| Abstract
| - Compared to the homogeneous ligand with an alkyl group at the 4-position of the pyrazolone ring, three synthesized pyrazolone-based ligands with electron-poor or electron-rich aryl substituents exhibit lower triplet energy levels which match the 5D0 level of Eu3+ properly. Their corresponding europium complexes emit characteristic Eu(III) photoluminescence with at most 9.2 × 10-3 fluorescent quantum yield, 35.1% energy transfer efficiency, and 2.6% europium emission probability.
- 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), weresynthesized 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 characterizedby photophysical studies. The characteristic Eu(III) emission of these complexes with at most 9.2 × 10-3 of fluorescentquantum yield was observed at room temperature. The results show that the modification of ligands tunes thetriplet energy levels of three pyrazolone-based ligands to match the 5D0 energy level of Eu3+ properly and improvesthe energy transfer efficiency from antenna to Eu3+, therefore enhancing the Eu(III) emission intensity. The highestenergy 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 ofligands. Furthermore, the electroluminescent properties of Eu(L1)3(TPPO)(H2O) were also investigated.
|
