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1Author    Jürgen Senker3, Jens LüdeckebRequires cookie*
 Title    Structure Determination for the Crystalline Phase of Triphenyl Phosphite by Means of Multi-Dimensional Solid-State NMR and X-Ray Diffraction  
 Abstract    The crystalline phase of triphenyl phosphite P(OCöH5)3 was investigated by means of 11P solid-state NMR and X-ray diffraction in a temperature range between 170 K and its melting point (Tm = 293 K). ID MAS NMR spectra exhibit one sharp central resonance indicating only one crystallographically unique molecule in the unit cell. A theoretical analysis concerning the shape of 2D exchange spectra for 1 = 1 /2 nuclei is presented. It is shown that if the exchange is caused by radio-frequency driven spin-diffusion, this technique allows to discriminate rota­ tional symmetry elements in crystalline solids. Used on crystalline triphenyl phosphite, 3-fold symmetry could be revealed clearly. Structure determination based on X-ray single crystal diffraction data collected at 191 K shows that triphenyl phosphite crystallises in hexagonal metric with space group R3 (w R i = 8.3%, Z = 18) and one molecule in the asymmetric unit. This result is in excellent agreement with the NMR spectroscopic data. The lattice parameters at 200 K were determined to a = 37.887(1) and c = 5.7567(2) Ä (V = 7156(1) A3) by refining an X-ray powder-diffraction pattern. The structure of triphenylphosphite can be described as a close rod packing. The rods are formed by ecliptically arranged triphenylphosphite molecules. Due to the 3-fold rotoinversion axis the orientation of molecules in neighboured rods is anti­ parallel. 
  Reference    Z. Naturforsch. 56b, 1089—1099 (2001); received July 18 2001 
  Published    2001 
  Keywords    Triphenyl Phosphite, Structure Determination, Solid-State NMR 
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 TEI-XML for    default:Reihe_B/56/ZNB-2001-56b-1089.pdf 
 Identifier    ZNB-2001-56b-1089 
 Volume    56 
2Author    V. P. Tarasov, G. A. Kirakosyan, K. E. German, Acad Sei, UssrRequires cookie*
 Title    Anomalous Temperature Dependence of the "Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTc0 4  
 Abstract    A "Tc and 133 Cs solid-state NMR study of polycrystalline CsTc04 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. "Tc quadrupole coupling constant, Cq, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, rj ("Tc), is zero at 430 K and at 210 K. The high-temperature minimum of rj is associated with a phase transition from orthorhombic to tetrag-onal and the second minimum reflects an orientational change of the principal axes q xx and q yy of the EFG-tensor. The 133 Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1, varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations. 
  Reference    Z. Naturforsch. 47a, 325—329 (1992); received July 26 1991 
  Published    1992 
  Keywords    Technetium, Cesium, Solid State NMR, Quadrupole Effects, Phase Transitions 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0325.pdf 
 Identifier    ZNA-1992-47a-0325 
 Volume    47 
3Author    P. Hartmann, G. SchelerRequires cookie*
 Abstract    Herrn Prof. W . Müller-Warmuth zum 65. Geburtstag gewidmet Is solid state 91 Zr NMR feasible? 91Zr solid state NMR spectra have been observed for samples possessing different zirconium local-site environments (e.g. phosphates, fluorides). Depending on the quadrupole coupling, different NMR experiments have been utilized. In case of weak quadrupole coupling, magic angle spinning (MAS) is suitable. Otherwise, spin echo techniques are necessary to overcome "acoustic ringing" and receiver dead-time limitations. Using the step echo method, the detection of the very broad 91Zr signals is not limited by non-uniform spectral excitation. The obtained 91Zr chemical shifts range from —246 ppm to 208 ppm, the quadrupole coupling frequencies from 50 kHz to 2.7 MHz.. I s t 91Z r -F e s tk ö r p e r -K e r n r e s o n a n z s p e k tr o s k o p ie p r a k tik a b e l? 
  Reference    Z. Naturforsch. 50a, 90—94 (1995); received September 26 1994 
  Published    1995 
  Keywords    Solid state NMR, Zirconium-91, MAS, Spin echo, Acoustic ringing 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0090.pdf 
 Identifier    ZNA-1995-50a-0090 
 Volume    50 
4Author    Shuan Dong, Kazuhiko Yamada, Gang WuRequires cookie*
 Title    Oxygen-17 Nuclear Magnetic Resonance of Organic Solids  
 Abstract    We report solid-state l7 0 NMR determinations of the oxygen chemical shift (CS) and electric field gradient (EFG) tensors for a series of 17 0-enriched organic compounds containing various functional groups. In several cases, analysis of the n O magic-angle-spinning (MAS) and static NMR spectra yields both the magnitude and relative orientations of the 17 0 CS and EFG tensors. We also demonstrate the feasibility of solid-state 17 0 NMR as a potentially useful technique for studying molecular structure and hydrogen bonding. 
  Reference    Z. Naturforsch. 55a, 21—28 (2000); received September 11 1999 
  Published    2000 
  Keywords    Oxygen-17, Solid State NMR, Organic Compounds, Chemical Shift Tensor, Quadrupole Coupling Constant 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0021.pdf 
 Identifier    ZNA-2000-55a-0021 
 Volume    55