J. Am. Chem. Soc., 130 (5), 1741 -1748, 2008.

Transient States in [2 + 2] Photodimerization of Cinnamic Acid: Correlation of Solid-State NMR and X-ray Analysis
Mujeeb Khan, Gunther Brunklaus, Volker Enkelmann, and Hans-Wolfgang Spiess

Abstract:
13C-CPMAS and other solid-state NMR methods have been applied to monitor the solid-state reactions of trans-cinnamic acid derivatives, which are the pioneer and model compounds in the field of topochemistry previously studied by X-ray diffraction, AFM, and vibrational spectroscopy. Single-crystal X-ray analyses of photoirradiated -trans-cinnamic acid where the monomers are arranged in a head-to-tail manner have revealed the formation of a centrosymmetric -truxillic acid photodimer. For a centrosymmetric dimer, however, two cyclobutane carbon signals and one carbonyl carbon signal were expected apart from other aromatic carbon signals. Instead, four cyclobutane and two carbonyl carbon signals were observed suggesting the formation of a non-centrosymmetric photodimer. Removing hydrogen bonds from the system by esterfication of -truxillic acid yield a centrosymmetric photodimer. Careful analysis of the obtained products via solid-state NMR clearly showed that the observed peak splittings in the 13C-CPMAS spectra did not originate from packing effects but rather result from asymmetric hydrogen bonds distorting the local symmetry. Further evidence of this rather dynamic hydrogen-bonding stems from high-temperature X-ray data revealing that only the joint approach of both X-ray analysis and solid-state NMR at similar temperatures allows for the successful characterization of dynamic processes occurring in topochemical reactions, thus, providing detailed insight into the reaction mechanism of organic solid-state transformations.

JMR, February 2008

Literature review, January 28, 2008 - JMR up to February 2008
33S NMR (Jakobsen)
17O NMR (Asakura)

Journal of Magnetic Resonance
Vol: 190, Issue: 2, February, 2008
pp. 316-326

Title: Sensitivity enhancement in natural-abundance solid-state ^3^3S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions
Authors: Hansen, M.R.; Brorson, M.; Bildsoe, H.; Skibsted, J.; Jakobsen, H.J.
Keywords: 33S MAS NMR; Sensitivity enhancement; WURST and hyperbolic secant inversion pulses; Population transfer; Inorganic sulfates; Tetrathiometallates

Abstract (English): The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state ^3^3S (spin I=3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH4)2WS4 and (NH4)2MoS4. These materials all exhibit ^3^3S quadrupole coupling constants (CQ) in the range 0.1-1.0MHz, with precise CQ values being determined from analysis of the PT enhanced ^3^3S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I=3/2 nuclei with similar CQ values (0.3-1.2MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance ^3^3S MAS NMR, a time saving which is extremely welcome for this important low-g nucleus.
# Item Identifier: S1090-7807(07)00354-0
Publication Type: Article ISSN: 1090-7807

—

Journal of Magnetic Resonance
Vol: 190, Issue: 2, February, 2008
pp. 327-332

Title: High field 17O solid-state NMR study of alanine tripeptides
Authors: Yamauchi, K.; Okonogi, M.; Kurosu, H.; Tansho, M.; Shimizu, T.; Gullion, T.; Asakura, T.
Keywords: Anti-parallel b-sheet; Parallel b-sheet; ^1^7O chemical shift; Ala-Ala-Ala; DFT
Abstract (English): 17O chemical shifts of Ala-Ala-Ala, with parallel and anti-parallel b-sheet structures, are observed using a 930-MHz high-resolution solid-state NMR spectrometer. Ala-Ala-Ala serves as a model sheet-forming peptide because it can be easily prepared as either a parallel or an anti-parallel b-sheet structure. Spectral differences between the two samples are observed which arise from molecular packing differences between the two sheet structures. DFT chemical shift calculations are performed for the two samples, and the calculated spectra are in good agreement with the experimental spectra. The DFT calculations provide insight into the nature of the chemical shift differences observed between the two sheet structures.
# Item Identifier: S1090-7807(07)00346-1
Publication Type: Miscellaneous ISSN: 1090-7807

Hiyam's Journal Update

J. Am. Chem. Soc., 130 (4), 1236 -1244, 2008. 10.1021/ja075584k S0002-7863(07)05584-9 Web Release Date: January 5, 2008 Copyright © 2008 American Chemical Society
Solid-State NMR Spectroscopy Detects Interactions between Tryptophan Residues of the E. coli Sugar Transporter GalP and the -Anomer of the D-Glucose Substrate
Simon G. Patching, Peter J. F. Henderson

Abstract:
An experimental approach is described in which high resolution 13C solid-state NMR (SSNMR) spectroscopy has been used to detect interactions between specific residues of membrane-embedded transport proteins and weakly binding noncovalent ligands. This procedure has provided insight into the binding site for the substrate D-glucose in the Escherichia coli sugar transport protein GalP. Cross-polarization magic-angle spinning (CP-MAS) SSNMR spectra of GalP in its natural membrane at 4 C indicated that the - and -anomers of D-[1-13C]glucose were bound by GalP with equal affinity and underwent fast exchange between the free and bound environments. Further experiments confirmed that by lowering the measurement temperature to -10 C, peaks could be detected selectively from the substrate when restrained within the binding site. Dipolar-assisted rotational resonance (DARR) SSNMR experiments at -10 C showed a selective interaction between the -anomer of D-[1-13C]glucose and 13C-labels within [13C]tryptophan-labeled GalP, which places the carbon atom at C-1 in the -anomer of D-glucose to within 6 Å of the carbonyl carbon of one or more tryptophan residues in the protein. No interaction was detected for the -isomer. The role of tryptophan residues in substrate binding was investigated further in CP-MAS experiments to detect D-[1-13C]glucose binding to the GalP mutants W371F and W395F before and after the addition of the inhibitor forskolin. The results suggest that both mutants bind D-glucose with similar affinities, but have different affinities for forskolin. This work highlights a useful general experimental strategy for probing the binding sites of membrane proteins, using methodology which overcomes the problems associated with the unfavorable dynamics of weak ligands.

J. Am. Chem. Soc., 130 (4), 1264 -1273, 2008. 10.1021/ja0759949 S0002-7863(07)05994-X Web Release Date: January 4, 2008 Copyright © 2008 American Chemical Society
NMR Investigations of the Static and Dynamic Structures of Bisphosphonates on Human Bone: a Molecular Model
Sujoy Mukherjee, Yongcheng Song, and Eric Oldfield*

Abstract:
We report the results of an investigation of the binding of a series of bisphosphonate drugs to human bone using 2H, 13C, 15N, and 31P nuclear magnetic resonance spectroscopy. The 31P NMR results show that the bisphosphonate groups bind irrotationally to bone, displacing orthophosphate from the bone mineral matrix. Binding of pamidronate is well described by a Langmuir-like isotherm, from which we deduce an ~30-38 Å2 surface area per pamidronate molecule and a G = -4.3 kcal mol-1. TEDOR of [13C3, 15N] pamidronate on bone shows that the bisphosphonate binds in a gauche [N-C(1)] conformation. The results of 31P as well as 15N shift and cross-polarization measurements indicate that risedronate binds weakly, since it has a primarily neutral pyridine side chain, whereas zoledronate (with an imidazole ring) binds more strongly, since the ring is partially protonated. The results of 2H NMR measurements of side-chain 2H-labeled pamidronate, alendronate, zoledronate, and risedronate on bone show that all side chains undergo fast but restricted motions. In pamidronate, the motion is well simulated by a gauche+/gauche- hopping motion of the terminal -CH2-NH3+ group, due to jumps from one anionic surface group to another. The results of double-cross polarization experiments indicate that the NH3+-terminus of pamidronate is close to the bone mineral surface, and a detailed model is proposed in which the gauche side-chain hops between two bone PO43- sites.

Joel's Journal Updates

Synthesis, Characterization, and Catalytic Activity of a Well-Defined Rhodium Siloxide Complex Immobilized on Silica
Bogdan Marciniec, Karol Szubert, Marek J. Potrzebowski, Ireneusz Kownacki, Kinga Leszczak
Angwandte (2007)47, 541.

Summary:
Rhodium siloxide surface complex 2, which was obtained directly by reaction of molecular precursor 1 with aerosil silica and characterized inter alia by solid-state NMR spectroscopy, is a highly active and stable catalyst for hydrosilylation reactions.

NMR Spectroscopy: Pushing the Limits of Sensitivity
Hans Wolfgang Spiess
Angwandte (2007)47, 639.

Summary:
Impressively sensitive: To meet the challenges of miniaturization and limited sample quantity, new approaches for substantially increasing the sensitivity of NMR spectroscopy for gases, liquids, and solids have been developed (for two examples, see picture). These and future developments will assure that NMR spectroscopy remains a major tool for chemistry and other fields for years to come.

Li6PS5X: A Class of Crystalline Li-Rich Solids With an Unusually High Li+ Mobility
Hans-Jörg Deiseroth, Shiao-Tong Kong, Hellmut Eckert, Julia Vannahme, Christof Reiner, Torsten Zaiß, Marc Schlosser
Angwandte (2007)47, 755.

Summary:
Mobile metal ions: Halide-substituted lithium argyrodites form a new class of Li-rich solids with an unusually high Li mobility. Single-crystal X-ray studies (see picture; Li black, S yellow, I red) at room temperature and MAS-NMR measurements in a wide temperature range provide insights into the Li+ ion dynamics.

The dynamics and orientation of a lipophilic drug within model membranes determined by 13C solid-state NMR
Martin P. Boland and David A. Middleton
PCCP(2008)10,178.

Abstract:
Methods for determining how a drug interacts with cellular membranes at the molecular level can give valuable insight into the mode of action of the drug and its absorption, distribution and metabolism profile. A procedure is described here to determine the orientation and location of the lipophilic drug trifluoperazine (TFP) intercalated into dimyristoylphosphatidylcholine (DMPC) bilayers, by using a novel combination of high-resolution solid-state nuclear magnetic resonance (SSNMR) methods to observe signals from 13C within the drug at natural abundance. SSNMR measurements of 1H–13C dipolar couplings for TFP and selective broadening of 13C NMR peaks by paramagnetic Mn2+ together suggest a model for the location, orientation and dynamics of the drug within lipid bilayers that offers an explanation for the lysoprotective effect of the drug at low concentrations. The experiments described are straightforward to implement and can be used for the routine analysis of drug–membrane interactions to provide useful information for drug design and structure refinement.

Isotropic chemical shifts in magic-angle spinning NMR spectra of proteins
Benjamin J. Wylie, Lindsay J. Sperling and Chad M. Rienstra
PCCP(2008)10,405.

Abstract:
Here we examine the effect of magic-angle spinning (MAS) rate upon lineshape and observed peak position for backbone carbonyl (C) peaks in NMR spectra of uniformly-13C,15N-labeled (U–13C,15N) solid proteins. 2D N–C spectra of U–13C,15N microcrystalline protein GB1 were acquired at six MAS rates, and the site-resolved C lineshapes were analyzed by numerical simulations and comparison to spectra from a sparsely labeled sample (derived from 1,3-13C–glycerol). Spectra of the U–13C,15N sample demonstrate large variations in the signal-to-noise ratio and peak positions, which are absent in spectra of the sparsely labeled sample, in which most 13C sites do not possess a directly bonded 13CA. These effects therefore are a consequence of rotational resonance, which is a well-known phenomenon. Yet the magnitude of this effect pertaining to chemical shift assignment has not previously been examined. To quantify these effects in high-resolution protein spectra, we performed exact numerical two- and four-spin simulations of the C lineshapes, which reproduced the experimentally observed features. Observed peak positions differ from the isotropic shift by up to 1.0 ppm, even for MAS rates relatively far (a few ppm) from rotational resonance. Although under these circumstances the correct isotropic chemical shift values may be determined through simulation, systematic errors are minimized when the MAS rate is equivalent to 85 ppm for 13C. This moderate MAS condition simplifies spectral assignment and enables data sets from different labeling patterns and spinning rates to be used most efficiently for structure determination.

Molybdenum magnetic shielding and quadrupolar tensors for a series of molybdate salts: a solid-state 95Mo NMR study
Michelle A. M. Forgeron and Roderick E. Wasylishen
PCCP(2008)10,574.

Abstract:
A series of molybdate, MoO42–, salts have been studied using solid-state 95Mo NMR spectroscopy at applied magnetic field strengths of 11.75, 17.63 and 21.14 T. In contrast to previous investigations, the principal components of the Mo shielding and EFG tensors have been obtained, as well as their relative orientations. At the fields employed, the anisotropic Mo shielding and quadrupolar interactions make significant contributions to the observed 95Mo central transition NMR lineshapes. Based on available structural data, the extent of distortion of the MoO42– anion from Td symmetry is reflected in the observed 95Mo nuclear quadrupolar coupling constants for the molybdate salts with divalent cations (i.e., Ca2+, Sr2+, Cd2+, Ba2+, Pb2+), but no correlation is found for molybdate salts containing the monovalent alkali metal (Li+, K+, Rb+, Cs+) cations.


Probing the surface structure of hydroxyapatite using NMR spectroscopy and first principles calculations
Helen Chappell, Melinda Duer, Nicholas Groom, Chris Pickard and Paul Bristowe
PCCP(2008)10,600.

Abstract:
The surface characteristics of hydroxyapatite (HA) are probed using a combination of NMR spectroscopy and first principles calculations. The NMR spectrum is taken from a bone sample and the first principles calculations are performed using a plane-wave density functional approach within the pseudopotential approximation. The computational work focuses on the (100) and (200) surfaces, which exhibit a representative range of phosphate, hydroxyl and cation bonding geometries. The shielding tensors for the 31P, 1H and 17O nuclei are calculated from the relaxed surface structures using an extension of the projector augmented-wave method. The calculated 31P chemical shifts for the surface slab are found to be significantly different from the bulk crystal and are consistent with the NMR data from bone and also synthetically prepared nanocrystalline samples of HA. Rotational relaxations of the surface phosphate ions and the sub-surface displacement of other nearby ions are identified as causing the main differences. The investigation points to further calculations of other crystallographic surfaces and highlights the potential of using NMR with ab initio modelling to fully describe the surface structure and chemistry of HA, which is essential for understanding its reactivity with the surrounding organic matrix.

Hiyam's Journal Update

J. Am. Chem. Soc., ASAP Article 10.1021/ja0759949 S0002-7863(07)05994-X Web Release Date: January 4, 2008 Copyright © 2008 American Chemical Society
NMR Investigations of the Static and Dynamic Structures of Bisphosphonates on Human Bone: a Molecular Model
Sujoy Mukherjee, Yongcheng Song, and Eric Oldfield*

Abstract:
We report the results of an investigation of the binding of a series of bisphosphonate drugs to human bone using 2H, 13C, 15N, and 31P nuclear magnetic resonance spectroscopy. The 31P NMR results show that the bisphosphonate groups bind irrotationally to bone, displacing orthophosphate from the bone mineral matrix. Binding of pamidronate is well described by a Langmuir-like isotherm, from which we deduce an ~30-38 Å2 surface area per pamidronate molecule and a G = -4.3 kcal mol-1. TEDOR of [13C3, 15N] pamidronate on bone shows that the bisphosphonate binds in a gauche [N-C(1)] conformation. The results of 31P as well as 15N shift and cross-polarization measurements indicate that risedronate binds weakly, since it has a primarily neutral pyridine side chain, whereas zoledronate (with an imidazole ring) binds more strongly, since the ring is partially protonated. The results of 2H NMR measurements of side-chain 2H-labeled pamidronate, alendronate, zoledronate, and risedronate on bone show that all side chains undergo fast but restricted motions. In pamidronate, the motion is well simulated by a gauche+/gauche- hopping motion of the terminal -CH2-NH3+ group, due to jumps from one anionic surface group to another. The results of double-cross polarization experiments indicate that the NH3+-terminus of pamidronate is close to the bone mineral surface, and a detailed model is proposed in which the gauche side-chain hops between two bone PO43- sites.


J. Am. Chem. Soc.,

Local Environments and Lithium Adsorption on the Iron Oxyhydroxides Lepidocrocite
(-FeOOH) and Goethite (-FeOOH): A 2H and 7Li Solid-State MAS NMR Study
Jongsik Kim, Ulla Gro Nielsen, and Clare P. Grey*

Abstract:
2H and 7Li MAS NMR spectroscopy techniques were applied to study the local surface and bulk environments of iron oxyhydroxide lepidocrocite (-FeOOH). 2H variable-temperature (VT) MAS NMR experiments were performed, showing the presence of short-range, strong antiferromagnetic correlations, even at temperatures above the Néel temperature, TN, 77 K. The formation of a Li+ inner-sphere complex on the surface of lepidocrocite was confirmed by the observation of a signal with a large 7Li hyperfine shift in the 7Li MAS NMR spectrum. The effect of pH and relative humidity (RH) on the concentrations of Li+ inner- and outer-sphere complexes was then explored, the concentration of the inner sphere complex increasing rapidly above the point of zero charge and with decreasing RH. Possible local environments of the adsorbed Li+ were identified by comparison with other layer-structured iron oxides such as -LiFeO2 and o-LiFeO2. Li+ positions of Li+-sorbed and exchanged goethite were reanalyzed on the basis of the correlations between Li hyperfine shifts and Li local structures, and two different binding sites were proposed, the second binding site only becoming available at higher pH.

J. Am. Chem. Soc., 130 (1), 288 -299, 2008.

Tuning the Structural and Physical Properties of Cr2Ti3Se8 by Lithium Intercalation: A Study of the Magnetic Properties, Investigation of Ion Mobility with NMR Spectroscopy and Electronic Band Structure Calculations
Joseph Wontcheu, Wolfgang Bensch,* Martin Wilkening, Paul Heitjans, Sylvio Indris, Paul Sideris, Clare P. Grey, Sergiy Mankovsky, and Hubert Ebert

Abstract:
The room temperature intercalation of Cr2Ti3Se8 with butyl lithium yields a phase mixture of the starting material and of the new trigonal phase with composition Li0.4Cr0.5Ti0.75Se2. The phase pure fully intercalated trigonal phase is obtained at elevated temperature (80 C) with the final composition Li0.62Cr0.5Ti0.75Se2. The line profile analysis (LPA) of the powder patterns shows that pronounced strain occurs in the intercalated material. The deintercalation of the material is realized by treatment of the fully intercalated sample with distilled water leading to the composition Li0.15Cr0.5Ti0.75Se2. The intercalation is accompanied by an electron transfer from the guest Li to the host material, and as a consequence significant changes of the interatomic distances are observed. The local environment and the dynamics of the Li+ ions in the fully intercalated sample were studied with 7Li magic angle spinning (MAS) NMR investigations. These reveal different environments of transition metal neighbors for the Li sites and a high mobility of the Li ions. Magnetic measurements show that in the pristine material antiferromagnetic interactions are dominating ( = -113.5 K) with no long-range order at low temperatures. The magnetic ground state is characterized by a spin-glass behavior. With increasing Li content the antiferromagnetic character vanishes progressively, and the fully intercalated phase exhibits a positive Weiss constant ( = 12 K) indicating dominating ferromagnetic exchange interactions; i.e., the magnetic properties can be significantly altered by lithiation. The interpretation of our experimental findings is supported by the results of accompanying band structure calculations done within the framework of local spin density functional theory. These demonstrate in particular the role of the charge transfer between the constituents as a function of the Li concentration and its impact on the exchange coupling.

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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Can. J. Chem. 85(7-8): 496–505 (2007) doi:10.1139/V07-069 © 2007 NRC Canada

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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Can. J. Chem. 85(10): 782–792 (2007) doi:10.1139/V07-085 © 2007 NRC Canada

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.

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.

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