黄酮类化合物^13C核磁共振谱的模式识别分类研究

黄酮类化合物广泛存在于植物的各个部位,根据其结构,主要分为黄酮、黄酮醇、双氢黄酮、异黄酮等。对于大多数植物化学工作者来说,解析一个未知化合物都必须经历先确定骨架类型,后确定基团位置这一过程。而前者则需要对该类型的数据规律有充分的认识,否则,就可能导致错误结果。     

Application of Artificial Neural Networks for Analysis of 13C NMR Spectra of Fucoidans

A new approach for structure determination of native and O-desulfated fucoidans by the analysis of their ¹³C NMR spectra by artificial neural networks (ANNs) is described. Two ANN models were studied: the simple three-layer feed-forward network, which employs supervised learning, and the adaptive resonance theory (ART) network with unsupervised learning. Training sets for the networks were constructed using chemical shifts of synthetic oligofucosides. The results obtained demonstrate that both models worked better in the case of desulfated fucoidans, while the ART-type networks gave better results in sulfated (native) fucoidan structure elucidation.     

The F NMR spectrum of bis-trifluoromethylmercury Hg(CF3)2 in the nematic phase: DAISY — a novel program system for the analysis and simulation of NMR spectra

The ¹⁹F NMR spectrum of bis-trifluoromethylmercury in the nematic phase has been analysed using the DAISY program system. The scalar and the dipolar coupling constants have been obtained.     

C60O2可能异构体的结构,电子光谱和NMR谱的理论研究

用ＩＮＤＯ系列方法研究Ｃ６０Ｏ２可能异构体的结构，两个氧原子分别加在两个六元环相邻边或五六元环相邻边形成环氧结构，为Ｃｓ对称性，得６种可能构型，计算表明，两个氧原子加在同个六元环的六六元环相邻边所形成环氧结构Ｃｓ构型最稳定，环氧处Ｃ－Ｃ键不断开，与实验结果一致，其电子光谱计算结果亦与实验值相吻合，这种Ｃｓ构环氧结构所在六元环上的另一个Ｃ－Ｃ键有大的键序，为高活性位置，因此Ｃ６０Ｏ２可能有较好的化学     

The Kinetic and Mechanistic Evaluation of NMR Spectra. New analytical methods (18)

In addition to the static parameters of the chemical shifts and coupling constants, which serve as a source of knowledge for molecular structure and stereochemistry, an NMR spectrum can frequently furnish dynamic quantities characterizing relaxation and exchange phenomena. The information about nuclear switching processes has proved to be particularly useful in practice for the detection of internal molecular motions and for the estimation or determination of the corresponding energy barriers. A plethora of studies of this nature has in the past been performed on simple proton spectra. Methodological developments of recent years have led to a significant reduction of the effort required for the quantitative dynamic evaluation of NMR spectra arising from complex spin systems or involving other nuclei. In many cases it has, moreover, become possible to extract detailed mechanistic information inaccessible by other means. The practical execution of such analyses will be explained and illustrated by a selected number of applications.     

11B 3Q MAS NMR Study on Glucose-Responsive Micelles Self-assembled from PEG-b-P(AA-co-AAPBA)

Phenylboronic acid (PBA) based glucose-responsive materials have attracted great interests in recent years for developing insulin delivery systems.It is desired to obtain PBA based materials that can response to glucose under physiological pH and understand the mechanism.By using 11B triple-quantum magic-angle spinning nuclear magnetic resonance (11B 3Q MAS NMR) measurements,the glucose-responsive mechanism of micelles self-assembled from poly(ethylene glycol)-b-ploy(acrylic acid-co-acrylamidophenylboronic acid) PEG-b-P(AA-co-AAPBA) is deeply investigated.Different configurations of phenylboronic acid during various steps of glucose-responsive behaviors are clearly analyzed in the 11B 3Q MAS NMR spectra and coordination between carboxyl and PBA is confirmed.By increasing the AA units in PEG-b-P(AA-co-AAPBA),the carboxyl can coordinate with PBA moieties and cause the glucose-responsiveness of micelles even in the weak acid environment.     

(s)-多沙唑嗪的核磁共振理论和实验研究

报道了(s)-多沙唑嗪的1H、13C、DEPT、1H-1H COSY等的NMR波谱数据, 并对1H、13C NMR信号进行了指认. (s)-多沙唑嗪分子中含有9个季碳原子, 其中绝大部分通过常规实验的方法难以指认. 应用量子化学规范不变原子轨道(GIAO)的Becke-3-Lee-Yang-Parr(B3LYP)和Hartree-Fock(HF)方法, 分别在6-21G基组下计算了标题化合物的13C NMR化学位移值. 计算结果表明, 理论计算数据与实验结果吻合较好, 可以帮助对(s)-多沙唑嗪季碳原子NMR位移信号进行指认.     

Combined Analysis of NMR and MS Spectra (CANMS)

Cellular metabolism in mammalian cells represents a challenge for analytical chemistry in the context of current biomedical research. Mass spectrometry and NMR spectroscopy together with computational tools have been used to study metabolism in cells. Compartmentalization of metabolism complicates the interpretation of stable isotope patterns in mammalian cells owing to the superimposition of different pathways contributing to the same pool of analytes. This indicates a need for a model‐free approach to interpret such data. Mass spectrometry and NMR spectroscopy provide complementary analytical information on metabolites. Herein an approach that simulates ¹³C multiplets in NMR spectra and utilizes mass increments to obtain long‐range information is presented. The combined information is then utilized to derive isotopomer distributions. This is a first rigorous analytical and computational approach for a model‐free analysis of metabolic data applicable to mammalian cells.     

配合物Zn(II)-BPHA的^1H NMR谱

测定了各pD值下BPHA[BPHA是N,N'-bis(2-aminoethyl)-1,3-propanediaminehexaaceticacid的简称,中文名称为二胺乙基丙二胺六乙酸]和Zn^2^+-BPHA的^1HNMR谱。BPHA两端羧甲基上亚甲基质子的化学位移δ~a和中间羧甲基上亚甲基质子的化学位移δ~b随pD值交替变化。Zn^2^+-BPHA的^1HNMR谱有3种情况:pD<6,对应Zn(II)-H~2BPHA^4^-,有一特征尖峰,显示自由-NH^+(CH~2COO^-)~2残基存在;pD=6-9,对应Zn(II)-HBPHA^5^-,该峰消失,显示4个胺基全部配位;pD>9,对应Zn(II)-BPHA^6^-,该峰再次出现,1个N(CH~2COO^-)~2脱离配位体系。在3种形态的配合物中,Zn-N键都是非活性的,Zn-O键在后两种形态配合物中是非活性的。     

Magic angle carbon-13 NMR study of solid poly(ethylene naphthalene-2,6-dicarboxylate)

Amorphous (1) and semicrystalline (2) samples of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) have been investigated by cross-polarization/magic angle spinning (CP/MAS) ¹³C NMR at 26°C (1 and 2), 100°C (1) and 120°C (2) in order to study the phase structure and the local motion of polymer chain segments at temperatures below and close to T_g (120°C). The lineshape of the ethylene unit ¹³C signal in sample 2 is consistent with the presence of two components which were assigned to trans and gauche conformations. The first component arises mainly from the crystalline regions and the second one from the amorphous part. Cross-polarization curves were traced by changing the contact time between carbon and proton reservoirs. T_CH (cross relaxation time) and proton T_1p (spin-lattice relaxation time in the rotating frame) values were obtained as best fit parameters by fitting calculated curves to the experimental data. All ¹³C NMR data are consistent with the presence of highly rigid ethylene units in both semicrystalline and amorphous samples within the temperature range (T) investigated. This result is in disagreement with the ¹H NMR wide line spectra which showed a noticeable narrowing of the linewidth with increasing temperature in the same range, hence indicating a great mobility of the chain segments. To account for this discrepancy a qualitative model based on the existence of two distinct dynamic regions, one where motion is highly restricted and the other one where large reorientations of ethylene group torsional angles take place, is suggested. The NMR results led to the conclusion that three structural phases are present in PEN: crystalline, very rigid amorphous, and very mobile amorphous. © 1995 John Wiley & Sons, Inc.     

47, 49Ti NMR spectra of half-sandwich titanium(IV) complexes

The 47, 49Ti chemical shifts, resonance line half-widths (Deltanu1/2) and energies of the first electronic charge-transfer transitions (lambdamax1.CT) of Cp'TiX3, where Cp' = eta5-C5H5 (Cp), eta5-C5H4Me (MeCp), eta5-C5HMe4 (Me4Cp), eta5-C5Me5 (Me5Cp), eta5-C5H4SiMe3 (SiCp), eta5-C5H4SnMe3 (SnCp) and eta5-C5H4SiMe2Cl (Si'Cp) and X = Cl, Br, I and OBut, half-sandwich complexes are reported. For the compounds studied, a direct linear relationship between delta(49Ti) and lambdamax1.CT was found.     

[Co(amp)2Cl2]2[ZnCl4]体系中两对称异构体的2D NMR研究

The two symmetrical isomers in [Co(amp)₂Cl₂]₂[ZnCl₄](amp=2-(Aminomethyl)pyridine) system were syn-thesized by general oxidation method and were separated by chromatography and recrystallization method. Their configurations were assigned by using 2D NMR techniques, particularly the NOESY NMR spectra. Solvent used was Me₂SO-d₆ with the central peak of the CD₃ septet as the reference ( ₁₃C,δ 39.37; ₁H,δ 2.49 relative to SiMe₄). Cation exchange media used was Dowex 50Wx 2(H⁺ form, 200～400mesh; Biorad).     

Investigation of Spectra（NMR,Mass）of Some Fe3S3Cluster Compounds

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NMR Crystallography of an Oxovanadium(V) Complex by an Approach Combining Multinuclear Magic Angle Spinning NMR,DFT, and Spin Dynamics Simulations

Bioinorganic vanadium(V) solids are often challenging for structural analysis. Here, we explore an NMR crystallography approach involving multinuclear ¹³C/⁵¹V solid‐state NMR spectroscopy, density functional theory (DFT), and spin dynamics numerical simulations, for the spectral assignment and the 3D structural analysis of an isotopically unmodified oxovanadium(V) complex, containing 17 crystallographically inequivalent ¹³C sites. In particular, we report the first NMR determination of C–V distances. So far, the NMR observation of ¹³C–⁵¹V proximities has been precluded by the specification of commercial NMR probes, which cannot be tuned simultaneously to the close Larmor frequencies of these isotopes (100.6 and 105.2 MHz for ¹³C and ⁵¹V, respectively, at 9.4 T). By combining DFT calculations and ¹³C–⁵¹V NMR experiments, we propose a complete assignment of the ¹³C spectrum of this oxovanadium(V) complex. Furthermore, we show how ¹³C–⁵¹V distances can be quantitatively estimated.     

meso和dl 2,3-二氰基-2,3-二(p-取代苯基)丁二酸二乙酯的~1H NMR研究

测定了meso和dl 2,3-二氰基-2,3-二(p-X苯基)丁二酸二乙酯(X=OCH_3,CH_3,H,Cl,NO_2)的~1H NMR谱及X为CH_3相应二乙酯的~1H Noesy谱。在meso和dl异构体中,苯环m-~1H的化学位移与p-X的Hammett基团常数σ呈线性关系,c~1H的化学位移仅受分子构型的影响,;△δdl-meso为负值,乙氧基中CH_2和CH_3的质子化学位移也只受分子构型的影响,△δdl-meso均为正值。     

Intermolecular stacking of a tetranuclear cyclic Pt(II) complex: NMR characterization and X-ray crystal structure of cis-trans-cis-trans tetra[μ-2,6-diethynyl-4-nitroaniline-bis(tri(p-tolyl)phosphine)platinum(II)]

The synthesis and characterization of a tetranuclear Pt complex, cis-trans-cis-trans tetra[μ-2,6-diethynyl-4-nitroaniline-bis(tri(p-tolyl)phosphine) platinum(II)], namely [L₂Pt-DENA]₄ with L = tri-p-tolylphosphine, is reported. The complex was obtained by the dehydrohalogenative condensation of 2,6-diethynyl-4-nitroaniline (DENA) with cis-[dichlorobis(tri(p-tolyl)phosphine)platinum(II)]. The single crystal structure determination of [L₂Pt-DENA]₄ indicated the formation of a neutral molecular cycle with four alternating platinum units in cis and trans configurations, all bridged with DENA spacers with the presence of solvent (toluene) crystallization molecules. A twisted tetranuclear cyclic feature was identified. The formation of intermolecular stacks of the tetranuclear complex in solution was assessed by means of nuclear Overhauser enhancement spectroscopy (NOESY) and rotating frame Overhauser effect spectroscopy (ROESY) characterizations.     

Molecular Association and Solvent Effects in the Electronic and NMR Spectra of the Tricyanoterpyridineruthenate(II) Complex

Solvent effects on the electronic structure and NMR spectra of the[Ru(terpy)(CN)₃] complex(terpy = 2,2,6,2-terpyridine) have beeninvestigated and interpreted using quantum mechanical semiempirical methods.A systematic splitting of the electronic bands in the visible is observed, in addition to theirbathochromic shifts depending on the acceptor number of the solvent. The solvent-inducedsplittings are rationalized in terms of the involvement of several charge—transfertransitions exhibiting distinct participation of the ruthenium (II), terpy, and CN^–orbitals. Direct evidence of solvent interaction at the cyanide ligands is observedin the [¹³C]NMR spectra. The most enhanced solvent effects are at the middle¹³C-4 and ¹H-4 atoms of terpy, in complete agreement with the theoreticalcalculations. In D₂O, stacking interactions involving the terpy ligands are detectedfrom the [¹H]NMR spectra, leading to a bimolecular association constant of90 mol^–1-dm³. In acetone—D₂O mixed solvents, the spectroscopic changes areindicative of preferential solvation departing from the ideal linear behavior.     

Polymeric Structure and Solid NMR Spectra of Cadmuim ( Ⅱ）Dialkyldithiophosphates(Alkyl=Propyl,Butyl,Isopropyl and Isobutyl)

By dropwise adding thio ligands to concentrated aqueous solutions of Cd(ClO₄)₂·6H₂O, polymeric complexes, Cd(II) O, O'‐dipropyldithiophosphate (1), O, O'‐dibutyl‐dithiophosphate (2), O, O'‐diisopropyl‐dithiophosphate (3) and O, O'‐diisobutyl‐dithiophosphate (4) were obtained. The structure of 4 was determined by X‐ray diffraction analysis, showing that the metal ion sits in distorted tetrahedral sulphur coordination sphere and that the eight‐membered bimetallic rings take the twist chair and boat conformations, alternately. Based on facts that the S(1)—Cd bond length [0.25099(12) nm] is shorter than the other S—Cd bond length [0.25399(12)—0.25701(18) nm] and that the S(1)‐involving angles [113.45(4)°—118.43(5)°] are systematically larger than the normal angles of a tetrahedron, the ligands are hypothesized to be erratically functionalized to Cd(II). To certify the steric nonequivalence of ligands, the compounds were investigated by solid ¹³C, ³¹P and ¹¹³Cd NMR spectroscopy.