Nuclear magnetic resonance shifts in solution due to lanthanide ions

The pseudocontact contribution to the NMR shifts for lanthanide complexes in solution is derived from the anisotropy in the susceptibility. Provided that the molecular geometry is independent of temperature and of the lanthanide ion, the shift should vary as T−2 and in a predicted way from ion to ion. For Sm3+, 4f5 and Eu3+, 4f6 effects of excited states give a more complex temperature dependence; for the former ion a term in T−1 predominates, and for the latter the dependence is rather faster than T−1 near room temperature. For other ions such effects give corrections at room temperature of a few per cent for the light lanthanons, falling to less than 1% for the heaviest lanthanons.