共查询到20条相似文献,搜索用时 15 毫秒
1.
Karl E. Schwarzhans 《Angewandte Chemie (International ed. in English)》1970,9(12):946-953
Serviceable NMR spectra can, with a few exceptions[1,6], be recorded for paramagnetic complexes in solution. These spectra provide information about the structure of the complexes and the distribution of the unpaired electrons, and hence also about reactive centers in the molecule. The elucidation of intermolecular and intramolecular exchange phenomena, e.g. the determination of ligand exchange rate constants, the determination of rotation barriers, and the detection of contact complexes in solution, or even of occupation equilibria of the electrons, is possible in this way. It can be seen, therefore, that NMR studies on paramagnetic complexes can be a rich source of information. 相似文献
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Ln(Ⅲ)—Co(Ⅱ)与以水杨醛缩乙二胺Schiff碱异核配合物的合成与波谱性质 总被引:5,自引:0,他引:5
合成了双水杨醛缩乙二胺Schiff碱(SALEN)与钴的配合物Co(SALEN)(NO3)2.3H2O及镧系-钴的异核配合物LnCo(SALEN)2(NO3)5.2H2O(Ln=La,Nd,Sm,Gd,Yb,Y)以紫外红外光谱,特别是HNMR是EPR波谱等方法研究了它们在组成、结构和配位等方面的异同,中讨论了配合物EPR谱在不同溶剂中峰宽的相对关系,配合物在晶体场强度及Gd^3+周围局部对称性等 相似文献
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茶多酚对食用油抗氧化作用的顺磁共振研究 总被引:2,自引:1,他引:2
研究了茶叶中的主要活性成分茶多酚的抗氧化作用及其机理,将不同含量的茶多酚溶液添加到经各种高温处理的食用油中,在实验的各个反应阶段分别取样用顺磁共振波谱仪进行跟踪检测,结果表明:茶多酚具有明显的消除,抑制食用油中的自由基的能力,该能力随着茶多酚加入的浓度,反应时间的变化而不同,实验所获得的茶多酚抑制食用油中自由基的反应时间,浓度,温度的变化规律,为今后在食品工业上科学地利用茶多酚提供了科学依据及实验 相似文献
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Pierre Laszlo 《Angewandte Chemie (International ed. in English)》1978,17(4):254-266
With the availability of Fourier transform spectrometers, 23Na-NMR spectroscopy has become an important tool. It affords direct insight into solvation and ion pairing phenomena, both in organic and in bio-inorganic systems. Monitoring the chemical shifts and linewidths of 23Na signals gives access to binding constants, reorientational correlation times and the microdynamics of the sodium coordination shell. The binding of other cations can also be studied by 23Na-NMR spectroscopy, in competition experiments. 相似文献
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Yunfei Bai Zhen Wang Ning Qin Detian Ma Dr. Wenbin Fu Prof. Dr. Zhouguang Lu Dr. Xiaobo Pan 《Angewandte Chemie (International ed. in English)》2023,62(18):e202303162
Organic materials are promising candidates for future rechargeable batteries, owing to their high natural abundance and rapidly redox reaction. Elaborating the charge/discharge process of organic electrode is critical to unveil the fundamental redox mechanism of lithium-ion batteries (LIBs), but monitoring of this process is still challenging. Here, we report a nondestructive electron paramagnetic resonance (EPR) technique to real-time detect the electron migration step within polyimide cathode. From in situ EPR tests, we vividly observe a classical redox reaction along with two-electron transfer which only shows one pair of peaks in the cyclic voltammetry curve. The radical anion and dianion intermediates are detailed delineation at redox sites in EPR spectra, which can be further confirmed through density functional theory calculations. This approach is especially crucial to elaborate the correlation behind electrochemical and molecular structure for multistep organic-based LIBs. 相似文献
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Imaging of Enzyme Activity by Electron Paramagnetic Resonance: Concept and Experiment Using a Paramagnetic Substrate of Alkaline Phosphatase 下载免费PDF全文
Urikhan Sanzhaeva Xuan Xu Priyaankadevi Guggilapu Prof. Dr. Mark Tseytlin Prof. Dr. Valery V. Khramtsov Prof. Dr. Benoit Driesschaert 《Angewandte Chemie (International ed. in English)》2018,57(36):11701-11705
Enzyme activities are well established biomarkers of many pathologies. Imaging enzyme activity directly in vivo may help to gain insight into the pathogenesis of various diseases but remains extremely challenging. In this communication, we report the use of EPR imaging (EPRI) in combination with a specially designed paramagnetic enzymatic substrate to map alkaline phosphatase activity with a high selectivity, thereby demonstrating the potential of EPRI to map enzyme activity. 相似文献
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Alarich Weiss 《Angewandte Chemie (International ed. in English)》1972,11(7):607-619
Various problems of solid-state chemistry can be solved by spectroscopic investigation of the nuclear magnetic resonance (NMR and NQR methods). This progress report presents a survey of the nature of the interactions in the crystal that underlie such measurements, of the observations in the spectrum, and of the information obtainable from it. The field of application of the methods covers both static and dynamic properties of solids. 相似文献
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Kirsten H. Chalmers Elena De Luca Naomi H. M. Hogg Alan M. Kenwright Dr. Ilya Kuprov Dr. David Parker Prof. Mauro Botta Prof. J. Ian Wilson Dr. Andrew M. Blamire Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):134-148
The synthesis and spectroscopic properties of a series of CF3‐labelled lanthanide(III) complexes (Ln=Gd, Tb, Dy, Ho, Er, Tm) with amide‐substituted ligands based on 1,4,7,10‐tetraazacyclododecane are described. The theoretical contributions of the 19F magnetic relaxation processes in these systems are critically assessed and selected volumetric plots are presented. These plots allow an accurate estimation of the increase in the rates of longitudinal and transverse relaxation as a function of the distance between the LnIII ion and the fluorine nucleus, the applied magnetic field, and the re‐rotational correlation time of the complex, for a given LnIII ion. Selected complexes exhibit pH‐dependent chemical shift behaviour, and a pKa of 7.0 was determined in one example based on the holmium complex of an ortho‐cyano DO3A‐monoamide ligand, which allowed the pH to be assessed by measuring the difference in chemical shift (varying by over 14 ppm) between two 19F resonances. Relaxation analyses of variable‐temperature and variable‐field 19F, 17O and 1H NMR spectroscopy experiments are reported, aided by identification of salient low‐energy conformers by using density functional theory. The study of fluorine relaxation rates, over a field range of 4.7 to 16.5 T allowed precise computation of the distance between the LnIII ion and the CF3 reporter group by using global fitting methods. The sensitivity benefits of using such paramagnetic fluorinated probes in 19F NMR spectroscopic studies are quantified in preliminary spectroscopic and imaging experiments with respect to a diamagnetic yttrium(III) analogue. 相似文献
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根据顺磁物质会引起溶液中质子谱线的位移,位移与磁矩间的关系为μ=aT△νC,其中a为常数,T为热力学温度(K),c为溶液中顺磁物质的浓度,△ν为顺磁物质引起溶液中质子共振线的频率差。采用同轴毛细管的样品管用核磁共振测定顺磁物质的磁矩,并得到一些顺磁物质的磁矩。其测定值与文献值相吻合。 相似文献
11.
Wolfgang von Philipsborn 《Angewandte Chemie (International ed. in English)》1971,10(7):472-490
In double resonance spectra, transitions between energy levels of a nuclear spin system are measured in the presence of two (or more) oscillating magnetic fields. Experiments of this nature form the basis of what is nowadays one of the most important techniques of NMR spectroscopy. Depending on the method selected, they can be used to unravel complex spectra, to measure hidden or weak resonances, or to determine the relative signs of coupling constants, as well as in stereochemical or kinetic studies. This wide and steadily growing range of applications of double resonance is described with the aid of specifilc examples. 相似文献
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Gwendal Kervern Anthony D'Aléo Dr. Loïc Toupet Dr. Olivier Maury Dr. Lyndon Emsley Prof. Guido Pintacuda Dr. 《Angewandte Chemie (International ed. in English)》2009,48(17):3082-3086
Shifts for crystals : Solid‐state NMR spectroscopy can be used for structure determination of microcrystalline paramagnetic solids at natural isotopic abundance. The protocol makes use of paramagnetic effects, measured on suitably recorded 1H NMR spectra, to define the conformation of a molecule in the lattice and the intermolecular packing in the solid phase. The method is illustrated with a family of lanthanide compounds (see picture).
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Xiaoli Tan Kaiyun Ji Xing Wang Ru Yao Guifang Han Frederick A. Villamena Jay L. Zweier Yuguang Song Antal Rockenbauer Yangping Liu 《Angewandte Chemie (International ed. in English)》2020,59(2):928-934
Biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), coexist in biological systems with diverse biological roles. Thus, analytical techniques that can detect, quantify, and distinguish between multiple biothiols are desirable but challenging. Herein, we demonstrate the simultaneous detection and quantitation of multiple biothiols, including up to three different biothiols in a single sample, using electron paramagnetic resonance (EPR) spectroscopy and a trityl‐radical‐based probe (MTST). We term this technique EPR thiol‐trapping. MTST could trap thiols through its methanethiosulfonate group to form the corresponding disulfide conjugate with an EPR spectrum characteristic of the trapped thiol. MTST was used to investigate effects of l ‐buthionine sulfoximine (BSO) and pyrrolidine dithiocarbamate (PDTC) on the efflux of GSH and Cys from HepG2 cells. 相似文献
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Dr. Matthieu Autillo Laetitia Guerin Dr. Thomas Dumas Dr. Mikhail S. Grigoriev Dr. Alexandre M. Fedoseev Sebastiano Cammelli Pier Lorenzo Solari Dr. Dominique Guillaumont Dr. Philippe Guilbaud Dr. Philippe Moisy Dr. Hélène Bolvin Dr. Claude Berthon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(17):4435-4451
The magnetic properties of LnIII and AnIII complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes. Methods using a number of nuclei of the dipicolinate ligands revealed an abrupt change in the geometries of the complexes and a metal–ligand interaction in the middle of the lanthanide series. A study of the variation of the paramagnetic shifts with temperature demonstrated that higher-order terms of the dipolar and contact contributions are required, especially for the lightest LnIII and almost all the studied AnIII. Bleaney's parameters <Sz>a and relating to the contact and dipolar terms, respectively, were deduced from experimental data and compared with the results of ab initio calculations. Quite a good agreement was found for the temperature dependencies of <Sz>a and . However, the values obtained from cation magnetic anisotropy calculations showed some discrepancies with the values derived from Bleaney's equation defined for LnIII. Other parameters, such as the crystal field parameter and the hyperfine constants Fi obtained from the experimental data of the [An(ethyl-dpa)3]3− complexes (ethyl-dpa=4-ethyl-2,6-dipicolinic acid), are at odds with the assumptions underlying Bleaney's theory. 相似文献
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Zhen Wei Yin Yang Qing‐Feng Li Feng Huang Hui‐Hui Zuo Prof. Xun‐Cheng Su 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(18):5758-5764
The site‐specific labeling of proteins with paramagnetic lanthanides offers unique opportunities for NMR spectroscopic analysis in structural biology. Herein, we report an interesting way of obtaining paramagnetic structural restraints by employing noncovalent interaction between a lanthanide metal complex, [Ln(L)3]n? (L=derivative of dipicolinic acid, DPA), and a protein. These complexes formed by lanthanides and DPA derivatives, which have different substitution patterns on the DPA derivatives, produce diverse thermodynamic and paramagnetic properties when interacting with proteins. The binding affinity of [Ln(L)3]n? with proteins, as well as the determined paramagnetic tensor, are tunable by changing the substituents on the ligands. These noncovalent interactions between [Ln(L)3]n? and proteins offer great opportunities in the tagging of proteins with paramagnetic lanthanides. We expect that this method will be useful for obtaining multiple angles and distance restraints of proteins in structural biology. 相似文献
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Shiny Maity Brad D. Price C. Blake Wilson Arnab Mukherjee Matthieu Starck David Parker Maxwell Z. Wilson Janet E. Lovett Songi Han Mark S. Sherwin 《Angewandte Chemie (International ed. in English)》2023,62(13):e202212832
We present time-resolved Gd−Gd electron paramagnetic resonance (TiGGER) at 240 GHz for tracking inter-residue distances during a protein's mechanical cycle in the solution state. TiGGER makes use of Gd-sTPATCN spin labels, whose favorable qualities include a spin-7/2 EPR-active center, short linker, narrow intrinsic linewidth, and virtually no anisotropy at high fields (8.6 T) when compared to nitroxide spin labels. Using TiGGER, we determined that upon light activation, the C-terminus and N-terminus of AsLOV2 separate in less than 1 s and relax back to equilibrium with a time constant of approximately 60 s. TiGGER revealed that the light-activated long-range mechanical motion is slowed in the Q513A variant of AsLOV2 and is correlated to the similarly slowed relaxation of the optically excited chromophore as described in recent literature. TiGGER has the potential to valuably complement existing methods for the study of triggered functional dynamics in proteins. 相似文献
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