Evidence of Different Stoichiometries for the Limiting Carbonate Complexes across the Lanthanide(III) Series

Lanthanide Carbonates

“…The thermodynamic stability constants that were obtained from the extraction and potentiometry methods and, particularly, from the solubility studies of Na[Ln(CO 3 3-seems to be the limiting complex. [5,8,9] We decided to investigate the speciation of the carbonates by taking advantage of the analysis of the f-f transitions, which has previously been successfully applied to identify the structure and stoichiometry of various complexes in aqueous solution. [23] The analysis of the UV/Vis/NIR absorption spectra led to certain conclusions about the stoichiometry of the complexes and the coordination modes of the carbonate anions.…”

“…It is well known that the presence of H 2 O in the lanthanide first coordination sphere contributes to nonradiative deexcitation of luminescence and, as a consequence, reduces the quantum yield of the lanthanide luminescence. In order to determine if polynuclear complexes are formed in considerable amount, the Stern-Volmer K SV quenching constants, which are defined by Equations (8) and (9): (8) (9) were determined. K SV Φ and K SV τ are the Stern-Volmer quenching constants that were determined from the luminescence intensity (I) or the luminescence lifetime (τ), and I Tb , I Tb,Eu , I Eu , τ Tb , τ Tb,Eu , τ Tb are the appropriate luminescence quantities in the presence or absence of the quencher (Eu 3+ ).…”

“…On the other hand, the measurements of the electrophoretic mobilities and solubilities of Na[Eu(CO 3 ) 2 ]·nH 2 O, which was performed by Philippini et al, [8,9] indicated different complex stoichiometries for the light ([Ln(CO 3 ) 4 ] 5-) and heavy ([Ln(CO 3 ) 3 ] 3-) lanthanides. These differences were explained by the lanthanide contraction.…”

“…These differences were explained by the lanthanide contraction. Vercouter et al, [5,9] by taking into account the results from the solubility and time-resolved laser-induced fluorescence spectroscopy (TRLFS) studies, concluded that the 8-coordinate [Eu(CO 3 ) 3 …”

Precipitation of and compounds from aqueous solutions for and

“…This contraction has also been proposed to explain the higher stabilities of Ln 2 ðCO 3 Þ 3 for the heaviest lanthanides compared to the lightest ones [1]. In the present study, we try to precipitate a set of ALnðCO 3 Þ 2 ; xH 2 O compounds from concentrated A 2 CO 3 aqueous solutions at room temperature in order to carry out the solubility measurements presented elsewhere [3,48]. Thus, well crystallised compounds are not especially expected.…”