Principles of High-Resolution NMR Spectroscopy of Paramagnetic Molecules in Solutions

The review summarizes the peculiarities of NMR phenomenon in paramagnetic molecules. These peculiarities are due to hyperfine or electronic coupling between the unpaired electrons and the resonant nuclei that leads to the paramagnetic broadening as well as to the paramagnetic shifts (contact and pseudocontact) of resonance lines in NMR spectra. The contact shift is observed when a probability of the unpaired electron disposition in the location of resonance nucleus is different from zero. Therefore, these shifts can be considered as a source of information about nature of the metal-ligand bond as well as about electron structure of the ligands. Pseudocontact shifts characterize the spatial structure of the molecule and can be used for solving various structural problems. The review covers the pioneering works describing the specifics of the NMR spectra transformed by additives of paramagnetic complexes of iron group elements including those of cobalt and nickel as well as complexes of