Magnetic Resonance in Chemistry

Cover image for Vol. 50 Issue 2

February 2012

Volume 50, Issue 2

Pages 85–177

  1. Research Articles

    1. Top of page
    2. Research Articles
    3. MRC Letters
    1. Studies on crude oil-water biphasic mixtures by low-field NMR (pages 85–88)

      Renzo C. Silva, Giovanna F. Carneiro, Lúcio L. Barbosa, Valdemar Lacerda Jr., Jair C. C. Freitas and Eustáquio V. R. de Castro

      Version of Record online: 15 FEB 2012 | DOI: 10.1002/mrc.2798

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      Analyzing low field NMR data coupled to partial least squares multivariate regression yields good results on phase quantification of crude oil-water biphasic mixtures, not only when the time domain signals differ visually, but also with low errors when the hydrogen relaxation rates of both phases are extremely similar; the worst scenario for water-cut measurements using this technique.

    2. Conformations and intermolecular interactions pattern in solid chloroxylenol and triclosan (API of anti-infective agents and drugs). A 35Cl NQR, 1H-14 N NQDR, X-ray and DFT/QTAIM study (pages 89–105)

      J. N. Latosińska, M. Latosińska, M. A. Tomczak, J. Seliger, V. Žagar and J. K. Maurin

      Version of Record online: 21 FEB 2012 | DOI: 10.1002/mrc.2799

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      Two antibacterial and antifungal agents, chloroxylenol (4-chloro-3,5-dimethyl-phenol) and triclosan (5-chloro-2-(2’,4’-dichlorophenoxy)-phenol), were studied experimentally in solid state with an X-ray, 35Cl-NQR and 17O-NQDR spectroscopies and, theoretically, with the DFT/QTAIM. The scattering of NQR frequencies reproduced by the DFT assuming the X-ray data either at 90 K or RT was found to be a good indicator of the quality of resolution of the crystallographic structure. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but opposite to those adopted when it was bound to different inhibitors. Temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90 K and RT. A single molecule of triclosan resembles an asymmetric unit consisting of two inequivalent molecules of chloroxylenol linked with O-H…O bond.

    3. Density functional theory study of 13C NMR chemical shift of chlorinated compounds (pages 106–113)

      Songqing Li, Wenfeng Zhou, Haixiang Gao and Zhiqiang Zhou

      Version of Record online: 21 FEB 2012 | DOI: 10.1002/mrc.2837

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      The WC04 functional is shown to be capable of reducing the overestimation of the chemical shift of Cl-bonded carbons in standard DFT functionals and to show a good performance in the prediction of 13C NMR chemical shifts of chlorinated organic compounds. The gas-phase GIAO/WC04/6-311+G(2d,p)//B3LYP/6-31+G(d,p) was found to be specifically suitable for the prediction of 13C NMR chemical shifts of chlorides in both chlorinated and non-chlorinated carbons.

    4. Self-diffusion in a hyaluronic acid–albumin–water system as studied by NMR (pages 114–119)

      Andrey Filippov, Marina Artamonova, Maya Rudakova, Roustam Gimatdinov and Vladimir Skirda

      Version of Record online: 15 FEB 2012 | DOI: 10.1002/mrc.2853

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      In the presence of even a small amount of hyaluronic acid, the self-diffusion coefficient of albumin decreases. Three hypotheses were proposed and analyzed. The most likely one is that BSA and HA molecules form complex. The state of the BSA molecules in the BSA-HA-D2O system corresponds to a ‘fast exchange’ condition from the NMR point of view: BSA molecules reside in the ‘free’ and ‘bound’ states for much shorter time than the diffusion time of the PFG NMR experiment.

    5. The effects of intramolecular and intermolecular coordination on 31P nuclear shielding: phosphorylated azoles (pages 120–127)

      Kirill A. Chernyshev, Ludmila I. Larina, Elena A. Chirkina and Leonid B. Krivdin

      Version of Record online: 14 FEB 2012 | DOI: 10.1002/mrc.2854

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      The effects of intramolecular and intermolecular coordination on 31P nuclear shielding have been investigated in the series of tetracoordinated, pentacoordinated and hexacoordinated N-vinylpyrazoles and intermolecular complexes of N-vinylimidazole and 1-allyl-3,5-dimethylpyrazole with phosphorous pentachloride both experimentally and theoretically. It was shown that either intramolecular or intermolecular coordination involving phosphorous results in a dramatic 31P nuclear shielding amounting to approximately 150 ppm on changing the phosphorous coordination number by one. A major importance of solvent effects on 31P nuclear shielding of intramolecular and intermolecular complexes involving N[RIGHTWARDS ARROW]P coordination bond has been demonstrated. It was found that the zeroth-order regular approximation-gauge-including atomic orbital-B1PW91/DZP method was sufficiently accurate for the calculation of 31P NMR chemical shifts, provided relativistic corrections are taken into account, the latter being of crucial importance in the description of 31P nuclear shielding.

    6. The effect of solvent accessible surface on Hammett-type dependencies of infinite dilution 29Si and 13C NMR shifts in ring substituted silylated phenols dissolved in chloroform and acetone (pages 128–134)

      Vratislav Blechta, Stanislav Šabata, Jan Sýkora, Jiří Hetflejš, Ludmila Soukupová and Jan Schraml

      Version of Record online: 15 FEB 2012 | DOI: 10.1002/mrc.2860

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      The substituent sensitivity of 29Si chemical shifts in para substituted silylated phenols, 4-R-C6H4-O-SiR′2R″, is reduced by association with chloroform. The decrease in slopes (Δ) in Hammett-type dependencies of 29Si chemical shifts is proportional to the solvent accessible surface of oxygen atom in the Si-O-C link.

    7. Spectra edited by relative signs of homonuclear couplings of low abundance nuclei (pages 135–141)

      Vratislav Blechta, Milan Kurfürst and Jan Schraml

      Version of Record online: 14 FEB 2012 | DOI: 10.1002/mrc.2869

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      New 2D HCSE pulse sequence for detection of signed homonuclear couplings between low abundant nuclei (29Si, 13C, 15N) using the third heteronucleus (usually hydrogen) in linear spin system is presented. Ability to detect two-bond carbon–carbon signed couplings is demonstrated. Signs of 2J(Si-O-Si) couplings with magnitudes from 0.5 to 9.0 Hz on a set of siloxanes were first time measured, and all were found to be positive.

    8. DFT calculations of structures, 13C NMR chemical shifts, and Raman RBM mode of simple models of small-diameter zigzag (4,0) carboxylated single-walled carbon nanotubes (pages 142–151)

      Teobald Kupka, Elżbieta Chełmecka, Karol Pasterny, Michał Stachów and Leszek Stobiński

      Version of Record online: 21 FEB 2012 | DOI: 10.1002/mrc.2874

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      Monocarboxylated acenes, cyclic acenes, and models of zigzag (4,0) single-walled carbon nanotubes were fully optimized at the UB3LYP/6-31G* level of theory. These models were selected to obtain some insight into the changes of nuclear isotropic changes upon systematically changing (increasing) the basic building units of single-walled carbon nanotubes. Selected structural, 13C NMR, and Raman radial breathing mode frequencies were approximated toward the infinity upon the increase of the studied system size using a simple two-parameter mathematical formula. The gauge including atomic orbital NMR-calculated nuclear isotropic shieldings were converted to 13C NMR chemical shifts using benzene as a secondary standard.

    9. Dynamic NMR of low-sensitivity fast-relaxing nuclei: 17O NMR and DFT study of acetoxysilanes (pages 152–158)

      Luca Fusaro, Giulia Mameli, Francesca Mocci, Michel Luhmer and Giovanni Cerioni

      Version of Record online: 28 FEB 2012 | DOI: 10.1002/mrc.3794

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      The present work shows, for the first time, that quantitative kinetic data on organic compounds can be obtained by natural abundance 17O dynamic NMR. This complements the recent progress achieved in 17O NMR and extends the use of DNMR to the characterization of processes that are not amenable to study by 1H or 13C.

    10. Hartmann–Hahn 2D-map to optimize the RAMP–CPMAS NMR experiment for pharmaceutical materials (pages 159–168)

      Kazuko Suzuki, Charlotte Martineau, Gerhard Fink, Stefan Steuernagel and Francis Taulelle

      Version of Record online: 26 FEB 2012 | DOI: 10.1002/mrc.3798

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      A two-dimensional Hartmann–Hahn map is used to highlight the effects of the RF field strength and inhomogeneities on the efficiency of the magnetization transfer in the RAMP–CPMAS NMR experiment.

  2. MRC Letters

    1. Top of page
    2. Research Articles
    3. MRC Letters
    1. Stereochemical behavior of 77Se-1H spin-spin coupling constants in pyrazolyl-1,3-diselenanes and 1,2-diselenolane (pages 169–173)

      Yury Yu. Rusakov, Leonid B. Krivdin, Lyubov K. Papernaya and Alexandra A. Shatrova

      Version of Record online: 26 FEB 2012 | DOI: 10.1002/mrc.2863

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      Conformational study of five derivatives of 2-(pyrazol-4-yl)-1,3-diselenane together with related 1,2-diselenolane in respect to the stereochemical trends of geminal and vicinal 77Se-1H spin-spin coupling constants has been carried out by means of high-level theoretical calculations in combination with experiment.

    2. Halogenated chamigrane sesquiterpenes from Laurencia okamurae (pages 174–177)

      Xiao-Dong Li, Wei Ding, Feng-Ping Miao and Nai-Yun Ji

      Version of Record online: 21 FEB 2012 | DOI: 10.1002/mrc.2870

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      Three new chamigrane sesquiterpenes (1–3) were characterized by one- and two-dimensional NMR from the marine red alga Laurencia okamurae.