High yield luminescence of a novel europium complex by excimer excitation and f-f absorption of Eu³⁺

A new organic ligand, 2-allyl-1,3-diphenyl-1,3-propanedione (ADP), and the corresponding quaternary Eu³⁺ complex, bi (ADP) (dibenzoyl methane) (1,10-phenanthroline) europium(III) [Eu(ADP)₂(DBM)(Phen)] have been synthesized. Excellent red luminescence from the Eu³⁺ complex was observed excited at 419 nm, and the broad visible excitation band is attributed to excimer absorption. The luminescence quantum yield excited at 419 nm (34 ± 3%) was higher than that at 380 nm (30 ± 3%). This is the first time to find strong and high yield excimer excitation absorption for a europium complex at room temperature, therefore, the excimer absorption band located in visible region (400-500 nm). Moreover, very high yields of direct f-f excitation absorption of Eu³⁺ ions at 466 nm (104 ± 10%) and 536 nm (96 ± 10%) were firstly observed, and the excitation spectrum for the europium complex in solid state is extended in wide region from 220 nm to 580 nm.