Photochemistry Group, Faculty of Chemistry and Pharmacy, Sofia University, 1 J. Bourchier Blvd, 1164 Sofia, Bulgaria; John Atanasoff Center for Bio and Nano Photonics (JAC BNP), 1164 Sofia, Bulgaria.
Department of Physics, Sofia University, 5 J. Bourchier Blvd., 1164 Sofia, Bulgaria.
Spectrochim Acta A Mol Biomol Spectrosc. 2021 Sep 5;258:119832. doi: 10.1016/j.saa.2021.119832. Epub 2021 Apr 20.
The effect of luminescent enhancement under exchange of the auxiliary ligand in Europium(III) tris(1,3-diphenyl-1,3-propanedionato) monohydrate was investigated by steady-state and time-resolved transient absorption spectroscopy. The excited state relaxation dynamics of this complex was analysed through a comparison of the experimental data obtained for several model compounds, namely Eu(DBM)·NH, Eu(DBM).EDA, Eu(DBM).Phen, Al(DBM) and dibenzoylmethane (DBM) in various solutions and polymer matrices. The results show there is no linear relationship between enhancement of the emission quantum yield and the luminescent lifetime, which suggests that the auxiliary ligand reduces the rate of nonradiative relaxation of the lanthanide ion, but also affects the excited state energy transfer from ligand to metal ion. Transient absorption data shows a clear correlation between the efficiency of the energy transfer and the degree of triplet state population expressed by an amplification of the signal for its excited state absorption band on going from Eu(DBM)·HO to the Eu(DBM) = .L complex. The results show that this auxiliary ligand exchange acts as a "switch" turning the intersystem crossing on or off as a competitive pathway for excited state relaxation of the europium(III) complexes.
通过稳态和时间分辨瞬态吸收光谱研究了辅助配体交换对三（1,3-二苯基-1,3-丙二酮）合铕（III）一水合物中镧系元素（III）发光增强的影响。通过比较几种模型化合物（即 Eu(DBM)·NH、Eu(DBM).EDA、Eu(DBM).Phen、Al(DBM)和二苯甲酰甲烷（DBM）在不同溶液和聚合物基质中的实验数据，分析了该配合物的激发态弛豫动力学。结果表明，发射量子产率的增强与发光寿命之间没有线性关系，这表明辅助配体降低了镧系离子非辐射弛豫的速率，但也影响了配体向金属离子的激发态能量转移。瞬态吸收数据表明，能量转移效率与三重态种群的程度之间存在明显的相关性，这表现在从 Eu(DBM)·HO 到 Eu(DBM) = L 配合物，其激发态吸收带的信号增强。结果表明，这种辅助配体交换充当“开关”，作为铕（III）配合物激发态弛豫的竞争途径，打开或关闭系间穿越。
