Luminescent Properties of the Hexakis(Nitrito)Europate(Iii) Ion [Eu(No 2 ) 6 ] 3−
Résumé
The 12-coordinated hexakis(nitrato)europate(III) ion displays a luminescence spectrum compatible with Th, symmetry, with essentially a single emission line at 16 873 cm−1 arising from the 5D0→7F1 transition. At low temperature (4.2 - 170 K), the lifetime of the 5D0 level amounts to 10.9 ms and then sharply decreases because of vibrational de-excitation processes (Ea = 2 250 ± 1 490 cm−1). The forbidden 5D0→7F0 transition displays an extensive pattern of Stokes and anti Stokes vibrational components and its energy reflects a nephelauxetic parameter for the nitrite ions δO(NO2) equal to -14.4, slightly larger than the one associated to the nitrate ion in [Eu(NO3)6]3-. The ligand excitation spectrum contains several bands displaying extensive vibrational structure mostly due to the δ(NO2) vibrational mode.