A spectroscopic study of Cm(iii) complexation with propionate in saline solutions at variable temperatures

• Published in: New journal of chemistry 2013-01, Vol.37 (5), p.152-1528
• Main Authors: Fröhlich, Daniel R, Skerencak-Frech, Andrej, Morkos, Marie-Louise K, Panak, Petra J
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c3nj00109a

The complexation of Cm( iii ) with propionate is studied by time resolved laser fluorescence spectroscopy (TRLFS) in saline solutions (NaCl and CaCl 2 ) as a function of ionic strength, ligand concentration, and temperature. The molar fractions of the different Cm( iii ) species are determined by peak deconvolution of the measured fluorescence spectra. By using the specific ion interaction theory (SIT), the stability constants at zero ionic strength (log K 0 n ) of the first and second complexation steps are determined. The stability constants of the mono- and dipropionate complexes increase continuously with increasing temperature between 20-90 °C in both background electrolytes. The log K 0 n values are linearly correlated to the reciprocal temperature, indicating Δ r H 0 m = const. and Δ r C 0 p,m = 0. Therefore, the thermodynamic constants (Δ r H 0 m , Δ r S 0 m , Δ r G 0 m ) for the formation of the [Cm(Prop)] 2+ and [Cm(Prop) 2 ] + complexes are derived from the integrated van't Hoff equation. The results show that both reactions are entropy driven. Furthermore, neither the formation of ternary species including Ca 2+ nor a complexing effect of Cl − at elevated temperatures is observed under the chosen experimental conditions. Lastly, the ion-ion interaction coefficients of both complexed species with Cl − are derived for the first time. The complexation of Cm( iii ) with propionate is studied by time resolved laser fluorescence spectroscopy (TRLFS) in saline solutions (NaCl and CaCl 2 ) as a function of ionic strength, ligand concentration, and temperature.