Judd-Ofelt analysis on trifluoroacetate europium complexes for liquid laser media

Four europium trifluoroacetate complexes, Eu(CF 3 COO) 3 ·bpy(bpy=2,2′-bipyridine)( 1 ), Eu(CF 3 COO) 3 ·phen(phen=1,10-phenanthroline)( 2 ), Eu(CF 3 COO) 3 ·2bp(bp=benzophenone)( 3 ) and Eu(CF 3 COO) 3 ·2tppo(tppo=triphenyl-phosphine oxide)( 4 ) were synthesized and characterized by elemental analysis, Fourier transform infrared(FTIR) spectroscopy, photoluminescence(PL) spectroscopy and thermogravimetric analysis(TGA). The PL spectra of the complexes at room temperature show the strong typical Eu 3+ ion red emission, due to the efficient energy “antenna absorption” of ligands and transitions of Eu 3+ ion between 5 D 0 → 7 F J ( J =0–4) . The long lifetime and high quantum yield reflect that the multiphonon relaxations by coupling to O-H and C-H vibrations were reduced. According to the photoluminescent spectra, the Judd-Ofelt parameters Ω 2 and Ω 4 of the complexes were calculated and the radiative properties were also presented. The 5 D 0 radiative lifetime, quantum yield and the stimulated emission cross-section of the complexes are excellent, which prove that they have promising optical properties for liquid laser. The thermal analyses indicate that they are quite stable to heat.