Lanthanide complexes nitrogen donor ligands

The impetus for the development of synthesis and characterization of complexes of lanthanides with organic nitrogen donor ligands is due to the search for more efficient luminescent rare earth compounds. One of the difficulties is the risk of precipitating lanthanide hydroxides in the process of synthesis of lanthanide complexes with organic amines. In the early stages, lanthanide complexes of heterocyclic bases of low basicities were prepared in aqueous alcoholic media [224], In the synthesis section it was appropriately pointed out the need for the anhydrous conditions and involved procedures for the preparation of lanthanide complexes of ligands of non-ionizable nature. Some representative complexes of both aliphatic and aromatic amines are listed in Table 4.19. 

Lanthanide complexes with nitrogen donor ligands.659... 

In addition to this wide range of uses for yttrium, new applications of yttrium complexes are under continual development. Examples include hydrate with halide and other simple ligands, with oxygen donor ligands with lanthanides, or mixed (e.g., metal diyttrium-barium and yttrium-copper), with nitrogen donor ligands, with... 

Both the synthetic trends and the reactivity of the metal macrocycle complexes considered in this review find some rationalization in the strudural data obtained from X-ray analysis. In the series of complexes containing the six-nitrogen, 18-atom macrocycles with aliphatic side-chains, the macrocydic moiety can flex to a different extent in each metal complex, thus allowing the most favorable metal-donor distance to be achieved for all donor atoms. These favorable metal-donor distances, together with appropriate geometries of the donor atoms and low steric strain, must account for the unique inertness displayed by these metal-macrocycle entities under conditions (dilute aqueous solution, presence of acids, bases and competing ligands) that would cause most other lanthanide complexes to decompose instantly. 

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