Influence of aromatics and substituents on the time-resolved luminescence spectroscopy of Eu(III)-complexes
Résumé
Simple organic carboxylic ligands have since long been proposed as analogues of the metallic cations complexation processes of complex organic mixtures, e.g. natural organic matter (NOM). There are quite substantial amounts of spectroscopic evidence that are showing that this approximation is not totally verified experimentally. The main evidence is the widespread occurrence of the luminescence bi-exponential decay of the NOM-complexed lanthanides (Ln) and actinides (An) at their +III redox state [1-3].Even if numerous complexation constants of Ln(III)- and An(III)-carboxylate complexes were determined spectroscopically in time-resolved luminescence spectroscopy [4], a global view on the influence of the different types of organic acids is still lacking, especially for aromatic acids. Some data are available [5-7], but no clear evolution of both the luminescence spectra and decay times have been proposed.I here propose to compare the luminescence comportment of Eu(III) complexed by a series of organic carboxylic acids, namely acetic, benzoic, phthalic, para-hydroxybenzoic, and 3,4-dihydroxybenzoic acid. The luminescence spectrum will be compared as well as their relative luminescence decay (Fig.1). The influence of the different substituents will be evidenced