Tb3+ Photophysics: Mapping Excited State Dynamics of [Tb(H2O)9]3+ Using Molecular Photophysics.

Abstract

The study of optical transitions in lanthanide(III) ions has evolved separately from molecular photophysics, but the framework still applies to these forbidden transitions. In this study, a detailed photophysical characterization of the [Tb(H2O)9]3+ aqua ion was performed. The luminescence quantum yield (Φlum), excited state lifetime (τobs), radiative (kr ≡ A) and nonradiative (knr) rate constants, and oscillator strength (f) were determined for Tb(CF3SO3)3 in H2O/D2O mixtures in order to map the radiative and nonradiative transition probabilities. It was shown that the intense luminescence observed from Tb3+ compared to other Ln3+ ions is not due to a higher transition probability of emission but rather due to a lack of quenching, quantified by quenching to O-H oscillators in the aqua ion of kq(OH) = 2090 s-1 for terbium and kq(OH) = 8840 s-1 for europium. In addition, the Horrocks method of determining inner-sphere solvent molecules has been revisited, and it was concluded that the Tb3+ is 9-coordinated in aqueous solution.