Crystal Structure Refinement Using Chemical Shifts

The NMR chemical shift is available from practically every conventional NMR experiment. In contrast to X-ray diffraction it is mainly caused by the density distribution of the valence electrons, hence it contains genuine information about the valence structure of the molecular system. High-resolution solid-state investigations on crystalline systems revealed a considerable dependence of the chemical shift on the 3D arrangement of the atoms and on their packing within the unit cell [1]. In many cases, an asymmetric content of the unit cell could be deduced from NMR line splittings. The point group symmetry of the molecule under study is frequently reflected within the NMR spectra and especially within the chemical shift tensors [2]. It was demonstrated by Taulelle [3] that even the complete space group could be deduced from NMR results.