Localized systems mechanisms for f-f transition probabilities in lanthanide coordination compounds

Abstract

The origins and development of the ligand polarization mechanism for f-f transition probabilities in lanthanide coordination compounds are briefly surveyed. Applied initially to lanthanide(III) complexes containing monoatomic ligands, which have an effectively isotropic polarizability, the mechanism is found to depend, on extension to the corresponding polyatomic ligand cases, on the anisotropy of the ligand polarizability tensor in complexes of the higher non-centric symmetries. The crystal field and the ligand polarization mechanisms make complementary intensity contributions to the f-f transitions of a given lanthanide(III) complex type which are dependent on the rank of the leading electric multipole transition moment. The latter mechanism contributes principally to the intensities of the ligand-hypersensitive 2 2-pole f-f transitions, whereas the former mechanism is predominant for the 2 6-pole transition intensities and makes the more important contribution in the 2 4-pole cases.