Pressure and Temperature Dependence of the < sup> 7 F < inf> 0 → < sup> 5 D < inf> 0 Excitation Spectrum of Europium(III) as a Probe of the Thermodynamics and Solution Structure of Complexes of Europium(III) with Polyaminocarboxylate Ligands

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The pressure and temperature dependence of the nondegenerate 7F0 → 5D0 excitation spectra of aqueous complexes of Eu(III) with the polyaminocarboxylate ligands triethylenetetraaminehexaacetic acid (ttha) and diethylenetriaminepentaacetic acid (dtpa) have been measured and analyzed in order to probe the solution structure and thermodynamics of these species. The 1:1 metal to ligand complexes of Eu(III) with dtpa show evidence for only one coordination environment for the range of temperatures (5-80 °C) and pressures (1 bar-3 kbar) studied in this work, whereas 1:1 solutions of Eu(III) with dtpa show spectral changes as a function of temperature and pressure which have been interpreted in terms of dimer and monomer structures with different coordination environments. Comparison is made to previous crystallographic results. © 2001 American Chemical Society.

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Journal of Physical Chemistry A