Effect of TBP on the Coordination Process of Eu(III) with T2EHDGA: A Luminescence Spectroscopy Investigation

Abstract

In this report, we explore the precise responsibility of a phase modifier along with the prime ligand in the coordination process of Ln(III) ions using luminescence spectroscopic technique by taking Eu(III) as the probeing metal ion. A well accepted diglyoclamide (DGA) ligand: N,N,N’,N’‐ tetra(ethylhexyl)diglycolamide(T2EHDGA) was used as the prime extractant along with tri‐n‐butylphosphate (TBP) as the phase modifier. Meticulous investigations on Eu(III) complexation with T2EHDGA‐TBP binary mixture was pursued by employing luminescence spectroscopy with the systematic variation of the concentration of TBP in the ligating phase and initial concentration of Eu(III) in the feed phase. The dominancy of the LMCT band over that of the metal centered band signifies the structural difference in the ligands used in the study. The presence of TBP in the organic phase enhances the intensity of 5D0→7F2 and 5D0→7F0 transition. The excitation and emission patterns of the Eu(III)‐solvate species formed in the organic phase both in unirraditaed and irradiated conditions were found to be entirely different, which effectively corroborates the efficacy of the extracting phase. The asymmetry ratio (AR) and the life time data at each experimental conditions were ascertained to realize the coordination behavior of the Eu(III) complex in the organic phase.

Understanding the correlation between extraction and luminescence behavior of Eu(iii) in a biphasic system in the presence of Co-extracting metal ions

“…These results have been used from our recently published literature for comparison and continuity. 24 Though the essentiality of TBP in the solution of 0.1 M T2EHDGA/ n -DD for high metal loading was corroborated from Fig. 1B, at the same time, it extracts other fission products present in the HLLW solution.…”

“…3, the appearance of a peak due to 5 D 0 -7 F 0 transition in both the spectra is due to jmixing in orbitals, which basically ensues as a result of the crystal field perturbation in the low symmetry complexes, and it occurs only when there are two different ligating species approaching towards Eu(III). 24,25 To know more about Zr(IV) presence, the initial concentration of Zr(IV) in the feed phase was varied from 0 to 0.066 M with a fixed concentration of Eu(III), and the emission spectra were recorded. The intensity of electric dipole transition or hypersensitive transition at 615 nm was observed to be gradually increasing with an increase in Zr(IV) concentration in the feed phase (Fig.…”

“…3B represents the increase in the corresponding AR values (from 1.8 to 2.66 against the initial feed Zr(IV) concentration of 0 to 0.066 M), which corroborates the fact that Zr(IV) acts as a sensitizer to enhance Eu(III) emission intensity. It should be noted that the AR values were evaluated from the intensity ratio (I 615 /I 592 ) of the electric dipole transition to the magnetic dipole transition instead of the area (A 2 /A 1 ) under two peaks, as described 24 These exercises revealed that the solvent extraction results of lanthanides cannot always be correlated with its fluorescence behavior as described elsewhere, and it absolutely depends on the nature of the extractant system and the nature of co-extracting metal ions present along with Ln(III). 26 It has been further clarified with Pd(II)/Eu(III) luminescence results (vide infra).…”

“…In this context, several spectroscopic techniques are used to ascertain the metal coordination behavior and metal-complex status in the extracted phase. [21][22][23][24][25] For instance, the precise role of a couple of phase modifiers such as TBP (tri-n-butylphosphate) and D2EHPA (di-(2-ethylhexyl)phosphoric acid) in the coordination process of Eu(III) with T2EHDGA has been explored by fluorescence spectroscopy. 24,25 The prime aim of these works was to emphasize ligand synergism and metalligand interaction in a binary solvent system.…”

“…[21][22][23][24][25] For instance, the precise role of a couple of phase modifiers such as TBP (tri-n-butylphosphate) and D2EHPA (di-(2-ethylhexyl)phosphoric acid) in the coordination process of Eu(III) with T2EHDGA has been explored by fluorescence spectroscopy. 24,25 The prime aim of these works was to emphasize ligand synergism and metalligand interaction in a binary solvent system. The technique potentially offers an elemental understanding of the metal-ligand complex formation process, and the solvent extraction behavior of a target metal ion can very well be addressed by varying different experimental parameters to evaluate the nature of the metalsolvate species formed in the organic phase under irradiated and unirradiated conditions.…”