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Quadrupole Resonance (quadrupole + resonance)

Distribution by Scientific Domains
Chemistry100%

Kinds of Quadrupole Resonance

  • nuclear quadrupole resonance
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    Selected Abstracts

    A computational NQR study on the hydrogen-bonded lattice of cytosine-5-acetic acid

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2008
    Mahmoud Mirzaei
    Abstract A computational study at the level of density functional theory (DFT) employing 6-311++G** standard basis set was carried out to evaluate nuclear quadrupole resonance (NQR) spectroscopy parameters in cytosine-5-acetic acid (C5AA). Since the electric field gradient (EFG) tensors are very sensitive to the electrostatic environment at the sites of quadruple nuclei, the most possible interacting molecules with the target one were considered in a five-molecule model system of C5AA using X-ray coordinates transforming. The hydrogen atoms positions were optimized and two model systems of original and H-optimized C5AA were considered in NQR calculations. The calculated EFG tensors at the sites of 17O, 14N, and 2H nuclei were converted to their experimentally measurable parameters, quadrupole coupling constants and asymmetry parameters. The evaluated NQR parameters reveal that the nuclei in original and H-optimized systems contribute to different hydrogen bonding (HB) interaction. The comparison of calculated parameters between optimized isolated gas-phase and crystalline monomer also shows the relationship between the structural deformation and NQR parameters in C5AA. The basis set superposition error (BSSE) calculations yielded no significant errors for employed basis set in the evaluation of NQR parameters. All the calculations were performed by Gaussian 98 package of program. © 2007 Wiley Periodicals, Inc. J Comput Chem 2008 [source]

    Electronic structure and biological activity of chosen DDT-type insecticides studied by 35Cl-NQR

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2009
    Maciej Jad
    Abstract 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,-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. [source]

    The 14N quadrupole coupling in hexamethylene triperoxide diamine (HMTD)

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2007
    John Persons
    Abstract Using high-field NMR, we have determined the magnitude of the nuclear quadrupole interaction in hexamethylene triperoxide diamine (HMTD), the explosive allegedly used in the London bombings of July 2005. The experimental quadrupolar coupling constant, 5.334 MHz, is in good agreement with quantum chemical calculations. The predicted single zero-field transition frequency should lie in a relatively empty part of the 14N nuclear quadrupole resonance (NQR) spectrum; the spin relaxation rate is reasonably fast. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Two solid phases of pyrimidin-1-ium hydrogen chloranilate monohydrate determined at 225 and 120,K

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010
    Kazuma Gotoh
    The crystal structures of two solid phases of the title compound, C4H5N2+·C6HCl2O4,·H2O, have been determined at 225 and 120,K. In the high-temperature phase, stable above 198,K, the transition temperature of which has been determined by 35Cl nuclear quadrupole resonance and differential thermal analysis measurements, the three components are held together by O,H...O, N...H...O, C,H...O and C,H...Cl hydrogen bonds, forming a centrosymmetric 2+2+2 aggregate. In the N...H...O hydrogen bond formed between the pyrimidin-1-ium cation and the water molecule, the H atom is disordered over two positions, resulting in two states, viz. pyrimidin-1-ium,water and pyrimidine,oxonium. In the low-temperature phase, the title compound crystallizes in the same monoclinic space group and has a similar molecular packing, but the 2+2+2 aggregate loses the centrosymmetry, resulting in a doubling of the unit cell and two crystallographically independent molecules for each component in the asymmetric unit. The H atom in one N...H...O hydrogen bond between the pyrimidin-1-ium cation and the water molecule is disordered, while the H atom in the other hydrogen bond is found to be ordered at the N-atom site with a long N,H distance [1.10,(3),Å]. [source]