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Some CNDO/S parameterized calculations of intramolecular effects on nuclear shielding
Author(s) -
Hamdi B. T.,
Reynolds D. J.,
Webb G. A.
Publication year - 1984
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270220207
Subject(s) - electromagnetic shielding , cndo/2 , intramolecular force , bond length , nitrogen , shielding effect , chemistry , variation (astronomy) , molecular geometry , molecular physics , crystallography , materials science , atomic physics , molecule , stereochemistry , physics , crystal structure , composite material , organic chemistry , astrophysics
Some shielding calculations, using Pople's SOS model, are reported for B, C, N, F, P and Si as a function of changes in bond length and pyramidal bond angle. In all cases considered, the shielding is predicted to decrease as the bond length increases, which is in line with the available experimental data. The observed temperature variation of the nitrogen and phosphorus shieldings of NH 3 , PH 3 and PF 3 could be accounted for by a decrease in the pyramidal angle at higher temperatures. A similar angular variation for NF 3 is predicted to cause a shielding variation, with temperature, in the same sense as that reported for NH 3 and PH 3 , but opposite to that for PF 3 .