Understanding the complexation of the Eu3+ ion with TODGA, CMPO, TOPO and DMDBTDMA: Extraction, luminescence and theoretical investigation

• DOI: 10.1016/j.poly.2016.06.037
• Publication Date: 2016-07-03T13:46:15Z
• Authors: Arijit Sengupta; Sk. Musharaf Ali; K.T. Shenoy
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract A comparative study was carried out to understand the complexation behavior of the Eu 3+ ion with important reagents, namely TODGA (N,N,N′,N′ tetraoctyl diglycolamide), CMPO (octyl (phenyl)-N, N-diisobutyl carbamoyl methyl phosphine oxide), DMDBTDMA (dimethyl dibutyl tetradecyl malonamide) and TOPO (tri-n-octyl phosphine oxide) in dodecane, used for the separation of actinides and lanthanides from lab and nuclear high-level wastes, by experimental (extraction and luminescent) and theoretical means. A solvent extraction study revealed the metal–ligand stoichiometry as 1:3 for all the systems with the extraction efficiency TOPO > CMPO > TODGA > DMDBTDMA at 1 M HNO 3 , while TODGA > CMPO > DMDBTDMA > TOPO at 3 M HNO 3 . A luminescence investigation revealed the presence of single species in the extracted complex for all the systems, with no inner sphere water molecules for all the systems except for DMDBTDMA which had one inner sphere water molecule. The high intensity of the 5 D 0 – 7 F 2 transition revealed the presence of Eu 3+ ions in an asymmetric environment with the local point group symmetry C 3v for the TODGA and DMDBTDMA complexes, compared to C 3h symmetry for the CMPO and TOPO complexes. Judd–Offelt parameters, radiative, non-radiative lifetimes, branching ratio, transition probabilities and quantum efficiencies for all the complexes were estimated and compared. Three O-donor atoms from each TODGA molecule coordinated to the Eu 3+ ion in the first coordination sphere, while three CMPO units were found to be coordinated in a monodentate fashion. For the Eu-TOPO complex, three O donor atoms from each of the three TOPO molecules and six O donor atoms from three nitrate ions were coordinated. Out of three DMDBTDMA ligands, one was found to be coordinated in a bidentate mode, whereas two were in a monodentate mode, along with three nitrate ligands bonding in a monodentate fashion.