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'35 C1 NQR spin lattice relaxation' in keywords
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1998 (1)
1996 (1)
1Author    A. Ishikawa, A. Sasane, Y. Hirakawa, Y. MoriRequires cookie*
 Title    Motion of Water Molecules and Hydrogen Bonds in Zinc Hexachlorostannate (IV) Hexahydrate as Studied by *H NMR and 35 C1 NQR  
 Abstract    The *H NMR spin-lattice relaxation time 7\, 35 C1 NQR frequency VQ, and 35 C1 NQR spin-lattice relaxation time 7\ Q of [Zn(H 2 0) 6 ] [SnCl 6 ] (zinc hexachlorostannate(IV) hexahydrate) have been measured at temperatures between 77 and 350 K. The NQR spin echo signal with Vq— 15.689 MHz at 77 K showed a positive temperature coefficient attributable to O-H-Cl type H-bonds in the crystal. v Q at 77 K is strongly correlated with the electronegativity Xm of the metal M in the series of stannates [M(H 2 0) 6 ] [SnCl 6 ] (M = Mg, Ca, Mn, Co, Ni, Zn). A 7\ minimum observed for the Zn salt is ascribed to 180° flips of water molecules with an activation energy of 20 kJ mol -1 . The motion is influenced by repulsive forces among the water molecules within a cation rather than by attractive forces between the H-bonded H and CI atoms. 7\q proved to be mainly governed by lattice vibrations, weakly modulated by the fluctuating electric field gradient caused by the 180° flip motions. 
  Reference    Z. Naturforsch. 51a, 693—697 (1996); received October 10 1995 
  Published    1996 
  Keywords    'H NMR spin-lattice relaxation, 35 C1 NQR frequency, 35 C1 NQR spin-lattice relaxation, H-bonding, Electronegativity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0693.pdf 
 Identifier    ZNA-1996-51a-0693 
 Volume    51 
2Author    A. Ishikawa, M. Kurasawa, S. Kitahara, A. Sasane, N. Kojima, R. IkedaRequires cookie*
 Title    A 35 C1 NQR Study on CS 2 [AU I C1 2 ] [Au m Cl 4 ]  
 Abstract    A pair of 35 C1 NQR spin echo signals has been observed for the mixed valence complex Cs 2 [Au'Cl 2 ] [Au'^C^] between 77 and 243 K. At 77 K, two resonance lines with the half widths Av Q ~ 50 kHz were located at v Q1 = 17.28 MHz for the Au'-Cl chlorine and at v Q2 = 27.10 MHz for the Au m -Cl chlorine in accordance with the crystal structure. The chlorine ionic characters of the Au'-Cl and Au'"-Cl bonds are estimated as 0.63 and 0.42, respectively. The central gold atom carries a fractional protonic charge of 0.26 in [AU'C1 2 ]~ and 0.68 in [Au"'Cl 4 p. The charge distributions in the complex anions differ in-significantly from those in the isolated [AUC1 2 ]~ and [AUC1 4 ]" for ordinary complexes, indicating that the charge transfer interactions between the anions are weak in the mixed valence complex. The ob-served linear temperature dependencies of Vg and log T lQ are well explained by the lattice vibration. When the temperature was increased from 77 K, the resonance lines became gradually weak without changing AV q and immeasurable above 215 K. ESR spectra taken at various temperatures revealed the presence of paramagnetic sites of ca. 5x 10 2<) mol -1 arising from Au(II). The small but finite concen-tration of Au(II) or some other reason should be responsible for the fade out phenomenon and the large Avq observed. 
  Reference    Z. Naturforsch. 53a, 590—594 (1998); received December 31 1997 
  Published    1998 
  Keywords    35 C1 NQR Frequency, 35 C1 NQR Spin-lattice Relaxation, Mixed Valence Gold Complex, Charge Transfer Interaction, ESR 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0590.pdf 
 Identifier    ZNA-1998-53a-0590 
 Volume    53