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

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.

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.

Hiyam's Journal Update

Chem. Mater., 19 (25), 6277–6289 10.

Cation Ordering in Li[NixMnxCo(1–2x)]O2-Layered Cathode Materials: A Nuclear Magnetic Resonance (NMR), Pair Distribution Function, X-ray Absorption Spectroscopy, and Electrochemical Study
Dongli Zeng,† Jordi Cabana,† Julien Bréger,† Won-Sub Yoon,‡ and Clare P. Grey*†

Abstract:
Several members of the compositional series Li[NixMnxCo(1–2x)]O2 (0.01 ≤ x ≤ 1/3) were synthesized and characterized. X-ray diffraction results confirm the presence of the layered α-NaFeO2-type structure, while X-ray absorption near-edge spectroscopy experiments verify the presence of Ni2+, Mn4+, and Co3+. Their local environment and short-range ordering were investigated by using a combination of 6Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and neutron pair distribution function (PDF) analysis, associated with reverse Monte Carlo (RMC) calculations. The 6Li MAS NMR spectra of compounds with low Ni/Mn contents (x ≤ 0.10) show several well-resolved resonances, which start to merge when the amount of Ni and Mn increases, finally forming a broad resonance at high Ni/Mn contents. Analysis of the 6Li MAS NMR 6Li[Ni0.02Mn0.02Co0.96]O2 spectrum, is consistent with the formation of Ni2+ and Mn4+ clusters within the transition-metal layers, even at these low-doping levels. The oxidation state of Ni in this high Co content sample strongly depends upon the Li/transition metal ratio of the starting materials. Neutron PDF analysis of the highest Ni/Mn content sample Li[Ni1/3Mn1/3Co1/3]O2 shows a tendency for Ni cations to be close to Mn cations in the first coordination shell; however, the Co3+ ions are randomly distributed. Analysis of the intensity of the “LiCoO2” resonance, arising from Li surrounded by Co3+ in its first two cation coordination shells, for the whole series provides further evidence for a nonrandom distribution of the transition-metal cations. The presence of the insulator-to-metal transition seen in the electrochemical profiles of these materials upon charging correlates strongly with the concentration of the “LiCoO2” resonance.


Chem. Mater., 19 (25), 6088–6094
Characterization of the Phosphate Units in Rat Dentin by Solid-State NMR Spectroscopy
Yao-Hung Tseng,† Yi-Ling Tsai,† Tim W. T. Tsai,† John C. H. Chao,† Chun-Pin Lin,*‡ Shih-Hao Huang,‡ Chung-Yuan Mou,†§ and Jerry C. C. Chan*†

Abstract:
Dentin samples of the incisor taken from Wistar rats of different ages are studied. A series of physical techniques are used to characterize the samples, with particular emphasis on 31P solid-state nuclear magnetic resonance. The structure of incisor dentin in rats can be described as apatite crystallites embedded in an amorphous matrix. We find that 19% of the apatite crystallites contain hydroxyl groups, which are distributed near the surface of the crystallites. The internal region of the crystallites is deficient in hydroxyl groups. As rats mature with age, there are several changes in the chemical composition of the incisor dentin: (i) the water content and phosporous amount in the amorphous matrix decrease; (ii) the amount of the phosphorus species in the apatite crystallites remains the same; and (iii) the loss of phosphorus species is accompanied by approximately the same loss of the calcium content.


Chem. Mater,; 2007; 19(26) pp 6367-6369; (Communication)

First Principles Calculations of NMR Parameters in Biocompatible Materials Science: The Case Study of Calcium Phosphates, β- and γ-Ca(PO3)2. Combination with MAS-J ExperimentsFrédérique Pourpoint, Adi Kolassiba, Christel Gervais, Thierry Azaïs, Laure Bonhomme-Coury, Christian Bonhomme, and Francesco Mauri

J. Am. Chem. Soc., 129 (49), 15164 -15173, 2007. 10.1021/ja0737117 S0002-7863(07)03711-0 Web

Paramagnetic NMR Relaxation in Polymeric Matrixes: Sensitivity Enhancement and Selective Suppression of Embedded Species (1H and 13C PSR Filter)
Eduardo Fernandez-Megia, Juan Correa, Ramon Novoa-Carballal, and Ricardo Riguera*

Abstract:
A study of the practical applications of the addition of paramagnetic spin relaxation (PSR) ions to a variety of polymers (PLL, PAA, PGA, PVP, and polysaccharides such as hyaluronic acid, chitosan, mannan, and dextran) in solution (D2O and DMSO-d6) is described. Use of GdIII, CuII, and MnII allows a reduction of up to 500% in the 1H longitudinal relaxation times (T1), and so in the time necessary for recording quantitative NMR spectra (sensitivity enhancement) neither an increase of the spectral line width nor chemical shift changes resulted from addition of any of the PSR agents tested. Selective suppression of the 1H and 13C NMR signals of certain components (low MW molecules and polymers) in the spectrum of a mixture was attained thanks to their different sensitivity [transverse relaxation times (T2)] to GdIII (PSR filter). Illustration of this strategy with block copolymers (PGA-g-PEG) and mixtures of polymers and low MW molecules (i.e., lactose-hyaluronic acid, dextran-PAA, PVP-glutamic acid) in 1D and 2D NMR experiments (COSY and HMQC) is presented. In those mixtures where PSR and CPMG filters alone failed in the suppression of certain components (i.e., PVP-mannan-hyaluronic acid) due to their similarity of 1H T2 values and sensitivities to GdIII, use of the PSR filter in combination with CPMG sequences (PSR-CPMG filter) successfully resulted in the sequential suppression of the components (hyaluronic acid first and then mannan).

J. Am. Chem. Soc., 129 (49), 15233 -15239, 2007.
Determination of Global Structure from Distance and Orientation Constraints in Biological Solids Using Solid-State NMR Spectroscopy
Loren B. Andreas, Anil K. Mehta,* and Manish A. Mehta*

Abstract:
We report the results from a new solid-state NMR experiment, DANTE-REDOR, which can determine global secondary structure in uniformly (13C,15N)-enriched systems by simultaneously measuring distance and orientation constraints. Following a heteronuclear spin-pair selection using a DANTE pulse train, the magnitude and orientation of the internuclear dipole vector, within the chemical shift anisotropy (CSA) frame of the observed nucleus, are determined by tracking the dephasing of individual spinning sidebands under magic angle spinning. The efficacy of the experiment is demonstrated by measuring the imidazole side-chain orientation in U-[13C6,15N3]-L-histidine·HCl·H2O

Joel's journal updates

Advances in Structural Analysis of Fluoroaluminates Using DFT Calculations of 27Al Electric Field Gradients
M. Body, C. Legein, J.-Y. Buzaré, G. Silly, P. Blaha, C. Martineau, and F. Calvayrac
JPCA(2007)111,11873.
Abstract:
Based on the analysis of 23 aluminum sites from 16 fluoroaluminates, the present work demonstrates the strong potential of combining accurate NMR quadrupolar parameter measurements, density functional theory (DFT)-based calculations of electric field gradients (EFG), and structure optimizations as implemented in the WIEN2k package for the structural and electronic characterizations of crystalline inorganic materials. Structure optimizations are essential for compounds whose structure was refined from usually less accurate powder diffraction data and provide a reliable assignment of the 27Al quadrupolar parameters to the aluminum sites in the studied compounds. The correlation between experimental and calculated EFG tensor elements leads to the proposition of a new value of the 27Al nuclear quadrupole moment Q(27Al) ) 1.616 ((0.024)  10-29 m2. The DFT calculations provide the orientation of the 27Al EFG tensors in the crystal frame. Electron density maps support that the magnitude and orientation of the 27Al EFG tensors in fluoroaluminates mainly result from the asymmetric distribution of the Al 3p orbital valence electrons. In most cases, the definition of relevant radial and angular distortion indices, relying on EFG orientation, allows correlations between these distortions and magnitude and sign of the Vii.

K-39 Quadrupolar and Chemical Shift Tensors for Organic Potassium Complexes and Diatomic Molecules
Philip K. Lee, Rebecca P. Chapman, Lei Zhang, Jiaxin Hu, Leonard J. Barbour, Elizabeth K. Elliott, George W. Gokel, and David L. Bryce
JPCA(2007)111,11859.
Abstract:
Solid-state potassium-39 NMR spectra of two potassium complexes of crown-ether-based organic ligands (1·KI and 2) have been acquired at 11.75 and 21.1 T and interpreted to provide information on the 39K quadrupolar and chemical shift tensors. The analyses reveal a large potassium chemical shift tensor span of 75 ± 20 ppm for 1·KI. This appears to be the first such measurement for potassium in an organic complex, thereby suggesting the utility of potassium chemical shift tensors for characterizing organic and biomolecular K+ binding environments. Compound 2 exhibits a cation- interaction between K+ and a phenyl group, and therefore, the 39K NMR tensors obtained for this compound must be partly representative of this interaction. Analyses of potassium-39 spin-rotation data for gaseous 39K19F and 39K35Cl available from molecular beam experiments performed by Cederberg and co-workers reveal the largest potassium CS tensor spans known to date, 84.39 and 141 ppm, respectively. Collectively, the results obtained highlight the potential of ultrahigh-field potassium-39 solid-state NMR spectroscopy and, in particular, the wide range of the anisotropy of the potassium CS tensor when organic and diatomic systems are considered.

Molecular Dynamics in Paramagnetic Materials as Studied by Magic-Angle Spinning 2H NMR Spectra
Motohiro Mizuno,* You Suzuki, Kazunaka Endo, Miwa Murakami, Masataka Tansho, and Tadashi Shimizu
JPCA(2007)111,12954.
Abstract:
A magic-angle spinning (MAS) 2H NMR experiment was applied to study the molecular motion in paramagnetic compounds. The temperature dependences of 2H MAS NMR spectra were measured for paramagnetic [M(H2O)6][SiF6] (M = Ni2+, Mn2+, Co2+) and diamagnetic [Zn(H2O)6][SiF6]. The paramagnetic compounds exhibited an asymmetric line shape in 2H MAS NMR spectra because of the electron-nuclear dipolar coupling. The drastic changes in the shape of spinning sideband patterns and in the line width of spinning sidebands due to the 180 flip of water molecules and the reorientation of [M(H2O)6]2+ about its C3 axis were observed. In the paramagnetic compounds, paramagnetic spin-spin relaxation and anisotropic g-factor result in additional linebroadening of each of the spinning sidebands. The spectral simulation of MAS 2H NMR, including the effects of paramagnetic shift and anisotropic spin-spin relaxation due to electron-nuclear dipolar coupling and anisotropic g-factor, was performed for several molecular motions. Information about molecular motions in the dynamic range of 102 s-1 k 108 s-1 can be obtained for the paramagnetic compounds from the analysis of 2H MAS NMR spectra when these paramagnetic effects are taken into account.

Carbon-13 Chemical Shift Tensors of Disaccharides: Measurement, Computation and Assignment
Limin Shao, Jonathan R. Yates, and Jeremy J. Titman*
JPCA(2007)111,13126.
Abstract:
A recently developed chemical shift anisotropy amplification solid-state nuclear magnetic resonance (NMR) experiment is applied to the measurement of the chemical shift tensors in three disaccharides: sucrose, maltose, and trehalose. The measured tensor principal values are compared with those calculated from first principles using density functional theory within the planewave-pseudopotential approach. In addition, a method of assigning poorly dispersed NMR spectra, based on comparing experimental and calculated shift anisotropies as well as isotropic shifts, is demonstrated.

Methanol Behviour in Direct Methanol Fuel Cells
Younkee Paik, Seong-Soo Kim, Oc Hee Han
Angwandte (2007)47, 94.
Summary:
Methanol crossover and reaction intermediates are studied in a direct methanol fuel cell (DMFC) by means of 2D and 13C MAS NMR spectroscopy. A membrane electrode assembly (MEA) composed of three polymer electrolyte membrane (PEM) layers is used in the DMFC, and the middle PEM film is extracted to perform the NMR measurements.

Theory and Computation of Nuclear Magnetic Resonance Parameters
J. Vaara
PCCP(2007)9,5399.
Abstract:
The art of quantum chemical electronic structure calculation has over the last 15 years reached a point where systematic computational studies of magnetic response properties have become a routine procedure for molecular systems. One of their most prominent areas of application are the spectral parameters of nuclear magnetic resonance (NMR) spectroscopy, due to the immense importance of this experimental method in many scientific disciplines. This article attempts to give an overview on the theory and state-of-the-art of the practical computations in the field, in terms of the size of systems that can be treated, the accuracy that can be expected, and the various factors that would influence the agreement of even the most accurate imaginable electronic structure calculation with experiment. These factors include relativistic effects, thermal effects, as well as solvation/environmental influences, where my group has been active. The dependence of the NMR spectra on external magnetic and optical fields is also briefly touched on.

Structural characterization of an anhydrous polymorph of paclitaxel by solid-state NMR
Elizabeth M. Heider, James K. Harper and David M. Grant
PCCP(2007)9,6083.
Abstract:
The three-dimensional structure of a unique polymorph of the anticancer drug paclitaxel (Taxol®) is established using solid state NMR (SSNMR) tensor (13C & 15N) and heteronuclear correlation (1H–13C) data. The polymorph has two molecules per asymmetric unit (Z = 2) and is thus the first conformational characterization with Z > 1 established solely by SSNMR. Experimental data are correlated with structure through a series of computational models that extensively sample all conformations. For each computational model, corresponding tensor values are computed to supply comparisons with experimental information which, in turn, establishes paclitaxels structure. Heteronuclear correlation data at thirteen key positions provide shift assignments to the asymmetric unit for each comparison. The two distinct molecules of the asymmetric unit possess nearly identical baccatin III moieties with matching conformations of the C10 acetyl moiety and, specifically, the torsion angle formed by C30–O–C10–C9. Additionally, both are found to exhibit an extended conformation of the phenylisoserine sidechain at C13 with notable differences in the dihedral angles centered around the rotation axes of O–C13, C2–C1 and C3–C2.

Microscopic Li self-diffusion parameters in the lithiated anode material Li4+xTi5O12 (0 x 3) measured by 7Li solid state NMR
Martin Wilkening, Wojciech Iwaniak, Jessica Heine, Viktor Epp, Alexandra Kleinert, Malte Behrens, Gerhard Nuspl, Wolfgang Bensch and Paul Heitjans
PCCP(2007)9,6199.
Abstract:
The microscopic Li diffusion parameters in the lithiated spinel Li4+xTi5O12, which is on its way to become a commercially used anode material in Li ion batteries, are probed for the first time via nuclear magnetic resonance spectroscopy.

A high-field solid-state 35/37Cl NMR and quantum chemical investigation of the chlorine quadrupolar and chemical shift tensors in amino acid hydrochlorides
Rebecca P. Chapman and David L. Bryce
PCCP(2007)9,6219.
Abstract:
A series of six L-amino acid hydrochloride salts has been studied by 35/37Cl solid-state NMR spectroscopy (at 11.75 and 21.1 T) and complementary quantum chemical calculations. Analyses of NMR spectra acquired under static and magic-angle-spinning conditions for the six hydrochloride salts, those of aspartic acid, alanine, cysteine, histidine, methionine and threonine, allowed the extraction of information regarding the chlorine electric field gradient (EFG) and chemical shift tensors, including their relative orientation. Both tensors are found to be highly dependent on the local environment, with chlorine-35 quadrupolar coupling constants (CQ) ranging from –7.1 to 4.41 MHz and chemical shift tensor spans ranging from 60 to 100 ppm; the value of CQ for aspartic acid hydrochloride is the largest in magnitude observed to date for an organic hydrochloride salt. Quantum chemical calculations performed on cluster models of the chloride ion environment demonstrated agreement between experiment and theory, reproducing CQ to within 18%. In addition, the accuracy of the calculated values of the NMR parameters as a function of the quality of the input structure was explored. Selected X-ray structures were determined (L-Asp HCl; L-Thr HCl) or re-determined (L-Cys HCl·H2O) to demonstrate the benefits of having accurate crystal structures for calculations. The self-consistent charge field perturbation model was also employed and was found to improve the accuracy of calculated quadrupolar coupling constants, demonstrating the impact of the neighbouring ions on the EFG tensor of the central chloride ion. Taken together, the present work contributes to an improved understanding of the factors influencing 35/37Cl NMR interaction tensors in organic hydrochlorides.

Hiyam's Journal Update

J. Am. Chem. Soc., 129 (47), 14717 -14723, 2007. 10.1021/ja0749690 S0002-7863(07)04969-4 Web Release Date: November 7, 2007 Copyright © 2007 American Chemical Society
Membrane-Bound Conformation of Peptaibols with Methyl-Deuterated -Amino Isobutyric Acids by 2H Magic Angle Spinning Solid-State NMR Spectroscopy
Kresten Bertelsen, Jan M. Pedersen, Brian S. Rasmussen, Troels Skrydstrup, Niels Chr. Nielsen, and Thomas Vosegaard*
Contribution from the Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark tv@chem.au.dk.
Received July 5, 2007
Abstract:
We present the use of 2H magic-angle spinning (MAS) NMR on methyl-deuterated -amino isobutyric acid (Aib) as a new method to obtain fast and accurate structural constraints on peptaibols in membrane-bound environments. Using nonoriented vesicle-reconstituted samples we avoid the delicate preparation of oriented samples, and the use of MAS ensures high sensitivity and thereby very fast acquisition of experimental spectra. Furthermore, given the high content (~40%) of Aib in peptaibols and the fact that the amino acid Aib may be synthesized from cheap starting materials, even in the case of 2H, 13C, or 15N labeling, this method is ideally suited for studies of the membrane-bound conformation of peptaibols.

Aaron's Journal Update

-Yining Huang, 23Na and 7Li NMR
J. Phys. Chem. C, 111 (36), 13427 -13436, 2007. 10.1021/jp0706275 S1932-7447(07)00627-9

Study of the Adsorption of Toluene in Zeolite LiNa-Y by Solid-State NMR Spectroscopy
Abstract: The adsorption of toluene inside partially Li+-exchanged zeolite Y (LiNa-Y) was examined by solid-state NMR spectroscopy. The environments of Li+ and Na+ ions at different sites in the framework before and after adsorption were characterized by 7Li and 23Na magic-angle-spinning (MAS) NMR. The information on the dynamic behavior of guest molecules inside the supercage of the zeolite was obtained from wide-line 2H NMR spectra. The cation-sorbate interactions were directly probed by heteronuclear dipolar coupling based double-resonance experiments such as 7Li{1H} and 23Na{1H} rotational-echo double-resonance (REDOR) experiments. Molecular modeling was also performed to assist in interpreting NMR results. The 7Li and 23Na MAS results indicate that during ion exchange the incoming Li+ ions fill the SI' sites first and then the SII sites, and the remaining Na+ ions stay mostly at SII sites. The MAS and REDOR results show that the toluene molecules are facially coordinated to the cations at SII sites in the supercage to form a -complex, resulting in a significant change in chemical shift of the Li+ ions and a dramatic reduction in the quadrupolar coupling constant (QCC) of the Na+ ions. The 2H NMR spectra indicate that at room temperature some toluene molecules reorient around the molecular long axis (two-site flip) and others undergo multiple-site jump motion, but at low temperature only two-site flip, at a much slower rate, remains. Both 2H and REDOR results show that the molecular dynamics of the guest species is also affected by the cation composition.


-Joel/Rob - M.E. Smith, 27Al, 29Si and 17O NMR

J. Phys. Chem. C, 111 (37), 13740 -13746, 2007. 10.1021/jp0739871 S1932-7447(07)03987-8

Structural Characterization of SiO2 and Al2O3 Zener-Pinned Nanocrystalline TiO2 by NMR, XRD and Electron Microscopy
Luke A. O'Dell, Shelley L.P. Savin, Alan V. Chadwick, and Mark E. Smith*
Abstract: Nanocrystalline TiO2 samples were prepared using sol-gel techniques in a pure form and also Zener pinned with either silica or alumina to reduce the growth of the crystallites during the annealing process and to stabilize the anatase phase at high temperatures. These samples were studied using 17O, 27Al, and 29Si nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and electron microscopy. The silica pinning phase was found to successfully restrict nanocrystal growth as well as stabilize the anatase phase at temperatures up to 800 C. The alumina phase had less of a pinning effect, and it reacted with the TiO2 to form tialite. 17O NMR relaxation time measurements on enriched samples showed that the presence of the pinning phases also reduced the activation energy for the oxygen ion diffusion mechanism.


Everyone - FAST MAS experiments to measure metal-carbon bond distances.

J. Phys. Chem. B, 111 (33), 9693 -9696, 2007. 10.1021/jp0727289 S1520-6106(07)02728-9

Elucidating Connectivity and Metal-Binding Structures of Unlabeled Paramagnetic Complexes by 13C and 1H Solid-State NMR under Fast Magic Angle Spinning
Nalinda P. Wickramasinghe, Medhat A. Shaibat, and Yoshitaka Ishii*
Abstract: Characterizing paramagnetic complexes in solids is an essential step toward understanding their molecular functions. However, methodologies to characterize chemical and electronic structures of paramagnetic systems at the molecular level have been notably limited, particularly for noncrystalline solids. We present an approach to obtain connectivities of chemical groups and metal-binding structures for unlabeled paramagnetic complexes by 13C and 1H high-resolution solid-state NMR (SSNMR) using very fast magic angle spinning (VFMAS, spinning speed 20 kHz). It is experimentally shown for unlabeled Cu(II)(Ala-Thr) that 2D 13C/1H correlation SSNMR under VFMAS provides the connectivity of chemical groups and assignments for the characterization of unlabeled paramagnetic systems in solids. We demonstrate that on the basis of the assignments provided by the VFMAS approach multiple 13C-metal distances can be simultaneously elucidated by a combination of measurements of 13C anisotropic hyperfine shifts and 13C T1 relaxation due to hyperfine interactions for this peptide-Cu(II) complex. It is also shown that an analysis of 1H anisotropic hyperfine shifts allows for the determination of electron-spin states in Fe(III)-chloroprotoporphyin-IX in solid states.


Rob??

J. Phys. Chem. B, 111 (33), 9711 -9721, 2007. 10.1021/jp072112j S1520-6106(07)02112-8
High-Resolution Solid-State NMR Studies of Poly(vinyl phosphonic acid) Proton-Conducting Polymer: Molecular Structure and Proton Dynamics
Young Joo Lee,* Bahar Bingöl, Tatiana Murakhtina, Daniel Sebastiani, Wolfgang H. Meyer, Gerhard Wegner, and Hans Wolfgang Spiess*
Abstract:The structure and the local proton mobility of poly(vinyl phosphonic acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P-OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P-OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P-OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from "normal" phosphonic acid and phosphonic acid anhydride. 31P double-quantum NMR experiments reveal that there is no phase segregation between normal and phosphonic acid anhydride and the condensation reaction occurs randomly throughout the system. The formation of acid anhydride leads to a decrease in proton conductivity through two mechanisms, (1) decrease in the number of charge carriers and (2) blockage of charge transport pathways through immobilization of charge carriers together with a hindered reorientation of the anhydride group. Our results provide strong evidence for these mechanisms by demonstrating that the conductivity is greatly influenced by the presence of phosphonic acid anhydride.



Hiyam/Joel

J. Phys. Chem. B, 111 (33), 9747 -9757, 2007. 10.1021/jp072061q S1520-6106(07)02061-5
27Al NMR Study of the Structure of Lanthanum- and Yttrium-Based Aluminosilicate Glasses and Melts
P. Florian,* N. Sadiki, D. Massiot, and J. P. Coutures
Abstract: We have investigated by 27Al nuclear magnetic resonance spectroscopy some compositions in the Ln2O3-Al2O3-SiO2 (Ln = Y or La) ternary phase diagram containing more than 60 mol % of SiO2. One- and two-dimensional high-field (17.6 T) high-speed (30 kHz) magic angle spinning experiments have been performed along with simulations of the spectra to quantify the amount of penta-coordinated aluminum present in those glasses as a function of composition. Very high-temperature experiments have allowed to follow selected samples from 2200 C down to 1700 C and hence to characterize the aluminum coordination state and dynamics in those liquids. The present study re-enforces the current view that "minor" species such as penta-coordinated aluminum are actually present in a considerable amount in aluminosilicate glasses, and high-temperature liquids at and above the charge compensation join. The high-field strength of Y3+ and La3+ reveal, for the first time in glasses, a different mean electric field gradient perceived by the tetra- and penta-coordinated aluminum environments. The movements responsible for the NMR relaxation of aluminum in the high-temperature liquid are shown to be uncorrelated with the movements responsible for the macroscopic shear viscosity. Results obtained both on glasses and in situ at high-temperature suggest a preferential localization of Ln3+ nearby tetra-coordinated aluminum species, with possible formation of tricluster and/or Ln3+ coordination changes.



-11B NMR

J. Phys. Chem. B, 111 (33), 9758 -9761, 2007. 10.1021/jp072223i S1520-6106(07)02223-7

11B MAS NMR Spectroscopic Study of Structural Relaxation, Aging, and Memory Effect at the Atomic Scale in a Borosilicate Glass
Sezen Soyer Uzun and Sabyasachi Sen*
Abstract: Relaxation kinetics of boron coordination environments in a borosilicate glass in response to temperature jumps has been monitored using 11B magic-angle spinning (MAS) NMR spectroscopy. The relaxation time scale of the BO4/BO3 ratio is found to be closely comparable with those of the bulk properties, namely, refractive index and viscosity, showing a close connection with one another. Samples partially equilibrated at a low temperature, when subjected to a positive temperature jump, display an initial rapid decrease followed by an increase in the BO4/BO3 ratio. This reversal in the trend of the variation of the BO4/BO3 ratio has been interpreted to be the signature of a memory effect, and the implications are discussed within the framework of the potential energy landscape model of glassy dynamics.



- Calculation of C13 tensors in order to measure ordering in a liquid crystal

J. Phys. Chem. B, 111 (33), 9787 -9794, 2007. 10.1021/jp0730693 S1520-6106(07)03069-6

Orientational Order of a Liquid Crystal with Three Chiral Centers by a Combined 13C NMR and DFT Approach
R. Y. Dong,* M. Geppi, A. Marini, V. Hamplova, M. Kaspar, C. A. Veracini, and J. Zhang
Abstract: In this work, the liquid crystal (S)-2-methylbutyl-[4'-(4' '-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/*) was investigated by means of 13C NMR spectroscopy. This compound has a very peculiar mesomorphic behavior, showing the following phases: paraelectric SmA, ferroelectric SmC*, antiferroelectric SmC*A, re-entrant ferroelectric SmC*re, and ferroelectric hexatic Sm*HEX. The structural and orientational ordering properties of ZLL 7/* have been determined by exploiting the nuclear chemical shielding properties of 13C. To this aim, solid-state NMR techniques such as CP, SPINAL-64, and SUPER have been used in combination with DFT calculations. The agreement between experimental and in vacuo DFT shielding parameters appears to be satisfactory. The orientational order parameters obtained from the 13C shielding analysis have been discussed, taking into account different data analysis approaches and comparing them to those previously obtained from an independent 2H NMR study.


-23Na and 95 Mo NMR

J. Phys. Chem. B, 111 (34), 10109 -10117, 2007. 10.1021/jp072883n S1520-6106(07)02883-0

Structural Studies of NaPO3-MoO3 Glasses by Solid-State Nuclear Magnetic Resonance and Raman Spectroscopy
Silvia H. Santagneli, Carla C. de Araujo, Wenzel Strojek, and Hellmut Eckert*
Gaël Poirier, Sidney J. L. Ribeiro, and Younes Messaddeq
Abstract: Vitreous samples were prepared in the (100 - x)% NaPO3-x% MoO3 (0 x 70) glass-forming system by a modified melt method that allowed good optical quality samples to be obtained. The structural evolution of the vitreous network was monitored as a function of composition by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), Raman scattering, and solid-state nuclear magnetic resonance (NMR) for 31P, 23Na, and 95Mo nuclei. Addition of MoO3 to the NaPO3 glass melt leads to a pronounced increase in the glass transition temperatures up to x = 45, suggesting a significant increase in network connectivity. For this same composition range, vibrational spectra suggest that the Mo6+ ions are bonded to some nonbridging oxygen atoms (Mo-O- or Mo=O bonded species). Mo-O-Mo bond formation occurs only at MoO3 contents exceeding x = 45. 31P magic-angle spinning (MAS) NMR spectra, supported by two-dimensional J-resolved spectroscopy, allow a clear distinction between species having two, one, and zero P-O-P linkages. These sites are denoted as Q(2)2Mo, Q(2)1Mo, and Q(2)0Mo, respectively. For x < n =" 0," x =" 45">

- Learn all about membrane proteins

J. Phys. Chem. B, 111 (35), 10340 -10351, 2007. 10.1021/jp073652j S1520-6106(07)03652-8

Structure, Topology, and Dynamics of Membrane Peptides and Proteins from Solid-State NMR Spectroscopy
Mei Hong
Abstract:The high-resolution structure of membrane proteins is notoriously difficult to determine due to the hydrophobic nature of the protein-membrane complexes. Solid-state NMR spectroscopy is a unique and powerful atomic-resolution probe of the structure and dynamics of these important biological molecules. A number of new solid-state NMR methods for determining the depth of insertion, orientation, oligomeric structure, and long-range (10-15 Å) distances of membrane proteins are summarized. Membrane protein depths can now be determined using several complementary techniques with varying site-specificity, distance precision, and mobility requirement on the protein. Membrane protein orientation can now be determined with or without macroscopic alignment, the latter providing a novel alternative for orientation determination of intrinsically curvature-inducing proteins. The novel analyses of -sheet membrane protein orientation are described. The quaternary structure of membrane peptide assemblies can now be elucidated using a 19F spin diffusion technique that simultaneously yields the oligomeric number and intermolecular distances up to 15 Å. Finally, long-range distances up to ~10 Å can now be measured using 1H spins with an accuracy of better than 1 Å. These methods are demonstrated on several -sheet membrane peptides with antimicrobial activities and on two -helical ion-channel proteins. Finally, we show that the nearly ubiquitous dynamics of membrane proteins can be readily examined using 2D correlation experiments. An intimate appreciation of molecular motion in these systems not only leads to important insights into the specific function of these membrane proteins but also may be exploited for other purposes such as orientation determination.


-27Al{19F} and 23Na{19F} REDOR experiments

J. Phys. Chem. B, 111 (35), 10402 -10412, 2007. 10.1021/jp072725w S1520-6106(07)02725-3

Structural Role of Fluoride in Aluminophosphate Sol-Gel Glasses: High-Resolution Double-Resonance NMR Studies
Long Zhang, Carla C. de Araujo, and Hellmut Eckert*
Abstract: The local structure of Na-Al-P-O-F glasses, prepared by a novel sol-gel route, was extensively investigated by advanced solid-state NMR techniques. 27Al{19F} rotational echo double resonance (REDOR) results indicate that the F incorporated into aluminophosphate glass is preferentially bonded to octahedral Al units and results in a significant increase in the concentration of six-coordinated aluminum. The extent of Al-F and Al-O-P connectivities are quantified consistently by analyzing 27Al{31P} and 27Al{19F} REDOR NMR data. Two distinct types of fluorine species were identified and characterized by various 19F{27Al}, 19F{23Na}, and 19F{31P} double resonance experiments, which were able to support peak assignments to bridging (Al-F-Al, -140 ppm) and terminal (Al-F, -170 ppm) units. On the basis of the detailed quantitative dipole-dipole coupling information obtained, a comprehensive structural model for these glasses is presented, detailing the structural speciation as a function of composition.


-27Al, 23Na, 19F, 29Si Solids NMR

J. Phys. Chem. B, 111 (35), 10413 -10420, 2007. 10.1021/jp073687j S1520-6106(07)03687-5

Preferential Binding of Fluorine to Aluminum in High Peralkaline Aluminosilicate Glasses
N. G. Karpukhina, U. Werner-Zwanziger, J. W. Zwanziger,* and A. A. Kiprianov
Abstract: For two series of fluoride-containing aluminosilicate glasses of high peralkaline type, we apply 27Al, 19F, 29Si, and 23Na NMR spectroscopy to understand the structural changes introduced by the addition of alkali fluorides. Adding fluoride in concentrations above the solubility limit causes crystallization of different phases in sodium and potassium glasses despite identical composition. However, the NMR spectra reveal that the structural evolution of the precrystallized states is similar in both series. In particular, fluorine coordinates exclusively to alkaline cations and aluminum. No indication of direct bonding with silicon was found from 19F 29Si cross-polarization experiments. In contrast to other glass systems, double resonance experiments in these peralkaline systems show that halide addition produces at most a minor fraction of tetrahedral aluminum containing fluorine in its coordination sphere. Instead, the fluorine addition prior to crystallization converts up to about 20% of the initial tetrahedral aluminum (1 mol % in absolute units) to 5- and 6-fold coordinated aluminum. A minor portion of five-coordinated aluminum groups is considered as the intermediate to the growing fraction of octahedral aluminum in the silicate matrix. The initialization of the crystallization process is correlated with the saturation of the silicate matrix by octahedral aluminum clusters segregating out under further doping by fluoride. It is suggested that the formation of the nonframework Al-F bonds is responsible for structural relaxation, reflected by the reduction of the glass transition temperature.



J. Phys. Chem. B, 111 (36), 10671 -10680, 2007. 10.1021/jp072001k S1520-6106(07)02001-9

Ab Initio Calculation of Solid-State NMR Spectra for Different Triazine and Heptazine Based Structure Proposals of g-C3N4
Jan Sehnert, Kilian Baerwinkel, and Juergen Senker*
Abstract: We present a comprehensive theoretical study of the structure and NMR parameters of a large number of triazine and heptazine based structure proposals for g-C3N4 in different condensation states. This approach includes a detailed investigation of cyclic melon which tends toward the formation of densely packed hydrogen bonded meshes. In all of the investigated systems, we found planar layers to represent saddlepoints on the energy surface, whereas corrugated species were identified as minima. The corrugation source was linked to the repulsion of nitrogen lone pairs in close NN contacts. A linear dependency of the corrugation energy from the number of NN interactions in the investigated clusters was found. Heptazine based systems gain about twice as much energy per NN close contact in comparison to triazine structures which could be understood in terms of the distortion mechanism in the investigated structures. Furthermore, a full study of the 15N and 13C chemical shift tensors was performed for the different C/N layers. The description of the NMR parameters required dividing the investigated systems into subclusters for which the NMR tensors were calculated with density functional theory (DFT) methods. A statistical analysis of these entities allowed for the investigation of the change in the chemical shift upon corrugation and, in the case of the cyclic melon system, hydrogen bonding. With the here presented study, the most prominent structure models for g-C3N4 are characterized in terms of the 15N and 13C NMR parameters which now can directly be compared to experimental spectra.


-Calculation of J-couplings in DNA

J. Phys. Chem. B, 111 (36), 10813 -10824, 2007. 10.1021/jp072822p S1520-6106(07)02822-2

Theoretical Study of the Scalar Coupling Constants across the Noncovalent Contacts in RNA Base Pairs: The cis- and trans-Watson-Crick/Sugar Edge Base Pair Family
Zuzana Vok ov , Ji í poner, Judit E. poner, and Vladimír Sychrovsk *
Abstract:The structure and function of RNA molecules are substantially affected by non-Watson-Crick base pairs actively utilizing the 2'-hydroxyl group of ribose. Here we correlate scalar coupling constants across the noncovalent contacts calculated for the cis- and trans-WC/SE (Watson-Crick/sugar edge) RNA base pairs with the geometry of base to base and sugar to base hydrogen bond(s). 23 RNA base pairs from the 32 investigated were found in RNA crystal structures, and the calculated scalar couplings are therefore experimentally relevant with regard to the binding patterns occurring in this class of RNA base pairs. The intermolecular scalar couplings 1hJ(N,H), 2hJ(N,N), 2hJ(C,H), and 3hJ(C,N) were calculated for the N-H···N and N-H···O=C base to base contacts and various noncovalent links between the sugar hydroxyl and RNA base. Also, the intramolecular 1J(N,H) and 2J(C,H) couplings were calculated for the amino or imino group of RNA base and the ribose 2'-hydroxyl group involved in the noncovalent interactions. The calculated scalar couplings have implications for validation of local geometry, show specificity for the amino and imino groups of RNA base involved in the linkage, and can be used for discrimination between the cis- and trans-WC/SE base pairs. The RNA base pairs within an isosteric subclass of the WC/SE binding patterns can be further sorted according to the scalar couplings calculated across different local noncovalent contacts. The effect of explicit water inserted in the RNA base pairs on the magnitude of the scalar couplings was calculated, and the data for discrimination between the water-inserted and direct RNA base pairs are presented. The calculated NMR data are significant for structural interpretation of the scalar couplings in the noncanonical RNA base pairs.



-35/37Cl NMR of Ionic Liquids

J. Phys. Chem. B, 111 (40), 11619 -11621, 2007. 10.1021/jp0756449 S1520-6106(07)05644-1

Hydrogen Bonds in Ionic Liquids Revisited: 35/37Cl NMR Studies of Deuterium Isotope Effects in 1-n-Butyl-3-Methylimidazolium Chloride
Richard C. Remsing, Jayme L. Wildin, Ashleigh L. Rapp, and Guillermo Moyna*
Abstract: Detailed knowledge of the structure, dynamics, and interionic interactions of ionic liquids (ILs) is critical to understand their physicochemical properties. In this letter, we show that deuterium isotope effects on the chloride ion 35/37Cl NMR signal represent a useful tool in the study of interionic hydrogen bonds in imidazolium chloride ILs. Sizable 35/37Cl(H,D) values obtained for the model system 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) upon deuteriation of the imidazolium C-2 and C-2,4,5 positions, of nearly 1 and 2 ppm, respectively, show that the approach can readily identify and differentiate Cl···H hydrogen bonds between the anion and cation. Our study is one of a few examples in which hydrogen-bonding in ILs has been investigated using deuterium isotope effects and, to our knowledge, the only one employing 35/37Cl NMR to detect these interactions. The methodology described could be easily extended to the study of other systems bearing NMR-active nuclei.



-The title says it all

J. Phys. Chem. B, 111 (42), 12088 -12096, 2007. 10.1021/jp073682m S1520-6106(07)03682-6

NMR Provides Checklist of Generic Properties for Atomic-Scale Models of Periodic Mesoporous Silicas
Ilja G. Shenderovich,* Daniel Mauder, Dilek Akcakayiran, Gerd Buntkowsky, Hans-Heinrich Limbach,* and Gerhard H. Findenegg
Abstract:MCM-41 and SBA-15 silicas were studied by 29Si solid-state NMR and 15N NMR in the presence of 15N-pyridine with the aim to formulate generic structural parameters that may be used as a checklist for atomic-scale structural models of this class of ordered mesoporous materials. High-quality MCM-41 silica constitutes quasi-ideal arrays of uniform-size pores with thin pore walls, while SBA-15 silica has thicker pore walls with framework and surface defects. The numbers of silanol (Q3) and silicate (Q4) groups were found to be in the ratio of about 1:3 for MCM-41 and about 1:4 for our SBA-15 materials. Combined with the earlier finding that the density of surface silanol groups is about three per nm2 in MCM-41 (Shenderovich, et al. J. Phys. Chem. B 2003, 107, 11924) this allows us to discriminate between different atomic-scale models of these materials. Neither tridymite nor edingtonite meet both of these requirements. On the basis of the hexagonal pore shape model, the experimental Q3:Q4 ratio yields a wall thickness of about 0.95 nm for MCM-41 silica, corresponding to the width of ca. four silica tetrahedra. The arrangement of Q3 groups at the silica surfaces was analyzed using postsynthesis surface functionalization. It was found that the number of covalent bonds to the surface formed by the functional reagents is affected by the surface morphology. It is concluded that for high-quality MCM-41 silicas the distance between neighboring surface silanol groups is greater than 0.5 nm. As a result, di- and tripodical reagents like (CH3)2Si(OH)2 and CH3Si(OH)3 can form only one covalent bond to the surface. The residual hydroxyl groups of surface-bonded functional reagents either remain free or interact with other reagent molecules. Accordingly, the number of surface silanol groups at a given MCM-41 or SBA-15 silica may not decrease but increase after treatment with CH3Si(OH)3 reagent. On the other hand, nearly all surface silanol groups could be functionalized when HN(Si(CH3)3)2 was used.


J. Phys. Chem. B, 111 (42), 12097 -12102, 2007. 10.1021/jp074517+ S1520-6106(07)04517-8

Rotation and Diffusion of H2 in Hydrogen-Ice Clathrate by 1H NMR
Lasitha Senadheera and Mark S. Conradi*
Abstract:A recently reported hydrogen-ice clathrate carries up to four H2 in each large cage and one H2 in each small cage. We report pulsed proton NMR line shape measurements on H2-D2O clathrate formed at 1500 bar and 250 K. The behavior of the two-pulse spin-echo amplitude with respect to the nutation angle of the refocusing pulse shows that intramolecular dipolar broadening, modulated by H2 molecular reorientations, dominates the line width of the ortho-H2. Dipolar interaction between H2 guests and host D atoms explains the echo variation with the relative phases of the pulses. From 12 to 120 K, the line width varies as 1/T, demonstrating that the three sublevels of J = 1 are split by a constant energy, . The splitting arises from distortion in the otherwise high-symmetry cages from frozen-out D2O orientational disorder. Above 120 K, further line-narrowing signals the onset of H2 diffusion from cage to cage. At the lowest temperature, 1.9 K, the spectrum has Pake powder doublet-like features; the doublet is not fully developed, indicating a broad distribution of order parameters and energies .



J. Phys. Chem. B, 111 (42), 12119 -12123, 2007. 10.1021/jp076046x S1520-6106(07)06046-4

Solid-State 13C NMR Studies on Organic-Inorganic Hybrid Zeolites
Katsutoshi Yamamoto, Yasuyuki Sakata, and Takashi Tatsumi*
Abstract:A novel type of organic-inorganic hybrid zeolite with organic lattice (ZOL) is studied in detail by solid-state 13C magic angle spinning nuclear magnetic resonance (MAS NMR). The 13C MAS NMR measurements employing several pulse sequences quantitatively demonstrate that methylene groups are really incorporated in the framework, although they are partially cleaved into methyl groups. The organic species in ZOL materials are open for adsorbates, which is evidenced by the 13C MAS NMR measurements for an n-hexane-adsorbing ZOL material. This finding strongly suggests that organic moieties are incorporated as a zeolite framework, indicating that ZOL is not a physical mixture of a carbon-containing amorphous aggregate and a conventional zeolite but a true organic-inorganic hybrid zeolite.

-Massiot: 27Al NMR
J. Phys. Chem. B, 111 (44), 12707 -12714, 2007. 10.1021/jp072620t S1520-6106(07)02620-X
Cation Sublattice Disorder Induced by Swift Heavy Ions in MgAl2O4 and ZnAl2O4 Spinels: 27Al Solid-State NMR Study
Nadia Pellerin,* Catherine Dodane-Thiriet, Valérie Montouillout, Michel Beauvy, and Dominique Massiot
Abstract: MgAl2O4 and ZnAl2O4 spinels have been irradiated by swift heavy ions (86Kr and 36S) simulating the irradiation by fission products for applications in the transmutation targets. The structures of unirradiated and irradiated spinel samples have been studied by NMR spectroscopy, with 27Al magic angle spinning and multiple-quantum magic angle spinning experiments. The parameters of fluence and electronic stopping power have been compared. For 86Kr ions, the obtained spectra are modified by irradiation: we observe a rise of the amount of aluminum in tetrahedral sites and a widening of the lines associated with the different aluminum environments compared with those of the pristine samples. Site exchange in the cationic sublattice is then observed and can be quantified from NMR spectra, determining the inversion parameter. An inversion parameter of 0.77 is estimated for the MgAl2O4 spinel irradiated with 1013 Kr ions/cm2, for a value of 0.275 in the pristine samples. Moreover, a line attributed to aluminum in 5-fold coordination with oxygen is observed in irradiated spinel samples at the maximum fluence for krypton. These new aluminum environments can characterize a transition layer which could change toward an amorphous layer, increasing the electronic stopping power and/or the fluence.

- Speiss 13C NMR Studies of Polymers
Macromolecules, 40 (17), 6249 -6256, 2007. 10.1021/ma0706531 S0024-9297(07)00653-5 Chain Dynamics in Poly(n-alkyl acrylates) by Solid-State NMR, Dielectric, and Mechanical Spectroscopies
Marianne Gaborieau,* Robert Graf, Stefan Kahle, Tadeusz Pakula, and Hans W. Spiess*
Abstract:A relaxation process was detected and quantified for the first time in various poly(n-alkyl acrylates) in the melt by a solid-state NMR method, NOE with dipolar filter. By comparison with dielectric spectroscopy and dynamic mechanical measurements carried out on the same samples, the relaxation process detected by NMR occurs at a higher temperature than the simple -relaxation and on a longer time scale than the -relaxation (cooperative -relaxation). This relaxation process could be the isotropization of the main chain (by analogy with structurally similar polymethacrylates), but it is more probably a local relaxation within the alkyl side chain that is usually detected only at significantly lower temperatures. The fact that this side-chain motion is slower than the cooperative main-chain -relaxation of restricted amplitude can be rationalized in the context of restricted amplitude main-chain motions in the local nanostructure present in the samples, as NMR and dielectric spectroscopy detect motions in different frames.

Hiyam's Journal Update

J. Am. Chem. Soc., 129 (45), 13806 -13807, 2007.
Probing Spatially-Resolved Pt Distribution in PtRu Nanoparticles with 195Pt EC-NMR
Aaron L. Danberry, Bingchen Du, In-Su Park, Yung-Eun Sung, and YuYe Tong*

Abstract:
We report the first quantitative analysis of spatially resolved local Pt distribution in graphite and carbon nanofibers supported PtRu alloy nanoparticles using slow-beat measurements by in situ 195Pt electrochemical NMR. While the two samples had the same nominal 1:1 atomic ratio and similar average particle size, it was found that the former had a rather homogeneous Pt distribution but not the latter, which had Pt segregation at the core and depletion at the surface of the nanoparticles.

Hiyam's Journal Update

Phys. Rev. Lett. 99, 187003 (2007)
NMR Relaxation and Resistivity from Rattling Phonons in Pyrochlore Superconductors
Thomas Dahm1,2 and Kazuo Ueda1
(Received 13 June 2007; published 30 October 2007)

We calculate the temperature dependence of the NMR relaxation rate and electrical resistivity for coupling to a local, strongly anharmonic phonon mode. We argue that the two-phonon Raman process is dominating NMR relaxation. Due to the strong anharmonicity of the phonon an unusual temperature dependence is found having a low temperature peak and becoming constant towards higher temperatures. The electrical resistivity is found to vary like T2 at low temperatures and following a behavior at high temperatures. Both results are in qualitative agreement with recent observations on -pyrochlore oxide superconductors.

Phys. Rev. Lett. 99, 187601 (2007)

Stochastic Dipolar Recoupling in Nuclear Magnetic Resonance of Solids
Robert Tycko
(Received 1 August 2007; published 2 November 2007)

I describe a nuclear magnetic resonance (NMR) technique, called stochastic dipolar recoupling (SDR), that permits continuous experimental control of the character of spin dynamics between coherent and incoherent limits in a system of magnetic dipole-coupled nuclei. In the fully incoherent limit of SDR, spin polarization transfers occur at distance-dependent rates without the quantum mechanical interferences among pairwise dipole-dipole couplings that often limit the feasibility or precision of structural studies of solids by NMR. In addition to facilitating structural studies, SDR represents a possible route to experimental studies of effects of decoherence on the dynamics of quantum many-body systems.