Tb 3+ Photophysics: Mapping Excited State Dynamics of [Tb(H 2 O) 9 ] 3+ Using Molecular Photophysics.

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(H 2 O) 9 ] 3+ aqua ion was performed. The luminescence quantum yield (Φ lum ), excited state lifetime (τ obs ), radiative ( k r ≡ A ) and nonradiative ( k nr ) rate constants, and oscillator strength ( f ) were determined for Tb(CF 3 SO 3 ) 3 in H 2 O/D 2 O mixtures in order to map the radiative and nonradiative transition probabilities. It was shown that the intense luminescence observed from Tb 3+ compared to other Ln 3+ 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 k q (OH) = 2090 s -1 for terbium and k q (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 Tb 3+ is 9-coordinated in aqueous solution.