Determination of the rotation-diffusion tensor orientation from NMR [sup 13]C–[sup 1]H cross-relaxation rates.

Taking advantage of the fact that α,α,2,6 tetrachlorotoluene possesses only one symmetry element (the aromatic ring plane), it proved possible to measure seven different [sup 13]C-[sup 1]H crossrelaxation rates which enable one to determine the three rotation-diffusion coefficients (D[sub xx], D[sub yy], D[sub zz]), in addition to the orientation of the relevant principal axis system (PAS) with respect to a chosen molecular axis system. It turns out that molecular reorientation is strongly anisotropic and that the rotation-diffusion PAS cannot be directly correlated with electrical molecular properties. [ABSTRACT FROM AUTHOR]