ABSTRACT
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Paramagnetic systems are materials with positive magnetic susceptibility associated with unpaired electrons. Paramagnetic solutions of interest to chemists usually contain free radicals or transition metal complexes. In addition, the paramagnetism of certain species with an electronic triplet ground state, such as the oxygen molecule, sometimes needs to be considered. To a certain extent, the unpaired electron spins behave in a similar way as the nuclear spins. The differences — and the profound influence of unpaired electron spins on NMR spectra — are, in the first place, related to the large value of the electronic magnetic moment, about 650 times that of the proton. In the second place, we need to consider the strong coupling of the electron spin to other degrees of freedom and the delocalized nature of the electron.
