排序方式: 共有60条查询结果,搜索用时 15 毫秒
11.
Jacek Zaleski Zdzisaw Daszkiewicz Janusz B. Kyzio 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(6):754-757
In the title compounds, C6H8N3O2+·NO3? and C5H6N3O2+·CH3SO3?, respectively, the cations are almost planar; the twist of the nitramino group about the C—N and N—N bonds does not exceed 10°. The deviations from coplanarity are accounted for by intermolecular N—H?O interactions. The coplanarity of the NHNO2 group and the phenyl ring leads to the deformation of the nitramino group. The C—N—N angle and one C—C—N angle at the junction of the phenyl ring and the nitramino group are increased from 120° by ca 6°, whereas the other junction C—C—N angle is decreased by ca 5°. Within the nitro group, the O—N—O angle is increased by ca 5° and one O—N—N angle is decreased by ca 5°, whereas the other O—N—N angle remains almost unchanged. The cations are connected to the anions by relatively strong N—H?O hydrogen bonds [shortest H?O separations 1.77 (2)–1.81 (3) Å] and much weaker C—H?O hydrogen bonds [H?O separations 2.30 (2)–2.63 (3) Å]. 相似文献
12.
13.
V. V. Prezhdo A. S. Bykova O. V. Prezhdo Z. Daszkiewicz J. B. Kyziol J. Zaleski 《Russian Journal of General Chemistry》2006,76(1):64-75
Ten mono-, di-, and trinitro derivatives of N-methyl-N-nitroaniline were synthesized and studied by spectral, electrooptical, and quantum-chemical methods. Three of these derivatives, N-methyl-N,2,3-trinitroaniline, N-methyl-N,2,5-trinitroaniline, N-methyl-N,3,5-trinitroaniline, were also examined by the X-ray diffraction method. The N-nitroamino group in their molecules is almost planar, the N7-N8 bond is shortened, and the N8 atom is characterized by a strong deficit of electron density. The dihedral angle between the planes of the N-nitroamino group and the benzene ring is 56°–92°, which makes conjugation between these fragments impossible. The N-nitroamino group in the examined compounds acts as a weak electron donor with respect to the nitro groups in the aromatic ring; the mechanism of this effect is inductive. 相似文献
14.
15.
Melnychuk Khrystyna Marchuk Oleg Daszkiewicz Marek Gulay Lubomir 《Structural chemistry》2020,31(5):1945-1957
Structural Chemistry - The crystal structures of quaternary R3Fe0.5SnS7, R3Co0.5SnS7 and R3Ni0.5SnS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) compounds of La3Mn0.5SiS7 structure type (space... 相似文献
16.
L. D. Gulay M. Daszkiewicz I. P. Ruda O. V. Marchuk 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(3):i19-i21
Crystals of La2Pb(SiS4)2, dilanthanum(III) lead(II) bis[tetrasulfidosilicate(IV)], were obtained from the La–Pb–Si–S system and structurally characterized using X‐ray single‐crystal diffraction. The La and Pb atoms are coordinated in bicapped trigonal prisms of S atoms, with the Si atoms in tetrahedra. An occupational disorder of the La and Pb centres was refined for one position in the structure. The bicapped trigonal prisms and tetrahedra share edges. A gap located 2.629 (1) Å from the sulfide anions was found around the coordination polyhedra, which makes La2Pb(SiS4)2 a prospective material in crystal engineering. The Si and one S atom lie on a threefold axis. 相似文献
17.
18.
19.
The new organic–inorganic salt, 2,3-diaminopyridinium selenate, has been synthesized and characterized by means of single-crystal X-ray crystallography, FT-IR and FT-Raman spectroscopy. A diprotonated organic ligand, H21,3L2+, existing in the crystal structure was theoretically shown to be the most stable cationic species of 2,3-diaminopyridine. The weak non-covalent forces of N–H?O type between the hydrogen atoms of the amino and ammonio groups of 2,3-diaminopyridinium cation and oxygen atoms of tetrahedral selenate anions determine three-dimensional arrangement with complex network of intermolecular interactions of hydrogen bond type (donor–acceptor distances from 2.697(3) Å to 3.088(3) Å). Vibrational spectra have been discussed in comparison with X-ray results. Juxtaposition of spectra of the complex with the pure organic ligand and deuterated analogue of the title compound allowed to give reliable assignments of most observed vibrational bands. Presented data can be useful in elucidation of molecular mechanism of uptake of tetrahedral SeO42− anion by the living organisms. 相似文献
20.
Let
and
be a reductive dual pair of the type mentioned in the title, with
the smaller member. Let and be unitary representations of
,
which occur in Howe's correspondence. We express the distribution character of in terms of the character of via an explicit integral kernel operator.Oblatum 4-I-1995Research partially supported by the1UMK Grant 514-M, and the2NSF Grant DMS 9204488. 相似文献