Spectroscopy of Eu3+ and Tb3+ pyridine- and pyrazine-2-carboxylates

The luminescence excitation, luminescence and vibrational spectra of europium and terbium pyridine- and pyrazine-2-carboxylates were investigated. A special attention was paid to spectroscopic characterization of tetrakis-compounds, MLn(Lig)4·H2O, where M = NH4, Na; Ln = Eu, Tb; Lig = pyridine-2-carboxylate and pyrazine-2-carboxylate anions. The features of the spectra indicated a decrease of the interaction of carboxylic groups and an increase of the donor–acceptor interaction of coordinated nitrogen atoms with the lanthanide ions in different tetrakis-salts in comparison with the tris-salts. This is accompanied by clear manifestation of the 4f–5d electronic transitions in the excitation spectra of terbium salts.