dimensional network parallel to the ac plane is constructed by three weak Ag...(O,N) interactions as well as an F...F contact of 2.890 (4) Å.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 8
    Publication Date: 2011-02-03
    Description: The title compound, C18H16N6·2CH3OH, was prepared by the reaction of 5,5′-bis(bromomethyl)-2,2′-bipyridine with imidazole. The main molecule lies on an inversion center located at the mid-point of the C—C bond joining the two pyridine rings. The asymmetric unit therefore contains one half-molecule and one methanol solvent molecule. The dihedral angle between the pyridine and imidazole rings is 72.32 (5)°. In the crystal, weak intermolecular O—H...N, C—H...N and C—H...O hydrogen bonds contribute to the stabilization of the packing.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 9
    Publication Date: 2014-10-26
    Description: In the asymmetric unit of the title compound, {[Ag(C11H11N3)]CF3SO3}n, there are two AgI atoms, two N-(pyridine-2-ylmethyl)pyridine-3-amine ligands (A and B) and two CF3SO3− anions. Both AgI atoms are bridged by two pyridine N atoms from two symmetry-related A or B ligands, forming right- or left-handed helical chains, respectively. The AgI atom of the right-handed helical chain adopts a slightly distorted linear coordination geometry [N—Ag—N = 170.69 (14)°], while that of the left-handed helical chain adopts a bent geometry [N—Ag—N = 149.42 (14)°]. Both helical chains have the same pitch length [10.8437 (5) Å], propagate along the b-axial direction and are alternately arranged via Ag...Ag [3.0814 (5) Å] and π–π stacking interactions [centroid–centroid distances = 3.514 (3) and 3.487 (3) Å], resulting in the formation of a two-dimensional supramolecular network extending parallel to the ab plane. Weak Ag...O [2.861 (4), 2.617 (3), and 2.624 (4) Å] and Ag...F [3.017 (3) Å] interactions as well as N—H...O and C—H...O, C—H...N and C—H...F hydrogen-bonding interactions occur between the helical chains and the anions.
    Keywords: crystal structuresilver(I)unsymmetrical dipyridyl ligandhelical chain coordination polymer
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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  • 10
    Publication Date: 2014-05-25
    Description: In the title polymeric complex, {[Ag(C11H11N3)]PF6}n, the AgI ion is two-coordinated in a nearly linear coordination geometry [N—Ag—N = 175.98 (9)°] by two pyridine N atoms from two symmetry-related N-[(pyridine-2-yl)methyl]pyridine-3-amine ligands. Each AgI ion is bridged by the ligands, forming a helical chain propagating along the b-axis direction. The right- and left-handed helical chains are alternately arranged via Ag...Ag [3.2639 (5) Å] and π–π stacking interactions [centroid–centroid distance = 3.523 (1) Å], resulting in the formation of a two-dimensional supramolecular network extending parallel to (101). Weak Ag...F interactions [longest Ag...F interaction = 3.153 (2) Å], as well as N—H...F and C—H...F hydrogen-bonding interactions, occur between the helical chains and the anions.
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
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