Abstract

The indirect spin-spin coupling is a molecular internuclear interaction, which is observable by utilizing NMR spectroscopy. This coupling, denoted J, is a second-order tensorial property that consists of rank-0, 1, and 2 components. The present thesis deals with the experimental determination of the rank-0 and rank-2 components of J tensors for different pairs of interacting nuclei by utilizing liquid crystal NMR (LC NMR) method.

The experimental information of the rank-2 component of the J tensor appears as J^aniso, a combination of tensor elements. In LC NMR, J^aniso is manifested as a contribution to the experimental anisotropic coupling (D^exp ) that contains also the corresponding internuclear dipolar coupling, D. The dipolar coupling is defined by the molecular geometry and average orientation, and affected by the molecular motions. Therefore, the molecular geometry and orientation have to be determined together with the studied J^aniso couplings. The contributions to D couplings arising from the molecular vibrations and solvent-induced deformation of the molecular geometry are taken into account in the analysis of the experimental data; the contributions are presented briefly in this thesis.

The LC NMR experiments are performed for C₆H₆, HCONH₂, C₂H₂, C₂H₄, C₂H₆, 1,4-C₆H₄F₂, CH₃F, CH₂F₂, CHF₃, and CSiH₆ molecules, and some important aspects of the liquid crystal NMR method are discussed. The obtained information of J tensors is compared with the theoretical ab initio MCSCF results. Finally, the systematics of the J tensors in different structural surroundings is found and the significance of the indirect contribution to the corresponding D^exp coupling is discussed.