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2000 (4)
1Author    Hiroyuki IshidaRequires cookie*
 Title    Conformations of Pyrrolidinium Ion Studied by Molecular Orbital Calculations  
 Abstract    Ab initio HF/6-3 lG(d. p) and density functional theory B3LYP/6-31G (d, p) calculations were carried out to investigate the conformations of pyrrolidinium ion. Two conformations, corresponding to twisted (C2) and envelope (Cs) forms were optimized. Vibrational analysis showed that the twisted form is at a local minimum point and the envelope form at a saddle point. The energy difference between the conformations is ca. 2 kJ mor 1 . 
  Reference    Z. Naturforsch. 55a, 665—666 (2000); received April 14 2000 
  Published    2000 
  Keywords    Pyrrolidinium Ion, Conformation: HF, DFT 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0665_n.pdf 
 Identifier    ZNA-2000-55a-0665_n 
 Volume    55 
2Author    Hiroyuki IshidaRequires cookie*
 Title    Protonation Effect on C-N Bond Length of Alkylamines Studied by Molecular Orbital Calculations  
 Abstract    Molecular orbital calculations were performed for the six saturated alkylamines (CH 3 NH 2 , (CH 3) 2 NH, (CH 3) 3 N, CH 3 CH 2 NH 2 , (CH 3) 2 CHNH 2 , (CH 3) 3 CNH 2), their protonated cations (CH 3 NH 3 + , (CH 3) 2 NH 2 + , (CH 3) 3 NH + , CH 3 CH 2 NH 3 + , (CH 3) 2 CHNH 3 + , (CH 3) 3 CNH 3 +), and (CH 3) 4 N + using the Hartree-Fock, second-order M0ller-Plesset, and density functional theory methods with the 6-311+G(d,p) basis set. Protonation lengthens the C-N bonds of the amines by 0.05 -0.08 A and shortens the C-C bonds of CH 3 CH 2 NH 2 , (CH 3) 2 CHNH 2 , and (CH 3) 3 CNH 2 by ca. 0.01 A. 
  Reference    Z. Naturforsch. 55a, 769—771 (2000); received August 8 2000 
  Published    2000 
  Keywords    Protonation, Amine, HF, DFT 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0769.pdf 
 Identifier    ZNA-2000-55a-0769 
 Volume    55 
3Author    O. Kh, J. N. Poleshchuk, B. Latosińska, NogajRequires cookie*
 Title    Analysis of the Quadrupole Coupling Constants and Mössbauer Iso- meric Shifts in Halogen Compounds Within the Gaussian98 Code  
 Abstract    A comparison of the experimental and calculated nuclear quadrupole coupling constants of diatomic halogen, interhalogen, trihalide ions and complexes of pyridine is a good test of reliability of semiempirical and non-empirical theories as well as their usefulness in the interpretation of quadrupole coupling data from the qualitative and quantitative point of view. Therefore, a practical way of gaining insight into the bonding properties and electronic structure of such systems consists of combining semiempirical MO calculations with experimental data to derive reliable information. In the present work we report the results of ab initio studies of several iodine containing molecules and ions using the calculated NQCC as a test of the quality of the wavefunctions. To demonstrate the quality of our calculations, we compare the calculated halogen-halogen bond length and QCC with the corresponding experimental values for the compounds studied. With a few exceptions, the overall agreement with experiment is most satisfactory. The results on dipole moments and energy levels are also in a good agreement with the experimental data, however these quantities were measured only in the few cases. 
  Reference    Z. Naturforsch. 55a, 271—275 (2000); received September 11 1999 
  Published    2000 
  Keywords    DFT, QCC, Isomeric Mössbauer Shifts, Halogen Compounds 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0271.pdf 
 Identifier    ZNA-2000-55a-0271 
 Volume    55 
4Author    O. Kh, Poleshchuk, J. N. LatosińskaRequires cookie*
 Title    Quadrupole Coupling Constants and Mössbauer Isomeric Shifts in Antimony Compounds within Gaussian 98  
 Abstract    The electron density and quadrupole coupling constants of molecules containing Sb are analysed. The NQCC for antimony, calculated using the extended basis 6-311G** are much lower than the experimental data, while the use of the small 3-21G* basis led to NQCC closer to the experimental ones. 
  Reference    Z. Naturforsch. 55a, 276—280 (2000); received August 23 1999 
  Published    2000 
  Keywords    DFT, QCC, Isomeric Mössbauer Shifts, Antimony Compounds 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0276.pdf 
 Identifier    ZNA-2000-55a-0276 
 Volume    55