Complexation of Cm(iii) and Eu(iii) with a hydrophilic 2,6-bis(1,2,4-triazin-3-yl)-pyridine studied by time-resolved laser fluorescence spectroscopy

• Published in: Dalton transactions : an international journal of inorganic chemistry 2012-12, Vol.41 (48), p.14594-1462
• Main Authors: Ruff, Christian M, Müllich, Udo, Geist, Andreas, Panak, Petra J
• Format: Article
• Language: English
• Subjects: Complexation; Enthalpy; Fluorescence; Lasers; Ligands; Liquid-liquid extraction; Selectivity; Spectroscopy
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c2dt31748f

The complexation of Cm( iii ) and Eu( iii ) with 2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine (aq-BTP) is studied in water at pH 3.0 applying time-resolved laser fluorescence spectroscopy. With increasing ligand concentration [M(H 2 O) 9−3 n (aq-BTP) n ] (M = Cm( iii )/Eu( iii ), n = 1, 2, 3) complex species are spectroscopically identified. The conditional stability constants of the M( iii ) 1 : 3 complex species with aq-BTP are log β 03 = 12.2 for Cm( iii ) and log β 03 = 10.2 for Eu( iii ). The complexation reaction is enthalpy- and entropy-driven for both metal ions, while the enthalpy change Δ H 03 is 9.7 kJ mol −1 more negative for Cm( iii ); changes in Δ S 03 are marginal. The difference in Δ G 03 of −12.7 kJ mol −1 between the formation of the [M(aq-BTP) 3 ] complexes agrees with aq-BTP's selectivity in liquid-liquid extraction studies. The complexation of Cm( iii ) and Eu( iii ) with a hydrophilic BTP ligand relevant to the innovative SANEX process was studied for the first time.