Figure 1.

This simplified Jablonski diagram for [Eu₂(Lk)(hfac)₆] (k = 2–4) shows the ligand-centered triplet-mediated sensitization mechanism of the two Eu³⁺ ions.^[10] The photophysical processes are described by the rate constants: $k_{\text{r}}^{\text{F}}$ for ligand fluorescence, $k_{\text{nr}}^{\text{F}}$ for ligand internal non-radiative conversion, $k_{\text{r}}^{\text{P}}$ for ligand phosphorescence, $k_{\text{nr}}^{\text{P}}$ for non-radiative relaxation from the ligand triplet state, $k_{\text{r}}^{\text{Eu}}$ for emission of Eu^*, $k_{\text{nr}}^{\text{Eu}}$ for nonradiative decay of Eu^*, k_ISC for ligand intersystem crossing, and $k_{\text{en}.\text{tr}.}^{\text{Eu}}$ for the ligand-to-metal energy transfer. Efficiencies of intersystem crossing (η_ISC), energy transfer ( ${\eta }_{\text{en}.\text{tr}.}^{\text{L}\to \text{Eu}}$), intrinsic quantum yield ( ${\mathrm{\Phi }}_{\text{Eu}}^{\text{Eu}}$), and quantum yield ( ${\mathrm{\Phi }}_{\text{Eu}}^{\text{L}}$) for the global ligand-mediated sensitization of Eu^III in [Eu₂(Lk)(hfac)₆] (solid-state, 293 K).