Unprecedented Sensitization of Visible and Near‐Infrared Lanthanide Luminescence by Using a Tetrathiafulvalene‐Based Chromophore

Ligand L was synthesized and then coordinated to [Ln(hfac) 3 ] ⋅ 2 H 2 O (Ln III =Tb, Dy, Er; hfac − =1,1,1,5,5,5‐hexafluoroacetylacetonate anion) and [Ln(tta) 3 ]⋅2 H 2 O (Ln III =Eu, Gd, Tb, Dy, Er, Yb; tta − =2‐thenoyltrifluoroacetonate) to give two families of dinuclear complexes [Ln 2 (hfac) 6 ( L )] ⋅ C 6 H 14 and [Ln 2 (tta) 6 ( L )] ⋅ 2 CH 2 Cl 2 . Irradiation of the ligand at 37 040 cm −1 and 29 410 cm −1 leads to tetrathiafulvalene‐centered and 2,6‐di(pyrazol‐1‐yl)‐4‐pyridine‐centered fluorescence, respectively. The ligand acts as an organic chromophore for the sensitization of the infrared Er III (6535 cm −1 ) and Yb III (10 200 cm −1 ) luminescence. The energies of the singlet and triplet states of L are high enough to guarantee an efficient sensitization of the visible Eu III luminescence (17 300–14 100 cm −1 ). The Eu III luminescence decay can be nicely fitted by a monoexponential function that allows a lifetime estimation of (0.49±0.01) ms. Finally, the magnetic and luminescence properties of [Yb 2 (hfac) 6 ( L )] ⋅ C 6 H 14 were correlated, which allowed the determination of the crystal field splitting of the 2 F 7/2 multiplet state with M J =±1/2 as ground states.