Synthesis of novel europium complexes and their photoluminescence properties

Two novel luminescent Eu(Ⅲ) complexes with the formulas (NIP)Eu(DBM)3 1 and (ENIP)Eu(DBM)3 2 (NIP=2-(naphthalen-1-yl)-1H-imidazo [4,5-f] [1,10] phenanthroline,ENIP=1-ethy1-2-(naphthalen-1-yl)-1H-imidazo [4,5-)] [1,10] phenanthroline,DBM=dibenzoylmethanato) were successfully synthesized and characterized by IR and elemental analysis.The UV-vis absorption spectra and photoluminescence properties of the complexes were investigated,and the irradiation at the absorption band between 300-400 nm of europium complexes either in solution or in the solid state led to the emission of a sharp red band at ～610 nm,a characteristic Eu3+ emission due to the transition of5D0→7F2.Furthermore,the weak emission bands around 587 and 595 nm attributed to 5D0→7F0 and 5D0→7F1 transition were also displayed in the emission spectra.These results demonstrated that the Eu(Ⅲ) ion was sensitized efficiently by the ligand and displayed photoluminescence with high intensity,narrow half-peak width,and monochromic light.The excited-state lifetimes of 1 and 2 were in the microsecond time scale,but the photoluminescence quantum yield of 2 (0.03) was two times higher than that of 1 (0.01) which should be attributed to the effect of the ethyl substituting in ENIP.