Stability Constants of Scandium Complexes. II. Dicarboxylate Complexes Species

Abstract

The stability constants of scandium complexes with malonate, maleate, itaconate, glutarate, adipate, and succinate ligands were determined titrimetrically at 25.0 °C and at an ionic strength of 0.1. The chelate effect was negligible for the stability of the scandium complexes with the dicarboxylate ligands studied in contrast with the lanthanoid complexes. The complex formation of scandium might be explained by an electrostatic ionic bond similar to ones exhibited in the lighter rare-earth complexes, due to linear relationships between the stability constants and the ionic potential Z2⁄r.

Influence of adipic acid on the speciation of Eu(III): Review of thermodynamic data in NaCl and NaClO4 media, and a new determination of Eu-adipate complexation constant in 0.5 mol·kgw−1 NaClO4 medium by time-resolved luminescence spectroscopy

“…ε(H + , ClO 4 − ) 0.14 ± 0.02 [24] ε(H + , Cl − ) 0.12 ± 0.01 [24] ε(Na + , OH − ) 0.04 ± 0.01 [24] ε(Na + , CO 3 2− ) -0.08 ± 0.03 [24] ε(Adip 2− , Na + ) 0.215 ± 0.006 estimated here from [25][26][27][28][29] in NaClO4 and [30,33] in NaCl ε(AdipH − , Na + ) 0.135 ± 0.006 estimated here from [25][26][27][28][29] in NaClO4 and [30,33] in NaCl ε(AdipH 2 (aq), NaClO 4 ) 0.037 ± 0.009 estimated here from [25][26][27][28][29] in NaClO4 and [30,33]…”

“…Solubility of AdipH2(s) was also proposed [33] in NaCl ionic medium. We have decided to reinterpret available data in NaClO4 [25][26][27][28][29] and NaCl [30,33] from literature at 25°C to propose coherent data to be used in the framework of SIT [10,24].…”

“…Up to now no specific ion interaction coefficients are available in the open literature for adipic acid protonation constants and Eu(III) complexation constants within the SIT formalism [24] and Hummel et al [10]. Data on adipic acid deprotonation constant in NaClO4 [25][26][27][28][29] or NaCl [30,31] ionic media are existing. Thermodynamic functions of reaction for Kn [32] and formation for adipic acid [31] has been proposed.…”