Dynamics of the excited states of the europium podant, [Eu C36H44N8O5Cl2]Cl•5H2O, in solid state and solutions

Heterocyclic ligands are common sensitizers for lanthanide ion emission under UV irradiation. Due to their specific emission properties, lanthanide podants are promising materials for medical applications. In this report we present spectroscopic and decay-time studies in the 360-77 K temperature range for an Eu(III) podand in the solid state, in solutions, and incorporated into a gel. The compound was synthesized and the luminescence and emission excitation spectra measured for the solid complex and dissolved in H2O, MeOH and MeCN. Two peaks in the spectral region of the D-5(0)-->F-7(0) transition are interpreted in terms of the existence of two forms of the complex in aqueous and MeOH solutions, but only one in MeCN. The role played by the radiative and nonradiative paths in emission intensity are discussed. Dynamic processes in solutions have been considered and are correlated with earlier spectroscopic, and X-ray studies. The pressure and temperature dependence of the D-5(0)-->F-7(0), transition of the Eu(III) complex in water has been measured and thermodynamic parameters (DeltaV, DeltaH) have been determined. (C) 2002 Elsevier Science B V All rights reserved.