On the quenching of trivalent terbium luminescence by ligand low lying triplet state energy and the role of the 7F5 level: The [Tb(tta)3 (H2O)2] case

In this work we discuss the observed Tb3+ ion luminescence quenching, due to the relative ligand low lying triplet state energy, in the [Tb(tta)3 (H2O)2] compound at low and room temperature (tta=thenoyltrifluoroacetonate). Theoretical energy transfer rates, for both multipolar and exchange mechanisms, were calculated and discussed on the basis of selection rules and energy mismatch conditions from the [Tb(tta)3 (H2O)2] emission spectra. We have concluded that the exchange mechanism by far dominates, in the present case, and that the long first excited state 7F5 lifetime (in the millisecond scale) plays a crucial role in the Tb3+ luminescence quenching.