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)]2H(2)O (Ln(III)=Tb, Dy, Er; hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion) and [Ln(tta)(3)]2H(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)]C6H14 and [Ln(2)(tta)(6)(L)]2CH(2)Cl(2). Irradiation of the ligand at 37040cm(-1) and 29410cm(-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 (6535cm(-1)) and Yb-III (10200cm(-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 (17300-14100cm(-1)). The Eu-III luminescence decay can be nicely fitted by a monoexponential function that allows a lifetime estimation of (0.490.01)ms. Finally, the magnetic and luminescence properties of [Yb-2(hfac)(6)(L)]C6H14 were correlated, which allowed the determination of the crystal field splitting of the F-2(7/2) multiplet state with M-J=+/- 1/2 as ground states.