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21.
P. S. Pereira Silva M. Ramos Silva J. A. Paixão A. Matos Beja 《Journal of chemical crystallography》2009,39(9):669-671
Abstract A new complex of diphenylhydantoin, pentaaquabis[(5,5-diphenylhydantoinato)potassium], has been synthesized and the structure
has been solved by X-ray diffraction. The crystals are monoclinic, space group C2/c, with a = 34.959(5) ?, b = 8.273(4) ?, c = 11.692(2) ?, β = 109.069(13)°, M
r = 670.80, V = 3196.0(17) ?3, Z = 4 and R = 0.050. The potassium cations are assembled in dimers bridged through the carbonyl O atoms of the anions. The metal atom
is in a distorted octahedral coordination environment.
Index Abstract In pentaaquabis[(5,5-diphenylhydantoinato)potassium] the potassium cations are coupled in dimers through the carbonyl O atoms
of the anions.
相似文献
22.
M. Ramos Silva J. A. Paixo A. Matos Beja L. Alte da Veiga 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):104-106
There are two symmetry‐independent formula units of the title compound, C6H15N4O2+·F?·HF, per cell. Both cations have a zwitterionic form, protonated at both the guanidyl and amino groups. The two symmetry‐independent cations differ in their conformation. In one of them the Cγ atom is in a gauche position to both the amino and carboxyl groups, while in the other this atom is trans to the amino group. The two anions have very similar geometry. The F? ions are strongly hydrogen bonded to an HF molecule [F—H?F 2.233 (2) and 2.248 (3) Å], thereby forming an asymmetric non‐linear bifluoride anion. These F?F distances are the shortest reported for an asymmetric HF2? anion. 相似文献
23.
M. Ramos Silva A. Matos Beja L. Alte da Veiga J. A. Paixo A. J. F. N. Sobral N. G. C. L. Rebanda A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):1136-1138
The title compound, C27H37N, which is intended to be included in the structure of a sulfonamide porphyrin for the preparation of Langmuir–Blodgett films, consists of a dodecyl chain linked to an anthracene molecule through an aminomethyl group. The angle between the least‐squares plane of the anthracene and the dodecyl chain is 11.44 (8)°. The molecules are arranged in zigzag layers head‐to‐head, with the hydrocarbon chains side‐by‐side. The structure is stabilized by C—H?π interactions, the strongest having an H?centroid distance of 2.63 Å. 相似文献
24.
M. Ramos Silva A. Matos Beja J. A. Paixo L. Alte da Veiga A. J. F. N. Sobral A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):1263-1264
In the title compound, C16H17NO4, the benzyloxycarbonyl group is anti to the pyrrolic N atom. The molecules are joined into head‐to‐head dimers by hydrogen bonds involving the carboxylic acid groups. There is orientational disorder of these groups over two positions with approximately equal occupancy. A weaker hydrogen bond between the pyrrolic N atom and the carbonyl O atom of the benzyloxycarbonyl group joins the dimers into chains running parallel to the [110] direction. 相似文献
25.
J. A. Paixo A. Matos Beja M. Ramos Silva L. Alte da Veiga A. C. Serra 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1501-1502
In the title compound, C8H5Br2NO4, the endocyclic angles of the ring deviate significantly from the ideal value of 120°. The substituents deviate from the plane of the ring, with large twist angles for the aldehyde, nitro and methoxy groups. The geometry of the molecule in the crystal is compared with that of the isolated molecule, as given by a self‐consistent field molecular‐orbital Hartree–Fock calculation. Only weak hydrogen bonds of the C—H?Br and C—H?O types are present in the crystal structure. 相似文献
26.
27.
Pinho e Melo TM Soares MI Gonsalves AM Paixão JA Beja AM Silva MR 《The Journal of organic chemistry》2005,70(17):6629-6638
1-Azafulvenium methides, generated from pyrrolo[1,2-c]thiazole-2,2-dioxides' thermal extrusion of sulfur dioxide, led to the synthesis of functionalized pyrroles. The intramolecular trapping of these transient 8pi 1,7-dipoles in pericyclic reactions, namely sigmatropic [1,8]H shifts and 1,7-electrocyclization, allowed the synthesis of N-vinylpyrroles and C-vinylpyrroles which, under flash vacuum pyrolysis conditions, are converted into 5-oxo-5H-pyrrolizines or 4-oxo-1,4-dihydro-1-aza-benzo[f]azulenes, respectively. These heterocycles can also be obtained directly from FVP of pyrrolo[1,2-c]thiazole 2,2-dioxides. The synthesis and X-ray structure of a new 6-oxocyclopenta[b]pyrrole derivative is also reported. 相似文献
28.
V. H. Rodrigues J. A. Paixo M. M. R. R. Costa A. Matos Beja 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(11):o658-o660
In the title compound, C2H6NO2+·C2F3O2?, the main N—C—COOH skeleton of the glycinium cation is almost perfectly planar. The trifluoroacetate anion has a staggered conformation with typical bond distances and angles. The CF3 group is slightly disordered. The structure is stabilized by an extensive network of strong O—H?O hydrogen bonds and weaker N—H?O bonds. 相似文献
29.
30.
Jos Antnio Paixo Manuela Ramos Silva Ana Matos Beja Abílio J. F. N. Sobral Susana H. Lopes A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o721-o723
In the title compound, C15H17NO2, the ethoxycarbonyl group is anti with respect to the pyrrole N atom. The angle between the planes of the phenyl and pyrrole rings is 48.26 (9)°. The molecules are joined into dimeric units by a strong hydrogen bonds between pyrrole N—H groups and carbonyl O atoms. The geometry of the isolated molecule was studied by ab initio quantum mechanical calculations, employing both molecular orbital Hartree–Fock (MO–HF) and density functional theory (DFT) methods. The minimum energy was achieved for a conformation where the angle between the planes of the phenyl and pyrrole rings is larger, and that between the ethoxycarbonyl and pyrrole planes is smaller than in the solid‐state molecule. 相似文献