Bryan's Literature Update up to June 4th, 2008

What follows is all the news fit to print on NMR since the last time I had the pleasure of communicating to the masses on March 31, 2008.

Fun game: Spot the paper by the current post-doctoral fellow in Rob Schurko's group! (It's really fun!)

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Chemical Physics
Vol: 345, Issue: 1, April 3, 2008
pp. 116-118

Title: The relationship between crystal structure and NMR relaxation in molecular solids with tert-butyl groups

Authors: Rheingold, A.L.; DiPasquale, A.G.; Beckmann, P.A.

Keywords: Solid state NMR; NMR relaxation; Molecular solids; Intramolecular motion; X-ray diffraction

Abstract (English): We correlate an X-ray determination of the molecular and crystal structures of 2-tert-butylanthracene and 2-tert-butylanthraquinone reported here with the previously reported dynamical nuclear magnetic resonance determination of the motions of the tert-butyl groups and their resident methyl groups in the solid state [P.A. Beckmann, K.S. Burbank, M.M.W. Lau, J.N. Ree, T.L. Weber, Chem. Phys. 290 (2003) 241].

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Chemical Physics
Vol: 348, Issue: 1-3, June 2, 2008
pp. 175-180

Title: 14N and 17O electric field gradient tensors in benzamide clusters: Theoretical evidence for cooperative and electronic delocalization effects in N-H...O hydrogen bonding

Authors: Esrafili, M.D.; Behzadi, H.; Hadipour, N.L.

Keywords: Electron delocalization effects; Cooperative effects; Electric field gradient; Benzamide; Hydrogen bond; Natural bonding orbital (NBO) analysis

Abstract (English): Nuclear quadrupole coupling tensors of 14N and 17O nuclei in benzamide clusters (up to n=6) were calculated via density functional theory. Results revealed that N-H...O hydrogen bonds around the benzamide molecule in crystalline lattice have significant influence on 14N and 17O nuclear quadrupole coupling tensors. n-dependent trend in 14N quadrupole coupling tensors significantly correlates with cooperative effects of R(N-H...O) hydrogen bond distance. Natural bonding orbital analysis, NBO, was used to rationalize the quadrupole coupling results in terms of substantial nO->sN-H^* charge transfer in (benzamide)n=1-6 clusters. It was found that intermolecular nO->sN-H^* interactions play a key role in cooperative change of 14N and 17O quadrupole coupling tensors. There is an acceptable linear correlation between 14N or 17O quadrupole coupling tensors with strength of Fock matrix elements (Fij). This suggests that both 14N and 17O quadrupole coupling measurements can provide a useful probe for electron delocalization effects in both gaseous and condensed media.

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Chemical Physics Letters
Vol: 455, Issue: 4-6, April 10, 2008
pp. 178-183

Title: Quantification of crystalline phases and measurement of phosphate chain lengths in a mixed phase sample by 31P refocused INADEQUATE MAS NMR

Authors: O'Dell, L.A.; Guerry, P.; Wong, A.; Abou Neel, E.A.; Pham, T.N.; Knowles, J.C.; Brown, S.P.; Smith, M.E.

Abstract (English): A 31P refocused INADEQUATE NMR pulse sequence has been used to identify the crystalline phases present in a sodium calcium phosphate ceramic. An unidentified calcium phosphate phase was observed, featuring a chain of six crystallographically distinct PO4 tetrahedra, the 31P NMR chemical shifts of which have been identified in the correct sequence along the chain.

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Chemical Physics Letters
Vol: 456, Issue: 1-3, April 21, 2008
pp. 116-121

Title: Estimation of internuclear couplings in the solid-state NMR of multiple-spin systems. Selective spin echoes and off-magic-angle sample spinning

Authors: Pileio, G.; Mamone, S.; Mollica, G.; Montesinos, I.M.; Gansmuller, A.; Carravetta, M.; Brown, S.P.; Levitt, M.H.

Abstract (English): A combination of modulated pulses and off-magic-angle spinning NMR allows the estimation of distances between selected pairs of nuclei in the solid-state.

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Chemical Physics Letters
Vol: 456, Issue: 4-6, May 5, 2008
pp. 227-230

Title: Proton exchange in hybrid sulfonated poly(ether ether ketone)-silica membranes by 1H solid-state NMR

Authors: Baias, M.; Demco, D.E.; Colicchio, I.; Blumich, B.; Moller, M.

Abstract (English): The Eyring function is used for obtaining enthalpy of activation for proton exchange in sulfonated poly(ether ether ketone)-silica membranes by NMR.

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Chemical Physics Letters
Vol: 456, Issue: 4-6, May 5, 2008
pp. 253-256

Title: 1H homonuclear dipolar decoupling at high magic-angle spinning frequencies with rotor-synchronised symmetry sequences

Authors: Paul, S.; Thakur, R.S.; Madhu, P.K.

Abstract (English): Symmetry based rotor synchronised RNnn sequences were applied to obtain high resolution 1H spectra in solid-state NMR. The experimental and simulated data shows the potential of such RNnn sequences in obtaining high resolution spectra at high spinning speeds.

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Chemical Physics Letters
Vol: 456, Issue: 4-6, May 5, 2008
pp. 262-267

Title: Decomposition of a NMR signal comprising a single resonance in exchange with a Pake doublet: Application to the analysis of ^1H NMR spectra of water molecules embedded in synthetic clays

Authors: Trausch, G.; Canet, D.; Turq, P.

Abstract (English): NMR of water in clays include several overlapping resonances, possibly with a Pake doublet. Proportions and dipolar coupling were determined.

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Chemical Physics Letters
Vol: 458, Issue: 1-3, June 6, 2008
pp. 219-222

Title: Enantiomeric analysis using natural abundance deuterium 3D NMR spectroscopy in polypeptide chiral oriented media

Authors: Lesot, P.; Lafon, O.

Abstract (English): The use of natural abundance deuterium 3D NMR experiments for analyzing chiral molecules dissolved in chiral liquid crystals is reported.

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Dalton Trans., 2008, 2241 - 2247, DOI: 10.1039/b718438g

Title: NMR Transversal relaxivity of aqueous suspensions of particles of Ln3+-based zeolite type materials

Authors: Giovannia A. Pereira, Magorzata Norek, Joop A. Peters, Duarte Ananias, João Rocha and Carlos F. G. C. Geraldes

Abstract: A series of zeolite-type silicates containing stoichiometric amounts of Ln3+ ions in the framework (Ln-AV-9 materials), with composition (Na4K2)(Ln2Si16O38)10H2O (Ln = Nd, Sm, Eu, Tb, Gd, Dy) has recently been synthesized and characterized. They form paramagnetic microparticles, which as aqueous suspensions have negligible water 1H longitudinal relaxivities (t1) for all Ln3+ ions studied and quite large transverse relaxivities (t2). In this work we further analysed the size distribution of the Ln-AV-9 particles and their t2* and t2 relaxivities. The t2* relaxivity effects are explained by the static dephasing regime (SDR) theory. The t2 relaxivities appear to be strongly dependent on the interval between two consecutive refocusing pulses (CP) in the train of 180̊ pulses applied. For long CP values, the t2 of the systems saturates at a value, which is always an order of magnitude smaller than t2*. These features are explained by a crude model, which takes into account the residual diffusion effect in the static dephasing regime. The large microparticles, although not efficient in T1 relaxation, are quite effective in enhancing T2 relaxation, particularly at high magnetic fields. The t2* values and the saturation values for t2 were found to increase linearly with B0 and 02. The largest transversal relaxation rate enhancements were observed for Dy-AV-9 with a saturation value of t2 of 60 s-1 mM-1 and a t2* value of 566 s-1 mM-1 at 9.4 T and 298 K.

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Chem. Commun., 2008, 2361 - 2363, DOI: 10.1039/b801154k

Title: Proton chemical shift anisotropy measurements of hydrogen-bonded functional groups by fast magic-angle spinning solid-state NMR spectroscopy

Authors: Luminita Duma, Daniel Abergel, Piotr Tekely and Geoffrey Bodenhausen

Abstract: The suitability of fast MAS solid-state NMR spectroscopy for probing 1H chemical shift anisotropy of hydrogen-bonded species has been demonstrated.