Luminescence and Single-Molecule Magnet Behavior in Lanthanide Complexes Involving a Tetrathiafulvalene-Fused Dipyridophenazine Ligand

• Published in: Inorganic chemistry 2015-06, Vol.54 (11), p.5384-5397
• Main Authors: Pointillart, Fabrice, Jung, Julie, Berraud-Pache, Romain, Le Guennic, Boris, Dorcet, Vincent, Golhen, Stéphane, Cador, Olivier, Maury, Olivier, Guyot, Yannick, Decurtins, Silvio, Liu, Shi-Xia, Ouahab, Lahcène
• Format: Article
• Language: English
• Subjects: Chemical Sciences
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.5b00441

The reaction between the TTF-fused dipyrido­[3,2-a:2′,3′-c]­phenazine (dppz) ligand (L) and 1 equiv of Ln­(hfac)3·2H2O (hfac– = 1,1,1,5,5,5-hexafluoroacetyacetonate) or 1 equiv of Ln­(tta)3·2H2O (tta– = 2-thenoyltrifluoroacetonate) (LnIII = DyIII or YbIII) metallic precursors leads to four mononuclear complexes of formula [Ln­(hfac)3(L)]·C6H14 (LnIII = DyIII (1), YbIII (2)) and [Ln­(tta)3(L)]·C6H14 (LnIII = DyIII (3), YbIII (4)), respectively. Their X-ray structures reveal that the LnIII ion is coordinated to the bischelating nitrogenated coordination site and adopts a D 4d coordination environment. The dynamic magnetic measurements show a slow relaxation of the DyIII magnetization for 1 and 3 with parameters highlighting a slower relaxation for 3 than for 1 (τ0 = 4.14(±1.36) × 10–6 and 1.32(±0.07) × 10–6 s with Δ = 39(±3) and 63.7(±0.7) K). This behavior as well as the orientation of the associated magnetic anisotropy axes have been rationalized on the basis of both crystal field splitting parameters and ab initio SA-CASSCF/RASSI-SO calculations. Irradiation of the lowest-energy HOMO → LUMO ILCT absorption band induces a 2F5/2 → 2F7/2 Yb-centered emission for 2 and 4. For these YbIII compounds, Stevens operators method has been used to fit the thermal variation of the magnetic susceptibilities, and the resulting M J splittings have been correlated with the emission lines.