Sensitized emission of luminescent lanthanide complexes based on a phosphane oxide derivative

The photophysical properties of a complex based on diphenylphosphanoethane (DPPE) fluorescent ligands linked to a europium ion have been investigated by different spectroscopic methods. Upon complexation with europium, the interaction of the phosphane oxide group with europium leads to a red shift of the absorption spectrum and a strong quenching of the ligand emission. The typical sensitized emission of Eu(3+) is observed upon excitation of the ligand with a fluorescence quantum yield of 1%. Time-resolved absorption and emission experiments have been performed in order to investigate the photophysical mechanism involved in this complex. Photophysical studies show that an energy-transfer mechanism occurs from both the first excited singlet and triplet states of the ligand, and the population of the europium ion to the (5)D(1) state takes place, from which the (5)D(0) state is populated. Additionally, electron transfer from the excited singlet state of the ligand to the europium ion appears as a very efficient process.