Macrocyclic and macropolycyclic heteroaromatic N-oxides: powerful sensitizers for the lanthanide ions emission

Heterocyclic ligands are common sensitizers for the lanthanide ions emission upon UV irradiation. Of particular interest are Tb(III) and Eu(III) ions in combination with acyclic, macrocyclic and macropolycylic ligands incorporating heterobiaryls, such as 2,2ʹ-bipyridyl, 1,10-phenanthroline, 1,1ʹ-biquinoline, 3,3ʹ-biisoquinoline, and their derivatives. Much more powerful sensitizers are the same systems bearing N-oxide functions, furthermore their complexes are more stable than the parent heterocycles. Such luminescent materials are the basis for time-resolved fluoroimmunoassays displaying very high sensitivity, and serve as materials for advanced medical diagnostics. In this short review, a brief presentation will focus on state-of-the-art photochemistry and photophysics of the lanthanide complexes of heterocyclic and N-oxide-incorporating heterocyclic systems.