title: A series of tetrathiafulvalene-based lanthanide complexes displaying either single molecule magnet or luminescence-direct magnetic and photo-physical correlations in the ytterbium analogue.
abstract: The reaction between (4,5-bis(2-pyridyl-N-oxidemethylthio)-4',5')-ethylenedithiotetrathiafulvene (L(1)) or -methyldithiotetrathiafulvene (L(2)) ligands and Ln(hfac)3·nH2O precursors (Ln(III) = Pr, Tb, Dy, Er, and Yb) leads to the formation of seven dinuclear complexes of formula [Ln2(hfac)6(H2O)x(L(y))2] (x = 2 and y = 1 for Ln(III) = Pr (1); x = 0 and y = 1 for Ln(III) = Tb (2), Dy (3), Er (4) and Yb (5); x = 0 and y = 2 for Ln(III) = Tb (6) and Dy (7)). Their X-ray structures reveal that the coordination environment of each Ln(III) center is filled by two N-oxide groups coming from two different ligands L(y). UV-visible absorption properties have been experimentally measured and rationalized by TD-DFT calculations. The temperature dependences of static magnetic measurements have been fitted. The ground state corresponds to the almost pure |M(J) = ±13/2〉 while the first excited state (±0.77|±11/2〉 ± 0.50|±3/2〉 ± 0.39|±5/2〉) is located at 19 cm(-1) and 26.9 cm(-1) respectively for 3 and 7. Upon irradiation at 77 K and at room temperature, in the range 25,000-20,835 cm(-1), both compounds 4 and 5 display a metal-centered luminescence attributed to (4)I(13/2) → (4)I(15/2) (6660 cm(-1)) and (2)F(5/2) → (2)F(7/2) (9972 cm(-1)) transitions, respectively. Emission spectroscopy provides a direct probe of the |±5/2〉 ground state multiplet splitting, which has been confronted to magnetic data. The energy separation of 225 cm(-1) between the ground state and the first excited level (M(J) = ±3/2) fits exactly the second emission line (234 cm(-1)). While no out-phase-signal is detected for 3, the change of ligand L(1) → L(2) induces a change of coordination sphere symmetry around the Dy(III) increasing the energy splitting between the ground and first excited states, and 7 displays a single molecule magnet behavior.
authors: Organométalliques: Matériaux et Catalyse, UMR 6226 CNRS-UR1 Institut des Sciences Chimiques de Rennes, Université de Rennes 1, 35042, Rennes Cedex, France. fabrice.pointillart@univ-rennes1.fr
authors: Fabrice
authors: F
authors: Pointillart
authors: Boris
authors: B
authors: Le Guennic
authors: Thomas
authors: T
authors: Cauchy
authors: Stéphane
authors: S
authors: Golhen
authors: Olivier
authors: O
authors: Cador
authors: Olivier
authors: O
authors: Maury
authors: Lahcène
authors: L
authors: Ouahab
mesh_terms: D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D059346:Magnets / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D055668:Photochemical Processes
chemical_list: D006571:Heterocyclic Compounds; D028581:Lanthanoid Series Elements; D009942:Organometallic Compounds; C063887:tetrathiafulvalene