Lanthanide complexes involving multichelating TTF-based ligands

S. Speed (1) , M. Feng (1) , G. Fernandez Garcia (2, 1) , Fabrice Pointillart (1) , Bertrand Lefeuvre (1) , F. Riobé (3) , Stéphane Golhen (1) , Boris Le Guennic (1) , F. Totti (2) , Y. Guyot (4) , Olivier Cador (1) , O. Maury (3) , Lahcène Ouahab (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 UniFI - Università degli Studi di Firenze = University of Florence
3 LC - Laboratoire de Chimie - UMR5182
4 ILM - Institut Lumière Matière [Villeurbanne]

The reaction between the 2-_TTF-fused-1H-benzimidazol-2-yl_ pyridine alkylated with either the di-( pyrazol-1-yl)-4-pyridyl (L-1) or dimethyl-2,2'-bipyridine (L-2) moiety and 1 equiv. of L-n(hfac)(3).2H(2)O (Ln(III) = Dy-III and Yb-III) leads to three dinuclear complexes of formula [Yb-2(hfac)(6)(L-1)].2(CH2Cl2).C6H14 (1) and [Ln(2)(hfac)(6)(L-2)].CH2Cl2 (Ln(III) = Yb-III (2) and Dy-III (3)). The X-ray structures highlight square antiprism (D-4d symmetry) and spherical tricapped trigonal prism (D-3h) for the eight-and nine-coordinated lanthanide ions, respectively. Irradiation of the lowest-energy HOMO -> LUMO ILCT absorption band induced a F-2(5/ 2) -> F-2(7/ 2) Yb-centered emission for 1 and 2. Both Yb-III ions displayed similar emissions in 2 while two distinct emissions, attributed to the two YbIII ions because of their different coordination environments, were observed in 1. Slow magnetic relaxation is detected by dynamic magnetic measurements for 3 with a measured relaxation time tau(0) = 3.7(1.3) x 10(-7) s and an energy barrier Delta = 39.6(2) cm(-1). Taking into account the environment of both DyIII ions in 3, it was expected that both metallic centers displayed similar dynamic magnetic behavior. The latter was rationalized by ab initio CASSCF/SI-SO calculations.

Domains: Chemical Sciences

S. Speed, M. Feng, G. Fernandez Garcia, Fabrice Pointillart, Bertrand Lefeuvre, et al.. Lanthanide complexes involving multichelating TTF-based ligands. Inorganic Chemistry Frontiers, 2017, 4 (4), pp.604--617. ⟨10.1039/c6qi00546b⟩. ⟨hal-01532163⟩