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81.
Zhi‐Guo Zhong Yu‐Quan Feng Ping Zhang 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(8):833-836
A novel copper–niobium oxyfluoride, {[Cu2(C10H7N2O)2][NbOF4]}n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single‐crystal X‐ray diffraction. The structural unit consists of one C2‐symmetric [NbOF4]− anion and one centrosymmetric coordinated [Cu2(obpy)2]+ cation (obpy is 2,2′‐bipyridin‐6‐olate). In the [NbOF4]− anion, each NbV metal centre is five‐coordinated by four F atoms and one O atom in the first coordination shell, forming a square‐pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb—O = 2.187 (3) Å], forming an infinite linear {[NbOF4]−}n polyanion. In the coordinated [Cu2(obpy)2]+ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF4]− and [Cu2(obpy)2]+ units are assembled via weak C—H...F hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. π–π stacking interactions between the pyridine rings [centroid–centroid distance = 3.610 (2) Å] may further stabilize the crystal structure. 相似文献
82.
V. S. Moskvina Ya. L. Garazd M. M. Garazd A. V. Turov V. P. Khilya 《Chemistry of Heterocyclic Compounds》2007,43(4):421-429
Syntheses are reported for sulfur-and nitrogen-containing derivatives of 4-arylspiro-2-benzopyranones modified at the exocyclic
oxygen atom. The structure of these products was demonstrated by correlational NMR spectroscopy.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 518–527, April, 2007. 相似文献
83.
《Magnetic resonance in chemistry : MRC》2003,41(6):431-434
A new pulse sequence for determining scalar long range C,H spin couplings in small organic molecules is proposed. It is based on the combination of a selective J‐resolved spectrum with a selective HMBC and displays the long‐range spin couplings of one chosen carbon atom in the indirect dimension. Advantages and disadvantages are discussed on example spectra of ethanol, strychnine and sucrose. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
84.
《Magnetic resonance in chemistry : MRC》2003,41(3):177-182
We present a new pulse sequence that yields two simultaneously detected types of long‐range correlation spectra. The one spectrum is to show all nJ(C,H) connectivities and the other is to show exclusively 2J(C,H) connectivities. The method is demonstrated by using strychnine as a test sample. A comparison with HMBC shows that the 2J(C,H)/nJ(C,H) experiment supplies a nJ(C,H) spectrum that is of equal standard with regard to sensitivity and spectral information. The additional 2J(C,H) spectrum allows the disentanglement of 2J(C,H) and nJ(C,H) signals (n > 2) in HMBC type spectra, which greatly simplifies signal assignment and structure elucidation in general. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
85.
A continuous two-dimensional jet expansion in combination with an infrared diode laser spectrometer has been used to record a new subband of the weakly bound complex Ar-CO in the 2168cm?1 region. Twenty-two transitions were assigned to a thus far unobserved K a = 0 van der Waals state at 36.765 cm?l above the ground state. This is the highest van der Waals mode of Ar-CO reported so far. These high lying energy levels will provide a very sensitive test for future ab initio and Semiempirical potential energy surfaces. 相似文献
86.
《光谱学快报》2013,46(4):421-436
Abstract Phencyclone, 1, reacted with N‐(2,6‐dimethylphenyl)maleimide, 2a; with N‐(2,6‐diethylphenyl)maleimide, 2b; and with N‐(2,6‐diisopropylphenyl)maleimide, 2c, respectively, to yield the corresponding Diels–Alder adducts, 3a–c. The adducts were extensively characterized by NMR (7 T) at ambient temperatures using one‐ and two‐dimensional (1D and 2D) proton and carbon‐13 techniques for assignments. Slow exchange limit (SEL) spectra were observed, demonstrating slow rotations on the NMR timescales, for the unsubstituted bridgehead phenyl groups [C(sp3)–C(aryl sp2) bond rotations] and for the 2,6‐dialkylphenyl groups [N(sp2)–C(aryl sp2) bond rotations]. Substantial magnetic anisotropic shifts were seen in the adducts. For example, in the N‐(2,6‐dialkylphenyl) moieties of the adducts, one of the alkyl groups is directed “into” the adduct cavity, toward the phenanthrenoid portion, and these “inner” alkyl proton NMR signals were shifted upfield. Thus, in CDCl3, the “inner” methyl of adduct 3a exhibits a proton resonance at ?0.13 ppm, upfield of tetramethylsilane (TMS); the “inner” ethyl group signals from 3b appear at 0.026 ppm (CH2, quartet), and ?0.21 ppm (CH3, triplet); and the “inner” isopropyl group from 3c is seen at ?0.06 ppm (methine, approx. septet) and ?0.39 ppm (CH3, doublet). Proton NMR of the crude N‐(2,6‐dialkylphenyl)maleamic acids (used as precursors of the maleimides, 2a–c) exhibited two sets of AB quartet signals, suggesting possible conformers from hindered rotation in the amide groups about the HN–C?O bonds. 相似文献
87.
Gary S. Linz M. J. Musmar Alfred J. Weinheimer Gary E. Martin James A. Matson 《光谱学快报》2013,46(5):545-557
During an investigation of the diterpene constituents of Briareum asbestinum we isolated the previously reported brianthein-X. Through the use of two-dimensional heteronuclear chemical shift correlation and relayed coherence transfer, four of the previously reported 13C-resonance assignments are revised. 相似文献
88.
NaLi分子的完全振动能谱和离解能的研究 总被引:3,自引:1,他引:2
文章使用作者建立的基于微扰理论的代数方法(AM),首次研究了碱金属异核双原子分子NaLi的 、 、 三个电子态的振动光谱常数和振动能谱;使用基于AM的代数能量方法(AEM)研究了这些电子态的离解能。结果表明:根据少数精确的实验振动能级[ ],用AM方法获得了精确的分子振动光谱常数集合,还首次获得了包含所有高振动量子态能级的正确的完全振动能谱{ };用AEM方法获得的分子离解能比由文献发表的振动光谱常数计算得到的离解能值更准确。 相似文献
89.
A new through-bond carbon-proton correlation technique, the MAS-J-HSQC experiment, is described for solid-state NMR. This new pulse scheme is compared experimentally with the previously proposed MAS-J-HMQC experiment in terms of proton resolution on a model sample of powdered L-alanine. We show that for natural abundance compounds, the MAS-J-HMQC and MAS-J-HSQC experiments give about the same proton resolution, whereas, for (13)C-labeled materials, narrower proton linewidths are obtained with the MAS-J-HSQC experiment. In addition we show that in scalar as well as in dipolar heteronuclear shift correlation experiments, when the proton chemical shift is encoded by the evolution of a single-quantum coherence, the proton resolution can be enhanced by simply adding a 180 degrees carbon pulse in the middle of the t(1) evolution time. 相似文献
90.
Fehér K Berger S Kövér KE 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,163(2):340-346
We report a G-BIRD(r) modified coupled HSQC experiment for the accurate determination of one-bond heteronuclear residual dipolar couplings. The G-BIRD(r) module has been employed to refocus the long-range coupling evolution of the heteronucleus during the t1 frequency labeling period. As a result, the crosspeaks obtained are split by only the direct one-bond coupling that can be extracted by measuring simple frequency differences between singlet maxima. Additionally the decoupling of long-range multiple bond splittings leads to considerable sensitivity enhancement. The modification also has been applied in a TROSY sequence resulting in a significant sensitivity and resolution improvement. 相似文献