Magnetic Resonance in Chemistry, up to July 2007

Magnetic Resonance in Chemistry
Vol: 45, Issue: 7, July 2007
pp. 532 - 543

Title: NMR spectra, GIAO and charge density calculations of five-membered aromatic heterocycles
Authors: Katritzky, Alan R.a; Akhmedov, Novruz G.a; Doskocz, Jacek; Mohapatra, Prabhu P.a; Hall, C. Dennisa; Güven, Alâattinb
Affiliations: a. Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611‐7200, USA
b. Department of Chemistry, Faculty of Sciences, Anadolu University, 26470 Eskisehir, Turkey
Keywords: NMR; coupling constants; GIAO; pyrrole; five-membered heterocycles
Abstract (English):

The B3LYP/6-31 + G(d) molecular geometry optimized structures of 17 five-membered heterocycles were employed together with the gauge including atomic orbitals (GIAO) density functional theory (DFT) method at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p) and B3LYP/6-311 + G(2d,p) levels of theory for the calculation of proton and carbon chemicals shifts and coupling constants. The method of geometry optimization for pyrrole (1), N-methylpyrrole (2) and thiophene (7) using the larger 6-311 + + G(d,p) basis sets at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p), B3LYP/6-31 + G(2d,p) and B3LYP/cc-pVTZ levels of theory gave little difference between calculated and experimental values of coupling constants. In general, the 1H and 13C chemical shifts for all compounds are in good agreement with theoretical calculations using the smaller 6-31 basis set. The values of nJHH(n = 3, 4, 5) and rmnJCH(n = 1, 2, 3, 4) were predicted well using the larger 6-31 + G(d,p) and 6-311 + + G(d,p) basis sets and at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p), B3LYP/6-31 + G(2d,2p) levels of theory. The computed atomic charges [Mülliken; Natural Bond Orbital Analysis (NBO); Merz-Kollman (MK); CHELP and CHELPG] for the B3LYP/6-311 + + G(d,p) geometry optimized structures of 1–17 were used to explore correlations with the experimental proton and carbon chemical shifts. Copyright © 2007 John Wiley & Sons, Ltd.
Publisher: John Wiley & Sons, Ltd.
Language of Publication: English
# 1097-458X(200707)45:7<532::aid-mrc1967>3.0.CO;2-C
# http://www.interscience.wiley.com/jpages/0749-1581/suppmat/

Magnetic Resonance in Chemistry
Vol: 45, Issue: 7, July 2007
pp. 547 - 556

Title: Solid-state 17O NMR study of the electric-field-gradient and chemical shielding tensors in polycrystalline amino acids
Authors: Yamada, Kazuhikoa; Shimizu, Tadashib; Tansho, Masatakab; Nemoto, Takahiroc; Asanuma, Miwakoa; Yoshida, Mitsurud; Yamazaki, Toshioa; Hirota, Hiroshia
Affiliations: a. RIKEN Genomic Sciences Center, 1‐7‐22 Suehiro, Tsurumi, Yokohama, 230‐0045 Japan
b. Tsukuba Magnet Laboratory, National Institute for Materials Science, 3‐13 Sakura, Tsukuba, 305‐003 Japan
c. Analytical R&D team NM&sol;ER Group, Analytical Instrument Division, JEOL Ltd, 3‐1‐2 Musashino Akishima, Tokyo, 189‐8558 Japan
d. Analytical Science Division, National Food Research Institute, 2‐1‐12 Kannondai, Tsukuba, 305‐8642 Japan
Keywords: NMR; 17O; electric-field-gradient tensor; chemical shielding tensor; amino acids; hydrogen bond; MQMAS
Abstract (English):

We have presented a systematic experimental investigation of carboxyl oxygen electric-field-gradient (EFG) and chemical shielding (CS) tensors in crystalline amino acids. Three 17O-enriched amino acids were prepared: L-aspartic acid, L-threonine, and L-tyrosine. Analysis of two-dimensional 17O multiple-quantum magic-angle spinning (MQMAS), MAS, and stationary NMR spectra yields the 17O CS, EFG tensors and the relative orientations between the two tensors for the amino acids. The values of quadrupolar coupling constants (CQ) are found to be in the range of 6.70–7.60 MHz. The values of diso lie in the range of 268–292 ppm, while those of the d11 and d22 components vary from 428 to 502 ppm, and from 303 to 338 ppm, respectively. There is a significant correlation between the magnitudes of d22 components and C—O bond lengths. Since C—O bond length may be related to hydrogen-bonding environments, solid-state 17O NMR has significant potential to provide insights into important aspects of hydrogen bonds in biological systems. Copyright © 2007 John Wiley & Sons, Ltd.
# 10.1002/mrc.2002

Magnetic Resonance in Chemistry
Vol: 45, Issue: 7, July 2007
pp. 595 - 600

Title: Janocchio—a Java applet for viewing 3D structures and calculating NMR couplings and NOEs
Authors: Evans, David A.a; Bodkin, Michael J.a; Baker, S. Richarda; Sharman, Gary J.a
Affiliations: a. Eli Lilly and Company Ltd, Lilly Research Centre, Windlesham, Surrey, GU20 6PH, UK
Keywords: J-coupling; NOE; Java; applet
Abstract (English):

We present a Java applet, based on the open source Jmol program, which allows the calculation of coupling constants and NOEs from a three-dimensional structure. The program has all the viewing features of Jmol, but adds the capability to calculate both H–H and H–C 3-bond couplings constants. In the case of H—H couplings, the Altona equation is used to perform this. The program also calculates NOEs using the full relaxation matrix approach. All these calculations are driven from a simple point and click interface. The program can calculate values for multi-structure files, and can produce input files for the conformational fitting program NAMFIS. Copyright © 2007 John Wiley & Sons, Ltd.
# 10.1002/mrc.2016

Magnetic Resonance in Chemistry
Vol: 45, Issue: 6, June 2007
pp. 488 - 495

Title: Dynamics and conformations of PEO chains chemically bonded on silica: comparison between 1H and 2H NMR
Authors: Tajouri, T.a; Hommel, H.b
Affiliations: a. Université de Tunis ‐ IPEIT ‐ UR 0113/04, 2, rue Jawhar Let Nahrou ‐ Montfleury, 1008 Tunis, Tunisia
b. Laboratoire de Physico‐Chimie des Polymères et des Milieux Dispersés, E.S.P.C.I., U.M.R. 7615 C.N.R.S., 10 rue Vauquelin, 75231 Paris Cedex 05, France
Keywords: NMR; 1H; 2H; poly(ethylene oxide); grafted polymer; interfaces

1H NMR was used to study the motion of monomer units in a layer of poly(ethylene oxide) chains grafted on silica. First, the dependence of the relaxation times on the grafting ratios is discussed qualitatively from a phenomenological point of view. Next, the NMR line narrowing effect by high-speed rotation is observed in the same samples with different grafting ratios. The magic angle spinning technique permits determination of two correlation times for each grafting ratio: tc characteristic of an environment with a fast motion and tl characteristic of an environment with a slow motion. In addition, the dynamics of these grafted chains are investigated by deuterium NMR (2H NMR), which is sensitive to the anisotropy of molecular motion. The evolution has been studied for two extreme grafting ratios and each time as a function of temperature. The anisotropy is more marked at low temperatures and for a low grafting ratio. The results are consistent with the 1H NMR relaxation times measured as a function of temperature. Copyright © 2007 John Wiley & Sons, Ltd.
# 10.1002/mrc.1997

Magnetic Resonance in Chemistry
Vol: 45, Issue: 6, June 2007
pp. 488 - 495

Title: Dynamics and conformations of PEO chains chemically bonded on silica: comparison between 1H and 2H NMR
Authors: Tajouri, T.a; Hommel, H.b
Affiliations: a. Université de Tunis ‐ IPEIT ‐ UR 0113/04, 2, rue Jawhar Let Nahrou ‐ Montfleury, 1008 Tunis, Tunisia
b. Laboratoire de Physico‐Chimie des Polymères et des Milieux Dispersés, E.S.P.C.I., U.M.R. 7615 C.N.R.S., 10 rue Vauquelin, 75231 Paris Cedex 05, France
Keywords: NMR; 1H; 2H; poly(ethylene oxide); grafted polymer; interfaces

1H NMR was used to study the motion of monomer units in a layer of poly(ethylene oxide) chains grafted on silica. First, the dependence of the relaxation times on the grafting ratios is discussed qualitatively from a phenomenological point of view. Next, the NMR line narrowing effect by high-speed rotation is observed in the same samples with different grafting ratios. The magic angle spinning technique permits determination of two correlation times for each grafting ratio: tc characteristic of an environment with a fast motion and tl characteristic of an environment with a slow motion. In addition, the dynamics of these grafted chains are investigated by deuterium NMR (2H NMR), which is sensitive to the anisotropy of molecular motion. The evolution has been studied for two extreme grafting ratios and each time as a function of temperature. The anisotropy is more marked at low temperatures and for a low grafting ratio. The results are consistent with the 1H NMR relaxation times measured as a function of temperature. Copyright © 2007 John Wiley & Sons, Ltd.
# 10.1002/mrc.1997

Magnetic Resonance in Chemistry
Vol: 45, Issue: 5, May 2007
pp. 401 - 409

Title: Solid-state 19F MAS NMR study on the conformation and molecular mobility of poly(chlorotrifluoroethylene)
Authors: Tatsuno, Hirotoa; Aimi, Keitaroa; Ando, Shinjia
Affiliations: a. Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Ookayama, Meguro‐ku, Tokyo 152‐8552, Japan
Keywords: NMR; 19F; magic angle spinning; dipolar–filter; T1r–filter; 19F shieldings; poly(chlorotrifluoroethylene); conformation; molecular mobility
Abstract (English):

The temperature dependence of molecular mobility and conformational changes of poly(chlorotrifluoro- ethylene) (PCTFE) have been investigated by solid-state 19F magic angle spinning (MAS) NMR spectroscopy. The pulse techniques of dipolar–filter and T1r–filter allow selective observation of the amorphous and crystalline domains, respectively. The temperature dependence of T1rF revealed that the segmental motion in the amorphous domain becomes vigorous above ca 80 °C, which is well above the glass transition (Tg) temperature (52 °C) and more close to the b-relaxation temperature (95 °C). On the other hand, vigorous molecular motions in the crystalline domain occur above 120 °C, which is much below the melting temperature (212 °C). This indicates that the polymer chains in the PCTFE crystallites are more mobile than those of typical semicrystalline fluoropolymers like poly(vinylidene fluoride) (PVDF), which can be associated with structural imperfections in the crystallites. In addition, the density functional theory (DFT) calculations of 19F magnetic shielding suggest that the high-frequency shifts observed for the crystalline signals above 80 °C can be ascribed to the conformational change around meso diads toward more twisted and/or helical conformations in the main chain. Copyright © 2007 John Wiley & Sons, Ltd.
# 10.1002/mrc.1982