Abstract

The formation of hydrated CmF2+ and CmF2+ species in aqueous solutions are studied in the temperature range of 20-90 degrees C at different fluoride concentrations and at constant ionic strength as well as at constant fluoride concentration and different ionic strengths by means of time-resolved laser fluorescence spectroscopy (TRLFS). The molar fractions of the Cm3+ aqua ion, CmF2+, and CmF2+ species are determined by peak deconvolution of the emission spectra. An increase of the mono- and difluoro complexes is observed with increasing fluoride concentration and/or increasing temperature. Using the specific ion interaction theory (SIT), the thermodynamic stability constants log K-1(0)(CmF2+) and log K-2(0) (CmF2+) as well as the values of Delta epsilon(1) and Delta epsilon(2), are determined as a function of temperature. The log K-1(0) values increase from 3.56 +/- 0.07 to 3.98 +/- 0.06 and the log K-2(0) values increase from 2.20 +/- 0.84 to 3.34 +/- 0.21 with increasing temperature from 20 to 90 degrees C. The value of Delta epsilon(1) determined at 25 degrees C is in good agreement with literature data and shows a negligible temperature dependency in the studied temperature range. The value of Delta epsilon(2) also shows only a moderate variation in the studied temperature range. The thermodynamic standard state data (Delta H-r(m)0, Delta S-r(m)0, Delta(r)G(m)(0)) are determined from the temperature dependence of the equilibrium constants at I-m = 0 using the integrated Van't Hoff equation. The fluorescence lifetime of the D-6'(7/2)(Cm3+) state is found to be constant at 63 +/- 5 mu s with increasing fluoride concentration. A model based on density functional theory (DFT) calculations is introduced to account for the additional quenching occurring through the near second sphere waters in the [Cm(H2O)(8)F](2+)(H2O)(18) complex.

Published in

Journal of Physical Chemistry B
2010, Volume: 114, number: 47, pages: 15626-15634
Publisher: AMER CHEMICAL SOC

UKÄ Subject classification

Theoretical Chemistry
Inorganic Chemistry


Publication identifier

DOI: https://doi.org/10.1021/jp107794u

Permanent link to this page (URI)

https://res.slu.se/id/publ/95524