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A complex procedure for quantitative allowance for small but significant effects of molecu lar orientation by strong static magnetic fields was elaborated. A series of high resolution 1 H 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 1 H 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 prop erty 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 calcu lated 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 agree ment with the experimental values of the magnetic susceptibility anisotropy for 1,2,3 tri chloronaphthalene. 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.Key words: NMR spectroscopy, orientation effects in magnetic field, ab initio quantum chemical calculatinos, structure of molecules in solution, anisotropy of magnetic suscepti bility, spin spin coupling constants, dipole dipole coupling constants.NMR spectroscopy belongs to key methods of investi gation of the structures and properties of compounds in solution. Recently, strong and very strong magnetic fields (10-20 T and greater) have been more and more often used. On the one hand, this improves the sensitivity of the method and facilitates interpretation of NMR spectra. On the other hand, this creates pre requisites for manifesta tion of the effects of orientation of molecules in strong magnetic fields. This phenomenon was disclosed quite recently; 1 it is due to the interaction of permanent mag netic field with the induced magnetic moment of a mol ecule. 2 The energy of this interaction is low compared to the energy of thermal motion, which prevents molecules from being ordered, and the resulting extent of orienta tion of small molecules by magnetic field in isotropic media is low. In liquids and gases the orientation effects can manifest themselves in NMR spectra owing to aniso tropic interactions of nuclear spins, namely, a non van ishing direct interaction between nuclear dipoles and the interaction of the nuclear quadrupole moment with the local electric field gradient produced by the environment.Detailed analysis of the manifestation of this new physical phenomenon can provide important information on the conformational state of molecules containing specifically oriented aromatic residues including such complex ob jects, as natural proteins, DNA, and their complexes in solution. 3,4 The aim of this study was t...

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