Orientation of molecules by magnetic field as a new source of information on their structures |
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Authors: | A K Shestakova A V Makarkina O V Smirnova M M Shtern V A Chertkov |
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Institution: | (1) State Research Institute of Chemistry and Technology of Organoelement Compounds, 38 Shosse Entuziastov, 111123 Moscow, Russian Federation;(2) Chemistry Department, M. V. Lomonosov Moscow State University, 1 Leninskie Gory, 119992 Moscow, Russian Federation |
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Abstract: | A complex procedure for quantitative allowance for small but significant effects of molecular orientation by strong static
magnetic fields was elaborated. A series of high-resolution 1H NMR spectra of 1,2,3-trichloronaphthalene recorded at magnetic field strength varied over a wide range was analyzed in the
framework of a unified approach with high accuracy. The spin-spin coupling constants and the dipole-dipole coupling constants
for all pairs of 1H nuclei and the anisotropy and rhombicity parameters of the magnetic susceptibility tensor of the molecule were determined.
Ab initio CSGT/RHF quantum chemical calculations of this property using a wide range of conventional diffuse and polarization basis
set functions were carried out. Augmentation of the basis set with polarization functions affects the values of the calculated
parameters to a lesser extent compared to augmentation with diffuse functions. The results of calculations using the 6-311G(df)
and 6-311++G(df) basis sets are in good agreement with the experimental values of the magnetic susceptibility anisotropy for
1,2,3-trichloronaphthalene. The advantages of the method proposed and specific features of the effects of orientation by magnetic
field as a new source of information on the structure of molecules in solution are discussed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1309–1317, August, 2006. |
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Keywords: | NMR spectroscopy orientation effects in magnetic field ab initio quantum chemical calculatinos structure of molecules in solution anisotropy of magnetic susceptibility spin-spin coupling constants dipole-dipole coupling constants |
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