Search results for "bonds"
showing 10 items of 155 documents
Three phenanthroline-metal complexes with topologically similar but geometrically different conformations.
2016
Two out of the three very similar complexes described present twofold symmetry but not the third one, probably by way of a strong intramolecular C—H⋯O hydrogen bond disrupting the symmetry, a fact which is analysed in detail.
The structure of bis(trimethylammonium) undecachlorotriantimonate(III) [(CH3)3NH]2Sb3Cl11 containing a novel antimony(III) anion
1999
The structure of [(CH3)3NH]2Sb3Cl11 (space group P21/n; a = 10.374(2), b = 23.723(5), c = 11.884(2) Å, β = 113.46(3)°; V = 2682.9(9) Å3) consists of a structurally novel [Sb3Cl2−11] anion and two crystallographically nonequivalent trimethylammonium cations. The anion is composed of three deformed octahedra in the asymmetric part of the unit cell. The octahedra are connected with each other by edges and corners forming a characteristic polyanionic layer. Trimethylammonium cations, one ordered and one disordered, are connected to the inorganic sublattice by N—H· · ·Cl hydrogen bonds.
Crystal structure of allylammonium hydrogen succinate at 100 K
2014
The asymmetric unit of the title compound, C2H8N+·C4H5O4−, consists of two allylammonium cations and two hydrogen succinate anions (Z′ = 2). One of the cations has a near-perfectsyn-periplanar (cis) conformation with an N—C—C—C torsion angle of 0.4 (3)°, while the other is characterized by agaucheconformation and a torsion angle of 102.5 (3)°. Regarding the anions, three out of four carboxilic groups are twisted with respect to the central C–CH2–CH2–C group [dihedral angles = 24.4 (2), 31.2 (2) and 40.4 (2)°], the remaining one being instead almost coplanar, with a dihedral angle of 4.0 (2)°. In the crystal, there are two very short, near linear O—H...O hydrogen bonds between anions, with t…
Crystal structure of 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate
2016
In the title molecular salt 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate, N—H⋯(O,O) and O—H⋯O hydrogen bonds link the components into a bilayer-like assembly.
Host-guest complexes of C-propyl-2-bromoresorcinarene with aromatic N-oxides*
2018
The host-guest complexes of C-propyl-2-bromoresorcinarene with pyridine N-oxide, 3-methylpyridine N-oxide, quinoline N-oxide and isoquinoline N-oxide are studied using single crystal X-ray crystallography and 1H NMR spectroscopy. The C-propyl-2-bromoresorcinarene forms endo-complexes with the aromatic N-oxides in the solid-state when crystallised from either methanol or acetone. In solution, the endo-complexes were observed only in methanol-d4. In DMSO the solvent itself is a good guest, and crystallisation provides only solvate endo-complexes. The C-propyl-2-bromoresorcinarene shows remarkable flexibility when crystallised from either methanol or acetone, and packs into one-dimensional sel…
Crystal structure of (2R*,3aR*)-2-phenylsulfonyl-2,3,3a,4,5,6-hexahydropyrrolo[1,2-b]isoxazole
2017
The title compound, C12H15NO3S, was prepared by 1,3-dipolar cycloaddition of 3,4-dihydro-2H-pyrrole 1-oxide and phenyl vinyl sulfone. In the molecule, both fused five-membered rings display a twisted conformation. In the crystal, C—H...O hydrogen bonds link neighbouring molecules, forming chains running parallel to thebaxis.
5-Acetyl-6-methyl-4-phenyl-1-(prop-2-ynyl)-3,4-dihydropyrimidin-2(1H)-one
2017
The 4-dihydropyrimidin-2(1H)-one moiety of the title molecule, C16H16N2O2, displays a half-chair conformation. The least-squares mean plane through this heterocycle is almost perpendicular to the aromatic ring [dihedral angle = 89.52 (8)°] and to the prop-2-ynyl chain [C—C—N—C torsion angle of −73.2 (2)°]. The mean plane through the acetyl group makes a dihedral angle of 30.93 (10)° with the mean plane of the heterocycle. There is an intramolecular C—H...O hydrogen bond forming anS(6) ring motif. In the crystal, molecules are linked by pairs of N—H...O hydrogen bonds forming inversion dimers.
Crystal structure, spectroscopic characterization and Hirshfeld surface analysis of trans-diaqua[2,5-bis(pyridin-4-yl)-1,3,4-oxadiazole]dithioc…
2019
The NiII atom in the mononuclear title complex has an almost regular octahedral N4O2 coordination geometry. In the crystal, the complex molecules are linked in a three-dimensional network through strong O—H⋯N hydrogen bonds.
Crystal structure and Hirshfeld surface analysis of [N(CH3)4][2,2′-Fe(1,7-closo-C2B9H11)2]
2017
This work investigates the meta-ferrabis(dicarbollide) anion that was isolated as salt of tetramethylammonium. The structure of the obtained crystal consisted of discrete [2,2′-Fe(1,7-closo-C2B9H11)2]− anions and disordered [N(CH3)4]+ cations. The anion had a considerable chemical stability ensured by ionic and Van der Waals interactions. Thus, Hirshfeld surfaces and fingerprint plot were used to visualize, explore, and quantify intermolecular interactions in the crystal lattice of the title compound. This investigation proved that close contacts were dominated by H⋯H interactions. peerReviewed
Notations et écarts de rentabilité : le marché français avant l'euro
2003
The main task of this paper is to confront two classical measures of default risk of the issuer, the rating and the spread. The first is attributed by agencies specialized in this activity (Standard and Poor's or Moody's) while the second results directly from the market price of the bond. This article studies this link over a period of two years for about forty French denominated bonds. Two measures of the spread are used and the results obtained show the very partial consideration of this information by the investors on the French bond market.