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71.
Misa V. Jovanovic Edward R. Biehl Patrice De Meester Shirley S. C. Chu 《Journal of heterocyclic chemistry》1984,21(5):1425-1429
The crystal structure of title compound, 4 , shows that the 10-aryl group is parallel to the plane bisecting the pyridobenzothiazine ring. This structure is in contrast to that normally found for phenothiazines substituted with electron-withdrawing substituents on the 10-phenyl ring. In those compounds, the 10-aryl group is perpendicular to the plane bisecting the phenothiazine ring. The esr spectrum of the cation radical of 4 shows that the radical is located on the hetero ring system which is opposite to that of the cation radical of 4′-dimethylamino-10-phenylphenothiazine in which the radical is located on the 10-aryl ring. 相似文献
72.
The title compound was obtained by reduction of diethyl (ferrocenylmethyl)malonate with lithium aluminium hydride in diethyl ether. The structure of this novel ferrocene derivative was assigned by means of elemental analysis, IR, [1H]NMR, and [13C]NMR spectroscopy. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic P21/a space group with unit cell dimensions: a = 9.7360(6), b = 27.040(5), c = 14.767(3) Å, = 103.835(6)°, V = 3774.8(11) Å3, Z = 12. The asymmetric unit contains three crystallographically independent molecules. In the ferrocenyl moieties, the Fe–C bond distance values are in the range 2.006(5)—2.051(3) Å and C–C distances in the range 1.366(7)–1.425(4) Å. The cyclopentadienyl rings in each of the molecules are mutually twisted by about 13° from the eclipsed conformation. The hydroxyl groups are involved in the intermolecular O–H...O hydrogen bond formation with O-O distances in the range 2.686(3)–2.801(4) Å forming infinite two-dimensional network in a [0 0 1] plane. The crystal structure is additionally stabilized by C–H-O weak intermolecular hydrogen bonds. 相似文献
73.
Zora Popovi
eljka Soldin Gordana Pavlovi 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(7):m272-m274
The title compound, [Hg(C6H4NO2)I(C6H5NO2)], has twofold symmetry along the Hg—I bond. The HgII ion coordinates one I atom [at 2.6045 (4) Å], two N and two O atoms [at 2.298 (3) and 2.481 (2) Å] from one picolinate ion, and one picolinic acid molecule in a very irregular trigonal–bipyramidal coordination. The single hydroxy H atom required for chemical neutrality is both statistically (by crystal symmetry) and structurally disordered, and is involved in an intermolecular O—H⋯O hydrogen bond [O⋯O = 2.455 (4) Å], connecting the molecules into one‐dimensional infinite chains along the [101] direction. 相似文献
74.
Gordana Pavlovi Lidija Barii Vladimir Rapi Veronika Kova
《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):m55-m57
Heteroannularly substituted ferrocene derivatives can act as model systems for various hydrogen‐bonded assemblies of biomolecules formed, for instance, by means of O—H⋯O and N—H⋯O hydrogen bonding. The crystal structure analysis of 1′‐(tert‐butoxycarbonylamino)ferrocene‐1‐carboxylic acid, [Fe(C10H14NO2)(C6H5O2)] or (C5H4COOH)Fe(C5H4NHCOOC(CH3)3, reveals two independent molecules within the asymmetric unit, and these are joined into discrete dimers by two types of intermolecular hydrogen bonds, viz. O—H⋯O and N—H⋯O. The –COOH and –NHCOOR groups are archetypes for dimer formation via two eight‐membered rings. The O—H⋯O hydrogen bonds [2.656 (3) and 2.663 (3) Å] form a cyclic carboxylic acid dimer motif. Another eight‐membered ring is formed by N—H⋯O hydrogen bonds [2.827 (3) and 2.854 (3) Å] between the N—H group and an O atom of another carbamoyl moiety. The dimers are assembled in a herring‐bone fashion in the bc plane. 相似文献
75.
Ivanka Matijai Gordana Pavlovi Rudolf Trojko Jr 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o184-o186
The X‐ray crystal structure analysis of the title compound, C17H30O8, revealed a 4C1 conformation of the pyranosyl ring [Cremer–Pople puckering parameters of Q = 0.568 (2) Å, θ = 5.1 (2) and ϕ = 218 (3)°]. The structure shows no deviations from the geometric parameters of pyranoside carbohydrates. The hydroxyl groups participate in O—H⃛O hydrogen bonds, forming a two‐dimensional pattern [O⃛O = 2.811 (3) and 2.995 (3) Å]. 相似文献
76.
Boris-Marko Kukovec Zora Popović Gordana Pavlović Marijana Vinković Dražen Vikić-Topić 《Polyhedron》2008
Cadmium(II) complexes of 3-hydroxypicolinic acid, namely [CdI(3-OHpic)(3-OHpicH)(H2O)]2 (1), [Cd(3-OHpic)2(H2O)2] (2) and [Cd(3-OHpic)2]n (3) were prepared and characterized by spectroscopic methods (IR, NMR) and their molecular and crystal structures were determined by X-ray crystal structure analysis. Complexes 1 and 2 were prepared in similar reaction conditions using different cadmium(II) salts: cadmium(II) iodide and cadmium(II) acetate dihydrate, respectively, while 3 was prepared by recrystallization of 2 from N,N-dimethylformamide solution. Various coordination modes of 3-OHpicH in 1–3 were established in the solid state: bidentate N,O-chelated mode in 1 and 2, monodentate mode through the carboxylate O atom from zwitterionic ligand in 1 and bidentate N,O-chelated and bridging mode in 3. In the DMF solution of all prepared complexes, only monodentate mode of 3-OHpicH binding to cadmium(II) through the carboxylate O atom was established by 1H, 13C, 15N and 113Cd NMR spectroscopy. 相似文献
77.
78.
S. De Nicola R. Fedele D. Jovanovic B. Malomed M. A. Man'ko V. I. Man'ko P. K. Shukla 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):113-119
We present one-dimensional (1D) stability analysis of a recently
proposed method to filter and control localized states of the
Bose–Einstein condensate (BEC), based on novel trapping
techniques that allow one to conceive methods to select a
particular BEC shape by controlling and manipulating the external
potential well in the three-dimensional (3D)
Gross–Pitaevskii equation (GPE). Within the framework of this
method, under suitable conditions, the GPE can be exactly
decomposed into a pair of coupled equations: a transverse
two-dimensional (2D) linear Schr?dinger equation and a
one-dimensional (1D) longitudinal nonlinear Schr?dinger
equation (NLSE) with, in a general case, a time-dependent
nonlinear coupling coefficient. We review the general idea how
to filter and control localized solutions of the GPE. Then,
the 1D longitudinal NLSE is numerically solved
with suitable non-ideal controlling potentials that differ from
the ideal one so as to introduce relatively small errors
in the designed spatial profile. It is shown that a BEC with an
asymmetric initial position in the confining potential exhibits
breather-like oscillations in the longitudinal direction but,
nevertheless, the BEC state remains confined within the potential
well for a long time. In particular, while the condensate remains
essentially stable, preserving its longitudinal soliton-like
shape, only a small part is lost into “radiation”. 相似文献
79.
We consider the problems of finding the maximum number of vertex-disjoint triangles (VTP) and edge-disjoint triangles (ETP) in a simple graph. Both problems are NP-hard. The algorithm with the best approximation ratio known so far for these problems has ratio 3/2+?, a result that follows from a more general algorithm for set packing obtained by Hurkens and Schrijver [On the size of systems of sets every t of which have an SDR, with an application to the worst-case ratio of heuristics for packing problems, SIAM J. Discrete Math. 2(1) (1989) 68-72]. We present improvements on the approximation ratio for restricted cases of VTP and ETP that are known to be APX-hard: we give an approximation algorithm for VTP on graphs with maximum degree 4 with ratio slightly less than 1.2, and for ETP on graphs with maximum degree 5 with ratio 4/3. We also present an exact linear-time algorithm for VTP on the class of indifference graphs. 相似文献
80.
Gordana S. Risti? Milan S. Trtica Nebojša ?. Rom?evi? 《Applied Surface Science》2007,253(12):5233-5239
Diamond coatings were deposited by synergy of the hot filament CVD method and the pulse TEA CO2 laser, in spectroactive and spectroinactive diamond precursor atmospheres. Resulting diamond coatings are interpreted relying on evidence of scanning electron microscopy as well as microRaman spectroscopy. Thermal synergy component (hot filament) possesses an activating agent for diamond deposition, and contributes significantly to quality and extent of diamond deposition. Laser synergy component comprises a solid surface modification as well as the spectroactive gaseous atmosphere modification. Surface modification consists in changes of the diamond coating being deposited and, at the same time, in changes of the substrate surface structure. Laser modification of the spectroactive diamond precursor atmosphere means specific consumption of the precursor, which enables to skip the deposition on a defined substrate location. The resulting process of diamond coating elimination from certain, desired locations using the CO2 laser might contribute to tailoring diamond coatings for particular applications. Additionally, the substrate laser modification could be optimized by choice of a proper spectroactive precursor concentration, or by a laser radiation multiple pass through an absorbing medium. 相似文献