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1Author    MarcoL H Gruwel, RoderickE. WasylishenRequires cookie*
 Title    A Deuterium NMR Study of some Ammonium Tetraphenylborates  
 Abstract    Deuterium nmr has been used to study the rotational dynamics of the ammonium ion in ammo-nium tetraphenylborate and of the cation in a series of methylammonium tetraphenylborates. The results of variable temperature 2 H relaxation measurements (T 1Z and T 1Q) on the parent compound, ND 4 B(C 6 H 5) 4 , lead to a low activation energy for reorientation of the ND 4 ion, 5.0 ± 0.5 kJ mol -1 , indicative of weak cation-anion interactions. Related studies of the tetramethyl-d 12 ammonium salt indicate rapid jumps of the whole cation (T <|10 -5 S) over the complete temperature range investi-gated, 137 to 385 K, with an activation energy of 14.1 + 0.5 kJ mol" 1 . Deuterium nmr lineshape studies of the methylammonium salt indicate rapid reorientation of the CD 3 and ND 3 groups about their C 3 axes; however, the motion of the C-N axis is restricted to large amplitude librations. Similar studies of the dimethylammonium salt indicate methyl group jumps at 245 K; at temperatures above 320 K the cation also undergoes two-site jumps about the C 2 axis. In the case of the trimethylam-monium salt, the nmr lineshapes indicate methyl group jumps superimposed on C 3 rotations of the complete cation about the N-H bond axis over the temperature interval 185-348 K. In all the tetraphenylborate salts studied, the 2 H nmr lineshapes indicate substantial librational motion of the cation at room temperature. 
  Reference    Z. Naturforsch. 45a, 55—66 (1990); received August 31 1989 
  Published    1990 
  Keywords    2 H nmr, rotation, ammonium derivatives, tetraphenylborates 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0055.pdf 
 Identifier    ZNA-1990-45a-0055 
 Volume    45 
2Author    K. Yamada, T. Ohtani, S. Shirakawa, H. Ohki, T. Okuda, T. Kamiyama, K. OikawaRequires cookie*
 Title    Phase Transition of C 5 H 5 NHSbBr 4 Having a Hypervalent Bond: A 2 H NMR and X-Ray Diffraction Study* [Phase Transition of C 5 H 5 NHSbBr 4 l  
 Abstract    The second order phase transition at 253 K of pyridinium tetrabromoantimonate(III), C 5 H 5 NHSbBr 4 , has been characterized by means of X-ray diffraction and 2 H NMR. As was suggested from the 81 Br NQR spectra, the Rietveld refinements of the X-ray diffraction patterns at 297 K and 116 K confirm the structural change of the anion from SbBr 4 to SbBr 3 • Br -. The line shape analysis of the 2 H NMR using the deuterated analog revealed that the librational amplitude of the pyridinium ring about the axis normal to the plane increased with temperature and its rms amplitude reaching ca. 25° at T c . The librational motion may induce the phase transition breaking the hydrogen bonds of the type N-H -Br. However, nearest-neighbor 2n/6 jump or reorientation such as seen in benzene were not observed even at 350 K. 
  Reference    Z. Naturforsch. 51a, 739—744 (1996); received October 11 1995 
  Published    1996 
  Keywords    2 H NMR, 81 Br NQR, Rietveld analysis, Phase transition, Hypervalent bond 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0739.pdf 
 Identifier    ZNA-1996-51a-0739 
 Volume    51 
3Author    Naohiro Yoshida, Noriko Onoda-Yamamuro, Shin'. Ichi Ishimaru, Keizo Horiuchi, Ryuichi IkedaRequires cookie*
 Title    Temperature Dependence of 2 H Quadrupole Coupling Constants in 2 H 2 0 and Ionic Motions in Crystalline IM( 2 H 2 0) 6 ] ISnCl 6 ] (M: Mg, Ca), Studied by 2 H NMR and Neutron Powder Diffraction  
 Abstract    The temperature dependence of 2 H NMR spectra was measured at 130-430 K on [M(D 2 0) 6 ] [SnCl 6 ] (M : Mg, Ca) (rhombohedral, space group: R3), and neutron powder diffraction on the Mg salt was performed at room temperature. Based on the accurate orientation of D 2 0 molecules in an octahedral cation, spectra with a large asymmetry parameter rj, observed around 200 K, were explained by a model of 180° flip of water molecules. Another motional narrowing observed above room temperature was assigned to a cationic overall reorientation about the C 3 -axis. 
  Reference    Z. Naturforsch. 53a, 473—479 (1998); received October 31 1997 
  Published    1998 
  Keywords    2 H NMR, Neutron Diffraction, Molecular Motion, Quadrupole Coupling Constant, Spectrum Lineshape 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0473.pdf 
 Identifier    ZNA-1998-53a-0473 
 Volume    53 
4Author    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 
5Author    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