NONRADIATIVE DEACTIVATION OF THE EUROPIUM-5D0 EXCITED-STATE BY WATER-MOLECULES OUTSIDE THE PRIMARY COORDINATION SPHERE OF EU3+ IN NA3[EU(C4H4O5)3].2NACLO4.6H2O

Room-temperature lifetimes of the 5D0 emission of Eu3+ in Na3[Eu(oxydiacetate)3].2NaClO4.6H2O (EuODA.H2O) and Na3[Eu(oxydiacetate)3].2NaClO4.6D2O (EuODA.D2O) are reported. Radiative and non-radiative contributions to the total excited-state relaxation rate are determined for both compounds. It is shown that water molecules outside of the first coordination sphere of Eu3+ make the most significant contribution to the deactivation of 5D0 luminescence in EuODA.H2O. The order-of-magnitude of the deactivation rate is consistent with the predictions of the Forster theory, assuming transfer of electronic energy of the Eu3+ ion to vibrational motions localized on the water molecules. Lattice water does not seem to play an important role in the deactivation of the 5D1 excited state.