title: Tuning the triplet energy levels of pyrazolone ligands to match the 5D0 level of europium(III).
abstract: 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.
authors.affiliation: Laboratory of Advanced Materials, Fudan University, Shanghai 200433, PR China.
authors.forename: Mei
authors.initials: M
authors.lastname: Shi
authors.forename: Fuyou
authors.initials: F
authors.lastname: Li
authors.forename: Tao
authors.initials: T
authors.lastname: Yi
authors.forename: Dengqing
authors.initials: D
authors.lastname: Zhang
authors.forename: Huaiming
authors.initials: H
authors.lastname: Hu
authors.forename: Chunhui
authors.initials: C
authors.lastname: Huang
mesh_terms: 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
chemical_list: D008024:Ligands; D047069:Pyrazolones; C038362:pyrazolone; D005063:Europium