Europium(III) complex formed with pyridine containing azamacrocyclic triacetate ligand: characterization by sensitized Eu(III) luminescence

The water soluble polyazamacrocyclic ligand, 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (111Py12N4) has been synthesized and found to be an effective antenna molecule for europium luminescence. When bound to Eu(III), excitation at the absorption band of the 111Py12N4 ligand (264 nm) leads to the well-known structured emission spectrum of the Eu(III) ion with a large Stockes shift (>250 nm). UV-light induced Eu(III) luminescence resulting from a through-space energy transfer allowed the determination of a 1:1 stoechiometry of the Eu(III) complex and the determination of the corresponding stability constant (log K therm=20.9). The luminescence lifetimes, the number of water molecules coordinated to the metal as well as the overall quantum yields were evaluated.