J Phys Chem C, vol. 113, Issue 4

Effect of Al−Si−Al and Al−Si−Si−Al Pairs in the ZSM-5 Zeolite Framework on the 27Al NMR Spectra. A Combined High-Resolution 27Al NMR and DFT/MM Study

Jiří Dědeček†, Stepan Sklenak*†, Chengbin Li†, Blanka Wichterlová†, Vendula Gábová†, Jiří Brus‡, Marek Sierka§ and Joachim Sauer§
J. Phys. Chem. C, 2009, 113 (4), pp 1447–1458
Publication Date (Web): January 8, 2009
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic.,
* Corresponding author. E-mail: stepan.sklenak@jh-inst.cas.cz.,

Abstract: The effect of the presence of Al−O−Si−O−Al and Al−O−Si−O−Si−O−Al sequences in the ZSM-5 zeolite framework on the local geometry of AlO4− tetrahedra and the 27Al NMR parameters was investigated employing 27Al 3Q MAS NMR spectroscopy and DFT/MM calculations. The presence of an Al atom as a next-nearest (Al−O−Si−O−Al) and next-next-nearest (Al−O−Si−O−Si−O−Al) neighbor can significantly affect both the local geometry of AlO4− tetrahedra as well as 27Al NMR isotropic chemical shift (up to 4 ppm). There is no systematic contribution of Al in Al−O−Si−O−Al or Al−O−(Si−O)2−Al chains to the 27Al isotropic chemical shift, and not even the direction can be predicted without explicit DFT calculations. Our combined experimental and computational approach employing 27Al (3Q) MAS NMR spectroscopy supported by DFT/MM calculations ( Sklenak, S.; Dědeček, J.; Li, C.; Wichterlová, B.; Gábová, V.; Sierka, M.; Sauer, J. Angew. Chem., Int. Ed. 2007, 46, 7286.) can be employed only for ZSM-5 samples having a low or negligible concentration of Al−O−(Si−O)n−Al (n = 1 and 2) sequences in the zeolite matrix, otherwise 27Al (3Q) MAS NMR spectroscopy cannot be used to even identify the number of framework T sites occupied by Al.

J Phys Chem B, vol. 113, Issue 4

Solid-State NMR Studies of Aminocarboxylic Salt Bridges in l-Lysine Modified Cellulose
Ricardo Manríquez†‡, Fernando A. López-Dellamary‡, Jaroslaw Frydel†, Thomas Emmler†, Hergen Breitzke§, Gerd Buntkowsky§, Hans-Heinrich Limbach† and Ilja G. Shenderovich*†#
J. Phys. Chem. B, 2009, 113 (4), pp 934–940
DOI: 10.1021/jp8081968

Abstract: LysCel is a cellulose-based material in which l-lysine molecules are grafted with their amino side chains to the cellulose hydroxyl groups. This modification increases considerably the mechanical strength and resistance of cellulosic structures toward water. It has been attributed to the formation of double salt bridges between lysine aminocarboxyl groups in the zwitterionic state. In order to characterize this unusual structure, we have performed high-resolution solid-state 15N and 13C CPMAS NMR experiments on LysCel samples labeled with 15N in the α-position or ε-position. Furthermore, 13C−15N REDOR experiments were performed on LysCel where half of the aminocarboxyl groups were labeled in 1-position with 13C and the other half in α-position with 15N. The comparison with the 13C and 15N chemical shifts of l-leucine lyophilized at different pH shows that the aminocarboxyl groups of LysCel are indeed zwitterionic. The REDOR experiments indicate distances of about 3.5 Å between the carboxyl carbon and the nitrogen atoms of different aminocarboxyl groups, indicating that the latter are in close contact with each other. However, the data are not compatible with isolated aminocarboxyl dimers but indicate the assembly of zwitterionic aminocarboxyl dimers either in a flat ribbon or as tetramers, exhibiting similar intra- and interdimer 13C···15N distances. This interaction of several aminocarboxyl groups is responsible for the zwitterionic state, in contrast to the gas phase, where amino acid dimers exhibiting two OHN hydrogen bonds are neutral.

MRC: Magn. Reson. Chem. (Wiley) up to Jan. 20, 2009

Magn. Reson. Chem. (Wiley) up to Jan. 20, 2009

Magnetic Resonance in Chemistry
Volume 47 Issue 1, Pages 9 - 15
Published Online: 4 Nov 2008

Solid-state natural abundance 25Mg NMR studies of Na2MgEDTA·4H2O - a possible new reference compound for 25Mg NMR spectroscopy
from Magnetic Resonance in Chemistry by Jair C. C. Freitas, Alan Wong, Mark E. Smith
Natural abundance solid-state 25Mg NMR measurements were made of the disodium salt of magnesium ethylenediaminetetraacetate tetrahydrate (Na2MgEDTA·4H2O). Both magic angle spinning (MAS) and static experiments were employed to determine the quadrupole coupling constant (Cq) and the asymmetry parameter ([eta]q) of the electric field gradient (EFG) tensor associated with 25Mg in this compound, giving the values Cq = 1.675(5) MHz and [eta]q = 0.15(1). The isotropic chemical shift was determined to be [delta]iso = 0.25(10) ppm (relative to 11 M MgCl2 aqueous solution) and a small chemical shift anisotropy (CSA) contribution ([sim]- 13 ppm) was detected, one of the first CSA reports in 25Mg NMR. This compound exhibited remarkably good 25Mg NMR sensitivity, due to its fast spin-lattice relaxation and modest quadrupole coupling, which allowed its use as a secondary shift reference and as a test sample for the implementation and optimisation of signal-enhancement methods in 25Mg NMR spectroscopy, such as double frequency sweeps (DFS) and the use of adiabatic hyperbolic secant (HS) and WURST pulses. Copyright © 2008 John Wiley & Sons, Ltd.

--

Magnetic Resonance in Chemistry
Volume 47 Issue 2, Pages 97 - 99
Published Online: 21 Oct 2008

Electronic structure and biological activity of chosen DDT-type insecticides studied by 35Cl-NQR
from Magnetic Resonance in Chemistry by Maciej Jad[zdot]yn, Boles[lstrok]aw Nogaj
A correlation between the electronic structure and biological activity of chosen dichlorodiphenyltrichloroethane (DDT)-type insecticides: 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene, 2,2-bis(4-chlorophenyl)ethanoic acid and 4,4[prime]-dichlorobenzophenone (used in agriculture) has been analysed on the basis of the 35Cl-nuclear quadrupole resonance (NQR) spectroscopy. The 35Cl-NQR resonance frequencies measured at 77 K have been correlated with the lethal dose (LD50) parameter that characterises the biological activity of these insecticides. Copyright © 2008 John Wiley & Sons, Ltd.

--

Magnetic Resonance in Chemistry
Volume 46 Issue S1, Pages S36 - S44
Special Issue: Diffusion ordered and heteronuclear NMR spectroscopy applied to inorganic and organometallic chemistry. Special Issue dedicated to Professor Paul S. Pregosin on the occasion of his 65th birthday
Published Online: 14 Oct 2008

Density-functional computation of 99Tc NMR chemical shifts
from Magnetic Resonance in Chemistry by Michael Bühl, Volodymyr Golubnychiy
99Tc chemical shifts of TcO4-, TcH92-, TcOF5, TcO2F4-, TcOCl4-, Tc2(CO)10, and Tc(CO)3L3+ (L = CO, MeCN, H2O) are computed using geometries optimized with the gradient-corrected BP86 and hybrid B3P86 density functionals, at the gauge-including atomic orbitals (GIAO), -BPW91 and -B3LYP levels. For this set of compounds, substituent effects on [delta](99Tc) are better described with the pure BPW91 functional than with B3LYP, in contrast to most other transition-metal chemical shifts studied so far. A rough, qualitative correlation is found between computed electric-field gradients at the Tc nuclei and the corresponding 99Tc NMR line widths. Thermal and solvation effects on magnetic shielding constants of aqueous TcO4-, as assessed by averaging these properties over trajectories from Car-Parrinello molecular dynamics simulations, are indicated to be small and comparable to those of MnO4-. Complexation to aqueous uranyl, UO22+, is predicted to affect [delta](99Tc) of TcO4- only slightly; somewhat larger complexation shifts are obtained for the oxygen nuclei of pertechnetate, suggesting that 17O NMR could be a useful probe for the extent of association between both radionuclides in solution. Copyright © 2008 John Wiley & Sons, Ltd.

--

Magnetic Resonance in Chemistry
Volume 46 Issue S1, Pages S45 - S55
Special Issue: Diffusion ordered and heteronuclear NMR spectroscopy applied to inorganic and organometallic chemistry. Special Issue dedicated to Professor Paul S. Pregosin on the occasion of his 65th birthday
Published Online: 14 Oct 2008

Analyzing Pt chemical shifts calculated from relativistic density functional theory using localized orbitals: The role of Pt 5d lone pairs
from Magnetic Resonance in Chemistry by Jochen Autschbach, Shaohui Zheng
Pt chemical shifts were calculated from two-component relativistic density functional theory (DFT). The shielding tensors were analyzed by using a recently developed method to decompose the spin-orbit DFT results into contributions from spin-free localized orbitals (here: natural localized molecular orbitals (NLMOs) and natural bond orbitals (NBOs)). Seven chemical shifts in six Pt complexes with Pt oxidation states II, III, and IV; and halide, amino, and amidate ligands were analyzed, with particular focus on the role of nonbonding Pt 5d orbitals. A simple d-orbital 'rotation' model has been used to rationalize some of the observed trends such as the main difference between Pt(II) and Pt(IV) chemical shifts. The localized orbital analysis data showed that most of this difference as well as trends among different Pt complexes with similar coordination can be rationalized by comparing properties of the nonbonding Pt 5d orbitals. We have also analyzed the spin-orbit effects on the chemical shifts of [PtCl4]2- compared to [PtBr4]2-. Copyright © 2008 John Wiley & Sons, Ltd.

--

Magnetic Resonance in Chemistry
Volume 46 Issue 11, Pages 1045 - 1050
Published Online: 19 Sep 2008

DFT calculations as a powerful technique to probe the crystal structure of Al(acac)3

from Magnetic Resonance in Chemistry by S. K. Amini, M. Tafazzoli

27Al, 17O and 13C chemical shieldings of aluminum acetylacetonate complex, Al(acac)3, were calculated at some Density Functional Theory (DFT) levels of theory. In these calculations the X-ray structures of its different polymorphs were used. Using these calculated data observed discrepancies between the X-ray crystallography and solid state NMR experiment were explained in terms of the quality of the NMR data. In this survey we resorted to the simulated spectra using our calculated chemical shifts. In order to confirm our conclusions, electric field gradient (EFG) tensors of the 27Al and 17O nuclei were calculated at the same levels of theory as used in the chemical shielding calculations. On the other hand, these calculated chemical shifts and nuclear quadrupole coupling constants (NQCCs) made a correlation between X-ray crystallography and solid state NMR experiments. Copyright © 2008 John Wiley & Sons, Ltd.

Faraday Discussions (RSC) - up to Jan. 20, 2009

Faraday Disc. (RSC) - up to Jan. 20, 2009

Faraday Discuss., 2009, 140, 139 - 153, DOI: 10.1039/b803073a
A comparative in situ195Pt electrochemical-NMR investigation of PtRu nanoparticles supported on diverse carbon nanomaterials

Fatang Tan, Bingchen Du, Aaron L. Danberry, In-Su Park, Yung-Eun Sung and YuYe Tong
This paper reports a detailed in situ195Pt electrochemical-nuclear magnetic resonance (EC-NMR) study of PtRu nanoparticles (NPs) that had a nominal atomic ratio of Pt : Ru = 1 : 1 and were supported on carbon nanocoils and carbon black (Vulcan XC-72) respectively. The particle sizes of the two samples were determined by X-ray diffraction using the Sherrer equation: 3.6 nm for the former and 3.2 nm for the latter, which were further corroborated by transmission electron microscope measurements. By taking advantage of a unique correlation between the spectral frequency of the 195Pt NMR resonance and the radial atomic position in a particle, qualitatively- and spatially-resolved local Pt atomic fractions in the particles were deduced by using a Ruderman–Kittel–Kasuya–Yosida (RKKY) J-coupling-based method as a function of different electrode potentials. The results indicated that both samples had Pt-enriched cores and Pt-deprived surfaces and, most importantly, the local Pt concentration varied as the electrochemical environment changed. The spatially-resolved Fermi level local densities of states (Ef-LDOS), which are a measure of the electronic frontier orbitals in metals, were deduced across the NMR spectrum and correlated with the EC activity in methanol electro-oxidation. The results were also compared to those obtained previously from Pt/Ru NPs supported respectively on carbon and graphite nanofibers.

--

Faraday Discuss., 2009, 140, 69 - 80, DOI: 10.1039/b802919a
Bridging the gap between nanoparticles and single crystal surfaces

Payam Kaghazchi, Felice C. Simeone, Khaled A. Soliman, Ludwig A. Kibler and Timo Jacob
Using density functional theory calculations and the extended ab initio atomistic thermodynamics approach, we studied the adsorption of oxygen on the different surface faces, which are involved in the faceting of Ir(210). Constructing the (p,T)-surface phase diagrams of the corresponding surfaces in contact with an oxygen atmosphere, we find that at high temperatures the planar surfaces are stable, while lowering the temperature stabilizes those nano-facets found experimentally. Afterwards, we constructed the (a,T,)-phase diagram for Ir(210) in contact with an aqueous electrolyte and found that the same nano-facets should be stable under electrochemical conditions. Motivated by this prediction from theory, experiments were performed using cyclic voltammetry and in-situ scanning tunneling microscopy. The presence of nanofacets for Ir(210) gives rise to a characteristic current-peak in the hydrogen adsorption region for sulfuric acid solution. Furthermore, first results on the electrocatalytic behavior of nano-faceted Ir(210) are presented.

Chem. Soc. Rev. - Chemical Society Reviews (RSC) - up to Jan. 21, 2009

Chemical Society Reviews (RSC) - up to Jan. 21, 2009

Some interesting Chem. Soc. Rev. articles that might be of interest to the group
(no NMR here, but some interesting topics)

Critical Review

Chem. Soc. Rev., 2009, 38, 185 - 196, DOI: 10.1039/b802262n
Photosynthetic energy conversion: natural and artificial

James Barber
Photosystem II (PSII) is the water splitting enzyme of photosynthesis. Its appearance during evolution dramatically changed the chemical composition of our planet and set in motion an unprecedented explosion in biological activity. Powered by sunlight, PSII supplies biology with the hydrogen needed to convert carbon dioxide into organic molecules. The questions now are can we continue to exploit this photosynthetic process through increased use of biomass as an energy source and, more importantly, can we address the energy/CO2 problem by developing new photochemical technologies which mimic the natural system? (Critical review, 82 references)

--

Tutorial Review

Chem. Soc. Rev., 2009, 38, 25 - 35, DOI: 10.1039/b800582f
Biology and technology for photochemical fuel production

Michael Hambourger, Gary F. Moore, David M. Kramer, Devens Gust, Ana L. Moore and Thomas A. Moore
Sunlight is the ultimate energy source for the vast majority of life on Earth, and organisms have evolved elegant machinery for energy capture and utilization. Solar energy, whether converted to wind, rain, biomass or fossil fuels, is also the primary energy source for human-engineered energy transduction systems. This tutorial review draws parallels between biological and technological energy systems. Aspects of biology that might be advantageously incorporated into emerging technologies are highlighted, as well as ways in which technology might improve upon the principles found in biological systems. Emphasis is placed upon artificial photosynthesis, as well as the use of protonmotive force in biology.

--

Tutorial Review

Chem. Soc. Rev., 2009, 38, 73 - 82, DOI: 10.1039/b718842k
New approaches to hydrogen storage

Jason Graetz
The emergence of a Hydrogen Economy will require the development of new media capable of safely storing hydrogen in a compact and light weight package. Metal hydrides and complex hydrides, where hydrogen is chemically bonded to the metal atoms in the bulk, offer some hope of overcoming the challenges associated with hydrogen storage. The objective is to find a material with a high volumetric and gravimetric hydrogen density that can also meet the unique demands of a low temperature automotive fuel cell. Currently, there is considerable effort to develop new materials with tunable thermodynamic and kinetic properties. This tutorial review provides an overview of the different types of metal hydrides and complex hydrides being investigated for on-board (reversible) and off-board (non-reversible) hydrogen storage along with a few new approaches to improving the hydrogenation–dehydrogenation properties.

--

Tutorial Review

Chem. Soc. Rev., 2008, 37, 2383 - 2392, DOI: 10.1039/b710347f
Current state for the development of metallopharmaceutics and anti-diabetic metal complexes

Hiromu Sakurai, Yutaka Yoshikawa and Hiroyuki Yasui
This tutorial review introduces the current state of metallopharmaceutics development by focusing on the topics of anti-diabetic vanadium and zinc complexes. Over thousands of years, people have produced many types of inorganic compounds, and the modern concept of chemotherapy was achieved by Ehrlich, who used an arsenic-containing compound to treat syphilis. Since then, many metallopharmaceutics have been developed worldwide. This review will be helpful to researchers who are interested in the current states of not only metallopharmaceutics but also anti-diabetic metal complexes.

--

Critical Review

Chem. Soc. Rev., 2008, 37, 2274 - 2309, DOI: 10.1039/b719149a
In-silico investigations in heterogeneous catalysis—combustion and synthesis of small alkanes

Oliver R. Inderwildi and Stephen J. Jenkins
In this critical review, we cover first-principles density functional calculations relevant to alkane oxidation and synthesis over transition metal catalysts. For oxidation, we focus upon Pt, Rh, Pd and Ni surfaces, while for synthesis we consider Co, Ru, Fe and Ni. Throughout, we emphasise the insight to be gained by thinking of each kind of reaction as the inverse of the other, with the directionality determined simply by the choice of metal catalyst and the reaction conditions. We highlight particularly the role of low-coordination sites (steps, kinks, etc.) and the emerging consensus over the importance of the formyl intermediate in facilitating the rate-determining step (249 references).

--

Editorial

Chem. Soc. Rev., 2008, 37, 2153 - 2154, DOI: 10.1039/b814437k
Chemistry at surfaces

Hans-Peter Steinrück, Jörg Libuda and Sir David A. King

--

Tutorial Review

Chem. Soc. Rev., 2008, 37, 2204 - 2211, DOI: 10.1039/b719206c
Automotive catalysis studied by surface science

Michael Bowker
In this tutorial review I discuss the significant impact that surface science has had on our understanding of the catalytic phenomena associated with automobile exhaust depollution catalysis. For oxidation reactions it has generally been found that reactions are self-poisoned at low temperatures by the presence of strongly adsorbed reactants (such as molecular CO and NO), and that the rapid acceleration in rate at elevated temperatures (often called light-off) is due to the desorption of such adsorbates, which then frees up sites for dissociation and hence for oxidation reactions. In some circumstances such autocatalytic phenomena can then manifest themselves as oscillatory reactions which can vary in rate in both space and time. For NO reduction, the efficiency of depollution (by production of molecular nitrogen) is strongly affected by the nature of the metal used. Rh is extremely effective because it can dissociate NO much more readily than metals such as Pd and Pt, enabling oxygen removal (by reaction with CO to CO2) even at room temperature. Rh is also very selective in producing predominantly N2, rather than N2O. NOx storage and reduction (NSR) is an important recent development for removal of NOx under the highly oxidising conditions of a lean-burn engine exhaust, and the strategy involves storing NOx on BaO under oxidising conditions followed by the creation of reducing conditions to de-store and reduce it to nitrogen. By the use of STM it has been shown that this storage process is extremely facile, occurring fast even under UHV conditions, and that the storage occurs on BaO in the vicinity of Pt, with most of the oxide being converted to nitrate.
--

Critical Review
Chem. Soc. Rev., 2008, 37, 2224 - 2242, DOI: 10.1039/b718768h
Oxide ultra-thin films on metals: new materials for the design of supported metal catalysts

Hans-Joachim Freund and Gianfranco Pacchioni
Ultrathin oxide films on metals offer new opportunities for the design of supported nanoclusters with potential use in catalysis. This requires a characterization at the atomistic level of the structure and composition of the thin film, of its morphology and defect structure. A proper selection of metal/oxide interface, film thickness, lattice mismatch, etc. makes it possible to prepare collections of supported metal particles with novel properties. This critical review describes some illustrative examples, emphasizes the role of the interplay between theory and experiment, and relates some recent findings related to the possibility to control the charge state of a supported nanoparticle on an ultrathin oxide film (211 references).

CMR: Concepts in NMR (Wiley) - up to Jan. 10, 2009

Concepts in NMR (Wiley) - up to Jan. 10, 2009

Concepts in Magnetic Resonance Part A
Volume 34A Issue 1, Pages 60 - 61
Published Online: 9 Jan 2009

2nd edition of Spin Dyanmics is now out, review is available on the CMR website!

Spin dynamics: Basics of nuclear magnetic resonance, 2nd edition.
William S. Price
Nanoscale Organisation and Dynamics Group, College of Health and Science, University of Western Sidney, Penrith South, Australia

--

Concepts in Magnetic Resonance Part A
Volume 32A Issue 6, Pages 417 - 435
Published Online: 17 Nov 2008

Nonuniform sampling: Bandwidth and aliasing
from Concepts in Magnetic Resonance Part A by G. Larry Bretthorst
For spectroscopic measurements, there are good reasons why one might consider using nonuniformly nonsimultaneously sampled complex data. The primary one is that the effective bandwidth, the largest spectral window free of aliases, can be much wider than with uniformly sampled data. In this article, we discuss nonuniformly nonsimultaneously sampled data, describe how these data are traditionally analyzed, analyze them using probability theory, and show how probability theory generalizes the discrete Fourier transform: first for uniformly sampled data, then for nonuniformly sampled data, and finally for nonuniformly nonsimultaneously sampled data. These generalizations demonstrate that aliases are not so much removed by nonuniform nonsimultaneous sampling as they are moved to much higher frequencies. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 417-435, 2008.

--

Concepts in Magnetic Resonance Part A
Volume 32A Issue 5, Pages 329 - 340
Published Online: 3 Sep 2008

Is quantum mechanics necessary for understanding magnetic resonance?
from Concepts in Magnetic Resonance Part A by Lars G. Hanson
Educational material introducing magnetic resonance (MR) typically contains sections on the underlying principles. Unfortunately the explanations given are often unnecessarily complicated or even wrong. MR is often presented as a phenomenon that necessitates a quantum mechanical explanation whereas it really is a classical effect, i.e. a consequence of the common sense expressed in classical mechanics. This insight is not new, but there have been few attempts to challenge common misleading explanations, so authors and educators are inadvertently keeping myths alive. As a result, new students' first encounters with MR are often obscured by explanations that make the subject difficult to understand. Typical problems are addressed and alternative intuitive explanations are provided. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 329-340, 2008.

Chem. Soc. Rev.: The Science of Champagne Bubbles

Just an article for fun...nice follow up to the previous Chem. Soc. Rev. article on wine.

Critical Review

Chem. Soc. Rev., 2008, 37, 2490 - 2511, DOI: 10.1039/b717798b

---

Recent advances in the science of champagne bubbles

Gérard Liger-Belair, Guillaume Polidori and Philippe Jeandet

---

The so-called effervescence process, which enlivens champagne and sparkling wines tasting, is the result of the fine interplay between CO₂-dissolved gas molecules, tiny air pockets trapped within microscopic particles during the pouring process, and some liquid properties. This critical review summarizes recent advances obtained during the past decade concerning the physicochemical processes behind the nucleation, rise, and burst of bubbles found in glasses poured with champagne and sparkling wines. Those phenomena observed in close-up through high-speed photography are often visually appealing. Lets hope that your enjoyment of champagne will be enhanced after reading this fully illustrated review dedicated to the deep beauties of nature often hidden behind many everyday phenomena (51 references).

Marcel's Update

J. Mater. Chem., 2008, 18, 4266 - 4273, DOI: 10.1039/b807778a

Detection of surface layers using 7Li MAS NMR

Nicolas Dupré, Jean-Frédéric Martin, Dominique Guyomard, Atsuo Yamada and Ryoji Kanno

Magic angle spinning solid state NMR is generally used to characterize bulk materials. We show here that it is also a promising tool to detect and characterize the diamagnetic surface layer on a paramagnetic material, which is a novel development. We apply this technique to the very hot topic of positive electrode/electrolyte characterization in the field of lithium rechargeable batteries. We report a 7Li MAS NMR study of physisorbed surface layers on LiNi1/2Mn1/2O2, a positive electrode material for lithium ion batteries. 7Li MAS NMR signals arising from surface layers formed by mixing the material with lithium carbonate or from contact of the material with ambient atmosphere, as well as with electrolyte are collected and analyzed. The progressive broadening of the line shape of the MAS NMR spectra reflects the increasing intimacy of the surface layer or secondary phase with the bulk material and therefore gives extremely useful complementary structural information on the surface not available using XPS or IR. We show that relaxation time measurements can be used as a probe of surface layers, allowing for discrimination of interphases from different origins. We propose a detailed analysis of the relaxation curves with a stretched exponential model allowing the description of the distribution of environments inside the surface layer. Our work indicates that MAS NMR can provide useful information for fine surface characterization of materials.

C&E News: MRI On The Nanoscale

from C&E News: http://pubs.acs.org/isubscribe/journals/cen/87/i03/html/8703scic1.html

"January 19, 2009
Volume 87, Number 03
p. 56
Science & Technology Concentrates
MRI On The Nanoscale
IBM scientists report the first nanometer-scale magnetic resonance imaging of a biological sample.
Celia Arnaud
IBM
An artist's rendering (left) shows the magnetic microscope tip (blue) interacting with virus particles (rods) on the end of a cantilever (yellow). The virus particles can also be viewed on the end of the cantilever in an SEM micrograph (right).
Scientists at IBM’s Almaden Research Center, in San Jose, Calif., report the first nanometer-scale magnetic resonance imaging of a biological sample. At such length scales, MRI could be used to image the three-dimensional structure of individual macromolecules and complexes, they note. Conventional MRI microscopy is limited to the micrometer scale. The IBM team, led by Dan Rugar, manager of nanoscale studies, improved the spatial resolution by combining magnetic resonance force microscopy (MRFM) with 3-D image reconstruction (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0812068106). MRFM is based on the mechanical measurement of ultrasmall magnetic forces between the nuclear spins in a sample and a nearby magnetic tip, which is scanned in three dimensions over the sample. The best spatial resolution previously achieved was 90 nm in 19F MRFM of inorganic samples. The IBM researchers extended the technology to biological samples and obtained 1H MRI images of tobacco mosaic virus particles with 4-nm resolution. Such a technique “would be complementary to other techniques, such as cryo-electron microscopy, and could develop into a powerful tool for structural biology,” the researchers write."

J Phys Chem C, vol 113, issues 2 and 3

Calculating the Concentration of SiOHAl Species in Ferrierites by 29Si and 27Al NMR Spectroscopy
Tamás I. Korányi*†‡ and János B.Nagy‡
J. Phys. Chem. C, 2009, 113 (3), pp 907–913

Abstract:Two NH4-ferrierites (NH4-FER) and their calcined H-FER forms with Si/Al ratios of 10 and 27.5 were characterized by 27Al and 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 27Al and 29Si NMR spectral resolutions of two NH4-FER samples with Si/Al = 8.4 and 30.0 were taken from the literature. The quantitative contributions of the Al sites, defect-free Si(nAl), and silanol groups to the different periodical building units (PerBUs) of the FER zeolite framework were calculated from the various Si/Al ratios and relative 27Al and 29Si NMR signal intensities. Two possible PerBU models and a dealumination route were suggested by the FER structure, and the distribution of PerBUs followed the composition of the framework with appropriate precision in the studied composition range (Si/Al = 8.4−30.0). The independently measured [Fourier transform infrared (FTIR) spectroscopy, NH3 temperature-programmed desorption (TPD)] extraframework aluminum (EFAl) concentrations and those measured by 27Al NMR spectroscopy were in a good agreement. The concentration of strong Brønsted acidic SiOHAl groups calculated with the SiOHAl PerBU model revealed that one-quarter to one-third of all OH groups were present in these SiOHAl sites in the ferrierites with Si/Al = 10 and one-half of them were in these sites in the NH4-FER sample with Si/Al = 27.5. The former zeolites were dealuminated at a higher degree than the latter. Tetrahedral aluminum species occupied the SiOHAl sites, and both deformed and octahedral Al species were present in the EFAl positions.

J Phys Chem B, vol 113, issues 2 and 3

Network Dynamics and Species Exchange Processes in Aluminophosphate Glasses: An in situ High Temperature Magic Angle Spinning NMR View
Sebastian Wegner†, Leo van Wüllen*† and Gregory Tricot†‡

J. Phys. Chem. B, 2009, 113 (2), pp 416–425
Abstract: In this contribution, we present an in situ high temperature 27Al and 31P magic angle spinning (MAS) NMR study of binary and ternary phosphate glasses at temperatures above the glass transition temperature TG. For binary phosphate glasses, xK2O−(1 − x)P2O5 and ternary aluminophosphate glasses 30K2O−xAl2O3−(70 − x)P2O5 with 7 < x < 15 dynamic exchange processes between the various phosphate species (and aluminate species) present in the glasses could be identified in the temperature range between TG and the maximum achievable temperature Tmax of our high temperature MAS NMR setup, TG < T < Tmax. This observation indicates rapid P−O−P and P−O−Al bond formation and bond breaking in the (alumino)phosphate glasses. From a modeling of the temperature dependence of these exchange processes, the activation energy EA for the corresponding process could be determined. These local bond breaking and making processes are ultimately linked to the macroscopic viscous flow and may indeed form the basic microscopic local step of viscous flow.

J Phys Chem C, v113, issue 1

Study of Aluminoborane Compound AlB4H11 for Hydrogen Storage
Ji-Cheng Zhao*†, Douglas A. Knight‡, Gilbert M. Brown‡, Chul Kim§, Son-Jong Hwang§, Joseph W. Reiter∥, Robert C. Bowman, Jr.∥, Jason A. Zan∥ and James G. Kulleck∥
J. Phys. Chem. C, 2009, 113 (1), pp 2–11

Aluminoborane compounds AlB4H11, AlB5H12, and AlB6H13 were reported by Himpsl and Bond in 1981, but they have eluded the attention of the worldwide hydrogen storage research community for more than a quarter of a century. These aluminoborane compounds have very attractive properties for hydrogen storage: high hydrogen capacity (i.e., 13.5, 12.9, and 12.4 wt % H, respectively) and attractive hydrogen desorption temperature (i.e., AlB4H11 decomposes at ∼125 °C). We have synthesized AlB4H11 and studied its thermal desorption behavior using temperature-programmed desorption with mass spectrometry, gas volumetric (Sieverts) measurement, infrared (IR) spectroscopy, and solid state nuclear magnetic resonance (NMR). Rehydrogenation of hydrogen-desorbed products was performed and encouraging evidence of at least partial reversibility for hydrogenation at relatively mild conditions is observed. Our chemical analysis indicates that the formula for the compound is closer to AlB4H12 than AlB4H11.



Solid-State 17O NMR Spectroscopy of Hydrous Magnesium Silicates: Evidence for Proton Dynamics
John M. Griffin†, Stephen Wimperis*‡, Andrew J. Berry§, Chris J. Pickard∥ and Sharon E. Ashbrook*†
J. Phys. Chem. C, 2009, 113 (1), pp 465–471
Abstract: First-principles calculations of 17O quadrupolar and chemical shift NMR parameters were performed using CASTEP, a density functional theory (DFT) code, to try and interpret high-resolution 17O NMR spectra of the humite group minerals hydroxyl-chondrodite (2Mg2SiO4·Mg(OH)2) and hydroxyl-clinohumite (4Mg2SiO4·Mg(OH)2), which are models for the incorporation of water within the Earth’s upper mantle. The structures of these humite minerals contain two possible crystallographically inequivalent H sites with 50% occupancy. Isotropic 17O multiple-quantum magic angle spinning (MQMAS) spectra were therefore simulated using the calculated 17O NMR parameters and assuming either a static or dynamic model for the positional disorder of the H atoms. Only the dynamic disorder model provided simulated spectra that agree with experimental 17O MQMAS spectra of hydroxyl-chondrodite and hydroxyl-clinohumite. Previously published 17O satellite-transition magic angle spinning (STMAS) spectra of these minerals showed significant dynamic line-broadenings in the isotropic frequency dimension. We were able to reproduce these line-broadenings with at least qualitative accuracy using a combination of the same dynamic model for the positional H disorder, calculated values for the change in 17O quadrupolar NMR parameters upon H exchange, and a simple analytical model for dynamic line-broadening in MAS NMR experiments. Overall, this study shows that a combination of state-of-the-art NMR methodology and first-principles calculations of NMR parameters is able to provide information on dynamic processes in solids with atomic-scale resolution that is unobtainable by any other method.

Chemical Physics, Volume 355, Issue 1, 7 January 2009, Pages 67-72

Relationship between calculated NMR data and intermolecular hydrogen bond properties in X-pyridineHF

Ali Ebrahimi, Mostafa Habibia, Hamid Reza Masoodia and Ali Reza Gholipoura


Abstract

The effect of different substituents in para and metapositions on the NMR data of X-pyridineHF complex has been studied at B3LYP/6-311++G(d,p) level of theory. The relationship between NMR data and electron donation of substituents has been investigated. The results of topological properties of electron charge density calculated using atoms in molecules (AIM) analysis can be used to predict some NMR data. The magnetism-based indices, nucleus independent chemical shift NICS(1) and its z component NICS(1)ZZ, were used to investigate the ring aromaticity changes on complexation. A linear correlation between Hammett coefficients and some NMR data could be found with a good correlation coefficient.

J. Am. Chem. Soc., 2009, 131 (1), pp 170–176

Structural Rearrangements of Membrane Proteins Probed by Water-Edited Solid-State NMR Spectroscopy
Christian Ader, Robert Schneider, Karsten Seidel‡, Manuel Etzkorn, Stefan Becker‡ and Marc Baldus

Abstract

We show that water-edited solid-state NMR spectroscopy allows for probing global protein conformation and residue-specific solvent accessibility in a lipid bilayer environment. The transfer dynamics can be well described by a general time constant, irrespective of protein topology and lipid environment. This approach was used to follow structural changes in response to protein function in the chimeric potassium channel KcsA-Kv1.3. Data obtained as a function of pH link earlier biochemical data to changes in protein structure in a functional bilayer setting.

J. Am. Chem. Soc., 2009, 131 (1), pp 118–128

Observation of a Low-Temperature, Dynamically Driven Structural Transition in a Polypeptide by Solid-State NMR Spectroscopy

Vikram S. Bajaj†, Patrick C.A. van der Wel‡ and Robert G. Griffin*

Abstract
At reduced temperatures, proteins and other biomolecules are generally found to exhibit dynamic as well as structural transitions. This includes a so-called protein glass transition that is universally observed in systems cooled between 200 and 230 K, and which is generally attributed to interactions between hydrating solvent molecules and protein side chains. However, there is also experimental and theoretical evidence for a low-temperature transition in the intrinsic dynamics of the protein itself, absent any solvent. Here, we use low-temperature solid-state NMR to examine site-specific fluctuations in atomic structure and dynamics in the absence of solvents. In particular, we employ magic angle spinning NMR to examine a structural phase transition associated with dynamic processes in a solvent-free polypeptide, N-f-MLF-OH, lattice at temperatures as low as 90 K. This transition is characterized by the appearance of an extra set of lines in 1D 15N spectra as well as additional cross peaks in 2D 13C−13C and 13C−15N spectra. Interestingly, the gradual, temperature-dependent appearance of the new spectral component is not accompanied by the line broadening typical of dynamic transitions. A direct comparison between the spectra of N-f-MLF-OH and the analog N-f-MLF-OMe, which does not display this transition, indicates a correlation of the structural transition to the temperature dependent motion of the aromatic phenylalanine side chain. Several quantitative solid state NMR experiments were employed to provide site-specific measurements of structural and motional features of the observed transition.

J. Am. Chem. Soc., 2009, 131 (1), pp 2–3

High-Resolution Double-Quantum Deuterium Magic Angle Spinning Solid-State NMR Spectroscopy of Perdeuterated Proteins

Vipin Agarwal†, Katja Faelber†, Peter Schmieder† and Bernd Reif*‡

Abstract

We show in this manuscript that 2H,13C correlation spectra in uniformly 2H,13C isotopically enriched peptides and proteins can be recorded in MAS solid-state NMR with site specific resolution. A resolved deuterium dimension is obtained by evolving 2H double-quantum coherences. Experimental 2H line widths are obtained that are as small as 16 Hz (0.17 ppm at 600 MHz) in the double-quantum dimension. The unprecedented resolution in the deuterium dimension obtained for proteins opens new perspectives for correlation experiments and, in particular, for the characterization of dynamics of proteins in the solid-state.

Bryan's Literature Update for January 8, 2009

Here comes the fun!

(Note the noteworthy submissions from Dr. Luke O'Dell in this wrap-up.)

These are the journals that were exhaustively combed (three times over. Honestly.) to procure the following entries:

Advanced Mater. (Wiley)
Chem. Phys. Lett. (Elsevier)
Chem. Commun. (RSC)
Dalton Trans. (RSC)

***

Chemical Physics Letters
Vol: 458, Issue: 4-6, June 17, 2008
pp. 368-372

Title: Intermolecular multiple-quantum coherences between spin 1/2 and quadrupolar nuclei in liquid nuclear magnetic resonance
Authors: Chen, S.; Cai, S.; Chen, Z.
Abstract (English): The features of the NMR signals from intermolecular multiple-quantum coherences between spin 1/2 and quadrupolar nuclei were investigated theoretically and experimentally.

***

Chemical Physics Letters
Vol: 458, Issue: 4-6, June 17, 2008
pp. 391-395

Title: Improving resolution in proton solid-state NMR by removing nitrogen-14 residual dipolar broadening
Authors: Stein, R.S.; Elena, B.; Emsley, L.
Abstract (English): Improved resolution is obtained for 1H solid-state NMR spectra by removing residual broadening due to interactions with neighboring 14N nuclei.

***

Chemical Physics Letters
Vol: 459, Issue: 1-6, June 27, 2008
pp. 188-193

Title: Solid-state single-scan 2D NMR under magic-angle-spinning
Authors: Gal, M.; Melian, C.; Demco, D.E.; Blumich, B.; Frydman, L.
Abstract (English): 2D NMR rubber spectrum collected within a single-scan (27ms total time) using a 2ms mixing time and magic-angle-spinning at 17kHz.

***

Chemical Physics Letters
Vol: 460, Issue: 1-3, July 20, 2008
pp. 278-283

Title: MIRROR recoupling and its application to spin diffusion under fast magic-angle spinning
Authors: Scholz, I.; Huber, M.; Manolikas, T.; Meier, B.H.; Ernst, M.
Abstract (English): A new second-order recoupling experiment under MAS NMR conditions is introduced. It allows measurement of proton-driven spin-diffusion spectra even at fast MAS conditions.

***

Chemical Physics Letters
Vol: 460, Issue: 4-6, July 30, 2008
pp. 531-535

Title: Simultaneous adiabatic spin-locking cross polarization in solid-state NMR of paramagnetic complexes
Authors: Peng, W.K.; Samoson, A.; Kitagawa, M.
Abstract (English): 13C NMR spectrum of Cu(II)(d,l-alanine)2.H2O, observed with different techniques, (a) SADIS cross polarization, (b) RAMP cross polarization, and (c) direct excitation of 13C. The signal-to-noise ratios (SNRs) are denoted besides its peaks.

***

Chemical Physics Letters
Vol: 461, Issue: 1-3, August 8, 2008
pp. 33-37

Title: From correlation-consistent to polarization-consistent basis sets estimation of NMR spin-spin coupling constant in the B3LYP Kohn-Sham basis set limit
Author: Kupka, T.
Abstract (English): Based on recently B3LYP calculated spin-spin coupling constants (SSCC) of several small molecules with cc-pVxZ, cc-pCVxZ, cc-pCVxZ-sd and cc-pCVxZ-sd+t basis sets, a reasonably fit, using the two-parameter formula, to the complete basis set limit (CBS) is shown. Calculation of water's ^1J(OH) using B3LYP/cc-pCVxZ and B3LYP/pcJ-n significantly improved the FC term and its total convergence.

***

Chemical Physics Letters
Vol: 462, Issue: 1-3, September 1, 2008
pp. 125-128

Title: Quantification of cross polarization with relaxation compensated reciprocity relation in NMR
Authors: Shu, J.; Chen, Q.; Zhang, S.
Abstract (English): Computer simulated reciprocity relation between the dynamics of cross polarization (CP) and cross depolarization (CDP) for a powder sample under fast magic angle spinning (MAS=40kHz). The symmetrical pattern between CP(t) and CDP(t) manifests the quantification of cross polarization under fast MAS. In the simulation, the dipolar coupling constant for a 1H-13C spin pair is d=25.37kHz and the RF spin-locking fields f1I and f1S are 140 and 100kHz, respectively.

***


Chemical Physics Letters
Vol: 463, Issue: 4-6, October 1, 2008
pp. 418-421

Title: Determination of transverse relaxation rates of individual spins while quenching echo modulations due to homonuclear scalar couplings
Authors: Aeby, N.; Bodenhausen, G.
Abstract (English): When spin-echo modulations are quenched, individual transverse relaxation rate constants R2(I)=1/T2(I) can be determined for each spin I individually site by site.

***

Chemical Physics Letters
Vol: 464, Issue: 1-3, October 13, 2008
pp. 97-102

Title: QCPMG using adiabatic pulses for faster acquisition of ultra-wideline NMR spectra
Authors: O'Dell, L.A.; Schurko, R.W.
Abstract (English): A QCPMG-like pulse sequence utilizing adiabatic (WURST) pulses. This sequence allows broadband excitation of ultra-wideline solid-state NMR spectra, combined with a significant increase in signal per scan. The sequence has been successfully used to acquire 71Ga and 91Zr spectra over 500kHz in width without any frequency or field adjustment. It can also be used to observe satellite transitions.

***

Chemical Physics Letters
Vol: 464, Issue: 1-3, October 13, 2008
pp. 42-48

Title: New perspectives on calcium environments in inorganic materials containing calcium-oxygen bonds: A combined computational-experimental ^4^3Ca NMR approach
Authors: Gervais, C.; Laurencin, D.; Wong, A.; Pourpoint, F.; Labram, J.; Woodward, B.; Howes, A.P.; Pike, K.J.; Dupree, R.; Mauri, F.; Bonhomme, C.; Smith, M.E.
Abstract (English): The potential of a combined experimental-computational 43Ca solid state NMR approach for the structural analysis of inorganic compounds is presented.

***

Chemical Physics Letters
Vol: 464, Issue: 4-6, October 23, 2008
pp. 235-239

Title: Irreducible spherical tensor analysis of quadrupolar nuclei
Authors: Chandra Shekar, S.; Rong, P.; Jerschow, A.
Abstract (English): Selection of a specific spherical tensor term from the density matrix of a spin=7/2 particle, demonstrated experimentally as a function of evolution time.

***

Chemical Physics Letters
Vol: 466, Issue: 1-3, November 24, 2008
pp. 95-99

Title: Homonuclear dipolar decoupling at magic-angle spinning frequencies up to 65kHz in solid-state nuclear magnetic resonance
Authors: Leskes, M.; Steuernagel, S.; Schneider, D.; Madhu, P.K.; Vega, S.
Abstract (English): Experimental aspects of the implementation of homonuclear dipolar decoupling schemes for 1H spectroscopy in solid-state NMR at high magic-angle spinning frequencies of up to 65kHz are demonstrated.

***

Chemical Physics Letters
Vol: 466, Issue: 4-6, December 4, 2008
pp. 227-234

Title: Application of static microcoils and WURST pulses for solid-state ultra-wideline NMR spectroscopy of quadrupolar nuclei
Authors: Tang, J.A.; O'Dell, L.A.; Aguiar, P.M.; Lucier, B.E.G.; Sakellariou, D.; Schurko, R.W.
Abstract (English): The uses of microcoils and WURST pulses for acquiring ultra-wideline (UW) NMR spectra of half-integer quadrupolar nuclei are explored.

***

Chemical Physics Letters
Vol: 466, Issue: 4-6, December 4, 2008
pp. 247-251

Title: Efficient heteronuclear decoupling by quenching rotary resonance in solid-state NMR
Authors: Weingarth, M.; Tekely, P.; Bodenhausen, G.
Abstract (English): We propose efficient heteronuclear decoupling by quenching rotary resonance in fast MAS solid-state NMR

***

Chem. Commun.
2008, 5568 - 5570,
DOI: 10.1039/b812928b


Title: Quantifying the fraction of glycine and alanine in -sheet and helical conformations in spider dragline silk using solid-state NMR

Authors: Gregory P. Holland, Janelle E. Jenkins, Melinda S. Creager, Randolph V. Lewis and Jeffery L. Yarger

Abstract: Solid-state two-dimensional refocused INADEQUATE MAS NMR experiments resolve distinct helical and -sheet conformational environments for both alanine and glycine in Nephila clavipes dragline silk fibers; the fraction of alanine and glycine in -sheet structures is determined to be 82% ± 4% and 28% ± 5%, respectively.

***

Chem. Commun.
2008, 5722 - 5724
DOI: 10.1039/b812905c

Title: Deuterated polymer gels for measuring anisotropic NMR parameters with strongly reduced artefacts

Authors: Grit Kummerlöwe, Sebastian Knör, Andreas O. Frank, Thomas Paululat, Horst Kessler and Burkhard Luy

Abstract: Perdeuterated poly(styrene) is introduced as an almost artefact-free and arbitrarily scalable alignment medium for measuring residual dipolar couplings and other anisotropic NMR parameters; the spectral quality achievable in this new medium is demonstrated for HSQC spectra leading to the conformational analysis of staurosporine and homonuclear TOCSY-type experiments.

***

Chem. Commun.
2008, 5933 - 5935
DOI: 10.1039/b814326a

Title: Solid-state 115In NMR study of indium coordination complexes

Authors: Fu Chen, Guibin Ma, Ronald G. Cavell, Victor V. Terskikh and Roderick E. Wasylishen

Abstract: The feasibility of solid-state 115In NMR studies is demonstrated by an examination of four different coordination complexes: indium(III) acetylacetonate, indium(III) tris(tropolonato), indium(III) triiodide bis(tris(4-methoxyphenyl)phosphine oxide) and indium(III) trichloride tris(2,4,6-trimethoxyphenyl)phosphine. The results provide information about the electric field gradients and magnetic shielding at the indium nuclei through the nuclear quadrupolar and chemical shift parameters, respectively. The CQ values in these four complexes range between 106.0 ± 2.0 and 200.0 ± 4.0 MHz, while the magnetic shielding anisotropies fall in the range from 85 ± 15 to 550 ± 60 ppm. Finally, this research demonstrates that solid-state 115In NMR studies are facilitated by performing experiments at the highest possible magnetic-field strengths, and that NMR offers a promising tool for the characterization of indium compounds.

***

Chem. Commun.
2008, 5981 - 5983
DOI: 10.1039/b813237b

Title: Revealing molecular self-assembly and geometry of non-covalent halogen bonding by solid-state NMR spectroscopy

Authors: Markus Weingarth, Noureddine Raouafi, Benjamin Jouvelet, Luminita Duma, Geoffrey Bodenhausen, Khaled Boujlel, Bernd Schöllhorn and Piotr Tekely

Abstract: We report a new spectroscopic fingerprint of intermolecular contacts in halogen bond-driven self-assembling aggregates and a precise determination of intermolecular NI distances in microcrystalline samples.

***

Chem. Commun.
2009, 186 - 188
DOI: 10.1039/b817017g

Title: A natural abundance 33S solid-state NMR study of layered transition metal disulfides at ultrahigh magnetic field

Authors: Andre Sutrisno, Victor V. Terskikh and Yining Huang

Abstract: Using a series of layered transition metal disulfides we demonstrate that the wide-line natural abundance solid-state NMR spectra of 33S in a less symmetric environment can readily be obtained at ultrahigh magnetic field of 21.1 T and that surprisingly these closely related materials display a wide range of 33S quadrupole coupling constant and chemical shift anisotropy values.

***

Dalton Trans.
2008, 3723 - 3728
DOI: 10.1039/b802496k


Title: Structural, 197Au Mössbauer and solid state 31P CP/MAS NMR studies on bis (cis-bis(diphenylphosphino)ethylene) gold(I) complexes [Au(dppey)2]X for X = PF6, I

Authors: Peter C. Healy, Bradley T. Loughrey, Graham A. Bowmaker and John V. Hanna

Abstract: 197Au Mössbauer spectra for the d10 gold(I) phosphine complexes, [Au(dppey)2]X (X = PF6, I; dppey = (cis-bis(diphenylphosphino)ethylene), and the single crystal X-ray structure and solid state 31P CPMAS NMR spectrum of [Au(dppey)2]I are reported here. In [Au(dppey)2]I the AuP4 coordination geometry is distorted from the D2 symmetry observed for the PF6- complex with Au–P bond lengths 2.380(2)–2.426(2) Å and inter-ligand P–Au–P angles 110.63(5)–137.71(8)̊. Quadrupole splitting parameters derived from the Mössbauer spectra are consistent with the increased distortion of the AuP4 coordination sphere with values of 1.22 and 1.46 mm s-1 for the PF6- and I- complexes respectively. In the solid state 31P CP MAS NMR spectrum of [Au(dppey)2]I, signals for each of the four crystallographically independent phosphorus nuclei are observed, with the magnitude of the 197Au quadrupole coupling being sufficiently large to produce a collapse of 1J(Au–P) splitting from quartets to doublets. The results highlight the important role played by the counter anion in the determination of the structural and spectroscopic properties of these sterically crowded d10 complexes.

***

Dalton Trans.
2008, 3782 - 3790
DOI: 10.1039/b719526e

Title: Perspectives in paramagnetic NMR of metalloproteins

Authors: Ivano Bertini, Claudio Luchinat, Giacomo Parigi and Roberta Pierattelli

Abstract: NMR experiments and tools for the characterization of the structure and dynamics of paramagnetic proteins are presented here. The focus is on the importance of 13C direct-detection NMR for the assignment of paramagnetic systems in solution, on the information contained in paramagnetic effects observed both in solution and in the solid state, and on novel paramagnetism-based tools for the investigation of conformational heterogeneity in protein–protein complexes or in multi-domain proteins.

***

Dalton Trans.
2008, 4965 - 4974
DOI: 10.1039/b803510p

Title: Nitrogen-15 NMR spectroscopy of N-metallated nucleic acids: insights into 15N NMR parameters and N–metal bonds

Authors: Yoshiyuki Tanaka and Akira Ono

Abstract: It was recently demonstrated spectroscopically that RNA/DNA nucleobases can bind to metal cations in aqueous solution through coordination bonds and covalent bonds. Nitrogen-15 (15N) NMR spectroscopy was employed and shown to be a powerful tool for determining the mode of metal ion binding to nitrogen atoms in RNA/DNA molecules. This review describes 15N NMR spectroscopic characteristics in accordance with the mode of metal ion binding to nitrogen atoms. The general rules for 15N chemical shift changes, which are applicable to the determination of the metal ion binding mode of N-metallated compounds, are also described.

***

Dalton Trans.
2008, 5296 - 5301
DOI: 10.1039/b809062a

Title: Effect of oxygen content on the 29Si NMR, Raman spectra and oxide ion conductivity of the apatite series, La8+xSr2-x(SiO4)6O2+x/2

Authors: A. Orera, E. Kendrick, D. C. Apperley, V. M. Orera and P. R. Slater

Abstract: 29Si NMR data have been recorded for the apatite series La8+xSr2-x(SiO4)6O2+x/2 (0 x 1.0). For x = 0, a single NMR peak is observed at a chemical shift of -77 ppm, while as the La:Sr ratio and hence interstitial oxygen content is increased, a second peak at a chemical shift of -80 ppm is observed, which has been attributed to silicate groups neighbouring interstitial oxide ions. An increase in the intensity of this second peak is observed with increasing x, consistent with an increase in interstitial oxide ion content, and the data are used to estimate the level of interstitial oxide ions, and hence Frenkel-type disorder in these materials. The increase in second 29Si NMR peak intensity/interstitial oxide ion content is also shown to correlate with an increase in conductivity. The effect of interstitial oxygen content can also be studied by means of Raman spectroscopy, with a new mode at 360 cm-1 appearing for samples with x > 0 in the symmetric bending mode energy region of the SiO4 group. The intensity of this mode increases with increasing oxygen content, yielding results comparable to those from the NMR studies, showing the complementarities of the two techniques.

***

Dalton Trans.
2008, 6150 - 6158
DOI: 10.1039/b810863c

Title: Structure determination of -Pb2ZnF6 by coupling multinuclear solid state NMR, powder XRD and ab initio calculations

Authors: Charlotte Martineau, Franck Fayon, Christophe Legein, Jean-Yves Buzaré, Monique Body, Dominique Massiot and François Goutenoire

Abstract: The results from one-dimensional multinuclear (19F, 207Pb and 67Zn) magic-angle spinning nuclear magnetic resonance experiments combined with the use of the ISODISPLACE program allow for the space group determination of -Pb2ZnF6 (no. 138 P42/ncm). The structure was refined from X-ray powder diffraction data (a = 5.633 (1) and c = 16.247 (1) , Z = 4). -Pb2ZnF6 has one six-fold coordinated Zn, one eleven-fold coordinated Pb and five F non-equivalent crystallographic sites and is built from alternated layers parallel to the (a, b) plane; tilted ZnF42- layers of corner sharing ZnF64- octahedra and FPb+ layers of edge sharing FPb47+ tetrahedra. The structure of -Pb2ZnF6 was then optimized using the ab initio code WIEN2k and the calculated 67Zn EFG is in agreement with the NMR results. 19F–19F proximities and 19F–207Pb connectivities were evidenced using through-space and through-bond NMR correlation experiments, respectively, and support the proposed structure. 19F–207Pb J-coupling was also used to select fluorine resonances depending on the number of neighbouring lead ions, leading to an unambiguous assignment of the different 19F resonances.

***

Macromolecules August 2008 (Volume 41, Issue 16) to January 2009 (Volume 42, Issue 1)

Segmental Dynamics of Bulk Poly(vinyl acetate)-d3 by Solid-State 2H NMR: Effect of Small Molecule Plasticizer

Rakesh R. Nambiar† and Frank D. Blum*‡
Macromolecules, 2008, 41 (24), pp 9837–9845

Abstract: The effect of dipropyleneglycol dibenzoate, a plasticizer, on the glass-transition temperature (Tg) of poly(vinyl acetate) was studied using deuterium solid-state NMR and modulated differential scanning calorimetry (MDSC) from 0 to 20% plasticizer content. Quadrupole-echo 2H NMR spectra were obtained for methyl deuterated PVAc-d3 samples with different plasticized amounts. The Tgʼs of different plasticized samples were determined from NMR as the temperatures at which the deuterium powder patterns collapsed. It was found that the Tgʼs decreased by approximately 6 °C for every 5% increment in the plasticizer content and that the trends in the NMR-determined Tgʼs, that is, Tg(NMR), were consistent with those determined by modulated differential scanning calorimetry (MDSC). The Tg(NMR) values were about 36 °C above those of the Tg(DSC) values. This difference in the Tgʼs was due to the different time scales of the two experiments which could be accounted for on the basis of time−temperature superposition principles. The experimental NMR line shapes were fitted using a set of simulated spectra generated from the MXQET simulation program. The spectra were based on a model of nearest-neighbor jumps on a truncated icosahedron (soccer ball). The resulting average correlation times were also found to fit a time−temperature superposition with the same parameter. While the Tg was decreased by the amount of plasticizer, it was found that the breadth of the transitions from either the NMR line shapes or the MDSC thermograms did not seem to change much with the amount of added plasticizer.



Segmental Dynamics of Poly(ethylene oxide) Chains in a Model Polymer/Clay Intercalated Phase: Solid-State NMR Investigation

Cédric Lorthioir*†, Françoise Lauprêtre†, Jérémie Soulestin‡ and Jean-Marc Lefebvre‡

Macromolecules, 2009, 42 (1), pp 218–230
DOI: 10.1021/ma801909s
Abstract: A model poly(ethylene oxide) (PEO)/laponite hybrid material, characterized by a high silicate content, was used to probe the dynamical behavior of polymer chains at the surface with clay platelets. Such a system mimics the intercalated phases that may occur in polymer/clay nanocomposites with usual silicate amounts of 5 wt %. The segmental motions underlying the α-relaxation of fully amorphous PEO chains confined within the nanometer-thick laponite galleries were monitored over the tens of microseconds time scale by means of 13C and 1H solid-state NMR. A significant slowing down of these motions was mostly observed, as compared to the local dynamics in the amorphous phase of neat PEO. Strong dynamical heterogeneities among the intercalated PEO monomer units remain even at room temperature, i.e., more than 50 K above the temperature at which the frequency of the segmental motions displayed by a significant part of the PEO chain segments gets above 52 kHz. Such heterogeneities are related to a pronounced extension of the α-relaxation process toward the low-frequency side. The slowing down of the PEO segmental motions was assigned to ion-dipole interactions between the PEO oxygen atoms and the Na+ counterions located in the laponite galleries. The domains formed by PEO monomer units characterized by a reduced segmental mobility were found to display rather long lifetime, about 13 ms at room temperature.




2H NMR Studies of Polymer Multilayer Capsules, Films, and Complexes

Blythe Fortier-McGill and Linda Reven*

Macromolecules, 2009, 42 (1), pp 247–254
DOI: 10.1021/ma801929g
Abstract: The chain dynamics of aqueous suspensions of polyelectrolyte complexes, supported multilayers deposited on submicron silica colloids, and hollow capsules were characterized by wide-line 2H NMR spectroscopy (DNMR) as a function of layer number, temperature, and ionic strength. The strong polyelectrolytes, poly(diallyldimethyl ammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS) were employed with selective deuteration of the PDADMAC methyl group. DNMR line-shape analyses showed that there is enhanced chain mobility in the systems with excess positive monomer units, that is, supported multilayers and capsules capped with PDADMAC. Selective deuteration of the first, fifth, and ninth layers confirms that the alternation in chain mobility with the capping layer is a through-film effect. Differential scanning calorimetry (DSC)-detected phase transitions were found to occur between 32 and 45 °C for the PSS/PDADMAC complexes, supported multilayers, and capsules. Whereas the glass transitions of bulk-state polymers are detected by DNMR typically 30 to 40° above the DSC-detected Tg, the onset of fast chain motion for the water-saturated polyelectrolyte complexes and supported multilayers coincides with calorimetric transitions.




Anisotropic Diffusion and Morphology in Perfluorosulfonate Ionomers Investigated by NMR

Jing Li, Kyle G. Wilmsmeyer and Louis A. Madsen*

Macromolecules, 2009, 42 (1), pp 255–262
DOI: 10.1021/ma802106g

Abstract:Anisotropy in ionomer membranes represents a powerful interaction for modulating properties such as mechanical moduli, thermal expansions, and small molecule transport, all tunable via controlled processing. We observe uniform hydrophilic channel alignment in three perfluorosulfonate ionomer membrane types, quantified by 2H NMR spectroscopy of absorbed D2O molecules. Our measurements show biaxial or uniaxial in-plane alignment for extruded membranes, but uniaxial through-plane alignment for dispersion-cast membranes, and further demonstrate affine swelling with both water uptake and thermal expansion. In order to correlate alignment data with a quantity relevant to proton transport, we measure the anisotropy of water self-diffusion using pulsed-field-gradient NMR along different membrane directions. Extruded membranes with stronger alignment exhibit 18% faster in-plane diffusion than through-plane diffusion, while diffusion anisotropy is minimal for weakly aligned membranes. These results should lead to a more quantitative understanding of and control over membrane properties via manipulation of molecular order.

Chem. Mater., Article ASAP

Sc2(WO4)3 and Sc2(MoO4)3 and Their Solid Solutions: 45Sc, 17O, and 27Al MAS NMR Results at Ambient and High Temperature

Namjun Kim* and Jonathan F. Stebbins

Abstract

The mobilities of trivalent ions are generally considered to be low in solid oxides and thus trivalent ionic conductors are rare. Sc2(WO4)3 and related compounds have been described as Sc3+ ionic conductors. However, there has not been conclusive experimental evidence whether Sc3+ is the major or the only mobile species. Here, we report 45Sc, 17O, and 27Al MAS NMR studies at ambient and high temperature of Sc2(WO4)3-type compounds including Sc2(WO4)3, Sc2(MoO4)3 (scandium tungstate and scandium molybdate), and their solid solutions, as well as aluminum-doped Sc2(WO4)3. 45Sc MAS NMR spectra at ambient temperature of the Sc2(WO4)3−Sc2(MoO4)3 binary are consistent with random mixing of W6+ and Mo6+ on tetrahedral sites. 17O spectra show that the details of the end-member short-range structure are preserved throughout this solid solution, indicating that lattice distortion is minimized by the close similarity of the radii of the hexavalent cations. Al3+ substitutes only into the octahedral sites. At high temperatures (600−700 °C), only the 17O high spectra show noticeable line shape changes, whereas 45Sc high-temperature spectra maintain a constant peak width and shift in position only, suggesting that the oxide anion may be a more mobile species but not excluding the possibility of a minor number of mobile scandium ions. 17O high-temperature NMR data also suggest that oxide ions bonded to molybdenum ions may be more mobile than those in tungstate groups.

Cryst. Growth Des., Article ASAP

Solid-State NMR Analysis of Organic Cocrystals and Complexes

Frederick G. Vogt*†, Jacalyn S. Clawson†, Mark Strohmeier†, Andrew J. Edwards‡, Tran N. Pham‡ and Simon A. Watson‡

Abstract

Solid-state NMR (SSNMR) is capable of providing detailed structural information about organic and pharmaceutical cocrystals and complexes. SSNMR nondestructively analyzes small amounts of powdered material and generally yields data with higher information content than vibrational spectroscopy and powder X-ray diffraction methods. These advantages can be utilized in the analysis of pharmaceutical cocrystals, which are often initially produced using solvent drop grinding techniques that do not lend themselves to single crystal growth for X-ray diffraction studies. In this work, several molecular complexes and cocrystals are examined to understand the capabilities of the SSNMR techniques, particularly their ability to prove or disprove molecular association and observe structural features such as hydrogen bonding. Dipolar correlation experiments between spin pairs such as 1H−1H, 1H−13C, and 19F−13C are applied to study hydrogen bonding, intermolecular contacts, and spin diffusion to link individual molecules together in a crystal structure and quickly prove molecular association. Analysis of the principal components of chemical shift tensors is also utilized where relevant, as these are more sensitive to structural effects than the isotropic chemical shift alone. In addition, 1H T1 relaxation measurements are also demonstrated as a means to prove phase separation of components. On the basis of these results, a general experimental approach to cocrystal analysis by SSNMR is suggested.

J. Phys. Chem. C vol. 112, iss. 51

Two Kinds of Framework Al Sites Studied in BEA Zeolite by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, NMR Techniques, and V Probe

Redouane Hajjar†‡, Yannick Millot*†‡, Pascal P. Man†‡, Michel Che§∥⊥ and Stanislaw Dzwigaj*§∥

J. Phys. Chem. C, 2008, 112 (51), pp 20167–20175

Abstract: The dealumination of BEA zeolite by treatment with concentrated nitric acid is evidenced by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Two-dimensional 27Al 3Q and 5Q magic-angle-spinning (MAS) NMR allow the detection of two kinds of tetrahedral Al atoms whose relative amounts depend on the Si/Al ratio and which correspond to two specific T-sites. 29Si MAS NMR and 1H MAS NMR measurements confirm these results. 29Si MAS NMR spectra evidence two resonances at around −114 and −111 ppm ascribed to Si sites of the Si(OSi)4 environment of two different crystallographic sites. Moreover, the presence of Si atoms associated with hydroxyl groups is confirmed by a resonance at −102 ppm when 1H−29Si CP is applied. The Brønsted and Lewis acidic sites in dealuminated BEA zeolites are evidenced by FTIR spectra of adsorbed pyridine which show two kinds of bridging hydroxyl groups (Si−O(H)−Al) of different acid strength. 51V MAS NMR confirms the incorporation of vanadium atoms into vacant T-atom sites of a fully dealuminated SiBEA zeolite leading to two kinds of tetrahedral V(V) sites (δiso = – 708 and – 766 ppm), with a V=O double bond and linked by V−OSi bonds to the framework. The two types of tetrahedral V(V) sites are in line with the two kinds of tetrahedral Al sites initially present in the zeolite. Moreover, the two bands at 3620 and 3645 cm−1 suggest that VSiBEA also contains V(V) sites with V(V)O−H groups, which exhibit Brønsted acidic character as shown by FTIR of adsorbed pyridine. Possible ways for the formation of tetrahedral V(V) in the BEA structure are proposed.





Direct Correlation between the 31P MAS NMR Response and the Electronic Structure of Some Transition Metal Phosphides
E. Bekaert†, J. Bernardi‡, S. Boyanov‡, L. Monconduit‡, M.-L. Doublet*‡ and M. Ménétrier*†

J. Phys. Chem. C, 2008, 112 (51), pp 20481–20490

Abstract: A series of binary transition metal phosphides (Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, FeP, FeP2, FeP4, VP2, CoP) were investigated by solid state 31P MAS NMR, leading to rather different lineshapes, shifts, relaxation times, and temperature dependences. The electronic structures of these compounds were computed using various DFT codes, based either on plane wave PAW potentials (VASP) or on all-electron basis sets in the FPLAPW formalism (Wien2K). Depending on the electronic features of the phosphide, self-interaction corrected formalisms (DFT+U or PBE0 hybrid functional) were also used to reach a better description of the electronic ground state and to establish a correlation with the shape and the nature of the NMR signals. As a result of the analysis, the main categories are diamagnetic compounds (FeP4, NiP2) and metallic ones, either real (VP2) or with some electronic localization in band tails (Ni12P5, Ni2P, Ni5P4, NiP) or with spin-polarized conduction bands (CoP, FeP). FeP2 appears somewhat ambiguous, both based on the various computational results and on the NMR characteristics. Besides, FeP4 is the only compound for which very clear J couplings resulting from P−P bonds were observed

J. Phys Chem B Vol 112, Issue 51

Dynamic Solvophobic Effect and Its Cooperativity in the Hydrogen-bonding Liquids Studied by Dielectric and Nuclear Magnetic Resonance Relaxation

Tsuyoshi Yamaguchi*, Hiroki Furuhashi, Tatsuro Matsuoka and Shinobu Koda

J. Phys. Chem. B, 2008, 112 (51), pp 16633–16641
Abstract: The reorientational relaxation of solvent molecules in the mixture of nonpolar solutes and hydrogen-bonding liquids including water, alcohols, and amides are studied by dielectric and 2H-nuclear magnetic resonance (NMR) spin−lattice relaxations. The retardation of the reorientational motion of the solvent by weak solute−solvent interaction is observed in all the solvent systems. On the other hand, no clear correlation between the strength of the solute−solvent interaction and the slowing down of the solvent motion is found in N,N-dimethylacetamide, which suggests the importance of the hydrogen bonding in the dynamic solvophobic effect. The cooperativity of the reorientational relaxation is investigated by the comparison between the collective relaxation measured by the dielectric spectroscopy and the single-molecular reorientation determined by NMR. The modification of the dielectric relaxation time caused by the dissolution of the solute is larger than that of the single-molecular reorientational relaxation time in all the solvents studied here. The effect of the static correlation between the dipole moments of different molecules is calculated from the static dielectric constant, and the effect of the dynamic correlation is estimated. The difference in the effects of the solutes on the collective and single-molecular reorientational relaxation is mainly ascribed to the dynamic cooperativity in the cases of water and alcohols, which is consistent with the picture on the dynamic solvophobicity derived by our previous theoretical analysis (Yamaguchi, T.; Matsuoka, T.; Koda, S. J. Chem. Phys. 2004, 120, 7590). On the other hand, the static correlation plays the principal role in the case of N-methylformamide.



Richard Weber*†‡, Sabyasachi Sen§, Randall E. Youngman∥, Robert T. Hart⊥ and Chris J. Benmore‡

J. Phys. Chem. B, 2008, 112 (51), pp 16726–16733
DOI: 10.1021/jp807964u

Abstract: The structure of binary aluminosilicate glasses containing 60−67 mol % Al2O3 were investigated using high-resolution 27Al NMR and X-ray and neutron diffraction. The glasses were made by aerodynamic levitation of molten oxides. The 67% alumina composition required a cooling rate of ∼1600 °C s1− to form glass from submillimeter sized samples. NMR results show that the glasses contain aluminum in 4-, 5-, and 6-fold coordination in the approximate ratio 4:5:1. The average Al coordination increases from 4.57 to 4.73 as the fraction of octahedral Al increases with alumina content. The diffraction results on the 67% composition are consistent with a disordered Al framework with Al ions in a range of coordination environments that are substantially different from those found in the equilibrium crystalline phases. Analysis of the neutron and X-ray structure factors yields an average bond angle of 125 ± 4° between an Al ion and the adjoining cation via a bridging oxygen. We propose that the structure of the glass is a “transition state” between the alumina-rich liquid and the equilibrium mullite phase that are dominated by 4- and 6-coordinated aluminum ions, respectively.



Ultrahigh Resolution Characterization of Domain Motions and Correlations by Multialignment and Multireference Residual Dipolar Coupling NMR

Charles K. Fisher, Qi Zhang, Andrew Stelzer and Hashim M. Al-Hashimi*
J. Phys. Chem. B, 2008, 112 (51), pp 16815–16822
DOI: 10.1021/jp806188j

Abstract: Nuclear magnetic resonance (NMR) residual dipolar couplings (RDCs) provide a unique opportunity for spatially characterizing complex motions in biomolecules with time scale sensitivity extending up to milliseconds. Up to five motionally averaged Wigner rotation elements, ⟨D0k2(αβ)⟩, can be determined experimentally using RDCs measured in five linearly independent alignment conditions and applied to define motions of axially symmetric bond vectors. Here, we show that up to 25 motionally averaged Wigner rotation elements, ⟨Dmk2(αβγ)⟩, can be determined experimentally from multialignment RDCs and used to characterize rigid-body motions of chiral domains. The 25 ⟨Dmk2(αβγ)⟩ elements form a basis set that allows one to measure motions of a domain relative to an isotropic distribution of reference frames anchored on a second domain (and vice versa), thus expanding the 3D spatial resolution with which motions can be characterized. The 25 ⟨Dmk2(αβγ)⟩ elements can also be used to fit an ensemble consisting of up to eight equally or six unequally populated states. For more than two domains, changing the identity of the domain governing alignment allows access to new information regarding the correlated nature of the domain fluctuations. Example simulations are provided that validate the theoretical derivation and illustrate the high spatial resolution with which rigid-body domain motions can be characterized using multialignment and multireference RDCs. Our results further motivate the development of experimental approaches for both modulating alignment and anchoring it on specifically targeted domains.




Structure, Orientation, and Dynamics of the C-Terminal Hexapeptide of LRAP Determined Using Solid-State NMR

Wendy J. Shaw* and Kim Ferris
J. Phys. Chem. B, 2008, 112 (51), pp 16975–16981
DOI: 10.1021/jp808012g

Abstract: Amelogenin is the predominant protein found during enamel development and has been shown to be essential to proper enamel formation. Leucine-rich amelogenin peptide (LRAP) is a naturally occurring splice variant that preserves the charged N- and C-termini of full length amelogenin, regions thought to be crucial in interacting with hydroxaypatite. Particularly, the highly charged C-terminal hexapeptide (KREEVD) is thought to be the region most intimately interacting with hydroxyapatite (HAP). The structure of this charged region was investigated, along with the proximity to the surface and the mobility of two of the residues. The structure was found to be consistent with a random coil or more extended structure, as has been seen for more internalized residues in the C-terminus. The backbone K54(13C′), V58(13C′), and V58(15N) were all found to be close to the surface of HAP, ∼ 6.0 Å from the nearest 31P atom, suggesting a strong interaction and emphasizing the importance of these residues in interacting with HAP. However, both ends of the hexapeptide at residues K54 and V58 experience significant mobility under hydrated conditions, implying that another portion of the protein helps to stabilize the strong LRAP-HAP interaction. Interestingly, the backbone of the C-terminal third of the protein is consistently 6.0 Å from the HAP surface, providing a model in this region of the protein lying flat on the surface with no three-dimensional folding. The combination of these features, that is, a random coil structure, a significant mobility, and a lack of three-dimensional folding in this region of the protein, may have an important functional role, possibly allowing maximum crystal inhibition at low protein concentrations.