Tuning the triplet energy levels of pyrazolone ligands to match the 5D0 level of europium(III).
Three pyrazolone-based ligands, namely 1-phenyl-3-methyl-4-(1-naphthoyl)-5-pyrazolone (HL1), 1-phenyl-3-methyl-4-(4-dimethylaminobenzoyl)-5-pyrazolone (HL2), and 1-phenyl-3-methyl-4-(4-cyanobenzoyl)-5-pyrazolone (HL3), were synthesized by introducing electron-poor or electron-rich aryl substituents at the 4-position of the pyrazolone ring. Their corresponding europium complexes Eu(LX)3(H2O)2 and Eu(LX)3(TPPO)(H2O) (X = 1-3) were characterized by photophysical studies. The characteristic Eu(III) emission of these complexes with at most 9.2 x 10(-3) of fluorescent quantum yield was observed at room temperature. The results show that the modification of ligands tunes the triplet energy levels of three pyrazolone-based ligands to match the 5D0 energy level of Eu3+ properly and improves the energy transfer efficiency from antenna to Eu3+, therefore enhancing the Eu(III) emission intensity. The highest energy transfer efficiency and probability of lanthanide emission of Eu(L1)3(H2O)2 are 35.1% and 2.6%, respectively, which opens up broad prospects for improving luminescent properties of Eu(III) complexes by the modification of ligands. Furthermore, the electroluminescent properties of Eu(L1)3(TPPO)(H2O) were also investigated.
Shi
Mei
M
Laboratory of Advanced Materials, Fudan University, Shanghai 200433, PR China.
Li
Fuyou
F
Yi
Tao
T
Zhang
Dengqing
D
Hu
Huaiming
H
Huang
Chunhui
C
D015392:Chemistry, Inorganic / Q000379:methods*; D018360:Crystallography, X-Ray; D004583:Electrons; D005063:Europium / Q000737:chemistry*; D008024:Ligands; D049449:Luminescence; D015394:Molecular Structure; D010777:Photochemistry / Q000379:methods; D047069:Pyrazolones / Q000138:chemical synthesis / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D008024:Ligands; D047069:Pyrazolones; C038362:pyrazolone; D005063:Europium