Luminescence Spectroscopic Study of europium(III) with alpha-hydroxy isobutyric acid in 1,4-dioxane
EMSL Project ID
37495
Abstract
It has been previously demonstrated that the ligand, alpha-hydroxy isobutyric acid (HIBA) shows remarkably efficient separations of trivalent lanthanides when compared to other carboxylic acids. While HIBA-lanthanide complexes have been studied extensively in aqueous media, little has been done to determine the thermodynamic values of HIB-lanthanide complexation in aqueous/organic systems. The main purpose of this research is to elucidate why certain arrangements of ligand donor atoms work more efficiently for trans-lanthanide separations and more globally to gain a better understanding of the role of solvation effects in metal-ligand bonding. The basic hypothesis of this work is that the nature of the solvent plays an important role in determining the size selectivity in this system. The luminescence lifetimes of aqueous Eu3+ can be used to determine the number of water molecules coordinated to the inner sphere of Ln3+ ions bound in complexes with the equation[3]q=A[1/(excited state)H2O -1/(excited state)D2O- alpha+ 0.45n OH + 0.99n NH + 0.075n O=CNH]
The Eu3+ can be excited to the lowest state (5Do) by a pulsed laser at 579 nm; the subsequent emission (5Do -> 7F2) at 616 nm monitored. In this work, time-resolved laser-induced fluorescence measurements will be made in H2O and D2O solution of 1.0x10-4 M Eu 3+ with varying concentrations of HIBA to feature the 1:1, 1:2, and 1:3 Eu(HIB)x buffered at the pH where complexation occurs in 0.1 M NaClO4 [4] . These experiments will be performed in a various dioxane/water media ranging from 0% to 50% dioxane and at different temperatures (15, 25 and 35 oC). These experiments should elucidate whether dioxane is incorporated into the primary coordination sphere along with HIBA upon complexation. Lifetimes should be expected to increase if 1,4-dioxane replaces H2O in the inner coordination sphere of the metal ion and its complexes. Ultimately this information will be coordinated with thermodynamic data determined separately in the same media. Europium-HIBA stability constants have been previously determined potentiometrically at Washington State University in 10 and 30% dioxane. Appropriate facilities for laser-induced fluorescence are not available at WSU.
Project Details
Project type
Exploratory Research
Start Date
2010-01-11
End Date
2011-01-16
Status
Closed
Released Data Link
Team
Principal Investigator