Europium(III) Coordination in a Combined Ligand System: A Luminescence Spectroscopy Study

The coordination of europium(III) in a combined ligand system has been probed by luminescence spectroscopy by extracting it from nitric acid medium. The ligands used in the study are N,N,N ',N '-tetra-bis(2-ethylhexyl)diglycolamide (T2EHDGA) and bis(2-ethylhexyl)phosphoric acid (D2EHPA). Europium(III) complex with these ligands present in n-Dodecane (n-DD) medium and its detailed investigation by luminescence spectroscopy is emphasized in this paper. Various experimental parameters such as aqueous phase acidity, concentration of ligand and initial metal ion, radiation dose, etc. were tuned to find the luminescence behavior of Eu(III) in the extracted phase. The emission intensity of Eu(III) was extremely high in the organic phase after extraction at all nitric acid phases (0.5 M to 3 M HNO3) for T2EHDGA/n-DD and from 0.01 M to 1 M for D2EHPA/n-DD) as compared to that of the aqueous phase. The principal driving force for the complexation mechanism of Eu(III) at each nitric acid was ascertained by varying the concentration of D2EHPA in the solution of 0.1 M T2EHDGA/n-DD. The decay profile of the Eu(III) complex was remarkably high (>1.2 millisecond (ms)) indicating theformation of inner-sphere complex of Eu(III) with the ligands. The emission profile of Eu(III) was recorded in the irradiated solvent compositions and was compared with respect to unirradiated condition.