Europium(III) Interaction with a Polyaza-Aromatic Extractant Studied by Time-Resolved Laser-Induced Luminescence:  A Thermodynamical Approach

Abstract

The 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridines (DATPs) belong to a new family of extracting agents recently developed in the framework of nuclear fuel reprocessing. These molecules exhibit exceptional properties to separate actinides(III) from lanthanides(III) in nitric acid solutions. In a previous work, the use of electrospray ionization mass spectrometry (ESI-MS) provided data such as stoichiometries and conditional stability constants of various DATP complexes with europium and evidenced the unusual capability of DiPTP [bis(di-iso-propyltriazinyl)pyridine] ligand to form 1:3 complexes in nitric acid solution. This latter result has then been further investigated by considering DiPTP complexation features with the complete lanthanide family. Moreover, a complementary study of equilibria in solution with a non intrusive technique such as time-resolved laser-induced luminescence (TRLIL) seemed quite promising to determine thermochemical data such as enthalpy and entropy variations associated with the complexation reaction between Eu(III) and DiPTP. Furthermore, this TRLIL study may also allow ensuring that the observations made on mass spectra actually reflected the equilibrium in solution and not an intermediate state between liquid phase and gaseous phase. The investigation of europium(III) complexation with DiPTP by TRLIL described in this paper first led to highlight the exclusive formation of a 1:3 complex between europium(III) and the DiPTP ligand, specificity already pointed out by ESI-MS. Two different calculation methods, using either luminescence spectra and luminescence decay curves, have then been used to measure the conditional stability constant of the [Eu(DiPTP)(3)](3+) complex. Both methods gave similar results (log beta3(app)= 14.3 +/- 0.6 at pH 2.8) in good agreement with the one previously reported in ESI-MS studies (log beta3(app)= 14.0 +/- 0.6 at pH 2.8). Moreover, while considering the influence of temperature on the value of the stability constant, it was possible to estimate the enthalpy (DeltaH(beta3) = -29 +/- 3 kJ mol(-1) at pH 2.8) and entropy variations (DeltaS(beta3) = 173 +/- 10 J K(-1) mol(-1) at pH 2.8) associated with the [Eu(DiPTP)(3)](3+) complex formation.

6-(Tetrazol-5-yl)-2,2′-bipyridine: A Highly Selective Ligand for the Separation of Lanthanides(III) and Actinides(III)

“…6-Cyano-2,2′-bipyridine 30 13,14 Et-BDP, 16 and n Pr-Tetrazine. 16 Fourier map calculations, as well as the magnitude of the residual electron densities, in each case were of no chemical significance.…”

A TRLFS Study on the Complexation of CmIII and EuIII with 2,6‐Bis(5,6‐dipropyl‐1,2,4‐triazin‐3‐yl)pyridine in Water/Methanol Mixture

“…[15][16][17] To confirm the formation of a metal ion:ligand 1:3 species upon addition of nPr-BTP to the solvated metal ions ([M(solv.)] 3+ ), slope analysis of the obtained titration results is performed using the following Equation (1): (1) It follows Equation (2): (2) According to this, a linear correlation between the logarithm of the concentration ratio…”

Influence of the solvent on the complexation of Cm(iii) and Eu(iii) with nPr–BTP studied by time-resolved laser fluorescence spectroscopy

“…[24][25][26] Information on the number and type of ligands as well as information on the complex geometry are provided by spectroscopic parameters like the position, shape and intensity of the emission bands. TRLFS has already been successfully used to study the coordination chemistry of Cm(III) and Eu (III) with BTP-and BTBP-type ligands in aqueous [14][15][16]27 and organic solutions. 28,29 Experimental section Chemicals All solvents were purchased by Merck KGaA and were used as supplied (UVASOL quality).…”