Tuning Coordination Environment: Better Photophysical Performance of Europium(III) Complex

The photophysical performance of a europium(III) complex depends on the coordination environment around the Eu 3+ ion. In this work, we employed ethylenediamine to modify this coordination environment by occupying partial binding sites of the central ion before the solvent molecules and found that such parameters of the photophysical performance as lifetime and quantum yield were improved. FTIR spectroscopy, UV–vis absorption, XPS analysis, fluorescence spectroscopy, and fluorescence decay analysis were used to characterize the interactions between ethylenediamine and a Phen–Eu(III) complex, where Phen is 1,10-phenanthroline. The experimental results showed that the complex to which 0.2 mmol of ethylenediamine had been added (C-0.2) exhibited superior photophysical performance and provided a more stable coordination environment around the Eu 3+ ion. The strong emission of the 5 D 0 – 7 F J ( J = 1–4) transition lines of the Eu 3+ ion excited at 274 nm is a result of the efficient emission of the Eu 3+ ion in C-0.2. The estimated nonradiative transition probability of the Eu 3+ ion suggests that ethylenediamine can reduce the nonradiative transition probability of the Eu 3+ ion in the emissive level and improve the emission efficiency.