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'Nuclear Quadrupole Interaction' in keywords Facet   section ZfN Section A  [X]
Facet   Publication Year 2000  [X]
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2000[X]
1Author    Nobuo Nakamura, Hirotsugo Masui, Takahiro UedaRequires cookie*
 Title    Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations  
 Abstract    Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bond-ing on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (r?) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correla-tion between the QCC of l4 N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hy-drogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as /C* when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the ob-served N-H distances in imidazole derivatives should be re-examined. 
  Reference    Z. Naturforsch. 55a, 315—322 (2000); received August 26 1999 
  Published    2000 
  Keywords    Hydrogen Bond, Nuclear Quadrupole Interaction, Molecular Orbital, Imidazole 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0315.pdf 
 Identifier    ZNA-2000-55a-0315 
 Volume    55 
2Author    Takahiro Iijima, Motohiro Mizuno, Masahiko SuharaRequires cookie*
 Title    H NMR Study of Molecular and Electron Spin Dynamics in Paramagnetic [Co(H 2 0) 6 ][SiF 6 ]  
 Abstract    The temperature dependences of 2 H NMR spectra and the spin-lattice relaxation time T\ were measured for [Co(H20)f,][SiF6]. The variation of the spectrum above room temperature can be explained by the reorientation of [Co(H20)fi] 2+ about the C3 axis. The activation energy E a and the jumping rate at infinite temperature fco for the three site jump of [Co(H20)6] 2+ were obtained as 82 kJmol -1 and 2x 10 17 s~ 1 from the spectral simulation. Below room temperature, the spectral line shape was dominated by the 180° flip of the water molecule. The minimum of T\ caused by the 180° flip of the water molecule was observed at ca. 260 K. The jumping rate of the 180° flip of the water molecule was estimated from the 2 H NMR T\ and the spectral simulation. E* = 38 kJmol -1 and fco = 6x 10 l5 s -1 for the 180° flip of the water molecule were obtained from T\. 
  Reference    Z. Naturforsch. 55a, 173—177 (2000); received August 23 1999 
  Published    2000 
  Keywords    Phase Transition, 2 H NMR, Nuclear Quadrupole Interaction, Paramagnetic Shift, Molecular Dynamics 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0173.pdf 
 Identifier    ZNA-2000-55a-0173 
 Volume    55 
3Author    Motohiro Mizuno, Takahiro Iijima, Kengo Orii, Masahiko SuharaRequires cookie*
 Title    Water Molecular Motion and Hydrogen Bond in Paramagnetic [Cu(H 2 0) 6 ][PtCl 6 ] as Studied by Single Crystal 2 H NMR  
 Abstract    The temperature and angular dependences of the 2 H NMR spectrum were measured for single crystal [Cu(H 2 0) 6 ] [PtCl 6 ]. (e 2 Qq/h, r?) = (132 kHz, 0.72) were obtained for the D nucleus averaged by the fast 180° flip of the water molecule at 297 K. D,(236 kHz, 0.10) and D 2 (246 kHz, 0.09) were obtained for two unequal D nuclei of the water molecule at 133 K. Below T c , at least three nonequivalent waters were found to exist. The jumping rate for the 180° flip of the water molecule (k) was obtained from the simulation of 2 H NMR spectra at //o||[l 11] direction. The activation energy E d and the jumping rate at infinite temperature were estimated from the temperature dependence of k to be 24kJmol _1 and 1 x 10 13 s -1 . 
  Reference    Z. Naturforsch. 55a, 178—182 (2000); received August 23 1999 
  Published    2000 
  Keywords    Phase Transition, 2 H NMR, Nuclear Quadrupole Interaction, Paramagnetic Shift, Molecular Dynamics 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0178.pdf 
 Identifier    ZNA-2000-55a-0178 
 Volume    55