Study of thermal and optical properties of dibenzoylmethane eu(III) organic complexes

Abstract

Two Europium(III) organic complexes (ternary complex Eu(DBM)3(PHEN) and tetrakis complex [Eu(DBM)4]N(Et)4, where DBM is dibenzoylmethane and PHEN is 1,10-phenantroline) were synthesized and their structures proven with1H-NMR spectroscopy, elemental analysis, FT-IR and mass spectroscopy. Their photophysical properties have been investigated in solution, solid-state and in poly-N-vinylcarbazole (PVK) films varying complex composition from 1 to 15 wt%. Both complexes exhibit intense UV light absorption and bright red-light emission with maximum wave length at 612 nm. It was shown that tetrakis complex in solution, solid-state and PVK films have enhanced photoluminescence properties compared to ternary complex due to four DBM molecules in Eu3+ coordination sphere, which leads to more effective excited energy transfer to Eu3+ ion. In THF solutions both complexes are characterized with low photoluminescence quantum yields (4% and 6%), in PVK films – moderate quantum yields (14–48%), but in solid state with high quantum yields (56% and 75%). Thermal properties for pure complexes and their PVK films were studied with thermogravimetric analysis. Both complexes exhibit high thermal degradation temperatures of 304 °C for ternary and 267 °C for tetrakis complex, but their PVK films show even higher degradation temperature (over 370 °C).