Luminescence and Single-Molecule Magnet Behaviour in Lanthanide Coordination Complexes Involving Benzothiazole-Based Tetrathiafulvalene Ligands

The two ligands 4-[6-(1,3-benzothiazol-2-yl)pyridin-3-yl]-4', 5'-bis(methylthio)tetrathiafulvene (L-1) and 4-[6-(1,3-benzothiazol-2-yl)pyridin-3-yl]-4', 5'-(ethylenedithio)tetrathiafulvene (L-2) were developed, and six new lanthanide coordination complexes, namely, [Ln(2)(hfac)(6)(L-1)(2)]center dot C6H14 center dot xCH(2)Cl(2) [Ln = Dy and x = 0.25 (1); Ln = Yb and x = 0.30 (2); hfac-= 1,1,1,5,5,5-hexafluoroacetylacetonate], [Ln(hfac)(3)(L-2)] [Ln = Dy (3), Yb (4)] and [Ln(tta)(3)(L-1)] [Ln = Yb (5), Er (6); tta(-) = 2-thenoyltrifluoroacetylacetonate], were characterized by single-crystal X-ray diffraction. Compounds 1-6 were identified as mononuclear complexes, and the crystal packing depends on the natures of the ancillary and tetrathiafulvalene-based ligands. The two dysprosium derivatives, 1 and 3, displayed single-molecule-magnet behaviour in zero applied magnetic field. Although the near-infrared luminescence of 2 and 4 is almost undetectable, the change of ancillary ligand switched on the Yb-III (5) and Er-III (6) luminescence.