Nuclear magnetic resonance study of the ferroelastic phase transition of order-disorder type in [N(C2H5)4]2CdCl4

This study uses nuclear magnetic resonance (NMR) techniques to examine the detailed changes in [N(C₂H₅)₄]₂CdCl₄ around its phase transition at the temperature T_C = 284 K. The chemical shifts and spin-lattice relaxation times in the rotating frame (T_1ρ) were determined from ¹H magic angle spinning (MAS) NMR and ¹³C cross-polarization (CP)/MAS NMR spectra. The two sets of inequivalent ¹H and ¹³C nuclei in CH₃ and CH₂ were distinguished. A ferroelastic phase transition was observed at T_C, without structural symmetry change. The phase transition is mainly attributed to the orientational ordering of the [N(C₂H₅)₄]⁺ cations, and the spectral splitting at low temperature is associated with different ferroelastic domains.     

Multinuclear magnetic resonance analysis of 2-(trifluoromethyl)-2-oxazoline

(1)H, (19)F, (13)C, (15)N, and (17)O NMR chemical shifts and (1)H-(1)H, (1)H-(19)F, (1)H-(13)C, (19)F-(13)C, and (19)F-(15)N coupling constants are reported for 2-(trifluoromethyl)-2-oxazoline.     

(1)H and (13)C chemical shifts for 2-aryl and 2-N-arylamino benzothiazole derivatives

The (1)H and (13)C NMR resonances for forty-three 2-aryl and 2-N-arylamino benzothiazole derivatives were completely assigned using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC).     

Complexation of selenium to (R)‐Rh2(MTPA)4: thermodynamics and stoichiometry

Variable‐temperature ¹H and ⁷⁷Se NMR data for 3‐phenylselenenyl‐1‐phenyl‐1‐propene (1) in the presence of Rh₂(MTPA)₄ (Rh*) prove that the equilibria are strongly shifted towards the adduct Rh*···1; free selenide molecules cannot be detected as long as uncomplexed rhodium atoms are available. In the case of excess Rh*, both 1 : 2 and 1 : 1 adducts (Rh* vs 1) are formed, and the latter is slightly favoured. With excess selenide, the system strongly favours the complexation of two selenide molecules (1 : 2 adduct), i.e. one at each rhodium atom. In this situation, intermolecular selenide exchange can be monitored by variable‐temperature ¹H NMR spectroscopy and the energy barrier is estimated to be 54–55 kJ mol^?1. Copyright © 2001 John Wiley & Sons, Ltd.     

(13)C NMR spectral assignment of 1,4-diarylpiperazinones

The piperazinone derivatives have potential application in the pharmaceutical, polymer and textile fields. The present work describes the preparation of a series of new 1,4-diarylsubstituted-2-piperazinones by condensation of substituted N,N'-bis-(2-hydroxyphenyl)-ethylenediamines with glyoxal and the complete (13)C NMR spectral assignment accomplished using APT, HMQC and HMBC techniques. Substituent chemical-shift effects (SCS) were calculated, which showed different values for the lactam- and amine-substituted aromatic rings. The results show that predictions based on SCS effects are not simple for these molecules due to electronic and steric effects. Moreover, in the case of the ortho-substituted derivative 2 g, the NMR spectra reveal a dynamic behavior related to restricted rotation of the phenyl groups (atropisomerism).     

Complete assignment of (1)H and (13)C NMR data of dihydroxyflavone derivatives

Six flavone derivatives were studied. Previously reported NMR data of three of these derivatives were corrected and the NMR data for the other three derivatives not studied previously were completely assigned on the basis of the basic 1D and 2D NMR experiments and molecular modeling.     

碘掺杂的3-乙基-5-[2-(3-乙基-2苯并噻唑啉基)亚乙基]罗丹宁的结构与电性能

标题化合物是一种商品名为Agfa-10的份菁染料,是一种光导性能较好的有机光导体。我们已对它的蒸发膜、溶液膜、单晶的培养与结构,晶型的转变及其电子性能进行了系统地研究与报导.它具有如下的分子结构:     

Stereochemical analysis of N-cyclohexylidene-N-(1-phenylethyl)amine derivatives

The configurational properties of a series of cyclohexylidene imines are discussed on the basis of their 1H, 13C and 15N NMR spectral data.     

Complete 1H and 13C assignments of 8-C-beta-D-[2-O-(E)-p-coumaroyl]glucopyranosyl-2-(2-hydroxy)propyl-7-methoxy-5-methylchromone

1H and 13C NMR spectra of 8-C-beta-D-[2-O-(E)-p-coumaroyl] glucopyranosyl-2-(2-hydroxy)propyl-7-methoxy-5-methylchromone were completely assigned by 2D NMR observations. Especially the 1H assignments of the glucosyl and hydroxyl protons were achieved by utilizing HMQC, HMBC, 1H-1H COSY and DEPT techniques together with a heavy water exchange 1H NMR experiment.     

Strukturen und intramolekulare Bewegungen spezieller polycyclischer Germanium(II)-amide

Structures and Intramolecular Motions of Special Polycyclic Germanium(II) Amides Compounds of the general formula MeSi(NtBu)₃Ge₂X (X = Cl ( 1 ), N(SiMe₃)₂ ( 2 ), P(C₆H₅)₂ ( 3 )) have been synthesized and characterized by X-ray structure analyses and multinuclear NMR-spectroscopy. The temperature dependent NMR investigations of 2 in solution show bond fluctuations concerning the metal-nitrogen bonds and ElMe₃ (El = C, Si) rotations. Some of these intramolecular motions also occur in the solid state as detected by means of temperature dependent ¹³C CP/MAS NMR spectroscopy. The special nature of these NMR spectroscopically detected movements in solution are compared with the results of the X-ray structure analyses. A model of the dynamical behaviour of 2 in solution suggests a quasi circular movement of the two germanium atoms within the molecular cage. After the phase transition from solution to the solid state at ambient temperature this special metal fluctuation is stopped. In the solid state the rotations of the SiMe₃ groups in 2 are only hindered at low temperatures.     

CP/MAS ~(13)C NMR技术对木浆纤维微观结构的研究

利用交叉极化结合魔角旋转技术~(13)C核磁共振法(CP/MAS ~(13)C NMR)对桉木浆纤维的微观结构进行研究,为进一步研究木质纤维素材料开发过程中反应障碍特征奠定基础.通过对NMR光谱C1区(δ 102～108)进行洛仑兹拟合,得到桉木浆纤维中纤维素Iα的相对含量为26.92%,纤维素Iβ的相对含量为52.04%,主要以纤维素Iβ晶体形式为主.通过计算纤维素C4结晶区(δ 86～92)和非结晶区(δ 80～86)的相对含量得到桉木浆的纤维素结晶度为47%.通过洛仑兹和高斯函数的混合模型对NMR光谱C4区(δ 80～92)进行拟合得到基原纤尺寸和微原纤横向尺寸分别为4.0与17.9 nm,并通过计算不同形态的结晶纤维素的相对含量得到纤维素结晶度为51%,证实了在微原纤内部次晶纤维素的存在.     

1H and 13C spectral assignment of 2(1H)-pyridone derivatives

1H and 13C NMR spectroscopic data for 4-aryl-3,4-dihydro-6-methyl-2(1H)pyridone derivatives were fully assigned by a combination of one- and two- dimensional experiments (DEPT, HMBC, HMQC, COSY, NOE).     

(1)H and (13)C NMR spectral data for a tricyclic derivative of a Diels-Alder adduct

A complete NMR analysis with full assignment for (1)H and (13)C NMR spectral data for 5-(acetyloxy)-3-hydroxy-9,10-dimethoxy-6-oxo-11-oxatricyclo[6.2.1.0(2,7)]undec-2-yl acetate is described. This compound was prepared by rapid hydrogenation of the unstable Diels-Alder adduct obtained from the reaction between 3,4-dimethoxyfuran and 2,5-diacetoxy-1,4-benzoquinone. Full homonuclear hydrogen coupling constants measurements and molecular mechanics calculations were performed for the determination of the relative stereochemistry.     

N(nPr)4[B5O6(OH)4][B(OH)3]2 and N(nBu)4[B5O6(OH)4][B(OH)3]2: Clathrates with a diamondoid arrangement of hydrogen-bonded pentaborate anions

Single-crystal X-ray structure analyses of N(nPr)₄[B₅O₆(OH)₄][B(OH)₃]₂,1, and N(nBu)₄ [B₅O₆(OH)₄][B(OH)₃]₂,2, reveal that these materials are novel clathrates, the isotypic host structures of which are three-dimensional assemblies of hydrogen-bonded [B₅O₆(OH)₄]^– ionsand B(OH)₃ molecules. The assembly of only the pentaborate anions is a distorted (i.e., along [102] elongated) fourconnected diamond-related network. The N(nPr) ₄ ⁺ and N(nBu) ₄ ⁺ ions are trapped within the complex three-dimensional channel systems of the host frameworks. Both1 and2 crystallize monoclinically with space groupP2₁/c andZ=4. The cell constants are:1:a=13.592(5),b=12.082(2),c=17.355(6) Å, =106.60(2)° (298K);2:a=13.874(3),b=12.585(1),c=17.588(4) Å, =107.04(1)° (238 K). The results obtained by both¹¹B and¹³C MAS NMR spectroscopy are discussed. Thermogravimetric studies under a flowing inert-gas atmosphere suggest that water, stemming from polycondensation of the hydrous borate species, is released from the clathrates at ca. 443 K (1) and 398 K (2) before the decomposition of the organic cations starts at ca. 603 K (1) and 603 K (2).Author for correspondence. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82172 (82 pages).     

^29Si（^27Al）MAS NMR考察镧离子在LaDAlY型沸石中的作用

用~(29)Si(~(27)Al)MAS NMR和辅加乙酰丙酮(acac)处理样品的静态~(27)Al NMR研究了镧离子对脱铝Y型沸石(DAIY)骨架硅、铝和非骨架铝(EFAL)的影响.结果表明,~(29)Si MAS谱的化学位移及其形状不仅取决于连接[SiO_4]四面体的[AlO]-四面体数目,而且还与引入镧离子的量有关.镧离子的引入导致~(27)Al MAS谱的明显宽化和不对称形变.另外,还讨论了镧离子对非骨架铝的影响.     

A 1H, 13C and 15N NMR study in solution and in the solid state of six N-substituted pyrazoles and indazoles

Three N-substituted pyrazoles and three N-substituted indazoles [1-(4-nitrophenyl)-3,5-dimethylpyrazole (1), 1-(2,4-dinitrophenyl)-3,5-dimethylpyrazole (2), 1-tosyl-pyrazole (3), 1-p-chlorobenzoylindazole (4), 1-tosylinda-zole (5) and 2-(2-hydroxy-2-phenylethyl)-indazole (6)] have been studied by NMR spectroscopy in solution (1H, 13C, 15N) and in the solid state (13C, 15N). The chemical shifts have been compared with GIAO/DFT calculated absolute shieldings. Some discrepancies have been analyzed.