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.

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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.

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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.

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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.

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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.