Aryl-Bridged 1-Hydroxypyridin-2-one: Sensitizer Ligands for Eu(III)

The synthesis, crystal structure, solution stability, and photophysical properties of an aryl group bridging two 1-hydroxypyridin-2-one units complexed to Eu(III) are reported. The results show that this backbone unit increases the rigidity of the ensuing complex, and also the conjugation of the ligand. As a result of the latter, the singlet absorption energy is decreased, along with the energy of the lowest excited triplet state. The resulting efficiency of sensitization for the Eu(III) ion is influenced by these phenomena, yielding an overall quantum yield of 6.2% in aqueous solution. The kinetic parameters arising from the luminescence data reveal an enhanced nonradiative decay rate for this compound when compared to previously reported aliphatic bridges.