A Novel Approach for the Determination of Stability Constants of Eu(III) and Tb(III) Pyridine-2,6-dicarboxylic Acid Complexes, Using Fluorescence Spectroscopy
- 1 November 1992
- journal article
- spectrometry
- Published by Taylor & Francis in Analytical Letters
- Vol. 25 (11) , 2123-2142
- https://doi.org/10.1080/00032719208020080
Abstract
A new method of evaluation of stability constants of Eu(III) and Tb(III)-pyridine-2,6-dicarboxylic acid (PDA) complexes from the changes of relative fluorescence intensities of “hypersensitive” 5D0 » 7F2 (615 nm) and 5D4 » 7F5 (545 nm) transitions as a function of ligand concentration is proposed. The computed log values : β 1 β 2, β3; 8.83, 15.98 and 21.03 for Eu3+- PDA and 8.09, 16.77, 21.50 for Tb3+- PDA are very reasonable in comparison with the potentiometric data. All values are for pH=5.8 aqueous solutions of complexes for total ionic strength of 0.5 mol.dm−3. An evidence to [Eu(PDA)Eu(H2O)n] 4+ and [Eu2 (PDA)3 (H2O)n]0 neutral complex formation (polynuclear association) is also found in emission of Eu3+-PDA for mol ratios 0.5/1.0 and 1.5/1.0 (moles PDA per mole Eu3+) respectively at 283.6 nm excitation.Keywords
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