NMR of partially aligned molecules

One of the main uses of NMR of partially aligned molecules has been to gain access to the dipolar coupling constants (Dy), because these can be related directly to the internuclear distances (ry) between each pair of interacting nuclei i and j. The Dy values are obtained by spectral analysis, most usually by computer simulation of experimental spectra. The Dy are inversely proportional to the cube of the internuclear distances (ry) (Eq. (1)). Providing sufficient independent Dy values can be measured and the relative positions of the nuclei in the spin system can be determined then the shape of the molecule as well as its average orientation in the magnetic field can be deduced. 

The induced alignment of solutes oriented in liquid crystalline solution is very sensitive to small variations in temperature. Sy values are temperature sensitive and since Dy is proportional to Sy, care must be exercised if spectra 

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The volume opens with a report by L.D. Field on Multiple Quantum NMR of Partially Aligned Molecules following this is an account on Solid-State NMR Studies of Molecular Motion by M.J. Duler C. Odin reviews NMR Studies of Phase Transitions Application of Multi-way Analysis to 2D NMR Data is covered by H.T. Pedersen, M. Dyrby, S.B. Engelsen and R. Bro the final contribution is on High Resolution Protein Structure Determination by NMR and it is provided by H. Takashima. My sincere thanks go to all of these reporters and to the production staff at Elsevier for their assistance in the creation of this volume. 

Although the vast majority of H NMR studies on hydrogenated fullerenes have focused on structure determination, it can also be used to study molecular dynamics and partial alignment of the molecule in solution (see Section 9.7.1). 

After the early work on dipolar couplings measured for small organic molecules in liquid crystalline phases, major elements of weak partial alignment have been developed in the field of biomolecular NMR spectroscopy where... 

According to Equ. (11) the partial alignment of a radical in a liquid crystal causes only shifts in the line positions. In contrast to the situation in nmr spectroscopy no new lines appear as a consequence of the partial orientation. The components of the g- and A-tensor and the elements of the order matrix always enter in combination into Equ. (11). Consequently these parameters cannot be determined simultaneously from the line shifts caused by the partial alignment even in the simplest case of cylindrical molecules. 

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