256 research outputs found
2,3,4,6-Tetra-O-benzoyl-4-nitrophenyl-1-thio-α-d-mannopyranoside–dichloromethane–diethyl ether mixed solvate (1/0.53/0.38)
The title compound, C40H31NO11S·0.53CH2Cl2·0.38C4H10O, was synthesized in two steps from mannose pentaacetate and single crystals were grown by slow evaporation. The structure was determined by single-crystal X-ray diffraction, confirming the α-configuration of the anomeric thioaryl substituent. The asymmetric unit contains two crystallographically distinct molecules of the carbohydrate. The central pyranose rings of these are geometrically similar, but there are differences in the orientations of the benzoate substituents
8-Chloro-5,5-dimethyl-5,6-dihydrotetrazolo[1,5-c]quinazoline
In the title compound, C10H10ClN5, the tetrazole ring and the phenyl ring make a dihedral angle of 7.7 (2)°. The hexahydropyrimidine ring adopts a screw-boat conformation. In the crystal, intermolecular bifurcated N—H⋯(N,N) hydrogen bonds link the molecules into [001] chains
(2E,4E)-1-(6-Chloro-2-methyl-4-phenyl-3-quinolyl)-5-phenylpenta-2,4-dien-1-one
In the title compound, C27H20ClNO, the quinoline ring forms a dihedral angle of 62.53 (5)° with the substituent benzene ring. In the crystal, intermolecular C—H⋯Cl interactions link the molecules into chains along the b axis. Intermolecular C—H⋯N and C—H⋯O hydrogen bonds further consolidate the structure into a three-dimensional network. The unit cell contains four solvent-accessible voids, each with a volume of 35 Å3, but no significant electron density was found in them
N-Benzyl-1,3-dideoxy-1,3-imino-l-xylitol
The structure determination confirms the stereochemistry of the title compound, C12H17NO3, which contains a four-membered azetidine ring system. The absolute configuration was determined by the use of d-glucose as the starting material. In the crystal, O—H⋯O and O—H⋯N hydrogen bonds link the molecules into layers in the ab plane
4-Methoxyphenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-mannopyranoside
The title compound, C21H26O10S, was synthesized in a single step from mannose pentaacetate. The molecular structure confirms the α configuration of the anomeric thioaryl substituent. Spectroscopic and melting-point data obtained for the title compound are in disagreement with those previously reported, indicating the previously reported synthesis [Durette & Shen (1980 ▶). Carbohydr. Res. 81, 261–274] to be erroneous. The crystal structure is stabilized by weak intermolecular C—H⋯O hydrogen bonds
Investigation of high-pressure planetary ices by cryo-recovery. I. An apparatus for X-ray powder diffraction from 40 to 315 K, allowing 'cold loading' of samples
A low-temperature stage for X-ray powder diffraction in Bragg–Brentano
reflection geometry is described. The temperature range covered is 40–315 K,
with a temperature stability at the sample within +-0.1 K of the set point. The
stage operates by means of a Gifford–McMahon (GM) closed-cycle He
refrigerator; it requires no refrigerants and so can run for an extended period (in
practice at least 5 d) without intervention by the user. The sample is cooled both
by thermal conduction through the metal sample holder and by the presence of
He exchange gas, at ambient pressure, within the sample chamber; the
consumption of He gas is extremely low, being only 0.1 l min-1 during normal
operation. Aunique feature of this cold stage is that samples may be introduced
into (and removed from) the stage at any temperature in the range 80–300 K,
and thus materials which are not stable at room temperature, such as highpressure
phases that are recoverable to ambient pressure after quenching to
liquid nitrogen temperatures, can be readily examined. A further advantage of
this arrangement is that, by enabling the use of pre-cooled samples, it greatly
reduces the turnaround time when making measurements on a series of
specimens at low temperature
A microprocessor-controlled continuous-flow cryostat for single-crystal X-ray diffraction in the range 10–300 K
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Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2’:6’,2’’-terpyridine ligand: implications for actinide(III) /lanthanide(III) partitioning
The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of the 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO22+) ion were obtained by X-ray crystallographic analysis, and showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligand
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