Complexation behaviour of U(VI) and Eu(III) with Schiff Bases investigated by laserinduced spectroscopy


Complexation behaviour of U(VI) and Eu(III) with Schiff Bases investigated by laserinduced spectroscopy

Lindner, K.; Günther, A.; Bernhard, G.

Actinides and lanthanides play an increasing important role in present time. Actinides can be released into the natural environment especially from mining areas by weathering, erosion and anthropogenic activities as well as by nuclear incidents and thus represents a hazard potential for humans. Lantha-nides occur in nature rarely, but they are significant in the glass and ceramics industries, metallurgy and the cracking of petroleum. New supramolecular complexing agents with N, O, S donor function are developed to separate the metals of the d- and f-block and enriched rare earths. Schiff Bases are essential basic components of these new organic ligands. In this study the complexation of uranium(VI) and europium(III) with the Schiff bases N-benzylideneaniline (NBA), 2-(2-hydroxybenzyliden-amino)phenol (HBAP) and alpha-(4-hydroxyphenyl-imino)-p-cresol (HPIC) was investigated in methanolic solution using time-resolved laserinduced fluorescence spectroscopy (TRLFS) at room and cryogenic temperature and in the case of the uranium(VI)-Schiff bases systems by applying of TRLFS with ultrashort laser pulses (fs-TRLFS).
The measurements of the uranyl luminescence in alcoholic solution at room temperature show strong quenching effects by solvent. These quenching effects could be minimized by measurements at cryogenic temperature (153 K). There is a decrease in fluorescence of the uranium(VI) with the addition of the Schiff Base. A wavelength shift can not be observed, which indicate that the complex seems not to fluoresce.
The europium(III) fluorescence at room temperature is not affected by the methanol. But it turns out that the europium(III) in methanol solution forms an asymmetric complex in comparison to the Eu(III)-water complex. The europium(III) fluorescence decrease with addition of Schiff Base. The observed splitting of the peaks indicates that two different europium(III) species exist in the system.
The fs-TRLFS as a sensitive speciation technique was used to determine the luminescence properties of formed complexes in the uranium(VI)-NBA, uranium(VI)-HBAP and uranium(VI)-HPIC systems. The emission signals show hypsochromic, bathochromic or hypsochromic shifts in comparison to the emission maxima of the uncomplexed ligand. The intensity of the ligand fluorescence increase with the increasing uranium(VI) concentration. The fs-TRLFS investigation opens up the possibilities for the determination of very short-lived complex species via the fluores-cence of the organic compounds by delocalized p-electron systems. Corresponding to the first analyses of the time resolved measurements the luminescence lifetimes of the free ligand and the uranium(VI) complex species are in the range from 2-4 ns. Through the change of the emission properties of organic ligands or metals can be observed the complexation with uranium(VI) and europium(III) and calculated corresponding complex formation constants.

Keywords: fs-TRLFS; Cryo TRLFS; uranium(VI); europium(III); Schiff Bases

  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.11.-07.12.2012, Dresden, Deutschland

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Publ.-Id: 17771