Solid-State NMR Literature Blog

Thursday, January 17, 2008

Bryan's Literature Update Through January 17, 2008

Welcome to another exciting Solid-State NMR Literature Blog update! Tell your friends all about the thrills and chills entailed in this wonderful read! It's a real page-turner (or page-scroller, get it?)! LOLZ!

This update contains all the news fit to print in the solid-state NMR (and some general NMR) world from Chem. Phys., Chem. Phys. Lett., Can. J. Chem., Chem. Commun., Dalton Trans., and J. Mater. Chem.. Six journals, six months, all below.

Special feature: Try moving your mouse cursor over the "volume" word in blog updates from Chemical Physics or Chem. Phys. Lett.. If you're at the University of Windsor, you can go right to the journal.

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Chemical Physics

Vol: 337, Issue: 1-3, August 16, 2007

pp. 144-150

Title: A first-principles computational ¹⁷O NMR investigation of metal ion-oxygen interactions in carboxylate oxygens of alkali oxalates

Authors: Wong, A.; Thurgood, G.; Dupree, R.; Smith, M.E.

Keywords: DFT calculations; Metal ion-oxygen interactions; Oxalates; ¹⁷O NMR; Chemical anisotropy shifts; Electrical-field gradients

Abstract (English): ¹⁷O NMR parameters, including chemical shift (CS) and electrical-field gradient (EFG) tensors, are calculated for oxalate compounds containing various different alkali ions using a DFT infinite periodic solid approach. This DFT study allows correlations to be found between the metal ion and oxygen interaction and the ¹⁷O NMR interaction parameters. The ¹⁷O CS shows greater sensitivity to the local alkali ions than that shown by the ¹³C CS in the same compounds. It is found that the combination of metal ion-oxygen bond strength and cation size induce a deshielding shift up to ~70ppm of ¹⁷O d_iso. The results also show the effects of different M-O interactions and C-O bond characteristics on the orientation of ¹⁷O CS tensor components, and suggest that the ¹⁷O quadrupolar parameters are systematically sensitive to the local cation environments around the carboxylate oxygen.

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Title: EFGShield - A program for parsing and summarizing the results of electric field gradient and nuclear magnetic shielding tensor calculations

Authors: Samyuktha Adiga, Dominic Aebi, and David L. Bryce

Abstract: A computer program (EFGShield) is described that simplifies and summarizes the output from electric field gradient (EFG) and nuclear magnetic shielding tensor calculations performed independently using existing quantum chemical software. In addition to summarizing tensor magnitudes according to conventions commonly used by solid-state NMR spectroscopists, the program provides Euler angles relating the orientations of the EFG and shielding tensor principal axis systems (PAS). An atomic coordinate file is generated that also contains dummy atoms representing the orientations of the EFG and shielding tensor PASs in the molecular framework. We demonstrate the functionality of the program using calculations of the chlorine EFG and shielding tensors for strontium chloride dihydrate and calcium chloride dihydrate. Several models of the chloride environment in these compounds are tested, including those where point charges are used to represent the extended three-dimensional lattices within the self-consistent charge field perturbation approach. The results highlight both the shortcomings and successes of traditional localized orbital-based basis sets in the description of the NMR properties of extended systems. We anticipate that EFGShield will be a useful tool for spectroscopists using quantum chemical software to aid in the interpretation of experimental data.

Key words: quantum chemical calculations, computer program, electric field gradient tensor, quadrupolar coupling constant, nuclear magnetic shielding tensor, Euler angles, alkaline earth chloride hydrates.

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Title: High resolution O 1s XPS spectral, NMR, and thermodynamic evidence bearing on anionic silicate moieties (units) in PbO-SiO2 and Na2O-SiO2 glasses

Authors: H. W. Nesbitt and K. N. Dalby

Abstract: Recent technical advances in X-ray photoelectron spectroscopy (XPS) have largely overcome differential charging of insulator surfaces, with the result that O 1s linewidths for silicates can be routinely collected that are 50% to 100% narrower than had been previously obtainable. The bridging and nonbridging oxygen signals of glasses are well resolved and now can be accurately measured by XPS without resorting to ad hoc fitting procedures. All O 1s spectra of silicates collected so far are somewhat asymmetric to the high binding energy side of the peak, a characteristic due primarily to vibrational contributions in the ion state produced by photoemission (electronic excited state). This asymmetry must be considered if the proportion of bridging to nonbridging oxygen ratios are to be accurately determined from the XPS O 1s spectra of silicates. X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) experiments yield similar silicon-bridging oxygen (Si-O-Si) concentrations for PbO-SiO₂ glasses. The data are proof that the reaction, 2PbO + SiO₂ Pb₂SiO₄, does not go to completion (i.e., one or other reactant is not completely consumed). Instead, the data indicate that an equilibrium exists among these constituents, with the equilibrium constant for the reaction being near 15; ergo, some metal bridging oxygen (MBO or Pb-O-Pb), silicon bridging oxygen (BO or Si-O-Si), and nonbridging oxygen (NBO or M-O-Si) are present over the entire range of binary melt compositions. NMR and XPS spectroscopic techniques yield substantially different Si-O-Si concentrations in Na₂O-SiO₂₂O content. XPS experiments indicate higher proportions of Si-O-Si in Na₂O-rich glasses than do the NMR studies. In spite of the different results, three independently collected sets of NMR experiments are similar and yield similar Si-O-Si concentrations. Five XPS experimental studies are likewise self-consistent (but different from the NMR studies). Comparison of data from the two spectroscopic techniques indicates that all experimental spectra are of good or reasonable quality, so that systematic experimental problems or the interpretation (i.e., fitting) of these spectra may be incorrect for one or both types of spectral data. Viscosity, conductivity, and the XPS data are consistent with (but not proof for) formation of an Na₂Si₂O₅ species in the Na₂O-SiO₂ glasses. The most comprehensive NMR study is, by contrast, consistent with the formation of an orthosilicate species (Na₄SiO₄). The NMR and XPS results cannot yet be reconciled and additional experimental studies are required to resolve and to understand better Na₂O-SiO₂ liquids and glasses.

Key words: XPS, high resolution, silicate glass, NMR.

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Chem. Commun., 2007, 2923 - 2925, DOI: 10.1039/b705844f

Title: Responsive fluorinated lanthanide probes for ¹⁹F magnetic resonance spectroscopy

Authors: P. Kanthi Senanayake, Alan M. Kenwright, David Parker and Susanna K. van der Hoorn

Abstract: The introduction of CF₃ reporter groups close to the paramagnetic centre in macrocyclic lanthanide(III) complexes allows faster acquisition of ¹⁹F magnetic resonance data, and amplifies chemical shift non-equivalence, as exemplified by the definition of ratiometric chemical shift probes for pH and, in principle, enzyme activity.

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Chem. Commun., 2007, 3664 - 3666, DOI: 10.1039/b707840d

Title: Sequential C–F activation and borylation of fluoropyridines via intermediate Rh(I) fluoropyridyl complexes: a multinuclear NMR investigation

Authors: Richard J. Lindup, Todd B. Marder, Robin N. Perutz and Adrian C. Whitwood

Abstract: The C–F bond activation of fluoropyridines by [Rh(SiPh₃)(PMe₃)₃] afforded Rh(I) fluoropyridyl complexes of the type [Rh(Ar^F)(PMe₃)₃] with concomitant formation of fluorotriphenylsilane; subsequent treatment with bis-catecholatodiboron yielded fac-[Rh(Bcat)₃(PMe₃)₃] and the free fluoropyridyl boronate esters (Ar^FBcat).

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Dalton Trans., 2007, 3914 - 3923, DOI: 10.1039/b708469b

Title: Sn-centred icosahedral Rh carbonyl clusters: synthesis and structural characterization and ¹³C–{¹⁰³Rh} HMQC NMR studies

Authors: Cristina Femoni, Maria Carmela Iapalucci, Giuliano Longoni, Cristina Tiozzo, Stefano Zacchini, Brian T. Heaton and Jonathan A. Iggo

Abstract: The reaction of [Rh₇(CO)₁₆]^3– with SnCl₂·2H₂O in a 1 : 1 molar ratio under N₂ results in the formation of the new heterometallic cluster, [Rh₁₂Sn(CO)₂₇]^4–, in very high yield (ca. 86%). Further controlled additions of SnCl₂·2H₂O, or solutions of HCl, or [RhCl(COD)]₂, give [Rh₁₂(µ-Cl)₂Sn(CO)₂₃]^4–. Similarly, addition of HBr to [Rh₁₂Sn(CO)₂₇]^4– gives the related cluster [Rh₁₂(µ-Br)₂Sn(CO)₂₃]^4–. Notably, if the addition of SnCl₂·2H₂O to [Rh₁₂Sn(CO)₂₇]^4– is carried out under a CO atmosphere, the reaction takes a different course and leads to the formation of the new cluster, [Rh₁₂Sn(µ₃-RhCl)(CO)₂₇]^4–. All the above clusters have been shown by single-crystal X-ray diffraction studies to have a metal framework based on an icosahedron, which is centred by the unique Sn atom. Their chemical reactivity and ¹³C–{¹⁰³Rh} HMQC NMR spectroscopic characterization are also reported.

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Dalton Trans., 2007, 4523 - 4528, DOI: 10.1039/b709673a

Title: Ionothermal synthesis, crystal structure and solid-state NMR spectroscopy of a new organically templated gallium oxalatophosphate: (H₂TMPD)_0.5[Ga₃(C₂O₄)_0.5(PO₄)₃] (TMPD = N,N,N,N-tetramethyl-1,3-propanediamine)

Authors: Ming-Feng Tang, Yi-Hui Liu, Pai-Ching Chang, Yi-Chen Liao, Hsien-Ming Kao and Kwang-Hwa Lii

Abstract: A new organically templated gallium oxalatophosphate, (C₇H₂₀N₂)_0.5[Ga₃(C₂O₄)_0.5(PO₄)₃], has been synthesized by using a low-melting-point eutectic mixture of choline chloride and oxalic acid as a solvent and characterized by single-crystal X-ray diffraction, thermogravimetric analysis and solid-state NMR spectroscopy. It is the first example of ionothermal synthesis of organically templated metal oxalatophosphate. The structure contains double 6-ring units of the composition Ga₆(PO₄)₆ which are connected by oxalate ligands and P–O–Ga bonds to form a 3-D framework. The charge-compensating organic ammonium cations which are disordered over two positions are located at the intersections of two types of 8-ring channels. ¹H MAS and ¹³C CPMAS NMR studies confirm the presence of N,N,N,N-tetramethyl-1,3-propanediammonium cation. The ⁷¹Ga and ³¹P MAS NMR spectra are also consistent with the crystal structure analysis results.

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Dalton Trans., 2008, 481 - 490, DOI: 10.1039/b712011g

Title: A solid-state NMR investigation of single-source precursors for group 12 metal selenides; M[N(ⁱPr₂PSe)₂]₂ (M = Zn, Cd, Hg)

Authors: Bryan A. Demko and Roderick E. Wasylishen

Abstract: The first solid-state NMR investigation of dichalcogenoimidodiphosphinato complexes, M[N(R₂PE)₂]_n, is presented. The single-source precursors for metal-selenide materials, M[N(ⁱPr₂PSe)₂]₂ (M = Zn, Cd, Hg), were studied by solid-state ³¹P, ⁷⁷Se, ¹¹³Cd, and ¹⁹⁹Hg NMR at 4.7, 7.0, and 11.7 T, representing the only ⁷⁷Se NMR measurements, and in the case of Cd[N(ⁱPr₂PSe)₂]₂¹¹³Cd NMR measurements, to have been performed on these complexes. Residual dipolar coupling between ¹⁴N and ³¹P was observed in solid-state ³¹P NMR spectra at 4.7 and 7.0 T yielding average values of R(³¹P,¹⁴N)_eff = 880 Hz, C_Q(¹⁴N) = 3.0 MHz, ¹J(³¹P,¹⁴N)_iso = 15 Hz, alpha =90°, beta = 26°. The solid-state NMR spectra obtained were used to determine the respective phosphorus, selenium, cadmium, and mercury chemical shift tensors along with the indirect spin–spin coupling constants: 1J(77Se,31P)iso, 1J(111/113Cd,77Se)iso, 1J(199Hg,77Se)iso, and 2J(199Hg,31P)iso. Density functional theory magnetic shielding tensor calculations were performed yielding the orientations of the corresponding chemical shift tensors. For this series of complexes the phosphorus magnetic shielding tensors are essentially identical, the selenium magnetic shielding tensors are also very similar with respect to each other, and the magnetic shielding tensors of the central metals, cadmium and mercury, display near axial symmetry demonstrating an expected deviation from local S4 symmetry.

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J. Mater. Chem., 2007, 17, 3167 - 3174, DOI: 10.1039/b702745a

Title: NMR, PDF and RMC study of the positive electrode material Li(Ni_0.5Mn_0.5)O₂ synthesized by ion-exchange methods

Authors: Julien Bréger, Kisuk Kang, Jordi Cabana, Gerbrand Ceder and Clare P. Grey

Abstract: The local environment and short-range ordering of Li(Ni_0.5Mn_0.5)O₂, a potential Li-ion battery positive electrode material obtained via an ion-exchange route from Na(Ni_0.5Mn_0.5)O₂, were investigated by using a combination of ⁶Li Magic Angle Spinning (MAS) NMR spectroscopy and neutron Pair Distribution Function (PDF) analysis, associated with Reverse Monte Carlo (RMC) calculations. ⁶Li MAS NMR experiments on Li(Ni_0.5Mn_0.5)O₂ showed that there are almost no Li ions in the transition metal layers. Neutron diffraction data for the precursor Na(Ni_0.5Mn_0.5)O₂ indicated that there is no Na/Ni disorder and that the material is perfectly layered. Neutron PDF analysis of Li(Ni_0.5Mn_0.5)O₂ and Na(Ni_0.5Mn_0.5)O₂ revealed differences in the local transition metal arrangements between those present in the ion-exchanged material and its precursor, and those found in the cathode material synthesized directly from hydroxide starting materials. Large clusters of 3456 atoms were built to investigate cation ordering. Reverse Monte Carlo results, for both the Na and Li-containing compounds, showed a non-random distribution of Ni and Mn cations in the transition metal layers: in the first coordination shell, Ni atoms are on average close to more Mn ions than predicted based on a random distribution of these ions in the transition metal layers. Analysis of the number of Ni/Ni, Mn/Mn and Ni/Mn pairs in the second coordination shell revealed that the Ni and Mn cations show a clear preference for ordering in zigzags rather than in chains.

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J. Mater. Chem., 2007, 17, 4316 - 4319, DOI: 10.1039/b707446h

Title: NMR studies of short and intermediate range ordering of amorphous Si–B–N–C–H pre-ceramic at the pyrolysis stage of 600 °C

Authors: Yee Hwa Sehlleier, Aswin Verhoeven and Martin Jansen

Abstract: Inorganic random networks of a pre-ceramic stage of the amorphous ceramic SiBN₃C, derived from the single-source precursor Cl₃Si(NH)BCl₂ (TADB), have been synthesized with isotope-labeled materials. This allowed characterization at an atomic level of the development of the pre-ceramic polymer at a crucial pyrolysis stage of 600 °C by solid-state NMR. Using several techniques including ¹³C{¹⁵N}REDOR, ¹¹B{¹³C}REDOR, ¹¹B{¹⁵N}REDOR and ¹³C-2D-RFDR, the atomic network of the ¹³C, ¹⁵N enriched sample was investigated. These combined experiments have lead to the important result that carbon forms unsaturated bonds at this stage of the pyrolysis but remains bonded to nitrogen, maintaining a homogeneous distribution of the elements. Carbon atoms seem to be incorporated into the network by using nitrogen atoms as bridges, similar to boron and silicon. The coordinations of boron and silicon are quite similar to those in the final ceramic SiBN₃C after pyrolysis at 1400 °C.

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J. Mater. Chem., 2007, 17, 5090 - 5096, DOI: 10.1039/b712922j

Title: A multinuclear MAS NMR study of calcium-containing aluminosilicate inorganic polymers

Authors: Kenneth J. D. MacKenzie, Mark E. Smith and Alan Wong

Abstract: Natural abundance ⁴³Ca, ²⁷Al and ²⁹Si MAS NMR spectra were acquired for a series of aluminosilicate inorganic polymers (geopolymers) containing up to 50 wt% of Ca(OH)₂, CaCO₃, Ca₃(PO₄)₂ and both amorphous and crystalline CaSiO₃. The ²⁷Al and ²⁹Si MAS NMR spectra of these geopolymers were generally consistent with those of conventional materials, with their XRD diffractograms showing the presence of the added crystalline phases. Comparison of the ⁴³Ca MAS NMR spectra with those of the calcium starting materials suggests that both the calcium silicates and Ca(OH)₂ enter into the geopolymer network, but the spectra of geopolymers containing CaCO₃ and Ca₃(PO₄)₂ are identical to those of the original compound, suggesting that the role of these materials is simply as a filler. At the highest concentration of CaCO₃, the ⁴³Ca resonance of the aragonite polymorph appears in the geopolymer but disappears on heating at 400 °C for 36 h, suggesting that this is a metastable phase formed in situ under the highly alkaline conditions of geopolymer formation and in the presence of calcite nuclei.

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J. Mater. Chem., 2008, 18, 392 - 399, DOI: 10.1039/b714785f

Title: Organosilicas based on purine–pyrimidine base pair assemblies: a solid state NMR point of view

Authors: Guilhem Arrachart, Carole Carcel, Joël J. E. Moreau, Geoffrey Hartmeyer, Bruno Alonso, Dominique Massiot, Gaëlle Creff, Jean-Louis Bantignies, Philippe Dieudonne, Michel Wong Chi Man, Gerhard Althoff, Florence Babonneau and Christian Bonhomme

Abstract: Organosilicas based on adenine (A) and thymine (T) assemblies have been synthesized. A surfactant-free route, based on specific molecular recognition between A and T entities, has been developed. The characterization of the H-bond networks, in both homo- and hetero-assemblies, has been emphasized by using ¹H solid state NMR (nuclear magnetic resonance). The latest experimental developments were implemented (i.e. very fast MAS (magic angle spinning) experiments at 750 MHz and 33 kHz), in order to enhance drastically the spectral resolution. Moreover, ¹H experiments at 67 kHz in 1.3 mm rotors were performed. Spatial connectivities between protons were established by using ¹H–¹H DQ (double quantum) MAS experiments, allowing the precise characterization of A/A, T/T and A/T associations.

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Chemical Physics Letters

Vol: 443, Issue: 4-6, August 6, 2007

pp. 269-273

Title: Some aspects of spin-locking effect in nitrogen-14 quadrupolar spin-system

Author: Rudakov, T.N.

Abstract (English): It was shown that the modified multi-pulse technique enable the observation of a long train of the spin-echo signals.

Publisher: Elsevier Science

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Chemical Physics Letters

Vol: 445, Issue: 1-3, September 4, 2007

pp. 1-5

Title: Proton-detected nitrogen-14 NMR by recoupling of heteronuclear dipolar interactions using symmetry-based sequences

Authors: Cavadini, S.; Abraham, A.; Bodenhausen, G.

Abstract (English): This Letter describes a combination of the heteronuclear multiple-quantum correlation (HMQC) experiment and the symmetry-based R20₅^9 sequence for the indirect observation of ¹⁴N single- (SQ) and double-quantum (DQ) coherences in solids, by recoupling the heteronuclear dipolar interaction between ¹⁴N and ¹H. The picture shows the N-acetylglycine[D₅] experimental spectrum (blue) showing the ¹⁴N SQ response of a rigid ¹⁴N-¹H pair. The quadrupolar parameters obtained with simulation (magenta) are C_Q=-3.21MHz and η_Q=0.32.

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Chemical Physics Letters

Vol: 445, Issue: 4-6, September 13, 2007

pp. 95-98

Title: The nuclear electric quadrupole moment of lutetium from the molecular method

Authors: Haiduke, R.L.A.; da Silva, A.B.F.; Visscher, L.

Abstract (English): The nuclear quadrupole moments of lutetium were determined from calculated electric field gradients and experimental nuclear quadrupole coupling constants.

Publisher: Elsevier Science

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Chemical Physics Letters

Vol: 447, Issue: 1-3, October 15, 2007

pp. 154-161

Title: Optimal control based design of composite dipolar recoupling experiments by analogy to single-spin inversion pulses

Authors: Hansen, J.O.; Kehlet, C.; Bjerring, M.; Vosegaard, T.; Glaser, S.J.; Khaneja, N.; Nielsen, N.Chr.

Abstract (English): Solid-state NMR composite dipolar recoupling experiments designed from a single-spin pulse analogy using optimal control based numerical optimization.

Publisher: Elsevier Science

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Chemical Physics Letters

Vol: 447, Issue: 4-6, October 25, 2007

pp. 370-374

Title: A broad-banded z-rotation windowed phase-modulated Lee-Goldburg pulse sequence for ¹H spectroscopy in solid-state NMR

Authors: Leskes, M.; Madhu, P.K.; Vega, S.

Abstract (English): The design and experimental implementation of an effective z-rotation wPMLG sequence for ¹H spectroscopy in solid-state NMR is demonstrated with a scale factor independent of radio-frequency imperfections.

Publisher: Elsevier Science

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Chemical Physics Letters

Vol: 449, Issue: 1-3, November 26, 2007

pp. 86-91

Title: Effects of spin diffusion on spin-lattice relaxation in solid-state ²H MAS NMR spectroscopy

Authors: Cutajar, M.; Lewis, M.H.; Wimperis, S.

Abstract (English): The phenomenon of MAS-enhanced spin diffusion can lead to observation of a common spin-lattice (T₁) relaxation time in ²H NMR.

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Chemical Physics Letters

Vol: 450, Issue: 4-6, January 4, 2008

pp. 417-421

Title: Sensitivity enhancement of solid-state NMR spectra of half-integer spin quadrupolar nuclei: Double- or single-frequency sweeps? Insights from the hyperbolic secant experiment

Authors: Nakashima, T.T.; Wasylishen, R.E.; Siegel, R.; Ooms, K.J.

Abstract (English): Enhancement of the central NMR transition of quadrupolar nuclei in solids by selective irradiation of one ssb in MAS experiments.

Hiyam's Journal Update

J. Am. Chem. Soc., 130 (3), 945 -954, 2008.
Quantifying Weak Hydrogen Bonding in Uracil and 4-Cyano-4'-ethynylbiphenyl: A Combined Computational and Experimental Investigation of NMR Chemical Shifts in the Solid State
Anne-Christine Uldry, John M. Griffin, Jonathan R. Yates, Marta Pérez-Torralba, M. Dolores Santa María, Amy L. Webber, Maximus L. L. Beaumont, Ago Samoson, Rosa María Claramunt, Chris J. Pickard, and Steven P. Brown*

Abstract:
Weak hydrogen bonding in uracil and 4-cyano-4'-ethynylbiphenyl, for which single-crystal diffraction structures reveal close CH···O=C and CCH···NC distances, is investigated in a study that combines the experimental determination of 1H, 13C, and 15N chemical shifts by magic-angle spinning (MAS) solid-state NMR with first-principles calculations using plane-wave basis sets. An optimized synthetic route, including the isolation and characterization of intermediates, to 4-cyano-4'-ethynylbiphenyl at natural abundance and with 13C13CH and 15NC labeling is described. The difference in chemical shifts calculated, on the one hand, for the full crystal structure and, on the other hand, for an isolated molecule depends on both intermolecular hydrogen bonding interactions and aromatic ring current effects. In this study, the two effects are separated computationally by, first, determining the difference in chemical shift between that calculated for a plane (uracil) or an isolated chain (4-cyano-4'-ethynylbiphenyl) and that calculated for an isolated molecule and by, second, calculating intraplane or intrachain nucleus-independent chemical shifts that quantify the ring current effects caused by neighboring molecules. For uracil, isolated molecule to plane changes in the 1H chemical shift of 2.0 and 2.2 ppm are determined for the CH protons involved in CH···O weak hydrogen bonding; this compares to changes of 5.1 and 5.4 ppm for the NH protons involved in conventional NH···O hydrogen bonding. A comparison of CH bond lengths for geometrically relaxed uracil molecules in the crystal structure and for geometrically relaxed isolated molecules reveals differences of no more than 0.002 Å, which corresponds to changes in the calculated 1H chemical shifts of at most 0.1 ppm. For the CCH···NC weak hydrogen bonds in 4-cyano-4'-ethynylbiphenyl, the calculated molecule to chain changes are of similar magnitude but opposite sign for the donor 13C and acceptor 15N nuclei. In uracil and 4-cyano-4'-ethynylbiphenyl, the CH hydrogen-bonding donors are sp2 and sp hybridized, respectively; a comparison of the calculated changes in 1H chemical shift with those for the sp3 hybridized CH donors in maltose (Yates et al. J. Am. Chem. Soc. 2005, 127, 10216) reveals no marked dependence on hybridization for weak hydrogen-bonding strength.

J. Am. Chem. Soc., 130 (3), 918 -924, 2008.
Solid-State 19F NMR Spectroscopy Reveals That Trp41 Participates in the Gating Mechanism of the M2 Proton Channel of Influenza A Virus
Raiker Witter, Farhod Nozirov, Ulrich Sternberg, Timothy A. Cross, Anne S. Ulrich,* and Riqiang Fu*

Abstract:
The integral membrane protein M2 of influenza A virus assembles as a tetrameric bundle to form a proton-conducting channel that is activated by low pH. The side chain of His37 in the transmembrane -helix is known to play an important role in the pH activation of the proton channel. It has also been suggested that Trp41, which is located in an adjacent turn of the helix, forms part of the gating mechanism. Here, a synthetic 25-residue peptide containing the M2 transmembrane domain was labeled with 6F-Trp41 and studied in lipid membranes by solid-state 19F NMR. We monitored the pH-dependent differences in the 19F dipolar couplings and motionally narrowed chemical shift anisotropies of this 6F-Trp41 residue, and we discuss the pH activation mechanism of the H+ channel. At pH 8.0, the structural parameters implicate an inactivated state, while at pH 5.3 the tryptophan conformation represents the activated state. With the aid of COSMOS force field simulations, we have obtained new side-chain torsion angles for Trp41 in the inactivated state (1 = -100 ± 10, 2 = +110 ± 10), and we predict a most probable activated state with 1 = -50 ± 10 and 2 = +115 ± 10. We have also validated the torsion angles of His37 in the inactivated state as 1 = -175 ± 10 and 2 = -170 ± 10.

Wednesday, January 16, 2008

Hiyam's Journal Update

J. Am. Chem. Soc., 130 (2), 414 -415, 2008.
Unexpected Fractionation in Site-Specific 13C Isotopic Distribution Detected by Quantitative 13C NMR at Natural Abundance
Eliot P. Botosoa, Elsa Caytan, Virginie Silvestre, Richard J. Robins, Serge Akoka, and Gérald S. Remaud

Abstract:
The recent development of 13C NMR to measure absolute 13C/12C ratios at natural abundance has made it possible to examine site-by-site variation at natural abundance. This technique has been applied to two common physical processes: distillation and column chromatography. It is shown that the target molecules, ethanol and vanillin, respectively, both show isotopic fractionation that differs in size and/or in sense at each carbon atom. The observation of this disparity in behavior is novel and unexpected. 13C SNIF-NMR appears as a new effective tool to study noncovalent isotope effects (NCIE) on target molecules.

J. Am. Chem. Soc., 130 (2), 481 -490, 2008.
31P Magic Angle Spinning NMR Spectroscopy of Paramagnetic Rare-Earth-Substituted Keggin and Wells-Dawson Solids
Wenlin Huang, Mark Schopfer, Cheng Zhang, Robertha C. Howell, Louis Todaro, Becky A. Gee, Lynn C. Francesconi,* and Tatyana Polenova*

Abstract:
Paramagnetic rare-earth elements have been examined as NMR structural probes in polyoxoanionic solids, which have a variety of applications as luminescent materials that are usually disordered and therefore intractable by traditional structural methods. Thirteen Keggin and Wells-Dawson polyoxotungstates containing substitutions with lanthanides of different effective magnetic moments have been examined by 31P magic angle spinning NMR spectroscopy. The electron-nuclear dipolar interaction dominating the spinning sideband envelopes is determined by the lanthanide's magnetic moment and was found to be a sensitive probe of the nature of the polyoxoanion, of the positional isomerism, and of the ion stoichiometry. Electron-nuclear dipolar anisotropies computed based on the point-dipole approximation are generally in good agreement with the experimental results. The choice of a specific lanthanide as a structural probe can be tailored to the desired distance range between the phosphorus atoms and the paramagnetic centers to be probed. This approach is expected to be particularly useful in the paramagnetic polyoxoanionic materials lacking long-range order.

Phys. Rev. B 76, 214424 (2007)

Magnetization and 63Cu NMR studies on granular FeCu alloys
B. Bandyopadhyay, B. Pahari, and K. Ghoshray

Nanostructured FeCu granular alloys (Fe ~1%–20%) have been prepared by borohydride reduction and characterized by energy dispersive spectroscopy, x-ray, and transmission electron microscopy studies. Study of zero-field-cooling–field-cooling magnetization yields blocking temperature distribution of magnetic fine particles system in all samples. At low Fe concentration, the magnetizations of the samples combine superparamagnetism and paramagnetism near room temperature and small hystereses at 5 K. High Fe content alloys are almost entirely ferromagnetic even at 300 K. However, in all these samples, the observation of the 63Cu nuclear magnetic resonance signal at all temperatures 4–300 K confirms the existence of a paramagnetic component having ~0.02–0.04 at. % Fe in Cu. The temperature dependence behavior of Fe contribution to 63Cu NMR linewidth and the Knight shift indicate that the paramagnetic component might exhibit a Kondo temperature of ~24 K that is significantly higher than that obtained in bulk dilute FeCu alloys.

Monday, January 14, 2008

Chem. Rev. - Chemical reviews, up to Jan. 2008

Chem. Rev. - Chemical reviews, up to Jan. 2008

Nothing directly to report, though a few issues you may wish to check out, for general interest and research proposals. - Rob

Contents:
Dec. 2007 - ORGANOCATALYSIS
Oct. 2007 - 100TH THEMATIC ISSUE - HYDROGEN
Apr. 2007 - ORGANIC ELECTRONICS AND OPTOELECTRONICS

ACR - Accounts of Chemical Research - up to Dec. 2007, vol. 40, iss 12.

ACR - Accounts of Chemical Research - up to Dec. 2007, vol. 40, iss 12.

Acc. Chem. Res., 40 (9), 738–746 10.1021/ar600030j
Web Release Date: April 27, 2007
Copyright © 2007 American Chemical Society

Advanced Solid State NMR Techniques for the Characterization of Sol–Gel-Derived Materials

Christian Bonhomme,* Cristina Coelho, Niki Baccile, Christel Gervais, Thierry Azaïs, and Florence Babonneau
Received November 22, 2006

Abstract:

A large array of advanced solid state NMR (nuclear magnetic resonance) techniques is presented in the frame of the structural characterization of sol–gel-derived materials. These techniques include the pertinent detection of 17O chemical shifts, MAS (magic angle spinning) J spectroscopy in the solid state, high-resolution 1H spectroscopy, heteronuclear and homonuclear D (dipolar)-derived multidimensional correlation experiments, and first-principles calculations of NMR parameters. This spectroscopic approach is suitable for the in-depth description of multicomponent sol–gel derivatives, crystalline and amorphous biocompatible silicophosphates, Al–O–P clusters, and templated porous materials. It offers unique perspectives for the description of the hybrid interfaces in terms of chemical and spatial connectivities.

CMR - Concepts in Magnetic Resonance - up to Volume 30A Issue 6 - November 2007 (309-393)

Concepts in Magnetic Resonance - up to Volume 30A Issue 6 - November 2007 (309-393)

Concepts in Magnetic Resonance Part A
Volume 30A, Issue 6 , Pages 309 - 348
Published Online: 27 Nov 2007

NMR and the uncertainty principle: How to and how not to interpret homogeneous line broadening and pulse nonselectivity. I. The fundamentals
Csaba Szántay Jr. *
*Correspondence to Csaba szántay Jr., Spectroscopic Research Division, Gedeon Richter Plc., H-1475 Budapest, 10, POB 27, Hungary

Dedicated to Prof. Csaba Szántay Sr. on the occasion of his 80th birthday

Keywords
uncertainty principle • Fourier transform • NMR lineshape • excitation profile • harmonic phasor

Abstract
Both the essence of homogeneous NMR line broadening as well as the fact that a short monochromatic radiofrequency pulse exhibits a polychromatic spectral bandwidth and is consequently associated with a broad off-resonance NMR excitation band are often rationalized in terms of a superficial and/or misguided use of the Uncertainty Principle. The problem is of quite fundamental nature, and stems from several deeper issues that reach beyond the world of NMR. To explore this topic, we need to go back to some basic concepts including the Fourier transform, time-frequency analysis, different versions of the uncertainty principle, and linear systems theory. My theme will be developed in four subsequent articles. First, by employing an approach that is unconventional in its thematic structure and applied nomenclature, I present an overview of some basic ideas (periodicity, basis functions, harmonic waves, density functions, etc.) that will then pave the way to discussing, in a somewhat avant-garde manner, the Fourier transform in Part II. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 309-348, 2007.
Received: 20 February 2007; Accepted: 14 August 2007

Digital Object Identifier (DOI) - 10.1002/cmr.a.20098

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Concepts in Magnetic Resonance Part A
Volume 30A, Issue 5 , Pages 246 - 260
Published Online: 4 Sep 2007

Nuclear magnetic moments from NMR spectra - Experimental gas phase studies and nuclear shielding calculations
Karol Jackowski 1 *, Micha Jaszuski 2
*Correspondence to Karol Jackowski, Laboratory of NMR Spectroscopy, Faculty of Chemistry, University of Warsaw, 02-093 Warszawa, Poland

Keywords
nuclear magnetic dipole moments • NMR in gases • shielding constants • ab initio calculations

Abstract
NMR spectra of gaseous compounds and quantum chemical calculations are combined to determine new accurate values of magnetic dipole moments for a series of nuclei. We have analyzed shielding constants, resonance frequencies, and nuclear magnetic moments for a group of simple molecules. The chemical shifts and resonance frequencies are measured at 300 K and extrapolated to the zero-density limit in order to remove all the intermolecular effects from the experimental parameters. The absolute shielding constants in the studied molecules are obtained from ab initio calculations. Assuming the proton magnetic moment as the reference, we determine the nuclear magnetic moments of 13C, 14N, 15N, 17O, 19F, 29Si, 31P, 33S, and 73Ge. The new nuclear magnetic moments are consistent with the experimental NMR parameters, and using these new values one can for the first time predict successfully the shielding constant of a nucleus in a molecule when the corresponding resonance frequency is known. Concepts Magn Reson Part A 30A: 246-260, 2007.
Received: 15 January 2007; Revised: 5 June 2007; Accepted: 8 June 2007

Digital Object Identifier (DOI) - 10.1002/cmr.a.20091

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JMR - Journal of Magnetic Resonance - up to January 2008

JMR - Journal of Magnetic Resonance - up to January 2008

Journal of Magnetic Resonance
Volume 190, Issue 1, January 2008, Pages 1-6
doi:10.1016/j.jmr.2007.09.016

Pre-SAT180, a simple and effective method for residual water suppression

Huaping Mo, and Daniel Raftery
Received 25 July 2007; revised 12 September 2007. Available online 25 September 2007.

Abstract

Water located outside the NMR detection coil experiences a reduced RF field intensity. This "faraway water" is known to be very difficult to suppress and often gives rise to a large residual solvent signal. Pre-SAT180 (Pre-Saturation with Adiabatic Toggling of 180 degree pulse inversion) is proposed to cancel the residual water contribution efficiently. Compared with several popular methods such as 1D NOESY with pre-saturation or 270° excitation, Pre-SAT180 has a number of advantages, including: full retention of signal intensity and selectivity, good phase properties, easy setup, and high tolerance to pulse missettings.

Keywords: Pre-SAT180; NMR; Water suppression; Pre-saturation; Metabolomics; Urine metabolomics

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Journal of Magnetic Resonance
Volume 190, Issue 1, January 2008, Pages 135-141
doi:10.1016/j.jmr.2007.07.012

A Hall effect angle detector for solid-state NMR

Salvatore Mamone, André Dorsch, Ole G. Johannessen, Manoj V. Naik, P.K. Madhu and Malcolm H. Levitt
Received 27 June 2007. Available online 29 August 2007.

Abstract

We describe a new method for independent monitoring of the angle between the spinning axis and the magnetic field in solid-state NMR. A Hall effect magnetic flux sensor is fixed to the spinning housing, so that a change in the stator orientation leads to a change in the angle between the Hall plane and the static magnetic field. This leads to a change in the Hall voltage generated by the sensor when an electric current is passed through it. The Hall voltage may be measured externally by a precision voltmeter, allowing the spinning angle to be measured non-mechanically and independent of the NMR experiment. If the Hall sensor is mounted so that the magnetic field is approximately parallel to the Hall plane, the Hall voltage becomes highly sensitive to the stator orientation. The current angular accuracy is around 10 millidegrees. The precautions needed to achieve higher angular accuracy are described.

Keywords: Magic-angle spinning; Hall effect; NMR; Solid-state NMR

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Journal of Magnetic Resonance
Volume 190, Issue 1, January 2008, Pages 165-170

doi:10.1016/j.jmr.2007.10.002

Proton-detected separated local field spectroscopy

Chin H. Wu and Stanley J. Opella
Received 8 August 2007; revised 29 September 2007. Available online 10 October 2007.

Abstract

PISEMO, a separated local field experiment that can be performed with either direct 15N (or 13C) detection or indirect 1H detection, is demonstrated on a single crystal of a model peptide. The 1H signals modulated by 1H–15N heteronuclear dipole–dipole couplings are observed stroboscopically in the windows of the multiple-pulse sequence used to attenuate 1H–1H homonuclear dipole–dipole couplings. 1H-detection yields spectra with about 2.5 times the signal to noise ratio observed with 15N-detection under equivalent conditions. Resolution in both the 15N chemical shift and 1H–15N heteronuclear dipole–dipole coupling dimensions is similar to that observed with PISEMA, however, since only on-resonance pulses are utilized, the bandwidth is better.

Keywords: PISEMA; PISEMO; Multiple-pulse; Double-resonance; Crystal

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Journal of Magnetic Resonance
Volume 189, Issue 1, November 2007, Pages 104-113
doi:10.1016/j.jmr.2007.08.019.

Stripline probes for nuclear magnetic resonance

P.J.M. van Bentum, J.W.G. Janssen, A.P.M. Kentgens, J. Bart and J.G.E. Gardeniers
Received 20 July 2007; revised 24 August 2007. Available online 7 September 2007.

Abstract

A novel route towards chip integrated NMR analysis is evaluated. The basic element in the design is a stripline RF ‘coil' which can be defined in a single layer lithographic process and which is fully scalable to smaller dimensions. The sensitivity of such a planar structure can be superior to that of a conventional 3D helix. The basic properties, such as RF field strength, homogeneity and susceptibility broadening are discussed in detail. Secondary effects related to the thermal characteristics are discussed in simplified models. Preliminary NMR tests of basic solid and liquid samples measured at 600 MHz confirm the central findings of the design study. It is concluded that the stripline structure can be a valuable addition to the NMR toolbox; it combines high sensitivity with low susceptibility broadening and high power handling capabilities in a simple scalable design.

Keywords: NMR; Microcoils; Stripline; Microfluidics; High resolution NMR; Thin films; Wide-line NMR; RF coil design

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Journal of Magnetic Resonance
Volume 189, Issue 1, November 2007, Pages 20-31
doi:10.1016/j.jmr.2007.06.017

Pursuing structure in microcrystalline solids with independent molecules in the unit cell using 1H–13C correlation data

James K. Harper, Mark Strohmeier and David M. Grant
Received 4 May 2007. Available online 14 August 2007.

Abstract

The 1H–13C solid-state NMR heteronuclear correlation (HETCOR) experiment is demonstrated to provide shift assignments in certain powders that have two or more structurally independent molecules in the unit cell (i.e. multiple molecules per asymmetric unit). Although this class of solids is often difficult to characterize using other methods, HETCOR provides both the conventional assignment of shifts to molecular positions and associates many resonances with specific molecules in the asymmetric unit. Such assignments facilitate conformational characterization of the individual molecules of the asymmetric unit and the first such characterization solely from solid-state NMR data is described. HETCOR offers advantages in sensitivity over prior methods that assign resonances in the asymmetric unit by 13C–13C correlations and therefore allows shorter average analysis times in natural abundance materials. The 1H–13C analysis is demonstrated first on materials with known shift assignments from INADEQUATE data (santonin and Ca(OAc)2 phase I) to verify the technique and subsequently is extended to a pair of unknown solids: (+)-catechin and Ca(OAc)2 phase II. Sufficient sensitivity and resolution is achieved in the spectra to provide assignments to one of the specific molecules of the asymmetric unit at over 54% of the sites.

Keywords: Heteronuclear correlation; Powders; Asymmetric unit

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Journal of Magnetic Resonance
Volume 188, Issue 2, October 2007, Pages 246-259
doi:10.1016/j.jmr.2007.07.009

Determination of NMR interaction parameters from double rotation NMR

I. Hung, A. Wong, A.P. Howes, T. Anupõld, J. Past, A. Samoson, X. Mo, G. Wu, M.E. Smith, S.P. Brown and R. Dupree
Received 30 May 2007; revised 18 July 2007. Available online 3 August 2007.

Abstract

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The 17O nuclei in isotopically enriched l-alanine and OPPh3 are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 ± 20 ppm and 350 ± 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of ±5–10°. For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V33 and ?33) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh3 the principal axis of the 17O EFG is found to be close to the O–P bond, and the 17O–31P one-bond J coupling (1JOP = 161 ± 2 Hz) is determined to a much higher accuracy than previously.

Keywords: Solid-state NMR; Double rotation; Quadrupolar interaction; Chemical shift anisotropy; J-coupling; Dipolar coupling; Oxygen-17

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Journal of Magnetic Resonance
Volume 188, Issue 2, October 2007, Pages 267-274
doi:10.1016/j.jmr.2007.06.015

Efficient cross polarization with simultaneous adiabatic frequency sweep on the source and target channels

Weng Kung Peng and Kazuyuki Takeda
Received 13 April 2007; revised 21 June 2007. Available online 3 August 2007.

Abstract

In this work, we propose a new and efficient heteronuclear cross polarization scheme, in which adiabatic frequency sweeps from far off-resonance toward on-resonance are applied simultaneously on both the source and target spins. This technique, which we call as Simultaneous ADIabatic Spin-locking Cross Polarization (SADIS CP), is capable of efficiently locking both the source and target spins with moderate power even in the presence of large spectral distribution and fast relaxation. It is shown that by keeping the time-dependent Hartmann–Hahn mismatch minimal throughout the mixing period, polarization transfer can be accelerated. Experiments are demonstrated in a powder sample of l-alanine.

Keywords: Cross polarization; Simultaneous adiabatic frequency sweep; Spin–lattice relaxation time in the rotating frame; Time-dependent Hartmann–Hahn mismatch

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Journal of Magnetic Resonance
Volume 188, Issue 2, October 2007, Pages 311-321
doi:10.1016/j.jmr.2007.07.005

High-field 75As NMR study of arsenic oxysalts

Geoffrey M. Bowers and R. James Kirkpatrick
Received 18 June 2007; revised 16 July 2007. Available online 2 August 2007.

Abstract

Arsenic is an important environmental hazard, but there have been few NMR investigations of its molecular scale structure and dynamics, due principally to the large quadrupole moment of 75As and consequent large quadrupole couplings. We examine here the potential of existing, single-field solid-state NMR technology to investigate solids containing arsenate and arsenite oxyanions. The results show that current techniques have significant potential for arsenates that do not contain both protonated Click to view the MathML source groups and structural water molecules, but that the quadrupole couplings for the arsenites examined here are large enough that interpretation of the spectra is difficult, even at 21.1 T. Compounds that contain both structural H2O molecules and protonated arsenate groups do not yield resolvable signal, likely a result of T2 effects related to a combination of strong quadrupolar interactions and proton exchange. Spin-echo experiments at 11.7 and 14.1 T were effective for Li3AsO4 and CsH2AsO4, as were whole-pattern spikelet experiments for arsenate oxide (As2O5) at 17.6 and 21.1 T. The central transition resonance of Ca3(AsO4)2·8H2O is not, vert, similar6 MHz broad and required a non-conventional, histogram-style spikelet method at high field to improve acquisition efficiency. This approach reduces the acquisition time due to the sensitivity enhancement of the spikelet sequence and a reduction in the number of frequency increments required to map the resonance. Despite the large quadrupole couplings, we have identified a correlation between the 75As isotropic chemical shift and the electronegativity of the next-nearest neighbor cation in arsenate compounds.

Keywords: Arsenic; Histogram; QCPMG; Shielding; Solid-state nuclear magnetic resonance

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Journal of Magnetic Resonance
Volume 188, Issue 1, September 2007, Pages 49-55
doi:10.1016/j.jmr.2007.06.003

Using chemical shift anisotropy to resolve isotropic signals in solid-state NMR

Matthew S. Ironside, Robin S. Stein and Melinda J. Duer
Received 27 March 2007; revised 6 June 2007. Available online 15 June 2007.

Abstract

A key problem in solid-state NMR is resolving overlapping isotropic signals. We present here a two-dimensional method which can enable sites with the same isotropic chemical shift to be distinguished according to their chemical shift anisotropy and asymmetry. The method involves correlating sideband spectra at different effective spinning rates using CSA-amplification pulse sequences. The resulting two-dimensional correlation pattern allows very accurate determination of the chemical shift principal values in addition to the recovery of parameters for two overlapping patterns which allows the resolution of overlapping signals.

Keywords: CSA recoupling; CSA-amplified PASS; Overlapping signals; Spinning sidebands; 31P NMR

JMR - Journal of Magnetic Resonance - up to January 2008

MRC Special Issue - Volume 45 Issue S1 , Pages 1 - 260 (December 2007) - Special Issue: New techniques in solid-state NMR

MRC Special Issue - Volume 45 Issue S1 , Pages 1 - 260 (December 2007) - Special Issue: New techniques in solid-state NMR

This blog item simply contains the table of contents for the special "New techniques in solid-state NMR" issue of MRC that came out in late Dec. 2007. There are quite a few good papers here which are worth a look.
-Rob

Reviews

Lipid bilayers: an essential environment for the understanding of membrane proteins (p S2-S11)
Richard C. Page, Conggang Li, Jian Hu, Fei Philip Gao, Timothy A. Cross
Published Online: Dec 19 2007 6:36AM
DOI: 10.1002/mrc.2077

Studying porous materials with krypton-83 NMR spectroscopy (p S12-S23)
Zackary I. Cleveland, Thomas Meersmann
Published Online: Dec 19 2007 6:34AM
DOI: 10.1002/mrc.2084

High-resolution solid-state MAS NMR of proteins - Crh as an example (p S24-S31)
Anja Böckmann
Published Online: Dec 17 2007 3:43AM
DOI: 10.1002/mrc.2106

The structure, dynamics, and energetics of protein adsorption - lessons learned from adsorption of statherin to hydroxyapatite (p S32-S47)
Gil Goobes, Rivka Goobes, Wendy J. Shaw, James M. Gibson, Joanna R. Long, Vinodhkumar Raghunathan, Ora Schueler-Furman, Jennifer M. Popham, David Baker, Charles T. Campbell, Patrick S. Stayton, Gary P. Drobny
Published Online: Jan 3 2008 3:55AM
DOI: 10.1002/mrc.2123

Chromatographic NMR: a tool for the analysis of mixtures of small molecules (p S48-S55)
Stefano Caldarelli
Published Online: Dec 17 2007 3:43AM
DOI: 10.1002/mrc.2143

Research Articles

15N solid-NMR and X-ray diffraction studies of N-confused porphyrins (p S56-S60)
Masashi Fukuchi, K. Takegoshi, Tomoya Ishizuka, Hiroyuki Furuta
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2066

Dipolar double-quantum filtered rotational-echo double resonance (p S61-S64)
Shigeru Matsuoka, Jacob Schaefer
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2076

Dipolar recoupling of I = 1/2, S = 3/2 spin pairs with SEDOR for static and spinning samples (p S65-S67)
Terry Gullion
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2083

The determination of 17O NMR parameters of hydroxyl oxygen: A combined deuteration and DOR approach (p S68-S72)
Alan Wong, Ivan Hung, Andy P. Howes, Tiit Anupõld, Jaan Past, Ago Samoson, Steven P. Brown, Mark E. Smith, Ray Dupree
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2088

Magic angle spinning NMR spectroscopy of thioredoxin reassemblies (p S73-S83)
Jun Yang, Sivakumar Paramasivam, Dabeiba Marulanda, Marcela Cataldi, Maria Luisa Tasayco, Tatyana Polenova
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2092

J-based 2D homonuclear and heteronuclear correlation in solid-state proteins (p S84-S92)
Lingling Chen, J. Michael Kaiser, Jinfeng Lai, Tatyana Polenova, Jun Yang, Chad M. Rienstra, Leonard J. Mueller
Published Online: Dec 21 2007 9:21AM
DOI: 10.1002/mrc.2107

On the orientational dependence of resolution in 1H solid-state NMR, and its role in MAS, CRAMPS and delayed-acquisition experiments (p S93-S100)
Vadim E. Zorin, Benedicte Elena, Anne Lesage, Lyndon Emsley, Paul Hodgkinson
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2108

Conformational constraints in solid-state NMR of uniformly labeled polypeptides from double single-quantum-filtered rotational echo double resonance (p S101-S106)
Nathan A. Oyler, Robert Tycko
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2110

Tailoring 13C labeling for triple-resonance solid-state NMR experiments on aligned samples of proteins (p s107-s115)
Neeraj Sinha, Fabian V. Filipp, Lena Jairam, Sang Ho Park, Joel Bradley, Stanley J. Opella
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2121

Investigation of structure and dynamics in the sodium metallocenes CpNa and CpNa·THF via solid-state NMR, X-ray diffraction and computational modelling (p S116-S128)
Cory M. Widdifield, Joel A. Tang, Charles L. B. Macdonald, Robert W. Schurko
Published Online: Jan 3 2008 3:55AM
DOI: 10.1002/mrc.2124

Long-range 19Fbond15N distance measurements in highly-13C, 15N-enriched solid proteins with 19F-dephased REDOR shift (FRESH) spectroscopy (p S129-S134)
Daniel T. Graesser, Benjamin J. Wylie, Andrew J. Nieuwkoop, W. Trent Franks, Chad M. Rienstra
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2126

Solid-state NMR studies of hydrogen bonding networks and proton transport pathways based on anion and cation dynamics (p S135-S143)
Jason W. Traer, Gillian R. Goward
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2127

Using 17O solid-state NMR and first principles calculation to characterise structure and dynamics in inorganic framework materials (p S144-S155)
Anne Soleilhavoup, Matthew R. Hampson, Stewart J. Clark, John S. O. Evans, Paul Hodgkinson
Published Online: Dec 21 2007 9:21AM
DOI: 10.1002/mrc.2128

Quantitative measurement of differential 15NbondHalpha/betaT2 relaxation rates in a perdeuterated protein by MAS solid-state NMR spectroscopy (p S156-S160)
Veniamin Chevelkov, Anne Diehl, Bernd Reif
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2129

Asymmetric doublets in MAS NMR: coherent and incoherent mechanisms (p S161-S173)
N. R. Skrynnikov
Published Online: Dec 21 2007 9:46AM
DOI: 10.1002/mrc.2162

Chemical shift computations on a crystallographic basis: some reflections and comments (p S174-S186)
Robin K. Harris, Paul Hodgkinson, Chris J. Pickard, Jonathan R. Yates, Vadim Zorin
Published Online: Dec 21 2007 9:21AM
DOI: 10.1002/mrc.2132

Measurement of through-space connectivities between spin-1/2 and quadrupolar nuclei in solid-state NMR: the TEDOR-MQMAS method (p S187-S191)
J. P. Amoureux, J. Trébosc, G. Tricot
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2135

Membrane orientation of the Na,K-ATPase regulatory membrane protein CHIF determined by solid-state NMR (p S192-S197)
Carla M. Franzin, Peter Teriete, Francesca M. Marassi
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2144

Low-load rotor-synchronised Hahn-echo pulse train (RS-HEPT) 1H decoupling in solid-state NMR: factors affecting MAS spin-echo dephasing times (p S198-S208)
John M. Griffin, Carmen Tripon, Ago Samoson, Claudiu Filip, Steven P. Brown
Published Online: Dec 21 2007 6:46AM
DOI: 10.1002/mrc.2145

Optimizing ssNMR experiments for dilute proteins in heterogeneous mixtures at high magnetic fields (p S209-S220)
Seth A. McNeill, Peter L. Gor'kov, Jochem Struppe, William W. Brey, Joanna R. Long
Published Online: Dec 21 2007 9:21AM
DOI: 10.1002/mrc.2146

Efficient low-power heteronuclear decoupling in 13C high-resolution solid-state NMR under fast magic angle spinning (p S221-S230)
Mrignayani Kotecha, Nalinda P. Wickramasinghe, Yoshitaka Ishii
Published Online: Dec 21 2007 9:21AM
DOI: 10.1002/mrc.2151

Environmentally friendly flame retardants. A detailed solid-state NMR study of melamine orthophosphate (p S231-S246)
Andreas Brinkmann, Victor M. Litvinov, Arno P. M. Kentgens
Published Online: Dec 21 2007 9:22AM
DOI: 10.1002/mrc.2159

Investigation of finite-pulse radiofrequency-driven recoupling methods for measurement of intercarbonyl distances in polycrystalline and membrane-associated HIV fusion peptide samples (p S247-S260)
Zhaoxiong Zheng, Wei Qiang, David P. Weliky
Published Online: Dec 21 2007 9:22AM
DOI: 10.1002/mrc.2160

MRC - Magnetic Resonance in Chemistry - up to Jan. 2008

MRC - Magnetic Resonance in Chemistry - up to Jan. 2008

Magnetic Resonance in Chemistry
Volume 45, Issue 9 , Pages 797 - 800
Published Online: 30 Jul 2007

Spectral Assignments and Reference Data
Statistical analysis of 13C and 15N NMR chemical shifts from GIAO/B3LYP/6-311 + + G** calculated absolute shieldings
Fernando Blanco, Ibon Alkorta, José Elguero
Instituto de Química Médica, CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain

Keywords - 13C NMR • 15N NMR • GIAO

Abstract
The 13C and 15N absolute shieldings of 28 compounds have been calculated at the GIAO/B3LYP/6-311 + + G** level to complete a collection of data already published. This has allowed us to devise new equations relating and for these nuclei based on 461 points (13C) and 70(72) points (15N).
Received: 22 May 2007; Revised: 11 June 2007; Accepted: 14 June 2007

Digital Object Identifier (DOI) - 10.1002/mrc.2053 About DOI

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Magnetic Resonance in Chemistry
Volume 45, Issue 10 , Pages 814 - 818
Published Online: 9 Aug 2007

Research Article
High-resolution magic-angle spinning NMR for the identification of reaction products directly from thin-layer chromatography spots
Scott A. Bradley *, Rebekah L. McLaughlin
Department of Drug Metabolism, Merck Research Laboratories, Rahway, NJ 07065, USA

Keywords
NMR • 1H • thin-layer chromatography • TLC • magic-angle spinning • HRMAS • Nano probe

Abstract
We have investigated the prospect of identifying organic reaction products directly from separated thin-layer chromatography (TLC) spots with high-resolution magic-angle spinning (HRMAS) NMR. The concept is to use the TLC spots for NMR analysis so that spectra can be obtained before the reaction is worked up, but without having to elute the product from the TLC stationary phase. Thus, the separated spot is scraped from the plate, transferred to an HRMAS sample rotor, and suspended with a deuterated solvent. Herein, we describe the effects of having the stationary phase present during NMR acquisition. Using a Varian 4 mm gHX Nanoprobe and rotenone as a test compound, we found that the presence of the stationary phase during NMR acquisition resulted in (i) a large, broad background signal near 4.6 ppm and (ii) a decrease in the signal-to-noise ratio due to the adsorption of the product molecules to the adsorbent. However, both effects could be adequately and conveniently eliminated. The background signal was removed by using either a CPMG pulse sequence or chemical exchange. The adsorption was avoided by using a more polar solvent system. Finally, we found that spectra with good signal-to-noise ratio and resolution could be acquired in a matter of minutes even for cases of limited product concentration. Therefore, we believe the technique has value and provides the organic chemist with another option to obtain NMR data critical for structural elucidation or verification.

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Magnetic Resonance in Chemistry
Volume 45, Issue 10 , Pages 860 - 864
Published Online: 29 Aug 2007

Research Article
Dependence of 35Cl NQR on hydrogen bonding and temperature in dichlorophenol-aniline charge transfer complexes
D. Ramananda, K. P. Ramesh, J. Uchil

*Correspondence to D. Ramananda, Department of Materials Science, Mangalore University, Mangalore, India.

Keywords
hydrogen bonded • NQR • charge transfer • chemical bond • ionic bond • double bond

Abstract
The hydrogen-bonded charge transfer complexes of aniline with -acceptors (or proton donors) such as 2,5-, 2,6-, 3,4- and 3,5-dichlorophenol were prepared. The 35Cl nuclear quadrupole resonance (NQR) frequencies of these charge transfer complexes in the temperature range 77-300 K were measured to ascertain the existence or otherwise of a phase transition upon complex formation. Further, the NQR frequency and asymmetry parameter of the electric field gradient at the site of quadrupole nucleus were used to estimate the chemical bond parameters, namely ionic bond, double bond character of the carbon-chlorine(CCl) bond and the percentage charge transfer between the donor-acceptor components in charge transfer complexes. The effect of hydrogen bonding and temperature on the charge transfer process is analysed.
Received: 14 February 2007; Revised: 21 June 2007; Accepted: 26 June 2007

Digital Object Identifier (DOI) - 10.1002/mrc.2059

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Magnetic Resonance in Chemistry
Volume 45, Issue 11 , Pages 962 - 970
Published Online: 8 Oct 2007

Research Article
Solid state NMR characterization of individual compounds and solid solutions formed in Sc2O3V2O5Nb2O5Ta2O5 system
Dzhalil Khabibulin, Konstantin Romanenko, Mikhail Zuev, Olga Lapina
*Correspondence to Olga Lapina, Boreskov Institute of Catalysis, SB RAS, pr. Lavrentieva, 5, 630090 Novosibirsk, Russia.

Keywords
solid state NMR • SATRAS • MAS • 51V • 45Sc • 93Nb • solid solutions • bulk oxides • vanadates • niobates

Abstract
In this study, 51V, 45Sc and 93Nb MAS NMR combined with satellite transition spectroscopy analysis were used to characterize the complex solid mixtures: VNb9(1-x)Ta9xO25, ScNb(1-x)TaxO4 and ScNb2(1-x)Ta2xVO9 (x = 0, 0.3, 0.5, 0.7, 1.0). This led us to describe the structures of Sc and V sites. The conclusions were based on accurate values for 51V quadrupole coupling and chemical shift tensors obtained with 51V MAS NMR/SATRAS for VNb9O25, VTa9O25 and ScVO4. The 45Sc NMR parameters have been obtained for Sc2O3, ScVO4, ScNbO4 and ScTaO4. On the basis of 45Sc NMR and data available from literature, the ranges of the 45Sc chemical shift have been established for ScO6 and ScO8. The gradual change of the 45Sc and 51V NMR parameters with x confirms the formation of solid solutions in the process of synthesis of VNb9(1-x)Ta9xO25 and ScNb(1-x)TaxO4, in contrast to ScNb2(1-x)Ta2xVO9. The cation sublattice of ScNb(1-x)TaxO4 is found to be in octahedral coordination. The V sites in VNb9(1-x)Ta9xO25 are present in the form of slightly distorted tetrahedra. The 93Nb NMR parameters have been obtained for VNb9O25. Copyright © 2007 John Wiley & Sons, Ltd.
Received: 1 May 2007; Revised: 22 June 2007; Accepted: 20 August 2007

Digital Object Identifier (DOI) - 10.1002/mrc.2086

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Magnetic Resonance in Chemistry
Volume 46, Issue 1 , Pages 9 - 16
Published Online: 26 Nov 2007

Research Article
Critical behavior of KDCO3 from 2H and 39K single crystal NMR
Christophe Odin *
*Correspondence to Christophe Odin, Groupe Matière Condensée et Matériaux, UMR6626 au CNRS, Université Rennes I, Campus de Beaulieu, 35042 Rennes Cedex, France.

Keywords
NMR • solid-state NMR • phase transition • critical behavior • hydrogenocarbonate • deuterium NMR

Abstract
Potassium hydrogenocarbonate KDCO3 presents an order/disorder phase transition at Tc 353 K. The critical behavior of this phase transition was studied by single crystal 2H and 39K NMR. The evolution of the order parameter as a function of temperature is quantified, and the critical exponent was determined, indicating a transition close to a tricritical point. The 2H Zeeman relaxation rate is strongly increased near the transition temperature. By calculating the noncritical contribution to the Zeeman relaxation rate, we show that the observed relaxation rate clearly presents a pseudo-divergent behavior near Tc, with a logarithmic singularity. The nature of the phase transition is discussed in the light of these results. Copyright © 2007 John Wiley & Sons, Ltd.
Received: 31 May 2007; Revised: 30 August 2007; Accepted: 18 September 2007

Digital Object Identifier (DOI) - 10.1002/mrc.2112

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Magnetic Resonance in Chemistry
Volume 46, Issue 1 , Pages 30 - 35
Published Online: 20 Dec 2007

Research Article
Inverse H-C ex situ HRMAS NMR experiments for solid-phase peptide synthesis
Timothy R. Ramadhar, Fernando Amador, Michael J. T. Ditty, William P. Power
*Correspondence to William P. Power, Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada, N2L 3G1.

Keywords
NMR • 1H • 13C • heteronuclear shift correlation • inverse experiments • gel-phase HRMAS • BIRD-HMQC • CT-HMBC-1 • solid-phase peptide synthesis

Abstract
The growing importance of solid-phase peptide synthesis (SPPS) has necessitated the development of spectroscopic experiments that can be used to obtain structural and conformational information on resin-bound peptides. Despite the utility of two-dimensional high-resolution magic angle spinning (HRMAS) NMR experiments that provide homonuclear shift correlations, experiments that provide heteronuclear shift correlations are necessary for complex conformational and structural elucidatory problems. Here we report the optimization and implementation of non-gradient inverse NMR experiments for acquiring the 1H13C shift correlations of resin-bound peptides. The use of non-gradient experiments is advantageous as many magic angle spinning (MAS) probes do not possess gradient coils. An HRMAS BIRD-HMQC experiment with a reduced 1JCH constant has proven very suitable for obtaining one-bond correlations. Long-range correlations can be interpolated by using a non-gradient HRMAS CT-HMBC-1 experiment where the resulting data is processed with forward linear prediction. It has been shown that removing the effects of 1H1H J-modulation is crucial in order to view cross peaks that correspond to long-range correlations. Additionally, both experiments prove extremely useful over routine one-dimensional 13C HRMAS experiments for extracting carbon chemical shift data. The non-gradient HRMAS BIRD-HMQC and CT-HMBC-1 experiments can be used to assist in conformational analysis and to identify and deconvolute situations where accidental equivalence and seemingly correlated isochronous signals arise.
Received: 23 August 2007; Revised: 21 September 2007; Accepted: 25 September 2007

Progress in NMR - Up to Volume 52, Issue 1 pp. 1-68 (30 January 2008)

Progress in NMR - Up to Volume 52, Issue 1 pp. 1-68 (30 January 2008)

Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 52, Issue 1, 30 January 2008, Pages 22-30

doi:10.1016/j.pnmrs.2007.07.003

Hyperdimensional NMR spectroscopy

Eriks Kupc and Ray Freeman
Received 20 July 2007; accepted 30 July 2007. Available online 6 August 2007.

Keywords: N-dimensional NMR; Projection-reconstruction; Hyperdimensional spectra; Agitoxin; Peptide

Solid-state NMR, up to Volume 32, Issue 4, Pages 99-136 (December 2007)

Solid-state NMR, up to Volume 32, Issue 4, Pages 99-136 (December 2007)

Solid State Nuclear Magnetic Resonance
Volume 32, Issue 4, December 2007, Pages 99-108

doi:10.1016/j.ssnmr.2007.09.003
A practical comparison of MQMAS techniques

Johanna Kanellopoulos, Dieter Freude, and Arno Kentgens
Received 30 August 2007. Available online 5 October 2007.

Abstract

A systematic experimental evaluation of several approaches to multiple-quantum MAS NMR was performed for spin-5/2 nuclei using 27Al NMR of the aluminosilicate andalusite and the porous aluminum phosphate AlPO4-14 as model. Experiments were conducted in the fields of 9.4 and 17.6 T using magic-angle spinning frequencies up to 30 kHz and rf-field strengths of 250 and 120 kHz. Numerical SIMPSON optimizations of the NMR parameters were performed alongside the experimental evaluations. Both theory and experiment show that the optimization is most critical for the species in the sample that have the largest quadrupolar coupling constant. For 5QMAS experiments it could be confirmed that the highest available rf-field strength and rotation frequency are favorable for the efficiency of the experiments. For 3QMAS experiments of sites with moderate quadrupolar coupling constants optimum results were obtained at less stringent conditions. The comparison of a FAM II-modification and DFS gave the expected improvement by a factor of about two with respect to a rectangular pulse. No significant difference between these techniques concerning the signal-to-noise ratios was obtained. An actual improvement of the isotropic resolution by a factor of about two was obtained going from 3QMAS to 5QMAS. In addition the resolution of the spectra increases by a factor of about two going from 9.4 to 17.6 T.

Keywords: Multiple-quantum; MQMAS NMR; Quadrupolar nuclei; 27Al

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Solid State Nuclear Magnetic Resonance
Volume 32, Issue 4, December 2007, Pages 109-117

doi:10.1016/j.ssnmr.2007.10.002
A multiple-field 23Na NMR study of sodium species in porous carbons

Jair C.C. Freitas, Miguel A. Schettino Jr., Francisco G. Emmerich, Alan Wong and Mark E. Smith

Abstract

The sodium environments in porous carbon materials prepared from NaOH activation of a char were investigated by means of multiple-field solid-state 23Na NMR measurements, carried out at magnetic fields of 4.7, 8.45 and 14.1 T, with single-pulse excitation and magic angle spinning (MAS). The recorded spectra showed a relatively featureless resonance with linewidth and peak shift strongly dependent on the magnetic field strength and on the hydration level of the samples. The existence of second-order quadrupolar effects was inferred, although the structural disorder and the mobile character associated with the Na environment precluded the direct observation of typical quadrupolar features in the MAS NMR spectra. The analysis of the spectra collected at multiple magnetic fields yielded the values of -2.8 ppm for the isotropic chemical shift and 1.8 MHz for the quadrupole coupling constant, which were interpreted as due to Na+ ions bonded to oxygenated groups at the edges of the graphene planes within the carbon pore network.

Keywords: Activated carbon; Nuclear magnetic resonance; Chemical structure; 23Na NMR; Multiple magnetic fields

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Solid State Nuclear Magnetic Resonance
Volume 32, Issue 3, November 2007, Pages 78-88

doi:10.1016/j.ssnmr.2007.09.001

New inserts and low temperature—Two strategies to overcome the bottleneck in MAS NMR on wet gels

R. König, G.and E. Kemnitz
Received 7 June 2007; revised 1 August 2007. Available online 25 September 2007.

Abstract

MAS NMR experiments on wet and dry aluminium alkoxide fluoride gels are presented here for the first time. For the MAS studies on wet jelly like gels special inserts were developed which fit perfectly a 4 mm rotor and allow rotation frequencies up to 12 kHz. Six different insert materials were tested concerning their suitability including different organic polymers ((poly(methyl methacrylate) (PMMA), poly(ether ether ketone) (PEEK), poly(vinylchloride) (PVC) and poly(tetrafluorethylene) (PTFE)), glass as well as pure quartz (SiO2). Alternatively, low-temperature MAS NMR experiments taken at 150 K with the wet gel frozen directly in the rotor led to comparable results.27Al, 19F, 13C, 1H were used as nuclear spin probes to identify local structures in the wet as well as in the dry xerogels. Both wet and dry gels consist of a network structure of AlF6-xOiPrx species (x: 0–3). The main structural units of the dried gel are already preformed in the jelly like gel and change only little at aging and drying processes.

Keywords: MAS NMR; Wet fluoride gels; Inserts; Low temperature

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Solid State Nuclear Magnetic Resonance
Volume 32, Issue 3, November 2007, Pages 89-98

doi:10.1016/j.ssnmr.2007.09.002
Site discrimination in the crystalline borophosphate Na5B2P3O13 using advanced solid-state NMR techniques

Wenzel Strojek, Constanze Miriam Fehse, Hellmut Eckert, Bastian Ewald and Rüdiger Kniep
Received 20 August 2007. Available online 28 September 2007.

Abstract

A comprehensive solid-state NMR investigation on crystalline Na5B2P3O13 is presented. Triple-quantum magic angle spinning (TQMAS) and rotational echo double resonance (REDOR) studies are used for accurate determinations of the 11B, 23Na and 31P interaction parameters. Based on these results and complementary quantum mechnical calculations, plausible site assignments can be derived. Generally, the results show that detailed, quantitative information about structures in borophosphate compunds can be obtained by investigating both the local site environments characterized by chemical shift and quadrupolar interaction parameters and the correlated dipolar interactions to atoms in the second coordination sphere.

Keywords: Dipolar coupling; Rotational echo double resonance; Borophosphates

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Solid State Nuclear Magnetic Resonance
Volume 32, Issue 2, October 2007, Pages 34-43

doi:10.1016/j.ssnmr.2007.07.001
93Nb and 17O NMR chemical shifts of niobiophosphate compounds

A. Flambard, L. Montagne, L. Delevoye and S. Steuernagel
Received 13 April 2007. Available online 10 July 2007.

Abstract

Niobiophosphate compounds with a large range of niobium and oxygen environments were studied with 93Nb and 17O solid-state NMR. 93Nb isotropic chemical shift of pure niobate Nb(ONb)6, pure phosphate Nb(OP)6 and mixed phosphate–niobate Nb(OP)x(ONb)(6-x) (1less-than-or-equals, slantxless-than-or-equals, slant5) sites were measured at a high magnetic field (18.8 T). 93Nb chemical shifts were found to be sensitive to the variation of local charge on Nb, but not to the local bond geometry (i.e. crystallographic site and edge or corner connectivity). A systematic shift to high field of the 93Nb chemical shift is measured when x increases. Then, 17O NMR spectra of a series of enriched samples provided the chemical shift and quadrupolar parameters for 4 types of oxygen environment (P–O–P, P–O–Na, P–O–Nb and Nb–O–Nb). Finally, Nb–O–Nb sites were characterized by a large 17O chemical shift anisotropy.

Keywords: 93Nb NMR; 17O NMR; Phosphate; Niobate; Niobiophosphate

Wednesday, January 09, 2008

Hiyam's Journal Update

Phys. Rev. B 76, 245209 (2007)
1H NMR electron-nuclear cross relaxation in thin films of hydrogenated amorphous silicon
Tining Su and P. C. Taylor, G. Ganguly and D. E. Carlson, D. C. Bobela, P. Hari

Abstract:
We investigate the spin-lattice relaxation of the dipolar order in 1H NMR in hydrogenated amorphous silicon (a-Si:H). We find that the relaxation is dominated by the cross relaxation between the hydrogen nuclei and the paramagnetic states. The relaxation is inhomogeneous, and can be described as a stretched exponential function. We proposed a possible mechanism for this relaxation. This mechanism applies to a rather broad range of paramagnetic states, including the deep neutral defects (dangling bonds), the light-induced metastable defects, the defects created by doping, and the singly occupied, localized band-tail states populated by light at low temperatures. The cross relaxation is only sensitive to the bulk spin density, and the surface spins have a negligible effect on the relaxation.

Phys. Rev. B 76, 172101 (2007)
1H and 31P nuclear magnetic resonance study of proton-irradiated KH2PO4
Se-Hun Kim,1,2 Kyu Won Lee,1 B. H. Oh,1 Cheol Eui Lee,1 and K. S. Hong3

Abstract:
We have studied the microscopic structure and dynamics in a proton-irradiated KH2PO4 single crystal. Our 1H and 31P nuclear magnetic resonance measurements indicate that proton irradiation gives rise to a decrease in the local dipolar order of the rigid lattice protons and an increase in interstitial protons as well as structural distortion of the PO4 tetrahedra.

Monday, January 07, 2008

Hiyam's Journal Update

Chem. Mater., 20 (1), 287–293 10.1021/cm071822z Web Release Date: December 6, 2007 Copyright © 2008 American Chemical Society
Nanoheterogeneity of a Polymer Blend and the Effect of Humidity as Characterized by Solid-State NMR
Stuart A. Brewer,*† David C. Apperley,‡ and Corinne A. Stone†

Abstract:
A material that potentially displays both breathability and chemical barrier properties has been the center of this study. This material is based on a hydrogel formed between polyvinyl alcohol, polyethyleneimine, and water. An important aspect of this study has been a need to obtain a greater understanding of the solid-state structure adopted by the material. Consequently, a detailed investigation of the polymer blend was conducted by solid-state NMR. A combination of high-resolution carbon-13 cross-polarization and fast-recycle direct-polarization experiments, together with 1H wide-line measurements, has yielded a wealth of information on the domain structure of the material and the characteristics of those domains. The effects of environmental humidity on the polymer blend have also been studied.

Chem. Mater., 20 (1), 294–302 10.1021/cm0716598 Web Release Date: December 5, 2007 Copyright © 2008 American Chemical Society
Solid-State NMR Study of the Role of H and Na in AB-Type Carbonate Hydroxylapatite
Harris E. Mason,*†‡ Andrew Kozlowski,†§ and Brian L. Phillips†‡

Abstract:
Solid-state nuclear magnetic resonance (NMR) techniques, combined with Fourier transform infrared (FT-IR) spectroscopy, were used to study synthetic AB-type carbonate hydroxylapatite (CHAp). 13C{1H} heteronuclear correlation (HetCor) experiments indicate that the two carbonate environments represented by the peaks at δC = 169.8 and 170.8 ppm are associated with three H environments with one environment represented by a peak centered about δH = 0.0 ppm and two additional peaks located at 1.3 and 5.5 ppm. The peaks near δH = 0.0 ppm correspond to hydroxyl environments within the channels of the CHAp, whereas those at 1.3 and 5.5 exhibit spectral characteristics consistent with bicarbonate ions that donate moderate to weak hydrogen bonds. Possible methods by which bicarbonate incorporation can be accommodated by the apatite structure are discussed. The Na/carbonate ratio and 23Na NMR spectroscopy indicate that Na plays an important role in the carbonate incorporation in these materials.

Solid-State NMR Literature Blog

Thursday, January 17, 2008

Bryan's Literature Update Through January 17, 2008

Hiyam's Journal Update

Wednesday, January 16, 2008

Hiyam's Journal Update

Monday, January 14, 2008

Chem. Rev. - Chemical reviews, up to Jan. 2008

ACR - Accounts of Chemical Research - up to Dec. 2007, vol. 40, iss 12.

CMR - Concepts in Magnetic Resonance - up to Volume 30A Issue 6 - November 2007 (309-393)

JMR - Journal of Magnetic Resonance - up to January 2008

JMR - Journal of Magnetic Resonance - up to January 2008

MRC Special Issue - Volume 45 Issue S1 , Pages 1 - 260 (December 2007) - Special Issue: New techniques in solid-state NMR

MRC - Magnetic Resonance in Chemistry - up to Jan. 2008

Progress in NMR - Up to Volume 52, Issue 1 pp. 1-68 (30 January 2008)

Solid-state NMR, up to Volume 32, Issue 4, Pages 99-136 (December 2007)

Wednesday, January 09, 2008

Hiyam's Journal Update

Monday, January 07, 2008

Hiyam's Journal Update

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