Pressure and temperature dependence of the F-7(0) -> D-5(0) excitation spectrum of europium(III) as a probe of the thermodynamics and solation structure of complexes of europium(III) with polyaminocarboxylate ligands

The pressure and temperature dependence of the nondegenerate F-7(0) - D-5(0 ) excitation spectra of aqueous complexes of Eu(LII) with the polyaminocarb oxylate ligands triethylenetetraaminehexaacetic acid (ttha) and diethylenet riaminepentaacatic acid (dtpa) have been measured and analyzed in order to probe the solution structure and thermodynamics of these species. The 1:1 m etal to ligand complexes of Eu(III) with dtpa show evidence for only one co ordination environment for the range of temperatures (5-80 degreesC) and pr essures (1 bar-3 kbar) studied in this work, whereas 1:1 solutions of Eu(m) with dtpa show spectral changes as a function of temperature and pressure which have been interpreted in terms of dimer and monomer structures With d ifferent coordination environments. Comparison is made to previous crystall ographic results.