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Magnetic Resonance in Chemistry: MRC

Reika Masuda, Abhishek Gupta, Tim Stait-Gardner, Gang Zheng, Allan Torres, William S Price
No abstract text is available yet for this article.
May 19, 2018: Magnetic Resonance in Chemistry: MRC
Yury Yu Rusakov, Irina L Rusakova, Leonid B Krivdin
Four-component DFT calculations of 31 P NMR chemical shifts have been performed for the representative series of 56 phosphine chalcogenides in order to investigate an influence of different functional groups on the heavy atom relativistic effect on the NMR chemical shifts of light phosphorous atoms (HALA effect). The validity of the four-component DFT approach used for the wide-scale calculations of the phosphorous chemical shifts in a wide series of phosphine chalcogenides has been confirmed on a small series of 5 representative compounds with the aid of high-quality CCSD calculations taking into account solvent, vibrational and the relativistic corrections in comparison with the experiment...
May 18, 2018: Magnetic Resonance in Chemistry: MRC
Dóra Bogdán, Rainer Haessner, Máté Vágvölgyi, Daniele Passarella, Attila Hunyadi, Tamás Gáti, Gábor Tóth
No abstract text is available yet for this article.
May 18, 2018: Magnetic Resonance in Chemistry: MRC
Yunzhi Zhang, Hui Xu, Leah B Casabianca
The interactions between small molecule drugs or dyes and nanoparticles are important to the use of nanoparticles in medicine. Noncovalent adsorption of dyes on nanoparticle surfaces is also important to the development of nanoparticle dual-use imaging contrast agents. In the present work, solution-state NMR is used to examine the noncovalent interaction between a near-infrared cyanine dye and the surface of polystyrene nanoparticles in solution. Using 1D proton NMR, we can approximate the number of dye molecules that associate with each nanoparticle for different sized nanoparticles...
May 17, 2018: Magnetic Resonance in Chemistry: MRC
Darren H Brouwer, Jared Van Huizen
NMR crystallography - an approach to structure determination that seeks to integrate solid-state NMR spectroscopy, diffraction, and computation methods - has emerged as an effective strategy to determine structures of difficult-to-characterize materials, including zeolites and related network materials. This paper explores how far it is possible to go in determining the structure of a zeolite framework from a minimal amount of input information derived only from solid-state NMR spectroscopy. It is shown that the framework structure of the fluoride-containing and tetramethylammonium-templated octadecasil clathrasil material can be solved from the 1D 29 Si NMR spectrum and a single 2D 29 Si NMR correlation spectrum alone, without the space group and unit cell parameters normally obtained from diffraction data...
May 10, 2018: Magnetic Resonance in Chemistry: MRC
Carlos Cobas
The Whittaker Smoother (WS), a special case of Penalized Least Square, is a multipurpose algorithm that has proven to be very useful in many scientific fields, including image processing, chromatography and optical spectroscopy. It shares many similarities with the Savitzky-Golay algorithm, but it is significantly faster and easier to automate. Its use in NMR, however, is not widespread although several applications have recently been published. In this review, the mathematical background of the method and its main applications in NMR spectroscopy will be discussed...
May 2, 2018: Magnetic Resonance in Chemistry: MRC
Jun Uzawa, Junpei Shimabukuro, Tatsuya Suzuki, Akihiro Imamura, Hideharu Ishida, Hiromune Ando, Yoshiki Yamaguchi
Seleno-carbohydrates are those in which the oxygen of the glycosidic bond or the hydroxyl group is artificially replaced with selenium. This substitution changes 1 H and 13 C chemical shifts and produces spin coupling constants involving 77 Se. Coupling constants, such as 2-3 J(77 Se, 1 H), are likely to be useful for conformational analyses of glycans since such couplings are never observed in natural glycans. Several papers have discussed the relationship between 2-3 J(77 Se, 1 H) and conformation, however only few reports describe 1-3 J(77 Se, 13 C), which could also be useful...
April 25, 2018: Magnetic Resonance in Chemistry: MRC
Stefan Benders, Florian Strassl, Bastian Fenger, Bernhard Blümich, Sonja Herres-Pawlis, Markus Küppers
Reactions of gases with liquids play a crucial role in the production of many bulk chemicals. Often, the gas is bubbled into the chosen reactor. Most of the processes at the gas-liquid interface of the bubbles and in their tails are not fully understood and warrant further investigation. For this purpose, NMR imaging or Magnetic Resonance Imaging (MRI) has been applied to visualize some of the processes in the bubble tail. To generate sufficient contrast, a magnetogenic gas-liquid reaction associated with a change of magnetic state, from dia- to paramagnetic, was employed...
April 23, 2018: Magnetic Resonance in Chemistry: MRC
Álvaro Lorente-Macías, Manuel Benítez-Quesada, Ignacio J Molina, Asier Unciti-Broceta, Juan José Díaz-Mochón, María José Pineda de Las Infantas Villatoro
No abstract text is available yet for this article.
April 20, 2018: Magnetic Resonance in Chemistry: MRC
Charles L Perrin
The NMR intensity pattern of a nucleus split by N identical nuclei of spin 1/2 is given by the binomial coefficients. These are conveniently obtained from Pascal's Triangle, equivalent to the chemist's branching diagram. Much less well known is the pattern from splitting by N identical nuclei of spin I > 1/2. This was originally presented in terms of multinomial coefficients, but polynomial coefficients are more convenient. These describe the number of ways that N objects can be distributed to 2I+1 numbered boxes...
April 20, 2018: Magnetic Resonance in Chemistry: MRC
Faith J Scott, Erika L Sesti, Eric J Choi, Alexander J Laut, Jagadishwar R Sirigiri, Alexander B Barnes
We introduce a novel design for millimeter wave electromagnetic structures within magic angle spinning (MAS) rotors. In this demonstration, a copper coating is vacuum deposited onto the outside surface of a sapphire rotor at a thickness of 50 nanometers. This thickness is sufficient to reflect 197 GHz microwaves, yet not too thick as to interfere with radiofrequency fields at 300 MHz or prevent sample spinning due to eddy currents. Electromagnetic simulations of an idealized rotor geometry show a microwave quality factor of 148...
April 19, 2018: Magnetic Resonance in Chemistry: MRC
Fátima M P de Rezende, Matheus P Freitas, Teodorico C Ramalho
Earlier studies with 2-bromocyclohexanone demonstrated a measurable long-range coupling constant (4 JH2,H6 ) for the equatorial conformer, while 4 JH2,H4 and 4 JH4,H6 were not observed; as a consequence, it is inferred that the carbonyl group plays an important role particularly due to hyperconjugative interactions σC2H2 →π*C=O and σC6H6 →π*C=O. In the present study, NBO analysis and coupling constant calculations were performed to cyclohexanone and cyclohexanethione alpha substituted with F, Cl and Br, aiming to evaluate the halogen effect and acceptor character of the π* orbital on the long-range coupling pathway...
April 17, 2018: Magnetic Resonance in Chemistry: MRC
Maria Victoria Silva Elipe, Neil Donovan, Robert Krull, Donald Pooke, Kimberly L Colson
After years towards higher field strength magnets, NMR technology in commercial instruments in the past decade has expanded at low and high magnetic fields to take advantage of new opportunities. At lower field strengths, permanent magnets are well-established, whereas for mid-range and high field, developments utilize superconducting magnets cooled with cryogenic liquids. Recently, the desire to locate NMR spectrometers in non-typical NMR laboratories has created interest in the development of cryogen-free magnets...
April 17, 2018: Magnetic Resonance in Chemistry: MRC
Jean-Nicolas Dumez
No abstract text is available yet for this article.
April 16, 2018: Magnetic Resonance in Chemistry: MRC
Marion Pupier, Jean-Marc Nuzillard, Julien Wist, Nils E Schlörer, Stefan Kuhn, Mate Erdelyi, Christoph Steinbeck, Antony J Williams, Craig Butts, Tim D W Claridge, Bozhana Mikhova, Wolfgang Robien, Hesam Dashti, Hamid R Eghbalnia, Christophe Farès, Christian Adam, Kessler Pavel, Fabrice Moriaud, Mikhail Elyashberg, Dimitris Argyropoulos, Manuel Pérez, Patrick Giraudeau, Roberto R Gil, Paul Trevorrow, Damien Jeannerat
Even though NMR has found countless applications in the field of small molecule characterization, there is no standard file format available for the NMR data relevant to structure characterization of small molecules. A new format is therefore introduced to associate the NMR parameters extracted from 1D and 2D spectra of organic compounds to the proposed chemical structure. These NMR parameters, which we shall call NMReDATA (for nuclear magnetic resonance extracted data), include chemical shift values, signal integrals, intensities, multiplicities, scalar coupling constants, lists of 2D correlations, relaxation times and diffusion rates...
April 14, 2018: Magnetic Resonance in Chemistry: MRC
Chang-Chun Ding, Shao-Yi Wu, Yong-Qiang Xu, Li-Juan Zhang
The local angular distortions Δθ are theoretically studied for the various Ni3+ centers in LiAly Co1-y O2 at different Al concentration y (= 0, 0.1, 0.5 and 0.8) based on the perturbation calculations of electron paramagnetic resonance (EPR) g factors for a trigonally distorted octahedral 3d7 cluster with low spin (S=1/2). Due to the Jahn-Teller effect, the [NiO6 ]9- clusters are found to experience the local angular distortions Δθ (≈ 5 - 9°) along the C3 axis. The variation trend of Δθ with y is in accordance with that of anisotropy Δg (= g// - g⊥ )...
April 12, 2018: Magnetic Resonance in Chemistry: MRC
Hai-Young Kim, Josep Saurí, Ryan D Cohen, Gary E Martin
Recently it has been reported that largen JCC correlations can sometimes be observed in 1,1-ADEQUATE spectra with significant intensity, which opens the possibility of structural misassignment. In this work we have focused on pyrimidine-based compounds, which exhibit multiple bond correlations in the 1,1-ADEQUATE experiment as a consequence of3 JCC coupling constants greater than 10 Hz. Results are supported by both the experimental measurement of3 JCC coupling constants in question using J-modulated-ADEQUATE and density functional theory calculations...
March 30, 2018: Magnetic Resonance in Chemistry: MRC
Guannan Zhang, Christian Hilty
Sensitivity of detection is one of the most limiting aspects when applying NMR spectroscopy to current problems in the molecular sciences. A number of hyperpolarization methods exist for increasing the population difference between nuclear spin Zeeman states, and enhance the signal-to-noise ratio by orders of magnitude. Among these methods, dissolution dynamic nuclear polarization (D-DNP) is unique in its capability of providing high spin polarization for many types of molecules in the liquid state. Originally proposed for biomedical applications including in vivo imaging, applications in high resolution NMR spectroscopy are now emerging...
March 30, 2018: Magnetic Resonance in Chemistry: MRC
Damien Jeannerat
No abstract text is available yet for this article.
March 26, 2018: Magnetic Resonance in Chemistry: MRC
Luc Patiny, Alejandro Bolaños, Andrés M Castillo, Andrés Bernal, Julien Wist
Teaching spectra analysis and structure elucidation requires students to get trained on real problems. This involves solving exercises of increasing complexity and when necessary using computational tools. Although desktop software packages exist for this purpose, platform offers students an online alternative. It provides a set of exercises and tools to help solving them. Only a small number of exercises are currently available, but contributors are invited to submit new ones and suggest new types of problems...
March 26, 2018: Magnetic Resonance in Chemistry: MRC
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